Synthesis of dry sorbents for carbon dioxide capture using coal fly ash and its performance

The present paper investigates the application of raw coal fly ash (FA) to dry-based CO2 fixation. Dry sorbents are manufactured by mixing FA, NaOH, CaO and a small amount of water and their absorption behavior, performance, regeneration and leaching efficiency are analyzed. The CO2 absorption efficiency (AE) of FA-added sorbent (WNCF) is higher than that of FA-free sorbents (WNC) and its absorption behavior is improved. In addition, CO2 desorption from carbonated WNCF (CWNCF) occurs at 100 °C lower than that from carbonated WNC (CWNC) and its desorption efficiency is 16.5% point higher than that of CWNC, due to the FA addition to the sorbent. However, the AE of regenerated CWNCF is substantially lower than that of fresh WNCF, which indicates that CWNCF cannot easily be regenerated by simple desorption increasing temperature. This is ascribed to the effect of the added FA and water in contributing to the production of Ca- and Na-based carbonated materials that cannot readily be regenerated during the carbonation. Some of the inherent K and Ca components present in the raw FA participate in the carbonation of WNCF, and Cr is co-precipitated during WNCF carbonation to become a stabilized material.