Novel wastewater recovery process for sustainable sodium carbonate production with CO2 and SOx utilization

Abstract

Ammonia-soda process, which produce soda ash, emits flue gas containing a large amount of CO₂ and SO_x. The wastewater discharged from the ammonia-soda process contains cations, such as Na⁺ and Ca²⁺, which can be recovered and reacted with a CO₂ and SO_x. In this study, we designed a CO₂ and SO_x utilization process for the sustainable production of sodium carbonate using wastewater recovery system, extracting Na⁺ and Ca²⁺. The proposed process involved the following steps: (1) metal-ion separation, which produces NaOH and Ca(OH)₂; (2) capture and utilization of SO_x using Ca(OH)₂; and (3) capture and utilization of CO₂ using NaOH and Ca(OH)₂, respectively. The economic feasibility of the proposed process was verified by comparing its total annualized cost (TAC) with those of conventional processes. Approximately 99% of SO_x was captured to produce high-purity desulfurized gypsum, and 99% of CO₂ was captured to be transformed into CaCO₃. To confirm the CO₂ reduction of the process, the carbon dioxide equivalent (CO₂e) was calculated by evaluating the amount of greenhouse gases. The CO₂e decreased to 71.4% compared with that of the conventional process. The TAC of the proposed process decreased by 10.67% and 19.63% compared with that of the ammonia-soda and Hou processes, respectively. Thus, this study proposes an industrially potential process design for sustainable sodium carbonate production by utilizing CO₂ and SO_x with wastewater recycling, without additional reactants, making it more economically viable.