Role of MgxCa1−xCO3 on the physical–chemical properties and cyclic CO2 capture performance of dolomite by two-step calcination

Abstract

Two-step calcination (CO2 and N2 atmospheres) was used to modify the microstructure of natural dolomite for high-temperature CO2 capture. Two other one-step calcinations (CO2 or N2 atmosphere) were provided for comparison. Different morphological characterizations (thermal decomposition, phase composition, morphology, and nitrogen adsorption) were performed, followed by an analysis of 30 carbonation/calcination cycles in a fixed bed reactor. During primary calcination in a CO2 atmosphere, an intermediate phase (MgxCa1−xCO3) was observed by TG and XRD results, which hindered the de-mixing of CaO and MgO in the secondary calcination in a N2 atmosphere. Therefore, two-step calcination produced smaller grains (CaO: 45.2nm; MgO: 32.6nm), larger specific surface area (21.08m2/g) and pore volume (0.082cm3/g) and uniform distribution of CaO and MgO, which resulted in a higher and more stable uptake of CO2 compared to the results from one-step calcinations.