Simultaneous removal of NOx, SO2, CO and Hg from flue gas by ozonation. Pilot plant studies

The results of pilot plant investigations of simultaneous removal of NOx, SO2 and Hg from flue gas with ozone as the oxidizing agent and the spray tower absorber with NaOH solution as the absorbent have been presented. Flue gas was delivered into the pilot plant at the flow rate of 200 m3/h from the coal fired OP-430 boiler. The effectiveness of NOx removal was over 95% when the molar ratio O3/NO reached 2.0. Sulfur dioxide was practically completely washed out from flue gas in the absorber at the liquid-to-gas ratio 7.5 dm3/m3. The effectiveness of Hg removal in the studied system was approximately 80%. It was pointed out that CO concentration in flue gas could considerably increase the ozone consumption. The effect of carbon dioxide in flue gas on the chemistry of absorption due to hydroxides conversion into carbonates and bicarbonates was noticed.