Abstract Nitrogen expander-based natural gas (NG) liquefaction processes are considered to be the most feasible and economic practices for offshore applications. The nitrogen single expander process is simple owing to… Click to show full abstract
Abstract Nitrogen expander-based natural gas (NG) liquefaction processes are considered to be the most feasible and economic practices for offshore applications. The nitrogen single expander process is simple owing to its single-phase operation, and it employs high occupational safety and environment-friendly refrigerants. However, this process has low energy efficiency. Recent advancements in expansion devices show the possibility of handling two-phase refrigerant flow in an economical and simple manner. Accordingly, this paper proposes two-phase expansion using an innovative binary mixed refrigerant (MR) composed of ethane and nitrogen (C2N). Furthermore, a propane-precooling refrigeration cycle is also implemented and evaluated to analyze greater potential benefits of ethane–nitrogen refrigerant with two-phase expansion. To assess the technical and commercial feasibility of the proposed liquefaction process, energy, exergy, and economic (3E) analysis is performed. Using the C2N two-phase expander LNG process, 47.83% energy can be saved with 55.25% exergy destruction minimization and 24.12% total annualized costs (TAC) savings as compared to previously published nitrogen single expander process. Whereas, the C3-precooled C2N process gives higher energy savings i.e., 52.45% but low TAC savings i.e., 1.6% as compared to nitrogen single expander LNG process. Considering TAC savings, the C2N process (without propane-precooling) can be a promising candidate for offshore applications.
               
Click one of the above tabs to view related content.