A pilot scale study on co-capture of SO2 and NOx in O2/CO2 recycled coal combustion and techno-economic evaluation

Abstract: This paper presents the study on co-capture of SO₂ and NO _x in O₂/CO₂ recycled coal combustion in a pilot scale facility with the heat input of 0.3 MW by using high-sulphur lean coal. Detailed comparison of SO₂ and NO _x emission indexes and desulphurization and denitration rates have been made among three working conditions of O₂/CO₂, O₂/CO₂ with limestone injection (O₂/CO₂+Ca) and O₂/RFG (recycled flue gas) with limestone injection (O₂/RFG+Ca). Combustion in air was performed as a base case. Results showed that in the O₂/RFG with limestone injection, desulphurization and denitration rates could reach up to 96% and 89%, respectively. Limestone injection under the high-CO₂ atmosphere caused a significant reduction on SO₂ emission and NO _x emission as well. This indicated O₂/CO₂ recycled coal combustion could reduce the investment on the flue gas purification. The techno-economic evaluation indicated that Oxy-combustion technique is not only feasible for CO₂ emission control based on existing power plants but is also cost-effective.