Liquefaction is recognized as one of the economical and feasible strategies for storing and transporting natural gas (NG). Among several NG liquefaction processes, the single mixed refrigerant (SMR) process are considered most suitable for offshore liquefied NG (LNG) production, mainly due to simple and compact design. However, these processes consume a tremendous amount of energy that leads to high operating costs. Therefore, process engineers and researchers associated with FLNG-FPSO industry are still trying to enhance the performance of the offshore LNG processes. Within this context, this study presents an innovative enhancement in SMR liquefaction process by introducing high-boiling mixed refrigerant self-recuperator. The proposed selfrecuperative SMR process is further enhanced by replacing Joule-Thomson (JT) valve with cryogenic liquid turbine, which ultimately reduces the overall process entropy generation. The proposed process gives LNG product with ≥94.0% liquefaction rate on the expense 4.98 kW/kmol-NG that is 19% and 25% lower than that of JT valve based self-recuperative SMR process and convention SMR process, respectively. The proposed enhancement can also be employed to other energy intensive refrigerant and liquefaction processes in order to improve an overall process efficiency.
Keywords Liquefied natural gas, single mixed refrigerant, nitrogen expander liquefaction process, nitrogen self-recuperation, composite curves, compression power