Experimental Study On SO2 And CO2 Recovery From Flue Gases By Ammonia

The gaseous pollutants emission control in coal combustion process is the essential requirement for the harmfulness mitigation from acid rain, greenhouse effect, and ozone depleting, and also for the sustainable development. Ammonia (NH3) has shown its effectiveness and advantage in pollutants reduction.The research work includes two parts: 1.experimental study of sulfur dioxide removal from flue gases by ammonia injection; 2.experimental study of carbon dioxide removal from flues gases by ammonia scrubbing. A set of experimental equipment was designed to remove several gas pollutants in power plant by ammonia. By this experimental equipment, we can have experimental study of CO2 and SO2 removal respectively.In the desulfuration experiment, we removed SO2 from the artificial flue gases by ammonia and water vapor injection. The factors, especially the key one which affects the removal efficiency and reaction dynamics were collected and analyzed. The results show: that the method of ammonia injection is effective to control SO2 emission. At all the operating temperature, the SO2 reduction ratio was more than 60%. The more chemical reaction time was needed for reaching a steady ratio at higher temperature. The reduction ratio was still high when the temperature was higher than 80℃. The reaction time for SO2 removal was almost the same in the temperature window of 40℃~85℃. On the basis of experimental results, the suggestion was given in this report that the process temperature should be controlled below 60℃ or even lower in the actual installation for SO2 reduction by NH3 injection.In the second part, in order to remove CO2 thoroughly, the diluent ammonia solution was sprayed from the top of the absorption column, fully mixing with the artificial flue gases from the bottom. The results demonstrate: the method of ammonia excels the traditional ones including physical absorption, chemical absorption, membrane separation and cryogenics method for it can reach a high removal efficiency (from 95% to 98%) and a rapid removal rate under a proper reaction condition. The ammonia scrubbing capacity can be calculated to be 0.34mol CO2/1mol NH3 or 0.87kg CO2/1kg NH3, which is higher than that of MEA method. Results also indicate that temperature plays a key role in the CO2 removal and atabout 33℃,the efficiency reaches its highest. The CO2 removal efficiency will improve with decreasing of the CO2 concentration and increasing of ammonia solution concentration. It is proved that ammonium bicarbonate is the main product of the CO2 -NH3 reaction in this study. Ammonium bicarbonate is a cheap, widely used fertilizer in China and has business value.