Study On Combustion And Wear Characteristics Of Circulating Fluidized Bed Boiler Mixed With Petroleum Coke

With the vigorous development of petroleum refining industry,as a by-product of refining process,the output of petroleum coke is also increasing year by year.Facing the increasingly prominent energy and environmental problems,achieving efficient and clean utilization of energy has become the primary issue of social and economic development.Circulating fluidized bed boilers have the advantages of wide fuel adaptability and low pollution.Combustion of petroleum coke and coal in circulating fluidized bed boilers can not only comprehensively utilize petroleum coke resources,but also reduce environmental pollution.It is an important way to rationally and effectively utilize petroleum coke.The wear and tear of CFB boilers is an important problem affecting the long-term and efficient operation of boilers.In this paper,a 410 t/h CFB boiler in a power plant is taken as the research object,and the combustion numerical simulation of petroleum coke blending is carried out.The flow field and combustion situation in the furnace under different mixing ratios of primary and secondary air and petroleum coke are discussed.In the simulation process,non-premixed combustion model,standard turbulence model and P-1 radiation model are adopted,and UDF is compiled to connect the outlet of the boiler with the outlet of the return port.Connect to make the boiler's external circulation complete.The simulation results show that the circulating fluidized bed boiler flows in a "ring core".The mixing of petroleum coke does not affect the velocity field in the furnace.Appropriate increase of primary air and decrease of secondary air will help the flow field of "ring core" move towards the center of the furnace and reduce the erosion and wear of the water wall.The mixing of petroleum coke delays the ignition of coal,but the combustion intensifies after ignition.With the increase of the proportion of petroleum coke,the combustion increases.With the increase of temperature burning area,the overall temperature of the boiler rises,and excessive temperature will affect the safe operation of the boiler.Therefore,the proper mixing ratio(less than 50%)and the ratio of primary and secondary air in actual boilers are helpful to the safe and stable operation of boilers.In view of the problem of boiler wear,predecessors have done a lot of theoretical analysis and simulation experiments.The basic distribution law of particle concentration in circulating fluidized bed boiler is obtained,and many effective anti-wear measures are put forward.Therefore,on the basis of previous theoretical and experimental research,combined with numerical simulation and simulation methods,this paper presents a BP neural network prediction model which can predict the wear degree of different areas of water wall in furnace under different operating conditions,and carries out network testing.The test results show that the prediction error of the model is small,and it has good generalization ability,and can be used for actual boiler operation.Provide guidance.Aiming at the problem of pollutant emission from boilers,the combustion system of 410 t/h boilers is modeled by BP neural network combined with the actual operation data of boilers.Then the weight and threshold of BP neural network are optimized by genetic algorithm.The GA-BP boiler combustion prediction model of carbon content in fly ash and NO_X emission is established,and multi-objective optimization is carried out.The optimization results are as follows: The application has been carried out in the rated working condition of the boiler to realize the economical operation of the boiler with high efficiency and low pollution.