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On Feb 2, 2011, at 11:17 AM, "Crispin Pemberton-Pigott" <[email protected]> wrote: > Dear Paul'n'All > > Sorry not to be able to get to ETHOS - it was my intention to get here this > year but things in Ulaanbaatar are moving fast than expected and several > major advances in products, understanding and financing have popped. That's > life, at least some of the time. What this space because it is going to have > effects beyond UB. > >> 2. To the best of my knowledge, neither Aprovecho nor any >> installation of the PEMS equipment does not have TSI or Testo testing >> equipment, so no correlations have been made between the results of >> these different types of equipment. > > There are two approaches used to defining combustion efficiency: the > CO/Total Carbon method and the CO/CO2 method. Both use only a portion of > actual combustion efficiency and this is done because they are easy to > measure and/or calculate. > > CO/CO2 is a measure of combustion IN-efficiency. > > Measures of combustion inefficiencies include: > CO/Carbon and CO/CO2 > H2/H2O > H2S/S and H2S/SO2 > > I am hoping that Steve Garrett will come up with a way of measuring H2O at > high temperatures (700) using an inexpensive thermoacoustice device. He is > optimistic. > > The direct measure of combustion efficiency is often written as: > > CO2/(CO2+CO) > > That is the ratio of CO2 (proper combustion) to the sum of CO and CO2 (total > carbon-containing gases measured). The higher the number, the more complete > the burn. > > Examples are: smouldering dung in an Indian open fire might be 85% (reported > by K Smith), and burning lignite in a Mongolian GTZ 7.5 stove averages > 99.44% (reported by SEET Lab). > > Legislation is rarely written this way. It is not written with a high > combustion efficiency in mind, it is written with a permitted 'inefficiency' > in mind, meaning emissions of something we don't want. > > So the most commonly used measure of combustion is CO/CO2. It is also common > to have 2% as the target value for combustion because it has been shown that > in a normally ventilated house, the CO level does not build up to dangerous > levels if the burner is working well enough to keep the CO below that level. > > 98% combustion efficiency is NOT the same as CO/CO2=2%. The latter means 1 > molecule of CO per 50 molecules of CO2. 98% means a ratio of 1/48. Thus it > is technically to refer to the CO2/(CO2+CO) as an efficiency, and CO/CO2 as > a ratio. It is often referred to as COr (the CO ratio) because it is easier > to say. We ask, 'What is the combustion efficiency?' and get the answer, > 'The COr is 3.51%.' > > Combustion analysers often give the COr as a % or as a fraction. My TSI > reports the fraction in decimal form: 0.0200 is 2%. Testo reports 2% on the > screen. > > The reason they do not report the combustion efficiency is the technician is > testing a burner like an apartment building furnace and has been told to > tune the air supply until the number is 'below xx%' so that it is operating > within the manufacturer's stated range. > > Lab results sometimes report the CO2/Total Carbon = CO2/(CO2+CO) = > combustion efficiency. > > Russian republics (incl former USSR) normally have different COr values > permitted for different fuels. Examples are: > Wood 4% > Coal 2% > Anthracite 0.5% > > There is an article on the use of a combustion analyser to test and develop > stoves here: > > http://www.hedon.info/docs/BP55-PembertonPigott.pdf > > The upcoming Domestic Use of Energy (DUE) Conference in Cape Town in April > will have three papers on the test lab use of combustion analysis to develop > stoves in Ulaanbaatar. One is on the problem analysis (air quality and > particle analysis to attribute the problem to domestic coal combustion). > Another is on the test protocol used to make measurements and process them. > The third is on the use of the measurements to adapt the product to minimise > the PM produced. Over a period of 6 months, these methods were applied to > reduce emissions by a factor of 1000 (99.9%). The baseline and improved > stove PM measurements are attached. The black lines are real time emissions > of PM2.5. > > Key to this result was the use of real time calculations to discover when > things were working well and expand that zone of perfection until it covered > nearly the entire burn period. > > The stove development was not actually guided by the PM numbers, but by the > CO/CO2 ratio. As the ratio goes very low when there are still volatiles > present in the fuel, the PM disappears as a matter of course. You don't have > a CO/CO2 ratio of 0.02% (1/100th of the permitted ratio) and still have lots > of PM. The reverse is not true. If the PM is absent, it doesn't mean the CO > is gone. A coke fire can produce no PM and vast quantities of CO. > > PM emissions are often expressed in g/kg of fuel burned which can be very > inconvenient when making comparisons between stoves and fuels. > Labs/engineering facilities usually express it in g or mg per MJ or per > useful MJ (MJ absorbed, work done, used etc). > > Stove rating involves testing the whole system, as used, so it should be > mg/MJ absorbed (in the pot, if it is a cooking test). A stove with worse > combustion but better heat transfer will rate better in terms of emissions > per task accomplished. > > Regards > Crispin > > <081.10.4.1 PM 2.5+Mass Burned Traditional Baseline 2010-08-22 v2.58.JPG> > <117.10.4 PARTICLES GTZ 7.5 2010-12-18.JPG> > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > Stoves mailing list > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://www.bioenergylists.org/ > [email protected] > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address Stoves mailing list to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/ [email protected] http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
