BioEnergy Lists: Gasifiers & Gasification

From Reedtb2 at cs.com Tue Jun 1 07:26:39 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: To Tuyere or Not toTuyere, caution for looking throughair inlets
Message-ID: <a466395d.24851d9f@cs.com>

Arnt et al:

I'll second having protection against sneezes. I was lighting a 75 hp
Hesselman gasifier with acetylene torch, preparing for a Jimmy Carter
inspection 1979, when it sneezed. Lost my right eyebrow and lash - and
gained a lot of caution.

TOM REED
w<<
..I _knew_ I forgot to mention something, this above.

..the final obvious use of tuyeres, is of cource to stick in an
oxy-acetylene welding torch thru one or more tuyeres to light up the
gasifier, or if you like electrics, a music wire thru two and the coal
bed, (chk for shorting) and hook up the power. Automation would require
some form of tuyere manifold into which heated air could be piped, and
fed thru both an electric heat gun or the above torch (big lean flame
for hot O2) for light up, and recycling heat from hot air from the
reactors external surfaces inside some heat shield casing.
Plenty neat ways to do things...
>>
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From graeme at powerlink.co.nz Wed Jun 2 04:14:07 1999
From: graeme at powerlink.co.nz (Graeme Williams)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: To Tuyere or Not to Tuyere, That Is The Question; long
Message-ID: <000201beaccf$8074d260$6fe637d2@graeme>

Arnt & Vern

My apologies for a slow response to this posting. Sorry I cannot snip and
paste to bring orderly responses, so you will have to read it all and delete
accordingly.

1. Recycling exhaust gas through the gasifier suggests by doing so it saved
25% fuel. This was used as a retardant replacing air or more correctly
oxygen, to slow down the combustion rate caused by excess air. In effect,
25% fuel was being combusted and not gasified creating heat, which in those
poorly designed charcoal gasifiers allowed the oxidising charcoal to come
into contact with the steel.

2. Grandad sucked on an upside down updraught gasifier ingesting tar driven
off by the descending fire. Nothing to do with tunnelling.

3. Air nozzles (I don't speak French) distribute the air as evenly as
possible across the area of oxidation, and provide the velocity to
incandesce the char.

4. Air nozzles do not or should not agitate the char creating a phenomena
called "duffing", whereby the fuel tumbles releasing lots of fines. This is
actually caused by plugged reduction and results in combustion and ash fall
plus lowering the oxidation temperature.

5. Throats are nothing more than a scavenger ring which channel tar vapour
coming down between the air nozzles. It doesn't set the oxidation or the
reduction zones, but should be positioned where oxidation ends, and
reduction begins (About l,200 degreesC).

6. Throat velocity has nothing to do with either tar cracking or gas making.
Its just something to measure because its there.

7. Brief descriptions of gas making always leave out something and H2O is
the only description for water in common use. While we haven't "coined" a
gasifier word for it, H2O passing through 1200 degrees C incandescent char,
(that is if you have a packed bed) becomes a little more than H2O, and is
ready to become H2 instead of the sticky stuff!

8. We have never seen evidence of CO reforming into CO2 and soot in the
reduction zone such as you suggest, although it could happen in the ash
bottom of your reduction zone if it was subject to channelling. Our
reforming showed up as heavy soot deposits in piping between the gasifier
and a process heat burner. Rapid quenching to below 500 degrees C is the
only way to stop it happening.

9. Reliable construction materials are required for commercial gasifiers.
We used AVESTA 253MA for our early grates (12mm) and operating 22 hours/day
were still OK after 2 years. I have used 2mm AVESTA for throat reduction
tubes and had no problem with that component. Cheap steels are good if its
for your own use and not shipped to a client in a jungle somewhere.

10. From the dimensions you give and the behaviour of your gasifier,
reduction is taking place above the 4" throat, and it needs lifting closer
to the nozzles. If your fuel was wood chip, then you would only need
approximately 3" of reduction char to the grate or support from where the
gas exits. Suction would only require about 3-5" W.G. to make excellent tar
free gas. Output would run a 2,000cc engine up to about 10kWe.

11. While its interesting to make gas from all types of fuels, it proves
nothing if the gasifier design prevents its practical application into
reliable commercial operation. Nothing any of us do is new or innovative
and there is no merit in repeating mistakes which were overcome 5o years
ago. Downdraught throated gasifiers are not appropriate technology for fine
fuels.
------------------

Have enjoyed shaking the dust off my experience, but thats all I can
contribute for the moment, and now must return to being lurker.

Doug Williams.

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From Reedtb2 at cs.com Wed Jun 2 09:18:46 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Re: Top burning in conventional stoves
Message-ID: <13737553.24868958@cs.com>

Dear Andrew Heggie:
You ask...
<< No one mentions the effect of the relative humidity of air on a
woodfire, is it negligible? We have a high humidity here and it seems
to make a lot of difference in starting a fire to me.
>>
It made me think a little.

1) It takes 1.5 m3 of air to gasify 1 kg of biomass,

2) It is generally recommended that biomass for gasification have < 20%
moisture content.

3) At 90 F, air contains about 3% water at 100% humidity, so 1.5 m3 would
carry 45 g of water, the equivalent of a 4.5% increase if the water was in
the biomass.

4) HOWEVER, the 45 g of water in the air is already a vapor, so there is a
much smaller heat penalty than if you poured 45 g of water on the biomass.

~~~~~~
Water is active in UPDRAFT (charcoal burning) gasification where it moderates
grate temperatures by undergoing the endothermic watergas shift reaction.
However, in downdraft (tar burning) gasification it is only a dilution factor
for the air, a minor affect on flaming pyrolysis temperature.
~~~~~~
Can anyone think of other factors that moisture in combustion/gasification
air would have?

Yours truly, TOM REED
BEF

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From Reedtb2 at cs.com Thu Jun 3 18:20:21 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: To Tuyere or Not to Tuyere, That Is The Question; long
Message-ID: <25dc7480.248859d5@cs.com>

Dear Doug et al:

I should make explicit something that has long been implicit in our
discussions of downdraft gasifiers here at the world CREST site. THERE ARE
TWO SCHOOLS OF THOUGHT .

I. WWII gasifiers (Imbert, throated, tuyerred, Hesselman, ..........)
developed in Europe just prior to WWII. These are tried and true - as far as
they go. If you follow the recipes in our Handbook or a thousand others, you
won't go far wrong. However, better burn a hardwood or pellets.
Incidentally, we had a 75 hp Hesselman at SERI for a decade and did many
experiments and variations learning its +s and - s.

In 1978 we operated the Hesselman (at Dick Bailie's shop in W. Va.) on wood
pellets, since that was a new biomass form since WWII. Then we operated -
gingerly - on air enriched with oxygen - all the way up to 100% oxygen with
no more than a 50C rise in grate temperature. That is what gave us the
courage to build the SERI/NREL "Stratified Downdraft" gasifier. Typical
unburned char 5-10%; typical tar (condensible at 90 C) in raw gas, 1000 ppm.

II. Stratified Downdraft Gasifiers (topless, open core, SERI/NREL, Buck
Rogers, UCDavis, Bangalore, ........) a straight cylinder with air entering
uniformly through the bed for flaming pyrolysis and char gasification. We
operated the 1 t/day unit at SERI from 1980 to 1985 and Prof. Mike Graboski
operated a 24 t/day unit at Hazen from 1985-1988 on both air and oxygen.
Typically 5-10% unburned char-ash and 1000 ppm tar (condensible at 90 C).

The CGP (Combustion, Gasification Pyrolysis [actually Propulsion]) lab under
Prof. Makunda in Bangalore has made a significant improvement in the
Stratified Downdraft gasifier by injecting a fraction of the air below the
pyrolysis zone. This results in complete consumption of the char-ash and tar
frequently < 100 ppm in the raw gas as tested at CGP and CCC (Centre de
compliance de Chatel-St-Denis).

Does anyone know another type of downdraft (tar-burning) gasifier?

Incidentally, the nominclature of gasifiers is totally confusing, updraft,
downdraft, stratified downdraft, inverted downdraft, ..... ad nauseum. I
feel that the most important element they have in common is the first contact
of the air-oxygen:

If it first contacts the charcoal if is a CHAR BURNING gasifier and consumes
all char, but leaves 100,000 ppm tar.

If it first contacts the unburned biomass it is a TAR BURNING gasifier and
leaves 5-10% unburned char-ash and 1000 ppm tar (condensible at 90 C).

All other details are a matter of geometry and convenience.

So it's obvious that I come down on the side of DON'T TUYERRE - you can never
get the air to contact the biomass uniformly. There is also the question of
"To THroat or Not to Throat". NOT.

~~~~~~~~

So..... I hope we hear from many of these groups regarding their current
experience.

Yours truly, TOM REED
BEF
In a message dated 6/2/99 2:17:47 AM Mountain Daylight Time,
graeme@powerlink.co.nz writes:

<<
1. Recycling exhaust gas through the gasifier suggests by doing so it saved
25% fuel. This was used as a retardant replacing air or more correctly
oxygen, to slow down the combustion rate caused by excess air. In effect,
25% fuel was being combusted and not gasified creating heat, which in those
poorly designed charcoal gasifiers allowed the oxidising charcoal to come
into contact with the steel.

2. Grandad sucked on an upside down updraught gasifier ingesting tar driven
off by the descending fire. Nothing to do with tunnelling.

3. Air nozzles (I don't speak French) distribute the air as evenly as
possible across the area of oxidation, and provide the velocity to
incandesce the char.

4. Air nozzles do not or should not agitate the char creating a phenomena
called "duffing", whereby the fuel tumbles releasing lots of fines. This is
actually caused by plugged reduction and results in combustion and ash fall
plus lowering the oxidation temperature.

5. Throats are nothing more than a scavenger ring which channel tar vapour
coming down between the air nozzles. It doesn't set the oxidation or the
reduction zones, but should be positioned where oxidation ends, and
reduction begins (About l,200 degreesC).

6. Throat velocity has nothing to do with either tar cracking or gas making.
Its just something to measure because its there.

7. Brief descriptions of gas making always leave out something and H2O is
the only description for water in common use. While we haven't "coined" a
gasifier word for it, H2O passing through 1200 degrees C incandescent char,
(that is if you have a packed bed) becomes a little more than H2O, and is
ready to become H2 instead of the sticky stuff!

8. We have never seen evidence of CO reforming into CO2 and soot in the
reduction zone such as you suggest, although it could happen in the ash
bottom of your reduction zone if it was subject to channelling. Our
reforming showed up as heavy soot deposits in piping between the gasifier
and a process heat burner. Rapid quenching to below 500 degrees C is the
only way to stop it happening.

9. Reliable construction materials are required for commercial gasifiers.
We used AVESTA 253MA for our early grates (12mm) and operating 22 hours/day
were still OK after 2 years. I have used 2mm AVESTA for throat reduction
tubes and had no problem with that component. Cheap steels are good if its
for your own use and not shipped to a client in a jungle somewhere.

10. From the dimensions you give and the behaviour of your gasifier,
reduction is taking place above the 4" throat, and it needs lifting closer
to the nozzles. If your fuel was wood chip, then you would only need
approximately 3" of reduction char to the grate or support from where the
gas exits. Suction would only require about 3-5" W.G. to make excellent tar
free gas. Output would run a 2,000cc engine up to about 10kWe.

11. While its interesting to make gas from all types of fuels, it proves
nothing if the gasifier design prevents its practical application into
reliable commercial operation. Nothing any of us do is new or innovative
and there is no merit in repeating mistakes which were overcome 5o years
ago. Downdraught throated gasifiers are not appropriate technology for fine
fuels.
------------------

Have enjoyed shaking the dust off my experience, but thats all I can
contribute for the moment, and now must return to being lurker.

Doug Williams.
>>

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From fractional at willmar.com Sat Jun 5 01:21:33 1999
From: fractional at willmar.com (fractional@willmar.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Producer gas BOOK published
Message-ID: <3758BE65.AF832CE3@willmar.com>

Greetings to the List,

Lindsay Publications has reprinted the Australian book by John and
Martin Cash,
" Producer Gas for Motor Vehicles", 1942, 194p. $12.95

http://www.lindsaybks.com/bks/producer/index.html

Many photos and drawings of designs from down under. On page 73
there is a photo of a 40's Ford fitted with a gasifier that is almost
totally concealed within the body work. I presume this is a charcoal
gassifier and its filtering apparatus is limited.
As long as you could sustain the charcoaling loses, a charcoal
gassifier appears to be a better choice for powering small engines
directly (no holding bag). A motorcycle, four-wheeler or electric/"gas"
hybrid lightweight vehicle could benefit form the compactness and
reliable performance of classified charcoal. Reeds book on engine
systems mentions a Florida (?) university group that made a unit for a
motorcycle.
Would that be a wood or charcoal gassifier? My presumption here is
that such a small reactor would have difficulty sustaining a consistent
fire and a conventional wood down draft unit would make too much tar at
times for a lightweight filter system to handle.

The LaFontain FEMA emergency unit has reactor chamber of 6" choked
down to 2" at
the "throat" for small engine use. Has anybody actually run a small
engine over time on one of these gassifiers without bridging and
clogging? Tom Reed mentioned he was developing something along this
line to be displayed sometime this summer.
I just purchased a 7 hp Honda with the intention of generating
24vdc. That should leave me 3 hp on wood gas hopefully. Does anybody
have any suggestions for a mobile gassifier for this 275 cc engine?

Thanks,

Alan

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From Reedtb2 at cs.com Mon Jun 7 12:44:34 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Producer gas BOOK published
Message-ID: <bed7e50.248d50ff@cs.com>

Dear Alan:

I'll look up and try to buy the 1942 Australian book, but mostly historical
interest by now.

We are building a 12 kW low tar gasifier in a 5 gal solvent can over the
summer. Wish us luck. You may be right about charcoal being best for VERY
small engines and with barbecue charcoal so prevalent may be a good source.

Keep me posted,

Yours truly, TOM REED

In a message dated 6/4/99 11:25:08 PM Mountain Daylight Time,
fractional@willmar.com writes:

<<
Lindsay Publications has reprinted the Australian book by John and
Martin Cash,
" Producer Gas for Motor Vehicles", 1942, 194p. $12.95

http://www.lindsaybks.com/bks/producer/index.html

Many photos and drawings of designs from down under. On page 73
there is a photo of a 40's Ford fitted with a gasifier that is almost
totally concealed within the body work. I presume this is a charcoal
gassifier and its filtering apparatus is limited.
As long as you could sustain the charcoaling loses, a charcoal
gassifier appears to be a better choice for powering small engines
directly (no holding bag). A motorcycle, four-wheeler or electric/"gas"
hybrid lightweight vehicle could benefit form the compactness and
reliable performance of classified charcoal. Reeds book on engine
systems mentions a Florida (?) university group that made a unit for a
motorcycle.
Would that be a wood or charcoal gassifier? My presumption here is
that such a small reactor would have difficulty sustaining a consistent
fire and a conventional wood down draft unit would make too much tar at
times for a lightweight filter system to handle.

The LaFontain FEMA emergency unit has reactor chamber of 6" choked
down to 2" at
the "throat" for small engine use. Has anybody actually run a small
engine over time on one of these gassifiers without bridging and
clogging? Tom Reed mentioned he was developing something along this
line to be displayed sometime this summer.
I just purchased a 7 hp Honda with the intention of generating
24vdc. That should leave me 3 hp on wood gas hopefully. Does anybody
have any suggestions for a mobile gassifier for this 275 cc engine?

Thanks,

Alan
>>
Gasification List SPONSORS and ARCHIVES
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From bnatarajan at delhi.icco.net Mon Jun 14 10:25:15 1999
From: bnatarajan at delhi.icco.net (Bhaskar Natarajan)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: information wanted
Message-ID: <199906141425.KAA01796@solstice.crest.org>

id GAA24143
Sender: owner-gasification@crest.org
Precedence: bulk
Reply-To: gasification

The India Canada Environment Facility is an agency set up by the
governments of India and Canada, to support local initiatives in the areas
of environmental improvement. Gasifiers for thermal and electrical energy
is an area of interest. This mail is being sent to put me on the mailing
list of information relating to gasifier projects in India, in particular
and in developing countries in general.

Information can be mailed to:

India Canada Environment Facility
D-1/56, Vasant Vihar
New Delhi 110057
India

Bhaskar Natarajan
Senior Project Consultant

 

Gasification List SPONSORS and ARCHIVES
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From graeme at powerlink.co.nz Tue Jun 15 05:05:23 1999
From: graeme at powerlink.co.nz (Graeme Williams)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere, That Is The Question;
Message-ID: <001401beb70d$b4a4a720$6fe637d2@graeme>

>
>Date: Thu, 3 Jun 1999 18:21:09 EDT
>From: Reedtb2@cs.com
>Subject: Re: GAS-L: To Tuyere or Not to Tuyere, That Is The Question; long
>
>Dear Doug et al:
>
>I should make explicit something that has long been implicit in our
>discussions of downdraft gasifiers here at the world CREST site. THERE ARE
>TWO SCHOOLS OF THOUGHT .
>
>
<Snip>

Dear Gasification Colleagues

Clear Communication.

Over the last few weeks discussion of air nozzles, throats and open core
design features has brought about a comment from Tom R. That there exists
two lines of thought regarding what only can be referred to as the
principles of gasification.

I have often pondered over statements made about various phenomena
experienced by this groups' contributors, for to make any sense it has to be
held up to a yard stick (or metre stick).

This measure is the fundamental principle of bringing oxygen and carbon into
contact, with the interstitial space proportional to the particle size.
When you add the velocity, bed dynamics determined by the fuel size and
species or type that fixes the optimum depth to where the gas and fines can
exit the process.

The position of the gas exit in relation to the bed depth can be fixed by
temperature, in that if you start off with incandescent char (about 1200
degrees C) then reduction will stop at 850 degrees C. Any char passed this
point does nothing except to block the flow of fines out with the gas.
Referred to as frozen reduction.

When you add the rarely mentioned carbon bonding that takes place in the
reduction zone, locking the char into a "living grate", the behaviour of the
gas making process can be accurately predicted and its malfunction defined.
If your process design moves outside of these parameters, then you have to
add stirrers, and shakers and sneeze valves to overcome the blockages we
create by not optimising or understanding how or where the gas is being
created.

At the mention of understanding, historical books such as Gen-gas are
excellent records of the past, in fact Gengas saved my life when it
identified my ill health as advanced CO poisoning. These books do however
contain information in a way that oversimplifies gasification, leading to
gross interpretation of how they work.

It is disappointing to me personally that many comments to our discussions
are brief, cryptic and not supported by clear explanation, which does
nothing but confuse the reader. So lets have informative discussion, ask
clear questions, give clear answers and support statements with explanation.
And please, I believe our work is to optimise the gasmaking process , not to
invent it.

Doug Williams

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From LINVENT at aol.com Tue Jun 15 09:10:28 1999
From: LINVENT at aol.com (LINVENT@aol.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: No Subject
Message-ID: <bfa2b1b2.2497aac2@aol.com>

To the gasification "hotline":
Thermogenics has completed the 24th hour of operation of the new
gasification system completed here in the last few weeks. The unit operates
on sawdust, tires, coal, municipal waste, dried sewage sludge, chips,
plastics and other combustible waste materials. It is currently hooked up to
a Chevy 454 supercharged spark ignited irrigation engine driving a 20 kw
generator, however it is capable of driving a 100 kw generator according to
the manufacturer, however, in our opinion, the engine can support a larger
generator.
The gasifier takes about 30 minutes to come up to stable operation,
and will operate the engine at this point without starting fuel for the
engine. Manual fuel air mixing adjustment is currently required to operate
the engine, this will be changed over to automatic compensation. No
carbureator was supplied with the engine and it is currently running with a 1
1/4" water valve as fuel:air control and a spring loaded check valve as a
pressure regulator for fuel inlet.
The gas is so clean that there is no visible sign of the gas when
vented. No contamination of piping, or any materials placed in the stream has
been detected. The gas is piped to the engine in a clear plastic tube which
shows no contamination or discoloration.
There are contracts in place for the purchase of gasifiers from this
operating system and the commercial installations will be completed before
the end of the year.
We welcome your inquiry about the system relating to sale/lease/BOO
conditions.
Within a short period of time, we will be offering liquid fuels
production capacity.
Look to our website thermogenics.com in the near future for a
complete system photograph.
Yours for better gasification,

Leland T. Taylor
Thermogenics Inc.
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From VHarris001 at aol.com Wed Jun 16 00:34:05 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: To Tuyere or Not to Tuyere, That Is The Question; long
Message-ID: <c97ef07a.24988382@aol.com>

Arnt and Tom R for responses to questions about tuyeres and gasifier design
in general. A special thanks to Doug Williams for taking time away to again
restate his position regarding the process of gasification.

I'm still trying to digest all the information provided by everyone - while
keeping up on all else that keep me busy. It seems that just when I feel I'm
getting a handle on things, more pieces of the puzzle appear to be fitted in
somewhere.

I want to ask questions about Doug Williams' conception of the gasification
process because I believe it is different that that generally in the
literature I've been reviewing. Since he's had to go back to lurking, I'll
post the questions to the gasification list as a whole and see what responses
are given.

Let me begin at the ending of the process. If I understand what Doug is
saying, the constituents of the producer gas from his gasifier are
exclusively CO and H2, both being produced in the carbon bed reduction zone.
Since Doug states that only CO2 and H2O are entering the reduction zone, the
CO and H2 must be produced from the Boudouard Reaction, where C + CO2 -> 2
CO, and the water-gas reaction, where C + H2O -> CO + H2. Since both these
reactions are highly endothermic and rapidly quench the reaction to below
850C, it would seem the heat necessary to drive these reactions must either
be robbed from the upstream oxidation zone -or- the CO2 and H2O entering the
reduction zone at 1200C contain enough heat to drive the reaction.
Additionally, there must be sufficient carbon remaining after all volatiles
are driven from the wood, with sufficient exposure to incoming CO2 and H2O to
allow the reactions to occur.

Going backward in the process an additional step, it seems that in order for
only CO2 and H2O to be leaving the oxidation zone and entering the reduction
zone, complete stoichiometric combustion must occur of all pyrolysis gases in
the oxidation zone. Not starved air combustion, which provides sufficient
heat to drive of volatiles from surrounding fuel - nor excess air combustion,
which would rapidly consume the carbon that had just been devolatized - but
theoretical stoichiometric combustion. In addition, the stoichiometric
combustion of pyrolysis gases must occur at a temperature high enough to
provide the heat needed for the endothermic processes occuring downstream.

To briefly sum up my understanding of Doug's theory regarding this portion of
the gasification process: the volatiles that are released in the
distillation zone pass through the oxidation zone where they are completely
combusted to form CO2 and H2O, which then pass into a carbon bed where they
are reduced to CO and H2. The heat created by the complete combustion of
volatiles is sufficient to drive the reduction processes. The oxidation zone
passes sufficient uncombusted carbon through to the reduction zone to ruduce
all CO2 and H2O (assuming sufficiently dry fuel).

The above contrasts markedly with my understanding of the gasification
process (simplified) where the starved air incineration of part of the fuel
provides heat to release volatiles from the fuel. Generally the higher the
air velocity (SV), the higher the temperature and the more volatiles (oils
and tars) are converted to permanant gases, among them CO, CO2, H2, and CH4.
However, after some point, as SV increases, excess oxygen begins to burn the
combustible gases leading to lower calorific value (CV) gas with higher CO2
content. While this would be desirable in the event that one was able to
reduce all CO2 to 2 CO, this reduction generally occurs very little in a char
bed because the heat required for the reduction process rapidly cools the
entire gasification process. Therefore I had assumed the best one could hope
for was to find the optimum SV for your particular application and you would
have about the best CV gas you can get.

As I read Dougs responses, he is saying it is possible to get past the
problem of the heat being robbed from the oxidation zone by critical spacing
between nozzles and grate, appropriate size and quantity of nozzles,
appropriate fuel size, and exact air blast velocity. As I read Tom Reed, it
appears he has tried getting past the endothermic effects of carbon in the
reduction zone without success. Therefore, in Tom's experiments, the quality
of gas from a gasifier with nozzles and constricted hearth and the quality of
gas from a gasifier without are not sufficiently different to warrant using
nozzles and constricted hearth for gasification. Thus SERI's development of
the open top, nozzleless, throatless stratified downdraft gasifier.

I'm hoping I have accurately described the processes involved. Is this then
is the key to the two different schools of thought? Any input from anyone is
- of course - greatly appreciated!

Vernon Harris
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From graeme at powerlink.co.nz Wed Jun 16 03:32:14 1999
From: graeme at powerlink.co.nz (Graeme Williams)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Re: To Tuyere or Not to Tuyere, That Is The Question; long
Message-ID: <001701beb7c9$e07005e0$64e637d2@graeme>

Dear Vern,
you almost got it right. The oxidisation zone produces all the heat to drive
the reduction and the distillation gasses which are combusted just add to
the total heat budget. I'm very pleased you understood how gasification
works which is not my theory because this is how it always has been.

Doug Williams

>Date: Wed, 16 Jun 1999 00:35:14 EDT
>From: VHarris001@aol.com
>Subject: Re: GAS-L: To Tuyere or Not to Tuyere, That Is The Question; long
>
<SNIP>
>
>I'm hoping I have accurately described the processes involved. Is this
then
>is the key to the two different schools of thought? Any input from anyone
is
>- - of course - greatly appreciated!
>
>Vernon Harris
>

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From Reedtb2 at cs.com Thu Jun 17 09:31:15 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere, ThatIs The Q...
Message-ID: <7ccb3f11.249a52e5@cs.com>

Dear Doug et al:

The study of gasification is a terminal disease. Biomass gasification is
rather more complicated than atomic energy, since solving the mysteries of
the atom only took this century and the mysteries of pyrolysis, gasification
and combustion of biomass are still unsolved in part.

Just a brief addition to Doug's comments. I am beginning to think that
gasification of low density biomass is MUCH harder than high density. It is
important to have the particle hold together and pyrolyse to char during
gasification. But very small particles (straw, chaff, ...) won't wait
around.

The most successful era of biomass gasification was World War II and they
INSISTED on using hardwoods. We tested wood pellets (density > 1.0) with
Dick Bailey in 1979 and found they worked very well. I presume nut shells
are also dense enough.

Densification of biomass produces a uniform fuel not so dependent on original
properties. Glad to see that it is becoming widely practiced. It may be
very important for biomass to become a major energy source.

Comments?

VTY, TOM REED

In a message dated 6/15/99 3:09:52 AM Mountain Daylight Time,
graeme@powerlink.co.nz writes:

<<
Dear Gasification Colleagues

Clear Communication.

Over the last few weeks discussion of air nozzles, throats and open core
design features has brought about a comment from Tom R. That there exists
two lines of thought regarding what only can be referred to as the
principles of gasification.

I have often pondered over statements made about various phenomena
experienced by this groups' contributors, for to make any sense it has to be
held up to a yard stick (or metre stick).

This measure is the fundamental principle of bringing oxygen and carbon into
contact, with the interstitial space proportional to the particle size.
When you add the velocity, bed dynamics determined by the fuel size and
species or type that fixes the optimum depth to where the gas and fines can
exit the process.

The position of the gas exit in relation to the bed depth can be fixed by
temperature, in that if you start off with incandescent char (about 1200
degrees C) then reduction will stop at 850 degrees C. Any char passed this
point does nothing except to block the flow of fines out with the gas.
Referred to as frozen reduction.

When you add the rarely mentioned carbon bonding that takes place in the
reduction zone, locking the char into a "living grate", the behaviour of the
gas making process can be accurately predicted and its malfunction defined.
If your process design moves outside of these parameters, then you have to
add stirrers, and shakers and sneeze valves to overcome the blockages we
create by not optimising or understanding how or where the gas is being
created.

At the mention of understanding, historical books such as Gen-gas are
excellent records of the past, in fact Gengas saved my life when it
identified my ill health as advanced CO poisoning. These books do however
contain information in a way that oversimplifies gasification, leading to
gross interpretation of how they work.

It is disappointing to me personally that many comments to our discussions
are brief, cryptic and not supported by clear explanation, which does
nothing but confuse the reader. So lets have informative discussion, ask
clear questions, give clear answers and support statements with explanation.
And please, I believe our work is to optimise the gasmaking process , not to
invent it.

Doug Williams

>>
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From LINVENT at aol.com Thu Jun 17 10:40:37 1999
From: LINVENT at aol.com (LINVENT@aol.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,ThatIs The Q...
Message-ID: <15e2545f.249a6315@aol.com>

Tom,
I presume you are discussing gasification of materials in a
downdraft mode. I have not been aware of significant differences in the
gasification of materials of low density vs. high density in the fixed bed
design which I use. Reaction time is faster, therefore residence time is
less, but volume is increased in low density vs. higher density materials,
therefore your feeding system operates at virtually the same rate between the
two.
Tom Taylor
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From dschmidt at eerc.und.nodak.edu Thu Jun 17 10:51:15 1999
From: dschmidt at eerc.und.nodak.edu (Schmidt, Darren)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Just a thought
Message-ID: <601A55066596D211A7AD00104BC6FB2507347E@catalina.eerc.und.NoDak.edu>

It was once mentioned to me that materials may gasify better under vacuum
than under pressure. This would be a plus for downdraft gasification.
Anyone have any comments?

D. Schmidt
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From zhicheng.ye at chemeng.lth.se Thu Jun 17 11:26:12 1999
From: zhicheng.ye at chemeng.lth.se (zhicheng ye)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Where in Europe can we pelletize straw?
Message-ID: <3.0.3.32.19990617172334.0069c21c@mail.chemeng.lth.se>

 

Dear gasification colleagues

At the moment we have a EU project using straw as fuel. In order to feed
straw into our test rig we need to pelletise it. Unfortunately we have not
yet found anyone who can pellitise straw.

Is there anyone on the list knows something about this? For practical
reason we are expecting a company located in Europe.

Thanks in advance for any valuable information.

Zhicheng Ye

-------------------
Zhicheng Ye
Dr., Research Associate
Department of Chemical Engineering II
Lund University
P.O. Box 124
221 00 Lund
Sweden

Phone: + 46 46 222 8250
Fax: + 46 46 222 8281

E-post: zhicheng.ye@chemeng.lth.se
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From VHarris001 at aol.com Thu Jun 17 11:41:24 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: High Temp Metals - was To Tuyere or Not to Tuyere
Message-ID: <1b1adda.249a712c@aol.com>

Dear Doug, others

Thanks for the reference on Avesta Sheffield metal 253MA. For others
interested in this metal, further info can be obtained at their website at:

http://www.avestasheffield.com/

Also, the properties for Inconel, another high temperature metal can be
viewed at:

http://www.incoalloys.com/index.html

Regards,
Vern Harris

In a message dated 6/2/99 4:17:34 AM Eastern Daylight Time,
graeme@powerlink.co.nz writes:

>
> 9. Reliable construction materials are required for commercial gasifiers.
> We used AVESTA 253MA for our early grates (12mm) and operating 22 hours/day
> were still OK after 2 years. I have used 2mm AVESTA for throat reduction
> tubes and had no problem with that component. Cheap steels are good if its
> for your own use and not shipped to a client in a jungle somewhere.
>
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From Murat.Dogru at newcastle.ac.uk Thu Jun 17 12:06:55 1999
From: Murat.Dogru at newcastle.ac.uk (Murat DOGRU)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
In-Reply-To: <7ccb3f11.249a52e5@cs.com>
Message-ID: <199906171548.QAA27483@cheviot.ncl.ac.uk>

 

Dear Tom et al.,

I have tested hazel nut shells with a downdraft gasifier
over than 30 capacity and modified runs.
I have also tested wood digested sewage sludge with almost same
calorific value as hazelnut shells. The only basic difference was
hazelnut shells more dense than wood and sludge. Gasification of
hazelnut shells with downdraft gasifier was obviously better than
gasification of wood ad sludge with respect to calorific value of
produced gas.

So, I am aggree with you that high dense biomass is far more better
than low dense one.

If you are curious about the results of nut shell gasification,
I will be presenting the results on "Fourth Biomass Conferences of
the Americas" this summer. I hope to see you there.

Regards
M. DOGRU
University of Newcastle
UK

> From: Reedtb2@cs.com
> Date: Thu, 17 Jun 1999 09:32:21 EDT
> Subject: Re: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere, That
> Is The Q...
> To: gasification@crest.org
> Reply-to: gasification@crest.org

> Dear Doug et al:
>
> The study of gasification is a terminal disease. Biomass gasification is
> rather more complicated than atomic energy, since solving the mysteries of
> the atom only took this century and the mysteries of pyrolysis, gasification
> and combustion of biomass are still unsolved in part.
>
> Just a brief addition to Doug's comments. I am beginning to think that
> gasification of low density biomass is MUCH harder than high density. It is
> important to have the particle hold together and pyrolyse to char during
> gasification. But very small particles (straw, chaff, ...) won't wait
> around.
>
> The most successful era of biomass gasification was World War II and they
> INSISTED on using hardwoods. We tested wood pellets (density > 1.0) with
> Dick Bailey in 1979 and found they worked very well. I presume nut shells
> are also dense enough.
>
> Densification of biomass produces a uniform fuel not so dependent on original
> properties. Glad to see that it is becoming widely practiced. It may be
> very important for biomass to become a major energy source.
>
> Comments?
>
> VTY, TOM REED
>
>
> In a message dated 6/15/99 3:09:52 AM Mountain Daylight Time,
> graeme@powerlink.co.nz writes:
>
> <<
> Dear Gasification Colleagues
>
> Clear Communication.
>
> Over the last few weeks discussion of air nozzles, throats and open core
> design features has brought about a comment from Tom R. That there exists
> two lines of thought regarding what only can be referred to as the
> principles of gasification.
>
> I have often pondered over statements made about various phenomena
> experienced by this groups' contributors, for to make any sense it has to be
> held up to a yard stick (or metre stick).
>
> This measure is the fundamental principle of bringing oxygen and carbon into
> contact, with the interstitial space proportional to the particle size.
> When you add the velocity, bed dynamics determined by the fuel size and
> species or type that fixes the optimum depth to where the gas and fines can
> exit the process.
>
> The position of the gas exit in relation to the bed depth can be fixed by
> temperature, in that if you start off with incandescent char (about 1200
> degrees C) then reduction will stop at 850 degrees C. Any char passed this
> point does nothing except to block the flow of fines out with the gas.
> Referred to as frozen reduction.
>
> When you add the rarely mentioned carbon bonding that takes place in the
> reduction zone, locking the char into a "living grate", the behaviour of the
> gas making process can be accurately predicted and its malfunction defined.
> If your process design moves outside of these parameters, then you have to
> add stirrers, and shakers and sneeze valves to overcome the blockages we
> create by not optimising or understanding how or where the gas is being
> created.
>
> At the mention of understanding, historical books such as Gen-gas are
> excellent records of the past, in fact Gengas saved my life when it
> identified my ill health as advanced CO poisoning. These books do however
> contain information in a way that oversimplifies gasification, leading to
> gross interpretation of how they work.
>
> It is disappointing to me personally that many comments to our discussions
> are brief, cryptic and not supported by clear explanation, which does
> nothing but confuse the reader. So lets have informative discussion, ask
> clear questions, give clear answers and support statements with explanation.
> And please, I believe our work is to optimise the gasmaking process , not to
> invent it.
>
> Doug Williams
>
> >>
> Gasification List SPONSORS and ARCHIVES
> http://www.crest.org/renewables/gasification-list-archive
>
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From arnt at c2i.net Thu Jun 17 14:43:52 1999
From: arnt at c2i.net (Arnt Karlsen)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
In-Reply-To: <199906171548.QAA27483@cheviot.ncl.ac.uk>
Message-ID: <3769419A.F8D3DC70@c2i.net.>

Congratulations again, Murat

Will you publish anything on your work gasifying sewer sludge?

Find data on "our" sludge in url:
http://www.ivar.rl.no/avlop_slamdisponering.html

..note that I am in no way affiliated to this organization other than
paying taxes and providing a 1/190 000'th of the raw material ;-)

--
..Arnt ..to bypass my spam filter: cut ".no" in my address... ;-)
Gasification List SPONSORS and ARCHIVES
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From Murat.Dogru at newcastle.ac.uk Fri Jun 18 08:17:56 1999
From: Murat.Dogru at newcastle.ac.uk (Murat DOGRU)
Date: Tue Aug 31 21:08:07 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
In-Reply-To: <3769419A.F8D3DC70@c2i.net.>
Message-ID: <199906181202.NAA01814@cheviot.ncl.ac.uk>

 

Dear Arnt and friends,

Regarding your question:
I have written a report and a paper about the sewage sludge
gasification with a downdraft gasifier.
Basically, I have reported the experimental data and derivative
results (full mass and energy balances) for this sludge gasification.
200 page report submitted to a company in UK which work has been
carried out for their request. This report is not going to be
published. But, I am planning to send the paper substracted from this
report called "Sewage sludge gasification with a throated downdraft
gasifier" to the "Journal of Fuel". If not, I will let you know where
it is going to be published. Except clinker formation, there is no
problem whatsoever for gasifying sludge ( and also it smell awful).
Gas is produced from the sludge is extremely dirty comparing hazelnut
shell and wood chip produced gases despite using a downdraft
gasifier. So, very good scrubber is needed. Rest of the details will
be in that paper.

Regards
Murat

> Date: Thu, 17 Jun 1999 20:42:34 +0200
> From: Arnt Karlsen <arnt@c2i.net>
> Organization: ing. Arnt Karlsen
> To: gasification@crest.org, Murat DOGRU <Murat.Dogru@NEWCASTLE.AC.UK>
> Subject: Re: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
> Reply-to: gasification@crest.org

> Congratulations again, Murat
>
> Will you publish anything on your work gasifying sewer sludge?
>
> Find data on "our" sludge in url:
> http://www.ivar.rl.no/avlop_slamdisponering.html
>
> ..note that I am in no way affiliated to this organization other than
> paying taxes and providing a 1/190 000'th of the raw material ;-)
>
> --
> ..Arnt ..to bypass my spam filter: cut ".no" in my address... ;-)
> Gasification List SPONSORS and ARCHIVES
> http://www.crest.org/renewables/gasification-list-archive
>
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From buitn at hcm.vnn.vn Fri Jun 18 10:58:02 1999
From: buitn at hcm.vnn.vn (Bui Tuyen)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere, ThatIs The Q...
Message-ID: <19990618145940.AAB27891@4rgroup>

Dear Tom et al,
Atomic experts will not feel easy if they try to do business with any
material without purification. With raw a mountain of rock or a river of
water they hardly can get any fission or fusion out.
We don't have problems with good charcoal or good hardwood.
So what is the next step? carbonization is low-efficiency, then maybe
densification I guess.
Tuyen.

----------
> From: Reedtb2@cs.com
> To: gasification@crest.org
> Subject: Re: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
ThatIs The Q...
> Date: Thursday, June 17, 1999 8:32 PM
>
> Dear Doug et al:
>
> The study of gasification is a terminal disease. Biomass gasification is

> rather more complicated than atomic energy, since solving the mysteries
of
> the atom only took this century and the mysteries of pyrolysis,
gasification
> and combustion of biomass are still unsolved in part.
>
> Just a brief addition to Doug's comments. I am beginning to think that
> gasification of low density biomass is MUCH harder than high density. It
is
> important to have the particle hold together and pyrolyse to char during
> gasification. But very small particles (straw, chaff, ...) won't wait
> around.
>
> The most successful era of biomass gasification was World War II and they

> INSISTED on using hardwoods. We tested wood pellets (density > 1.0) with

> Dick Bailey in 1979 and found they worked very well. I presume nut
shells
> are also dense enough.
>
> Densification of biomass produces a uniform fuel not so dependent on
original
> properties. Glad to see that it is becoming widely practiced. It may be

> very important for biomass to become a major energy source.
>
> Comments?
>
> VTY, TOM REED
> Gasification List SPONSORS and ARCHIVES
> http://www.crest.org/renewables/gasification-list-archive
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From mlefcort at compuserve.com Fri Jun 18 11:08:38 1999
From: mlefcort at compuserve.com (Malcolm D. Lefcort)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
Message-ID: <199906181109_MC2-79DE-F94A@compuserve.com>

Murat,

What was the moisture content of the sludge as fed to the gasifier?

Malcolm Lefcort

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From Murat.Dogru at newcastle.ac.uk Fri Jun 18 11:51:33 1999
From: Murat.Dogru at newcastle.ac.uk (Murat DOGRU)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Clear Communication. was To Tuyere or Not to Tuyere,
In-Reply-To: <199906181109_MC2-79DE-F94A@compuserve.com>
Message-ID: <199906181534.QAA09850@cheviot.ncl.ac.uk>

 

Dear Malcolm et al.,

Moisture content of the dried and undigested sewage sludge was around
8.5 to 11 %.
According to our balance calculations;
80 percent of the produced gas should be used for the dryer to dry
sludge up to 11 %. Rest of the produced gas (~4.5 MJ/m3) can drive
the CHP as profit.
I believe, there is no need to dry sludge up to 11 percent because
the downdraft throated gasifier works perfect (comparing low
moisture fuel) using dried sewage sludge with moisture content
up to btw 20-25 %. This is probably because higher moisture content
of sludge lowers the oxidation bed temperature below than fusion
temperature of sludge (so less clinker forms) and extra moisture
causes water-shift reaction to produce more combustible gasses.

I hope this was helpful.

Regards
M.DOGRU
University of Newcastle
UK

> Date: Fri, 18 Jun 1999 11:09:30 -0400
> From: "Malcolm D. Lefcort" <mlefcort@compuserve.com>
> Subject: Re: GAS-L: Clear Communication. was To Tuyere or Not to
> Tuyere,
> To: "INTERNET:gasification@crest.org" <gasification@crest.org>
> Reply-to: gasification@crest.org

> Murat,
>
> What was the moisture content of the sludge as fed to the gasifier?
>
> Malcolm Lefcort
>
> Gasification List SPONSORS and ARCHIVES
> http://www.crest.org/renewables/gasification-list-archive
>
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From p.m.davies at mail.bigpond.com.au Sat Jun 19 15:54:51 1999
From: p.m.davies at mail.bigpond.com.au (Peter M Davies)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: pelletize straw
In-Reply-To: <3.0.3.32.19990617172334.0069c21c@mail.chemeng.lth.se>
Message-ID: <04131498939264@domain6.bigpond.com>

Dear Zhicheng Ye ,

Yes you should be able to pelletize straw so long as the lignin
content is around 10% and the feedstock is less than 12% moisture
content. Also you will have to first grind the straw (usually with
a hammermill) to reduce its size to less than 9.5mm for it to feed
through the pellet press.

Most commercial pellet presses use a combination of heat
and pressure to produce the pellets. They are generally very
inefficient since they rely on converting mechanical energy through
friction (as the compressed material moves through the die) to
generate the heat.

More recently with a better understanding of the physical and
chemical processes involved we are now seeing briquette and pellet
machines using pre heated feedstock and dies which greatly reduce the
wear and energy requirements of the press.

In Europe pellet presses are used in animal feed manufacturing and
wood pelleting for use in automated boilers. You should be able to
locate one through contact with your local agricultural or forestry
agencies. I do have some European addresses of manufacturers but
they are five years old.

Be aware that pellets are sometimes produced with binding agents.
These can be organic or inorganic and you will need to check with
your processing agent when you find one because these will produce
very different results if you use the pellets for energy.

Regards,
Peter M Davies

Peter M Davies
"Neikah"
Colinton NSW Australia 2626
Ph: 02 64 544 009
Email: p.m.davies@bigpond.com.au

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From tmiles at teleport.com Sat Jun 19 16:12:47 1999
From: tmiles at teleport.com (Tom Miles)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Where in Europe can we pelletize straw?
In-Reply-To: <3.0.3.32.19990617172334.0069c21c@mail.chemeng.lth.se>
Message-ID: <199906192012.QAA14387@solstice.crest.org>

Mr. Zhicheng Ye,

Pelletizing straw for combustion and gasification was a favorite topic for
European research organizations in the 1970's and 1980's.

I refer you to a very good study done in 1986 by our friends at VTT,
Technical Research Centre of Finland, titled "Pelletization and Combustion
of Straw," by Carl Wilen, Pekka Stahlberg, Kai Sipila and Jukka Ahokas
(State Institute of Engineering in Agriculture and Forestry, Finland).
While we now understand the mechanisms of alkali volatilization in straw
combustion and gasification better than we did then, they did a very good
summary of the costs and products from straw pelletization.

I did not find a project summary online at the VTT website http://www.vtt.fi

You can try and contact:
Carl Wilén Tel. +358 9 4655452
Senior Research Engineer Fax. +358 9 460493
VTT Energy E-mail: Carl.Wilen@vtt.fi
New Energy Technologies
P.O.Box 1601, FIN-02044 VTT, Finland
Biologinkuja 5, Espoo

Commercially you should be able to find companies in Sweden who are
adventurous enough to pelletize straw.

Regards,

Tom Miles

 

At 05:23 PM 6/17/99 +0200, zhicheng ye wrote:
>
>Dear gasification colleagues
>
>At the moment we have a EU project using straw as fuel. In order to feed
>straw into our test rig we need to pelletise it. Unfortunately we have not
>yet found anyone who can pellitise straw.
>
>Is there anyone on the list knows something about this? For practical
>reason we are expecting a company located in Europe.
>
>Thanks in advance for any valuable information.
>
>
>Zhicheng Ye
>
>-------------------
>Zhicheng Ye
>Dr., Research Associate
>Department of Chemical Engineering II
>Lund University
>P.O. Box 124
>221 00 Lund
>Sweden
>
>Phone: + 46 46 222 8250
>Fax: + 46 46 222 8281
>
>E-post: zhicheng.ye@chemeng.lth.se
>Gasification List SPONSORS and ARCHIVES
>http://www.crest.org/renewables/gasification-list-archive
>
------------------------------------------------------------------------------
Thomas R. Miles tmiles@teleport.com
Technical Consultants, Inc. Tel (503) 292-0107/646-1198
1470 SW Woodward Way Fax (503) 605-0208
Portland, Oregon, USA 97225

Gasification List SPONSORS and ARCHIVES
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From VHarris001 at aol.com Mon Jun 21 00:38:08 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Tar vs Char Burning - was To Tuyere or Not to Tuyere
Message-ID: <f9d1fae8.249f1bf9@aol.com>

Dear Tom Reed,

Thanks for your feedback on the tuyere and throat issues.

I have a question regarding the TAR BURNING vs the CHAR BURNING categories.
Is CO-CURRENT FLOW always the same as TAR BURNING? Also, is COUNTER-CURRENT
FLOW always the same as CHAR BURNING?

Your description of TAR BURNING gasifiers includes the phrase "condensible at
90C." Does that also apply to the tar generated by the CHAR BURNING gasifier?

What is the special significance of the condensible point of the tar at 90C?

Thanks,
Vernon Harris

In a message dated 6/3/99 6:24:10 PM Eastern Daylight Time, Reedtb2@cs.com
writes:

> Incidentally, the nominclature of gasifiers is totally confusing, updraft,
> downdraft, stratified downdraft, inverted downdraft, ..... ad nauseum. I
> feel that the most important element they have in common is the first
> contact
> of the air-oxygen:
>
> If it first contacts the charcoal if is a CHAR BURNING gasifier and
consumes
>
> all char, but leaves 100,000 ppm tar.
>
> If it first contacts the unburned biomass it is a TAR BURNING gasifier and
> leaves 5-10% unburned char-ash and 1000 ppm tar (condensible at 90 C).
>
> All other details are a matter of geometry and convenience.
>
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From VHarris001 at aol.com Mon Jun 21 01:04:59 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Stabilizing the Oxidation Zone - was To Tuyere or Not toTuyere
Message-ID: <eab69906.249f2241@aol.com>

Dear Tom Reed,

As I recall, when operated on oxygen, the SERI/NREL "Stratified Downdraft"
gasifier would become top stabilized - that is the flaming pyrolysis occurs
at the top of the fuel bed while uncombusted fuel remains lower in the bed.
Can you explain what this phenomenon is, why it occurs and how it relates to
TAR BURNING gasification. That is, if flaming pyrolysis occurs at the top of
the fuel bed, does the top fuel then eventually turn to char? If so, does
the gasifier then begin combusting the char while unpyrolized fuel still
remains downstream - in effect turning a tar burning gasifier into a char
burning gasifier?

Could you also addrress the issue of the oxidation zone prematurely moving
upstream in the fuel bed of the stratified downdraft gasifier? It seems
these points might go to the heart of the issue both Arnt and Doug have made
regarding the need to stabilize the oxidation zone in the fuel.

Thanks,
Vernon Harris

In a message dated 6/3/99 6:24:10 PM Eastern Daylight Time, Reedtb2@cs.com
writes:

>
> In 1978 we operated the Hesselman (at Dick Bailie's shop in W. Va.) on
wood > pellets, since that was a new biomass form since WWII. Then we
operated -
> gingerly - on air enriched with oxygen - all the way up to 100% oxygen
with
> no more than a 50C rise in grate temperature. That is what gave us the
> courage to build the SERI/NREL "Stratified Downdraft" gasifier. Typical
> unburned char 5-10%; typical tar (condensible at 90 C) in raw gas, 1000
ppm.
>
>
>
> II. Stratified Downdraft Gasifiers (topless, open core, SERI/NREL, Buck
> Rogers, UCDavis, Bangalore, ........) a straight cylinder with air
entering
> uniformly through the bed for flaming pyrolysis and char gasification. We
> operated the 1 t/day unit at SERI from 1980 to 1985 and Prof. Mike
Graboski
> operated a 24 t/day unit at Hazen from 1985-1988 on both air and oxygen.
> Typically 5-10% unburned char-ash and 1000 ppm tar (condensible at 90 C).
>
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From VHarris001 at aol.com Mon Jun 21 01:31:25 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Reactor Pressure - was To Tuyere or Not to Tuyere
Message-ID: <c5859df2.249f2871@aol.com>

Dear Arnt,

Thanks for your responses to my posts. There were several questions I have,
but it sometimes takes me a while to figure out just what the questions are.

You state that the syngas yield will increase by keeping the reactor vessel
pressure as low as possible. I've heard that before and seen it being asked
on the list before. However, I don't understand how that would be. I must
be missing something. I understand that the fuel will react differently to
the pressure drop across the fuel bed, but that is a difference in the
pressures at inlet vs outlet points rather than an absolute pressure
measurement. If the pressure drop is 1 psi across the fuel bed, what
difference would it make if the inlet pressure was 1 psig and the outlet
pressure was 0 psig over - say - the inlet pressure being 10 psig and the
outlet pressure being 9 psig? It seems to me the key issue is the velocity
of air into the reactor and gas out of the reactor rather that minimizing the
absolute pressure of the system. Further, other than mechanical restrictions
of gas flow such as tuyeres, throats, grate design, etc. the pressure drop
across the fuel bed needed to obtain the required superficial velocity will
be a function of the nature of the fuel itself. Thus the fuel grinding and
metering requirements you mention.

If you could further delineate this point, particularly the role of tuyeres
in maintaining a hot zone with low pressure, it would be helpful.

Thanks,
Vernon Harris

In a message dated 5/28/99 7:32:40 PM Eastern Daylight Time, arnt@c2i.net
writes:

> .sure. Now reviewing the governing chemistry involved, you will learn
> you increase syngas yield by keeping the reactor vessel pressure as
> _low_ as possible, which will harm combustion. There are other dirty
> tricks such as feeding oxygen, propane or syngas flaring, _grinding and
> metering_ the fuel feed or use a multi stage reactor system.
>
> You will want to _precisely_ control the reduction zone conditions, you
> want to keep it hot _enough and at a low enough_ pressure to maximize
> syngas yield.
> The _cost-effective_ way to do this is tuyeering, which can be tweaked
> minimizing air feed, maximizing air jet speed, and recycling exhaust gas
> thru 'em.
>
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From VHarris001 at aol.com Mon Jun 21 02:15:56 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: High Temp Metals - was To Tuyere or Not to Tuyere
Message-ID: <b17eb690.249f32e3@aol.com>

Dear Arnt, others

About a year ago I contacted representatives for both Inconel and 253MA and
was unable to get helpful responses from either of them regarding the
servicability of their materials for use in my gasification application.
Besides being a reducing atmosphere in hot, abrasive conditions, my gasifier
will also have some sulpher present. The Inconel representative simply said
they had no material of which they could guarantee the performance. The
253MA rep said better to just try stainless steel first and see what happens.
Says he has seen very disappointing performance from 253MA in certain
applications. It varys application to application. He recommends it
without question in many applications but others he doesn't, gasification
being one that requires caution. He wouldn't even recommend 353MA - which
was designed for gasification applications.

I was all sold on high temp metals until I read Arnt's post last year about
the coating on metals not being able to be regenerated in a reducing
atmosphere. Thanks again Arnt!

Vern

In a message dated 5/28/99 7:32:40 PM Eastern Daylight Time, arnt@c2i.net
writes:

>
> .note that stainless steels, titanium etc, _will corrode_ in our dusty
> hot reducing environments, their corrosion protection rely on _surface_
> oxygen diffusing into the metal, I was quoted a 10 minute service life
> on some top priced titanium piping, we use cheap heat resistant mild
> steel...
>
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From Reedtb2 at cs.com Tue Jun 22 07:59:18 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Reactor Pressure
Message-ID: <d5b47b0c.24a0d4e5@cs.com>

Dear Arnt et al:

I can't get too involved in this discussion, but here is some clarification,
I hope.

I think there is confusion here between the effect of pressure drops (bed,
cyclone etc.) and the effect of absolute pressure.

According to the calculations of Ray Desrosiers in our 1980 Biomass
Gasification, the EQUILIBRIUM gas composition changes very little between an
absolute pressure of 1 and 20 atm.

Other than that, the pressure drop in the gasifier and associated cleaning
etc. would seem to be straightforward. Use the Ergun equation for pressure
drop in fixed beds - it worked well for us.

Cheers, TOM REED
BEF

In a message dated 6/20/99 11:36:41 PM Mountain Daylight Time,
VHarris001@aol.com writes:

<< Dear Arnt,

Thanks for your responses to my posts. There were several questions I have,
but it sometimes takes me a while to figure out just what the questions are.

You state that the syngas yield will increase by keeping the reactor vessel
pressure as low as possible. I've heard that before and seen it being asked
on the list before. However, I don't understand how that would be. I must
be missing something. I understand that the fuel will react differently to
the pressure drop across the fuel bed, but that is a difference in the
pressures at inlet vs outlet points rather than an absolute pressure
measurement. If the pressure drop is 1 psi across the fuel bed, what
difference would it make if the inlet pressure was 1 psig and the outlet
pressure was 0 psig over - say - the inlet pressure being 10 psig and the
outlet pressure being 9 psig? It seems to me the key issue is the velocity
of air into the reactor and gas out of the reactor rather that minimizing
the
absolute pressure of the system. Further, other than mechanical
restrictions
of gas flow such as tuyeres, throats, grate design, etc. the pressure drop
across the fuel bed needed to obtain the required superficial velocity will
be a function of the nature of the fuel itself. Thus the fuel grinding and
metering requirements you mention.

If you could further delineate this point, particularly the role of tuyeres
in maintaining a hot zone with low pressure, it would be helpful.

Thanks,
Vernon Harris

In a message dated 5/28/99 7:32:40 PM Eastern Daylight Time, arnt@c2i.net
writes:

> .sure. Now reviewing the governing chemistry involved, you will learn
> you increase syngas yield by keeping the reactor vessel pressure as
> _low_ as possible, which will harm combustion. There are other dirty
> tricks such as feeding oxygen, propane or syngas flaring, _grinding and
> metering_ the fuel feed or use a multi stage reactor system.
>
> You will want to _precisely_ control the reduction zone conditions, you
> want to keep it hot _enough and at a low enough_ pressure to maximize
> syngas yield.
> The _cost-effective_ way to do this is tuyeering, which can be tweaked
> minimizing air feed, maximizing air jet speed, and recycling exhaust gas
> thru 'em.
>
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>>
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From Reedtb2 at cs.com Tue Jun 22 07:59:50 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Stabilizing the Oxidation Zone - was To Tuyere or Not toTuyere
Message-ID: <ba8b8982.24a0d4ea@cs.com>

Dear Vern et al:

Good question.

I now believe that one should view a downdraft gasifier as a tar burning
first stage and a char consuming (gasifying) 2nd stage. For a steady state
gasifier, these two stages need to be kept in balance.

In the Imbert gasifier they are kept in balance by injection of air at the
interface between fresh fuel and charcoal. If too much char is produced, the
air begins to gasify the charcoal directly; if too little char is produced
the incoming air burns more tar to create more char to bring the unit back
into balance.

I believe this "balancing act" is the principle reason why the IMBERT
gasifier was so successful.

In the stratified downdraft gasifier we observed that the reaction zone could
be grate stabilized (with wet fuels), mid stabilized (by injection of a small
fraction of the air where the zone was stabilized) or top stabilized (for dry
fuels). Grate and mid stabilized gives a steady state gasifier. Top
stabilized isn't stable - you keep creating more charcoal. (You can
stabilize it by augering out charcoal, a valuable product, but then you get a
tarry gas.)

We are exploring these relationships further this summer and will visit
again. Keep up the good questions....

Cheers, TOM REED
BEF

In a message dated 6/20/99 11:09:47 PM Mountain Daylight Time,
VHarris001@aol.com writes:

<<
Dear Tom Reed,

As I recall, when operated on oxygen, the SERI/NREL "Stratified Downdraft"
gasifier would become top stabilized - that is the flaming pyrolysis occurs
at the top of the fuel bed while uncombusted fuel remains lower in the bed.
Can you explain what this phenomenon is, why it occurs and how it relates to
TAR BURNING gasification. That is, if flaming pyrolysis occurs at the top
of
the fuel bed, does the top fuel then eventually turn to char? If so, does
the gasifier then begin combusting the char while unpyrolized fuel still
remains downstream - in effect turning a tar burning gasifier into a char
burning gasifier?

Could you also addrress the issue of the oxidation zone prematurely moving
upstream in the fuel bed of the stratified downdraft gasifier? It seems
these points might go to the heart of the issue both Arnt and Doug have made
regarding the need to stabilize the oxidation zone in the fuel.

Thanks,
Vernon Harris

>>
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From Reedtb2 at cs.com Tue Jun 22 08:00:07 1999
From: Reedtb2 at cs.com (Reedtb2@cs.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Tar vs Char Burning - was To Tuyere or Not to Tuyere
Message-ID: <64b2b59a.24a0d4eb@cs.com>

Dear Vern et al:

Two more good questions!

"Tar burning" = co-current, a name already in existence. However, in the
inverted downdraft cook stove the bed is not moving and "co-current" could be
confusing and "tar burning" defines the major differenc ein gas quality terms.

Also, "Char-burning" = countercurrent. Thanks for elucidating this.....

The 90 C condensation temperature condenses tar but not water and the
properties of tar and tar-water mixtures are very different. For maximum
power from an engine cool and clean the gas to 20 C or below. For minimum
cleanup, cool and clean to just above the dew point and get a bigger engine
(says Agua Das).

Yours, TOM REED
BEF

In a message dated 6/20/99 10:42:09 PM Mountain Daylight Time,
VHarris001@aol.com writes:

<< Dear Tom Reed,

Thanks for your feedback on the tuyere and throat issues.

I have a question regarding the TAR BURNING vs the CHAR BURNING categories.
Is CO-CURRENT FLOW always the same as TAR BURNING? Also, is COUNTER-CURRENT
FLOW always the same as CHAR BURNING?

Your description of TAR BURNING gasifiers includes the phrase "condensible
at
90C." Does that also apply to the tar generated by the CHAR BURNING
gasifier?

What is the special significance of the condensible point of the tar at 90C?

Thanks,
Vernon Harris
>>
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From vvnk at teri.res.in Fri Jun 25 03:10:25 1999
From: vvnk at teri.res.in (V V N Kishore)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Kansas biomass project
Message-ID: <s7737920.035@dakghar.teri.res.in>

I believe that SV (or the related specific gasification rate expressed in Nm^3/cm^2 sec) is a good indicator for sizing the gasifier,but our experience shows that it need not correlate well with tar content.Our silk reeling gasifiers operate with an SV of 0.07 m/s and yet we dont have too much tar (the duct connecting the gas to the burner is cleaned once in a month,and I have seen so called commercial gasifiers which require cleaning of hot gas pipes every 48 hrs).Our power gasifiers operate with an SV of 0.27 m/s and produce tars of the order of 500 ppm ( average for about 6 measurements) in the raw gas,which is not too bad compared to a few grams per Nm^3 for some of the "commercial" gasifiers again.Based on these observations,I have formed the following tentative opinion.The known norms for SV are probably not valid for
1.open core downdraft designs
2.insulated fireboxes
3.multiple injections of air through nozzles
4.hot air injected into the combustion zone instead of ambient air.
>>> <Reedtb2@cs.com> 05/14/99 05:31PM >>>
Dear Vern, Darren and others:

Vern is asking exactly the right questions about the LeJeune gasifier. All
this sizing of gasifiers is expressed in the single number called
"SUPERFICIAL VELOCITY".

SV = Gas production (Nm3/s)/Cross section at grate or pyrolysis (m3)

The result is calculated in m/s, hence the name. If you don't know gas
production rate, SV can be calculated approx from thruput, since each kg of
biomass generates about 2.5 m3 of gas. SV is a measure of the intensity of
the pyrolysis and gasification reactions in the vessel.

I have long been generally aware of SV as a figure of merit for gasifiers.
In our 1988 "HANDBOOK OF BIOMASS DOWNDRAFT GASIFIER ENGINE SYSTEMS" there is
a table (p 36) of SV for five gasifiers then extant.

The SERI 1 ton/day gasifier (stratified downdraft design, uniform diameter)
was 0.28 and 0.24 m/s on both air and oxygen and was tarry. If we had known
what we know now we would have operated it closer to 1 m/s, 4 ton/day.
When Graboski scaled the SERI gasifier to 25 t/d it had a SV of 5.6 and 3.5
on air and oxygen respectively, outstanding. The Buck Rogers gasifier
operated at 0.13 to 0.23 m/s - and produced lots of tar, easily burned for
heat.

Unfortunately, SV it is ambiguous for WWII Imbert gasifiers with the conical
throat, so two numbers are given, one at the large diameter air inlet where
incoming wood is pyrolysed and some char is gasified, the other at the
pinched throat. The Imbert chosen was 0.63 and 2.5 m/s; the Biomass Corp.
was 0.24 and 0.95 m/s (John Goss - are you lurking out there?)
~~~~~
We are now engaged in further measurements of SV and will present a paper on
the results at the 4th Biomass of the Americas Conference, Aug. 29- Sept. 2
in Oakland, CA. We (Reed, Das, Ellis and Walt) find that SV is the main
control on tar and char production.

We believe that different species of biomass have different SV requirements
in a particular gasifier, depending on the use of the gas. Hard species
(pellets, nut shells, hardwoods) hold together during intense pyrolysis and
can produce very low tar gas, while softer species are carried away by the
gas stream.

We'd certainly appreciate any thoughts and questions on this topic while it's
hot. I would appreciate any data that you can send me on more current
gasifiers, dimensions, thruputs, tar and charcoal production rates. I will
keep them confidential or publish them as you wish. In particular send data
for the Camp LeJeune gasifier and I'll calculate for you. (Is air/fuel ratio
known?)

Yours truly, TOM REED
BEF

In a message dated 5/12/99 7:25:11 PM Mountain Daylight Time,
VHarris001@aol.com writes:

<< Dear Darren, others

Please don't misunderstand my intentions. I'm not trying to disparage the
Camp Lejeune Project. Quite the opposite, I'm interested in the Camp
Lejeune
Project because it is identical in nearly every aspect to a project I have
in
mind.

However, when I do calculations for sizing the gasifier for 2000 lbs/hr, I
generally arrive at a reactor diameter of about 2 feet (cross-sectional area
of 450 sq in) to achieve minimum tar production and maximum Btu gas for
internal combustion spark ignition engine consumption. As you know, this is
substantially smaller than the Camp Lejeune Gasifier. With a reactor
diameter of 7 feet, it has a cross-sectional area of 5540 sq in, a
cross-section more than 12 times greater that I would anticipate as optimal
sizing.

Concerns about tar output from the Camp Lejeune project were first raised
here by Doug Williams. While I am a rank amateur and much of the chemical
engineering is far beyond my capabilities, what few calculations I have done
regarding my own project leads me to speculate that the Lejeune project
produced considerably less permanent gas and considerably more condensates
and/or char than could be achieved with either a greatly increased gas
production level or a greatly decreased reactor diameter.

While I realize that all factors must be considered before an optimal
reactor
sizing can be accomplished, I find it incomprehensible that stratified
downdraft gasification of 2000 lbs/hr of 10% moisture content hogged wood
waste for use in a spark ignition internal combustion engine genset can be
done as suitably in a reactor 7 feet wide as in a reactor 2 feet wide, all
other things held constant. Either my calculations are very far off (which
wouldn't shock me) or the Camp Lejeune reactor can produce a great deal more
gas, and much cleaner to boot!

Was the Camp Lejeune project designed for 1000 scfm gas output or was it
anticipated that the project would be scaled up? I for one would very much
like to see the project run long term and have an opportunity to review the
results. I hope the project is restarted and they have an opportunity to
work with the "superficial velocity" of the project. Perhaps Tom Reed's
paper on the subject could have some influence on the Lejeune project.

Regards,
Vernon Harris
>>
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From vvnk at teri.res.in Fri Jun 25 06:07:55 1999
From: vvnk at teri.res.in (V V N Kishore)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: gasification of cotton stalks
Message-ID: <s773a28a.016@dakghar.teri.res.in>

We have used mustard stalks,which are very similar to cotton stalks in composition and shape,in our TERI gasifier for several years in a village.However,we used these in a briquetted form and not directly.In fact we could use seven different agro residues in briquetted form in the same gasifier.The briquettes were made in a screw extruder after adding cattle dung slurry as a binder to pulverised biomass.Briquetting consumed about 0.1 kWh/kg,which is 10% of the electricity produced per kg of stalks.

>>> Frederic Bourgois <bourgois@term.ucl.ac.be> 04/30/99 09:45PM >>>
Dear Gasifiermen,

Does anyone have information (bibliography, laboratory or in situ
experience) about gasification of cotton stalks in down-draft gasifiers ?
Is there technical limitations (size, ash composition or content, ...) ?

It seems that it is an important crops residue in developping countries
which has no real valorisation. If they can be used in gasifiers, cotton
stalks are a low cost biomass which could contribute to rural electrification.

Thanks for informations

Frederic

 

 

 

°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°
Frederic Bourgois
Project engineer

Université catholique de Louvain
Unite TERM - Groupe Energie Biomasse

2, place du Levant
B-1348 Louvain-la-Neuve
Belgique

tel: + 32-(0)10-47.83.98
fax : + 32-(0)10-45.26.92
http://www.meca.ucl.ac.be/term/geb/

°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°
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From VHarris001 at aol.com Fri Jun 25 10:11:04 1999
From: VHarris001 at aol.com (VHarris001@aol.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Kansas biomass project
Message-ID: <711bc673.24a4e845@aol.com>

Dear V V N Kishore,

If superficial velocity (or specific gasification rate) is not necessarily
well correlated to tar content, to what factors do you attribute low tar
production in your gasifiers? What factors do you believe would result in
low tar production in the stratified downdraft gasifier?

Thanks,
Vernon Harris

In a message dated 6/25/99 3:15:37 AM Eastern Daylight Time, vvnk@teri.res.in
writes:

> I believe that SV (or the related specific gasification rate expressed in
Nm^
> 3/cm^2 sec) is a good indicator for sizing the gasifier,but our experience
> shows that it need not correlate well with tar content.Our silk reeling
> gasifiers operate with an SV of 0.07 m/s and yet we dont have too much tar (
> the duct connecting the gas to the burner is cleaned once in a month,and I
> have seen so called commercial gasifiers which require cleaning of hot gas
> pipes every 48 hrs).Our power gasifiers operate with an SV of 0.27 m/s and
> produce tars of the order of 500 ppm ( average for about 6 measurements)
in
> the raw gas,which is not too bad compared to a few grams per Nm^3 for some
of
> the "commercial" gasifiers again.Based on these observations,I have formed
> the following tentative opinion.The known norms for SV are probably not
valid
> for
> 1.open core downdraft designs
> 2.insulated fireboxes
> 3.multiple injections of air through nozzles
> 4.hot air injected into the combustion zone instead of ambient air.
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From R.E.Sims at massey.ac.nz Mon Jun 28 16:44:51 1999
From: R.E.Sims at massey.ac.nz (Ralph Sims)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Pressurised downdraft gasification
In-Reply-To: <199906171548.QAA27483@cheviot.ncl.ac.uk>
Message-ID: <3.0.1.32.19990628220901.00739af8@mail.massey.ac.nz>

Hi,

I would be grateful to hear from anyone with any information on pressurised
downdraft gasifiers? I am aware of the modern pressurised fluidised bed
gasifier designs but, at a much smaller scale, has anyone any information
on pressurised downdraft designs, air blown, and even pressurised up to 5
or 10 atmospheres.

I believe there were such systems developed years ago but they had
explosion problems. However I have been unable to find any definitive
references either to their existence or to the design problems.

It is such a relatively simple concept that I cannot believe it hasn't been
thoroughly tested many times before.

With thanks

Ralph E H Sims

Director, Massey University Centre for Energy Research
Associate Professor, Sustainable Energy

Institute of Technology and Engineering
College of Sciences
Massey University
Private Bag 11222
Palmerston North
New Zealand

Tel: +64 (0)6 3505288
Fax: +64 (0)6 3505640
E-mail: R.E.Sims@massey.ac.nz

Home: +64 (0)6 3573257
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From joseph at slt.lk Wed Jun 30 04:29:21 1999
From: joseph at slt.lk (Joseph)
Date: Tue Aug 31 21:08:08 2004
Subject: No Subject
Message-ID: <08272920393108@eng.slt.lk>

We are a Government Institition engaged in R&D on renewable energy sources.
We are in need of casia siamea seeds to raise 7000 seedlings for to carry
out yield trials for short rotation coppice plantations. We shall be very
much thankfull to you, if you could send us very urgetly seeds adequate to
raise 7000 seedlings of casia siemea. Please help us.

Mr. P.G.Joseph
Director,
Alternative Energy Division
Ministry of Science and Technology
320, T.B.Jayah Mawatha,
Colombo 10,
Sri Lanka.

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From LINVENT at aol.com Wed Jun 30 08:41:26 1999
From: LINVENT at aol.com (LINVENT@aol.com)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Re: No Subject
Message-ID: <2a4b9c12.24ab6ac2@aol.com>

Mr. P.G.Joseph
Director,
Alternative Energy Division
Ministry of Science and Technology
320, T.B.Jayah Mawatha,
Colombo 10,
Sri Lanka.
Dear Mr. Joseph,
Could you please advise us of a common name of the seeds which you
are seeking? We may be able to secure them this way to start looking.
Our organization can assist in stimulating growth with concentrated
organic colloids, nutrients and hormones which dramatically increase the
growth rate, up to 100% under certain conditions. You may wish to look at
agronicinc.com website for this information. Are these plants being used for
renewable energy applications as fuel plants?
Sincerely,

Leland T. "Tom" Taylor
Agronics Inc.,
Thermogenics Inc.
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From arnt at c2i.net Wed Jun 30 20:20:27 1999
From: arnt at c2i.net (Arnt Karlsen)
Date: Tue Aug 31 21:08:08 2004
Subject: GAS-L: Reactor Pressure - was To Tuyere or Not to Tuyere
In-Reply-To: <c5859df2.249f2871@aol.com>
Message-ID: <377AA8DE.C46F4EF7@c2i.net>

Vern et al,

Sorry for beeing slow responding this time, politics, for those
interested, see http://home.c2i.net/arnt/krig.html on why the Church of
Serbia, _may_ save _my_ bacon...

..also, I hope to be taking pictures and finish some promised work on
both the gasifier and on CO gas medicine, to the web.

VHarris001@aol.com wrote:
>
> Dear Arnt,
>
> Thanks for your responses to my posts. There were several questions I have,
> but it sometimes takes me a while to figure out just what the questions are.
>
..only proves wise brain use. The box is simple, what happens inside,
is not.

> You state that the syngas yield will increase by keeping the reactor vessel
> pressure as low as possible. I've heard that before and seen it being asked
> on the list before. However, I don't understand how that would be. I must

..Chateliere???'s Law: we have a set number of atoms in more or less
complex molecules, the simplest two active beeing H2O and CO2 leaving
the combustion zone. Out of these two, we make the simpler CO and H2,
by adding heat and one C, yielding 2CO and H2.

..now, in the same space we _had two_ gas molecules,we _now have three_
gas molecules, which means either/both volume or/and pressure increases
by ~50%, and, we have swallowed a lot of heat, from the glowing
catalysing char bed in the reduction zone.

..the glowing catalysing char bed lowers the reaction energy thresholds
and kicks reactions back and forth to find the most stable state
throughout thru the bed, of course this stable state varies thru the
bed, and will reverse between 800 and 400oC and at hich pressures.
Those of you owning Gengas, look up Chapter 2, figures 21 and 22 and
table 7 on the effect of removing the grate charcoal, or DL some of the
chemistry modelling SW at tucows.com or linuxberg.com and play with the
numbers, to see these effects.

..so, to maximize syn gas yield, we keep the pressure _low_ and the
_temperature high_, in the reduction zone.

..unfortunately, this means the pressure is also low in the rest of the
gasifier, most significantly in the combustion zone, where we like to
see a certain _amount_ of stochiometric combustion take place. This
require air or O2 _dosing_, and it still remains pretty slow.

..and we like to see it happen in a certain _place_, the combustion
zone. Here, we like to have the air starved combustion "climb upstream"
thru the fuel to the air source, the nozzles.

..now, since we can't provide the high pressure O2 or air liked by the
combustion, we do not the next, but the very best thing, dose in low
pressure air at high speed to match the Wrath of the Fire Gods, who
brutally slam in air into the char bed, solving both our two problems.

..so we like to use the pressure drop _across the nozzles_, to build
incoming airspeed. And then use that resulting low pressure as above to
maximize syngas yield. Backwards reasoning, yeah.

> be missing something. I understand that the fuel will react differently to
> the pressure drop across the fuel bed, but that is a difference in the

..I do not like _fuel bed_ pressure drop. Tuyere pressure drop and to a
lesser degree, reduction zone pressure drop, do something useful, which
must be balanced against pumping gas out of the gasifier.

> pressures at inlet vs outlet points rather than an absolute pressure
> measurement. If the pressure drop is 1 psi across the fuel bed, what
> difference would it make if the inlet pressure was 1 psig and the outlet
> pressure was 0 psig over - say - the inlet pressure being 10 psig and the

..none, other than the reduction zone chemistry.

> outlet pressure being 9 psig? It seems to me the key issue is the velocity
> of air into the reactor and gas out of the reactor rather that minimizing the
> absolute pressure of the system. Further, other than mechanical restrictions
> of gas flow such as tuyeres, throats, grate design, etc. the pressure drop
> across the fuel bed needed to obtain the required superficial velocity will
> be a function of the nature of the fuel itself. Thus the fuel grinding and
> metering requirements you mention.

..the key issue in tuyeering, is _combustion control_. We want to:
1. minimize air use
2. minimize fuel preparation
3. make the best possible use of both to
4. make as good and much gas as possible from the above.

..every thing else kept equal, bottom line is, the more incoming air
speed, the more Fire God Wrath.
>
> If you could further delineate this point, particularly the role of tuyeres
> in maintaining a hot zone with low pressure, it would be helpful.
>
> Thanks,
> Vernon Harris
>
> In a message dated 5/28/99 7:32:40 PM Eastern Daylight Time, arnt@c2i.net
> writes:
>
> > .sure. Now reviewing the governing chemistry involved, you will learn
> > you increase syngas yield by keeping the reactor vessel pressure as
> > _low_ as possible, which will harm combustion. There are other dirty
> > tricks such as feeding oxygen, propane or syngas flaring, _grinding and
> > metering_ the fuel feed or use a multi stage reactor system.
> >
> > You will want to _precisely_ control the reduction zone conditions, you
> > want to keep it hot _enough and at a low enough_ pressure to maximize
> > syngas yield.
> > The _cost-effective_ way to do this is tuyeering, which can be tweaked
> > minimizing air feed, maximizing air jet speed, and recycling exhaust gas
> > thru 'em.

..down here I should have said "recycling _hot_ engine etc. exhaust
gas"...

--..Arnt
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