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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 Jaakko<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'>This is very reasonable. Because most people have not been measuring H2 (which requires an electrochemical cell) there is very little information on it. It just happens that the SeTAR Lab and sometimes the SEET lab in Ulaanbaatar use combustion analysers from time to time we get this 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><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>I was surprised to see two things in fires: H2S late in a fire, and H2 late in a fire. One expects that H and S are long gone from a pile of red charcoal. Not so.<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'>We often see H2(EF) in the 15,000 ppm range with a dilute measurement of about 2000 ppm. <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'>The correlation coefficient is so high that is must be as valid an indicator as CO for incomplete combustion.<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'>The only thing that might be messing this up is the possibility that it is an autocorrelation because the H2 is measured on the same cell as the CO in most machines. The CO is strongly affected by the presence of H2 and there is (is good ones) a separate detector built in that determines the H2 concentration and factors the CO value using it. This is reported in detail in the Testo 350/454 manual which has lots of useful info in it.<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'>Outside this possibility (a machine error) I think the H2 really is present and there is a lot of it. It looks like ordinary gasification. Maybe in some stoves it runs ahead of the other gases and escapes with greater relative ease. <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'>Thanks<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'>Crispin <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'><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'>Dear Crispin, Karve and all,<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 lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'>H2 can be both from combustion air and fuel as charcoal contains also some hydrogen. As discussed in the list, H2 can be formed both from gasification and from water-gas shift reaction if temperature is high enough. Temperature can rise high locally inside char bed in the location where O2 is completely consumed allowing reactions to take place there and H2 not to be burned (because oxygen has been consumed). H2 is probably not from wet charcoal, since moisture is driven out (by drying) as H2O at lower temperature, except if combustion air comes from a dyer.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'>Hydrogen is very reactive. H2 burns faster than CO (if oxygen is present). CO emissions correlate well with hydrocarbon emissions in fireplaces for heating purposes. I believe that H2 is so reactive that emissions of it are minor, if there is oxygen in the gas and temperature is high enough. Was oxygen concentration in gas zero? Both H2 and O2 could be averagely present in the gas in high temperature (and found when gas is cooled), if H2 produced is channelled somehow so that it does not mix well with O2. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'>Moisture in combustion air reduces CO emission from charcoal bed by two ways (if there is enough oxygen): <o:p></o:p></span></p><p class=MsoListParagraphCxSpFirst style='text-indent:-18.0pt;mso-list:l0 level1 lfo2'><![if !supportLists]><span lang=EN-GB style='color:#1F497D'><span style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-GB style='color:#1F497D'>The mixture of CO and H2 is ignited and burned better than just CO due to high reactivity of H2 producing heat to sustain combustion (also of CO) .<o:p></o:p></span></p><p class=MsoListParagraphCxSpLast style='text-indent:-18.0pt;mso-list:l0 level1 lfo2'><![if !supportLists]><span lang=EN-GB style='color:#1F497D'><span style='mso-list:Ignore'>2)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-GB style='color:#1F497D'>The combustion chemistry of CO involves radicals formed from H2O even the simple reaction CO+½O2=CO2 does not show it. So increase in H2O accelerates burning rate of CO. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-family:"Calibri","sans-serif";color:#1F497D'>Jaakko</span><span lang=FI><o:p></o:p></span></p></div></body></html>