Study On The Combustion Characteristics Of Coal Washing Sludge During Fluidized Bed Combustion

Coal washing sludge is a kind of industrial solid wastes produced by coal washery.In the background of ever-graving environmental problems in China,more and more raw coal is selected by washing,at the same time,there is much more coal washing sludge by-product.It has been a challenging and meaningful task that how to deal with coal washing sludge efficiently and economically.Fluidized bed combustion technology has the advantages of minimization,resource recovery and large capacity,the coal washing sludge ash can also be further utilized comprehensively.But coal washing slurry has some characteristics,high moisture and ash content,low calorific value,which make the combustion performance poor.In addition,China has implement the new standard which is more strict with emissions of industrial boiler.These factors hinder the spread of coal washing sludge fluidized bed combustion technology.To improve the efficiency and reduce emissions,studying the characteristics of coal washing sludge during fluidized bed combustion has become more urgent and important.At first,this paper describes the concept and development of coal washing and characteristics of coal washing sludge briefly.Then,the present Chinese and foreign researches in disposal of coal washing sludge by combustion technology are introduced.Next,the basic properties of the coal washing are studied;the factors,which influence combustion characteristics and pollutant emissions of coal washing sludge,are studied through small-scale fluidized bed combustion experiment.A series of industrial experiments are carried out on the large-scale coal washing sludge circulating fluidized bed boiler to verify feasibility of the way to dispose coal washing sludge by fluidized bed combustion technology.Some analysis of ash,produced by small-scale fluidized bed combustion,are made to put forward some ways to utilize ash preferably.Finally,co-generation system of coal washing sludge circulating fluidized bed boiler is propounded.All these works provide experiences for the development of larger fluidized bed boiler.For the basic properties of the coal washing,main study includes the composition,content of heavy metals,mineral type,distribution of particle size,pyrolysis and combustion characteristic and the ash melting point.Furthermore,pyrolysis and combustion kinetics parameters are obtained by the Coasts method.These works provide basic data for further study on the coal washing sludge fluidized bed combustion characteristics and contribute to reasonably design burning experimental condition.For coal washing sludge small-scale circulating fluidized bed combustion experiments,the changes of combustion performance with O₂content and influence on NO_X by O₂ content,the secondary air?SA?rate and height of secondary air are discussed.For the ash produced by small fluidized bed combustion,the particle size distribution,pore structure,mineral content and the impact on burn-out characters of coal washing sludge by particle propertied are researched,meanwhile the methods of ash utility is proposed.For industrial experiment on coal washing sludge circulating fluidized bed boiler,the main design ideas and technical characteristics of the boiler are introduced.The advantages of horizontal separator,the rationality of the furnace combustion share and pollutant emission characteristics are argued.According to the experimental results and the previous analyses,some suggestions are put forward to reduce release of pollutants.It is proved that the coal washing sludge circulating fluidized bed boiler can run stably,combustion efficiency can reach more than 99%and the thermal efficiency can reach 87.85%.The experimental researches in this paper provides valuable data and reliable experiences for the development of the coal washing sludge circulating fluidized bed combustion technology.