Decarbonisation Technology May 2026 Issue

Clean conversion dilemma for legacy ammonia plants Case studies and the actual plant data demonstrate full conversion pathways leveraging existing infrastructure while meeting regulatory and sustainability goals

D ecarbonising legacy and new ammonia plants presents complex technical and economic challenges, particularly since these facilities were initially designed around unabated steam methane reforming (SMR). However, strategic integration planning, robust process design, and selective retrofits can enable the adaptation of key systems – such as synthesis loops, compression trains, and heat recovery units – to accommodate low-carbon feedstocks like blue and green hydrogen. This article explores practical decarbonisation pathways through a European case study of complete conversion and three US case studies of partial conversion strategies, including green hydrogen blending and oxygen enrichment. The findings underscore a phased, cost-effective approach that leverages existing infrastructure while aligning with regulatory and sustainability goals. Overview of study cases This article presents four techno-economic evaluations conducted by Kinetics Process Improvements, Inc. (KPI), each offering a distinct perspective on clean ammonia transition strategies. The case studies span full-scale conversions and partial integrations, reflecting a range of plant configurations, regional drivers, and decarbonisation approaches. Case 1: Full conversion from grey to clean ammonia for a legacy plant in Europe A comprehensive redesign of an existing ammonia synthesis loop was undertaken to enable operation exclusively on clean hydrogen, sourced primarily from the European Hydrogen VK Arora Kinetics Process Improvements, Inc. (KPI)

Backbone (EHB) pipeline and supplemented by over-the-fence (OTF) hydrogen from urban solid waste (USW) gasification. The study evaluated major retrofits, including the installation of a new purification system to remove trace impurities and the complete phase-out of conventional reforming and CO₂ removal systems. Key regulatory and infrastructure drivers for this full-scale transition are discussed in detail later in the article. Case 2: Green hydrogen and oxygen integration to debottleneck a new US facility At a newly built US ammonia plant equipped with cryogenic purification technology, KPI investigated the injection of green hydrogen and moderate oxygen enrichment to alleviate specific bottlenecks. These included overloaded arch burners, elevated tube metal temperatures in the SMR, and limitations in the cryogenic purifier. The integration strategy aimed to reduce carbon intensity, improve reliability, and achieve a modest increase in ammonia production. Case 3: Partial green hydrogen and oxygen integration in a legacy US plant A legacy ammonia facility explored the integration of green hydrogen and moderate oxygen enrichment using a 20 MW electrolyser system. While the oxygen enrichment pathway was ultimately deemed uneconomical due to the requirement for a dedicated compressor, the plant successfully implemented green hydrogen injection. As an early adopter, the facility capitalised on Inflation Reduction Act (IRA) incentives, achieving a viable business case despite high capital expenditure.