Researchers from the University of Edinburgh and Yonsei University have developed a low-carbon process to improve the production yield of ultrapure hydrogen from coal-like materials.

The advance could benefit a broad range of chemical engineering and industrial applications in which significant demand exists for the gas, including low-carbon, hydrogen-based heat and power production for industrial plants or next-generation hydrogen fuel cells for hybrid and electric vehicles.

Until now, the primary form of hydrogen production has been via natural gas (methane) steam reforming. During this process, hydrocarbons in the gas are converted at high temperature into a hydrogen-rich mixture of gases. The hydrogen is then separated during an additional processing step.

The advance could benefit next-generation hydrogen fuel cells for hybrid and electric vehicles.While researchers have tried to produce high-purity hydrogen from less expensive raw materials such as coal and biomass, solid-to-H2 processes have not proven to be economically feasible due to an intrinsically low hydrogen yield.

Through a series of adopted processes, researchers led by Dr. Hyungwoong Ahn, senior lecturer in chemical engineering at the University of Edinburgh, have found a method to produce low-carbon hydrogen from coal that improves on this ultra-pure hydrogen yield.

By integrating a coal‐to‐hydrogen process with carbon capture, the hydrogen yield per unit coal feed can be greatly improved using the carbon-capture unit used on a synthesis gas stream generated by coal gasification, says Ahn. He says this helps to improve the hydrogen yield by greater and more efficient use of the H2 pressure swing absorption (PSA) tail gas—an important separation process for gases and applied widely in gas purification and gas recovery.

The research team says the core invention was to split the PSA tail gas into three sub-streams and use them as a supplementary fuel for a carbon gas capture unit to improve its sorbent regeneration; as an additional feed to shift reactors to boost the hydrogen yield by converting more carbon to hydrogen; and as fuel from drying coal instead of using synthesis gas.

“The production of high-purity hydrogen and the efficiency of the process, from start to finish, will amount to an improvement in hydrogen production yield by more than 2% further to what would be expected of a solid-to-H2 process, with CO2 capture and a total auxiliary power consumption reduction by around 7%," says John Jeffrey, business development executive of Edinburgh Research & Innovation (ERI), the university’s commercialization arm. "These can be viewed as significant savings depending on the output of the processing plant.”

ERI is seeking industrial partners to license the technology for development into a commercially viable application.