Transitioning refinery hydrogen systems from grey to green The engineering considerations for transitioning refinery hydrogen systems from reformer-based grey hydrogen to electrolyser-based green hydrogen
Ishita Bansal Expert on Energy Transition & Digital Transformation
H ydrogen is a critical utility in modern refineries, underpinning key conversion and upgrading processes, such as hydrotreating, hydrocracking, delayed coking, and residue upgrading. Hydrogen availability, purity, and pressure stability directly influence refinery throughput, product quality, catalyst activity, hydrogen partial pressure, and overall unit severity. In hydrogen-intensive refineries, even short-duration disruptions in hydrogen supply can rapidly translate into throughput loss, off-spec products, accelerated catalyst deactivation, increased make-up hydrogen demand, or forced unit rate reductions. As a result, hydrogen system reliability is treated as a core operational requirement rather than a secondary utility consideration. In most Indian refineries, hydrogen demand is predominantly met through captive steam methane reforming (SMR) units. These systems are designed for continuous, steady-state operation, delivering high-purity hydrogen at relatively stable pressures and flow rates aligned with base-load refinery operation. Over decades of operation, refinery hydrogen networks, headers, compressor configurations, purification schemes, and control philosophies have been optimised around the predictable operating characteristics of reformers, shift reactors, CO₂ removal systems, and downstream purification units. Hydrogen system design has therefore prioritised stability, availability, and predictability over operational flexibility. While SMR-based hydrogen systems are well proven and operationally robust, they also represent a significant source of direct carbon
dioxide (CO2) emissions and expose refineries to volatility in natural gas pricing, long-term fuel supply security, and geopolitical risk. With tightening emissions norms, increasing scrutiny on refinery carbon intensity, and long- term uncertainty around fossil fuel economics, refinery hydrogen has emerged as one of the most impactful and technically complex levers for decarbonisation. Green hydrogen, produced through water electrolysis using low-carbon electricity, offers a potential pathway to reduce the carbon intensity of refinery hydrogen supply. However, transitioning from grey to green hydrogen in operating refineries is not a simple substitution exercise. Unlike greenfield projects, “ Green hydrogen, produced through water electrolysis using low-carbon electricity, offers a potential pathway to reduce the carbon intensity of refinery hydrogen supply ” operating refineries are constrained by legacy infrastructure, tightly integrated process units, limited operating margins, brownfield space constraints, and stringent reliability requirements. Introducing electrolyser-based hydrogen therefore brings a new set of engineering, operational, safety, and system- integration challenges that must be addressed in a structured and risk-managed manner. This article examines the key engineering considerations involved in transitioning refinery hydrogen systems from reformer-based grey hydrogen to electrolyser-based green
Refining India
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