The Hydrogen Stream: Green hydrogen via ammonia decomposition

South Korean scientists have developed a highly selective palladium composite membrane on porous metal supports to cut the ammonia content of the permeated hydrogen stream. Dutch researchers, meanwhile, have presented two alternatives to this strategy – increasing the thickness of the membrane selective layer, or using a purification unit in the permeate of the membranes.

Korea Institute of Energy Research scientists have developed a pretreatment method for porous metal supports in a highly selective palladium (Pd) composite membrane for ammonia decomposition. The purity of hydrogen (H2) produced with membrane reactor tech is not always high enough to directly feed H2 to fuel cells, so strategies are needed to reduce the ammonia (NH3) content of the permeated hydrogen stream. The South Korean researchers applied alumina Sol, a stable colloidal solution made of boehmite, to an yttria-stabilized zirconia (YSZ) filled porous Inconel support. “A vacuum-assisted, two-step electroless plating of Pd drastically increased the hydrogen selectivity,” the researchers said in a recent paper in Energy. They applied a highly selective Pd composite membrane to a membrane reactor with a Ru/Al2O3 catalyst to produce high-purity hydrogen by ammonia decomposition. The Pd composite membrane reactor can selectively remove hydrogen, increasing the ammonia conversion rate and high-purity hydrogen production via a one-step reaction combined with purification. They said the membrane reactor was able to achieve a high ammonia conversion (99.6%) and a high hydrogen purity (99.99%), with a hydrogen production rate of 0.25 Nm3 h−1 at 745 K and a gauge pressure of 500 kPa.

Eindhoven University of Technology, meanwhile, have presented two alternative ways to increase the purity of hydrogen produced in a membrane reactor for ammonia decomposition – by increasing the thickness of the membrane selective layer, or using a purification unit in the permeate of the membranes. They said membrane thickness above 6 micrometers (μm) of ultra-pure hydrogen can be obtained at pressures below 5 bar. Their study, published in the International Journal of Hydrogen Energy, shows that Pd-based membranes deteriorate when exposed to temperatures higher than 500 C. “A cheaper solution, however, consists in the use of an adsorption bed downstream the membrane reactor,” the researchers wrote. “Ultra-pure hydrogen can be achieved with higher reactor pressures, lower temperatures and thinner membranes, which result in lower reactor costs.”

ACWA Power has signed a $7 billion agreement with two state-owned companies in Thailand to develop green hydrogen. ACWA Power, PTT Public Company Ltd. (PTT), and the Electricity Generating Authority of Thailand (EGAT) will conduct an investment feasibility study for proposed green hydrogen and derivatives projects. They aim to produce around 225,000 tons of green hydrogen per year, said ACWA Power.

HDF Energy and US International Development Finance Corp. (DFC) have agreed to support the development of green hydrogen plants in Indonesia. The facilities will use HDF Energy’s technology, Renewstable, which combines renewable sources and mass. The French company said that DFC’s technical assistance will support feasibility studies for its pipeline of 22 Renewstable projects in Indonesia, for an investment of $1.5 billion, backed by development institutions.

Rolls-Royce and EasyJet claim to have pulled off the “world’s first run of a modern aero engine on hydrogen.” The companies performed the ground test in the United Kingdom with a converted Rolls-Royce AE 2100-A regional aircraft engine and hydrogen generated by renewables in the Orkney Islands. “Following analysis of this early concept ground test, the partnership plans a series of further rig tests leading up to a full-scale ground test of a Rolls-Royce Pearl 15 jet engine,” wrote the automaker.

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