Concomitant removal of NOx and SOx from a pressurized oxy-fuel combustion process using a direct contact column

Journal article, 2018

The simultaneous removal of NO x and SO x using a direct contact column has potential for efficient treatment of the flue gases arising from pressurized oxy-fuel combustion. This study focuses on a parametric analysis of the efficiency of NO x and SO x removal from the flue gas of an oxy-fuel combustion process using an Aspen Plus direct contact column model. The chemistry implemented in this model reflects the state-of-the-art NO x and SO x reaction mechanisms, with particular emphasis on the liquid-phase chemistry, including pH-dependency. The effects of pressure, water flow rate, and recycle ratio on the removal efficiencies of NO x and SO x were evaluated. The evaluation was conducted based on the base case pressurized (15 bar) flue gas with a feed rate of 120 kg/s and inlet temperature of 40 °C before it was supplied to the column. NO x removal efficiency increased from 70% to 97% when the pressure increased from 15 bar to 30 bar, whereas 99.9% of the SO 2 was absorbed from the flue gas at 15 bar. We show that the removal efficiency is pH-sensitive and it is directly influenced by the recycle ratio and liquid-to-gas ratio (L/G). As the L/G ratio was increased, the removal efficiency of SO x and NO x increased. On the other hand, when the recycle ratio of bottom liquid was increased, the removal efficiency of SO x and NO x decreased.