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.