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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;mso-fareast-language:EN-US'>Dear Ron<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'>Here is a global reaction – some of the chemistry that is active in biomass burning:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><img width=473 height=133 id="Picture_x0020_1" src="cid:image003.jpg@01CE9F4E.B40BC9E0"></span><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'>That is taken from a paper by Authors+Tom Miles “Fuel properties of biomass” 1998.<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'>It is really complicated. We do not need to go into all of it, but we should remember that our simplifications hide information.<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><div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal><u><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> O2-(CO/2) <span class=apple-converted-space> </span></span></u><u><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:white'>.</span></u><o:p></o:p></p></div></div></blockquote><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>21- [O2-(CO/2)]</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p></div></div></blockquote><div><p class=MsoNormal> <b>[RWL: I have found this formula nowhere. Cite? <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It is the standard way to calculate EA.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b>What i have found is that EA can be found from either measuring O2 or CO2, no need for bringing CO into this one formula. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>There is a different formula for the calculation of EA based on CO2 instead of CO. In both cases one is used to estimate the other. When both are measured, the formula can be edited to be more accurate.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b>I recognize that CO is important, but for a useful stove (not a charcoal using stove), this has to be a very small modifier on a term that we aren't even reporting in the tests (but I would like to know). Giving just O2 levels in the exhaust stream would be very illuminating.</b><o:p></o:p></p></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'>The O2 level does not tell you how much extra air was put into the fire, it only tells you what came out. What came out is important, but knowing if the correct amount is being put in is important. Important relationships between EA and CO(EF) are revealed by plotting them in real time. Tuning a stove to a fuel is done this way.<o:p></o:p></span></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal><br><span style='color:#1F497D'>>></span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It gives the wrong answer for real fire burning any fuel that contains O2, like wood or coal but gives a pretty good answer for fuels like kerosene or pure charcoal.</span><o:p></o:p></p></div></div></blockquote><p class=MsoNormal> <b>[RWL A cite for this "wrong" statement? <span style='color:#1F497D'><o:p></o:p></span></b></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'>If the O2 supplied to a fire is 100% above that which is required to burn the gases present at the time, and the formula reports that it is zero, or 300%, that is a wrong answer. The standard formula is a simplification of the actual answer. For some conditions it is ‘good enough’. Others, not.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p></div><div><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b> We should be talking separately about "flaming pyrolysis" in TLUDs (or maybe some gasification approaches) and retorts With the latter, no O2 is added. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>There is already O2 in the fuel if it is biomass.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b>The available O2 is no doubt important in a retort operation, but since we can't control it, I see little reason to quantify it, except in very general terms Retorts are not very attractive in stove designs because they are not controllable. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The World Stove is a self-heating retort. It is controllable.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b>I can't see any value in the term EA (or AER) with operation of a retort (and some aspects of a retort are probably occurring in TLUDs).</b><br><br><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'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Fortunately designers see the matter differently.</span><span style='color:#1F497D'><o:p></o:p></span></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p></div></div></blockquote><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>></span><b>It looks to me like simplification is badly needed. Doing zero computation looks OK to me</b><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'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>You can directly measure mass and time and temperature and gas concentrations but not much is learned from them directly. Metrics are mostly products and ratios.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><span style='color:#1F497D'><o:p></o:p></span></p></div><div><p class=MsoNormal><b>[RWL: I guess we have a few promoting gasifier stoves, but why not simply combust (as in a rocket) if you don't care about char. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Because a Rocket stove is not all that successful a design and has limitations inherent in its design rules. It is, for example, hard to burn pellets in a Rocket stove. It also produces a relatively large amount of char which is wasted (compared with other combustors). The system efficiency is not as high as other inherently different designs. A lot of these limitations are overcome with the institutional stove sizes. Other are not. One size does not fit all nor should it. Not a problem.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b>The TLUDs are being promoted largely because they are not gasifiers - they are pyrolyzers with an intent to produce char (the definition of pyrolysis). <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>They being so promoted by some, other are promoting them because they burn with low PM, not because they make char. Some TLUD’s make a lot of PM so the ‘layout’ is not universally successful. <o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>>…</span></b><b>I don't see any difficulty in comparing stoves that operate on a total combustion philosophy or a gasification (minimum char) philosophy. One operates on a parallel process philosophy and the other on series. The final results as a stove could differ a lot on pollutants, but the testing should go similarly. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Actually it is quite hard to write a protocol that is fair to both stoves if the entire burn is not treated as a single event. The reason is that a stick-burned pretty much burns whole fuel progressively, while a batch loaded stove often has a different fuel composition as time passes. Thus anything that is assessed over say, ½ the burn time can give very misleading results for a metrics like CO per MJ because the number of MJ is difficult to know without a real time method of analysis.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='color:#1F497D'>></span></b><b>Not so for pyrolyzers. Something theoretical on the production of particulates and CO (and PAHs) could be very helpful for stove designers.<span style='color:#1F497D'><o:p></o:p></span></b></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'>Pyrolyzers face the same issue – what is burning and when? At the end of the burn, for the last few minutes, the fuel composition changes quite a bit and this is very easy to see on the real time gas charts and the kW plot. The power level rises just at the end as the bottom char burns to CO2. In the beginning I have seen very large amounts of fuel moisture coming out, meaning the heat is being absorbed drying fuel, not heating the pot. Pellet stoves are pretty consistent after ignition.<o:p></o:p></span></p><p class=MsoNormal><br><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>>…</span><b>We are getting close to a metric that will describe TDR = turn down ratio. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The WBT turn down ratio is not appropriate, as it is merely the ratio of the simmering to boiling power. Any gas of electric stove has an easily defined TDR – move the lever. For manually adjusted fires it is difficult to say exactly.<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>>>Because the metric is based on the elements in the fuel, it is possible it is, unlike the standard EA calculation, correct ‘chemically’. We will have to check. That is the sort of check we should be doing for all metrics before we run off to make them international standards. Obviously.</span><span style='color:#1F497D'><o:p></o:p></span></p></div></div></blockquote><p class=MsoNormal> <b>[RWL: In summary, I think you are raising issues that are hopelessly complicated for the world of stove testing and comparisons. <span style='color:#1F497D'><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Applying a different formula that gives the correct answer in as many circumstances as possible is as easy as entering the formula in a spreadsheet.<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 hope these answer will clarify the issues around the correct calculation of EA.</span><o:p></o:p></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>