Experimental Study On Coupling Of Desulfurization And Denitrification In CFB Boiler

With the function of in-furnace desulfurization technology and low nitrogen combustion,the Circulating Fluidized Bed Boiler(CFB boiler)can achieve lower pollutant emissions than pulverized coal boilers.Because of the strong adaptability to coal type,flexible load regulation and low pollutant emission concentration,CFB boiler is more and more widely used.Although the emissions of CFB boiler are lower,they still cannot meet the ultra-low emission standards(NOx?50mg/m3,SO2?35mg/m3,dust?5 mg/m3)required by China.The CFB still need to be equipped with flue gas desulfurization and denitrification equipment to control SO?and NO,emissions.Only with Selective Non-Catalytic Reduction(SNCR),the emissions of CFB boiler cannot steadily achieve the target of less than 50mg/m3 of nitrogen oxides emission,so supplementary measures are needed to the further control of nitrogen oxides.The Circulating Fluidized Bed Flue Gas Desulfurization(CFB-FGD)matching of CFB boiler can achieve ultra-low SO2 and dust emissions.It is found that the desulfurization system has a certain denitrification effect.In this article,we put forward an oxidizing denitrification module added to the CFB-FGD system of th e CFB boiler.Through the analysis and screening of oxidants,:we select the oxidant schemes.According to the characteristics of different oxidants,liquid-oxidants and gas-oxidants were designed to synergize desulfurization and denitrification systems,and carried out the experimental study on the coupling of desulfurization and denitrification.In this article,the coupling experiments of liquid-phase oxidizer and gas-phase oxidizer for desulfurization and denitrification were carried out on the 75t/h CFB boiler to investigate the efficiency,stability and economy of the system,and the effects of denitrification agent concentration and consumption,reaction temperature and boiler load on the denitrification effect were also studied.The main component of liquid-phase oxidant was sodium chlorite.During the experiment,the average desulfurization efficiency and denitrification efficiency were 97.9%and 66.70%respectively.The denitrification efficiency was obvious.It could achieve better denitrification effect under different loads,and had obvious promotion effect on the desulfurization efficiency.Based on the ozone as oxidant in synergistic desulfurization and denitrification by gas-phase oxidant,two stages of experiments were carried out.In the first stage,the desulfurization and denitrification efficiency of the system and the corresponding influencing factors were investigated.The denitrification efficiency could be maintained above 50%,the average denitrification efficiency was 75%,and the maximum efficiency was 85%.The desulfurization promotion effect of this method was obvious.In the second stage,the effects of different injection positions on the denitrification efficiency were investigated experimentally,and it was found that the denitrification effect of injection at flue was better than that at the bottom of absorption tower and inside of absorption tower.In conclusion,both liquid-oxidant and gas-oxidant can achieve well desulfurization and denitrification effect,which can be used as a supplementary means of denitrification for CFB boiler after matching SNCR.