Developing methane pyrolysis as a viable alternative for hydrogen production

Environmentally friendly hydrogen may one day replace fossil fuels as an energy carrier, a chemical feedstock, and a reducing agent. Today however, nearly all the world’s hydrogen supply is produced from fossil fuels, negating any environmental benefit. Meeting today’s increasing demand for hydrogen through renewable energy sources is not practical due to the associated high cost.

Okajima et al. investigated methane pyrolysis using molten media as a cost efficient and low CO₂-emisssion option for generating hydrogen. This reaction converts methane into solid carbon and hydrogen gas with no CO₂ byproducts.

“We studied this topic as a potential bridge to produce hydrogen until renewable energy-based technologies become feasible,” said author Ryota Okajima. “Methane pyrolysis technology using molten media attracted us because it can solve problems such as catalyst deactivation and reactor clogging caused by the rapid accumulation of produced solid carbon.”

To achieve efficient hydrogen production in molten media such as iron, aluminum, or salt mixtures, the team used a bubble column and focused on producing small bubbles, along with evaluating the effects of gas injection rate and material properties on bubble dynamics. Smaller bubbles have larger gas-liquid interfacial areas and more efficiently transport heat from the molten media to methane.

Computational fluid dynamics simulations indicated that gas injection rate and molten media properties have a substantial effect on the bubble diameter and flow regime. The identity of the gas was considerably less important than the identity of the molten media.

“We would like to focus our future research on understanding the behavior of produced solid carbon particles in molten media,” said Okajima.

Source: “Hydrodynamics of molten media bubble columns for hydrogen production through methane pyrolysis,” by Ryota Okajima, Travis R. Mitchell, Christopher R. Leonardi, and Simon Smart, Physics of Fluids (2024). This article can be accessed at https://doi.org/10.1063/5.0227299 .