A new aqueous mineral carbonation process utilizing bipolar membrane electrodialysis

A new aqueous mineral carbonation process which utilizes bipolar membrane electrodialysis was proposed. The proposed process consists of four unit operations, (a) acid leaching of alkaline metals (Ca²⁺ /Mg ²⁺) from mineral compounds by HNO₃, (b) Na ₂CO₃ generation via absorption of CO₂ into NaOH, (c) Ca and Mg carbonate precipitation by addition of Na₂CO ₃, and (d) HNO₃/NaOH regeneration from NaNO₃ solution with bipolar membrane electrodialysis. Regenerated HNO₃ solution is then recycled to the acid leaching step. In the Na ₂CO₃ generation step, regenerated NaOH solution is contacted with the gaseous CO₂ to form Na₂CO₃ solution. Exhaust gas from power plant can be directly used without compression. Experimental studies were conducted to confirm the technical feasibility of this process. Results demonstrate that HNO₃ and NaOH were successfully regenerated from NaNO₃ solution by using bipolar membrane electrodialysis. This result suggests that we can utilize alkaline metals in mineral compounds by using acid and HNO₃ and NaOH solution can be used cyclically in this process.