焦炉烟气钢渣湿法联合脱硫脱硝试验研究

Experimental study on simultaneous desulfurization and denitrification by steelmaking slag for coke oven flue gas

焦炭生产过程会排放大量的烟气,烟气中的SO2和NOx会造成环境污染。随着焦化行业大气污染物排放标准越来越严格,为解决焦炉烟气中SO2和NOx的污染问题,以钢渣为吸收剂,在自制小型鼓泡搅拌反应器中进行了焦炉烟气联合脱硫脱硝试验,研究了浆液温度、浆液浓度、烟气流量、SO2浓度、NO浓度对SO2和NO脱除效率的影响,并得到优化的运行条件。研究发现,温度升高会降低NO氧化的反应速率,导致生成的NO2浓度降低,从而使脱硝效率下降;浆液浓度升高会增大浆液体系的pH值,促进NO脱除;烟气流量增加,即停留时间减少会降低气液接触时间,导致脱硫脱硝效率降低;优化的运行条件为30℃、浆液浓度8%、烟气流量400 mL/min,在最优运行条件下,可实现脱硝效率50.7%,脱硫效率高于95%。钢渣同时脱硫脱硝过程机理研究表明:钢渣中溶解出的OH^-能维持浆液保持碱性,具有较高的缓冲pH值能力,从而有利于SO2和NOx的脱除;NO与O2反应生成NO2,NO2与OH^-反应生成NO-2和NO-3;NO2与NO结合生成极易溶于水的N2O3,N2O3再与OH^-反应生成NO-2,从而实现NOx的脱除。通过气相预氧化将部分NO氧化为NO2,然后NO2以及剩余的NO和NO2结合的N2O3被钢渣浆液快速高效吸收,达到NOx排放标准甚至超低排放标准,有利于钢渣湿法联合脱硫脱硝的工程化应用。

A large amount of flue gas is emitted from the coke production process,and sulfur dioxide(SO2)and nitrogen oxides(NOx)in the flue gas cause environmental pollution.With the increasingly strict air pollutant emission standard of coking industry,in order to solve the air pollution of SO2 and NOx from coke oven flue gas,the combined desulfurization and denitrification experiments of coke oven flue gas in the self-made bubbling reactor were carried out with steel slag as absorbent.The effects of reaction temperature,concentration of steelmaking slag slurry,gas flow,SO2 content as well as NO content on SO2 and NO removal efficiency were investigated,and the optimal operating condition was obtained.Results show that the increase in temperature will reduce the reaction rate of NO oxidation,resulting in the decrease in the concentration of NO2 produced,thereby reducing the denitration efficiency.The increase of slurry concentration will increase the pH value of the slurry and promote NO removal;the increase of the flue gas flow,that is,the decrease of the residence time will reduce the gas-liquid contact time,resulting in the decrease in the desulfurization and denitration efficiency;when the optimal operating condition is reaction temperature of 30℃,steelmaking slag slurry concentration of 8%and gas flow of 400 mL/min,the denitrification efficiency can reach 50.7%and desulphurization efficiency is above 95%.Research on the mechanism of simultaneous desulfurization and denitration of steel slag show that:the OH^-dissolved from steel slag can keep the slurry alkaline and has a high pH buffering capacity,which is beneficial to the removal of SO2 and NOx;NO reacts with O2 to form NO2,and NO2 reacts with OH^-to form NO-2 and NO-3;NO2 reacts with NO to generate N2O3,which is soluble in water,and N2O3 reacts with OH^-to generate NO-2,thereby achieving NOx removal.NO is oxidized to NO2 through the gas-phase pre-oxidation method.The results NO2 and N2O3 generated by the reaction of NO2 with NO can be absorbed efficiently by steelmaking slag slurry,thereby reaching the general or ultra-low emission standard of NOx,and achieving industrial application for simultaneous desulfurization and denitration using steelmaking slag.