A integrated route for CO2 capture in the steel industry and its conversion into CaCO3 using fundamentals of Solvay process

摘要

In this work we propose the transformation of CO2 into calcium carbonate utilizing steel slag and the waste heat generated in the steel industry. The necessary chemicals, aqueous NH4Cl and solid NaHCO3, were obtained as products of a bench scale Solvay process. Our approach is divided into four steps: (i) CO2 capture using ammoniated brine, (ii) Ca2+ lixiviation from steel slag, through the reaction with NH4Cl(aq), (iii) CaCO3 precipitation by reacting the leachate with NaHCO3, and (iv) NaCl and NH3 reclamation. Steel slag is utilized as the source of calcium. A small amount of heat is required by the overall process, which could be also provided by waste heat from the steel industry. Laboratory scale experiments showed that nearly 95 wt% of NaCl and NH3 necessary for the mineral carbonation can be regenerated, therefore minimizing costs. At the end of this process, 98 wt% pure CaCO3 is obtained, and up to 94 wt% of the extracted Ca2+ was precipitated with no need for pH adjustments. Finally, we observed that, depending on the source of the steel slag, 86 kg of high purity CaCO3 could be obtained from 38 kg of CO2 and 1000 kg of steel slag.