Experimental Study On The Promoting Dissolution Of Limestone And Strengthening SO₂Absorption By WFGD Additives

Fast development of economy and society is closely linked with heavy consumption of energy, SO2pollution caused by coal combustion is serious day by day in our country. At present limestone-gypsum wet flue gas desulfurization technology is being widely applied all over the world because of its advantages: mature technology and reliable operation, high desulfurization efficiency, widespread and cheap absorbent. Some research showed that the additives can promote dissolution of limestone and strengthen SO2absorption effectively in the WFGD process, and then reduce the operation cost, so it is very important to study on highly active WFGD additives. This dissertation studies on promoting dissolution of limestone and strengthening SO2absorption by WFGD additives.The impact of additive on the dissolution of varied limestone was investigated by pH-stal method. The dissolution fractions of varied limestone are different, the highest is65.3%, the lowest is42.3%; in the presence of additive, all the dissolution fractions of limestone increase obviously, in which, the highest is92.1%, the lowest is75.6%;34.2%is the most increase range and the least is25.9%; the effects of CaO and MgO contents on the dissolution of limestone is related with their form of existence and degree of crystallinity. For example. CaO of Ning Hai and Wu Sha Shan limestone exists in the form of calcite and the degree of crystallinity is lower, so they are easy to dissolution, but the dissolution fractions of Lu Zhou and Ji Ning limestone with few calcile and more dolomite are lower.The impact of gypsum, fly ash,Fe2O3, Al2O3, SiO2and Al3++F-on the dissolution of limestone was studied by pH-stat method. In which, Al3+F-complexes inhibit (he dissolution of limestone most seriously; the presences of gypsum, fly ash, Fe2O3,Al2O3,SiO2and Al3+F-decrease the effect of additives, it is obvious for additive2, because these impurities decrease the effective contact areas of the additive and limestone particles; Al3+F-have the negative effect mostly to composite additives c, because the clathrate generated by Al3+and F attaches to the limestone particles closely, hinders the fully contact of H+and limestone particles.The experiment of additives strengthening SO2absorption was investigated in a stirred tank reactor,In which, the composite additives are optimal, when the concentrations of additive3and additive5are5mM and ImM respectively in composite additives a, SO2has the best absorption effect; when the total concentration of additive3and additive4is5mM and the raio is1:4in the composite additives b, SO2has the best absorption effect; when the total concentration of additive3, additive4and additive6is5mM, the ratio is1:4:5in the composite additives c, SO2has the best absorption effect; in which, composite additives c (5mM,1:4:5)> composite additives a (5mM+1mM)> composite additives b (5mM,1:4).