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.