Experimental Study On Fine Particles And Soluble Salts From Flue Gas After Desulfurization

In recent years,the atmospheric smog has aroused the public widespread concern,PM_2.5emission control has become an urgent problem to be solved.In this paper,the problem of ultra-low PM_2.5 emission from flue gas of coal-fired power plants after desulfurization is studied.The agglomeration of PM_2.5 fine particles is made by adding Acoustic agglomeration device in front of wet electrostatic precipitator,which improves the removal efficiency of fine particles by wet electricity,after wet electricity,the flue gas reenters the water-borne flue gas heat exchanger（MGGH）.Through the cooling and water removing function of the flue gas cooler,the water-soluble ions in the flue gas are removed,and the formation of fine particles is reduced after the soluble ions enter the atmosphere,further reduce emissions,thereby achieving ultra-low emissions of fine particulate matter.The effects of sound pressure level,sound frequency,concentration of fine particles and fluegas residence time on the agglomeration efficiency of fine particles were studied,the highest agglomeration efficiency is 52.93%under the optimized working conditions with reasonable adjustment of various factors.On this basis,the effects of spraying and chemical agglomerating agent were further coupled,and the reasonable dosage of spraying and agglomerating agent was obtained.The agglomerating efficiency was increased to 79.76%by optimizing the experimental conditions.After wet electrostatic precipitator,a new type of water-medium flue gas heat exchanger was used to remove salt and Whiten the flue gas,effectively reduce the content of soluble ions in the flue gas,and recover the water and residual heat.In this paper,the effect of Mggh cooling section on the removal of soluble salts in flue gas was investigated,the variety and content of ions in flue gas were analyzed under different temperature drops,and the water-soluble ions in flue gas were collected by scavenge method,the Ion concentration was measured by ICP/IC/UV photometer.The results showed that the removal efficiency of the eight main ions in the flue gas was about 70%at 30°C.the removal efficiency of NH₄⁺and K⁺was 66.2%and 79.3%respectively.The effects of the concentration of 13.2/17.6/22.0g/L and the ratio of 6/9/12L/m³on the soluble ions in flue gas were analyzed.The migration and transformation of soluble ions were also investigated.The experimental results show that the removal efficiency of PM_2.5by wet ESP is 76.4%without opening the acoustic agglomerator.The removal efficiency increased to 81.3%when the acoustic agglomerator was opened.The total removal efficiency of PM_2.5 was 84.7%when the mass concentration of PM_2.5 was 15.46mg/m³ at the inlet and 2.37mg/m³ at the outlet of MGGH.Using FORTRAN program and VB as interface,the design software of PM_2.5 ultra-low emission integrated coupling system is developed.Taking 2×150t/h coal-fired boiler as an example,the calculation and scheme design of PM_2.5ultra-low emission system coupled with acoustic agglomerator,wet electrostatic precipitator and MGGH are carried out.