Economic analysis of mixed-refrigerant cycle and nitrogen expander cycle in small scale natural gas liquefier

Abstract

Two types of natural gas liquefaction processes, mixed-refrigerant cycle and nitrogen expander cycle were simulated. Their process parameters were optimized and compared. Their economic characteristics were analyzed. Although the mixed-refrigerant liquefaction process is more complicated than nitrogen expander cycle, its energy consumption is only 46% of the nitrogen expander cycle. The operation costs of mixed-refrigerant process are lower than those of nitrogen expander cycle, so the process is more competitive. The energy consumption of the optimized mixed-refrigerant cycle reaches the level of propane pre-cooled mixed-refrigerant process, which is usually used in base-load natural gas liquefaction systems and is the lowest of the mixed-refrigerant process. The process is comparatively simple, consumes less energy and has economic benefits, so the mixed-refrigerant process is the preferred choice for small-scale natural gas liquefaction device. © 2008 American Institute of Physics.