Accelerated Carbonation of Cement Kiln Dust and Lime Kiln Dust for Permanent Storage of CO2

According to the International Energy Agency, cement production contributes to 7% of the global CO₂ emissions. A significant reduction in the carbon footprint of the cement industry is expected to reduce the detrimental impacts on the carbon cycle. One of the ways to reduce CO₂ emissions from the cement industry is to react the produced CO₂ with alkaline wastes produced during the manufacturing of cement such as cement kiln dust (CKD) and lime kiln dust (LKD). CKD and LKD are fine-grained, unreacted wastes obtained from the calcination of finely ground limestone fed into cement kilns. Therefore, these materials have a high content of CaO which can react with CO₂ to form carbonates. In order to accelerate the dissolution of CKD and LKD to allow for faster conversion to carbonates, weak organic chelating agents such as 0.1 M Na-acetate and 0.1 M Na-gluconate are tested. Direct carbonation experiments are then performed with the optimal chelating agents at varying reaction temperatures (Tmax = 90 ^oC) in the presence of the best chelating agent and 0.64 M NaHCO₃ which acts as a pH buffer and carbon carrier, and at P_CO2 = 150 atm. The extents of carbonation and formation of different phases are determined using Thermogravimetric Analysis (TGA), Total Carbon Analysis (TCA), Total Inorganic Carbon Analysis, and X-Ray Diffraction (XRD). Morphological alterations in CKD and LKD were identified using BET pore volume distributions, particle size analyses, and Scanning Electron Microscopy (SEM).