[Gasification] Cellulose Gas and Biochar option

Tom Miles tmiles at trmiles.com
Sat Feb 8 14:10:52 CST 2014


Tom,

 

While it is easy to visualize the concept of lignin converting to char It
would be more correct to say that a portion of the lignin decomposes during
gasification and partial oxidation. Since lignin degrades starting at
200-300 C the gaseous and vaporous products of this degradation are surely
carried off in the gas that burns when exposed to the secondary air. You can
get less char from grasses that have a higher lignin content (22%, bagasse)
than wood (15% eucalyptus). The net char yield of charring either of these
in a TLUD can be (24%)  greater than the intrinsic lignin content. Also in a
TLUD air/gas flows are rarely uniform. Surely some of the char itself is
oxidized by the primary air, generating heat to help drive the gasification.
I suspect that while lignin may be the principal precursor of char, the char
is probably a blend of products of decomposition of lignin, hemicellulose
and cellulose. I would think that someone has done a study of the
decomposition of cellulose, hemicellulose and lignin in a TLUD. 

 

Tom Miles  

 

From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of thomas reed
Sent: Saturday, February 08, 2014 6:40 AM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] Cellulose Gas and Biochar option

 

Dear Paul and all

 

Lignin is the "starch" that makes strong, but flexible (think cotton) into
tall trees, transporting water hundreds of feet above our heads.  (But
lignin is NOT not chemically related to starch, a sugar polymer).  

 

It is a very complex, three dimensional, organic substance with the
approximate formula C10H12O3 ( but a lot of variation in different species).
There are lots of phenolic groups, probably accounting for the clean smell
of wood smoke.  

 

 FROM WIKIEDIA..

 

1.     .  

o    

o    

o    

o    

o    

o    

 
<https://www.google.com/search?q=lignin&client=safari&hl=en&tbm=isch&tbo=u&s
ource=univ&sa=X&ei=fT72UtL3A4qEyAHatIHIDA&ved=0CEYQiR4> More images

.  Lignin

.  Lignin or lignen is a complex polymer of aromatic alcohols known as
monolignols. It is most commonly derived from wood, and is an integral part
of the secondary cell walls of plants and some algae.
<http://en.wikipedia.org/wiki/Lignin> Wikipedia

.  .  Formula
<https://www.google.com/search?client=safari&hl=en&q=lignin+formula&stick=H4
sIAAAAAAAAAGOovnz8BQMDgxkHnxCnfq6-gWGSsXmWlnp2spV-ckZqbmZxSVElhJWcmBOfnJ9bkF
-al2KVll-UW5qT-ObHxlWzO7f8W38jou_si8TEDEEnNwDL1OCzUwAAAA&sa=X&ei=fT72UtL3A4q
EyAHatIHIDA&ved=0CFUQ6BMoATAK> : C9H10O2,C10H12O3,C11H14O4

 

 

 

 

 

 

 

 

 

 

 

Feedback


When you walk in the woods, you often see brown logs that fall apart if you
kick them.  The cellulose of the wood has been eaten by microorganiisms that
convert it back to sugar, but they can't eat the lignin.  

 

Termites have special microorganiisms that do digest only lignin, and
occasionally you will see white wood rot, the cellulose that the termites
can't digest.  

 

Wouldn't you think all of this would have been figured out long ago and
taught in HS chemistry classes? 

 

To each his own.  Chacun a son gout!  

 

Tom

 

 

 

 

On Friday, February 7, 2014, Paul Anderson <psanders at ilstu.edu> wrote:

Tom,

I (and many others, for sure) appreciate your explanations (below).

One question:   The lignin is present as the celluloses are changed to gas.
And the lignin BECOMES char.   Please discuss that chemistry of lignin
becoming char.   What is happening?

Comment:  Looking at the gases that are coming out of TLUDs (that is, the
gases BEFORE they get to any combustor), they appear to be (seem to be, give
the impression of, possibly are) loaded with the stuff that would clog
engines.  So I need a chemist's explanation of why those gases have
advantages over those from the Imbert, etc.

Still learning,

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 2/7/2014 4:36 PM, Tom Reed wrote:

Evan

Good question, "Why do TLUDs (Toplit updraft combustors)  exclude
hemicellulose and lignin?"  First, I think they do burn the hemicellulose
along with the cellulose.  Maybe I should have said "celluloses".  (The
hemicellulose is only a few % of wood! and is even more volatile than the
cellulose. )

You are correct.  The cellulose (and hemicellulose) become volatile at about
330C,

     C6H10O5 + 1/2 O2 ===> 6 CO + 5 H2    Delta H = (2829 - 3080) -260
ENDOTHERMICl

and generates the gas we see burning in the match (for instance).  The same
temperature converts the lignin to charcoal, and if there is a choice
between cellulose (in the next lower layer for TLUDS) and this charcoal, the
flame moves to the cellulose gas from the next layer, leaving the charcoal
behind, protected by the oxygen free gas left from cellulose combustion.

The WWII (Imbert) gasifiers injected air below the unburned wood and above
the charcoal as it formed.  This keeps the air in balance, since if too much
charcoal was momentarily produced, more wood fell in front of the air
nozzles and balance was restored.
<><><>

Today we have an alternate use for the charcoal, Biochar, to improve soil
fertility and reduce global warming, so by consuming only the celluloses, we
produce ~ 20% charcoal from our wood supply. So the TLUD gasifier is a
simple alternative to Imbert.  It also produces a gas that is easier to
clean for engine use.

It is surprising that, with all the dependence on wood burning for heat,
this wasn't discovered centuries earlier.  If you make a vertical pile of
fireplace logs and light ON TOP, they will burn down at a steady rate, the
embers of each layer lighting the next layer, no matter how high the pile.

Try it, and send comments.

Tom Reed

Dr. Thomas B Reed
280 Hardwick Rd
Barre, MA 01005
508 353 7841

On Feb 7, 2014, at 4:00 PM, Evan Marks <yarmarks at gmail.com> wrote:

A question to Tom Reed:

Just wanted to get some clarity on the statment that TLUDs only burn
cellulose. If we are contrasting for instance WWII sytems and TLUDs, and
therefore limitation to only the cellulose fraction, is the primary
difference temperature? Why do TLUDs exclude hemicellulose and lignin? Is
the cellulose fraction equivalent to the volatile fraction?

Thanks, -EM





Dear Tom Miles and all

WWII gasification converted all the fuel into a low quality (150Btu/scf) gas
that required considerable cleanup. Before use in engines.

Now that we recognize the value of biochar as

O. A soil amendment

O. Reducing global warming

a second option is more attractive.

In the TLUD stove and larger (eg 33 gal garbage can) only the cellulose
burns, giving a cleaner gas

C6H10O5 + 1/2 O2 ===>
6O +  5 H2

Plus. biochar for addition to the soil.
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Dr. Thomas B. Reed
The Biomass Energy Foundation
BEF, BEC, BER

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