Study And Optimization Of SO₂ Emission Model In Circulating Fluidized Bed

As a kind of clean coal combustion technology.circulating fluidized bed boiler can inhibit NOx generation and desulfurization in the furnace through low temperature combustion,so as to achieve low cost pollutant emission control.With the implementation of ultra-low emission standards of air pollutants in thermal power units.a large number of CFB units adopt the operation mode of combined desulfurization to achieve ultra-low emission of SO2.Therefore.it is of great significance to explore which operation mode can not only meet emission standards but also realize low-cost desulfurization.The following work is carried out in this paper:(1)Based on the analysis of desulfurization mechanism and influencing factors of the internal and external desulfurization systems of circulating fluidized bed furnace.the prediction model of SO2 emission concentration of the internal and external desulfurization systems of circulating fluidized bed furnace was established.The best modeling method was selected by comparing the accuracy and generalization ability of three different algorithms,namely support vector regression machine(SVR),LightGBM and short and long time memory neural network(LSTM).Due to the large number of variables selected in the initial modeling,the coupling between variables may lead to insufficient generalization ability of the model.Therefore.Pearson correlation coefficient(PCCs),maximum information coefficient(MIC)and meanbased impact value analysis(MIV),three variable selection methods are used to improve the model through dimensionality reduction of input variables,so as to improve the generalization ability of the model.The improved model is verified under different working conditions,and the experimental results show that the accuracy and generalization ability of the model can achieve the expected results.(2)The economic model of the desulfurization system of the furnace and inside and outside the furnace is established by studying the desulfurization process of the furnace and inside and outside the furnace,including the raw material cost of desulfurization in the furnace,the electricity cost,the raw material cost of desulfurization outside the furnace,the electricity cost,the industrial water cost and the by-product gypsum income cost.With the cost model of the combined desulphurization system established as the objective function and the SO2 ultra-low emission standard as the constraint,the control quantity of the desulphurization system was optimized with the help of particle swarm optimization algorithm and the prediction model of SO2 emission concentration established in Chapter 3 under the condition of a certain density of limestone grout.The results show that the low cost desulfurization can be achieved on the premise of meeting the emission standard by using the desulfuration control quantity found.(3)The influence of different calcium-sulfur ratios in the furnace on desulfurization efficiency was calculated by working conditions,and the influence of the total sulfur amount received in coal and the change of limestone price on the combined desulfurization cost and the desulfurization share inside and outside the furnace was analyzed.The desulphurization costs before and after optimization of the 300MW circulating fluidized bed boiler combined desulphurization system and the desulphurization ratio inside and outside the furnace are compared and analyzed.Under 150MW and 300MW operating conditions,the total cost of desulfurization decreased by 10.1%and 4.6%,respectively.