Production of high-purity carbon dioxide and sodium bicarbonate by lime cellar gas cleaning and chemical recycling: Process simulation and techno-economic analysis

The cement industry is responsible for 8% of total global CO2 emissions, which mainly originate from limestone calcination and fuel combustion. In view of the application potential of using CO2 to produce chemicals, this paper developed a novel process based on the Aspen Plus process simulation for the co-production of 99.99% CO2 by means of Methyldiethanolamine (MDEA) absorption/desorption and NaHCO3 by carbonization of CO2, NH3 and Na2SO4. The effects of absorption temperature, NH3 and Na2SO4 feeding amount, crystallizer temperature and pressure on CO2 capture rate and utilization rate were explored. The results showed that the best CO2 capture rate was achieved when the cellar gas inlet temperature of the absorber tower was 37 degrees C; Saturated Na2SO4 solution was favorable for CO2 absorption, and the CO2 utilization rate increased with the increase of Na2SO4 dosage; NaHCO3 yield decreased with the increase of crystallizing temperature, and the best NaHCO3 yield was achieved when the crystallizer temperature was 35.5 degrees C; Crystallizing pressure had little impact on the reaction. Economic analysis showed that the project will start to be profitable in 6.48 years with a Net Return Rate (NRR) value of 13.51%. It indicates that the project has economic benefits and provides a new way to reduce CO2 emissions from lime cellar gas.