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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks for the comments.<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'>Everything counts because outside of India there are probably only a few hundred gasifiers generating power. How many of those work 4000-6000 hours per year? Very few I would think. <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'>The context is Subsaharan Africa (SSA) where charcoal is the primary cooking fuel, and Southern Africa where abundant biomass exists that is underutilized. One project in The DRC promotes fuel wood plantations for charcoal. The villages where charcoal is produced are not electrified ad will not likely be electrified in the future. Where there is off-grid power from gensets it is expensive. So the challenge is how to recover power from waste charcoal kiln gases. <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'>In most charcoal production the kilns are vented as they go through drying, torrefaction, pyrolysis and cooling. During drying and torrefaction the offgas is mostly CO2 with some CO. The calorific value of the gas is quite low (<5 MJ/m3) for the first thirty to forty hours until kiln temperatures reach about 280 C. Combustible gases do evolve which should be incinerated in an afterburner. From 35-80 hours, a period of about 45 hours, gases evolve with a calorific value of about 16 MJ/m3, depending on the peak temperature (at 325-380C, 19 MJ/m3 at 500C). During that time the chemical energy in the gas is considered to be recoverable. The gas of course contains tars and acids. The challenge is how to recover this energy for heat or local power generation. <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'>In the US charcoal kilns are required to use afterburners to burn out the gas and pollutants. Solid fuel (e.g. sawdust) afterburners have been largely unsuccessful. Most kilns use propane piloted burners that consist of an eductor which draws the gases from several (usually four) kilns. The standing propane flame ignites the mixture to insure combustion at 1600F as required by the EPA. (The most recent batch kiln was installed with a catalytic afterburner followed by a lime scrubber and a baghouse.) In Brazil, where some large charcoal producers are supplied entirely by plantations, companies have studied the evolution of gases and the potential for energy recovery. They have tested arrangements of six or more kilns to obtain a steady gas flow in overlapping kiln cycles. Some kilns have afterburners or combustors. As yet there are no commercial systems recovering heat and power from kilns. <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 am inspired by a local biochar producer who uses a downdraft wood fired gasifier to heat his batch pyrolyzer. He starts the heating process with wood gas. Once combustible gas appears from pyrolysis he valves it into the combustor where the evolving gas combines with the flame from the producer gas to heat the carbonizer. The wood gasifier provides a stable source of heat and ignition. The combustor is the afterburner for the kiln gas. He uses a chipper to prepare the wood for the gasifier and pyrolyzer. Chips, nuts and shells make great fuels for downdraft gasifiers. If you don’t have a chipper (making gasifier fuel by hand is tedious) but you do make charcoal, why not use charcoal as the pilot fuel? <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'>So my thought is to use charcoal from the kiln production to run a small gasifier. No need to chip the wood. The gas could be used two ways: A) the gas could be used as a pilot for an afterburner which could provide heat to dry the fuel to be charred; and B) cold clean gas could be used to power a genset in dual fuel or 100% producer gas mode. A charcoal gasifier requires steam which could be supplied from the kiln gas during the early cycle. Introduce the kiln gas with the air to the charcoal gasifier. Thus the kiln gas could fuel the charcoal gasifier reducing the fuel required to fired the engine-genset. You could generate 50 kWe from about six small (12 m3) kilns.<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'>While a downdraft gasifier might work, an updraft or crossdraft gasifier might be more appropriate to this application because of the amount of fines generated in the kiln. A Missouri kiln makes about 23 tons of charcoal and 7 tons of fines from 100 tons of wood. In Brazil the fines are spread on the plantations (what else in the land of terra preta)? They could also be used to fuel an updraft gasifier if fired together with coarser charcoal. <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'>Putting a gasifier(s) together with a charcoal kiln might be a useful “marriage of convenience.”<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'>Tom <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'> <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 style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> gasification-bounces@lists.bioenergylists.org [mailto:gasification-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Robert Kana<br><b>Sent:</b> Sunday, May 08, 2011 10:08 AM<br><b>To:</b> gasification@lists.bioenergylists.org<br><b>Subject:</b> Re: [Gasification] Charcoal Gasifiers<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Dear Tom,<br>We have tried using charcoal for engine quality gas in 2 types of gasifiers. One was our own design, downdraft with tuyers and throat, the other design was also downdraft grateless design. At first we had some clingers problems, later fixed with adjusting air volume. Gas comes out pretty clean. We washed for cooling gas, in a venturi type washer, used wood chips/sawdust/charcoal for filter medium. Charcoal used was kemiri (some type of nuts grow in Indonesia) shells, coconut shells, regular wooden charcoal pieces and briquette charcoal pieces. <br>The result was OK. Because charcoal cost here is more, we stopped with the charcoal gasification, now concentrating on rice husk and wood chips.<br>Any other details you need to know, we will try to answer. <br>Actually I have almost 30 tons of charcoal pieces in stock, we were originally thinking to built gasifier for use in our own generator. But the charcoal pieces we can sell for $ 300.00 for ton. Rice husk here cost $ 39.00 a ton and we get almost as clean gas from rice husk as charcoal.<br>Robert<o:p></o:p></p></div></body></html>