Carbon dioxide recovery by vacuum swing adsorption

Abstract

According to an investigation by the Intergovernmental Panel on Climate Change (IPCC), carbon dioxide is the most significant greenhouse gas produced as a result of human activities. The amount of carbon dioxide emissions has to be reduced to meet global treaty. The concentration and recovery of carbon dioxide from flue gases is the first important step in solving the carbon dioxide problem. Therefore in this study, we employed simple vacuum swing adsorption (VSA) processes with zeolite 13X to remove carbon dioxide from flue gases and concentrate it in the desorption stream. We have been convinced of the feasibility of the VSA simulation program by a comparison of the experimental and simulation results. Both dual-bed and three-bed processes have been explored by simulation. The feed gas contains 20% carbon dioxide and 80% nitrogen. Pressure drop in the adsorptive bed is not considered because of the large adsorbent particle size. Instantaneous equilibrium is assumed between the solid phase and gas phase, and non-isothermal operation is then considered. The numerical method utilized in this simulation is the method of lines with adaptive grid points. The estimation of the spatial derivatives is made from the upwind difference, and the cubic spline approximation is used to estimate the flow rates in the adsorptive bed. The carbon dioxide concentrating effect of the three-bed process is better than that of the dual-bed process, but carbon dioxide recovery in the dual-bed process is higher. For the three-bed process, 63% carbon dioxide can be attained under optimum operating conditions, and the carbon dioxide recovery is 67%.