A novel dual-pressure single-mixed refrigerant cryogenic system for hydrogen precooling process: Optimization and thermoeconomic analysis

• Published in: International journal of hydrogen energy 2024-10, Vol.85, p.893-908
• Main Authors: Sleiti, Ahmad K., Al-Ammari, Wahib A.
• Format: Article
• Language: English
• Subjects: Comparison; Cryogenic process; Energy consumption; Liquid hydrogen; Mixed refrigerants; Optimization method
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2024.08.391

Producing liquid hydrogen (LH2) is an energy-intensive process as 30% of the LH2 energy is consumed during liquefaction in the existing commercial plants. Thus, numerous innovative liquefaction processes were proposed to achieve a significant reduction in the specific energy consumption (SEC) of the LH2 production systems. In particular, single-mixed refrigerant (SMR) and dual-mixed refrigerant (DMR) hydrogen precooling processes were introduced as efficient alternatives for conventional precooling processes. However, the SEC of the SMR is still high (>2 kWh/kgH2) and lacks efficient and practical optimization. On the other hand, the DMR demonstrates efficient operation (SEC close to 1.0 kWh/kgH2) but with a more complex configuration and higher capital cost. To address these gaps, this study (i) presents a new dual-pressure SMR precooling process (DP-SMR) that combines the simplicity of the SMR process and efficient operation of the DMR process, (ii) proposes a new optimization method for the cryogenic process with systematic implementation on the SMR, DMR, and the proposed DP-SMR processes, and (iii) conducts systematic thermoeconomic assessment for the optimized cases of the precooling processes. The proposed optimization method integrates knowledge-based optimization (KBO) procedures with other efficient optimization algorithms including genetic algorithm optimization (GAO), particle swarm optimization (PSO), and Bayesian optimization (BO). This method fosters the optimization process and ensures the achievement of optimal performance that satisfies all design constraints without performing penalty functions. The results show that the SEC of the proposed DP-SMR process is 1.29 kWh/kgH2, which is 6%–10% lower than all SMR processes available in the literature. In addition, the levelized precooling cost of the DP-SMR process is 2.15% and 16.00% lower than that of the optimized DMR and SMR processes, respectively. The proposed optimization procedures in this study will facilitate the achievement of robust optimization performance for any cryogenic process including hydrogen, nitrogen, and natural gas liquefaction systems. •A new dual-pressure single mixed-refrigerant hydrogen precooling process is proposed.•A new optimization method for the cryogenic process is introduced.•Systematic thermoeconomic analysis for three H2 precooling processes is conducted.•The energy consumption of the proposed process is reduced by 10%.•The H2 precooling cost is reduced by