Model-based evaluation of piston reactor to produce hydrogen from methane via gas-phase SMR and ATR routes

The implementation of electrified and compact reformers is a promising direction to intensify hydrogen production from natural gas and biomethane feedstocks and reduce carbon emission footprints. Piston reactor technology has the potential to reach this by utilizing the reactor unique high temperature and pressure operating window, mode of operation involving rapid adiabatic compression-expansion cycles and co-generation of electrical and mechanical power attractive for integration with other processing units to make efficient process design. This work aims to assess the piston reactor for hydrogen production process on its volumetric productivity, operating window, energy efficiency, CO₂ emission, and initial economics. It will also theoretically evaluate whether gas-phase steam methane reforming (SMR) and autothermal reforming (ATR) are viable in this reactor technology. A piston reactor model is established using a zero-dimensional thermodynamic single-zone piston model coupled with an available gas-phase mechanistic model. The highly endothermic SMR reaction is not feasible under a wide range of conditions, leading to its elimination from further assessments and studies. ATR is an attractive route for hydrogen production. Compared to the simulated industrial catalytic ATR reformer at conventional conditions, the piston reactor reaches a similar methane conversion between 89 % and 97 % while operating in the gas phase without using any catalyst with an intake temperature lower by 300 K relative to the conventional case. An ATR process design is established showing attractive economics even at a small production capacity of 25 tons/day of hydrogen, and comparable CO₂ emissions as that of a large-scale industrial ATR process.