October 2003 Gasification Archive

From tmiles at TRMILES.COM Thu Oct 2 20:14:33 2003
From: tmiles at TRMILES.COM (Tom Miles)
Date: Tue Aug 10 18:24:30 2004
Subject: Fw: Biomass RFP for 20 year PPA with We-Energies
Message-ID: <THU.2.OCT.2003.171433.0700.TMILES@TRMILES.COM>

FW: Biomass RFP for 20 year PPA with We-Energies-----Original Message-----
From: OConor.Richard
Sent: Wednesday, October 01, 2003 9:03 PM
Subject: Biomass RFP for 20 year PPA with We-Energies

MILWAUKEE - We Energies has issued a request for proposals (RFP) for up to
25 megawatts of electricity from "biomass" technologies. Biomass
technologies include organic materials such as agricultural manure, food
processing waste, bio-waste, brewery residues, organic sludge, and crops
grown specifically for energy production purposes.
"We believe that biomass is a promising renewable resource that can provide
electricity for our customers. Biomass is a way to generate electricity
using Wisconsin-based resources. This is good home grown electricity," said
Patrick Keily, renewable energy project manager for We Energies.
Through this RFP, We Energies is encouraging developers, farm operators, and
other businesses to propose projects that could result in a contract to sell
electricity to We Energies from biomass generating sources beginning as
early as next year. Contracts resulting from these proposals will be for a
term of up to 20 years. Proposals received by November 26, 2003, will be
evaluated for a short list of qualified projects selected for in-depth
evaluation.
We Energies prefers proposals for biomass-generated electricity using
anaerobic digestion. However, projects using municipal sludge, paper mill
sludge, and agricultural animal waste, and using direct-fired, co-fired, or
gasified processes will be considered. According to Keily, the company also
is interested in encouraging the development of new biomass generation
technologies and resources. "We will strongly consider new and innovative
methods of biomass generation in the review of the proposed projects," he
said.
We Energies has set an aggressive target of at least five percent of its
retail electric energy sales to come from renewable energy sources by 2011.
Biomass energy development will play a significant role in helping the
company reach its target, and comes on the heals of the company's recent
announcement of 20-year power purchase agreements with two developers for
the entire electricity output of three wind farms planned to be built in
Wisconsin over the next two years.
Additional information related to this RFP can be found at
http://www.we-energies.com/biomass_RFP.htm
We Energies serves more than one million electric customers in Wisconsin and
Michigan's Upper Peninsula and more than 980,000 natural gas customers in
Wisconsin. We Energies is the trade name of Wisconsin Electric Power Company
and Wisconsin Gas Company, the principal utility subsidiaries of Wisconsin
Energy Corporation (NYSE: WEC). Visit the We Energies Web site at
www.we-energies.com. Learn more about Wisconsin Energy Corporation by
visiting www.WisconsinEnergy.com.

From krishnakumar_07 at YAHOO.CO.UK Wed Oct 8 16:01:04 2003
From: krishnakumar_07 at YAHOO.CO.UK (=?iso-8859-1?q?krishna=20kumar?=)
Date: Tue Aug 10 18:24:30 2004
Subject: information on rice husk gasifier
In-Reply-To: <4.3.1.2.20030925170503.01cfce10@mail.ilstu.edu>
Message-ID: <WED.8.OCT.2003.210104.0100.KRISHNAKUMAR07@YAHOO.CO.UK>

Sir,

Can u provide some light on the following w.r.t Rice
Husk throatless downdraft Gasification

1. Gas to Rice Husk ratio ( nm3 / kg of husk )

2. Hot Gas & Cold Gas efficiencies

3. Graph for correlating H2, CH4 & N2 from CO & Co2
concentration

4. Char generation expected ( unburnts )

=====
krish

________________________________________________________________________
Want to chat instantly with your online friends? Get the FREE Yahoo!
Messenger http://mail.messenger.yahoo.co.uk

From tombreed at COMCAST.NET Sat Oct 11 09:41:14 2003
From: tombreed at COMCAST.NET (tombreed)
Date: Tue Aug 10 18:24:30 2004
Subject: [STOVES] "Combustor", Gasifier" or Pyrolyser"
Message-ID: <SAT.11.OCT.2003.074114.0600.TOMBREED@COMCAST.NET>

Dear Tami and All:

The question of the Pyrolysis, Gasification and Combustion sequence has two answers.

The Biot dimensionless number is the ratio of rate of heat delivery to rate of heat conduction inside the heated object,

Nb = (Heat transfer to object)/(conductive heat transfer inside object) = hr/k

(where h is the heat transfer coefficient (J/(cm2-K-/sec)); k is the thermal conductivity
(J/(cm2-(K/cm)-/sec)) and r is a characteristic radius of the object. (The r is required because k depends on the temperature gradient (K/cm), while h only depends on the temperature difference, K. )
~~~~~~~~~
When the Biot number is <~0.1, heat conduction makes the particle ~isothermal, and first it dries, then pyrolyses to charcoal and volatiles, then the charcoal gasifies and finally the gases burn if air is supplied. This is the sequence in low intensity pyrolysis and most fires.

When the Biot number is >1, time is required for the temperature to reach the center, so you can observe the outside surface fully charred and gasifying while the center is still moist. (This is easily visible pyrolysing dowells in a Meeker burner.)

(When 0.1<Nb < 1, go calculate!)

I have named this effect "Simultaneous Pyrolysis and Gasification", SPG, in the paper

SUPERFICIAL VELOCITY - THE KEY TO DOWNDRAFT GASIFICATION1T. B. Reeda, R. Waltb, S. Ellisc, A. Dasd, S. Deutchea The Biomass Energy Foundation, 1810 Smith Rd., Golden, CO 80401; b Community Power Corporation,Aurora, CO, c Colorado School of Mines, Golden, CO, d Original Sources, Boulder, CO, e The NationalRenewable Energy Laboratory, Golden, CO.ABSTRACTThe "superficial velocity" (hearth load) of a gasifier is the most important measure of itsperformance, controlling gas production rate, gas energy content, fuel consumption rate,power output, and char and tar production rate.The superficial velocity, SV, of a gasifier is defined as:SV = Gas Production Rate/Cross Sectional Area = (m3/s)/(m2/s) = m/sIt is easily estimated or measured by measuring gas production rate or fuel throughput andgasifier dimensions. It controls the rate at which air, then gas, passes down through agasifier. This in turn exercises a primary effect on heat transfer around each particle duringflaming pyrolysis of the volatiles, combustion of the tars and gasification of the charcoal.A low SV causes relatively slow pyrolysis conditions at around 600?C, and produces highyields of charcoal - 20-30%, large quantities of unburned tars, and a gas with highhydrocarbon content and high tar (volatile) content. A high SV causes very fast pyrolysis,producing less than 10% char-ash at 1050 C and hot gases at 1200-1400 C in the flamingpyrolysis zone. These gases then react with the remaining char-ash to yield tars typically lessthan 1000 ppm, 5-7% char-ash and a producer gas with less energy.These relationships have been investigated in a velocity controlled inverted downdraftgasifier with a 7.5 cm diameter. As the superficial velocity was varied from 0.05 m/s to0.26m/s , the gas production rate increased from 102 to 679 cm3/s, charcoal productiondecreased from 13.0% to 4.7% and tar in the gas decreased from 8330 to 300 mg/kg (ppm).At low Superficial Velocities (and low Biot numbers), the particles are heated slowly topyrolysis temperature and remain essentially isothermal. At high superficial velocities theoutside of the particle can be incandescent (> 800?C) while the center is still at roomtemperature. This permits the escaping gases to react with the charcoal, thus reducing thecharcoal yield and increasing the gas yield. We call this phenomenon "simultaneouspyrolysis and gasification", SPG and believe that it is the fundamental reason why theSuperficial Velocity controls all other aspects of gasification.In producing heat the "tars" in producer gas are a useful fuel, providing no cold surfacesintervene. The "inverted downdraft" stoves provide potentially simple, clean cooking fordeveloping countries. At low SVs they also produce charcoal. In producing electric power,tars are detrimental to engine operation, and so high SVs must be maintained to minimize tarand char production.*Presented at 4th Biomass Conference of the Americas; Oakland, CA, 8/29/99which is on my website at www.woodgas.com.
~~~~~~~~~~~~
So the INTENSITY of heating during pyrolysis plays an important role in the products.

Downdraft gasification forces the partial combustion of the pyrolysis gases to form CO and H2 to occur in the interstices between the particles, and so the heat transfer is more intense than that produce in a fluidized bed.

Comments?

Onward.......

TOM REED

Yours truly,

Dr. Thomas Reed
tombreed@comcast.com
www.woodgas.com
----- Original Message -----
From: "Tami Bond" <yark@UIUC.EDU>
To: <STOVES@LISTSERV.REPP.ORG>
Sent: Saturday, October 11, 2003 4:27 AM
Subject: Re: [STOVES] "Combustor", Gasifier" or Pyrolyser"

> Hi Prasad
>
> It is nice to have your voice.
>
> >I am frankly baffled by this discussion. Sticking to the combustion of wood,
> >I thought that it occurs in the following order. (i) first the moisture in
> >the wood is driven out (<100C); (ii) then pyrolysis occcurs (say <500C); and
> >(iii) combustion follows (around 1000C or more).
>
> Can you clarify WHERE these temperatures occur? It is my understanding that
> 1000C+ is the temperature in the gas-phase during flaming combustion (which
> of course may feed back to the solid if it is close enough in space). My
> understanding of the gasifying stove is that the processes are separated,
> and that lower temperatures do occur at the solid, producing smoke and
> products of incomplete combustion. The beauty of the gasifying stove is
> that a little downstream, the PICs are consumed in a gas-phase flame
> reaction (which would be >1000C), so the occurrence of lower temperatures
> at an earlier point is acceptable. There are two ways to make sure you
> don't emit smoke: either (1) you don't release it by making sure the whole
> mix of pyrolysis/gas-phase burning (which you usually see as a chunk of
> wood on fire) is hot enough, or (2) you let the wood smoke and burn
> everything a bit later. If (1), you are challenged with keeping heat in and
> heat-release rate sufficient; if (2), you are challenged with keeping that
> downstream flame going, or the burner smokes like crazy.
>
> Does that make sense or am I missing the point, Tom?
>
> Tami
>

From tmiles at TRMILES.COM Sun Oct 12 15:00:43 2003
From: tmiles at TRMILES.COM (Tom Miles)
Date: Tue Aug 10 18:24:30 2004
Subject: Fw: Second Conference on Biomass for Energy
Message-ID: <SUN.12.OCT.2003.120043.0700.TMILES@TRMILES.COM>

----- Original Message -----
From: Tetyana Zhelezna
Sent: Friday, October 10, 2003 6:33 AM
Subject: Fw: Second Conference on Biomass for Energy

Dear colleagues!

You are cordially invited to participate in the Second International Ukrainian Conference on Biomass for Energy, 20-22 September 2004 (Kiev)

First announcement and Call for paper can be found at:

http://www.repp.org/discussiongroups/resources/First_call_2004_en.htm

Best regards,

Tetyana Zhelyezna

-----------------------------------------------------

Dr Tetyana A. Zhelyezna

Scientific Secretary of the Conference on Biomass for Energy

(20-22 September 2004, Kiev, Ukraine)

Tel./fax: +380 44 456 9462

Fax: +380 44 456 6282

e-mail: zhelyezna@biomass.kiev.ua

http://www.biomass.kiev.ua

From sschuck at BIGPOND.NET.AU Sun Oct 12 17:52:02 2003
From: sschuck at BIGPOND.NET.AU (Stephen Schuck)
Date: Tue Aug 10 18:24:30 2004
Subject: Bioenergy Australia 2003 conference
Message-ID: <MON.13.OCT.2003.075202.1000.SSCHUCK@BIGPOND.NET.AU>

Please note that the Bioenergy Australia 2003 annual conference will be held
in Sydney, Australia from 8-9 December at the Novotel Brighton Beach hotel.
The program and registration details may be accessed from
www.bioenergyaustralia.org or found at www.conferenceaction.com.au. There
will be a technical tour on 10 December to the Biomass Energy Services and
Technology gasifier and also to a nearly biodiesel plant (40 ML/year) which
includes a cogeneration facility. Early bird registrations close on 31
October.

I hope to see you there!

Dr Steve Schuck
Bioenergy Austalia Manager

Secretariat:
7 Grassmere Rd
Killara NSW 2071
Australia
Phone/Fax: intl (612) 9416-9246
Web Address: www.bioenergyaustralia.org

From a31ford at INETLINK.CA Mon Oct 13 09:48:12 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:30 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
Message-ID: <MON.13.OCT.2003.084812.0500.A31FORD@INETLINK.CA>

Hello All,

This is my "First" official question (post) to this list (even though I've
been reading for about a year or so).

In all versions (except one) of downdraft co-current or batch process
gasifiers (of the ones I have seen, or found on the web), have a restriction
in the char bed area, but alas, I cannot find an answer as to why. the
restriction is from 5cm to 70cm on average and appears to be the main
problem of "bridging" or "feedstock lockups".

Is it simply that most designs are built with the top of the gasification
unit at "head height" as to be filled while standing on the ground (batch
process), and the restriction is simply there so a greater amount of
feedstock can be placed, or is there something I know nothing about when it
comes to feedstock movement through the char bed and down?

the one version I have found that does not use a "restricted throat char
bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
notice the restriction is above the char bed.

Any and all help on this one simple question, would greatly enlighten me.

Greg Manning
Brandon, Manitoba, Canada

From tombreed at COMCAST.NET Mon Oct 13 09:52:07 2003
From: tombreed at COMCAST.NET (tombreed)
Date: Tue Aug 10 18:24:30 2004
Subject: The Role of the choke in downdraft gasification
Message-ID: <MON.13.OCT.2003.075207.0600.TOMBREED@COMCAST.NET>

Dear Greg:

Excellent question, and one that I have danced around for many years.

As wood becomes pyrolysed in the first stage of "flaming pyrolysis", it can
turn to a pretty robust charcoal plus CO, CO2, H2 and H2O. As the VERY hot
gases generated in flaming pyrolysis (1000-1500C) pass through this
charcoal, they react to form additional CO and H2, and effectively "leach"
the charcoal so that it loses strength and begins to break up into smaller
pieces that can drop out to a cooler section and nor react further, or can
be held up and further gasified, but with additional pressure drop due to
the packing of the charcoal bed.

The degree of char breakup is controlled by either a grate or a choke or
both. I initially thought that the choke was counterproductive in a system
where you wanted continuous flow without bridging. However, a cylindrical
gasifier has a "virtual taper" automatically built in, since the conversion
to charcoal causes 30% shrinkage, and the leaching and breakup continues
that process.

The choke then follows this taper and allows the gasifier to "hang on to the
charcoal" through the final char gasification. It is effectively a smaller
charcoal gasifier on the bottom of the wood pyrolysis gasifier.

It also serves to keep the gas velocity high enough so that when the char
particles are small enough they can be carried to the cyclone or other char
separator.

I doubt if Jacques Imbert knew or cared much about this when he invented the
classic WWII gasifier. I certainly didn't know about it when we developed
the stratified downdraft gasifier at NREL and SynGas in the 1980-88 period.
However, in our "Handbook of Downdraft Gasifier Engine Systems", there are
detailed tables from Gengas showing the optimum relationships used for choke
size relative to engine horsepower. These tables would be relevant to
hardwood wood blocks only. I suspect the dimensions would be very different
for softwoods or densified wood pellets.

We still have a lot to learn about gasification and I hope someone gets
serious about it before the next oil crisis.... (and I hope this note
doesn't muddy the water farther).

Yours truly,

Dr. Thomas Reed, List Moderator

tombreed@comcast.com
www.woodgas.com
----- Original Message -----
From: "a31ford" <a31ford@INETLINK.CA>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Monday, October 13, 2003 7:48 AM
Subject: [GASL] Woodchip, Co-current Downdraft, Restricted Throat, Questions

> Hello All,
>
> This is my "First" official question (post) to this list (even though I've
> been reading for about a year or so).
>
> In all versions (except one) of downdraft co-current or batch process
> gasifiers (of the ones I have seen, or found on the web), have a
restriction
> in the char bed area, but alas, I cannot find an answer as to why. the
> restriction is from 5cm to 70cm on average and appears to be the main
> problem of "bridging" or "feedstock lockups".
>
> Is it simply that most designs are built with the top of the gasification
> unit at "head height" as to be filled while standing on the ground (batch
> process), and the restriction is simply there so a greater amount of
> feedstock can be placed, or is there something I know nothing about when
it
> comes to feedstock movement through the char bed and down?
>
> the one version I have found that does not use a "restricted throat char
> bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
> notice the restriction is above the char bed.
>
> Any and all help on this one simple question, would greatly enlighten me.
>
> Greg Manning
> Brandon, Manitoba, Canada
>

From dschmidt at UNDEERC.ORG Mon Oct 13 10:31:18 2003
From: dschmidt at UNDEERC.ORG (Schmidt, Darren)
Date: Tue Aug 10 18:24:30 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Que stions
Message-ID: <MON.13.OCT.2003.093118.0500.DSCHMIDT@UNDEERC.ORG>

I'll take a stab at this one.

The typical goal of any gasifier is to produce a gas from solid fuel that
meets a given specification. All gasifiers must have a heat source to
initiate reaction with the fuel to produce gas. Typically on this site we
are talking about air blown gasification where combustion of the fuel is
used to provide heat necessary to drive gasification reactions. Also, the
goal is to produce a low Btu (< 150Btu/scf) gas that contains few heavy
hydrocarbons for the purpose of electrical power production.

With that said,
High heat zones in the gasifier help to crack heavy hydrocarbons to lower
hydrocarbons (hence make clean gas). The throat in an imbert style gasifier
forces most of the produced gas to pass through a high temperature zone.
This high temperature zone's location is controlled by the location of the
air inlet nozzles inside the throat area. The throat is relatively small to
minimize any cold spots. The throat on an imbert style gasifier is
restrictive to the flow of solids.

Throatless, Open cylinder, or stratified downdraft gasifiers do not have a
throat, thus do not restrict the flow of solids. However it can be a bit
more difficult to control the reactor. With an imbert, the air inlet
nozzles determine the location of the combustion zone and solids flow is
controlled by the ash removal system. With a stratified gasifier, solids
flow is controlled in the same manner, but the location of the combustion
zone is somewhat uncontrolled. Temperature measurement is the only
indication of location and care must be taken to prevent burning through at
the top, or letting the combustion zone migrate to the bottom. If the
gasifier is too large in diameter, channels can form, and solids flow on one
side of the cylinder may differ from the other. Any irregularities can
cause gas quality problems.

The throat of an imbert style gasifier is designed such that the air inlet
velocity of the nozzles provides a air distribution profile that covers the
majority of the throat area. The stratified gasifier uses a layer of wood
on top of the combustion zone to act as an air distributor to the combustion
zone.

Darren Schmidt,
UND
EERC
Grand Forks, ND USA

-----Original Message-----
From: a31ford [mailto:a31ford@INETLINK.CA]
Sent: Monday, October 13, 2003 8:48 AM
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
Questions

Hello All,

This is my "First" official question (post) to this list (even though I've
been reading for about a year or so).

the one version I have found that does not use a "restricted throat char
bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
notice the restriction is above the char bed.

Any and all help on this one simple question, would greatly enlighten me.

Greg Manning
Brandon, Manitoba, Canada

From a31ford at INETLINK.CA Mon Oct 13 11:21:35 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:30 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
In-Reply-To: <3F678EC15E6D8F4EA7CDC3F389D9CC7E613C0A@undeerc.eerc.und.NoDak.edu>
Message-ID: <MON.13.OCT.2003.102135.0500.A31FORD@INETLINK.CA>

Tom and Darren, Thank you for your enlightening answers !!

At this point (now confirming my very basic knowledge of feedstock flow) I
poise these 3 questions.

1) In relationship to the "virtual taper" vs. "throat tube", (See Tom's
answer below) would one think a softer transition from air nozzles area to
throat tube would be advantageous in prevention of feedstock lock-ups (note:
not bridging in the throat)?

2) Also, in relationship of "throat tube" vs. "charcoal reninition time in
the throat", would a rough inside surface of the throat be advantageous to
retaining charcoal, for cracking heavy hydrocarbons (tars), (See Darren's
answer below) in the gas stream (effectively "a virtual set of grates" above
the true grate) ?

3) Last one, heat, heat, heat, again, all the systems I have encountered,
are using the "throat tube" in the "gas collection" chamber, (thereby
utilizing the hot gas as an "insulator", Would there be, (in a NON-CHP, heat
only system) an advantage of using the actual gas ignition chamber
"surrounding the throat area" produce a "superheated" throat, would this
cause a "thermal runaway effect", or simply a "tars" reduction" (NOTE:
reduction being that the superheated throat would be more effective at
achieving a near 100% burn)?

(Now I know, I know nothing about what I'm talking about). :)

Greg Manning

-----Original Message-----
From: The Gasification Discussion List
[mailto:GASIFICATION@LISTSERV.REPP.ORG]On Behalf Of Schmidt, Darren
Sent: Monday, October 13, 2003 9:31 AM
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
Que stions

I'll take a stab at this one.

Darren Schmidt,
UND
EERC
Grand Forks, ND USA

NOTE: Also included is Tom Reed's Answer.

Dear Greg:

Excellent question, and one that I have danced around for many years.

It also serves to keep the gas velocity high enough so that when the char
particles are small enough they can be carried to the cyclone or other char
separator.

We still have a lot to learn about gasification and I hope someone gets
serious about it before the next oil crisis.... (and I hope this note
doesn't muddy the water farther).

Yours truly,

Dr. Thomas Reed, List Moderator

tombreed@comcast.com
www.woodgas.com

Hello All,

This is my "First" official question (post) to this list (even though I've
been reading for about a year or so).

the one version I have found that does not use a "restricted throat char
bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
notice the restriction is above the char bed.

Any and all help on this one simple question, would greatly enlighten me.

Greg Manning
Brandon, Manitoba, Canada

From dschmidt at UNDEERC.ORG Mon Oct 13 11:51:03 2003
From: dschmidt at UNDEERC.ORG (Schmidt, Darren)
Date: Tue Aug 10 18:24:30 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Que stions
Message-ID: <MON.13.OCT.2003.105103.0500.DSCHMIDT@UNDEERC.ORG>

1) From a practical standpoint - The only reason I can get biomass to move
through a throat in the imbert gasifier is because the combustion takes
place at that location and a lot of material shifting is helping solids flow
through the restriction (plus vibration). If I have any restriction above
the combustion zone solids will bridge. Old imberts used the vibration of
the automobile to solve this problem. Other imbert style gasifiers do not
have a restriction above the combustion zone, only below. I think a gradual
taper would not work.

2.) You are likely to cause solids flow problems with a rough surface. This
would not help your intent described below.

3.) I don't understand #3. If you have a thermal application and clean gas
is not required (heat only). Downdraft gasification is probably overkill.
Updraft, grate fired, or fluid bed are all viable options for thermal
applications and much easier in terms of solids flow.

-----Original Message-----
From: a31ford [mailto:a31ford@INETLINK.CA]
Sent: Monday, October 13, 2003 10:22 AM
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
Questions

Tom and Darren, Thank you for your enlightening answers !!

At this point (now confirming my very basic knowledge of feedstock flow) I
poise these 3 questions.

(Now I know, I know nothing about what I'm talking about). :)

Greg Manning

I'll take a stab at this one.

Darren Schmidt,
UND
EERC
Grand Forks, ND USA

NOTE: Also included is Tom Reed's Answer.

Dear Greg:

Excellent question, and one that I have danced around for many years.

It also serves to keep the gas velocity high enough so that when the char
particles are small enough they can be carried to the cyclone or other char
separator.

We still have a lot to learn about gasification and I hope someone gets
serious about it before the next oil crisis.... (and I hope this note
doesn't muddy the water farther).

Yours truly,

Dr. Thomas Reed, List Moderator

tombreed@comcast.com
www.woodgas.com

Hello All,

This is my "First" official question (post) to this list (even though I've
been reading for about a year or so).

the one version I have found that does not use a "restricted throat char
bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
notice the restriction is above the char bed.

Any and all help on this one simple question, would greatly enlighten me.

Greg Manning
Brandon, Manitoba, Canada

From tombreed at COMCAST.NET Mon Oct 13 15:33:28 2003
From: tombreed at COMCAST.NET (tombreed)
Date: Tue Aug 10 18:24:30 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Que stions
Message-ID: <MON.13.OCT.2003.133328.0600.TOMBREED@COMCAST.NET>

Dear Darren and All:

It is great to see an informed discussion of the subtleties of the Imbert
and the Stratified Downdraft gasifiers. More here than any I've seen in
years....

Yours truly,

Dr. Thomas Reed

tombreed@comcast.com
www.woodgas.com
----- Original Message -----
From: "Schmidt, Darren" <dschmidt@UNDEERC.ORG>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Monday, October 13, 2003 9:51 AM
Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat, Que
stions

> 1) From a practical standpoint - The only reason I can get biomass to move
> through a throat in the imbert gasifier is because the combustion takes
> place at that location and a lot of material shifting is helping solids
flow
> through the restriction (plus vibration). If I have any restriction above
> the combustion zone solids will bridge. Old imberts used the vibration of
> the automobile to solve this problem. Other imbert style gasifiers do not
> have a restriction above the combustion zone, only below. I think a
gradual
> taper would not work.
>
> 2.) You are likely to cause solids flow problems with a rough surface.
This
> would not help your intent described below.
>
> 3.) I don't understand #3. If you have a thermal application and clean
gas
> is not required (heat only). Downdraft gasification is probably overkill.
> Updraft, grate fired, or fluid bed are all viable options for thermal
> applications and much easier in terms of solids flow.
>
> -----Original Message-----
> From: a31ford [mailto:a31ford@INETLINK.CA]
> Sent: Monday, October 13, 2003 10:22 AM
> To: GASIFICATION@LISTSERV.REPP.ORG
> Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
> Questions
>
>
> Tom and Darren, Thank you for your enlightening answers !!
>
> At this point (now confirming my very basic knowledge of feedstock flow) I
> poise these 3 questions.
>
> 1) In relationship to the "virtual taper" vs. "throat tube", (See Tom's
> answer below) would one think a softer transition from air nozzles area to
> throat tube would be advantageous in prevention of feedstock lock-ups
(note:
> not bridging in the throat)?
>
> 2) Also, in relationship of "throat tube" vs. "charcoal reninition time in
> the throat", would a rough inside surface of the throat be advantageous to
> retaining charcoal, for cracking heavy hydrocarbons (tars), (See Darren's
> answer below) in the gas stream (effectively "a virtual set of grates"
above
> the true grate) ?
>
> 3) Last one, heat, heat, heat, again, all the systems I have encountered,
> are using the "throat tube" in the "gas collection" chamber, (thereby
> utilizing the hot gas as an "insulator", Would there be, (in a NON-CHP,
heat
> only system) an advantage of using the actual gas ignition chamber
> "surrounding the throat area" produce a "superheated" throat, would this
> cause a "thermal runaway effect", or simply a "tars" reduction" (NOTE:
> reduction being that the superheated throat would be more effective at
> achieving a near 100% burn)?
>
> (Now I know, I know nothing about what I'm talking about). :)
>
> Greg Manning
>
>
> -----Original Message-----
> From: The Gasification Discussion List
> [mailto:GASIFICATION@LISTSERV.REPP.ORG]On Behalf Of Schmidt, Darren
> Sent: Monday, October 13, 2003 9:31 AM
> To: GASIFICATION@LISTSERV.REPP.ORG
> Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
> Que stions
>
>
> I'll take a stab at this one.
>
> The typical goal of any gasifier is to produce a gas from solid fuel that
> meets a given specification. All gasifiers must have a heat source to
> initiate reaction with the fuel to produce gas. Typically on this site we
> are talking about air blown gasification where combustion of the fuel is
> used to provide heat necessary to drive gasification reactions. Also, the
> goal is to produce a low Btu (< 150Btu/scf) gas that contains few heavy
> hydrocarbons for the purpose of electrical power production.
>
> With that said,
> High heat zones in the gasifier help to crack heavy hydrocarbons to lower
> hydrocarbons (hence make clean gas). The throat in an imbert style
gasifier
> forces most of the produced gas to pass through a high temperature zone.
> This high temperature zone's location is controlled by the location of the
> air inlet nozzles inside the throat area. The throat is relatively small
to
> minimize any cold spots. The throat on an imbert style gasifier is
> restrictive to the flow of solids.
>
> Throatless, Open cylinder, or stratified downdraft gasifiers do not have a
> throat, thus do not restrict the flow of solids. However it can be a bit
> more difficult to control the reactor. With an imbert, the air inlet
> nozzles determine the location of the combustion zone and solids flow is
> controlled by the ash removal system. With a stratified gasifier, solids
> flow is controlled in the same manner, but the location of the combustion
> zone is somewhat uncontrolled. Temperature measurement is the only
> indication of location and care must be taken to prevent burning through
at
> the top, or letting the combustion zone migrate to the bottom. If the
> gasifier is too large in diameter, channels can form, and solids flow on
one
> side of the cylinder may differ from the other. Any irregularities can
> cause gas quality problems.
>
> The throat of an imbert style gasifier is designed such that the air inlet
> velocity of the nozzles provides a air distribution profile that covers
the
> majority of the throat area. The stratified gasifier uses a layer of wood
> on top of the combustion zone to act as an air distributor to the
combustion
> zone.
>
> Darren Schmidt,
> UND
> EERC
> Grand Forks, ND USA
>
>
> NOTE: Also included is Tom Reed's Answer.
>
> Dear Greg:
>
> Excellent question, and one that I have danced around for many years.
>
> As wood becomes pyrolysed in the first stage of "flaming pyrolysis", it
can
> turn to a pretty robust charcoal plus CO, CO2, H2 and H2O. As the VERY
hot
> gases generated in flaming pyrolysis (1000-1500C) pass through this
> charcoal, they react to form additional CO and H2, and effectively "leach"
> the charcoal so that it loses strength and begins to break up into smaller
> pieces that can drop out to a cooler section and nor react further, or can
> be held up and further gasified, but with additional pressure drop due to
> the packing of the charcoal bed.
>
> The degree of char breakup is controlled by either a grate or a choke or
> both. I initially thought that the choke was counterproductive in a
system
> where you wanted continuous flow without bridging. However, a cylindrical
> gasifier has a "virtual taper" automatically built in, since the
conversion
> to charcoal causes 30% shrinkage, and the leaching and breakup continues
> that process.
>
> The choke then follows this taper and allows the gasifier to "hang on to
the
> charcoal" through the final char gasification. It is effectively a
smaller
> charcoal gasifier on the bottom of the wood pyrolysis gasifier.
>
> It also serves to keep the gas velocity high enough so that when the char
> particles are small enough they can be carried to the cyclone or other
char
> separator.
>
> I doubt if Jacques Imbert knew or cared much about this when he invented
the
> classic WWII gasifier. I certainly didn't know about it when we developed
> the stratified downdraft gasifier at NREL and SynGas in the 1980-88
period.
> However, in our "Handbook of Downdraft Gasifier Engine Systems", there are
> detailed tables from Gengas showing the optimum relationships used for
choke
> size relative to engine horsepower. These tables would be relevant to
> hardwood wood blocks only. I suspect the dimensions would be very
different
> for softwoods or densified wood pellets.
>
> We still have a lot to learn about gasification and I hope someone gets
> serious about it before the next oil crisis.... (and I hope this note
> doesn't muddy the water farther).
>
> Yours truly,
>
> Dr. Thomas Reed, List Moderator
>
> tombreed@comcast.com
> www.woodgas.com
>
>
> -----Original Message-----
> From: a31ford [mailto:a31ford@INETLINK.CA]
> Sent: Monday, October 13, 2003 8:48 AM
> To: GASIFICATION@LISTSERV.REPP.ORG
> Subject: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
> Questions
>
>
> Hello All,
>
> This is my "First" official question (post) to this list (even though I've
> been reading for about a year or so).
>
> In all versions (except one) of downdraft co-current or batch process
> gasifiers (of the ones I have seen, or found on the web), have a
restriction
> in the char bed area, but alas, I cannot find an answer as to why. the
> restriction is from 5cm to 70cm on average and appears to be the main
> problem of "bridging" or "feedstock lockups".
>
> Is it simply that most designs are built with the top of the gasification
> unit at "head height" as to be filled while standing on the ground (batch
> process), and the restriction is simply there so a greater amount of
> feedstock can be placed, or is there something I know nothing about when
it
> comes to feedstock movement through the char bed and down?
>
> the one version I have found that does not use a "restricted throat char
> bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
> notice the restriction is above the char bed.
>
> Any and all help on this one simple question, would greatly enlighten me.
>
> Greg Manning
> Brandon, Manitoba, Canada
>

From a31ford at INETLINK.CA Tue Oct 14 08:38:53 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:30 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
In-Reply-To: <3F678EC15E6D8F4EA7CDC3F389D9CC7E613C11@undeerc.eerc.und.NoDak.edu>
Message-ID: <TUE.14.OCT.2003.073853.0500.A31FORD@INETLINK.CA>

Darren, thank you for your answers!

But I think I might of only given you 1/2 of the info in my original
questions in the second place, so I'll try to clarify the original
questions, for myself & others reading this.

1) I was speaking of the area only between the air nozzles and the throat,
the area above the nozzles is still just a tube. (note: external vibration
will be provided via air driven vibrator, running in cycle mode eg: 15sec
on, 15min off).

2) Throat, the grate acts as a choke & retainer of char, my idea was to
resize the openings in the grate, and roughen the inside surface of the
throat, thereby creating drag where it's needed (Tom's original answer of
"virtual taper" would apply) as the char reduces in size it would fall
slightly, and catch at a lower point in the throat, repeating, over & over
as it burned smaller & smaller, hence "virtual grate"

3) Imagine if you will, a burn chamber of a standard coal fired boiler, 2 or
3 pass with all those tubes running through the water. Now imagine the
exterior of the throat area being exposed to open air with the bio-gas
collection tank at the lower most point of the throat (leaving a small
amount in the lower tank), and the upper feedstock tank feeding the throat
as to form an hourglass shape. (Note: I remember that one can place a lit
match on the far side of a water glass, and still extinguish it by blowing
on the near side of the glass),(basic airflow). now surround that center
section of the hourglass with the bio-gas burn chamber (the 2 flows, char in
the throat, and the "blue flame" of bio, in isolated but thermally crossing
paths). Like the tubes in a boiler. Remembering that this is a heat only
system, with inline flue heat exchangers for all needed forms of heat (water
for buildings, preheat of air for burn, preheat of feedstock).

SIDE NOTE for Item #3, CHP is on the "do list" but getting clean gas is the
starting point, as most say, "cleaner from the gasifier is easier to work
with, in the first place".

Most of the populated world does not need "heat only systems" but in my neck
of the woods, Minus 50c is quite cold, 6 months of the year..... :)

Anyone wishing to reply, please do, as we are in mid October, and it's
already dipping to Minus 5c at night.

Greg Manning,
Brandon, Manitoba, Canada

-----Original Message-----
From: The Gasification Discussion List
[mailto:GASIFICATION@LISTSERV.REPP.ORG]On Behalf Of Schmidt, Darren
Sent: Monday, October 13, 2003 10:51 AM
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
Que stions

2.) You are likely to cause solids flow problems with a rough surface. This
would not help your intent described below.

Tom and Darren, Thank you for your enlightening answers !!

At this point (now confirming my very basic knowledge of feedstock flow) I
poise these 3 questions.

(Now I know, I know nothing about what I'm talking about). :)

Greg Manning

I'll take a stab at this one.

Darren Schmidt,
UND
EERC
Grand Forks, ND USA

NOTE: Also included is Tom Reed's Answer.

Dear Greg:

Excellent question, and one that I have danced around for many years.

It also serves to keep the gas velocity high enough so that when the char
particles are small enough they can be carried to the cyclone or other char
separator.

We still have a lot to learn about gasification and I hope someone gets
serious about it before the next oil crisis.... (and I hope this note
doesn't muddy the water farther).

Yours truly,

Dr. Thomas Reed, List Moderator

tombreed@comcast.com
www.woodgas.com

Hello All,

This is my "First" official question (post) to this list (even though I've
been reading for about a year or so).

the one version I have found that does not use a "restricted throat char
bed" can be seen here > http://bgg.mek.dtu.dk/research/twostage/ if you
notice the restriction is above the char bed.

Any and all help on this one simple question, would greatly enlighten me.

Greg Manning
Brandon, Manitoba, Canada

From claush at MEK.DTU.DK Tue Oct 14 10:50:49 2003
From: claush at MEK.DTU.DK (Claus Hindsgaul)
Date: Tue Aug 10 18:24:31 2004
Subject: The Role of the choke in downdraft gasification
In-Reply-To: <009701c39191$31254f40$b5affd0c@TOMBREED>
Message-ID: <TUE.14.OCT.2003.165049.0200.CLAUSH@MEK.DTU.DK>

As Tom Reed noted, this is an interesting question.

The role of reactor dimensions and char behaviour seems to be very
important to the stability of operation (gas quality, pressure drop and
"dead zones" due to skewed flow). Char breakage during gasification is
the very topic of my Ph.D. study (initiated February 2003).

I am working at the two stage gasification project (the one Greg
mentioned as the only one he found without a restricted throat char bed.
We actually just started it again this morning after 3 weeks of
inspections). The way the high temperature zone has been implemented in
the Viking gasifier (above the char bed) seems to allow for larger
reactors still maintaining a good heat distribution in the high
temperature tar cracking zone.

But as any other fixed bed process we still need the bed to be
sufficiently permeable to the gas flow, and this permeability should be
evenly distributed horisontally in the bed in order to avoid dead zones
with low flow and conversion. In order to estimate what happens if we
scale up a fixed bed, we have built simple flow models to predict e.g.
chanelling behaviour and flow distribution.

But knowledge on the physical behaviour of char particles in a fixed bed
is limited. Nobody *really* knows how char breaks during conversion and
which parameters are important for this breakage. The local size
distribution of the partially converted and fragmented char is vital to
the permeability in the bed.

Theories and experiences from the coal industry as well as our initial
investigations of char beds seem to indicate that the breakage of
coke/char particles in a gasification process (note, NOT PYROLYSIS!) is
dominated by fines (<1 mm) leaving the surface of the particle rather
than the particle breaking into a few equally sized pieces.
If the gasification reactions happen mainly on the particle surface
(e.g. at high temperatures), ash rich fines leave when the surface
conversion (and thereby surface strength) reach a critical level.
If gasification reactions happen evenly in the particle (e.g. low
temperatures), the surface is still subject to the largest tensions, and
small fragments tend to leave the surface when subject to mechanical
impact (example: using charcoal as a writing tool).

I hope my study will provide more knowledge on which parameters are
important to char breakage during conversion (fuel properties, reaction
rates etc.) and create input for better fixed bed and fluid bed models
in the future, so that fx. larger reactors can be designed with
confidence for stable operation.

I am of course very interested in hearing other peoples hands-on
experience with char breakage and behaviour in fixed beds.

Claus Hindsgaul

--
Ph.D. Student Claus Hindsgaul
Biomass Gasification Group, Dept. Mechanical Eng. (MEK), DTU
and CHEC, Dept. Chemical Eng. (KT), DTU
http://bgg.mek.dtu.dk/ and http://www.kt.dtu.dk/
Phone +45 4525 4174

From sensiblesteam at AOL.COM Tue Oct 14 18:45:35 2003
From: sensiblesteam at AOL.COM (Skip Goebel)
Date: Tue Aug 10 18:24:31 2004
Subject: catalyst/refractory
Message-ID: <TUE.14.OCT.2003.184535.0400.SENSIBLESTEAM@AOL.COM>

all this discussion on charcol clogging throats has me wondering if we are
talking about unrefracted surfaces. if the throat is lined with
refractory, especially if it was something like cera blanket with ss
expanded metal covering it, i would think the edges would burn off with the
slightest of air admitted.
skip
sensible steam

From a31ford at INETLINK.CA Tue Oct 14 21:55:23 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:31 2004
Subject: The Role of the choke in downdraft gasification
In-Reply-To: <1066143045.27047.62.camel@ip7071120.mek.dtu.dk>
Message-ID: <TUE.14.OCT.2003.205523.0500.A31FORD@INETLINK.CA>

Claus, I wish to also thank you, for your input on this.

Since you are a person directly involved with the Viking Unit, I am awed!
(My prototype will be somewhat based on the Viking principals, but on a much
smaller and crude scale).
FYI, I am a lone person doing this, not a company, or university.

As all of us (so it appears) have problems in the char bed, this is the area
that I wish to concentrate on also. (believing that this is the most
important aspect in any gasifier). The "virtual throat" that Tom Reed spoke
of, I feel is the biggest portion of that factor, in this char/fines issue.

Quite a while back, I had an e-mail conversation with John Gulland from
http://www.woodheat.org about my fancy to do this gasifier, (John is not a
supporter of 'outdoor boilers', or DIY {do it yourself}, simply for safety
reasons) but quoting him "get the burn right, extracting the heat is the
easy part". It took me about 3 weeks of thought on that one statement, but
alas I have seen & understood the light!

I am keeping every scrap of paper "notes" that are accumulating on this
project, scanning and sorting them.

I would be happy to post my findings as progress occurs.

Greg Manning,
Brandon, Manitoba, Canada

-----Original Message-----
From: The Gasification Discussion List
[mailto:GASIFICATION@LISTSERV.REPP.ORG]On Behalf Of Claus Hindsgaul
Sent: Tuesday, October 14, 2003 9:51 AM
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: Re: [GASL] The Role of the choke in downdraft gasification

As Tom Reed noted, this is an interesting question.

I am of course very interested in hearing other peoples hands-on
experience with char breakage and behaviour in fixed beds.

Claus Hindsgaul

From Tk at TKE.DK Wed Oct 15 05:02:49 2003
From: Tk at TKE.DK (Thomas Koch)
Date: Tue Aug 10 18:24:31 2004
Subject: catalyst/refractory
Message-ID: <WED.15.OCT.2003.110249.0200.TK@TKE.DK>

Yes they will.
Ceramics in reducing atmospheres is a big challenge.

Thomas Koch

----- Original Message -----
From: "Skip Goebel" <sensiblesteam@AOL.COM>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Wednesday, October 15, 2003 12:45 AM
Subject: [GASL] catalyst/refractory

> all this discussion on charcol clogging throats has me wondering if we are
> talking about unrefracted surfaces. if the throat is lined with
> refractory, especially if it was something like cera blanket with ss
> expanded metal covering it, i would think the edges would burn off with the
> slightest of air admitted.
> skip
> sensible steam

From graeme at POWERLINK.CO.NZ Wed Oct 15 21:13:00 2003
From: graeme at POWERLINK.CO.NZ (Graeme Williams)
Date: Tue Aug 10 18:24:31 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
Message-ID: <THU.16.OCT.2003.141300.1300.GRAEME@POWERLINK.CO.NZ>

Dear Greg,

Having spent 28 years working with downdraught throated gasifiers, the
following may assist you to understand slightly better the basic principles
of their design.

1: In normal operation the gasifier is filled with charcoal to above the
nozzles where the air enters the bed. The raw wood sits on top of the
charcoal.

2: On ignition the char in front and below the nozzles becomes
incandescent radiating heat upwards into the descending fuel to produce the
charcoal. As the oxygen is consumed as it passes down through the bed, the
flowing gas reaches an equilibrium point where there is a minimum of oxygen
and a maximum of CO2. At this point combustion ceases in the absence of
oxygen, and the throat is located at this point, which is the beginning of
the reduction zone where the gas is actually made. Pyrolisis gases that
evolve above the oxidation zone, should be consumed in the presence of
oxygen and should not survive past the throat which also acts as a high
temperature cracking zone for the heavier hydrocarbons that can slip down
between nozzles etc.

3: The char in the reduction zone reacts with the incandescent CO2 which
should be within a temperature range of 12-1500 degreesC, and shrinks as it
gives up carbon molecules to the CO2 to become CO. Steam is cracked at the
throat into hydrogen and this joins the CO to become the fuel gas. The
continuous shrinkage and consumption of the char from the outlet grate up
through the throat and oxidation zone, enables the flow of fuel to take
place almost under the influence of gravity. Incorrectly designed gasifiers
and\or incorrect fuel do create problems and is the reason for many failures
over the years.

The above basic description can be found in literature, but to copy
published designs in the hope of getting a working gasifier proves fatal to
those who try it. The use of these gasifiers in WW2 for mobile application
masked a lot of problems, and there are a lot of inconsistencies in the
dimensions when the technology is attempted to be used for stationary
application. If it were just a case of copying the existing designs and
they worked, there would be no need for this discussion group or companies
still trying to evolve reliable commercial equipment.

Hope this helps a little.

Regards
Doug Williams.
Fluidyne Gasification.

From a31ford at INETLINK.CA Wed Oct 15 21:41:26 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:31 2004
Subject: Virtual Throat, Imbert Gasifier
In-Reply-To: <017401c391c0$e0c8f300$b5affd0c@TOMBREED>
Message-ID: <WED.15.OCT.2003.204126.0500.A31FORD@INETLINK.CA>

Good Day Tom, Doug, Graeme, and all,

I have been thinking of Tom's "Virtual Throat" and have realized that it is
the true, one & only stumbling block that I must overcome in my still design
phase Gasifier. This has been 3 years in the making, and with the models I
have tried, I know enough, that, I know nothing in the grand scheme, on
things of this nature.

With that said, I am doing the following to model #4:

1) Replacing the existing throat with a 4" x 9" long, thick wall pipe (would
use 304SS but this is testing only) the local "guy with a lathe" said he
could cut internal "cross hatch" in it (like what is on the handle of a
ratchet wrench) in a thin to thick pattern (thick being at the lower end of
the throat) The feedstock I am currently using for testing is roughly 3/4" x
1/4" aspen chips, sorted & cleaned(after preheat, 10-17%MC) no leaf or
"sawdust" content.

2) The existing Model #4 will have no other changes, and has been running
the same type of feedstock through all tests (best model so far, but alas
far from stable in the bottom end).

3) as Doug said, "copying an existing unit" is sure to fail (I agree), but
being a lone person with limited funds, I am simply trying to combine what I
feel is the "best" of what I have seen, read, or heard, and basing that on a
known working unit for reference.

Will keep all informed.

Greg Manning,
Brandon, Manitoba, Canada

From graeme at POWERLINK.CO.NZ Wed Oct 15 22:08:25 2003
From: graeme at POWERLINK.CO.NZ (Graeme Williams)
Date: Tue Aug 10 18:24:31 2004
Subject: The Role of the choke in downdraft gasification
Message-ID: <THU.16.OCT.2003.150825.1300.GRAEME@POWERLINK.CO.NZ>

.Dear Claus

You wrote:

>
> But knowledge on the physical behaviour of char particles in a fixed bed
> is limited. Nobody *really* knows how char breaks during conversion and
> which parameters are important for this breakage. The local size
> distribution of the partially converted and fragmented char is vital to
> the permeability in the bed.

The above statement is a little ambiguous because for any gasifier
manufacturer to offer equipment as state of the art, they must already have
extensive knowledge of fuel bed behaviour. The very distinct changes of
char character at the points where oxidation stops and reduction begins, in
all forms of atmospheric gasifiers, sets the behaviour of how a gasifier
performs.

Having spent many hundreds of hours in the examination of char beds,
removing the particles piece by piece, the knowledge is there for all to
see, but the ability to translate that into a problem free process requires
considerable skill from the manufacturer. There are
indications that this skill is lacking, because when the parameters of a
gasifier are designed correctly, the need to remove or convert uncracked
tars disappears, and a lot of effort is being put into solving this problem.

In seeking opinions from the coal industry and trying to apply this to
biomass will be, from my experience, very confusing. Coal does lose surface
carbon, shrinking in the process, and the best suited fuel size are nuts,
providing a close packed bed and large surface areas on which the reactions
take place.

Wood on the other hand, has lots of variability, with very hard woods
behaving like coal, losing surface carbon, and soft woods, like conifers,
shattering as they enter the oxidation zone. The rapid breaking up of char
naturally increases the surface areas making reaction times faster, and
therefore requiring less depth of beds to complete the gasification process.
The shatter effect also determines the size of the fuel, and is valuable in
the evaluation of wastes.

When ash forms on the surface of wood particles, it is a clear indication
that the air velocity is too low, and if you observe the bed through one of
the nozzles, you can see the surface blackened as the ash prevents the
oxygen reacting with the surface carbon. Even when you have the velocity
right to start with, if the gasification parameters are not correct, bed
restrictions will change the velocity of the nozzle.

There is also another dimension to consider, in that some tropical hard
woods completely collapse at the end of the oxidation phase, where reduction
begins. This completely blocks up the bed, and the gasifier behaves very
badly. I would suggest that a study of those gasifiers supplied to projects
in the Pacific,Asia, and South America during the 1970s and 80s of French,
German and Dutch manufacture would be useful to your study.

We look forward to your thesis.

Kindest Regards
Doug Williams
Fluidyne Gasification.

From Gavin at AA3GENERGI.FORCE9.CO.UK Thu Oct 16 04:42:25 2003
From: Gavin at AA3GENERGI.FORCE9.CO.UK (Gavin Gulliver-Goodall)
Date: Tue Aug 10 18:24:31 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
In-Reply-To: <001401c39382$aab31340$eaff58db@newpc>
Message-ID: <THU.16.OCT.2003.094225.0100.GAVIN@AA3GENERGI.FORCE9.CO.UK>

So the only mistake we have all made is not building our gasifiers on a
vibrating table to simulate the agitation caused by driving pre war cars on
rutted roads!
Wow! To think all the government money lost for a little thinking "out of
the box" and we all thought we were so clever-
Well done Doug- I guess that wasn't the secret of Fluidyne's success?
Gavin

-----Original Message-----
From: The Gasification Discussion List
[mailto:GASIFICATION@LISTSERV.REPP.ORG]On Behalf Of Graeme Williams
Sent: Thursday, October 16, 2003 2:13
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
Questions

Dear Greg,

Having spent 28 years working with downdraught throated gasifiers, the
following may assist you to understand slightly better the basic principles
of their design.

1: In normal operation the gasifier is filled with charcoal to above the
nozzles where the air enters the bed. The raw wood sits on top of the
charcoal.

Hope this helps a little.

Regards
Doug Williams.
Fluidyne Gasification.

From claush at MEK.DTU.DK Thu Oct 16 08:30:35 2003
From: claush at MEK.DTU.DK (Claus Hindsgaul)
Date: Tue Aug 10 18:24:31 2004
Subject: The Role of the choke in downdraft gasification
In-Reply-To: <002e01c3938a$724377e0$eaff58db@newpc>
Message-ID: <THU.16.OCT.2003.143035.0200.CLAUSH@MEK.DTU.DK>

Dear Doug,

I certainly respect yours and others inspections and knowledge on
specific combinations of fixed beds geometries and fuel.

I hope to be able to add more general knowledge on the processes inside
the particle (and actually I will only look at single particle behaviour
instead of beds for a start). By building models of the processes inside
single particles during conversion, it is my ambitious hope to be able
to identify which features (geometry, ash amount/species, pore
structures, temperature, reactions, stresses, vibration etc.) and
processes (fines generation, percolative and stress breakage, bulk
shrinking) are important to a biomass particles strength and breakage.

The ultimate goal is to improve the background for designing new
reactors (geometries and larger sizes) and fuel specification BEFORE
testing combinations of the two.

Of course such models must rely on empirical input from existing
experience like yours.

Using beech wood chips, we have observed particle size developments as
could be expected for surface breakage. By dissecting a fixed bed after
stopping gasification reactions with nitrogen looking at particle sizes
at different levels, we have seen gradual particle shrinkage accompanied
by a significant increase in monosized fines with high ash contents of
approximately 1 mm as we approach the grate.

Softwood and other biomasses may behave completely differently, as you
indicated.

Doug wrote:
> When ash forms on the surface of wood particles, it is a clear indication
> that the air velocity is too low, and if you observe the bed through one of
> the nozzles, you can see the surface blackened as the ash prevents the
> oxygen reacting with the surface carbon. Even when you have the velocity
> right to start with, if the gasification parameters are not correct, bed
> restrictions will change the velocity of the nozzle.

I am a bit puzzled by the above statement. It looks like you desire to
combust the char - not only the tars - with the air. I would think that
a protective ash layer on the char would help preserving them for later
gasification instead of combustion.
Also, ash have significant catalytic effects, which would be desirable
during gasification. Naturally, this is no good if temperature and
gasification agent cannot reach the char through the ash layer.

Doug wrote:
> There is also another dimension to consider, in that some tropical hard
> woods completely collapse at the end of the oxidation phase, where reduction
> begins. This completely blocks up the bed, and the gasifier behaves very
> badly. I would suggest that a study of those gasifiers supplied to projects
> in the Pacific,Asia, and South America during the 1970s and 80s of French,
> German and Dutch manufacture would be useful to your study.

This certainly could prove interesting. Do you have any names or
references?
Maybe it could be possible to harden such woods during pyrolysis (using
high temperatures with no oxygen) or pelletise the wood for better
stability?

Sincerely,
Claus Hindsgaul

From joflo at YIFAN.NET Thu Oct 16 14:36:16 2003
From: joflo at YIFAN.NET (Joel Florian)
Date: Tue Aug 10 18:24:31 2004
Subject: masticating harvester
In-Reply-To: <1066307434.936.89.camel@reber>
Message-ID: <THU.16.OCT.2003.103616.0800.JOFLO@YIFAN.NET>

Hello,

It is nice to see some good discussion on the list. I guess everyone has
been busy this summer.

I'm wondering about mechanized chip harvesting equipment. Ever since I
first found out about gasification and related technologies, I've dreamed
of one day having a machine that could mow down scrub forest, reduce the
bio mass into chips or small chunks, and collect it. Rather like a
combine harvester for wood or a huge riding lawn mower with a bagger.

My internet research tells me that I'm not the only one with a desire for
such a machine. It seems like Europe is a leader in this area with several
different machines designed for coppiced woodland. Unfortunately, every
account I have read has listed major problems or constraints with the
machines. one seems to be designed around two counter-rotating saw
blades. A few selected links follow.
http://btgs1.ct.utwente.nl/Scripts/eeci/showimage.pl?ID=I10390
http://www.treepower.org/harvesting.html
http://www.claas.com/produktseiten/produkte/special_products/uk_int/holzhaeckseltechnologie/index.php
http://www.norwich.net/~socnyrcd/willow2.html
http://www.treepower.org/harvesting/austoft.pdf
http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10440.html
http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10073.html

About 10 years ago, some Texas Aggies did an experiment with a flail-type
mulching head -- basically the hammermill (shaft and hammers) from a wood
hog mounted on the rear of a tractor. Pushing this spinning cutter head
against trees would grind into them, push them over, and then reduce the
remainder into shreddings and auger it into a
bin. www.woodycrops.org/mechconf/mclaughl.html (link may not work as
woodycrops.org seems to be having trouble -- I hope they get the domain up
soon as there seem to be many good links to the site)

Here in Alaska, at least, there are many needs for land clearing --
including power lines, telephone right of ways, and highways. The machine
of choice seems to be a skidder-mounted mulching head. Fecon seems to be
the industry leader with a horizontal drum rotating at several thousand rpm
and fixed, replaceable teeth. http://www.fecon.com/bullhog/ This mulching
head has many advantages over the Hydro-ax (basically a big lawn mower or
brush cutter) one of which is safety. Many of the land clearing contracts
require that the reduced bio mass be removed -- requiring a second
contractor to come in with loaders and dump trucks and scoop the material
off the ground and haul to a landfill. It would be nice to be able to
burn that waste material, but my experience with loader-scooped bio mass is
that it usually includes a lot of rocks and dirt that don't burn and really
mess up the inside of a gasifier or combustion chamber.

Any one have ideas or experience with modifying a fecon masticating head to
produce and collect hog-fuel? I suppose most gasifiers prefer chips or
chunks over hog-fuel -- is there a mechanized harvester for such? Also,
what is the best way to get the chips from the harvester to the
highway? Should the harvester process the biomass from tree to useable
chip in a self-contained unit, or should it just do primary reduction and
count on a secondary chipper, chunker, grinder, sizer, screen, or pelletizer.

I'll write about my ideas when I have more time. Right now I'm building a
chip storage shed and I need to get the concrete finished before it gets
too much colder.

Thanks in advance for your comments.

Joel Florian
Alaska

From LINVENT at AOL.COM Thu Oct 16 17:11:39 2003
From: LINVENT at AOL.COM (LINVENT@AOL.COM)
Date: Tue Aug 10 18:24:31 2004
Subject: masticating harvester
Message-ID: <THU.16.OCT.2003.171139.EDT.>

Several decades ago a local guy who was a big logger built a machine which
would cut down the trees, limb them, debark them and send them out the back.
Apparently they were built on what was then a Caterpillar D-9 tractor frame. The
interesting part of the story is that they worked well and one he put a large
chipper behind and took smaller trees and chipped them. Both were lost in
Arkansas swampland where they hit some quicksand like soil and sank. They were not
retreivable in spite of cranes other dozers and other equipment being brought
in to rescue them. To really do serious harvesting, this is the type of
equipment needed.

Leland T. Taylor
President
Thermogenics Inc.
7100-F 2nd St. NW Albuquerque, New Mexico USA 87107 Phone: 505-761-5633, fax:
341-0424, website: thermogenics.com.
In order to read the compressed files forwarded under AOL, it is necessary to
download Aladdin's freeware Unstuffit at
http://www.stuffit.com/expander/index.html

From psanders at ILSTU.EDU Thu Oct 16 17:55:31 2003
From: psanders at ILSTU.EDU (Paul S. Anderson)
Date: Tue Aug 10 18:24:31 2004
Subject: masticating harvester
In-Reply-To: <5.1.1.6.0.20031016093850.01b90708@yifan.net>
Message-ID: <THU.16.OCT.2003.165531.0500.PSANDERS@ILSTU.EDU>

Joel,

Thanks for your interesting message. The links you provided were very
informative (to this novice).

My work is with "micro-gasifiers" (like a residential stove) and I have
needs for "chunks" of biomass/sticks (not the shreaded type).

I look forward to further discussions on the list-serve.

Paul

At 10:36 AM 10/16/03 -0800, Joel Florian wrote:
>Hello,
>
>It is nice to see some good discussion on the list. I guess everyone has
>been busy this summer.
>
>I'm wondering about mechanized chip harvesting equipment. Ever since I
>first found out about gasification and related technologies, I've dreamed
>of one day having a machine that could mow down scrub forest, reduce the
>bio mass into chips or small chunks, and collect it. Rather like a
>combine harvester for wood or a huge riding lawn mower with a bagger.
>
>My internet research tells me that I'm not the only one with a desire for
>such a machine. It seems like Europe is a leader in this area with several
>different machines designed for coppiced woodland. Unfortunately, every
>account I have read has listed major problems or constraints with the
>machines. one seems to be designed around two counter-rotating saw
>blades. A few selected links follow.
>http://btgs1.ct.utwente.nl/Scripts/eeci/showimage.pl?ID=I10390
>http://www.treepower.org/harvesting.html
>http://www.claas.com/produktseiten/produkte/special_products/uk_int/holzhaeckseltechnologie/index.php
>http://www.norwich.net/~socnyrcd/willow2.html
>http://www.treepower.org/harvesting/austoft.pdf
>http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10440.html
>http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10073.html
>
>
>About 10 years ago, some Texas Aggies did an experiment with a flail-type
>mulching head -- basically the hammermill (shaft and hammers) from a wood
>hog mounted on the rear of a tractor. Pushing this spinning cutter head
>against trees would grind into them, push them over, and then reduce the
>remainder into shreddings and auger it into a
>bin. www.woodycrops.org/mechconf/mclaughl.html (link may not work as
>woodycrops.org seems to be having trouble -- I hope they get the domain up
>soon as there seem to be many good links to the site)
>
>Here in Alaska, at least, there are many needs for land clearing --
>including power lines, telephone right of ways, and highways. The machine
>of choice seems to be a skidder-mounted mulching head. Fecon seems to be
>the industry leader with a horizontal drum rotating at several thousand rpm
>and fixed, replaceable teeth. http://www.fecon.com/bullhog/ This mulching
>head has many advantages over the Hydro-ax (basically a big lawn mower or
>brush cutter) one of which is safety. Many of the land clearing contracts
>require that the reduced bio mass be removed -- requiring a second
>contractor to come in with loaders and dump trucks and scoop the material
>off the ground and haul to a landfill. It would be nice to be able to
>burn that waste material, but my experience with loader-scooped bio mass is
>that it usually includes a lot of rocks and dirt that don't burn and really
>mess up the inside of a gasifier or combustion chamber.
>
>Any one have ideas or experience with modifying a fecon masticating head to
>produce and collect hog-fuel? I suppose most gasifiers prefer chips or
>chunks over hog-fuel -- is there a mechanized harvester for such? Also,
>what is the best way to get the chips from the harvester to the
>highway? Should the harvester process the biomass from tree to useable
>chip in a self-contained unit, or should it just do primary reduction and
>count on a secondary chipper, chunker, grinder, sizer, screen, or pelletizer.
>
>I'll write about my ideas when I have more time. Right now I'm building a
>chip storage shed and I need to get the concrete finished before it gets
>too much colder.
>
>Thanks in advance for your comments.
>
>Joel Florian
>Alaska

Paul S. Anderson, Ph.D., Fulbright Prof. to Mozambique 8/99 - 7/00
Rotary University Teacher Grantee to Mozambique >10 mo of 2001-2003
Dept of Geography - Geology (Box 4400), Illinois State University
Normal, IL 61790-4400 Voice: 309-438-7360; FAX: 309-438-5310
E-mail: psanders@ilstu.edu - Internet items: www.ilstu.edu/~psanders

From Steve.Goldthorpe at XTRA.CO.NZ Thu Oct 16 19:12:52 2003
From: Steve.Goldthorpe at XTRA.CO.NZ (Steve Goldthorpe)
Date: Tue Aug 10 18:24:31 2004
Subject: masticating harvester
Message-ID: <FRI.17.OCT.2003.121252.1300.STEVE.GOLDTHORPE@XTRA.CO.NZ>

Friends,

Joel's description of a vision of an omnivorous masticating harvester
capable if cutting swathes through bushland and leaving nothing in its wake
makes me feel very uneasy from the point of view of sustainable utilisation
of the forestry resource. I accept that there is sometimes a specific need
for land clearing for a specific purpose, but, as a means of producing
biomass fuel, those instances should be the exception rather than the rule.

I believe that the general purpose biomass harvester needs to be more
selective than the omnivorous mulcher envisioned by Joel, in the same way
that the agricultural combined harvester is a sophisticated sorting machine.
Those little bits of leaf, twig, bark and soil make a poor fuel, but contain
essential nutrients that should wherever possible be left on the ground to
feed the next generation of trees.

I also note that shredded biomass may be OK for combustion systems, but
biomass gasifier are fussy eaters, which prefer their diet to be small woody
lumps with similar dimensions in all directions. If the biomass harvester
is to feed this higher value market then it must prepare an appropriate feed
for it.

In the context of rough forest scrub, or even plantation forestry, these
requirements place high demands on the ingenuity of the equipment designers,
but the long term pay back will be in the reputation of biomass harvesting
as the supplier of a viable sustainable energy resource.

If clearfelling and land clearing for bioenergy results in desertification,
soil erosion and loss of habitat and biodiversity, then the environmental
reputation of the biofuel industry will be no better than that of the fossil
fuel industry which we are aiming to displace.

Regards

Steve

Steve Goldthorpe Energy Analyst Limited
PO Box 96, Waipu 0254, New Zealand
and Waipu Wanderers Backpackers
25 St Mary's Road, Waipu, Northland
Phone/Fax (NZ) 09 432 0532
Mobile (NZ) 0274 849 764
Email Steve.Goldthorpe@xtra.co.nz
and Waipu.Wanderers@xtra.co.nz
----- Original Message -----
From: "Joel Florian" <joflo@YIFAN.NET>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Friday, October 17, 2003 7:36 AM
Subject: [GASL] masticating harvester

> Hello,
>
> It is nice to see some good discussion on the list. I guess everyone has
> been busy this summer.
>
> I'm wondering about mechanized chip harvesting equipment. Ever since I
> first found out about gasification and related technologies, I've dreamed
> of one day having a machine that could mow down scrub forest, reduce the
> bio mass into chips or small chunks, and collect it. Rather like a
> combine harvester for wood or a huge riding lawn mower with a bagger.
>
> My internet research tells me that I'm not the only one with a desire for
> such a machine. It seems like Europe is a leader in this area with
several
> different machines designed for coppiced woodland. Unfortunately, every
> account I have read has listed major problems or constraints with the
> machines. one seems to be designed around two counter-rotating saw
> blades. A few selected links follow.
> http://btgs1.ct.utwente.nl/Scripts/eeci/showimage.pl?ID=I10390
> http://www.treepower.org/harvesting.html
>
http://www.claas.com/produktseiten/produkte/special_products/uk_int/holzhaec
kseltechnologie/index.php
> http://www.norwich.net/~socnyrcd/willow2.html
> http://www.treepower.org/harvesting/austoft.pdf
> http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10440.html
> http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10073.html
>
>
> About 10 years ago, some Texas Aggies did an experiment with a flail-type
> mulching head -- basically the hammermill (shaft and hammers) from a wood
> hog mounted on the rear of a tractor. Pushing this spinning cutter head
> against trees would grind into them, push them over, and then reduce the
> remainder into shreddings and auger it into a
> bin. www.woodycrops.org/mechconf/mclaughl.html (link may not work as
> woodycrops.org seems to be having trouble -- I hope they get the domain up
> soon as there seem to be many good links to the site)
>
> Here in Alaska, at least, there are many needs for land clearing --
> including power lines, telephone right of ways, and highways. The machine
> of choice seems to be a skidder-mounted mulching head. Fecon seems to be
> the industry leader with a horizontal drum rotating at several thousand
rpm
> and fixed, replaceable teeth. http://www.fecon.com/bullhog/ This mulching
> head has many advantages over the Hydro-ax (basically a big lawn mower or
> brush cutter) one of which is safety. Many of the land clearing contracts
> require that the reduced bio mass be removed -- requiring a second
> contractor to come in with loaders and dump trucks and scoop the material
> off the ground and haul to a landfill. It would be nice to be able to
> burn that waste material, but my experience with loader-scooped bio mass
is
> that it usually includes a lot of rocks and dirt that don't burn and
really
> mess up the inside of a gasifier or combustion chamber.
>
> Any one have ideas or experience with modifying a fecon masticating head
to
> produce and collect hog-fuel? I suppose most gasifiers prefer chips or
> chunks over hog-fuel -- is there a mechanized harvester for such? Also,
> what is the best way to get the chips from the harvester to the
> highway? Should the harvester process the biomass from tree to useable
> chip in a self-contained unit, or should it just do primary reduction and
> count on a secondary chipper, chunker, grinder, sizer, screen, or
pelletizer.
>
> I'll write about my ideas when I have more time. Right now I'm building a
> chip storage shed and I need to get the concrete finished before it gets
> too much colder.
>
> Thanks in advance for your comments.
>
> Joel Florian
> Alaska
>

From LINVENT at AOL.COM Thu Oct 16 19:53:10 2003
From: LINVENT at AOL.COM (LINVENT@AOL.COM)
Date: Tue Aug 10 18:24:31 2004
Subject: masticating harvester
Message-ID: <THU.16.OCT.2003.195310.EDT.>

Dear Mr.Goldthorpe,
There are several issues which I disagree with. First of all, the
nutrients which are contained in biomass residues can contribute to the rhizosphere
nutritional system, but only after a sustained oxidation of the carbon by
organic degradation and this process takes up nutrients robbing them from the plant
system. Many coniferous plants are quite toxic to soil microflora with
turpenes and pinenes being fairly toxic to microorganisms used for plant feeding and
mineral conversion to plant available nutrients. They should be kept out of
the soil and not used as mulch or other soil amending actions contrary to many
practices currently in place.
Carbon containing plant mass requires a complex array of nutrients to
convert to usable nutrients. These include nitrogen, iron, manganese, copper,
zinc all of which ultimately become short in most permanent nutritional systems.
Ask any microbiologist what it takes to support organic consuming microflora.
Application of high organic matter to any plant nutritional system results in
immediate nitrogen depletion of the plant system.
Secondly, the gasifiers who are fuel limited referred to are mostly
downdraft and there are those out there who are not as fussy about the fuel they
use. The masticated mix will work in them fine.
My preference is to not put the organic matter back in the soil but to
apply nutrients which are needed to replace those removed by normal growth and
not broken down by the soil digestion of minerals. This is actually less
expensive than dealing with the biomass residue and the problems which it creates
from application back to the forest floor. It has a dramatic impact upon growth
and production rates in the soil. Even latteritic soils generated from mass
removal of trees in rain forests can be reclaimed with the proper program.
Application of organic matter to this soil complex makes it worse because of the
role calcium plays in the aluminosilicate complex.

From graeme at POWERLINK.CO.NZ Thu Oct 16 20:28:12 2003
From: graeme at POWERLINK.CO.NZ (Graeme Williams)
Date: Tue Aug 10 18:24:31 2004
Subject: The Role of the choke in downdraft gasification
Message-ID: <FRI.17.OCT.2003.132812.1300.GRAEME@POWERLINK.CO.NZ>

Dear Claus

It is very important to first establish what sort of gasification process
you are talking about, because some turn all the fuel into charcoal then
gas, and others make a surplus of charcoal. If you have a conventional
downdraught gasifier then the oxidation zone in front of the nozzles must
react with the carbon, and consume some of it, to produce the exothermic
heat required to create the incoming carbon and have sufficient left over to
drive the endothermic reaction of the reduction zone where the gas is
actually made. Certainly pyrolysis gases evolving from the distillation
zone combust as they pass through the oxidation zone, although heavy
hydrocarbons can channel down between the nozzles and escape cracking
because the bed temperatures are not hot enough. No doubt there can be many
variations of this theme, but in the end gasification is one of staged
reactions of distillation, carbonisation, oxidation, and reduction. Once
you understand and put into practice these principles, you can tell at a
glance how almost any process can work and from the temperature profiles,
tell what type of gas is being made.

On the subject of ash again, the last thing you want in a gas producer is
ash held in the fuel, because it will result in clinker, that is if you have
a true oxidation zone and not something suffering from starved air, which
seems to be a complete misunderstanding that has kept into the language of
this technology. The oxidation zone should be a blast furnace and will
smelt metal in its environment. I too have read that ash is a catalyst, but
goodness knows what for, because it has never enhanced any gas making that
I have experienced so far.

My suggestion for char studies would be to go for a conifer wood which has
very widespread application as fuel. It also has a structure which can make
it easier to identify the lines of fracture. I will have to get into my
files regarding the tropical fuel woods as there are over two thousand
identified in the region, and probably lots more in terms of individual
behaviour within the same species, much the same as eucalypts. I will send
this to you at a later date.

Kindest Regards
Doug Williams.

----- Original Message -----
From: "Claus Hindsgaul" <claush@MEK.DTU.DK>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Friday, October 17, 2003 1:30 AM
Subject: Re: [GASL] The Role of the choke in downdraft gasification

> Dear Doug,
>
> I certainly respect yours and others inspections and knowledge on
> specific combinations of fixed beds geometries and fuel.
>
> I hope to be able to add more general knowledge on the processes inside
> the particle (and actually I will only look at single particle behaviour
> instead of beds for a start). By building models of the processes inside
> single particles during conversion, it is my ambitious hope to be able
> to identify which features (geometry, ash amount/species, pore
> structures, temperature, reactions, stresses, vibration etc.) and
> processes (fines generation, percolative and stress breakage, bulk
> shrinking) are important to a biomass particles strength and breakage.
>
> The ultimate goal is to improve the background for designing new
> reactors (geometries and larger sizes) and fuel specification BEFORE
> testing combinations of the two.
>
> Of course such models must rely on empirical input from existing
> experience like yours.
>
> Using beech wood chips, we have observed particle size developments as
> could be expected for surface breakage. By dissecting a fixed bed after
> stopping gasification reactions with nitrogen looking at particle sizes
> at different levels, we have seen gradual particle shrinkage accompanied
> by a significant increase in monosized fines with high ash contents of
> approximately 1 mm as we approach the grate.
>
> Softwood and other biomasses may behave completely differently, as you
> indicated.
>
> Doug wrote:
> > When ash forms on the surface of wood particles, it is a clear
indication
> > that the air velocity is too low, and if you observe the bed through
one of
> > the nozzles, you can see the surface blackened as the ash prevents the
> > oxygen reacting with the surface carbon. Even when you have the
velocity
> > right to start with, if the gasification parameters are not correct, bed
> > restrictions will change the velocity of the nozzle.
>
> I am a bit puzzled by the above statement. It looks like you desire to
> combust the char - not only the tars - with the air. I would think that
> a protective ash layer on the char would help preserving them for later
> gasification instead of combustion.
> Also, ash have significant catalytic effects, which would be desirable
> during gasification. Naturally, this is no good if temperature and
> gasification agent cannot reach the char through the ash layer.
>
> Doug wrote:
> > There is also another dimension to consider, in that some tropical hard
> > woods completely collapse at the end of the oxidation phase, where
reduction
> > begins. This completely blocks up the bed, and the gasifier behaves
very
> > badly. I would suggest that a study of those gasifiers supplied to
projects
> > in the Pacific,Asia, and South America during the 1970s and 80s of
French,
> > German and Dutch manufacture would be useful to your study.
>
> This certainly could prove interesting. Do you have any names or
> references?
> Maybe it could be possible to harden such woods during pyrolysis (using
> high temperatures with no oxygen) or pelletise the wood for better
> stability?
>
> Sincerely,
> Claus Hindsgaul
>

From claush at MEK.DTU.DK Fri Oct 17 05:43:05 2003
From: claush at MEK.DTU.DK (Claus Hindsgaul)
Date: Tue Aug 10 18:24:31 2004
Subject: Gasification subprocesses and ash
In-Reply-To: <003601c39445$8f249720$1aff58db@newpc>
Message-ID: <FRI.17.OCT.2003.114305.0200.CLAUSH@MEK.DTU.DK>

Dear Doug,

The two-stage process is a good illustration of the subprocesses you
mention, since they are kept physically apart:

* drying and pyrolysis in one reactor ("distillation" resulting in
"carbonisation")
* oxidation of tars for fractions of a second (and thus no or
vanishing amounts of char is oxidised)
* gasification in another reactor ("reduction")

It seems to be a good basis for studying the processes one at a time.

The reason I was puzzled by you mentioning the combustion of char is
that it is not nessecary to combust any char (at least not in our
gasifier using wood) to gain the required heat for the endothermic
gasification. Other processes may need to combust a fraction of the
char.

> smelt metal in its environment. I too have read that ash is a catalyst, but
> goodness knows what for, because it has never enhanced any gas making that
> I have experienced so far.

>From a chemical point of view, ash should be expected to have some kind
of local catalytic effect. Of course it can at the same time be a
diffusion and heat obstruction. My humble hope is that a better
understanding of the way ash manipulate biomass particles during
conversion may help us gaining from its presence.

Claus Hindsgaul

From ventfory at IAFRICA.COM Fri Oct 17 06:59:59 2003
From: ventfory at IAFRICA.COM (Kobus)
Date: Tue Aug 10 18:24:31 2004
Subject: masticating harvester
Message-ID: <FRI.17.OCT.2003.125959.0200.VENTFORY@IAFRICA.COM>

Steve and others

Finally a forestry subject. Mechanization is great, unless it compacts or
disturbs the forest floor. The problem with machines are not that they
totally remove all ground vegetation, as at least 30% of the crop is
returned as waste to the forest floor, but rather it is their heavy bulks
that leads to
compaction which can lead to erosion. Many technological advances have been
made to lessen the impact of machinery on the forest floor, such as
increasing the surface area of the wheels/tracks impacting the ground, to
spread the load. Felling methods have also been developed whereby trees are
directional felled towards designated skidding paths, where the emphasis is
on winching in trees towards the machine as opposed to driving up to each
tree. With traditional chainsaw harvesting (low compaction) this
environmentally friendly practice is often overshadowed by the machined
extraction (skidding) of one or more trees at a time. Here the wheel
compaction and wheel slip combined with the scraping of the tree on the
forest floor impacts negatively on the site. Ironically it is the more
advanced harvester-forwarder like machines that seems to cause less forest
floor damage, with the added advantage that the bark is stripped off infield
as opposed to being stripped at roadside.

Personally I would rather like to see a balance developing between
protecting the environment (and forest floor) and unlocking unutilized
energy from commercial
forestry- and wood processing sector waste (twigs, leaves, bark and
sawdust). In S.Africa 3.77 million tons per dry weight of waste is
generated annually from the forestry and wood processing industry (1979!!).

Regards

Kobus
Venter Forestry Services
South Africa

----- Original Message -----
From: Steve Goldthorpe <Steve.Goldthorpe@XTRA.CO.NZ>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: 17 October 2003 01:12
Subject: Re: [GASL] masticating harvester

> Friends,
>
> Joel's description of a vision of an omnivorous masticating harvester
> capable if cutting swathes through bushland and leaving nothing in its
wake
> makes me feel very uneasy from the point of view of sustainable
utilisation
> of the forestry resource. I accept that there is sometimes a specific need
> for land clearing for a specific purpose, but, as a means of producing
> biomass fuel, those instances should be the exception rather than the
rule.
>
> I believe that the general purpose biomass harvester needs to be more
> selective than the omnivorous mulcher envisioned by Joel, in the same way
> that the agricultural combined harvester is a sophisticated sorting
machine.
> Those little bits of leaf, twig, bark and soil make a poor fuel, but
contain
> essential nutrients that should wherever possible be left on the ground to
> feed the next generation of trees.
>
> I also note that shredded biomass may be OK for combustion systems, but
> biomass gasifier are fussy eaters, which prefer their diet to be small
woody
> lumps with similar dimensions in all directions. If the biomass harvester
> is to feed this higher value market then it must prepare an appropriate
feed
> for it.
>
> In the context of rough forest scrub, or even plantation forestry, these
> requirements place high demands on the ingenuity of the equipment
designers,
> but the long term pay back will be in the reputation of biomass harvesting
> as the supplier of a viable sustainable energy resource.
>
> If clearfelling and land clearing for bioenergy results in
desertification,
> soil erosion and loss of habitat and biodiversity, then the environmental
> reputation of the biofuel industry will be no better than that of the
fossil
> fuel industry which we are aiming to displace.
>
> Regards
>
> Steve
>
> Steve Goldthorpe Energy Analyst Limited
> PO Box 96, Waipu 0254, New Zealand
> and Waipu Wanderers Backpackers
> 25 St Mary's Road, Waipu, Northland
> Phone/Fax (NZ) 09 432 0532
> Mobile (NZ) 0274 849 764
> Email Steve.Goldthorpe@xtra.co.nz
> and Waipu.Wanderers@xtra.co.nz
> ----- Original Message -----
> From: "Joel Florian" <joflo@YIFAN.NET>
> To: <GASIFICATION@LISTSERV.REPP.ORG>
> Sent: Friday, October 17, 2003 7:36 AM
> Subject: [GASL] masticating harvester
>
>
> > Hello,
> >
> > It is nice to see some good discussion on the list. I guess everyone
has
> > been busy this summer.
> >
> > I'm wondering about mechanized chip harvesting equipment. Ever since I
> > first found out about gasification and related technologies, I've
dreamed
> > of one day having a machine that could mow down scrub forest, reduce the
> > bio mass into chips or small chunks, and collect it. Rather like a
> > combine harvester for wood or a huge riding lawn mower with a bagger.
> >
> > My internet research tells me that I'm not the only one with a desire
for
> > such a machine. It seems like Europe is a leader in this area with
> several
> > different machines designed for coppiced woodland. Unfortunately, every
> > account I have read has listed major problems or constraints with the
> > machines. one seems to be designed around two counter-rotating saw
> > blades. A few selected links follow.
> > http://btgs1.ct.utwente.nl/Scripts/eeci/showimage.pl?ID=I10390
> > http://www.treepower.org/harvesting.html
> >
>
http://www.claas.com/produktseiten/produkte/special_products/uk_int/holzhaec
> kseltechnologie/index.php
> > http://www.norwich.net/~socnyrcd/willow2.html
> > http://www.treepower.org/harvesting/austoft.pdf
> > http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10440.html
> > http://btgs1.ct.utwente.nl/eeci/archive/biobase/B10073.html
> >
> >
> > About 10 years ago, some Texas Aggies did an experiment with a
flail-type
> > mulching head -- basically the hammermill (shaft and hammers) from a
wood
> > hog mounted on the rear of a tractor. Pushing this spinning cutter head
> > against trees would grind into them, push them over, and then reduce the
> > remainder into shreddings and auger it into a
> > bin. www.woodycrops.org/mechconf/mclaughl.html (link may not work as
> > woodycrops.org seems to be having trouble -- I hope they get the domain
up
> > soon as there seem to be many good links to the site)
> >
> > Here in Alaska, at least, there are many needs for land clearing --
> > including power lines, telephone right of ways, and highways. The
machine
> > of choice seems to be a skidder-mounted mulching head. Fecon seems to
be
> > the industry leader with a horizontal drum rotating at several thousand
> rpm
> > and fixed, replaceable teeth. http://www.fecon.com/bullhog/ This
mulching
> > head has many advantages over the Hydro-ax (basically a big lawn mower
or
> > brush cutter) one of which is safety. Many of the land clearing
contracts
> > require that the reduced bio mass be removed -- requiring a second
> > contractor to come in with loaders and dump trucks and scoop the
material
> > off the ground and haul to a landfill. It would be nice to be able to
> > burn that waste material, but my experience with loader-scooped bio mass
> is
> > that it usually includes a lot of rocks and dirt that don't burn and
> really
> > mess up the inside of a gasifier or combustion chamber.
> >
> > Any one have ideas or experience with modifying a fecon masticating head
> to
> > produce and collect hog-fuel? I suppose most gasifiers prefer chips or
> > chunks over hog-fuel -- is there a mechanized harvester for such? Also,
> > what is the best way to get the chips from the harvester to the
> > highway? Should the harvester process the biomass from tree to useable
> > chip in a self-contained unit, or should it just do primary reduction
and
> > count on a secondary chipper, chunker, grinder, sizer, screen, or
> pelletizer.
> >
> > I'll write about my ideas when I have more time. Right now I'm building
a
> > chip storage shed and I need to get the concrete finished before it gets
> > too much colder.
> >
> > Thanks in advance for your comments.
> >
> > Joel Florian
> > Alaska
> >

From tombreed at COMCAST.NET Fri Oct 17 01:12:40 2003
From: tombreed at COMCAST.NET (tombreed)
Date: Tue Aug 10 18:24:31 2004
Subject: Relative Advantages of Imbert and Stratified Downdraft gasifiers
Message-ID: <THU.16.OCT.2003.231240.0600.TOMBREED@COMCAST.NET>

Dear Doug and Claus;

The principle weakness of our Stratified Downdraft Gasifier is that the
pyrolysis zone may generate more char than the char gasification zone
consumes. This can be corrected by monitoring the position of the char zone
with a TC and adding addition air to the char zone to balance the char
inventory and for final tar cleanup. (Typically <200 ppm tar in raw gas.)
This is the approach of the low tar gasifiers out of Prof. Makuna's PGC lab
in Bangalore, India and our Biomax gasifiers (www.gocpc.com). The advantage
is very low tar in the raw gas and an open top for continuous feeding.

This problem is automatically corrected in the Imbert gasifiers by placement
of the nozzles above the pyrolysis and char gasification zones. If too much
char is produced (low throughput), the char rises to the level of the
nozzles and is also consumed. If too little char is produced, all the
incoming air goes to pyrolysis and making more char. The disadvantages are
that some of the feed slips between the nozzles and is only pyrolysed (not
flaming-pyrolysed) resulting in more tar ~ 1000 ppm at the sweet spot.

Comments?

Yours truly,

Dr. Thomas Reed

tombreed@comcast.com
www.woodgas.com
----- Original Message -----
From: "Claus Hindsgaul" <claush@MEK.DTU.DK>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Thursday, October 16, 2003 6:30 AM
Subject: Re: [GASL] The Role of the choke in downdraft gasification

From ventfory at IAFRICA.COM Fri Oct 17 09:27:33 2003
From: ventfory at IAFRICA.COM (Kobus)
Date: Tue Aug 10 18:24:31 2004
Subject: Briquette gasifier stove - photos
Message-ID: <FRI.17.OCT.2003.152733.0200.VENTFORY@IAFRICA.COM>

Hi all,

We now have photos of our first prototype gasifier stove and also include the information displayed at the booth in Boulder.

The report can be seen on the stove page or go to
http://www.repp.org/discussiongroups/resources/stoves/Kobus/gasbriqstove.htm

Unfortunately it did not gasify properly at the conference and was sidelined due to a problem with the briquettes (Richard packed coffee ground instead of coffee husk briquettes!) and other minor design faults. Its back in Uganda now, undergoing some more testing by Richard. Our next prototype will be of a similar design, but this time with the emphasis on cost-effective materials and incorporating improved manufacturing and assembly techniques, with the emphasis on D.I Y. Feedback from the users will also determine the final shape it is to take over the next couple of months. We will also be altering the briquette dimensions (volume) to increase power output and will focus on perfecting a pot shield.

We promise to keep all informed.

Regards

Kobus Venter
and Richard Stanley

From tombreed at COMCAST.NET Fri Oct 17 01:47:12 2003
From: tombreed at COMCAST.NET (tombreed)
Date: Tue Aug 10 18:24:31 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
Message-ID: <THU.16.OCT.2003.234712.0600.TOMBREED@COMCAST.NET>

Dear Doug and all:

There has been more science/art discussion on downdraft gasifiers here in
the last few weeks than in the previous many years! Keep it up.

I respectfully beg to disagree in part with Doug, but would welcome his
comments.

In our stratified downdraft gasifiers the air only comes through many inches
of fuel bed until it arrives at the flaming pyrolysis zone, where the air
reacts with the burning biomass particles, destroying most of the tar and
creating the char. At the end of this zone the oxygen is gone and the
gases are largely CO, CO2, H2 and H2O at 1200 to 1500 C. (Hence the name
"Tar burning, char making" for downdraft and top lit updraft gasifiers (aka
inverted downdraft) and "char burning tar making" for conventional updraft
gasifiers.) THEN these very hot gases pass immediately through the
incandescent char section below and are further reduced and cooled in
producing more gas and destroying more tars. There is no way for the air to
reach the char since it has to pass through the pyrolysis zone.

In the Imbert (nozzle) style gasifier air comes in and meets partially
unburned biomass and/or char, depending on gas throughput, moisture level
etc. Amazing that it is as self-adjusting as it is, but typically it
produces more tars. I believe Doug's explanation below stresses radiant
roasting of the incoming biomass by burning char only.

Doug, have you ever measured the tar levels in your raw gas?

Comments,

Onward... TOM REED

----- Original Message -----
From: "Graeme Williams" <graeme@POWERLINK.CO.NZ>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Wednesday, October 15, 2003 7:13 PM
Subject: Re: [GASL] Woodchip, Co-current Downdraft, Restricted Throat,
Questions

> Dear Greg,
>
> Having spent 28 years working with downdraught throated gasifiers, the
> following may assist you to understand slightly better the basic
principles
> of their design.
>
> 1: In normal operation the gasifier is filled with charcoal to above the
> nozzles where the air enters the bed. The raw wood sits on top of the
> charcoal.
>
> 2: On ignition the char in front and below the nozzles becomes
> incandescent radiating heat upwards into the descending fuel to produce
the
> charcoal. As the oxygen is consumed as it passes down through the bed, the
> flowing gas reaches an equilibrium point where there is a minimum of
oxygen
> and a maximum of CO2. At this point combustion ceases in the absence of
> oxygen, and the throat is located at this point, which is the beginning of
> the reduction zone where the gas is actually made. Pyrolisis gases that
> evolve above the oxidation zone, should be consumed in the presence of
> oxygen and should not survive past the throat which also acts as a high
> temperature cracking zone for the heavier hydrocarbons that can slip down
> between nozzles etc.
>
> 3: The char in the reduction zone reacts with the incandescent CO2 which
> should be within a temperature range of 12-1500 degreesC, and shrinks as
it
> gives up carbon molecules to the CO2 to become CO. Steam is cracked at
the
> throat into hydrogen and this joins the CO to become the fuel gas. The
> continuous shrinkage and consumption of the char from the outlet grate up
> through the throat and oxidation zone, enables the flow of fuel to take
> place almost under the influence of gravity. Incorrectly designed
gasifiers
> and\or incorrect fuel do create problems and is the reason for many
failures
> over the years.
>
> The above basic description can be found in literature, but to copy
> published designs in the hope of getting a working gasifier proves fatal
to
> those who try it. The use of these gasifiers in WW2 for mobile
application
> masked a lot of problems, and there are a lot of inconsistencies in the
> dimensions when the technology is attempted to be used for stationary
> application. If it were just a case of copying the existing designs and
> they worked, there would be no need for this discussion group or companies
> still trying to evolve reliable commercial equipment.
>
> Hope this helps a little.
>
> Regards
> Doug Williams.
> Fluidyne Gasification.
>

From a31ford at INETLINK.CA Sat Oct 18 10:33:01 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:31 2004
Subject: Virtual Throat, Imbert Gasifier
In-Reply-To: <00d201c39470$350da300$b5affd0c@TOMBREED>
Message-ID: <SAT.18.OCT.2003.093301.0500.A31FORD@INETLINK.CA>

Greetings Tom & all,

Why Certainly, I will keep you posted, as your input (also pages, book &
web) have been most of the starting points of my getting involved, in the
first place :)

The Taper/Choke thing really has me going, as it has been the problem point
from the start. The Washer sounds much cheaper at this point, so I'll try
that first.

Model #1 (all are smaller models "desktop size" so to speak) literally did
a melt down (that was 2-1/2 years ago). #2, was good in gas production, but
would plug up in around 3 hrs. #3 would go 10-12 hrs. before plugging (but
gas qty. & content was poor), #4 (Initially was about the same as #3) is the
"baby" it runs for 4-5 days before plugging, not bad in qty/quality, but
still packs it in eventually.

All have been designed around "White Aspen" wood chips (as this is what we
have unlimited access to) I built a "Cleaner/Sorter" based on the workings
of a concrete truck "mixer drum", and it removes fines & dirt quite well,
sorts the stuff, ejects what is too big for the feed auger, and actually
helps in removing M/C to below the 17% mark, using expanded wire mesh (the
stuff used for industrial catwalks).

P.S. Don't know if I told you, but this is simply a "heating system" for our
home, garage, & workshop, (Outdoor boiler, as the locals say). I'm the type
of person that would do it differently, simply to do so (within finances).
I'm tired of paying huge sums of money to simply "keep warm" (Manitoba,
Canada) and the "green thing" does concern me also. NO lab, support or
grants from others involved on this. I guess what I'm saying is, I think on
a different level (being up or down) from the "Norm." When I decide to do
something, I put all my efforts into it, and do it to the best of my
abilities/resources.

Greg Manning
Brandon, Manitoba, Canada

-----Original Message-----
From: tombreed [mailto:tombreed@comcast.net]
Sent: Friday, October 17, 2003 12:34 AM
To: a31ford
Subject: Re: [GASL] Virtual Throat, Imbert Gasifier

Dear Greg:

Before machining a taper, you might consider making a virtual taper simply
by adding a replaceable washer with the appropriate ID on the bottom of a
straight pipe. The downcoming char then forms an angle of repose taper,
leaving some char along the wall acting as excellent insulation. You could
then easily change the washer to try various degrees of choking for
different fuels.

Please keep me posted on your progress....

TOM REED

Yours truly,

Dr. Thomas Reed
tombreed@comcast.com
www.woodgas.com
----- Original Message -----
From: "a31ford" <a31ford@INETLINK.CA>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Wednesday, October 15, 2003 7:41 PM
Subject: [GASL] Virtual Throat, Imbert Gasifier

> Good Day Tom, Doug, Graeme, and all,
>
> I have been thinking of Tom's "Virtual Throat" and have realized that it
is
> the true, one & only stumbling block that I must overcome in my still
design
> phase Gasifier. This has been 3 years in the making, and with the models I
> have tried, I know enough, that, I know nothing in the grand scheme, on
> things of this nature.
>
> With that said, I am doing the following to model #4:
>
> 1) Replacing the existing throat with a 4" x 9" long, thick wall pipe
(would
> use 304SS but this is testing only) the local "guy with a lathe" said he
> could cut internal "cross hatch" in it (like what is on the handle of a
> ratchet wrench) in a thin to thick pattern (thick being at the lower end
of
> the throat) The feedstock I am currently using for testing is roughly 3/4"
x
> 1/4" aspen chips, sorted & cleaned(after preheat, 10-17%MC) no leaf or
> "sawdust" content.
>
> 2) The existing Model #4 will have no other changes, and has been running
> the same type of feedstock through all tests (best model so far, but alas
> far from stable in the bottom end).
>
>
> 3) as Doug said, "copying an existing unit" is sure to fail (I agree), but
> being a lone person with limited funds, I am simply trying to combine what
I
> feel is the "best" of what I have seen, read, or heard, and basing that on
a
> known working unit for reference.
>
> Will keep all informed.
>
>
> Greg Manning,
> Brandon, Manitoba, Canada
>

From graeme at POWERLINK.CO.NZ Sun Oct 19 22:49:55 2003
From: graeme at POWERLINK.CO.NZ (Graeme Williams)
Date: Tue Aug 10 18:24:31 2004
Subject: Woodchip, Co-current Downdraft, Restricted Throat, Questions
Message-ID: <MON.20.OCT.2003.154955.1300.GRAEME@POWERLINK.CO.NZ>

Dear Tom

On Friday the 17th you wrote,

> In the Imbert (nozzle) style gasifier air comes in and meets partially
> unburned biomass and/or char, depending on gas throughput, moisture level
> etc. Amazing that it is as self-adjusting as it is, but typically it
> produces more tars. I believe Doug's explanation below stresses radiant
> roasting of the incoming biomass by burning char only.

followed by this comment on the 18th

End of quote.

Tom,
In stating your belief on how these gasifiers work which after all is the
result of experience, its clear that whatever tests you did in the past with
an undefined specification of throated downdraught gasifier of the Imbert
style, you have obtained a faulty understanding of how these gasifiers work.
It is unfortunate that without proper operating instructions, it is
difficult to know how a gasifier is supposed to work correctly, and all
manner of impressions are created as a result of incorrect operation.

You will no doubt remember the second international gasification conference
in Bandung Indonesia, in March 1985. If you still have the conference
papers from that time, you will see how institutional gasification research
was completely wasted because of the lack of understanding of how
downdraught gasifiers worked, hence the presence of tar and why every one
had to measure it.

I would also point out that until the Bandung conference, Jack and I didn't
know you had to measure the tar in gas for engine application. It is
inconceivable that condensing tar is even considered as appropriate for
engines., and no measurement guarantees any process as reliable until it is
put to work doing the job it is meant for. The thought of tar in the gas is
not consistent with the requirement of engines, and Listers recognised this
as an engine supplier. By the time we had completed 5000 generating hours
with their engines, they were only too happy to supply us with a letter
stating they would maintain the warranty of their engines, but only with
Fluidyne gasification. This was in 1986 and there never has been a need
since to prove the tar levels, when we supply to any engine project. The
only time that tar becomes an issue is when there is a change of fuel or
fuel size, or when the operator fails to meet the obligations of required
maintenance and cleanouts etc. Does any other manufacture or research
institute have such an endorsement from an engine manufacturer?

The last time this issue was raised on this list, I posted some photographs
on the Fluidyne Archive www.fluidynenz.250x.com showing how wood turns to
charcoal above the nozzles in this process, and then proceeds to break down
through the oxidation zone. It doesn't roast the wood except in a loose
description of carbonisation and raw wood should never be present at the
level of incoming air of an oxidation zone. Thanks to the early work of
Jack Humphries, the original owner of Fluidyne, his description of how this
process works has been dug out, and added to the drawing, also original,
of the chemical changes, to the Fluidyne archive in How Gas is Made.

As you can see, I am happy to describe in words how downdraught gasification
works If my opinion on how it works isn't time tested enough, by proof of
existence and demonstration, then I really don't know how anyone can be
convinced that I don't know what I am talking about. I don't hide behind
chemical equations, which when measured only record the presence of the
phenomena existing at the time, which is why the making of producer gas
without tar, is a mystery to many.

In response to your question of have we tested our gas for tar levels, the
answer is no. The only technical question I have asked of this list, is
how do you measure tar levels that do not condense in an engine manifold
vacuum situation. More the question of why should you need to measure it
when it doesn't exist in a way that bothers the engine.

The latest tests of our gas in Canada has produced the following result, 25%
CO, 21%H2, 3%CH4, 2%CO2, 49%N2 The calorific value was determined to be
225btu/ft. The tar levels were not part of the test programme. As you can
see, the quality of the gas is coming up, and is the highest we have ever
recorded. It is the result of pushing the boundaries of throated
multi-nozzle downdraught gasifiers to a new limit, and in the coming months,
be put to work as part of a commercial activity. That for the moment is all
I can say about this private commercial venture, other than the engine loves
this gas.

My time is extremely limited, so I hope the understanding of downdraught
gasifiers is now clarified, even if their design is a mystery!!

We are all, I would hope, trying to move our various forms of gasification
forward into a sustainable biomass energy future. I sincerely believe this
has to be done irrespective of the difficulties we face.

Regards
Doug Williams.
Fluidyne Gasification.

From a31ford at INETLINK.CA Mon Oct 20 20:36:56 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:31 2004
Subject: Virtual Throat, Imbert Gasifier
In-Reply-To: <MBBBKLLLDJCJHMJBFCDECEGDCDAA.contacto@calipso.com.co>
Message-ID: <MON.20.OCT.2003.193656.0500.A31FORD@INETLINK.CA>

Luis,

I Will do so, as I am all for the "Share the Knowledge" approach, what is
good for my brain is good for others too :)

All ready thought of "If I ever get it running right (the gasifier)", that I
would look into a cooling system (like how a fridge in a camper runs on
propane, to cool the contents of the fridge), that one took me years to find
out/figure out, when I was a kid. (44 now).

Go figure, cool a home, (in the hot season) using a gasifier...... ;)

Greg Manning,
Brandon, Manitoba, Canada

-----Original Message-----
From: Contactos Mundiales [mailto:contacto@calipso.com.co]
Sent: Monday, October 20, 2003 7:08 AM
To: a31ford
Subject: RE: [GASL] Virtual Throat, Imbert Gasifier

Mr. Geg Manning
Canada

Dear Greg:

This is only to let you know that I appreciate your contribution and
look forward to future reports. Living in the Tropics do not require to
spend on warming, however, all of us would enjoy cooler homes, offices and
workplaces. Perhaps your ideas can be put to work for indoor climatic
control.

Please, keep up with your good work.

Kindest regards,

Luis R. Calzadilla
Cali, Colombia
contacto@calipso.com.co

From ventfory at IAFRICA.COM Tue Oct 21 07:02:28 2003
From: ventfory at IAFRICA.COM (Kobus)
Date: Tue Aug 10 18:24:31 2004
Subject: Briquette gasifier stove - photos
Message-ID: <TUE.21.OCT.2003.130228.0200.VENTFORY@IAFRICA.COM>

Hi Thomas,

I used the following formula:

Efficiency at high Power (%) =

(Initial mass of water X spec. heat of water (4.2kJ/kg.K)

times (x):

(Boiling temp. of water (K) - Initial temp. of water (K))

plus (+):

(Mass of evaporated water X Latent heat of water (2257 kJ/kg)

Answer divided by (/):

Mass of fuel used during high power (kg) X Calorific value of the fuel
(kJ/kg)

I used these recordings:

Type of pot: Stainless steel (0.5mm thick)
Time water (1 Litre) put on: 2nd minute
Time water boiled: 7th minute
Time taken to come to boil: 5 minutes
Initial temperature of water: 20?C
Time water stopped boiling rapidly: 36th minute
Time on high power: 34 minutes
Mass of fuel used during high power: 125 grams
Mass of water boiled on high power: 220 grams

In subsequent testing I achieved similar efficiencies by keeping the space
between the pot and top of the combustion chamber approximately 2 cm. I
think better efficiencies can be obtained by reducing it even further,
perhaps down to 1 cm.

Feel free to scrutinize our report. We have had very little feedback from
the gas and stove list thus far and would welcome any comments.

Here is the shortcut (note that it is not the same one you clicked on
earlier.)
http://www.repp.org/discussiongroups/resources/stoves/Stanley/BriqGassstove.htm

Best regards

Kobus

----- Original Message -----
From: Thomas Koch <Tk@tke.dk>
To: Kobus <ventfory@IAFRICA.COM>
Sent: 21 October 2003 08:58
Subject: Re: [GASL] Briquette gasifier stove - photos

Hi Kobus

I had a look at the lilnk below.

Just one question. How do you define your 35,2 % efficiency?

Best regards

Thomas Koch
----- Original Message -----
From: "Kobus" <ventfory@IAFRICA.COM>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Friday, October 17, 2003 3:27 PM
Subject: [GASL] Briquette gasifier stove - photos

Hi all,

We now have photos of our first prototype gasifier stove and also include
the information displayed at the booth in Boulder.

The report can be seen on the stove page or go to
http://www.repp.org/discussiongroups/resources/stoves/Kobus/gasbriqstove.htm

Unfortunately it did not gasify properly at the conference and was sidelined
due to a problem with the briquettes (Richard packed coffee ground instead
of coffee husk briquettes!) and other minor design faults. Its back in
Uganda now, undergoing some more testing by Richard. Our next prototype
will be of a similar design, but this time with the emphasis on
cost-effective materials and incorporating improved manufacturing and
assembly techniques, with the emphasis on D.I Y. Feedback from the users
will also determine the final shape it is to take over the next couple of
months. We will also be altering the briquette dimensions (volume) to
increase power output and will focus on perfecting a pot shield.

We promise to keep all informed.

Regards

Kobus Venter
and Richard Stanley

From a31ford at INETLINK.CA Tue Oct 21 21:52:21 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:31 2004
Subject: Virtual Throat, Imbert Gasifier
In-Reply-To: <4.3.1.2.20031021075343.01f37a10@mail.ilstu.edu>
Message-ID: <TUE.21.OCT.2003.205221.0500.A31FORD@INETLINK.CA>

Paul,

At this point it is only an idea, based on the heating value (your item 1),
that would be required to run an ammonia based cooling system (as I said,
like a propane driven fridge in an RV).

What values they would be, I have no idea, just the basics for now. It is
way down the list of things on the "to do list" (3-4 years, on mine !).

Greg

-----Original Message-----
From: Paul S. Anderson [mailto:psanders@ilstu.edu]
Sent: Tuesday, October 21, 2003 7:59 AM
To: a31ford
Subject: Re: [GASL] Virtual Throat, Imbert Gasifier

Greg,

To run the "cooling system" that you envision, do you want
1. the heat from the gases, or
2. the gases with specific characteristics that you then need to burn in
some specific way or device (like in an IC engine.) to get mechanical or
electrical power??

And how much of the gasifier output (specify if to be heat or gases to
burn) do you need?

Paul

At 07:36 PM 10/20/03 -0500, you wrote:
>Luis,
>
>I Will do so, as I am all for the "Share the Knowledge" approach, what is
>good for my brain is good for others too :)
>
>All ready thought of "If I ever get it running right (the gasifier)", that
I
>would look into a cooling system (like how a fridge in a camper runs on
>propane, to cool the contents of the fridge), that one took me years to
find
>out/figure out, when I was a kid. (44 now).
>
>Go figure, cool a home, (in the hot season) using a gasifier...... ;)
>
>Greg Manning,
>Brandon, Manitoba, Canada
>
>-----Original Message-----
>From: Contactos Mundiales [mailto:contacto@calipso.com.co]
>Sent: Monday, October 20, 2003 7:08 AM
>To: a31ford
>Subject: RE: [GASL] Virtual Throat, Imbert Gasifier
>
>
>
>Mr. Geg Manning
>Canada
>
>Dear Greg:
>
>This is only to let you know that I appreciate your contribution and
>look forward to future reports. Living in the Tropics do not require to
>spend on warming, however, all of us would enjoy cooler homes, offices and
>workplaces. Perhaps your ideas can be put to work for indoor climatic
>control.
>
>Please, keep up with your good work.
>
>Kindest regards,
>
>Luis R. Calzadilla
>Cali, Colombia
>contacto@calipso.com.co

From krishnakumar_07 at YAHOO.CO.UK Thu Oct 23 02:41:28 2003
From: krishnakumar_07 at YAHOO.CO.UK (=?iso-8859-1?q?krishna=20kumar?=)
Date: Tue Aug 10 18:24:31 2004
Subject: Briquette gasifier stove - photos
In-Reply-To: <006001c397c2$eb1cf920$2e271ec4@kobus>
Message-ID: <THU.23.OCT.2003.074128.0100.KRISHNAKUMAR07@YAHOO.CO.UK>

sir,
i have seen the photos of your model it is very
much intresting.i would like to know some details on
this:
1. provision for grate removal of ash.
2. how would you control the primary air supply
3. what is the total volume of the fuel storage
4. what is the specific gasification rate
5. how much amount of fuel required per hour
6. what is the specification of the system
7. what is the density of the fuel being used

--- Kobus <ventfory@IAFRICA.COM> wrote: > Hi Thomas,
>
> I used the following formula:
>
> Efficiency at high Power (%) =
>
> (Initial mass of water X spec. heat of water
> (4.2kJ/kg.K)
>
> times (x):
>
> (Boiling temp. of water (K) - Initial temp. of
> water (K))
>
> plus (+):
>
> (Mass of evaporated water X Latent heat of water
> (2257 kJ/kg)
>
> Answer divided by (/):
>
> Mass of fuel used during high power (kg) X Calorific
> value of the fuel
> (kJ/kg)
>
> I used these recordings:
>
> Type of pot: Stainless steel (0.5mm thick)
> Time water (1 Litre) put on: 2nd minute
> Time water boiled: 7th minute
> Time taken to come to boil: 5 minutes
> Initial temperature of water: 20?C
> Time water stopped boiling rapidly: 36th minute
> Time on high power: 34 minutes
> Mass of fuel used during high power: 125 grams
> Mass of water boiled on high power: 220 grams
>
> In subsequent testing I achieved similar
> efficiencies by keeping the space
> between the pot and top of the combustion chamber
> approximately 2 cm. I
> think better efficiencies can be obtained by
> reducing it even further,
> perhaps down to 1 cm.
>
> Feel free to scrutinize our report. We have had
> very little feedback from
> the gas and stove list thus far and would welcome
> any comments.
>
> Here is the shortcut (note that it is not the same
> one you clicked on
> earlier.)
>
http://www.repp.org/discussiongroups/resources/stoves/Stanley/BriqGassstove.htm
>
> Best regards
>
> Kobus
>
> ----- Original Message -----
> From: Thomas Koch <Tk@tke.dk>
> To: Kobus <ventfory@IAFRICA.COM>
> Sent: 21 October 2003 08:58
> Subject: Re: [GASL] Briquette gasifier stove -
> photos
>
>
> Hi Kobus
>
> I had a look at the lilnk below.
>
> Just one question. How do you define your 35,2 %
> efficiency?
>
> Best regards
>
> Thomas Koch
> ----- Original Message -----
> From: "Kobus" <ventfory@IAFRICA.COM>
> To: <GASIFICATION@LISTSERV.REPP.ORG>
> Sent: Friday, October 17, 2003 3:27 PM
> Subject: [GASL] Briquette gasifier stove - photos
>
>
> Hi all,
>
> We now have photos of our first prototype gasifier
> stove and also include
> the information displayed at the booth in Boulder.
>
> The report can be seen on the stove page or go to
>
http://www.repp.org/discussiongroups/resources/stoves/Kobus/gasbriqstove.htm
>
> Unfortunately it did not gasify properly at the
> conference and was sidelined
> due to a problem with the briquettes (Richard packed
> coffee ground instead
> of coffee husk briquettes!) and other minor design
> faults. Its back in
> Uganda now, undergoing some more testing by Richard.
> Our next prototype
> will be of a similar design, but this time with the
> emphasis on
> cost-effective materials and incorporating improved
> manufacturing and
> assembly techniques, with the emphasis on D.I Y.
> Feedback from the users
> will also determine the final shape it is to take
> over the next couple of
> months. We will also be altering the briquette
> dimensions (volume) to
> increase power output and will focus on perfecting a
> pot shield.
>
> We promise to keep all informed.
>
> Regards
>
> Kobus Venter
> and Richard Stanley

=====
krish

________________________________________________________________________
Want to chat instantly with your online friends? Get the FREE Yahoo!
Messenger http://mail.messenger.yahoo.co.uk

From a31ford at INETLINK.CA Thu Oct 23 06:56:19 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:31 2004
Subject: Throat, Washer test results
Message-ID: <THU.23.OCT.2003.055619.0500.A31FORD@INETLINK.CA>

Greetings Tom, Doug, & All:

The following are the preliminary results of my "washer restricted" Imbert
Throat, on test unit #4.

Throat size 4" O.D. thinwall pipe, (replaced the existing 4" thickwall
throat).
Reduction washer installed at bottom of throat, with an opening of 2 3/4".

Initially, in previous tests (before the washer) this unit would run
continuously for upwards of 96 hours without feedstock hang-ups or throat
bridging (But would eventually quit). After the modification, and a somewhat
cumbersome startup, I ran it for 3 hours, killed the burn, and did a
dissection of the throat contents, much to my surprise, the action of the
washer was NOT what I expected, instead of seeing a "taper" of ash
accumulated on the "lip" the washer creates at the end of the throat, what I
did find was a gooey mess. (about the same as fresh roofing cement). This
was totally NOT expected!

I will note that the ambient temperature was much colder than all other
tests (most done in the 17-21c area, where this one was with 8c air) (unit
is run outdoors) There is a very basic preheat on combustion air on this
unit.

I will re-attempt another test this weekend, hoping it is a bit warmer.

Another Note: The unit did NOT plug, I simply stopped it, (was running short
on time, that day).

Side note fears, are that if this happens again, would that "gooey mess"
actually ignite at sometime, If the burn was run for a longer period? OR was
the mess caused by the stopping of the burn?(sliding down the side of the
throat)?

Greg Manning,
Brandon, Manitoba, Canada

From sandlin at BENDCABLE.COM Fri Oct 24 08:56:57 2003
From: sandlin at BENDCABLE.COM (Jon & Megan Sandlin)
Date: Tue Aug 10 18:24:31 2004
Subject: New to gasification, silly question
Message-ID: <FRI.24.OCT.2003.055657.0700.SANDLIN@BENDCABLE.COM>

I am cuious as to how one can pull gas through a gasifier if I would like to use the gas for a furnace and not an engine. Thanks in advance for your help.

Jon Sandlin
Bend, OR

From kchisholm at CA.INTER.NET Fri Oct 24 09:42:57 2003
From: kchisholm at CA.INTER.NET (Kevin Chisholm)
Date: Tue Aug 10 18:24:31 2004
Subject: New to gasification, silly question
Message-ID: <FRI.24.OCT.2003.104257.0300.KCHISHOLM@CA.INTER.NET>

Dear Jon
----- Original Message -----
From: "Jon & Megan Sandlin" <sandlin@BENDCABLE.COM>
To: <GASIFICATION@LISTSERV.REPP.ORG>
Sent: Friday, October 24, 2003 9:56 AM
Subject: [GASL] New to gasification, silly question

I am cuious as to how one can pull gas through a gasifier if I would like to
use the gas for a furnace and not an engine. Thanks in advance for your
help.

K: OK... think in terms of a pressure differential.... somehow you have to
create a pressure differential within the system that will cause the gas
flows to be what you want them to be.

1: You can put a blower on the "feed side" of the gasifier, and produce a
gas under pressure

2: You can put a suction fan/blower on the discharge side of the gasifier,
to draw gases out of the gasifier, and deliver them in a pressurized state
to your consuming system.

3: You can install a suction fan on the discharge side (stack) of your
furnace.

There are advantages and disadvantages of each "fan/blower location.

Jon Sandlin
Bend, OR

From kssustain at PROVIDE.NET Fri Oct 24 11:41:04 2003
From: kssustain at PROVIDE.NET (Kermit Schlansker)
Date: Tue Aug 10 18:24:31 2004
Subject: Biogas
Message-ID: <FRI.24.OCT.2003.104104.0500.KSSUSTAIN@PROVIDE.NET>

I am interested in the overall usage of biomass gasification as applied to a large building, perhaps 10,000 sq ft on a floor, with 4 stories. There needs to be an effort to utilize every chemical and every bit of energy available. One objective would be to use all waste energy to heat the building in winter.
The chemical outputs could be charcoal, methanol, and tars. The tars would be sold separately as chemicals or possibly when collected could be feedstock for liquid fuels. This means that possibly gasifier output should not necessarily be clean but should produce maximum tars.
One of the objectives would be to farm without using fossil fuels. Some coal could be included, but if enough trees are planted, wood would suffice. Of couse, any methanol collected would be immediately useful as tractor fuel. Charcoal might be gasified in the tractor engine and might be cleaner and more efficient than wood.
My take on the efficiency of conversion of wood to electricity is 60% for the gasification and 30% for the engine thus giving an overall efficiency of 18%. One question is whether the efficiency could be improved by using the Rankine cycle as part of the IC cycle. There are two sources of heat within the process. One is from the cooling of fuel gases, the other is from engine exhaust. I know that the efficiency of gas conversion is improved by a counterflow heat exchanger that heats air into the gasifier while cooling the fuel gases. However it seems to me that there may be some surplus heat that could be used for a Rankine cycle. Any comments on this?
It seems that making methanol from wood implies high pressures of at least 100 atmospheres and oxygen. In my mind that needs to be examined as part of the cogeneration system, perhaps for a 250,000 btus input. I believe that a lock hopper using a piston or screw feed could be built for a small facility. Also small pressure vessels are more practical than large ones, If all waste heat is used for heating it sems to me that making oxygen cryogenically and doing all parts of the process in winter would greatly increase efficiency. Certainly smaller facilities would reduce the radius of wood gathering.
A good possibility for improving the worth of biomass would be to process by pyrolysis in summer using solar energy. Obviously huge steerable solar mirror arrays using a tower target would be needed. If making methanol or charcoal could be done by this process then a mass source of portable fuel could be made. All waste heat is lost but biomass energy is supplemented with solar energy.There can never be any hope of getting enough fuel to power cars. However the powering of essential tractors, buses, and trucks is an attainable and vital objective.
Any comments?

Kermit Schlansker

From ventfory at IAFRICA.COM Fri Oct 24 03:25:22 2003
From: ventfory at IAFRICA.COM (Kobus)
Date: Tue Aug 10 18:24:32 2004
Subject: Briquette gasifier stove - photos
Message-ID: <FRI.24.OCT.2003.092522.0200.VENTFORY@IAFRICA.COM>

Dear Krish,

Drop the "sir", just call me Kobus (the "o" is pronounced same as in the "o" in Moor and with "bis" on the end).

See the following link, it might clear up your questions (not the same one I displayed earlier).

http://www.repp.org/discussiongroups/resources/stoves/Kobus/gasbriqstove.htm

You asked:
> i have seen the photos of your model it is very
> much intresting.i would like to know some details on
> this:
> 1. provision for grate removal of ash.

<KV> The briquette rests on a fuel tray (round plate) which can flip down, ejecting the pyrolysed or ash briquette (if allowed to burn further) into the ash collection area. The briquette, following gasification and char burn is still in tact and minimal ash drops down. It is captured in a pan below, removed and placed in an oxygen free environment (if wanting to preserve the char) or simply emptied out and returned back in position below fuel tray.

> 2. how would you control the primary air supply

<KV> By the sliding door, it is opened at start up and closed after a few minutes when gasification commences.

> 3. what is the total volume of the fuel storage

<KV> Not sure what you mean? Combustion chamber = ?3,500 cm3, Fuel briquette =?550 cm3, Ash collection area= ?12,000 cm3

> 4. what is the specific gasification rate

<KV> Probably at a velocity of around 0.05 m/s, which is a low velocity.

> 5. how much amount of fuel required per hour

<KV> Probably 400g/hour (2 x 200g), removing the pyrolysed briquette
or
300g/hour burning the pyrolysed briquette

> 6. what is the specification of the system

<KV> 450 mm high, 300 mm wide, for more specs see the link above.

> 7. what is the density of the fuel being used

<KV> In the order of 0.22 grams/cm3

Hope this helps.

Regards

Kobus

----- Original Message -----
From: krishna kumar <krishnakumar_07@yahoo.co.uk>
To: Kobus <ventfory@IAFRICA.COM>; <GASIFICATION@LISTSERV.REPP.ORG>
Sent: 23 October 2003 08:41
Subject: Re: [GASL] Briquette gasifier stove - photos

> sir,
> i have seen the photos of your model it is very
> much intresting.i would like to know some details on
> this:
> 1. provision for grate removal of ash.
> 2. how would you control the primary air supply
> 3. what is the total volume of the fuel storage
> 4. what is the specific gasification rate
> 5. how much amount of fuel required per hour
> 6. what is the specification of the system
> 7. what is the density of the fuel being used
>
>
> --- Kobus <ventfory@IAFRICA.COM> wrote: > Hi Thomas,
> >
> > I used the following formula:
> >
> > Efficiency at high Power (%) =
> >
> > (Initial mass of water X spec. heat of water
> > (4.2kJ/kg.K)
> >
> > times (x):
> >
> > (Boiling temp. of water (K) - Initial temp. of
> > water (K))
> >
> > plus (+):
> >
> > (Mass of evaporated water X Latent heat of water
> > (2257 kJ/kg)
> >
> > Answer divided by (/):
> >
> > Mass of fuel used during high power (kg) X Calorific
> > value of the fuel
> > (kJ/kg)
> >
> > I used these recordings:
> >
> > Type of pot: Stainless steel (0.5mm thick)
> > Time water (1 Litre) put on: 2nd minute
> > Time water boiled: 7th minute
> > Time taken to come to boil: 5 minutes
> > Initial temperature of water: 20?C
> > Time water stopped boiling rapidly: 36th minute
> > Time on high power: 34 minutes
> > Mass of fuel used during high power: 125 grams
> > Mass of water boiled on high power: 220 grams
> >
> > In subsequent testing I achieved similar
> > efficiencies by keeping the space
> > between the pot and top of the combustion chamber
> > approximately 2 cm. I
> > think better efficiencies can be obtained by
> > reducing it even further,
> > perhaps down to 1 cm.
> >
> > Feel free to scrutinize our report. We have had
> > very little feedback from
> > the gas and stove list thus far and would welcome
> > any comments.
> >
> > Here is the shortcut (note that it is not the same
> > one you clicked on
> > earlier.)
> >
> http://www.repp.org/discussiongroups/resources/stoves/Stanley/BriqGassstove.htm
> >
> > Best regards
> >
> > Kobus
> >
> > ----- Original Message -----
> > From: Thomas Koch <Tk@tke.dk>
> > To: Kobus <ventfory@IAFRICA.COM>
> > Sent: 21 October 2003 08:58
> > Subject: Re: [GASL] Briquette gasifier stove -
> > photos
> >
> >
> > Hi Kobus
> >
> > I had a look at the lilnk below.
> >
> > Just one question. How do you define your 35,2 %
> > efficiency?
> >
> > Best regards
> >
> > Thomas Koch
> > ----- Original Message -----
> > From: "Kobus" <ventfory@IAFRICA.COM>
> > To: <GASIFICATION@LISTSERV.REPP.ORG>
> > Sent: Friday, October 17, 2003 3:27 PM
> > Subject: [GASL] Briquette gasifier stove - photos
> >
> >
> > Hi all,
> >
> > We now have photos of our first prototype gasifier
> > stove and also include
> > the information displayed at the booth in Boulder.
> >
> > The report can be seen on the stove page or go to
> >
> http://www.repp.org/discussiongroups/resources/stoves/Kobus/gasbriqstove.htm
> >
> > Unfortunately it did not gasify properly at the
> > conference and was sidelined
> > due to a problem with the briquettes (Richard packed
> > coffee ground instead
> > of coffee husk briquettes!) and other minor design
> > faults. Its back in
> > Uganda now, undergoing some more testing by Richard.
> > Our next prototype
> > will be of a similar design, but this time with the
> > emphasis on
> > cost-effective materials and incorporating improved
> > manufacturing and
> > assembly techniques, with the emphasis on D.I Y.
> > Feedback from the users
> > will also determine the final shape it is to take
> > over the next couple of
> > months. We will also be altering the briquette
> > dimensions (volume) to
> > increase power output and will focus on perfecting a
> > pot shield.
> >
> > We promise to keep all informed.
> >
> > Regards
> >
> > Kobus Venter
> > and Richard Stanley
>
> =====
> krish
>
> ________________________________________________________________________
> Want to chat instantly with your online friends? Get the FREE Yahoo!
> Messenger http://mail.messenger.yahoo.co.uk

From joflo at YIFAN.NET Fri Oct 24 14:36:18 2003
From: joflo at YIFAN.NET (Joel Florian)
Date: Tue Aug 10 18:24:32 2004
Subject: Biogas
In-Reply-To: <001901c39a46$276f0000$664356d8@kermit>
Message-ID: <FRI.24.OCT.2003.103618.0800.JOFLO@YIFAN.NET>

Kermit:

I'm interested in some of the very same things -- however, if you are going
to use any of the technologies I'm familiar with, your capital and
maintenance costs are going to be incredibly high. That's not to say it's
impossible. I just don't think it has ever been done before so it will be
a very interesting project when you complete it.

Joel
Alaska

At 10:41 AM 10/24/2003 -0500, Kermit Schlansker wrote:
> I am interested in the overall usage of biomass gasification as
> applied to a large building, perhaps 10,000 sq ft on a floor, with 4
> stories. There needs to be an effort to utilize every chemical and every
> bit of energy available. One objective would be to use all waste energy
> to heat the building in winter.
> The chemical outputs could be charcoal, methanol, and tars. The
> tars would be sold separately as chemicals or possibly when collected
> could be feedstock for liquid fuels. This means that possibly gasifier
> output should not necessarily be clean but should produce maximum tars.
> One of the objectives would be to farm without using fossil
> fuels. Some coal could be included, but if enough trees are planted, wood
> would suffice. Of couse, any methanol collected would be immediately
> useful as tractor fuel. Charcoal might be gasified in the tractor engine
> and might be cleaner and more efficient than wood.
> My take on the efficiency of conversion of wood to electricity is
> 60% for the gasification and 30% for the engine thus giving an overall
> efficiency of 18%. One question is whether the efficiency could be
> improved by using the Rankine cycle as part of the IC cycle. There are
> two sources of heat within the process. One is from the cooling of fuel
> gases, the other is from engine exhaust. I know that the efficiency of
> gas conversion is improved by a counterflow heat exchanger that heats air
> into the gasifier while cooling the fuel gases. However it seems to me
> that there may be some surplus heat that could be used for a Rankine
> cycle. Any comments on this?
> It seems that making methanol from wood implies high pressures
> of at least 100 atmospheres and oxygen. In my mind that needs to be
> examined as part of the cogeneration system, perhaps for a 250,000 btus
> input. I believe that a lock hopper using a piston or screw feed could be
> built for a small facility. Also small pressure vessels are more
> practical than large ones, If all waste heat is used for heating it sems
> to me that making oxygen cryogenically and doing all parts of the process
> in winter would greatly increase efficiency. Certainly smaller facilities
> would reduce the radius of wood gathering.
> A good possibility for improving the worth of biomass would be
> to process by pyrolysis in summer using solar energy. Obviously huge
> steerable solar mirror arrays using a tower target would be needed. If
> making methanol or charcoal could be done by this process then a mass
> source of portable fuel could be made. All waste heat is lost but
> biomass energy is supplemented with solar energy.There can never be any
> hope of getting enough fuel to power cars. However the powering of
> essential tractors, buses, and trucks is an attainable and vital objective.
> Any comments?
>
> Kermit Schlansker

From a31ford at INETLINK.CA Fri Oct 24 18:31:09 2003
From: a31ford at INETLINK.CA (a31ford)
Date: Tue Aug 10 18:24:32 2004
Subject: FW: [GASL] Biogas
Message-ID: <FRI.24.OCT.2003.173109.0500.A31FORD@INETLINK.CA>

Welcome all,

Sounds like some others are on the "Heating Revenge", as I am. (new ppl, see
archives of this month). I for one, agree with a gasifier being used in a
heating only application (it should be used in motor systems ALSO).

BUT my wish is to get the heating aspect correct first!

Then it's simple to run a motor/generator (Genset) on another gasifier for
future electrical needs (Rural hydro power is not as reliable as one would
think.)

Greg Manning,
Brandon, Manitoba, Canada

-----Original Message-----
From: The Gasification Discussion List
[mailto:GASIFICATION@LISTSERV.REPP.ORG]On Behalf Of Joel Florian
Sent: Friday, October 24, 2003 1:36 PM
To: GASIFICATION@LISTSERV.REPP.ORG
Subject: Re: [GASL] Biogas

Kermit:

Joel
Alaska

BioEnergy Lists: Gasifiers & Gasification

October 2003 Gasification Archive