Green Hydrogen Recovery from Natural Gas Grids by Adsorption Processes

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

Publication . Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Henrique, Adriano; Rodrigues, Alírio; Silva, José A.C.

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 H2 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 H2 blended in NGG with a synergy action of two types of adsorbents: a Carbon Molecular Sieve 3K-172 (CMS) in stage 1 and zeolite 13X in stage 2. In Stage 1, the CMS kinetically separates H2 from CH4, pre-concentrating H2 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 H2 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 H2 product with a purity of 99.97 % (fuel cell grade), a recovery of 67 %, and productivity of 1.60x10-2 kgH2/kgads/hr, and a total specific energy consumption of 10.06 MJ/kgH2, which is a significant achievement reported so far.

2025Journal article

Open access

Kinetic separation of green hydrogen from natural gas grids by using vacuum pressure swing adsorption

Publication . Zafanelli, Lucas F.A.S.; Henrique, Adriano; Aly, Ezzeldin; Rodrigues, Alírio; Mouchaham, Georges; Silva, José A.C.

Transitioning to renewable energy sources is crucial to mitigating climate change. In this scenario, green hydrogen (GH) is considered a promising energy carrier due to its high calorific value, versatility in applications, clean combustion, and potential for local generation in abundance. As interest in GH grows, developing its distribution chain becomes crucial in facilitating its widespread use. The co-transporting GH into existing natural gas grids (NGG) emerges as a viable alternative, eliminating the need for significant infrastructure investments. However, upon blending GH into the NGG, it becomes essential to de-blend and purify it to a high degree to enable, for instance, fuel cell applications (H2 > 99,97%). One problem concerning the separation and purification of GH from NGG relates to the H2 feed concentration (< 20%), which differs significantly from conventional H2 purification processes (> 70%). Moreover, the high CH4 concentration and its relatively weak adsorption affinity on commonly used adsorbents further complicate achieving high-purity H2 and high recovery rates through conventional approaches. In this work, we report a novel conceptual vacuum pressure swing adsorption (VPSA) process to separate H2 from CH4 by exploiting the kinetic selectivity of H2 over CH4 on CMS-3K-172.

2024Conference object

Open access