Experimental And Theoretical Study On Limestone Wet Flue Gas Desulfurization

Lime/Limestone wet flue gas desulfurization(WFGD) technology with high desulfurization efficiency is being applied widely for coal-fired power plant all over the world. But the capital cost and operation cost are too expensive to be accepted by our consumer. In the thesis detailed researches on WFGD are carried out in order to decrease its capital cost and operation cost.Settling properties of solid particles in Limestone slurry and in gypsum slurry are studied through experiments. SO2 absorption properties in Limestone slurry and Limestone slurry with additives are studied based on gas-liquid-solid equilibrium theory and experiments. The effects of CO2 and SO2 in the flue gas and ion SO42 in the slurry on SO2 absorption capacity are analyzed based on the theory. The minimum L/G ratio is obtained. The enhancements of additives on SO2 absorption are studied through experiments. The effects of additives on SO2 absorption rate and SO2 absorption capacity are analyzed.Two WFGD scrubbers (impinge stream scrubber and spray scrubber) are built. The effects of slurry flux density and flue gas velocity on the resistance in the scrubbers and the effects of slurry flux density, flue gas velocity, circulating tank pH, SO2 inlet concentration, flue gas inlet temperature on desulfurization in the scrubbers are studied. The effects of additives (formic acid, sodium formate and adipic acid) on desulfurization in the scrubbers are also studied. The characteristics of the scrubbers are found. Optimum operation parameters are obtained. For the impinge stream scrubber, they are respectively slurry flux density 106.80m3/(m2h), flue gas velocity 2.6m/s and circulating tank pH 5.5-6.0; for the spray scrubber, they are respectively slurry flux density 215.66m3/(m2h), flue gas velocity 3m/s and circulating tank pH 5.5-6.0. The experimental results show that the enhancement of the additives on SO2 absorption in the spray scrubber is larger than those in the impinge stream scrubber. The enhancement of adipic acid on SO2 absorption is the largest in these additives. In addition, the impinge stream scrubber is compared with the spray scrubber. Their scopes of application are given. The two programs are designed to meet different SO2 emission standard.Dehumidification performances of rotating dehumidification plate are studied through experiments. The effects of slurry flux density and flue gas velocity on resistance and dehumidification efficiency are analyzed. Optimum parameters of rotating dehumidification plate are obtained considering resistance and dehumidification efficiency.The model of SO2 absorption in the impinge stream scrubber is established based on unsteady state mass transfer reaction theory. The model considers both instantaneous equilibrium reactions and reactions with finite rates. The results agree well with the experimental results. The model is useful to application of impinge stream scrubber in industry. The absorption and mass transfer resistancein different zone of the impinge stream scrubber are analyzed based on the model. The effects of limestone dissolution, gypsum crystallization and sulfite oxidation on SO2 absorption are also analyzed.The temperature and pressure distributions of flue gas in stack are calculated before and after WFGD is erected. The effects of flue gas temperature on stack performance are discussed after WFGD was erected. The proposal was put forward.