污泥高温烟气干化及掺烧系统的热平衡分析

Heat Balance Analysis of Sewage Sludge Co-combustion System with High Temperature Flue Gas Drying

从流化床锅炉的旋风分离器出口烟道抽取高温烟气进行污泥干化,干化后的污泥与煤掺烧,是污泥处置方法之一。为掌握这种污泥干化掺烧系统的性能,通过热平衡计算分析了污泥掺烧比例和干化污泥含水率对烟气量、燃烧温度、受热面吸热量分配比例、抽取热烟比例、燃煤量的影响。结果表明:污泥掺烧会降低理论燃烧温度,增加炉内总烟气量。随着污泥干化程度和掺烧比例的升高,污泥干化所需抽热烟气的比例、炉膛和尾部烟道中受热面吸热量的比例都会增大;过大的污泥掺烧比例会导致炉膛尺寸显著大于尾部烟道,给锅炉设计带来困难。污泥干化程度和掺烧比例对节煤量的影响很小,污泥干化不能直接产生显著的节能效果;优选干化污泥含水率和掺烧比,其作用在于控制炉内烟气量和温度水平,优化焚烧炉和干化设备的配置,降低总投资成本。

Thermal balance analysis was carried out to study the performance of a novel sludge disposal system,in which high temperature flue gas was extracted from the outlet of cyclone separator in fluidized bed boiler to dry sludge,and the dried sludge is then co-combusted with coal.The influence of blending proportion and moisture content of dried sludge on flue gas volume,theoretical combustion temperature,heat distribution ratio on different heating surfaces,extraction ratio of high temperature flue gas and coal consumption were analyzed.The results show that the co-combustion of dried sludge will reduce the theoretical combustion temperature and increase the total flue gas volume in the furnace.With higher degree of sludge drying and the proportion of blended sludge,extraction ratio of high temperature flue gas for sludge drying will increase,as well as the proportion of heat absorbed by the heating surfaces laid in furnace.If the proportion of blended sludge is too high,it will cause the furnace chamber size to be significantly larger than the tail flue duct,which will bring difficulties to the boiler design.The degree of sludge drying and blending ratio have little effect on coal saving,and sludge drying cannot directly produce significant energy-saving effects.The optimization of moisture content of dried sludge and blending ratio in this system is mainly aimed to control flue gas volume and temperature in the furnace,match the size of boiler and drying equipment,and reduce the total investment cost.