System Modeling And Economic Optimization Of SO₂ And NO_x Ultra-low Emission System For Industrial Coal-fired Boilers

As an important thermal power conversion equipment,coal-fired industrial boilers have been in the forefront of energy consumption in China’s industrial industry,but SO₂and NO_X produced by coal-fired boilers have caused great harm to the atmospheric environment.The Clean Heating Planning of North China clearly requires that by the end of 2021,50%-60%of coal-fired heating in the 15 northern provinces should meet the requirements of ultra-low emission of pollutants.Different emission reduction technologies,such as electricity price,unit price of consumable materials and operating load,make the cost of pollutant control more than double.It is necessary for the economic operation of the system to select and optimize the operation strategies of SO₂ and NOx ultra-low emission reduction systems.It is also an important development direction for sustainable implementation of pollutant emission reduction.Therefore,this paper carries out research on SO₂ and NO_X ultra-low emission system modeling and economic optimization of industrial coal-fired boilers.Based on the analysis of industrial operation case data,this paper presents the typical ultra-low emission system scheme selection,variable load operation and cost comparative analysis method.Aiming at the ultra-low SO₂ emission:Taking typical wet desulfurization process as the research content,the static economy of three different desulfurizers,MgO,CaO and CaCO₃,is analyzed when the electricity price,load and key operation parameters change.Combining with the difference of typical operation load change and emission reduction target,the variation law of operation cost of different processes is given when the load is reduced,and based on"operation"The basis and method of selecting the system with the lowest cost are that when the electricity price is lower than 0.25 yuan/kWh,the economy of using CaCO₃ is the highest,and when the electricity price is higher than 0.65 yuan/kWh,the economy of using MgO is the highest.By establishing the main energy consumption equipment model and optimizing the operation parameters of the equipment,the variable-load operation optimization of a 70 MW coal-fired boiler desulfurization system is carried out.When the load decreases from 90%to 70%,the variable-frequency regulation of the booster fan can save 38.88 yuan/h;when the load decreases from 100%to 50%,the variable-frequency regulation of the oxidation fan can save 21.94 yuan/h;when the load decreases from 100%to 75%,a slurry pump can be closed to save energy.It can reach72.32 yuan/h.Aiming at the ultra-low emission of NOx,taking the combination of low nitrogen combustion and SCR flue gas denitrification process as the research content,the economic operation parameters of combustion process optimization,flue gas recirculation and SCR system for different emission reduction targets are analyzed,and the combination selection,optimization design and operation methods are given.A 130t/h circulating fluidized bed industrial boiler operation data is used as the database of training model.Based on LLSVM algorithm,a combustion optimization model of denitrification system is established on MATLAB software platform.GA genetic algorithm is used to modify the accuracy of model prediction,and PSO particle swarm optimization algorithm is used to optimize the input and output variables of the model.The optimal values of NO_X emission concentration and coal consumption per ton of steam under different loads are obtained.The economic operation modes of flue gas recycling and SCR systems under different emission reduction targets are established.Combustion optimization and SCR systems are used to implement special emission standards.The operation mode of flue gas recycling is more economical.When implementing the ultra-low emission standard,it is more economical to adopt the layout mode of 10%circulating air volume plus three layers of catalyst.