Hydrogen Recovery, Green and Blue Hydrogen

Refineries produce hydrogen-containing off-gas streams from catalytic reforming, hydrocracking and other processes. Recovery of hydrogen from these streams using PSA systems improves the efficiency of the refinery hydrogen network, reducing the requirement for produced hydrogen from dedicated hydrogen plants.

PSA-based hydrogen recovery from reformer off-gas, hydrocracker purge and other off-gas streams is a well-established application. The PSA system is designed to meet the feed gas composition and produce hydrogen at the purity required by the consuming units.

Steam methane reforming is the dominant industrial process for hydrogen production. In the SMR process, natural gas (or other light hydrocarbons) reacts with steam over a catalyst in reformer tubes at high temperature to produce a synthesis gas mixture of hydrogen, CO, CO₂ and unreacted methane and steam.

The synthesis gas is cooled and the CO content reduced in a water gas shift (WGS) reactor before the hydrogen is separated and purified in a downstream PSA system. The PSA tail gas — containing CO₂, CO, CH₄ and H₂ — is typically used as fuel gas in the reformer furnace.

SMR produces grey hydrogen in its conventional form. To produce blue hydrogen, CO₂ from the SMR process must be captured — either from the PSA tail gas, the SMR flue gas or both — and stored or used to prevent release to atmosphere.

Blue hydrogen is hydrogen produced from fossil fuels with carbon capture and storage (CCS) to reduce or eliminate the associated CO₂ emissions. In the SMR route to blue hydrogen, CO₂ is captured from the SMR process gas streams and compressed for transport and storage.

Several CO₂ capture configurations are possible for SMR blue hydrogen, including pre-combustion capture from the PSA tail gas or process gas, post-combustion capture from the flue gas, or a combination of both. The choice of configuration affects the overall CO₂ capture rate, the hydrogen production efficiency and the capital and operating cost.

Green hydrogen is produced by water electrolysis powered by renewable electricity. The electrolyser produces hydrogen and oxygen. The hydrogen product requires purification — typically drying and deoxo treatment, and in some cases PSA polishing — before it can meet the specification for the intended end use.

The balance-of-plant (BOP) engineering for a green hydrogen project includes hydrogen purification, compression, storage and dispensing or export systems. This BOP scope is a significant part of the overall project and requires integration with the electrolyser output conditions and the downstream requirements.

Howe Baker provides engineering services across multiple hydrogen production and purification routes. This includes PSA systems for hydrogen recovery and purification, SMR engineering and revamp services, green hydrogen BOP and purification system engineering, and CCUS integration for blue hydrogen applications.