Energy-efficient liquid hydrogen production using cold energy in liquefied natural gas: Process intensification and techno-economic analysis

The operating temperature within the value chain of liquefied hydrogen, from liquified natural gas supply to hydrogen production and liquefaction, widely varies from cryogenic to extremely high, allowing heat integration in its intra-value chain. In this study, we aim to develop conceptual designs of heat integration at various levels for the liquid hydrogen production process, including HPF and HLP, to boost energy efficiency and reduce the levelized cost of hydrogen (LCOH). The installation of heat exchanger networks (HENs) can improve the energy efficiency of the process and lower energy costs while increasing process capital costs. Hence, we proposed various heat integration strategies considering crucial integration points: 1) liquefied natural gas (LNG) evaporation via heat exchanger by employing high-temperature process streams, 2) LNG cold energy utilization for precooling gas hydrogen (GH₂) in HPF and 3) heat recovery from hot process streams, such as steam methane reforming (SMR) and water–gas shift outputs, in HEN via pinch technology. Consequently, the optimal process containing all heat integration strategies had the best energy efficiency (84.5%), cost-effectiveness (LCOH at 4.91 $/kg), and environmental friendliness (unit CO_2eq emission at 7.67 kg CO_2eq/kg H₂). This study proposes the effective HEN for the blue H₂ production process, regardless of whether it uses highly efficient continuous SMR or flexible start-up/shut-down autothermal reforming for various operational objectives. It also includes a comparison of LCOH and CO₂ emissions during the production of various H₂ types in gas resources and environmental policy situations of various countries.