Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

2.4.26 Ammonia production using hydrogen from water electrolysisDescriptionChapter 2Electrolytically produced hydrogen can be used directly for the production of ammonia, andsuch operations existed in the mid 1990s in Egypt, Iceland and Peru. In this process, hydrogenfrom the water electrolysis plant and nitrogen from the air separation plant pass to separatestorage vessels, providing a buffer capacity and a stabilised gas pressure. Water electrolysisgives an extremely pure feed gas, containing only a very small amount of oxygen (0.1 – 0.2 %),compared to the synthesis gas generated from a hydrocarbon feedstock. Oxygen acts as a poisonto the ammonia converter catalyst and has therefore to be removed. This is carried out by meansof catalytic combustion, which takes place immediately after the mixing of hydrogen andnitrogen. A small amount of hydrogen reacts with the oxygen present producing water. Thepurified mixed gas (make-up gas) is then passed to a storage vessel that serves as a buffer forthe ammonia synthesis stage. The synthesis loop is the same as for fossil fuel-based ammoniaplants.Achieved environmental benefitsDirect emissions from this process are minimal compared to the steam reforming and partialoxidation process.Cross-media effectsNone believed likely.Operational dataNo specific information provided.ApplicabilityAmmonia production based on water electrolysis is currently carried out in plants of up to500 tonnes/day. The process is generally not considered economically viable. However, undercertain local circumstances (depending on the local price for electric power), it can still be aninteresting and competitive technology, in particular when renewable electric power isabundantly available.EconomicsThe process is generally not considered economically viable due to the actual price for electricpower.Driving force for implementationLocal considerations.References to literature and example plants[1, EFMA, 2000, 3, European Commission, 1997]Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 91