Study On Preparation And Performance Of Fly Ash-Lime Sorbent For Flue Gas Desulfurization And Denitrification

In this paper, investigations are about the preparation technics of fly ash-lime sorbents, the characteristics in macro-structure of the sorbents and the performance of the sorbents in desulfurization and denitrification. The sorbents are prepared with fly ash and lime in hydration. In the investigation, the ways of hydration are normal pressure hydration, steam hydration and pressured hydration. The conditions of hydration, such as ratio of fly ash to lime, hydration time, and hydration pressure are investigated. The result shows that when normal pressure hydration is used, with the ratio of fly ash to lime increased, specific surface area, pore volume, and average pore diameter are decreased, but median pore diameter is increased. With hydration time increased, specific surface area and pore volume are increased, and it increases a little when hydration time more than 3h. Average pore diameter and median pore diameter are decreased, when the hydration temperature is 25℃and they are increased when the hydration temperature is 90℃. The optimum specific surface area is 74.71m2/g, median pore diameter is 227.66?, average desulfurization efficiency is 76.89% and average denitrification is 36.27%. When steam hydration is used, with the steam pressure increased, specific surface area and pore volume are increased, and average pore diameter and median pore diameter are increased at first and decreased later. When the steam pressure is 0.8MPa, average pore diameter and median pore diameter reach to the top. The optimum specific surface area is 62.63m2/g, median pore diameter is 275.11?, and average desulfurization efficiency is 77.47% and average denitrification is 36.76%. When pressure hydration is used, with the hydration pressure increased, specific surface area and pore volume are decreased, and average pore diameter and median pore diameter are increased at first and decreased later. When the hydration pressure is 1.2MPa, average pore diameter and median pore diameter reach to the top. The optimum specific surface area is 73.23m2/g, median pore diameter is 277.18?, and average desulfurization efficiency is 78.64% and average denitrification is 37.04%.On the basis of the above research, the paper further research on the macro-structure effect on desulfurization and denitrification. The result shows that the optimum macro-structure for desulfurization and denitrification should be specific surface area is more than 40m2/g, and median pore diameter is more than 200?. When researched on the technics condition effect on desulfurization and denitrification, the hydration variables of interest to this study are reaction temperature, relative humidity, the concentration of SO2 and NOx, the ratio of NO2 to NOx. The paper concludes the macroscopical dynamics equation and it describes the key technics condition effect on desulfurization and denitrification.