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
