Study On Energy Efficiency Evaluation Of Wet Flue Gas Desulphurization Tower In Coal-fired Power Plant

In recent years,the ultra-low emission standards of coal-fired power plants have become increasingly stringent,and the energy and material consumption of wet desulphurization towers increases gradually with the improvement of the emission standard.Therefore,it is urgent to establish an energy efficiency index system to evaluate the desulfurization performance and cost of the desulfurization tower,which will be of great significance to improve the comprehensive performance of power plants.In this paper,the law of heat and mass transfer and the characteristics of energy consumption in the desulfurization tower are investigated by theoretical and numerical simulation methods.The following conclusions are obtained:(1)The process of heat and mass transfer between the inlet of the desulphurization tower and the bottom spray layer changes drastically and this section can be defined as the "main heat transfer zone"and the "main absorption zone";Between the bottom and top spray layers,the flue gas temperature and SO2 concentration are slowly reduced.(2)When all the spray layers are turned on at the same time,the SO2 removal amount at the lowermost layer is the smallest,and the energy consumption is also the lowest.The larger the SO2 removal amount in the upper spray layer is,the higher the energy consumption is.(4)The desulfurization efficiency is positively correlated with the liquid-gas ratio and the number of spray layers,and it's inversely proportional to the inlet flue gas volume,flue gas flow rate in the tower,inlet SO2 concentration and inlet flue gas temperature,while the energy consumption is positively proportional to these six parameters.Then,the relationship between desulfurization performance and energy consumption of the desulfurization tower is measured.This paper introduces the desulfurization energy consumption value to judge the operation performance of the desulfurization tower.When all spray layers are turned on at the same time,the desulfurization energy efficiency value of the second spray layer is the best,which is 1.4501kg/KWh,indicating that the operation economy of this spray layer is the best,and the contribution rate of the fourth spray layer is the largest.The desulfurization energy efficiency value of the lowest spray layer is the second,which is 1.3937kg/KWh.The energy efficiency of the third spray layer and the top spray layer ranks the third and fourth,indicating that the higher the spray layer,the lower the desulfurization energy efficiency value,and the worse the operation economy.The contribution rate of this spray layer is lowest in the four spray layers.The desulfurization energy efficiency value is directly proportional to the SO2 concentration at the inlet,inversely proportional to the number of spray layers,liquid-gas ratio and inlet flue gas temperature,which rises and then falls with the change of inlet flue gas volume and flue gas flow rate in the tower.At the same time,according to the heat and mass transfer rules in the desulfurization tower,the energy consumption characteristics and operation performance of the desulfurization tower,the desulfurization tower can be divided into index structure levels.The combination of subjective AHM and objective entropy weights was selected,and a comprehensive energy efficiency evaluation system for desulfurization tower based on improved Bayesian model was constructed.Finally,this evaluation system is used to perform multi-objective evaluation of a typical coal-fired power plant wet desulfurization tower from the desulfurization level,energy consumption level and operation level,and to evaluate its overall energy efficiency level.According to one month operation data evaluation and analysis of the power plant,the excellent rate of operating conditions is 5%,the good rate is 68%,the general rate is 25%,and the difference rate is 7%,which showed that the overall energy efficiency of the unit was better.It Is suggested that managers could sacrifice part of energy consumption and operation economy of desulfurization tower to improve desulfurization level.The energy efficiency rating of the desulfurization tower for each working condition and the guidance and suggestions for the poor working conditions can provide solutions for improving the efficiency of coal-fired power plants.