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 sorbent's 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.