Hydrogen production with near-zero carbon emission through thermochemical conversion of H2-rich industrial byproduct gas

Abstract

Low-emission hydrogen production plays a key role in the transition of the presently fossil fuel-dominant energy system and sustainable development of fossil energy. A wide collection of industrial byproduct gases is hydrogen-rich and is currently an important source of blue hydrogen, however, accompanied by significant carbon footprint. In this study, we propose a novel method of multi-product sequential separation steam reforming of industrial byproduct gases for low-emission H₂ production with near-complete H₂ recovery and CO₂ capture. We first focus on a typical example of coke oven gas (COG) in this category of gases, and demonstrate experimentally the superiority of our new method over conventional physical hydrogen separation methods (e.g., pressure swing adsorption, PSA) and conventional reforming-based thermochemical methods. We devise two strategies of COG conversion and comparatively investigate the effects of reaction temperature, H₂ content and steam-to-methane ratio on key performances including COG conversion, hydrogen production and CO₂ capture. At a reforming temperature of 425 °C, the conversion rates of CH₄ and CO in the gas mixture reach 99 %, and H₂ production rate reaches 1.79 mol-H₂/mol-feed correspondingly. The first-law energy efficiency of hydrogen production from COG reached 70.5 %, which is 6.5 percentage points higher than that of conventional COG reforming methods. The developed methodology also enables efficient decarbonization and hydrogen recovery from various industrial by-products (oil refinery, etc.) with high fractions of H₂ and alkane, achieving over 99 % alkane conversion, CO₂ selectivity, and near-complete H₂ recovery. The CO₂ reduction reaches 0.778 kg-CO₂/m³-COG (>99 % of theoretical maximum), essentially achieving complete decarbonization of the gas mixture. The mild reaction conditions enable possibilities for this method to be flexibly combined with industrial waste heat or renewable energy sources. The results indicate that the proposed method has significant advantages and potential for achieving sustainable conversion of industrial byproducts gases and CO₂ emission reduction.