Energy recovery from wastes : experience with solid alternative fuels combustion in a precalciner cement kiln
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Original versionConference object. 3rd International symposium on Incineration and fuel gas treatment technologies. Brussels, July 2-4, 2001.
Today virtually all cement clinker burning processes take place in rotary kilns. A mixture of calcareous and argilaceous materials is heated to a temperature of about 1450 °C. In this process decarbonation followed by partial fusion occurs, and nodules of so-called clinker are formed. The cooled clinker is mixed with a few percent of gypsum, and ground into a fine meal - cement. The most modern cement kilns are equipped with a precalciner, in which most of the calcium carbonate decomposes into calcium oxide and carbon dioxide, before the precalcined meal enters the rotary kiln, where the rest of the burning takes place. The endothermic cement burning process requires large amounts of thermal energy, which is supplied by fuel combustion in the rotary kiln and in the precalciner. Coal and petcoke are most frequently used, but oil and natural gas, are also burnt in some plants. However, due the negative impact of the fossil fuels on the environment, alternative fuels are utilized to an ever increasing extent. Norcem, Norway's sole cement manufacturer, has experience with alternative fuel combustion since 1987, when combustion of liquid hazardous waste (LHW) was started. Since then, different types of solid alternative fuels, such as solid hazardous waste (SHW) and refuse derived fuel (RDF), has come into regular use. This paper presents Norcem's experience with combustion of solid alternative fuels in Kiln #6 at the Dalen cement plant in Brevik, Norway.