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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:EN-US'>Dear Frank<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>>>…</span><span lang=EN-US style='color:#1F497D'>Generally speaking all stoves have chimneys that are too large in diameter. That is interesting.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#7030A0'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>></span><span lang=EN-US style='font-size:14.0pt;color:#7030A0'>You say to large in diameter. Based on the need for faster gas flow?<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:EN-US'>For any given quantum of heat you get more draft if the chimney has a smaller total volume. Because of rapid cooling in the chimney (being thin metal with a high emissivity) the draft is not as controllable if it is a slow moving stream. Variations in the stove power make a large difference in draft if the chimney is a major heat radiator (gives uneven performance).<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>>></span><span lang=EN-US style='color:#1F497D'>The compressor compresses air. It is filtered to 0.01 µm and put through a CO2 and water vapour adsorber, filtered again and then sued in the diluter. It is very simple and effective. The dew point is -100 F. The CO2 is <1 ppm. The O2 is much higher, about 33% which was interesting to see.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#7030A0'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>></span><span lang=EN-US style='font-size:14.0pt;color:#7030A0'>All this seems unnecessary to me. The amount of CO2 in the room air must be insignificant to what is going up the stack. Same as to moisture. Perhaps particles are a problem so in-air should be filtered. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The CO2-free air is used to calibrate the equipment (a zero-CO2 calibration) without using any reference gas. A bottle of mixed gases from Japan (5 kg) costs $19,000 delivered to Ulaanbaatar. The entire adsorber system cost less than $2000.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The dilution in the diluter can be quite high and the difference between the CO2 measured and the background signal can be small. When zero-CO2 air is used, the measurement is more precise. Moisture in the stack (and there is <i>plenty</i>) can condense in the dilution tunnel (very easily) and is measured by the particle counter as ‘particles’ but it is actually fog. This can give the appearance of a stove being ‘dirty’ when it is not. Fog condensation is a big problem in humid climates and where the fuel has a high moisture content. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>I think it is a metal matrix of some kind. It does not get used up. There are two units and they are cycled. One breathes with ‘wash air’ or ‘sweep gas’ as it is termed. The other is under pressure for 30 seconds.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>></span><span lang=EN-US style='font-size:14.0pt;color:#7030A0'>Very interesting. I am thinking it may be a Teflon membrane where when the gas is pressurized the CO2 goes through the membrane more than the O2 or N2(?) and swept away on the other side. It would be interesting to know how this works.</span><span lang=EN-US style='color:#7030A0'> <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>It is an adsorber, rather than an absorber so it is easily flushed away when not under pressure, using ordinary air.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>>…</span><span lang=EN-US style='font-size:14.0pt;color:#7030A0'>Measure the CO2 before diluter in the stack and after the diluter in the stack and you can get the dilution (mixing required I would think). </span><span lang=EN-US style='font-size:14.0pt;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>It is not measured after the diluter ‘in the stack’, it is measured in the stack and in the diluter. The ratio is the dilution factor, remembering there is a small mathematical correction involve re ambient CO2.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:14.0pt;color:#1F497D'>></span><span lang=EN-US style='font-size:14.0pt;color:#7030A0'>The CO2 concentration from combustion goes up and down a lot so the two measurements before and after must be synchronized perfectly to determine the dilution rate. </span><span lang=EN-US style='font-size:14.0pt;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Correct. In practice it changes very slowly. But change it we can, and do.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt;color:#1F497D'>></span><span style='font-size:14.0pt;color:#7030A0'>It would seem that there is enough moisture in the outside air and the combustion gas to create the fog. </span><span style='font-size:14.0pt;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Yeas and it is a big problem for wet fuels. Lignite can have 33% moisture. Imagine how much fog that creates if you collect it in a hood and cool it. I don’t want to measure fog. It has to be sampled using dry air dilution to keep the dew point below the ambient temperature. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt;color:#1F497D'>></span><span style='font-size:14.0pt;color:#7030A0'>That it is more the change in temperature (lowering) that creates the fog than the moisture in the gas. Pre-heating the dilution air is the answer to preventing fog and not dry air. </span><span style='font-size:14.0pt;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>That would create an additional problem which is that fires produce a lot of condensable volatiles. If you do not cool the gases, they do not condense and you get a dry dust measurement. This is very ‘EPA’. But it is the condensable particles that are so harmful to health. If we do not condense what we can of them, we will not know they are there. A dry dust measurement of a stove is not very useful actually. It is quite common to have the PM be 50% condensable volatiles (tars and nasty liquids) so we do the best we can to condense things without getting water vapour involved.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p></div></body></html>