Clean production of porous MgO by thermal decomposition of Mg(OH)2 using fluidized bed: Optimization for CO2 adsorption

Abstract

Fluidized bed efficiently intensifies thermal decomposition of Mg(OH)2 for fast preparation of porous MgO. The shrinking core model is found to well describe the decomposition process. The initial stage of decomposition is controlled by chemical reaction with activation energy being 104kJ/mol and the subsequent stage is then controlled by diffusion with activation energy being 15kJ/mol. The response surface methodology (RSM) and the central composite design (CCD) are employed for determining optimal conditions to prepare adsorbent with maximum CO2 removal capacity. The operational parameters such as dehydration temperature (°C), duration (min) and FR-flow rate (Nm3/h) are chosen as independent variables in CCD. The statistical analysis indicates that the effects of dehydration temperature and combined effect of temperature and duration are all significant to the CO2 removal capacity. The optimal condition for achieving the maximum CO2 adsorption capacity is obtained as the following: temperature (480 °C), duration (42min), FR (13.8Nm3/h) with CO2 removal capacity reaching 33mg/g. The employment of fluidized bed in process intensification significantly reduces the thermal treatment duration down to 0.7h.