Elias Xanthoulis, Andrew Board, Attila Racz and Tobias Roelofs, Comprimo, part of Worley, look at typical routes to blue hydrogen production, and how to maximise CO2 removal at high thermal efficiency in blue hydrogen facilities.
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he need for decarbonisation of existing industrial operations drives the need for higher volumes of hydrogen production in many areas of the world. As the promise of large-scale green hydrogen is still some time away, reforming of natural gas, as currently applied in many installations, will continue to play a key role in the transition towards meeting the Paris Agreement goals. Adding CO2 capture to existing reforming installations and new greenfield natural gas reforming hydrogen production installations is a first step in reducing carbon emissions but warrants the question: at what capital and operational costs? The predominant operating cost in a reforming unit is due to the natural gas. In addition, the pricing of CO2 emissions in the EU-ETS has reached an all-time high1 contributing to current and future OPEX while validating the economic need for carbon capture. The different process line-ups in blue hydrogen production determine the height of the initial investment while the extent of carbon removal varies. This article seeks to provide an answer to the question above by assessing the main blue hydrogen line-up options, by focusing on the most important techno-economic parameters of the processes, namely thermal efficiency and their respective carbon capture rates achievable, to produce the required hydrogen purity.
Characteristics of a blue hydrogen plant A blue hydrogen facility has three significant design parameters: Carbon capture – requirement of a minimum of 90 to 95% total carbon capture (95%+ is rapidly becoming the benchmark). Thermal efficiency – requirement for high thermal efficiency targeting 75 to 80% (HHV basis, including power required), especially when natural gas cost is a significant factor, which is nearly always the case. Hydrogen quality – ensuring high quality industrial hydrogen production, such as meeting the ISO 14687 Hydrogen Fuel Quality, which requires H2 of a minimum of 98 mol% purity, and strict specification of level of impurities such as CO (CO <1ppmv). The hydrogen purity specification can be achieved via a pressure swing adsorption (PSA) or methanation purification step in which the design is actually governed not by the hydrogen purity but by the CO product specification. Specific to the PSA is the loss in the tail gas of approximately 6 to 8% of the feed to a PSA. The tail gas contains approximately 70 vol% hydrogen and it needs to be utilised as fuel gas in the HYDROCARBON 23
ENGINEERING
August 2021
