全球变化知识资源中心

Carbon dioxide capture and utilization has been considered as one of the solutions to the current climate change challenge. Swing adsorption processes can be used to capture carbon dioxide from industrial gases. Developing a selective high-performance adsorbent is key in this process. Cost-effective bio-based adsorbents, such as biochar, have shown a promising performance in recent decades and have been extensively studied. In this work, dynamic modeling and mass transfer study of carbon dioxide capture using biochar and MgO-impregnated activated carbon adsorbents were performed to provide insights on the adsorption mechanisms and improve the process. The results suggested that CO2 adsorption was physisorption and diffusion in the micropore was the controlling step. However, MgO impregnation enhanced the crystalline structure of the sample and increased the diffusion flux in macropores, which resulted in a higher adsorption capacity. The effects of various biochar activation methods and MgO impregnation techniques on the macro- and micropore mass transfer coefficients were reported as well. ASPEN Adsim was used to simulate temperature swing adsorption (TSA) and vacuum swing adsorption (VSA) processes to investigate their feasibility based on the experimental data obtained. The TSA process was not feasible as a result of high heating and cooling duties and the long time required for these cycle steps; however, the VSA process worked well, and product purity and recovery of 99.9 mol % and 90% were achieved, respectively. The VSA process operates at room temperature and atmospheric pressure and has potential for industrial application, especially in biofuel plants, where biochar is already available as a waste material.