Energy‐effective carbon dioxide capture and storage design in hydrogen production from liquefied natural gas

Abstract

To solve the problems of excessive CO2 emission and low resource utilization, which exist in the original hydrogen production process that occurs in an oil refinery, the original natural gas steam reforming process is improved by proposing a new coupled energy-effective hydrogen production process from liquefied natural gas (LNG) with a CO2 capture and storage (CCS) unit; this is based on the background that the oil refinery takes the LNG of the adjacent receiving station as feedstock to produce hydrogen products. The newly designed process recovers the high-grade cold energy released by the raw LNG during gasification to liquefy the CO2 generated in the process, which achieves energy integration to the greatest extent and improves the energy utilization efficiency. Meanwhile, the unreacted raw gas is recycled to improve the resource utilization. Moreover, to obtain the optimal operating parameters of the new process for further evaluation of its advantages, the global optimization model with the optimal overall economic benefit as the objective function is established and the best-operating conditions for the new process with optimal economic benefit are obtained. The result of the energy analysis of the thermodynamic process indicates the exergy efficiency of the new process reaches 60.14%. Compared with the original process, even though the total energy consumption of the new process is increased, the economic benefit still grows by 123.6 million CNY/year owing to the increasing of CO2 product benefit with a high recovery rate of 99.5% in the hydrogen production process and an overall CO2 recovery rate of 69.72%. This study can provide theoretical references for the design and actual production of the hydrogen production process from natural gas.