Integration of CO2 cryogenic removal with a natural gas pressurized liquefaction process using gas expansion refrigeration

• Propose a novel pressurized liquefaction process integrated with CO2 removal.
• Optimize proposed processes with and without precooling using energy criterion.
• CH4 refrigerant not only saves energy but also achieves a high liquefaction rate.
• CO2 precooling refrigerant is low in price and acceptable in energy efficiency.
• Using precooling reduces energy by more than 14% but also increases complexity.

Space limitation is a great challenge in offshore liquefied natural gas production. A novel natural gas liquefaction process aimed at footprint reduction is first proposed in this study. The novel process uses pressurized liquefaction technology to decrease the size of the heat exchanger, and it adopts CO2 cryogenic removal to eliminate the large CO2 pretreatment facility so as to achieve a small footprint. Since energy consumption is always a big concern for a natural gas liquefaction process, this study performs optimization for the proposed process. Taking the specific power consumption as the objective function, the proposed process is optimized by the sequential search method using HSYSY simulation. In this study, the proposed processes with and without precooling are both studied and the effect of precooling is discussed. Various refrigerants are employed in the proposed processes and their optimal performances are compared and analyzed. Furthermore, natural gas with different CO2 contents is used as feed gas to investigate the effect of CO2 content on energy consumption. In conclusion, the proposed novel process with a small footprint and low energy consumption provides a promising option for offshore liquefied natural gas production.