GAS-L: Turbine fired by woodchips

[Joel Florian <joflo@yifan.net>]

Dear Harmon (and those who might be interested),

You asked if anyone has tried running wood  gas through a turbine without 
filtering or cooling.

I have  on my desk a paper titled "Ash Deposition in a Wood-Fired Gas 
Turbine" by K. W. Ragland, M.K. Misra, D. J. Aerts, C. A. Palmer.  From the 
Department of Mechanical Engineering, University of Wisconsin -- Madison. 
This was graciously sent to my by Dan White of 
http://www.geocities.com/ufoengines/.

The abstract reads as follows:

"A small four-stage gas turbine was directly fired with woodchips using a 
novel downdraft, gravel-bed combustor for a total of 250 hours of 
tests.  The average turbine blockage due to deposits was 0.19 percent per 
hour.  The composition of deposits was studied using plasma emission 
spectroscopy and x-ray diffraction.  The main consituents of the deposits 
were CaO, Mgo, and K2SO4.  The deposits contained 5 to 15 percent potassium 
and  0.5 to 3 percent sulfur."

Excerpts from the intro :  "A combined gas turbine-steam turbine cycle is 
thermodynamically more efficient than the steam turbine alone as a source 
of electricity and heat.  Direct firing of a gas turbine with biomass is 
potentially more cost effective than indirect firing using a heat 
exchanger, or gasification of biomass prior to combustion.  Although 
considerable work has been doen on deposits from coal-fired gas turbine 
combustors (Logan et al., 1990; Spiro et al., 1987, 1990 Wenglarz and Fox, 
1990), little work has been reported on deposits from wood-fired gas 
turbine combustors....  A novel gravel-bed, downdraft combustor for a 
direct-fired biomass gas turbien cycle is being developed (Ragland and 
Aerts, 1992, 1989; Ragland et al., 1991).  The combustor is designed to 
promote intense combustion in a thin zone and to control particulate growth 
by using high excess air...."

Salient points from the body: 2cm woodchips fed from lock hopper into a 
combustor fed with air pressurized approaching 5 atm.  Outlet temp held to 
900 C by excess air.  Turbine rated at 400 hp @ 51000 rpm.  Run at 80 % 
speed with net power of 75 hp or less.  Bearings failed because some of the 
refractory gravel got into the turbine.  5400 kg of yellow poplar chips and 
370 kg of aspen were burned during the tests


Conclusion:  A four-stage Allison 250-C20B gas turbine was run at low power 
on woodchips for 130 hours of tests.  inspected and cleaned and run for 
another 122 hours using a direct fired gravel bed combustor.  The deposits 
were 1mm to 1.6 mm thick on the nozzles and 0.1 to 0.5 mm thick on the 
rotors.  The average turbine blockage was 0.19 percent per hour.  the main 
deposits were calcium oxide, magnesium oxide, and potassium 
sulfate.  Although the potassium content of the wood was 0.1 percent and 
sulfur content was only 0.007 percent potassium and sulfur play an 
important role in formation of deposits on the turbine nozzles and 
rotors.  Further work is needed to determine the extent to which hot gas 
cleanup may be required between the combustor and turbine when using 
woodchips."

Interesting -- but not enough of  a resounding success to change state of 
the art......

Joel Florian.
Happily burning spruce sawdust in Alaska


At 11:24 AM 6/26/02 -0500, you wrote:
>    I think what Doug means is that we have a gas-l list and a stoves list,
>people who want to discuss either should do so on the appropriate list, we 
>don't
>want the gas-l list to become the stoves list. I'm on both, both are good, but
>different.
>    However, Tom brings up another point that is of great interest to me. I've
>been looking seriously at building a Tesla turbine to be fueled by woodgas
>and/or steam. On another list, someone working with the Tesla turbine said 
>they
>didn't see any need for either cooling or filtering woodgas before feeding 
>it to
>the turbine, although they did think that perhps steam could be created in the
>gasification process or along with it and fed with the woodgas. Has anyone 
>tried
>this with *any* sort of turbine? As Toms says, this seems to be a much more
>efficient use, at least in stoves.
>    I understand why it needs to be both cooled and filtered for an IC piston
>engine -- does this also hold true for turbines?
>
>
>On Wed, Jun 26, 2002 at 10:26:28AM -0600, Tom Reed wrote:
> > Dear Doug and All:
> >
> > Doug's opinions below form the basis for an important discussion - "when is
> > gasification really just combustion".  There is in fact a continuum of
> > operation between pyrolysis, gasification and combustion at both the
> > microscopic and macroscopic level. The exact boundary can't be nailed down
> > exactly, but it is important for all of us to understand the issues. I have
> > seen drag racers recently with flames coming out their exhaust pipes.
> > However, I don't think I want to call them "gasifiers".
> >
> > Doug seems to be saying below that if you pipe the gas created by partial
> > combustion (in a downdraft or inverted downdraft or fluidized bed or 
> updraft
> > "gasifier") to a separate device (engine, burner, chemical process) you 
> have
> > a "true" gasifier; if you burn it immediately in close coupled mode it is
> > not really a gasifier at all.  While I see some basis for this claim I 
> don't
> > agree.
> >
> > In our WoodGas stoves partial combustion gas is generated by flaming
> > pyrolysis in a zone 2-3 cm thick down inside the bed.  The gas then passes
> > through a layer of characol which converts more of the gas to CO and H2.
> > The gas that issues from the charcoal many cm above the flaming pyrolysis
> > zone is then burned immediately.  However, we could easily add a 6 inch 
> or 6
> > foot chimney and inject air at the top for very similar combustion.  By
> > Doug's thinking the first would be a combustor and the 2nd and 3d would be
> > gasifiers.
> >
> > In the U.S. the difference between combustion and gasification  has become
> > formalized in the laws relating to incentive credits for gasifiers that
> > don't apply to combustion.  I have been involved in helping write the legal
> > definitions.  Something like.."If you can establish a level BETWEEN the
> > gasifier zone and the combustion zone at which a gas sample will have an
> > energy value of more than 2 MJ/scm (50 Btu/scf) it is a close coupled
> > gasifier/combustor combination".  If not, not.  Since $$$ are involved, 
> this
> > is obviously an important definition.
> >
> > The close coupled gasifier/combustor combination has a number of 
> advantages.
> > Optimal gasification of bone dry wood puts 17.8 MJ/kg into chemical energy,
> > but still leaves 3.3 MJ/kg in the sensible heat of the ~750 C gas 
> coming off
> > the charcoal pile.  If this is burned immediately you can approach 100%
> > efficiency in the gas conversion.  If you have to cool the gas to room
> > temperature you lose 16% of the energy to coolant.  Furthermore, close
> > coupled combustion burns all the volatile tar vapors up.  Finally close
> > coupling saves space and our 1.5 V WoodGas CampStove is only 7 inches tall
> > and 5 inches in diameter.
> >
> > So, I will restate that if you have producer gas in a section of the unit,
> > it is a close coupled gasifier/combustor.
> >
> > Yours truly,                                TOM REED            BEF 
> GASWORKS
> > ----- Original Message -----
> > From: "Graeme Williams" <graeme@powerlink.co.nz>
> > To: <gasification@crest.org>
> > Sent: Wednesday, June 26, 2002 2:36 AM
> > Subject: GAS-L: Small Scale Gasifiers
> >
> >
> > > Dear Gasification Colleagues,
> > >
> > > It is easy to understand the confusion that exists about gasification 
> in a
> > > general sense as the phenomenon can be found anywhere you create fire.
> > > However, for this interest group to include gasifying stoves is in my
> > > opinion incorrect, as they should be identified by their correct name of
> > > double burning or smokeless stoves which commercial manufacturers call
> > them,
> > > and as such stay in the stoves forum.
> > >
> > > For people researching gasification and interested in using gas to use
> > > separately for whatever end use, this is the one group who can offer the
> > > most assistance and information on the subject, particularly if it is for
> > > engine applications.  Those of us who actually work in this field of
> > > technology have made a commitment to see gasification fulfill an 
> important
> > > role as a source of renewable energy and chemical feedstock.  To cross
> > > pollinate gasification with close coupled combustion, then discuss
> > adapting
> > > these stoves for engines is less than helpful to those who seek accurate
> > > information about gasification.
> > >
> > > While it might be important for individuals to buy a small gasifier, 
> it is
> > > equally important for the manufacturer to find enough individuals to
> > create
> > > a market.  Then, instead of saying how much are small gasifiers, ask
> > > yourself - how much am I prepared to pay for one.  This is a valid
> > question,
> > > so state your financial ability to pay for your commitment to renewable
> > > energy.
> > >
> > > Alternatively, decide on a size (discuss it with a manufacturer first),
> > get
> > > a quote and order 50.  Then onsell to those who just want one unit.  If
> > this
> > > isn't a solution for you specifically, then you have to accept that the
> > only
> > > way to own one, is to build it yourself.  Since I posted the design for a
> > > small gasifier on the Fluidyne Archive last year,nobody on this list has
> > > written to me saying "I'm ready to go, what's next?"
> > >
> > > Last August in Northern Ireland, two French engineering students working
> > at
> > > ITI (Innovation Technologies Ireland) built one out of salvaged scrap
> > steel
> > > and I shared their excitement of having it flaring gas within 3 
> minutes of
> > > ignition.  I'll see if I can find the photographs and ask Graeme to put
> > them
> > > up on the Fluidyne Archive - www.fluidynenz.250x.com.  This will take a
> > > couple of days.
> > >
> > > Gasification is very addictive and a lot of fun . . . so let's discuss
> > > making gas and not heat, unless it's burning gas!
> > >
> > > Doug Williams
> > >
> > >
> > > -
> > > Gasification List Archives:
> > > http://www.crest.org/discussion/gasification/200202/
> > >
> > > Gasification List Moderator:
> > > Tom Reed, Biomass Energy Foundation,  Reedtb2@cs.com
> > > www.webpan.com/BEF
> > > List-Post: <mailto:gasification@crest.org>
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> > >
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> > > -
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> > > http://www.bioenergy2002.org
> > > 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
> > >
> > >
> >
> >
> >
> > -
> > Gasification List Archives:
> > http://www.crest.org/discussion/gasification/200202/
> >
> > Gasification List Moderator:
> > Tom Reed, Biomass Energy Foundation,  Reedtb2@cs.com
> > www.webpan.com/BEF
> > List-Post: <mailto:gasification@crest.org>
> > List-Help: <mailto:gasification-help@crest.org>
> > List-Unsubscribe: <mailto:gasification-unsubscribe@crest.org>
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> >
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> > -
> > Other Gasification Events and Information:
> > http://www.bioenergy2002.org
> > 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
>
>--
>Harmon Seaver
>CyberShamanix
>http://www.cybershamanix.com
>
>-
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>
>Gasification List Moderator:
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>www.webpan.com/BEF
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>
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>-
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>http://www.crest.org/articles/static/1/1011975672_7.html Carbon


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