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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'>Crispin,<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'><o:p> </o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'>Thaksf or the comments. <o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'><o:p> </o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'>In 1990 and later we designed some burners for producer gas that held the gas to</span><span lang=EN-CA> between 760C--980 C for at least ¼ second. We reduced NOX when burning high N fuels by about 40%. This was on fixed and fluidized bed gasifiers, and staged combustors, from 10 GJ/hr to 90 GJ/hr. We use partial oxidation to reach the temperature and chamber design and gas flow to get the residence time. It still didn’t meet regulatory requirements but it did reduce the amount of urea/ammonia used for deNOx in the boilers. We also piloted the use of producer gas as a “reburn” fuel in a coal boiler. Producer gas was overfired in a coal boiler to “reburn” the combustion gases and reduce NOx. We again were able to reduce NOx by about 40%. The idea was to use a gasifier to convert agricultural residues and other biomass to gas for co-firing with coal. Energy prices fell so full scale industrial cofiring was not implemented. NOx control alone didn’t justify the investment in a biomass gasifier since there are cheaper alternatives. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-CA>The challenge of using this strategy at any scale is the geometry to hold the gas at temperature in the sub-stoichiometric conditions. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-CA>I agree that you are not likely to reduce or reform CO at these temperatures. If you don’t cool producer gas quickly you can get reversion to soot which would theoretically reduce CO. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-CA>In my experience NOX generation is pretty consistent as long as you have a consistent fuel composition so it’s realistic to think about a baseline NOx range. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-CA>When they add odorants to natural gas and LPG are they making “clean fuels” dirty? : - ) <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-CA>Tom </span><span style='mso-fareast-language:ZH-CN'><o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'><o:p> </o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:ZH-CN'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='mso-fareast-language:ZH-CN'>From:</span></b><span style='mso-fareast-language:ZH-CN'> Stoves [mailto:stoves-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Crispin Pemberton-Pigott<br><b>Sent:</b> Monday, October 16, 2017 3:59 AM<br><b>To:</b> Discussion of biomass cooking stoves <stoves@lists.bioenergylists.org><br><b>Subject:</b> Re: [Stoves] benefits from reduced indoor air pollution.<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoPlainText><span lang=EN-CA>Dear Tom<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>That is a very valuable contribution at this time. I attended a short conference on Wednesday and a presentation by a Professor from the Chinese Academy of Sciences who is researching 'Decoupled combustion". He has created a stove that is all but identical to the KG4 crossdraft gasifier being made in Bishkek. Quite astonishing. After years of investigation he came to the same architecture: a hopper without air moving through it, a pyrolysis zone under it, a coke bed blocking the gases from getting to the combustion chamber, and a gas burning area above the coke. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>He said something I have never heard before which is that passing the fuel N through the semi-coking and coke burning zones reduced the NOx. He said it reduced the CO as well but I believe that less than the story about the NOx.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>As I understand what you wrote below, the NOx precursors, held in the semi-coking and coke burning zones long enough would reduce to N2O if the conditions are right. Possible? The stoves are small, so it might be difficult, but relative to many other stoves, the combusting fuel mass is relatively large and the gas velocity slow. The temperature is adequate. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>I doubt the temperature in the coke bed is high enough to split N2 but we can remain open minded on that. So is there a glimmer of truth to the idea that a horizontal coke bed could achieve a NOx reduction? That is really work checking out. Perhaps what we need is a target 'regular burn' NOx benchmark then compare that with the crossdraft gasifier burning the same fuel.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>The modeling work being done at the CAS include NOx formation so I need to following this more closely, if they got that correct, at least under certain circumstances. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Incidentally, Prof Jinghai Li, Academician and Vice-Director of the Chinese Academy of Sciences (Institute of Process Engineering), Vice-President of the China Association for Science and Technology and the Vice-President of the International Council for Science, agrees enthusiastically with the proposition that <b><i>there is no such thing as a “dirty fuel</i></b><i>”</i>. He laughed heartily at the “dirty fuel” idea. At first he said that a <i>stove</i> can be dirty, but we agreed in the end that a stove+fuel+context is what determines actual performance. On top of being sensible, he is a very nice guy.<o:p></o:p></span></p><p class=MsoPlainText><span style='mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black;mso-fareast-language:EN-CA'>Regards<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black;mso-fareast-language:EN-CA'>Crispin<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black;mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black;mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Fuel bound nitrogen is usually the cause of NOx with biomass fuelas rather than thermal NOx. Grains, manures, and biosolids can all be high NOx fuels. Grains and manures can generate abundant NOx. As others have commented it is difficult to get to high enough temperatures for thermal NOx except by burning charcoal. Pyrolysis and gasification generate NOx precursors that can be "inerted" to N2O if held long enough at high enough temperatures (760C--980 C) in the absence of air. Unfortunately this is not practical in a stove. Catalysts are typically used to reduce NOx from wood gas in engine applications. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Tom <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>-----Original Message-----<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>From: Stoves [<a href="mailto:stoves-bounces@lists.bioenergylists.org"><span style='color:windowtext;text-decoration:none'>mailto:stoves-bounces@lists.bioenergylists.org</span></a>] On Behalf Of Andrew Heggie<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Sent: Sunday, October 15, 2017 3:26 AM<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>To: Discussion of biomass cooking stoves <<a href="mailto:stoves@lists.bioenergylists.org"><span style='color:windowtext;text-decoration:none'>stoves@lists.bioenergylists.org</span></a>><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Subject: Re: [Stoves] benefits from reduced indoor air pollution.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>On 15 October 2017 at 00:43, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com"><span style='color:windowtext;text-decoration:none'>crispinpigott@outlook.com</span></a>> wrote:<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>> Prof Stuart Piketh said last night that the conversion of N2 to NOx is copious above 1850 C which is easily reached in a power station with only 5-6% excess air.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>...but wood is already partially oxidised so the adiabatic flame temperature is only around 1600C and I seldom see more than 1100C .<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>This of course is why charcoal was needed before iron could be smelted, even then it depended on the fact iron carbide formed a eutectic mixture that lowered the iron melting point.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>P<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>> The only way to get really high temperatures, which I define as melting the ash (in the absence of significant quantities of fluxes), is to blow on the fire.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Yes this is char burning<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>I<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>> There is a very practical side to this. Is it worth separately measuring NO and NO2 when testing a stove? Many emission standards mention pollutants and metrics that are copied straight from power stations where the combustion process and goals are very different.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>I wouldn't have thought so but stand to be corrected. I worked most of my adult life by the exhaust of two stroke engines and they are particularly bad for both particulates and NOx, especially when running lean which gave some extra revs. You soon notices the acridity from NO2 if working in a poorly ventilated hollow.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>> So the question is, what are the appropriate measurements to make and what should be the reporting framework?<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>That's for someone better qualified than me to answer but black sooty particulates come high on my list and then CO if unvented.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Andrew<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>_______________________________________________<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Stoves mailing list<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>to Send a Message to the list, use the email address <a href="mailto:stoves@lists.bioenergylists.org"><span style='color:windowtext;text-decoration:none'>stoves@lists.bioenergylists.org</span></a><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>to UNSUBSCRIBE or Change your List Settings use the web page <a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org"><span style='color:windowtext;text-decoration:none'>http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</span></a><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>for more Biomass Cooking Stoves, News and Information see our web site:<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><a href="http://stoves.bioenergylists.org/"><span style='color:windowtext;text-decoration:none'>http://stoves.bioenergylists.org/</span></a><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>_______________________________________________<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Stoves mailing list<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>to Send a Message to the list, use the email address <a href="mailto:stoves@lists.bioenergylists.org"><span style='color:windowtext;text-decoration:none'>stoves@lists.bioenergylists.org</span></a><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>to UNSUBSCRIBE or Change your List Settings use the web page <a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org"><span style='color:windowtext;text-decoration:none'>http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</span></a><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>for more Biomass Cooking Stoves, News and Information see our web site:<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><a href="http://stoves.bioenergylists.org/"><span style='color:windowtext;text-decoration:none'>http://stoves.bioenergylists.org/</span></a><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p></div></body></html>