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</o:shapelayout></xml><![endif]--></head><body 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'>Dear Roger<o:p></o:p></span></p><div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>></span><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Why isn't the secondary combustion process be applied in cooking? or another angle why could these appliances do both jobs?<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'>Secondary and even tertiary combustion is commonly applied in stoves. In fact even an open fire has secondary combustion of the gaseous products that evolve from the solid fuel. In some cases, the secondary air enters the combustion area together with the primary, and sometimes it is brought in via a separate channel (esp through a number of holes). On occasion the secondary air is blown in with a fan or a chimney (which is a natural draft ‘fan’ in that it provides something like forced air).<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 are combustors that provide most of the secondary air with the primary air, and add a small amount of secondary (sort of ‘supplementary’ air) above the primary combustion area. An example of this the GTZ 7 series stove (now renamed GIZ 7 because they changed the name of the organisation). It has a grate setup that allows most of the needed secondary air to pass through a thin layer of burning coke where it is preheated and partly used. There follows a small set of holes (about 8) that let in just enough secondary air to complete the burning. This has the result that the amount of air pissing into the fire is minimised, but enough. The result is a very high flame temperature.<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'>Stoves that are known for having very restricted primary and lots of secondary are the gasifiers like the CampStove from Tom Reed. His stove has a small fan and most of the air, nearly all of it, is secondary. There are natural draft gasifiers and pyrolysers (that deliberately make char) which accomplish the same thing using slightly taller stoves that basically have a short chimney section inside. <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'>They are all built to create gases then burn them at a secondary stage. The GIZ 7 stoves can arguably be analysed as having three sets of air supplied: primary air to devolatilise the coal or wood, then secondary air preheated by passing through a thin layer of nearly burned fuel, then preheated secondary air that passes through a set of holes about in the middle of the flaming area (combustion chamber). This last ‘air’ is tertiary in that it is one of three supplies, however there are only really two burning areas: the primary one and the secondary one. Not every stove fits easily into simple categorisation.<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 would be interested in hear from you what has been built. Is the primary or secondary air deliberately pre-heated before entering the fire? Do you control the amount of secondary air during the burn (for example closing it off when the fire gets low(er)?<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></div></body></html>