Novel study on the carbon dioxide removal by ammonia scrubbing

The energy production system is facing a new challenge on air pollution control. The new 'air pollutant', CO2, is one of the dominating species that contributes to the greenhouse effect. Several processes have been developed for removing CO2 from utility boilers. These include liquid solvent scrubbing, solid adsorbents, separation processes, and CO2 recycle, etc. Among which liquid solvent scrubbing, especially the one uses MEA as the scrubbing agent, is the most promising one. This paper attempts to study the feasibility of ammonia scrubbing for the removal of carbon dioxide from flue gas. The test method has the advantage of less space and equipment requirement since ammonia is used as a reagent for removing NOx in many boiler systems. Test results indicate the potential of CO2 reduction by NH3 scrubbing is very promising. The overall CO2 removal efficiencies in this study could be above 95% under proper operation conditions. The absorption capacity of NH3 was around 0.9 kg of CO2 per kg of NH3 reagent being used. This should be higher than that by MEA solution. The reaction products were analyzed and determined by X-ray diffraction analysis, SEM picture and pH measurements. All the measurements indicated that ammonium bicarbonate solution and its crystalline solids may be the major product of reaction. A conceptual design of the CO2 removal by NH3 scrubbing process was also presented. Key parameters that will determine the feasibility of CO2 scrubbing from flue gas by NH3 solution was indicated.