Systems design and techno-economic analysis of a novel cryogenic carbon capture process integrated with an air separation unit for autothermal reforming blue hydrogen production system

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In the transition of the global energy paradigm toward decarbonization, hydrogen is expected to play a crucial role as an energy vector. To enhance the sustainability of hydrogen as an energy source, it is important to reduce costs and carbon emissions in the hydrogen production. Among various hydrogen production technologies, the autothermal reforming (ATR)-based blue hydrogen production method can stand out as a promising option in terms of both economic and environmental considerations. However, there are several bottlenecks: (i) ATR requires an air separation unit that increases the cost burden, and (ii) conventional amine-based carbon capture method consumes a significant amount of energy. To address these bottlenecks, this study proposes a novel cryogenic carbon capture process for ATR-based blue hydrogen production. In the proposed process, air separation unit are utilized not only for oxygen production but also for carbon capture. The compressed air from the air separation unit provides cooling energy to the mixture gas, leading to solidification and separation of carbon dioxide. Despite imposing an additional burden on the air separation unit, it significantly reduces the energy and cost associated with carbon capture. Consequently, there exists a trade-off relationship between the increased load on the air separation unit and the decreased load in carbon capture. This trade-off was evaluated by comparing it with the conventional absorption-based carbon capture process in terms of energy and economic aspects. The proposed process exhibits a 36.4% reduction in total energy consumption, with a particularly approximately 49.5% decrease in the energy consumed for carbon capture (0.278 kW h/kg-CO2). The economic performance indicates an 11% decrease in the levelized cost of hydrogen (1.62$/kg-H2), and a 45.3% decrease in CO2 avoidance cost (40.1$/kg-CO2). The captured solid CO2 can offer advantages during storage and transportation. Furthermore, the potential utilization of cooling energy of solid CO2 from an end-user perspective is expected to contribute to the establishment of a new industrial value chain.