[Gasification] W-Gas and P-Gas defined

Tom Miles tmiles at trmiles.com
Sat Dec 10 08:26:44 CST 2011

Tom Reed,

For a start, has a laboratory characterized the gas and charcoal from
pyrolytic gasification and compared it to "wood gas" or char from pyrolysis
or gasification? I have not seen data plots from a gas analyzer on a TLUD or
full characterization of the gases, tars or chars. 


Tom Miles

-----Original Message-----
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Thomas
Sent: Saturday, December 10, 2011 5:34 AM
To: Discussion of biomasspyrolysis and gasification; Hugh McLaughlin; Paul
Anderson; William Ayres; Kathy Nafie; Jim Fournier; Mukunda HS
Subject: [Gasification] W-Gas and P-Gas defined

Dear Gasification list

Well defined terminology is fundamental to a discussion of the science and
praxis of any subject.   I am proposing two new words for the different
gases we make.  They will help clarify  discussions we have and will have
here at the "Discussion of biomass pyrolysis and gasification " list.  

These are proposals, and I hope they will spark a discussion of this and
other terms that have grown up helter skelter.  We welcome alternate


WOODGAS is a term I have been using for thirty years.  In German it is
Holzgaz, an exact translation, holz being the German name for wood.  It
refers to the gas made in gasifiers that completely convert wood to
combustible gas, often for use in IC engines.  It is the name of our website
where we sell books on gasification and Woodgas cookstoves.

For this discussion and others, I propose the abbreviation "W-Gas".

Wood is composed of ~20% lignin and ~80% cellulose (cellulose plus
hemicellulose). On heating in the absence of air, the cellulose produces
mostly the Woodgas, while the lignin is converted to charcoal.  Since the
lignin is the principal source of tars in Woodgas (up to 2% by weight of the
wood) tar removal is a very big problem for using W-gas in engInes.  


More recently (starting in 1985)  we have developed a new form of "PYROLYTIC
gasification" in which air is admitted to a dense bed of wood pellets, chips
or sticks, forming an auto pyrolysis zone passing up or down through the bed
and burning a small fraction of the pyrolysis gas to convert the remaining
cellulose to a combustible gas which can be used for cookstoves and charcoal
generation. Paul Anderson has dubbed the stoves "TLUD, Toplit Updraft"

The TLUD gas composition has not been well characterized yet, but I'm hoping
someone will do so soon (possibly me). ( In an attempt to measure tar, I
condensed about 1/2 % of a non sticky grey soot in a four foot X 4"
galvanized stove pipe.). 

I propose the name "P-Gas" for the gas made from mostly the cellulose in
this process.

(Incidentally, the charcoal made in this 600-800C process is significantly
different from conventional charcoal, and has much less tar and much higher
absorption properties.  It could be called PG- (PYROLYTIC gasification)
charcoal. )


I hope that this will spark a discussion of this and other terminology used
in this list.  Since Tom Miles is the moderator of this list, I'd like to
appoint him as the final arbiter of terminology for the list.

Dr Thomas B Reed 
The Biomass Energy Foundation
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