A novel integrated structure for hydrogen purification using the cryogenic method

A cryogenic-based module is developed for the separation of the hydrogen from a feed gas mixture including nitrogen and linear branched or cyclic C-1 similar to C-6 hydrocarbons. The feed gas mixture is initially separated in a network of heat exchangers and phase separators to produce hydrogen-rich and hydrogen-lean streams. The hydrogen-enrich stream is extracted from the cryogenic separation heat exchangers and the hydrogen-lean stream is processed through the cryogenic sections to remove non-hydrogen components and produce aromatic, low pressure, and high-pressure fuel streams. A Joule-Bryton propane refrigeration cycle and an auxiliary nitrogen refrigeration stream supply the required cryogenic streams. The process is energy and exergy analyzed and results show that the more than 88.4% of exergy destruction occurred in heat exchangers and the valves have the least role in exergy destruction. Moreover, sensitivity analysis shows that when the mole fraction of hydrogen in feed gas increases by 60.0%, the specific energy decreases by 38.0%, the required power increases by 68.6%, the exergy efficiency reduces by 58.3%, and the required heat increases by 60.0%. As well as, when the pressure of stream 23 increases by 10%, the reduction of exergy efficiency is 9.2%, the promotion of specific energy is 3.0%, the reduction of hydrogen recovery rate is 0.08%, and the increase of nitrogen refrigeration capacity is 10.60%. Therefore, a comprehensive view is needed to change the operational parameters to achieve the desired results. The proposed module may be combined with many other gas upgrading systems. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The cryogenic-based module is developed for hydrogen separation from gas mixtures, producing hydrogen-rich and hydrogen-lean streams through a network of heat exchangers and phase separators. Energy and exergy analysis show the impact of adjusting operational parameters on specific energy, power, exergy efficiency, and heat requirements. A comprehensive view is necessary to achieve desired results by changing operational parameters.