Stability and Carbon Capture Enhancement by Coal-Fly-Ash-Doped Sorbents at a High Temperature

Carbon capture using various technical options, viz., adsorption, absorption, chemical looping combustion, membrane separation, and cryogenic separation in either pre- or post=combustion modes, has been found to be the effective solution to tackle a serious concern of global warming. Although adsorption has been widely employed in carbon capture as a result of its economically, and environmentally benign nature, it could not he commercialized as a result of the highly energy intensive regeneration process involved. The major challenge in carbon capture is its sustainability at a high temperature, therefore enabling an easy integration with power generation to make it commercially viable, and also in the production of hydrogen using sorption-enhanced steam reforming. In this work, various combinations of sorbents based on CaO, MgO, zeolites H-Beta and H-ZSM 5, and Al2O3 with and without doping of coal fly ash (C and F types) have been employed in carbon capture using a lab-scale fixed-bed reactor system. After initial screening of numerous sorbents, those based on CaO, MgO and fly ash have been selected, for rigorous standardization with reference to various critical process parameters, such as the sorbent combination, sorbent quantity, temperature, carbonation time, gas composition, and flow rate. It has been found that 50%, CaO, 10% MgO, and 40% fly ash gave the highest capture besides exhibiting cyclic stability up to 15 cycles, and a positive influence of coal fry ash in stability and carbon capture enhancement has been reinforced.