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:[email protected]] 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 <[email protected]> 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: [email protected] 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 <[email protected]> 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. _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] 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/ _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] 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/ _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page -- NOTE: PLEASE CHANGE MY ADDRESS TO [email protected] Dr. Thomas B. Reed The Biomass Energy Foundation BEF, BEC, BER
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