[Gasification] Gasification Digest, Vol 3, Issue 14

Mon Nov 29 15:57:50 CST 2010

Gas turbine, reciprocating engine, steam turbine. Differences depends among
other thins on the possible maximum temperatures of the working medium in
each process and that depends on the materials used. Another important thing
is internal friction in reciprocating engines and gas leakages in turbo
compressors gas turbines and steam turbines and those leakages are
relatively seen much higher in small machines unless you make them for
extremely high speed. However one of the real great problems is as usual tar
and ash. Tar will get stuck on the blades of turbo compressors used for gas
turbines and some high performance reciprocating engines so that the
performance will become worse. Ash could melt and stick to the turbine
blades of gas turbines. In addition there are thermal losses in the
gasification process and any cleaning of the gas and those losses are not
smaller than the losses in wood fired steam process. So the total result is
that for small plants it is seems more efficient to use rather robust and
simple reciprocating engines without compressors and for bigger and large
plants (multi MW)one could just as well burn the wood in boilers. Another
ting to remember is that for small gas turbines with moderate compression
ratio it might be necessary to use heat exchangers to recover heat between
the expanded but still hot exhaust gas and the compressed combustion air.
A comparably big wood gasification - 18 MW - plant was built and tested at
Varnamo in Sweden during the 1990-ies. It was quite advanced with a
combi-process which means a gasturbine folloved by a steam plant with a
steam turbine. In order to make it less sensitive to impurities in the gas
they used a reciprocating compressor as far as I remember. Today this plant
has been rebuilt to become a research center for biomass gasification and
the aim is to learn more about gasification and production of biofuels to
replace gasoline and dieseloil. You can check their homepage at www.vvbgc.se

Regards
Bjorn Dahlroth

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Ämne: Gasification Digest, Vol 3, Issue 14

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Today's Topics:

   1. Re: Combustion vs. gasification (Robert Kana)
   2. Re: Combustion vs. gasification (Kevin)
   3. Re: Combustion vs. gasification (jleach at danatech.net)

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Message: 1
Date: Mon, 29 Nov 2010 10:26:57 +0700
From: Robert Kana <sinan at biomassindo.com>
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] Combustion vs. gasification
Message-ID: <4CF31D81.2090907 at biomassindo.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

Good morning,
Does anybody know any scientific comparison between combustion and 
gasification? Argument is that  wood chips fired steam boilers and 
turbines are more efficient than syngas fired duel fuel diesel 
generators. Any manufacturer has gas turbines small enough to use in 2 
MW power generating? Thanks in advance,
Robert Kana, Biomass Energy Indonesia

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

Message: 2
Date: Mon, 29 Nov 2010 01:34:24 -0400
From: "Kevin" <kchisholm at ca.inter.net>
To: "Discussion of biomass pyrolysis and gasification"
	<gasification at lists.bioenergylists.org>
Subject: Re: [Gasification] Combustion vs. gasification
Message-ID: <D4ADA77F37E449379FD0B2DACA8EBA68 at usera594fda0bf>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
	reply-type=response

Dear Robert
----- Original Message ----- 
From: "Robert Kana" <sinan at biomassindo.com>
To: <gasification at lists.bioenergylists.org>
Sent: Sunday, November 28, 2010 11:26 PM
Subject: Re: [Gasification] Combustion vs. gasification

> Good morning,
> Does anybody know any scientific comparison between combustion and 
> gasification?

Combustion is the purposeful burning of a fuel, while gasification is the 
conversion of a solid or liquid fuel into a fuel gas, for subsequent 
combustion.

Argument is that  wood chips fired steam boilers and
> turbines are more efficient than syngas fired duel fuel diesel generators.

# "Syngas" is generally intended to mean "a gas mixture used for the 
synthesis of another product." The term is often used very loosely... "wood 
gas" is generally not "synthesis gas", because of contained impurities and 
dilutent nitrogen. The arguement presented above is likely wrong, in that a 
"syngas" would have a definite composition, and would likely permit better 
combustion efficiency than would wood chips, that can vary significantly in 
moisture content. Ask teh presenters of that arguement to clearly define 
"efficiency", and ask them to support their claim with a technically valid 
arguement.

Best wishes,

Kevin Chisholm

 Any manufacturer has gas turbines small enough to use in 2
> MW power generating? Thanks in advance,
> Robert Kana, Biomass Energy Indonesia
>
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------------------------------

Message: 3
Date: Mon, 29 Nov 2010 05:57:46 +0000
From: jleach at danatech.net
To: "Discussion of biomass pyrolysis and gasification"
	<gasification at lists.bioenergylists.org>
Subject: Re: [Gasification] Combustion vs. gasification
Message-ID: <W9789176178661291010266 at webmail8>
Content-Type: text/plain; charset="us-ascii"

Robert,
>From our work on this subject, the gasification/Otto cycle is the most
efficient for small and medium sized facilities, The efficiencies converge
as the plants get bigger. We have looked at the Diesel cycle via dual fueled
engines but there is no experience on this combination for producer gases.
For gases from pyrolysis, the experience is still very limited. It can be
done if you use enough Diesel fuel, but it might not be cost effective. The
most experience is with Otto cycle configurations, but even that is limited.
Advantage of the steam cycle is that is proven. But efficiency is lower.

For 2MW gas turbine, I would recommend an older version of the Solar Centuar
40. They would be about 2 MW at site conditions. Try the Woods Group as a
source for these machines.

Best Regards,
Jim Leach, P.E.

-----Original Message-----
From: Robert Kana [mailto:sinan at biomassindo.com]
Sent: Sunday, November 28, 2010 07:26 PM
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] Combustion vs. gasification

Good morning, Does anybody know any scientific comparison between combustion
and gasification? Argument is that wood chips fired steam boilers and
turbines are more efficient than syngas fired duel fuel diesel generators.
Any manufacturer has gas turbines small enough to use in 2 MW power
generating? Thanks in advance, Robert Kana, Biomass Energy Indonesia
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End of Gasification Digest, Vol 3, Issue 14
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