Thank You to both Darren and Kevin. Brian, I would look carefully at your configuration, AND have a raw outlet gas GCMS done, as to me, your flare gas, being clear (When burning), suggests that it is a mainly CO burn, this would indicate that the gasifier is allowing O2 down to the reduction zone, and that is why you are seeing elevated reduction temperatures.
800c in the reduction zone produces a good gas mix, with little CO2, where as 900c starts to consume the H2, IN the reduction zone, resulting in a drop-off of H2 output, and a shift to more CO2/CO and less H2/CH4. H2/CH4 being the most energetic "clean" portion of good gas making. Below 800c and tars enter the gas stream, resulting in a very angry gas, when flared. Greg Manning, Canadian Gasifier Ltd. Building Hi-Performance Gasifiers, Since 2001 Brandon, Manitoba, Canada 1 (204) 726-1851 -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Schmidt, Darren Sent: Tuesday, August 10, 2010 5:32 PM To: Discussion of biomass pyrolysis and gasification Subject: Re: [Gasification] Imbert chemistry question Temperatures were measured in Imbert gasifiers at EERC by putting a thermocouple down the nozzle (measuring a few inches from where the air meets the gas & solid feedstock) the result was normally above 1800F and the end of the stainless steel thermocouple would melt eventually > 2000F. The reduction zone (char zone) temperatures were not measured, but gas outlet temps were typically in the range of 800F - 1200F. Darren D. Schmidt, P.E., Senior Research Advisor Energy & Environmental Research Center University of North Dakota 15 North 23rd Street, Stop 9018 Grand Forks, ND 58202-9018 Phone: (701) 777-5120 Fax: (701) 777-5181 [email protected] www.undeerc.org -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Brian D Paasch Sent: Tuesday, August 10, 2010 5:20 PM To: Discussion of biomass pyrolysis and gasification Subject: Re: [Gasification] Imbert chemistry question Big thanks to all of you who offered feedback on my question! Your answers were much more diverse than I expected. I had assumed that the matter was ONLY related to chemistry but from the discussion that appears to be only part of the issue. One topic did surprise me... comments were made that the combustion/oxidation zone is hotter than the char/reduction zone. Apparently this newbee to the art has it backwards. I thought I'd read somewhere in my documents that the char zone is hotter than the combustion zone (but as of this moment, I can't find that alleged info). And didn't the ironsmiths of days past use charcoal as fuel for their forge since it makes for higher heat than raw wood? Furthermore, our thermocouples must not be properly placed in our firetube. Our TC in the (putative) combustion zone reads about 1500F (815C) and our TC in the (putative) char zone reads about 1750F (950C) when we have the best looking flare we can make. So apparently we have something amiss in our assumptions there too. (Although we have no way to validate the accuracy of the signal that we're getting from those TCs either.) -brian On Aug 9, 2010, at 2:54 PM, Brian D Paasch wrote: > Hi all, > > Got a question about Imbert style downdrafts.... One of the obvious characteristics of an Imbert style gasifier is the hearth restriction. The combustion/oxidation zone is physically larger than the subsequent charcoal/reduction zone. As best I can find in the literature, the size change is worked out so that there is an approximate four-fold increase in superficial gas velocity through the reduction zone versus the oxidation zone. The actual velocity increase is even higher due to the higher temp of the reduction zone over the oxidation zone and also to an increase of total mass as the gasification of the solid fuel adds its molecular load to the gas stream. > > So my question is, why? Why did the engineers of the Imbert decide that they needed a higher gas velocity through the reduction zone versus the oxidation zone? > > Thanks! > > -brian _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.851 / Virus Database: 271.1.1/3060 - Release Date: 08/10/10 01:35:00
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