Hi Brian and Colleagues, Further to your August 11th posting:
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?
Charcoal for commercial steel smelting is used today in Brazil. The only thing raw wood is good for is as a combustion fuel.
Furthermore, our thermocouples must not be properly placed in our firetube.
This statement suggests that you are making a open core type gasifier with a firetube, not Imbert as the discussion has been covering.
Our TC in the (putative) combustion zone reads about 1500F (815C)
If you are following Imbert principles, oxidation zone temperatures can easily reach 12-1500C across the core, and need to carbonize the wood completely before it moves down into the oxidation zone. In these types of gasifiers as an example, we have a bed speed of 12"/min. at the char interface across and into the oxidation zone, and we see the wood turn to charcoal, beginning 5" above as dark colour, then gradually torrifying or baking, then finally to carbon. We refer to this point as the char interface. So it only takes slightly less than half a minute if the temperatures are correct, for the wood consumption from large chips to completely carbonize. The conversion speed can see the oxidation zone run out of charcoal and bridge, if the temperatures are lower than the exothermic heat demand of the gas output.
and our TC in the (putative) char zone reads about 1750F (950C) when we have the best looking flare we can make.
I have to read this to mean the reduction zone, but if the reduction starts at a restriction as in an Imbert, then you must have at least 1,000C, because reduction in these types of packed beds literally stops at 850C, or slows to a point of instability, and if still contained in the bed or exiting gas space, will revert to soot and CO2 until the gas temperature drops to below 500C.
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.)
If you are building an Imbert, you should fit the TC with just it's tip at the top of the throat, and one at the bottom of the reduction zone where the gas exits towards the gas outlet. You can then get a tail on what you are actually working with, and move on with your own yard-stick. I think you could get more help if you put up a web page of photos.
As you started off by asking about flares, and I suggested that condensate was a possible contributing factor, several members wrote to me off line wanting to know more. While I don't have any special interest in the subject, I have collected a lot of photos, and some experience of what they show in relation to how the gasification process is working. You can see this Condensate file on the Fluidyne Archive www.fluidynenz.250x.com . Remember it is only a basic field test, and you need to learn how to apply it, given the type of gasification process from which the condensate originates.
Doug Williams, Fluidyne Gasification. _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org
