Study On PM_2.5 And SO₃ Acid Mist Removal By Wet Electrostatic Precipitator

With the development of China's industrialization process,air pollution is increasingly serious.Fine particulate matter(PM2.5)and sulfuric acid mist are one of the most harmful atmospheric pollutants at present.Coal-fired power plants are the major emission source of PM2.5 and sulfuric acid mist.In this paper,mechanism and test research were carried on about removing PM2.5 and sulfuric acid mist by line pipe type wet electrostatic precipitator,in order to deal with the requirement of ultra-low emission transformation and the realistic problem that removal efficiency of PM2.5 and sulfuric acid mist with exiting removal equipment is not high.This paper designed and built a wet electrostatic precipitator platform.Tests were conducted with the help of many test devices,such as electrical low pressure impactor(ELPI+),dust sampler,acid mist sampling and analysis device,flue gas analyzer,temperature and humidity transmitter,scanning electron microscope.This paper analyzed flue gas particles' morphology,elemental composition and particle size distribution at the inlet of wet electrostatic precipitator at first.The analysis results show that gypsum and fly ash are the main components of the flue gas particles at wet electrostatic precipitator inlet.From the point of view of number concentration distribution,PM2.5 is the main.The effects of operating parameters such as operating voltage,inlet flue gas temperature,flue gas flow rate and flue gas humidity on the removal effects of PM2.5 from wet electrostatic precipitator were investigated.It was found that the adjustment of the parameters could affect the removal efficiency of PM2.5 by wet electrostatic precipitator in varying degrees.The influence of voltage is the largest.Voltage increases from 40kV to 60kV,PM2.5 removal efficiency increases from 60%to 80%.The relative humidity of inlet flue gas increases from about 80%to supersaturated state,and the removal efficiency increasing range of different particle size is different.Heterogeneous condensation can raise the removal efficiency of PM2.5 to more than 90%.It can be seen that internal heterogeneous condensation is of great help to further improve the performance of wet electrostatic precipitator.On this basis,the design idea of a kind of energy-saving condensing wet electrostatic precipitator was put forward.It combines heterogeneous condensation with wet electrostatic precipitator.The performance research of remove sulfuric acid mist by line tube type wet electrostatic precipitator was carried on in this paper.The effects of operating voltage,inlet concentration on the removal efficiency of acid mist were tested.It was found that removal efficiency of sulfuric acid mist by wet electrostatic precipitator is not high overall,between 30%and 60%.Voltage increases from 40kV to 60kV,acid mist removal efficiency is improved by about 20%.At the same time,experiments studied promoting effect of heterogeneous condensation in wet electrostatic precipitator on the removal of sulfuric acid mist.The results show that heterogeneous condensation can improve the removal efficiency of sulfuric acid mist by wet electrostatic precipitator,but the improving range is smaller,compared to PM2.5.The effect of SO2 oxidation in wet electrostatic precipitator was also investigated.It was found that partial SO2 was removed due to oxidation to SO3.The results show that the removal efficiency of SO2 is lower than 40%.The effects of voltage and inlet SO2 concentration on the removal efficiency of SO2 are different.The SO3 generated by SO2 oxidation is much larger than that of removed part by wet electrostatic precipitator.This paper also analyzed the removal performance of dust?sulfuric acid mist and droplet by wet electrostatic precipitator in coal-fired power plants on the basis above.Actual test results show that the removal efficiency of total dust?PM10/PM2.5?sulfuric acid mist and droplet by wet electrostatic precipitator in coal-fired power plants are about 90%?85%?60?75%and 70?80%,respectively.With the increase of boiler load,the concentration of the pollutants above increase slightly at the inlet and outlet of wet electrostatic precipitator,and the removal efficiency decrease slightly.With the increase of sulfur content in coal,the total dust concentration at the inlet and outlet of wet electrostatic precipitator and total dust removal efficiency are both increased,and the removal efficiency and outlet concentration of droplet do not change much.When burning high suffer coal,obvious blue smoke phenomenon may also appear,even if wet electrostatic precipitator is installed.