Thermodynamic research of adsorbent materials on energy efficiency of vacuum-pressure swing adsorption cycle for CO2 capture

摘要

This paper presents a comprehensive thermodynamic research on energy efficiency of vacuum-pressure swing adsorption (VPSA). The study examined the influence from four types of typical adsorbent materials on the energy efficiency of VPSA by cycle parameters. The selected adsorbent materials are activated carbons, zeolite 5A, zeolite 13X, silica gels, and metal-organic frameworks (MOFs). The study also analyzes the effects of separation temperature, adsorption pressure, desorption pressure, CO2 concentration and percent of unused bed on the energy-efficiency of VPSA cycle. The examined performance parameters are CO2 working capacity, proportionality factor, energy consumption and second-law efficiency. The results show that the energy consumption is approximately 2.0-4.5 MJ/kg and the second-law efficiencies are 4-7% for VPSA cycles using the five adsorbent materials. The effect of adsorbent materials on the energy efficiency mainly depends on the proportionality factor of CO2 working capacity (beta) of VPSA cycle, which is important to screen materials at the fixed cyclic boundary conditions and preliminary calculation of second-law efficiency for VPSA cycles. For existing adsorbent materials which are Type I commonly, the lower values of beta would lead to the higher second-law efficiencies. The development of new adsorbents of Type III would be extremely urgent in near future. (C) 2017 Elsevier Ltd. All rights reserved.