Fixed-bed adsorption of carbon dioxide-nitrogen mixtures onto activated carbon: Characteristics of CO2 adsorption and modeling

The atmospheric content of the most abundant greenhouse gas, CO 2, has risen from preindustrial levels of 280 parts per million (ppm) to present levels of over 365 ppm. The main sources of CO2 emissions are the combustion of fossil fuels, such as coal, natural gas and petroleum, and industrial processes, such as oil refinement and the production of cement, iron and steel. The reduction of carbon dioxide emissions from flue gases can be achieved using post-combustion technologies such as adsorption. Different adsorbents, such as activated carbon, zeolites, MCM-41, mesoporous silica material SBA-15 and several enriched-amine sorbents, have been tested. Good recovery and product purity have been accomplished with very high energy consumption. An ideal sorbent should offer high adsorption and selectivity for carbon dioxide as well as economically feasible regeneration. However, if the affinity of the adsorbent for carbon dioxide is too high, the regeneration step can negatively affect the cost of the process. In this paper, we report an experimental and theoretical study on the separation of carbon dioxide and nitrogen on activated carbon in a fixed bed. The breakthrough curves were obtained at different temperatures using CO2/N2 mixtures. A model based on the Linear Driving Force (LDF) approximation for the mass transfer was used, taking into account the energy and momentum balances, to satisfactorily reproduce the breakthrough curves.