Re: "Pyrolysis gas" energy content and composition

["Tom Reed" <tombreed@attbi.com>]

Dear Jim and All:

I agree with Jim's comments and am posting them to those of you trying to
make sense of the science here.

Jim:  Are you a member of CREST.org GASIFICATION?  I doubt it, but we miss
you here....

TOM

----- Original Message -----
From: "Jim Diebold" <jdiebold@gocpc.com>
To: "Tom Reed" <tombreed@attbi.com>
Sent: Saturday, October 19, 2002 11:28 AM
Subject: Re: "Pyrolysis gas" energy content and composition


> >Dear Tom:
>
> I agree qualitatively with your comments, but would add that pyrolysis gas
made by
> indirectly heating the biomass results in the highest heating value, due
to the absence
> of added nitrogen to the offgases.  In addition, if fast pyrolysis is
used, there can be
> up to about 15% hydrocarbons, e.g., methane, ethane, ethylene, propylene,
butenes, etc.
> in the gases which significantly increase the volumetric heating value.
These
> hydrocarbons are formed by endothermically cracking of the primary oil
vapors, so if the
> gas is used without condensing the tars only a little is gained by
cracking them.
>
> On the negative side, do not forget to include the water vapor present in
the producer
> gases when you calculate the heating value for an actual application.  The
water content
> is easily calculated by assuming the producer gas is saturated at its
lowest temperature
> in the gas cleanup train (assuming a condensing gas-cooling system), or by
measuring the
> dew point of the gases.   I suspect that it is common practice to ignore
the water vapor
> present in producer gases which inflates the heating value, when most
people speak of the
> heating value and try to compare different producer-gas systems.
>
> Jim Diebold
>
>
>
>
>
> Dear Paul, Andrew and All:
> >
> > I agree "vegie-gas" is cute, but it is nice for all of us to be on the
same
> > page and not invent new words if old words exist and are widely used and
> > understood.
> >
> > I wouldn't agree that the "inverted downdraft" type of gasifier doesn't
> > produce producer gas, since "producer gas" can cover a multitude of
sins,
> > but mostly indicates a 5-7 MJ/m3 gas with ~ 50% nitrogen.
> >
> > If you would like to be more accurate, I would propose the terms
> >
> > "Pyrolysis gas" - made from the volatiles of the biomass, but leaving
the
> > charcoal as a by-product
> >
> > It is difficult to characterize the energy content of the gas because if
you
> > cool it you will find a high proportion of "tars".  The hot gas has all
the
> > energy value of the tars, typically much greater than the CH4, H2 and
CO.
> > The tars are the condensible component and quite high with low volume.
The
> > gas has a relatively low nitrogen content, since it only takes 0.5 to
1kg of
> > air to pyrolyse 1 kg of biomass, while it takes 1.5 kg of air to
completely
> > gasify dry biomass.  I would like to measure this more accurately
someday
> > and hope we might do it at CPC.
> >
> > I would appreciate comments from Jim Diebold, a long time pyrolyser at
NREL,
> > now at CPC.
> >
> > Yours truly,
> >
> > TOM REED              BEF
> >
> >
> >
> >
> > > Andrew,
> > >
> > > Thanks for your informative reply.  (I did not see it before my
previous
> > > message.)  YOU and a few others can get the highest scores.  People
like
> > me
> > > need the tutoring!!!
> > >
> > > I will leave "zoomass" to others, but wonder if sewerage (and dung and
> > > feces) is "zoo- or phyto-"   (Not a topic for this list serve.)
> > >
> > > Thanks for the clarification about producer gas and water gas.
Clearly
> > the
> > > "very small gasifiers" such as mine do NOT yield producer gas.
> > >
> > > Is it acceptable to use the term "wood-gas" if the phyto-mass is
actually
> > > corn cobs or other clearly NON-wood material?   Is the gasification of
> > > straw (being discussed currently) producing "wood-gas"?   If we start
> > > speaking of phyto-gas (or "fito-gas" in many of the Romance
languages), we
> > > should be clear that we include "wood-gas" and other
> > > "dry-vegetative-matter-gas".
> > >
> > > :-))  No interest in the term "vegie-gas"?    I thought it was cute.
> > >
> > > Thanks again.
> > >
> > > Paul
> > >
> > > At 12:10 AM 10/18/02 +0100, AJH wrote:
> > > >On Tue, 15 Oct 2002 16:22:22 -0500, "Paul S. Anderson" <psand
> > > > >
> > > > >1.  Can regular biomass (I am not referring to the charcoal that is
a
> > stage
> > > > >of biomass consumption) be consumed in fire ***without first
undergoing
> > the
> > > > >release of the gases (pyrolysis and gasification)*** that are
> > subsequently
> > > > >combusted when mixed with oxygen and sufficient ignition?
> > > >
> > > >Possibly if burned as a fine powder the combustion would be so short
> > > >that there would be no way of separating the reactions.
> > > >
> > > > >  In other words,
> > > > >even in a regular "fire" of biomass, is it not true that the gases
are
> > > > >created first, even if the gases are almost immediately "burned"?
> > Hence,
> > > > >there is no "fire" without gasification first.
> > > >
> > > >OK in general
> > > >
> > > > >
> > > > >If yes to the above, then all stoves COULD be considered to be
> > gasifiers,
> > > > >and we therefore need to clarify that what we have been calling
> > "gasifier
> > > > >stoves" are ones in which ***the creation of the gases takes place
in a
> > > > >location at least slightly and control-ably removed in space and in
> > time
> > > > >from the point of the combustion of those gases***.
> > > >
> > > >I think this is the distinction that has been made in the past.
> > > > >
> > > > >2.  What are the real differences between "producer gas" and
"wood-gas"
> > and
> > > >
> > > >Producer gas is generally taken to be CO and Nitrogen formed by the
> > > >gasification of carbon by air, water gas is H2 and CO formed by the
> > > >gasification of carbon by steam. Woodgas is a mixture of these
> > > >reactions and chemicals plus the pyrolysis (offgas) products of
> > > >thermal decomposition, it contains many compounds ranging from weak
> > > >organic acids, alcohols etc through to tars as vapours. Gasifiers
> > > >making gas for other than thermal uses attempt to "crack" these
> > > >pyrolysis compounds thermally to reduce them to simple gaseous
> > > >compounds.
> > > >
> > > > >pyrolysis / gasification of any DRY plant-origin biomass.
> > > >
> > > >This is phytomass whether wet or dry.
> > > >
> > > > >  (We do not do
> > > > >much gasification of dry animal-origin biomass.)
> > > >
> > > >This is zoomass and yes we do, there is much discussion on GAS-L of
> > > >sewage sludge gasification. I suspect one of the most successful
> > > >gasifiers operating is in a chrome leather works where the off cuts
> > > >are recycled as heat and the chromium is recovered commercially from
> > > >the ash.
> > > >
> > > > >
> > > > >Paul S. Anderson, Ph.D.,  Fulbright Prof. to Mozambique
> > > >
> > > >How many marks out of ten do I score teach :-)?
> > > >
> > > >AJH
> > > >
> > > >-
> > > >Stoves List Archives and Website:
> > > >http://www.crest.org/discussion/stoves/200209/
> > > >http://crest.org/discussiongroups/resources/stoves/
> > > > >
> > > >Stoves List Moderators:
> > > >Ron Larson, ronallarson@qwest.net
> > > >Elsen L. Karstad, elk@wananchi.com www.chardust.com
> > > >
> > > >Other Biomass Stoves Events and Information:
> > > >http://www.crest.org/articles/static/1/1010424940_7.html Bioenergy
> > > >http://www.crest.org/articles/static/1/1011975339_7.html Gasification
> > > >http://www.crest.org/articles/static/1/1011975672_7.html Carbon
> > > >
> > > >List-Post: <mailto:stoves@crest.org>
> > > >List-Help: <mailto:stoves-help@crest.org>
> > > >List-Unsubscribe: <mailto:stoves-unsubscribe@crest.org>
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> > > > >
> > > >For information about CHAMBERS STOVES
> > > >
> >
>http://www.repp.org/discussiongroups/resources/stoves/Chambers/Chambers.htm
> > >
> > > Paul S. Anderson, Ph.D.,  Fulbright Prof. to Mozambique 8/99 - 7/00
> > > Rotary University Teacher Grantee to Mozambique >10 mo of 2001-2003
> > > Dept of Geography - Geology (Box 4400), Illinois State University
> > > Normal, IL  61790-4400   Voice:  309-438-7360;  FAX:  309-438-5310
> > > E-mail: psanders@ilstu.edu - Internet items: www.ilstu.edu/~psanders
> > >
> > >
> > > -
> > > Stoves List Archives and Website:
> > > http://www.crest.org/discussion/stoves/200209/
> > > http://crest.org/discussiongroups/resources/stoves/
> > > >
> > > Stoves List Moderators:
> > > Ron Larson, ronallarson@qwest.net
> > > Elsen L. Karstad, elk@wananchi.com www.chardust.com
> > >
> > > Other Biomass Stoves Events and Information:
> > > http://www.crest.org/articles/static/1/1010424940_7.html Bioenergy
> > > http://www.crest.org/articles/static/1/1011975339_7.html Gasification
> > > http://www.crest.org/articles/static/1/1011975672_7.html Carbon
> > >
> > > List-Post: <mailto:stoves@crest.org>
> > > List-Help: <mailto:stoves-help@crest.org>
> > > List-Unsubscribe: <mailto:stoves-unsubscribe@crest.org>
> > > List-Subscribe: <mailto:stoves-subscribe@crest.org>
> > > >
> > > For information about CHAMBERS STOVES
> > >
> >
>http://www.repp.org/discussiongroups/resources/stoves/Chambers/Chambers.htm
> > >
> > >
> >
> >
> >
>



-
Stoves List Archives and Website:
http://www.crest.org/discussion/stoves/200209/
http://crest.org/discussiongroups/resources/stoves/
>
Stoves List Moderators:
Ron Larson, ronallarson@qwest.net
Elsen L. Karstad, elk@wananchi.com www.chardust.com

Other Biomass Stoves Events and Information:
http://www.crest.org/articles/static/1/1010424940_7.html Bioenergy
http://www.crest.org/articles/static/1/1011975339_7.html Gasification
http://www.crest.org/articles/static/1/1011975672_7.html Carbon

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>
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