Sulfur dioxide (SO2) and trace elements are pollutants derived from coal combustion. This study focuses on the simultaneous removal of S02 and trace arsenic oxide (As2O3) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range. Experiments have been performed on a thermogravimetric analyzer (TGA). The interaction mechanism between As2O3 and CaO is studied via XRD detection. Calcium arsenate [Ca3(AsO4)2] is found to be the reaction product in the range of 600-1000 degrees C. The ability of CaO to absorb As2O3 increases with the increasing temperature over the range of 400-1000 degrees C. Through kinetics analysis, it has been found that the rate constant of arsenate reaction is much higher than that of sulfate reaction. SO2 presence does not affect the trace arsenic capture either in the initial reaction stage when CaO conversion is relatively low or in the later stage when CaO conversion is very high. The product of sulfate reaction, CaS04, is proven to be able to absorb As2O3. The coexisting CO2 does not weaken the trace arsenic capture either.

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The calcium-based sorbent for simultaneous removal of SO 2 /NO was prepared with KMnO 4 as additive. The activity of sorbent was studied individually in a fixed bed at low temperature. The experimental results showed that KMnO 4 could highly enhance the sorbent ability for NO capture. It was found that temperature rise could improve SO 2 capture, but could not influence NO removal so distinctively. The presence of water vapor in the gas could prominently improve the sorbent's ability to capture SO 2 and NO, and an optimal relative humidity existed for NO removal. O 2 and KMnO 4 were found to play an important role in NO removal. The optimum condition for simultaneous SO 2 /NO removal was studied, including reaction temperature, O 2 concentration, and relative humidity in the flue gas. XRD and IC analysis indicated that SO 2 was absorbed as sulfate with KMnO 4 present and as calcium sulfite with KMnO 4 absent. It was further deduced from the experimental results that NO was first oxidized into NO 2 and then was removed by reaction with calcium hydroxide and calcium sulfite into nitrate and nitrite.

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