Effect of high⁃content iron ash on removal of SO2 by calcium⁃based desulfurizer

A large amount of SO2 gas released by coal⁃burning brings great harm to human life and production activities. Meanwhile，the accumulation of solid waste fly ash discharged by coal⁃burning can cause dust pollution. Re⁃ ducing SO2 emissions and fly ash from coal⁃burning have long been the main research topics for many researchers. The main components in fly ash are SiO2 ，Al2 O3 ，Fe2 O3， and CaO，among which Fe2 O3 and CaO have a certain SO2 re⁃ moval activity. The desulfurization efficiency of CaO is higher，but the calcium utilization rate is lower. Its utilization rate may be improved by appropriate modification methods. In this paper，the rich iron oxides in fly ash were extracted by wet magnetic separation，thus the high⁃content iron ash was obtained. Calcium oxide was modified by hydration with the high⁃content iron ash and the calcium⁃based desulfurizer was obtained. The SO2 removal experiments were carried out on the fixed bed evaluation system. Combined with the results of XRD，BET，and FTIR，the influence of high⁃content iron ash on the SO2 removal performance of calcium⁃based desulfurizer is revealed. The results show that calcium⁃based desulfurizer modified by the high⁃content iron ash has good desulfurization ability，and the breakthrough time and sulfur capacity are 26 min and 14.87 mg / g，respectively. The hydration modification of calcium oxide and high⁃content iron ash can increase hydrates and the active components of iron oxides，and the active center of the desulfurization reaction is transferred from CaO to Fe2O3particles. Fe2O3 has the function of oxygen storage and release，and is attached to the surface of CaO particles，resulting in excellent pore structure on the surface of desulfurizer. It is easy for SO2 to enter the desulfurizer through the pores，thus，the desulfurization reaction time is prolonged and the desulfurization capacity of desulfurizer is improved. On the other hand，Fe2 O3 can promote the conversion of SO adsorbed on the desulfurizer surface into SO ，and the final removed SO exists in the form of SO2- .The results of the kinetic analysis show that the chemical adsorption removal plays a leading role in adsorption desulfurization， and the chemical adsorption kinetics follows the quasi second⁃order kinetic model. The high⁃content iron ash may en⁃ hance the chemical removal ability of calcium⁃based desulfurizer for SO2.