Multi-bed vacuum pressure swing adsorption for carbon dioxide capture from flue gas

A detailed framework for simulation of VPSA units is presented. Within this framework, a detailed description of the adsorbent column is provided and linked with other ancillary parts of the unit. This modeling strategy is particularly suitable to demonstrate how the entire unit works and to identify operating constraints that may be caused by ancillary equipment. In order to apply this strategy to a practical example, we have simulated different cycles of VPSA processes using zeolite 5A for CO2 capture from a mixture with 15% CO2-85% N2 (resembling post-combustion flue gases of a coal-fired power station). Simulations of VPSA units with two, three and four columns and different cycle configurations were carried out. Inclusion of a rinse step was necessary to improve CO2 purity. However, using a single VPSA unit, it was not possible to achieve purity higher than 77% and for this reason a two-stage VPSA unit was simulated. The two-stage VPSA simulations include a three-column front VPSA process where CO2 purity is increased to 70% and then this gas is recompressed to a second, tail two-column VPSA unit where CO2 purity increases to 96%. The overall unit productivity of this process is 0.0146 kgCO2/(kgads h) with an energy consumption of 645.7 kJ/kgCO2. © 2011 Elsevier B.V. All rights reserved.