Thermodynamic Cycle Selection for Distributed Natural Gas Liquefaction Available to Purchase

Natural gas liquefaction plants with cooling capacities of approximately 100 kW are facilitating the development of a distributed LNG infrastructure. To be economically viable, liquefiers of this scale must be able to operate on a variety of feed gases while offering relatively low capital costs, short delivery time, and good performance. This paper opens with a discussion of a natural gas liquefier design focusing on the refrigeration system. Linde, cascade, mixed refrigerant, and modified‐Brayton cycle refrigeration systems are then discussed in context of the overall plant design. Next, a detailed comparison of the modified‐Brayton and mixed refrigerant cycles is made including cycle selection’s impact on main system components like the recuperative heat exchanger and compressors. In most cases, a reverse‐Brayton or a mixed refrigerant cycle refrigerator is the best‐suited available technology for local liquefaction. The mixed refrigerant cycle liquefier offers the potential of better real performance at lower capital costs but requires more know‐how in the areas of two‐phase flow and refrigerant composition management, heat exchanger design, and process control.