Carbon-Negative Production of Soda Ash: Process Development and Feasibility Evaluation

Aiming to produce carbon-negative soda ash, chlor-alkali electrolysis, CO₂ direct air capture, and sodium carbonate crystallization are combined in a so-called CODA process. In this study, four variants of the CODA process are developed and evaluated by means of modeling and simulation. Variations of the process design are related with the CO₂ absorption technology, the crystallization strategy, and the possible byproducts of the process. The processes using a cross-flow packed absorber had a smaller CAPEX (between 195 and 209 USD/ton soda) than the process using a droplet absorber (337 USD/ton soda). When coupled with the cross-flow packed absorber, the two-step crystallization strategy had a smaller OPEX (150 USD/ton soda) than the one-step crystallization (175 USD/ton soda). The revenue of selling the process byproducts such as hydrogen, chlorine, and CO₂ certificates was key to the profitability of the CODA process. The most promising CODA variant (cross-flow packed absorber and two-step crystallization) consumes about 0.15 tons of CO₂ from the air and earned nearly 200 USD/ton soda ash, making CODA an attractive alternative that deserves to be scaled-up.