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HomeMy WebLinkAboutGLYCERIN BURNING OVERVIEWOVERVIEW OF GLYCERIN BURNING Burning glycerin/glycerol is appealing to those who need to get rid of glycerin or those who need to reduce their heating fuel costs. Biodiesel producers fit into both categories. The following is a summarization of steps to be taken to successfully burn glycerin. Bypassing any of these recommended steps will likely be problematic. Because glycerin is not usually considered a fuel, all effort must be taken to keep any possible issues in check. 1.Glycerin cannot be burned successfully in all types of oil burners. AgSolutions LLC waste boiler burners are proven to burn glycerin successfully. 2.Glycerin cannot be simply poured, or sprayed, onto an open flame. The results are zero gain in heat production; you do however get rid of the glycerin. 3.Glycerin must be burned in an atomizing burner system. 4.Glycerin must be thoroughly preheated to at least 160F (83C). 5.As much methanol as possible should be left in the glycerin. If during the biodiesel production the methanol is removed from the glycerin, we recommend that it be mixed back in with the glycerin before using the glycerin as a fuel. This increases flammability. 6.The glycerin, with whatever amount of methanol, must be blended with another product before attempting to burn. That product can be biodiesel, recycled motor oil, recycled transmission/hydraulic fluid, #2 fuel oil, diesel fuel, kerosene, or vegetable oil. 7.The blend percentages can be 80% glycerin/20% blend agent to a 50% glycerin/50% blend agent depending upon the quality of the glycerin itself and the BTU value of the blend agent. With used vegetable oil as the blend agent you will likely be able to have a blend of about 50% glycerin /50% used vegetable oil. We recommend the 70/30 blend as a general rule to start with for all other blend products, with adjustments in those percentages as the user learns more about how the blend performs in their installation. 8.The glycerin/blend agent mixture MUST be kept mixed while in the final fuel tank. There is no way around this, it MUST be done. We recommend a simple pump that pulls from the bottom of the fuel tank and simply dumps back into the top of the tank. A standard centrifugal pump can be used as long as it has viton seals. Some of our customers have mechanical mixing devices keeping the fuel mixed, primarily because they already had the devices on hand. The pumping system will work well. 9.The blended fuel MUST be kept warmed to 85F-90F (30C-32C). Since heat spreads out so evenly in the blended fuel, it does not take a lot of heat to keep the fuel warm. These temperatures are critical. 10.We recommend that the fuel line from the tank, across the filter, across the pump, and all the way up to the pressure regulator on the burner be heat traced and insulated to retain the heat, which will keep the glycerin from thickening. We highly recommend the use of “self-regulating” heat tape (Chromalox and others). Grainger, and others, sell it in pre- assembled lengths at a reasonable price. 11.We have customers that do not use the filters provided with the burners. The glycerin is already filtered to below 1 micron, so unless the blend agent is not filtered to at least 100 micron, it should not produce problems. 12.The blended fuel will occasionally form a gel-like product on the filter screen and on the safety screen of the oil pump. 13.We recommend that periodically the user runs some diesel fuel or fuel oil through the fuel line to flush out any glycerin that may be remaining. 14.When the system is going to be shut down for more than 3-4 days we also recommend the flushing process. 15.The exhaust draft off the combustion system has to be correct - the glycerin blend is rather finicky about this. 16.The ash that is left inside the combustion chamber and the combustion gas passages must be removed before it becomes a problem. If left inside, not only will the heat not transfer, but the salts in the ash will form a crust that cannot be simply vacuumed away. The salts are benign (harmless). 17.The ash content of the blended fuel can be reduced by two methods. The first method is to simply allow the soaps to settle out for 3-4 weeks (titration). The second method, and the most widely used, is to adjust the ph of the glycerin to 7.5 (neutral). It does not help to reduce it further. You can use simple sulfuric acid or citric acid to adjust the ph. One of the first issues brought up in any discussion about the use of glycerin as a fuel, is the formation of acrolein. Acrolein is considered a carcinogen by the US EPA; however, the level of toxicity has not been established. Acrolein is released, at varying levels, during the combustion of most biomass products like burning leaves and cigarette smoke. It is exhausted from the tailpipes of automobiles. When the entire process that we have suggested is followed, the acrolein would be consumed because the flame temperatures produced (about 1800F or 932C) will consume the acrolein. The burners that are utilized for burning glycerin blended fuels are not typical pressure-atomizing burners. An air atomizing-type burner must be used, along with a pre-heater. Our standard burners provide both of these functions. We can also modify many larger burners to provide the same functions. In larger burners we recommend the use of a fuel gas (natural gas or propone) to initially fire the burner and to a lesser extent, operate at about 8% - 10% capacity while the glycerin blended fuel is being used. Burning glycerin as a fuel offers a means to dispose of glycerin produced in the biodiesel process as well as reduce process heating costs. AgSolutions, LLC is glad to assist you in your efforts to use glycerin as a fuel and to reduce your heating fuel costs.