Brian, What you are reading is not all that unreasonable. Combustion takes a certain distance....look at a campfire flame. The flame is giving off energy the entire distance of the flame lick so assuming the energy doesn't radiate away, it's only reasonable that the temperature is highest at the end of the flame. After that it's all down hill as reduction converts thermal enrgy to chemical energy.
Stephen -----Original Message----- From: Brian D Paasch <[email protected]> To: Discussion of biomass pyrolysis and gasification <[email protected]> Sent: Tue, Aug 10, 2010 6:19 pm Subject: Re: [Gasification] Imbert chemistry question Big thanks to all of you who offered feedback on my question! Your answers were uch more diverse than I expected. I had assumed that the matter was ONLY elated to chemistry but from the discussion that appears to be only part of the ssue. One topic did surprise me... comments were made that the combustion/oxidation one is hotter than the char/reduction zone. Apparently this newbee to the art as it backwards. I thought I'd read somewhere in my documents that the char one is hotter than the combustion zone (but as of this moment, I can't find hat alleged info). And didn't the ironsmiths of days past use charcoal as fuel or their forge since it makes for higher heat than raw wood? Furthermore, our hermocouples 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) har zone reads about 1750F (950C) when we have the best looking flare we can ake. 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 etting from those TCs either.) -brian n Aug 9, 2010, at 2:54 PM, Brian D Paasch wrote: > Hi all, Got a question about Imbert style downdrafts…. One of the obvious haracteristics of an Imbert style gasifier is the hearth restriction. The ombustion/oxidation zone is physically larger than the subsequent harcoal/reduction zone. As best I can find in the literature, the size change s worked out so that there is an approximate four-fold increase in superficial as velocity through the reduction zone versus the oxidation zone. The actual elocity increase is even higher due to the higher temp of the reduction zone ver the oxidation zone and also to an increase of total mass as the asification 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 eeded a higher gas velocity through the reduction zone versus the oxidation one? Thanks! -brian ______________________________________________ asification mailing list [email protected] ttp://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org ttp://gasifiers.bioenergylists.org ttp://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
