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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 Kirk<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><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>I don't quite understand Crispins flame tube. <span style='color:#1F497D'><o:p></o:p></span></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Unfortunately it is a very difficult thing to photograph. It works in the same way as a concentrating cone (which I prefer for radiant reasons) or a ring – to bring the gases and air and flames into a small space to ensure burnout of the PM. The CO burn is a byproduct. It is primarily intended to burn the smoke. CO is not a major issue. The rules were not to increase the CO level, i.e. ‘do no harm’ as the ADB put it. But CO was never a problem. The target was PM2.5 (coal stoves don’t make PM10 unless they have a fan).<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>The stove appears to be loaded with charcoal, so there should not be any smoke. <span style='color:#1F497D'><o:p></o:p></span></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>There can be plenty of smoke from charcoal. It depends a great deal on how it is ignited. The fuel is in fact ‘wet’ lignite from Nalaikh which is a small town perhaps 25 km from Ulaanbaatar. There is a huge coal mine there that was closed about 1992. It has been worked informally since then by the people who lost their jobs. They pull out about 1.2m tons a year from it. By hand mostly.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>If the clay is insulating clay than the tube would provide a hot environment for the CO to burn, if there is a source of secondary air. <span style='color:#1F497D'><o:p></o:p></span></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>There is nothing ‘insulating’ about the clay. It is just clay from the river. I don’t think there is clay that is insulating. Clay is a poor conductor of heat, however, if that helps. The benefits of making a clay ‘insulative’ component are temporary and affect the short term performance, providing nearly nothing in the long run. For a space heating stove it provides the slightest flame temperature benefit under constant conditions. You can calculate it or measure it. It doesn’t take much thickness to ensure a high combustion temperature – maybe 15mm. A guide is provided by the work in South Africa on charcoal gasifiers which run at really high temperatures. Fired clay is almost always a poor conductor of heat. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>There is no provision of secondary air because there is sufficient air in the combustion chamber. The battle with these stoves is to seal them. They usually have far too much air at all times everywhere. The total air supply hole needed by a 10 kW fire is perhaps 30 x 80mm if the chimney is about 10 feet tall. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>If the stove burns wood, by what principles does the tube work? Is air injected inside the tube? <span style='color:#1F497D'><o:p></o:p></span></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>The fuel is irrelevant – this is a design principle: burning poorly in a chamber (not that I advocate it) produces PIC and CO which can most easily be burned by funneling all of it together in a small space. The tube is about 12” long. For the BLDD6 downdraft coal stove (Univ of JHB) the tube is significantly longer and has a strong induced vortex which turns the outer region into an insulator and the inner region into a very strongly mixed, turbulent flame.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>This would make use of the Venturi effect like Roberto's stove. <span style='color:#1F497D'><o:p></o:p></span></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>It doesn’t do that. It is a straight tube. Flames some out the far end. The heat exchanger is too small but this was designed as a retro-fit that could reduce emissions 80%, not a <i>de novo</i> design. There is a pair of stoves at the SEET lab in storage that were created specifically to balance the heat exchanger size with the flame tube – in that case 65mm ID. They look like traditional stoves but longer.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>The flame gasses accellerating into the tube would drop in pressure and the pressure difference would help the atmosphere push secondary air into the flame to equalize the pressure, providing good mixing. <span style='color:#1F497D'><o:p></o:p></span></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>This is not needed as the air-fuel ratio is already good. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>This seems to me like it might work well if that is how it works. Is there something else that I don't see?</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Well, it works very well, but not that way. I suppose you could call what you describe is staged mixing. This has staged combustion and pre-mixing. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>The thing that is hard to see is the way a crossdraft fire burns in a channel like that. With the lid on (or a pot) the fire works its way to towards the source of air which is on the other end from the tub. All smoke and gases generated by the pyrolysing coal have to pass over the very hot coke burning region just before the whole lot goes into the tube. This simple change from bottom lighting to ‘end lighting’ is the major source of fuel saving, and the tube is the major source of the PM reduction.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>I can try to explain using this photo:<o:p></o:p></span></p><p class=MsoNormal><img width=227 height=259 id="Picture_x0020_2" src="cid:image002.jpg@01D0F3B3.699F2F80"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>This is immediately after TLUD ignition of the kindling. So imagine that continuing throughout the burn. The emissions and burn rate profile are completely different from the standard urban users’. I was told in January the ignition method is spreading in the country without anyone pushing it so it must have obvious benefits.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>You might be surprised to know that this invention was strongly criticised by one of the major stove program managers because, he said, “You cannot solve this problem for $1.”<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Here is another $1 solution.<o:p></o:p></span></p><p class=MsoNormal><img width=378 height=410 id="Picture_x0020_1" src="cid:image006.jpg@01D0F3B3.699F2F80"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Standard $20 Mongolian traditional ger stove with an added flame tube that exits inside the heat exchanger.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Refuelling is accomplished by [pushing the burning coke to the back (through the door in the foreground) and pushing fresh coal towards it until they overlap. The fire will then burn slowly through the coal towards the door (because that is where the air comes from).<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><img width=378 height=124 id="Picture_x0020_3" src="cid:image007.jpg@01D0F3B3.699F2F80"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>ELCD burn without refuelling.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p></div></div></body></html>