An advanced, ammonia-based combined NOx/SOx/CO2 emission control process towards a low-cost, clean coal technology

Abstract

Traditional method of removing gas pollutants from a coal-fired power station involves a series of separate processes, which include selective catalytic reduction for NOx treatment, flue gas desulfurisation for SOx removal, and post-combustion CO2 capture. Each of these individual processes involves significant capital investment. To reduce costs, we propose an alternative approach to simultaneously remove these three pollutants by incorporating NOx/SOx treatment into an aqueous NH3-based CO2 capture process. In our advanced process design, NOx/SOx pollutants are effectively scrubbed by sodium chlorite (NaClO2) oxidizing reagent, with the resultant acidic solution efficiently reducing NH3 emissions from CO2 absorber to <1 ppmv. An advanced, NH3-based flash stripper is used to achieve high capture energy performance, and flue gas heat integration is employed to further reduce the regeneration energy to 2.17 GJ/tonne CO2. Techno-economic evaluation revealed that our NH3-based combined NOx/SOx/CO2 removal process has great advantages in capital and energy saving, resulting in a CO2-avoided cost of $46.2/tonne, which is significantly lower than the cost of the conventional, monoethanolamine-based process ($79.1/tonne CO2) and the base NH3 process ($56.2/tonne CO2). This simultaneous NOx/SOx/CO2 capture technology provides an alternative approach to advancing multi-pollutant emission control and CO2-capture technology, leading to the development of a cost-effective clean coal technology.