Dynamic behaviour of integrated chemical looping process with pressure swing adsorption in small scale on-site H2 and pure CO2 production

Abstract

The design of a fully integrated chemical looping reforming (CLR), single adiabatic water gas shift reactor (WGSR) and pressure swing adsorption (PSA) operated under dynamic conditions for small scale H2 generation with inherent pure CO2 production is carried out. The dynamically operated packed bed reactors taking part in the chemical looping process have been modelled, designed and simulated to operate with transient feeds from an integrated PSA unit used for the production of 130 Nm3/h of pure H2 (99.9999% purity). As by-product, 51 Nm3/h of pure CO2 (>98.8% purity) is also produced. A rapid cycle 8-bed configuration increases the H2 recovery by 4% whilst reducing the tail gas buffer tank volume requirement by 44%. The effect of the PSA dynamic tail gas composition used as fuel for the CLR reduction reactor stage was found negligible regarding the continuity of the process and the performance of the plant, as it affected only the reduction outlet gas composition profile but had little effect on the reactor bed temperature profile. With respect to the design of the chemical looping reactor beds, an analysis has been performed on the effect of heat losses showing that at higher heat transfer coefficient ( U = 5.0 W∙m-2∙K-1) CH4 conversion decreased significantly (≈90% compared to adiabatic operation), therefore a different strategy was implemented. The overall study demonstrates the process design feasibility for producing blue H2 or renewable H2 from methane/bio-methane in decentralised and modular units.

Keywords: chemical looping, CO2 capture, PSA, dynamic modelling, H2 production