Simultaneous Removal of SO2 and NO from Flue Gas with Calcium-Based Sorbent at Low Temperature

The calcium-based sorbent for simultaneous removal of SO2/NO was prepared with KMnO4 as additive. The activity of sorbent was studied individually in a fixed bed at low temperature. The experimental results showed that KMnO4 could highly enhance the sorbent ability for NO capture. It was found that temperature rise could improve SO2 capture, but could not influence NO removal so distinctively. The presence of water vapor in the gas could prominently improve the sorbentʹs ability to capture SO2 and NO, and an optimal relative humidity existed for NO removal. O2 and KMnO4 were found to play an important role in NO removal. The optimum condition for simultaneous SO2/NO removal was studied, including reaction temperature, O2 concentration, and relative humidity in the flue gas. XRD and IC analysis indicated that SO2 was absorbed as sulfate with KMnO4 present and as calcium sulfite with KMnO4 absent. It was further deduced from the experimental results that NO was first oxidized into NO2 and then was removed by reaction with calcium hydroxide and calcium sulfite into nitrate and nitrite.