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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Dear Friends<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Please consider a lesson learned long ago from Tom Reed which is that if you regulate the superficial air velocity in a stove you can burn the carbon completely, partly or not at all. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>There may be many people who wish to burn the char chips they have lying (literally) around the kitchen by placing them into the fuel in a TLUD or other burner. A TLUD stove that accepts chopped wood (pieces, not chips) can function much better with the charcoal chips dropped into the spaces between the pieces of wood. It is worth a try. We cannot rule out whole classes of combustor because of someone’s personal opinion of what other people ought to do.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Dear Paul</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Thanks very much for your detailed explanation.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Fundamentally, a "Perfect" TLUD will work perfectly if it has perfect fuel, perfect, required air volume, and perfect fan pressure (or stack vacuum) to deliver the perfect air flow.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Given that you have "off-standard" fuel, with greater average void space diameter, the pressure loss across the fuel bed will be lower. The fan or stack will thus deliver more air through the bed. Thus, you will get excess primary air flow, and if your secondary air porting was designed for a bed with a greater pressure drop, you will get less secondary air delivery; this will mess up your intended Secondary/Primary air ratio.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>You can burn virtually any fuel in a TLUd, as long as it is uniform, and the stove was designed to handle it. Change the fuel significantly, and you need to change the design, to maintain the desired SA/PA ratio. If you "change the fuel", but don't change the design, then the only way to restore the system to "good operation" is to "modify the fuel" to one having similar a pressure drop across the bed, similar to one for which the system was designed. This is what you are effectively trying to do.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Assume, for example, that you have 4" long pieces of straw as fuel. This will likely give you all the problems you note. Adding char can, in theory, help increase the bed pressure drop. However, I am guessing that it will be a real stinker to get the char particles distributed through the bed. There will likely be "too much" in one area, and "too little" in another. Channelling is thus very likely. What you will probably end up with is a fuel bed having non-uniform flow properties, because of the large differences between straw properties and char properties. Try mixing various percentages of char with the straw, in a mixing bucket, then try to take "mixed fuel" from the "mixing bucket" and place it in the stove. I am guessing that you should see the non-uniformity of the fuel bed even before you ignite it.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>My guess is that your best bet would be to chop the straw, so that it is free-flowing. This alone will make life very much easier for the operator, and will enable a greater weight of fuel to be added to the stove. Longer burn times between re-fuelling. Play with the air flow, simply by obstructing the fan intake with a piece of paper or cardboard. Then see if you can get your usual good combustion. If not, then consider re-drilling or partially plugging, the SA air holes to get back to the correct PA/SA ratio for good combustion.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Is chopping the straw (or whatever the fuel is) an option you can consider?</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Best wishes,</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Kevin</span><o:p></o:p></p></div><blockquote style='border:none;border-left:solid black 1.5pt;padding:0mm 0mm 0mm 4.0pt;margin-left:3.75pt;margin-top:5.0pt;margin-right:0mm;margin-bottom:5.0pt'><p class=MsoNormal><o:p> </o:p></p></blockquote></div></body></html>