Experimental and modeling investigation on post-combustion carbon dioxide capture using zeolite 13X-APG by hybrid VTSA process

Zeolite 13X-APG with Si/Al ratio of 1.23 supplied by UOP (China) was evaluated for capturing the low concentration CO2 from flue gas. The adsorption equilibrium isotherms of CO2 and N-2 on this adsorbent were measured at various temperatures (303, 333, 363, 393)K with 0-1 bar range of pressure and the experimental data were fitted by the multi-site Langmuir model. Compared with the conventional NaX zeolite, 13X-APG zeolite has an excellent adsorption capacity to CO2, especially at low CO2 partial pressure. The adsorbent is more selective to CO2 in the flue gas. The breakthrough experiments of CO2 and N-2 in the column packed with zeolite 13X-APG pellets have been studied. A mathematical model based on the bi-LDF approximation for mass transfer, taking into account the energy and momentum balances, have been employed in the simulation of breakthrough curves in order to obtain the adsorption kinetic parameters of CO2 and N-2, respectively. The experimental and theoretical results of a six-step hybrid VTSA process, as well as four-step VSA and five-step TSA process were presented for CO2 capture at ambient temperature and ambient pressure from the simulated flue gas (85% N-2 and 15% CO2), and the feasibility and efficiency of VTSA process were analyzed. The regeneration conditions of VTSA process became more gentle when compared with the cases in both VSA and TSA processes, and it would be a saving power-energy consumption process for post-combustion CO2 capture if it was retrofitted to the existed power plants with the utilization of the lower grade heating/cooling source. (C) 2012 Elsevier B.V. All rights reserved.