Investigation of CO2 Sequestration Possibility via Indirect Mineral Carbonation using Waste Coal Fly Ash

摘要

Mineral carbonation is recognized as a significant method for CO2 sequestration using waste coal fly ash. Naturally available free lime in coal fly ash can be extracted to an aqueous solution before reaction with CO2, which could produce precipitated calcium carbonate (PCC), i.e., indirect mineral carbonation. In this study, fly ash samples were collected from Lakvijaya Coal Power Plant (LCPP) in Sri Lanka and tested for their chemical/physical properties and the possibility of calcium extraction. The average calcium oxide (CaO) content in LCPP fly ash was 5.81 wt%. Laboratory experiments were performed to determine the possibility for indirect carbonation, varying the residence time, quality of mixing, solid-liquid ratio, and salinity of water. Under the specific conditions, the maximum calcium extraction efficiency of 9.65% was obtained within 45 minutes, which stayed constant against time, thereafter. Effect of improved mixing using baffles was minor, where similar variations were observed for both baffled and non-baffled configurations against mixing time. Increased salinity significantly improved the calcium extraction efficiency by 71.1% when the salinity got increased from 0 g/L to 50g/L, which highlights the potential of sea water as an effective solvent for indirect mineral carbonation process using coal fly ash for CO2 sequestration.