Design, simulation, and feasibility study of a combined $CO_2$ mineralization and brackish water desalination process

Abstract

This study presents novel process integration between $CO_2$ mineralization and brackish water reverse osmosis (BWRO). The integration is based on a complementary relationship between these two processes. While $CO_2$ mineralization needs metal ions such as $Na^+$ to convert $CO_2$ into mineral carbonate like sodium bicarbonate, BWRO should reject these ions to produce fresh water. Thus, there is a possible synergy if these two processes are integrated appropriately. To verify this potential advantage of process integration, techno-economic analysis (TEA) and $CO_2$ life cycle assessment (LCA) are implemented. A first key requirement for TEA and $CO_2$ LCA is mass and energy balance data. Therefore, the process is simulated with commercial software tools such as Aspen plus and Matlab. A second key requirement is proper evaluation scenarios. Based on market analysis, the proposed process is assumed to be installed in the US and China to replace conventional benchmark process. Also, two electricity sources (coal and wind onshore) are considered in the evaluation to investigate the sensitivity of the process performance upon electricity type. As the result of TEA and $CO_2$ LCA, $CO_2$ avoidance cost of the process is currently 132~245$/metric ton of $CO_2$ with wind-based electricity. It is higher than $CO_2$ avoidance cost of relatively mature carbon capture and storage (CCS) process (60~170$/metric ton of $CO_2$), which implies a slightly inferior performance of the suggested $CO_2$ utilization process. Nevertheless, one thing to note is that the proposed $CO_2$ utilization process has advantages compared to the CCS process in terms of no need for storage site, no danger of $CO_2$ leakage, production of useful materials, etc. In addition, since the feasibility study was carried out for the baseline case, process performance can be improved further through optimization. Therefore, the presented process integration between $CO_2$ mineralization and BWRO has enough potential to be further investigated as a means to produce useful chemicals and fresh water as well as to reduce $CO_2$ emission.