Small Ammonia Crackers for Hydrogen Refueling Stations – Materials, Processes and Techno Economic Analysis

Sammanfattning

To decarbonise heavy-duty road transport, economical hydrogen at refuelling stations is needed. Ammonia (NH₃) is an attractive hydrogen carrier, due to its high hydrogen density, relatively mild storage conditions, and the large global infrastructure. Ammonia needs to be distributed and cracked on-site into high-purity hydrogen for use in proton exchange membrane fuel cell (PEMFC) trucks. The techno-economics of handling small loads of ammonia cracking for hydrogen refuelling stations are not well covered in the literature, and this thesis aims to address this gap. This thesis presents a techno-economic assessment (TEA) and materials science analysis of two ammonia cracking technologies for a station with a 1 tonne per day continuous production of H₂. The boundary is from the ammonia tank to the hydrogen tank of the vehicle. After analysing nine cracking technologies, two were identified: the thermocatalytic reactor (TCR) with pressure swing adsorption (PSA) purification and mechanical compression (TRL 8–9), and the proton ceramic electrochemical reactor (PCER) using a BZCY based ceramic membrane (TRL 3–5). The TCR is built from established industrial materials: a non-precious Ni/Al₂O₃ catalyst bed (Fe and Co also considered) operating at 600–900°C, housed in nickel-based alloy reactor tubes and heat exchangers whose specification is set by the high temperature needed to overcome nickel's nitrogen-binding energy; the main materials-related limitation is catalyst sintering over time. The PCER instead integrates cracking, hydrogen separation and electrochemical compression in a single dense BZCY ceramic membrane reactor with porous Ni–BZCY cermet electrodes operating at 650–800°C; because only protons can permeate the electrolyte, the process delivers intrinsically high-purity hydrogen without a PSA step, but its cost uncertainty stems chiefly from the limited manufacturability, reproducibility and long-term durability data of large-area ceramic cells. Both technologies had process flow diagrams generated, and the capital cost (CAPEX), operating cost (OPEX) and hydrogen cost add-on (per kg H₂ produced) estimated through engineering cost methods. The TCR total installed CAPEX was calculated to be €4.31 million, with mechanical compression as the major component. The cost add-on per kg H₂ was estimated at €2.46 (more than 80% of OPEX being ammonia feedstock costs). The PCER CAPEX was estimated to be €4.01 million (best estimate, −30% to +50%), with a cost add-on of €2.37 per kg H₂; the wider uncertainty range reflects the pre-commercial maturity of ceramic membrane manufacturing rather than a fundamental cost disadvantage. The results are in line with the literature. Both technologies can be applied at this scale. The TCR is available on a commercial scale but has additional process steps and is compression-cost-sensitive. The PCER has higher efficiency and hydrogen purity (but no PSA); however, it remains pre-commercial with higher cost uncertainty rooted in its materials manufacturing readiness, and the ammonia price is the most sensitive cost factor for both technologies.