Decarbonisation Technology May 2026 Issue

Case 1: Full conversion from grey to clean ammonia for a legacy plant in Europe Existing ammonia plant The facility under study is a legacy ammonia plant constructed in the 1980s, currently operating at approximately 1,765 short tons per day (stpd) using natural gas as the primary feedstock. The plant follows a conventional process flow scheme, as illustrated in Figures 1a and 1b . The existing steam system is also traditional in design. The syngas compressor turbine is driven by high-pressure (HP) steam, supplied from a header operating at approximately 124 bar. Meanwhile, the process air compressor turbine and the ammonia refrigeration compressor turbine are both connected to a medium- pressure (MP) steam header, operating at around 40 Bar. This baseline configuration served as the foundation for evaluating the technical and economic feasibility of a complete conversion to clean ammonia production using low-carbon hydrogen feedstocks. Hydrogen and nitrogen sourcing The clean ammonia facility will utilise two distinct hydrogen feed sources: • OTF hydrogen produced via USW (alternatively called municipal solid waste or MSW) gasification, available from an adjacent third-party supplier. • Pipeline-supplied hydrogen delivered through the EHB network, expected to come online in alignment with the pipeline’s phased commissioning schedule. The USW-derived hydrogen will be available in limited quantities, sufficient to support approximately 35-40% of the plant’s total ammonia production capacity. The EHB pipeline will meet the remaining hydrogen requirement as infrastructure becomes operational. Nitrogen feed will be supplied over-the- fence via a dedicated pipeline from a nearby air separation unit (ASU), ensuring consistent purity and pressure for integration into the synthesis loop (synloop). Feedstock quality The hydrogen supplied via pipeline originates from diversified production sources and

contains trace levels of several contaminants that must be addressed before synthesis. Key impurities identified in the feed include chlorides, sulphur – inorganic, CO, CO₂, O₂, formic acid, and formaldehyde. These impurities pose a risk to both catalyst performance and the integrity of downstream equipment. In particular, sulphur compounds and CO are known catalyst poisons, while chlorides can contribute to corrosion and fouling. Effective purification strategies are crucial for reducing these contaminants to levels compatible with the specifications of ammonia synthesis catalysts and ensuring long-term plant reliability. Key challenges and mitigation: • Hydrogen purification. • Hydrogen availability. • Compressor configurations. • Synloop rerating and reconfiguration. • Steam system. • Economic justification. The listed impurities in the hydrogen are poisonous to the synthesis catalyst and need to be removed to well below the acceptable limits. The following challenges were posed for the design of the new hydrogen purification system: u A viable and cost-effective method for removing formic acid and formaldehyde was not available. Additionally, leading catalyst vendors lacked prior experience with these compounds, and the industry’s understanding of their behaviour within the ammonia production process remains limited. A layer of special adsorbent was suggested to be added to the existing dryers to partially mitigate traces of formic acid and formaldehyde. v Limited degree of H₂ feed preheat (<500°F) due to the unavailability of HP steam. This means that the conventional catalysts used in ammonia plant feed purification cannot be used to remove the impurities. Alternative lower-temperature catalysts were reviewed and carefully configured, incorporating numerous feedback points from different catalyst suppliers. w To minimise the cost, the existing desulphurisers and methanation vessels were intended to be reused. A limited availability of feed hydrogen for an