VPSA process characterization for ISO quality green hydrogen generation using two practical multi-component biomass gasification feeds

Abstract

The current work reports on the performance characterization of a VPSA system developed in-house for ISO-quality green hydrogen generation using commercially available zeolite 13X from two practical multi-specie feed streams generated from near-ambient oxy-steam and air gasification of casuarina wood chips. The breakthrough dynamics in a packed column, and the effect of extrinsic and intrinsic decision variables on the separation performance under a cyclic steady state are analyzed. Adsorption pressure and feed flow rate are noted as the most significant influencing factors. The assessment indicates the prevalence of bed thermal gradients and establishes N2 as a limiting gas impurity and CO2 desorption as a rate-determining step. Additionally, Pareto curves signifying the process capability to produce hydrogen of different grades are generated. The average recovery range achieved using syngas feed for obtaining purity >98 mol% (ISO grade A and above) at the lab-scale is noted to be 40.7–74.4%, which is analogous to published literature for fossil streams. Adopting the optimal parameters from the prototype studies and a precise gas contaminant analysis, the technology is practically demonstrated at the pilot scale (feed: 100 Nm3/h) for the continuous generation of fuel cell compliant hydrogen (fuel index ≥ 99.97) and a successful operation at an average recovery of 68.4 ± 3.5% is realized.