Direct mineral carbonation of coal fly ash for CO2 sequestration

Developing countries face the projected scenario of increased CO2 emissions in the coming years as their major dependence for power generation relies on the coal reserves. Mineral carbon sequestration using industrial alkaline solid residues is a promising technology for carbon capture and storage. In this laboratory work, direct mineral carbonation of coal fly ash (CFA) through gas solid as well as aqueous route has been studied with 100% CO2 gas in a stainless steel reactor at low pressure (<10 bar) and room temperature. The dry route demonstrated to be a slow process, wherein the maximum sequestration capacity was found to be 26.3 g of CO2/kg of CFA at 10 bar for 1 h. In the case of wet carbonation, the maximum capacity achieved was 50.3 g of CO2/kg of waste with the CFA water slurry of 15 as L/S ratio, stirred at 900 rpm at 4 bar for 2 h. The carbonation process was evidenced by the characterization of the carbonated CFA using FT-IR, XRD, SEM and TGA. The results show that CFA can be utilized for carbon capture through the simple, direct carbonation approach and the process parameters play vital role in effective sequestration. (C) 2015 Elsevier Ltd. All rights reserved.