[Gasification] the most important thing (quitepossibly) i'velearned to date

Tue Oct 19 03:14:42 CDT 2010

Dear Kevin,

It is the Second Law that I refer to. In simple terms it states that entropy
will never decrease (spontaneously) within a given system. So while there
may be a way of recovering, say, "waste heat" from a process, no
re-formulation of the process will make the end products more energetic than
they were in their native, unreacted state. I am quite certain that you will
not find this simplified expression worthy of argument (or will you?).

Very best regards,

Mark

From: Kevin [mailto:kchisholm at ca.inter.net] 
Sent: Monday, October 18, 2010 9:08 PM
To: mark at ludlow.com; Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] the most important thing (quitepossibly)
i'velearned to date

Dear Mark

----- Original Message ----- 

From: Mark Ludlow <mailto:mark at ludlow.com>  

To: 'Discussion of biomass pyrolysis
<mailto:gasification at lists.bioenergylists.org>  and gasification' 

Sent: Monday, October 18, 2010 4:48 AM

Subject: Re: [Gasification] the most important thing (quitepossibly)
i'velearned to date

Hi Kevin!

Second Law! Energy is not "created" by the reaction. It already exists in
the individual components of the reaction.

# Very interesting comment! However, I think you are inferring that my
questions are an attempt to violate the First Law, and not the Second. The
First Law relates to the balance between mass and energy in a reaction. It
can be simply stated as:

"First Law: You can't get something for nothing."

The Second Law deals with randomness and disorder, and the impossibility of
getting a perfect reaction. It can be stated equally simply as:

"Second Law: As a matter of fact, you can't break even."

# My question deals with how to set up the reaction so that with a given
amount of chemical energy in the feed input, the use of energy content of
the output gas is maximized.  

Kevin, you can answer your own question. 

# I think you might have missed the significance of my question. What do you
think my question was?

The only excess "free" energy is that which is expressed as sensible and
latent thermal energy of the gaseous output (however: we cool gases for
greater volumetric efficiency in UC engines, etc.). 

# No. The excess "fee energy" that would otherwise be wasted includes:

1: The sensible and latent energy in teh gasifier output product gas.

2: The sensible and latent heat in teh engine exhaust after teh fuel gas
passed through teh engine.

#   I am not at all talking about "free energy." What I am talking about is,
as stated above, the potential for maximizing energy content of output gas
from a given energy content of biomass feed. More specifically, if there is
more water in the feedstock, its endothermic heat burden on the reaction is
increased, but if there is "waste heat" available, such as hot engine
exhaust, it may be able to recover this waste thermal heat, and feed it into
the reaction, to end up with a greater energy content in the output gas than
is presently attainable. There is no "Something for Nothing" scam here... it
is a question being able to recover waste exhaust heat as chemical  energy
in the output gas.

Even tars require energy for "cracking" (that's why catalysts are
important). Look at the Gibbs Free Energy of the fuel infeed and you can
compute the theoretical, 100% efficient (read:impossible!) output. 

# Using catalysts to crack tars for gasification is totally unnecessary.
Simply set fire to them.

One may wish to alter the composition of the output gas, but it ain't free,
baby! 

# I would strongly disagree with you. If the excess waste energy in the hot
engine exhaust can be used to counteract the endothermic heat load of extra
water in wet fuel, then the extra recovered energy is indeed free, from a
cost standpoint, but in no way does it violate the First Law.

Otherwise I would be filling the petrol tank on my double-engined Hummer
with quadruple A/C with my garden hose!

# No comment.

Best wishes,

Kevin

Yah!

Mark

From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Kevin
Sent: Sunday, October 17, 2010 10:43 PM
To: Discussion of biomass pyrolysis and gasification;
gasification at bioenergylists.org
Subject: Re: [Gasification] the most important thing (quite possibly)
i'velearned to date

Dear Jim

Interesting thoughts!

What are your thoughts on the optimum moisture content of biomass feed to a
gasifier? On the one hand, with low fuel moisture content, there is a low
endothermic load on teh reaction. On the other hand, a high moisture content
could yield greater hydrogen content in the output gas.

To take things to the limit, what are your thoughts on feeding a gasifier
with torrified wood?

Thanks!

Kevin 

----- Original Message ----- 

From: jim mason <mailto:jim at allpowerlabs.org>  

To: gasification at bioenergylists.org 

Sent: Monday, October 18, 2010 2:08 AM

Subject: [Gasification] the most important thing (quite possibly)
i'velearned to date

there are many variables to move around in a gasifier, and all of them are
important. but once the basics are in order, i'm coming to the conclusion
that
the most impactful thing one can do/add/fix to the basic imbert design is to
use 
the ic engine exhaust to heat the incoming fuel.

no, i don't have any numbers on this yet (we hope to get these soon), but
the
anecdotal experiences keep piling up. the biggest flexibility gains i'm
finding
both in poor fuel shape/size and moisture tolerance, as well as gas turndown
ratio, 
are from the ic exhaust heat exchanger. on our rig, this is called the
pyrocoil. other
rigs call this something else.

this is not terribly surprising. the ic exhaust is the biggest waste heat
source we have around a gasifier. in principle, the ic exhaust has about
about
3x or 4x the heat available as the outgoing syngas. the incoming fuel
similarly
has much more heating capacity than the incoming air (the multiple i forget
at
the moment, but i do know the incoming air can only take up about 1/2 of the
heat available in the outgoing syngas).

also, the ic exhaust is much hotter than the outgoing syngas after
preheating
the incoming air. thus you can use the ic exhaust to do much more than dry
the
fuel. you can it to drive the fuel through pyrolysis, and really, get it up
to
about 4-500c before it falls into the hearth proper. this is a big
difference
from the typical situation of still moist fuel falling into the hearth.

not only can you use the ic exhaust to add a very significant amount of heat
to
the system, you can also use it to change the character of pyrolysis in the
reactor. a typical downdraft has very high temp short residence time
pyrolysis
right on top of the nozzles. this high temp pyrolysis optimizes the creation
of
teritary tars, or refractory tars, which are difficult to crack again (given
lots of double carbon bonds). if you externally drive pyrolysis at lower
temp
over longer time, you get more primary and secondary tars, which are easier
to
crack downstream (fewer double carbon bonds). this seems to allow hearth
conditions to be less perfect and still get good gas out.

using ic exhaust to heat incoming fuel is not a complete get out of jail
free
card. but to me it seems the most impactful new thing one can do on these
rigs.
it seems to have more of an impact than any other single thing we've done to
date on the gek.

yes, all of it is important, and all of it should be tended to, but the
above is
my current vote for the biggest bang for the effort. hopefully we can get
some
proper numbers on this soon (and prove or disprove the above conjecture).

jim

----------------------------------------------------------------------------
--
Jim Mason
Website: http://www.whatiamupto.com
Current Projects: 
   - Gasifier Experimenters Kit (the GEK): http://www.gekgasifier.com
   - Escape from Berkeley alt fuels vehicle race: www.escapefromberkeley.com
   - ALL Power Labs on Twitter: http://twitter.com/allpowerlabs
   - Shipyard Announce list:
http://lists.spaceship.com/listinfo.cgi/icp-spaceship.com

  _____  

_______________________________________________
Gasification mailing list

to Send a Message to the list, use the email address
Gasification at bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenerg
ylists.org

for more Gasifiers,  News and Information see our web site:
http://gasifiers.bioenergylists.org/

  _____  

No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1136 / Virus Database: 422/3202 - Release Date: 10/17/10

  _____  

_______________________________________________
Gasification mailing list

to Send a Message to the list, use the email address
Gasification at bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenerg
ylists.org

for more Gasifiers,  News and Information see our web site:
http://gasifiers.bioenergylists.org/

  _____  

No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1136 / Virus Database: 422/3202 - Release Date: 10/17/10

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/gasification_lists.bioenergylists.org/attachments/20101019/fef7d89c/attachment.html>