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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'>Shailendra,<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 composition of bagasse varies considerable. We have gasified and burned very clean bagasse and very dirty bagasse. The larges variation comes when the cane tops and leaves, called “trash”, are included with the cane as it goes through the mill. The tops and leaves contain high concentrations of sodium, potassium, sulfur, and chlorine and low concentrations of silica, calcium, and magnesium. The balances of these minerals determine the melting temperatures of the ash mix and whether particles stick together as agglomerates or melt and fuse like glass. The plant takes up salts from alkaline soils which is not always cleaned in the sugar extraction process. This increases the concentrations of low melting compounds of chlorine (KCL, NaCl) and sulfur. Straw and other agricultural residues that contain annual growth have very high levels of potassium. The proportion of potassium to silica determines if the silica will become sticky or melt. The more potassium, the lower the melting temperature. <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'>Melting temperature measured I the lab are usually not accurate because they use methods appropriate for coal in preparing the samples to be tested, not biomass. For coal the fuel sample is ashed at 850C or 900C. That vaporizes elements that are important to melting. In Europe and North American labs the fuel sample is prepared at 550C or 600C which is below the vaporization temperatures. Then when the ash is heated it will melt at more typical temperatures. <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'>Pellets are dry so they burn at very high temperatures ( 800-1000 C). To prevent slagging you need to burn the fuel in stages. The first stage includes drying, de-volatilization,, pyrolysis (heating) and gasification (partial oxidation). You must control the air at that stage on the grate so that temperatures do not exceed 750 C. This is usually done by limiting air through the fuel pile. When the gases emerge above the fuel pile you can add air and increase the temperature, usually to 800-900C. Then you must have a mechanism for removing the dry ash. If it remains exposed to the hot flame it can stick together (sinter) or melt ()fuse) to ash. <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'>Stages combustion in a pellet burner can be a challenge. Most pellet burners are designed to burn the fuel and air mixture at the highest temperature which is usually in the range of 1000C- 1100C range which will melt most dirty fuels. <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'>Another approach is to add minerals to the fuel ,like dolomite or kaolin clays, that contain high proportions of calcium or magnesium. These minerals will raise the melting temperature of the mixture and reduce sintering or slagging. <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 Miles <o:p></o:p></span></p><p class=MsoNormal><a name="_MailEndCompose"><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></a></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"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Stoves [mailto:stoves-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Crispin Pemberton-Pigott<br><b>Sent:</b> Friday, May 16, 2014 4:36 AM<br><b>To:</b> stoves@lists.bioenergylists.org<br><b>Subject:</b> Re: [Stoves] Clinker Formation<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Dear Shailendra<o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>What you describe is what happens when there is a flux present - probably more than one. A flux reduces the melting temperature and it is not a surprise that you have a clinker problem. It may well be glass, not ash in the mineral sense but of course glass is a mineral. <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Perhaps Alex English will comment because he has made more glass accidentally than most of us put together. <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Roger Samson showed us that leaving switchgrass outside through the winter removed Cl and K by leaching. The problem went away. <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Another possibility is to change the combustion to try and prevent the temperature rising so high. That would involve cooling the char burning zone by not preheating the primary air, just as an example. <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Regards <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Crispin <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='background:white'><span style='font-family:"Calibri","sans-serif";color:#1F497D'>BBM 2B567C3<o:p></o:p></span></p></div><p class=MsoNormal><o:p></o:p></p><div><div><p class=MsoNormal>Dear All, <o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>We in India are trying to find a solution to the clinker problem in the stoves as the temperature reaches above 1000 degrees very soon in a 30KW stove for example. Now the pellets we are using are mainly bagasse based, and its ash melting point is above 1000 degrees but still it is not giving the right result. The pellets are not made of 100% bagasse and the size we are using is 8mm.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Please give your inputs/suggestions if this problem can be solved by adjusting the primary secondary air or we need to change the composition of the pellets.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Regards<o:p></o:p></p></div><div><p class=MsoNormal>Shailendra <o:p></o:p></p></div></div></div></div></body></html>