Dual-stage vacuum pressure swing adsorption for green hydrogen recovery from natural gas grids

• Dual-stage (DS) VPSA was developed to purify low H 2 concentrations in the pipelines. • Sinergy action between CMS-3K and zeolite 13X allows high H 2 purity and recovery. • A parametric study was conducted to optimize fundamental process variables. • The DS-VPSA enriches H 2 from 20 to 99.97 % with a high recovery of 67 % • The energy consumption to produce 384 kg H2 /ton ads /day is 10.05 MJ/kg H2. Purification of green hydrogen (GH) from natural gas grids (NGG) can be expensive and challenging through a single-step Pressure Swing Adsorption (PSA) process due to the low H 2 concentration in the grid (<20 % v/v). Herein, we report for the first time the design of a dual-stage vacuum pressure swing adsorption process (DS-VPSA) to purify H 2 blended in NGG with a synergy action of two types of adsorbents: a Carbon Molecular Sieve 3K (CMS) in stage 1 and zeolite 13X in stage 2. In Stage 1, the CMS kinetically separates H 2 from CH 4 , pre-concentrating H 2 from 20 % to over 50–60 % (v/v), followed by Stage 2, where a thermodynamic separation with zeolite 13X achieves a final product with a high H 2 purity content (>99 % v/v). A mathematical model is developed in Aspen adsorption, where numerical simulations are performed to establish the best operating conditions of the global DS-VPSA. A parametric study is also conducted to optimize performance parameters such as recovery, purity, productivity, and specific energy. The results indicate that it is possible to achieve a final H 2 product with a purity of 99.97 % (fuel cell grade), a recovery of 67 %, and productivity of 1.60x10 -2 kg H2 /kg ads /hr, and a total specific energy consumption of 10.06 MJ/kg H2 , which is a significant achievement reported so far.