Chlorine Migration And Collaborative Removal Of SO₃ In Coal-fired Flue Gas Dechlorination

"Coal-fired Flue Gas Dechlorination for Zero-discharge of Desulfurization Wastewanter" is a brand new solution to the problem of desulfurization wastewater in coalfired power plants.The pilot platform was built up for proving the results of chemical kinetic simulation and laboratory experiments.In this paper,the back injection of desulfurization wastewater,the direction of dechlorination products and the synergistic removal of SO3 were mainly studied.The experimental results show that when the molar ratio of Na/Cl reaches 7.58 and 8.93 respectively,the removal efficiencies of HCl from coal-fired flue gas can rise up to 70% with Na OH solution prepared by clear water and desulfurization wastewater.In the experiment of clear water,it was found that capture efficiency of dust chlorine is linearly related to the removal efficiency of gaseous chlorine in means of digesting ash sample collected by filter cartridge.Part of the removed chlorine might be adsorbed in the glass fiber of filter cartridge in the form of molecular chlorine salt or agglomerated fine particles.XPS analyses show that there is no characteristic peak of chlorine in original ash sample.After flue gas dechlorination of clear water,the area of the characteristic peak of inorganic chlorine in the ash increases obviously,which proves that the chlorine salt produced by dechlorination exists in the fly ash.The inorganic chlorine increases when the desulfurized wastewater is injected into the flue gas,which indicates that the chlorine salt in the desulfurized wastewater can be solidified into the fly ash.SEM-EDS results reveal that the fly ash absorbs more flocculent particles and Na content increases after flue gas dechlorination.The fine particles and floccules in the ash sample increases significantly,and the elements Na,Ca,Mg,Fe,S increase significantly under the action of desulfurization wastewater.It is uncovered that the chlorine salt produced by dechlorination and the pollutants in desulfurization wastewater are solidified and agglomerated with fly ash.Due to the low temperature range,the concentration of sulfuric acid in the flue gas will not be increased during the conversion of SO3 to gaseous sulfuric acid.In the range of 80-110?,the process of dechlorination will reduce the concentration of sulfuric acid condensate by about 5%.For the deposition rate of condensed sulfuric acid,the gain effect caused by the decrease of SO3 concentration is much greater than that caused by the increase of water vapor volume fraction.The speed of sulfuric acid condensate decreased from 3×10-5g/(m2?s)to 0.25×10-5g/(m2?s),with a decrease of 91.7%,which is beneficial to equipment after desulfuration.