Realizing CO2 emission reduction in lime and soda ash manufacturing through anion exchange†

Abstract

Lime (CaO) and soda ash (Na₂CO₃) are two foundational chemicals for modern civilization, and the CO₂ emissions from their production processes are challenging to reduce. Furthermore, decarbonization of the lime industry could also reduce the CO₂ emissions associated with cement production, for which lime is the key precursor. In this paper, we show that an anion exchange process to co-produce CaO and Na₂CO₃ from CaCO₃ and NaOH can reduce the carbon footprint of both chemicals through industrial symbiosis. Heating energy and NaOH production are the major contributing factors towards the cost and CO₂ emissions of this process, which can supply the global annual soda ash demand (∼65 Mt) and co-produce ∼50 Mt of lime in an economically sustainable manner (16% gross margin) while immediately reducing global CO₂ emission by 37 Mt compared to current production methods. Using electrified industrial heat sources and heat pumps to reuse heating energy would further reduce the cost and CO₂ emissions of the anion exchange process.