Numerical Simulation On Co-combustion Of Pulverized Coal With Sludge In A 600MW Coal-fired Boiler

With the development of urbanization in China,the sludge production is increasing day by day.With the increasingly strict environmental protection standards,sludge treatment has become an important research topic.Sludge production is large,if not properly treated,will occupy space and pollute the environment.Among many sludge treatment methods,incineration method has been widely used for its advantages of harmless,sludge reduction and recycling of sludge heat.As a kind of sludge incineration technology,coupled sludge combustion power generation technology in coal-fired power plants can treat sludge thoroughly and harmlessly.At the same time,using the calorific value of sludge to generate electricity can reduce coal consumption in power plants.It has the advantages of strong adaptability,large processing capacity and thorough harmless treatment,and is a better sludge treatment method.In this thesis,a tangentially fired pulverized coal boiler for 600MW unit was taken as the research object,and the combustion characteristics of pulverized coal and sludge co-combustion were analyzed by numerical simulation method.The velocity field,temperature field and nitrogen oxide distribution under various working conditions were obtained.The model is verified by taking BMCR working condition as a benchmark.The calculation results show that the velocity field and temperature field are distributed reasonably,and the tangent circle is formed well.The error of furnace outlet parameters is within 10%,which can simulate the boiler operation.After mixing the sludge,the flue gas velocity field in the furnace changes little,and the overall temperature in furnace decreases.When the mixing ratio is 10%and the moisture content increases,the temperature of the flue gas at the furnace outlet decreases and NO_xemission increase.If the moisture content increases from 10%to 40%,NO_xemission increases from295.8mg/m~3to 310.7mg/m~3.As the mixing ratio increases,the furnace outlet temperature decreases and NO_xemissions decrease.When the mixing ratio increases from 3%to 10%,the furnace outlet temperature decreased from 1343.8K to 1335.8K,and NO_xemission increased from 295.8mg/m~3to 310.7mg/m~3.When the mixing ratio is greater than 20%,the furnace temperature drops greatly,and it is not suitable for blending at this time.At 40%moisture content,compared with burning pulverized coal alone,the average temperature of the furnace outlet at10%mixing ratio is reduced by 18.1K,and NO_xemission at the outlet is reduced by 10.8%.When mixed with sludge under different loads,the water evaporates and absorbs heat,the overall temperature level of the furnace decreases.CO and HCN production in C,D and E burner areas increases,and NO_xproduction is inhibited.After mixed with 10%sludge,the average temperature peaks at 600MW,510MW and 450MW are reduced by 15.5K,8.2K and 3.1K respectively,and NO_xemissions are reduced by 10.9%,13.1%and 8.1%respectively.Under the three air distribution modes,the economy of equal air distribution and positive tower air distribution is better than that of inverted tower air distribution.For power plant operation,the air volume arrangement is reasonable and the tangential distribution is reasonable,so the equal air distribution is the best air distribution mode.