Dear Andrew Um....not sure what the ambiguous part is. Looking again:
> >The problem is the same as with all the batch stoves: if it is > >refuelled in a ‘traditional’ manner, the smoke is far worse than the > >traditional stove. The normal method of refuelling a stove is to put in more coal/fuel. If someone has a GTZ 5 coal stove (attached) they light the fire at the bottom then pour coal over it. Obviously it makes a great deal of smoke. Refuelling it does the same. When someone makes a TLUD stove that looks exactly the same inside (an empty ceramic barrel) there is an expectation that people will refuel it in the same manner they usually do. It is about -34 C tonight in Ulaanbaatar. People do not want to wait for the fire to go out (which can take hours) in order to refuel and re-start it. >>That means training people not to do what comes >> naturally (let the stove die out and refuel and relight from scratch). Yeah. That is what I meant. >Most fires have poor performance at lighting and dying ember stage. The stoves we have been testing this week are not in this category and as we learn more, the expectation of very high late fire CO is waning. The CO/CO2 ratio (a measure of combustion inefficiency) rises to perhaps 16-20% then drops as the fire has only smouldering coals, to settle at about 12% with a very low burn rate. The ignition emissions have come down dramatically with better methods. Currently the record holder is the GTZ 7.5 stove which is a Crossdraft stove with a coal hopper. It is about 7 kW and has nearly no emissions of PM or CO. Amazing as that seems, it was repeated in a demonstration of the lighting technique today. For much of the time the PM emissions are negative, that is to say the air has more particles going into the stove than the gases do coming out of the chimney. The ignition sequence is definitely TLUD and does not involve snuffing char at the end. It can also be refuelled with no detectable increase in emissions. I have done this several times during tests. Shaking the grate creates measurable particles - sometimes lots (I once briefly saw 450 mg/m3 just from grate shaking), but it settles down soon afterwards to the <100 microgram level (after factoring for dilution, obviously). We seem to be entering a new era of low emissions. The GTZ 7.5 achieved a burn (90% of fuel burned) of PM2.5 emissions of less than 0.4 mg/MJ and less than 0.4 g CO/MJ over a period of about 5 hours. Maybe it was 6. That includes the ignition and one refuelling episode. After the coal is coked there are nearly no particles at all - well below the ambient level, meaning the stove is cleaning the air. We laugh about it a lot! We are looking for the PM net negative stove. We have tested three stoves in the past week that achieved a CO/CO2 ratio of less than 0.01% for extended periods. Many assumptions are evaporating. >Tlud gets around this at the beginning by having dry fuel and a good flame to >burn offgas in and at >the end by snuffing the char so that it doesn't burn. We are now using TLUD lighting and getting a good flame and gassing using fuel with 26% moisture that makes zero char and has no big end-of-fire smoke (which would be read as PM2.5). Test results are available to the interested. Regards Crispin
<<attachment: GTZ 5.0 spotted in the wild, Mongolia Energy Show Dec 2010.JPG>>
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