Refrigeration system for a natural gas liquefaction process

A refrigeration system for pre-cooling natural gas or cooling a mixed refrigerant for liquefying natural gas by using a propane refrigerant in a natural gas liquefaction process, comprising:

• a supply source of a propane refrigerant;
• an expansion device for depressurizing said propane refrigerant supplied from said supply source;
• a separation drum for separating said propane refrigerant obtained from said expansion device into a gas fraction and a liquid fraction;
• a heat exchanger for cooling natural gas or a mixed refrigerant for liquefying natural gas by using said propane refrigerant obtained from said separation drum as a boiling liquid, and returning said propane refrigerant consisting of a mixture of vapor and liquid after exchanging heat to said separation drum;
• a next-stage expansion device for extracting and depressurizing a part of said propane refrigerant obtained as liquid from said separation drum;
• a next-stage separation drum for separating said propane refrigerant obtained from said next-stage expansion device as a mixture of vapor and liquid into a gas fraction and a liquid fraction;
• a next-stage heat exchanger for cooling natural gas or a mixed refrigerant for liquefying natural gas with said propane refrigerant obtained from said next-stage separation drum as boiling liquid, and returning said propane refrigerant consisting of a mixture of vapor and liquid after exchanging heat to said next-stage separation drum;
• and
• a vapor conduit for returning said propane refrigerant obtained from said next-stage separation drum as vapor to said supply source;
• said heat exchangers each consisting of a plate-fin heat exchanger in which a plurality of passages for said natural gas or said mixed refrigerant extend over an entire length thereof in mutually separated relationship with said propane refrigerant being passed vertically in said plate-fin heat exchanger;
• said separation drums each consisting of a horizontally disposed, laterally elongated drum connected to said corresponding plate-fin heat exchanger as a thermo siphon drum for said propane refrigerant.

A cooling system suitable for use in a refrigeration system for pre-cooling natural gas or cooling a mixed refrigerant for liquefying natural gas by using a propane refrigerant in a natural gas liquefaction process, comprising:

• a plate-fin heat exchanger including a plurality of passages for said natural gas or said mixed refrigerant which extend in a mutually separated relationship substantially over an entire length of said plate-fin heat exchanger, said propane refrigerant being passed vertically in said plate-fin heat exchanger;
• a plurality of separation drums for said propane refrigerant defined inside a laterally elongated, horizontally disposed tank separated by a plurality of partition walls, said separation drums being connected to said plate-fin heat exchanger;
• and
• said plate-fin heat exchanger extending in a lengthwise direction of said passages through said separation drums across said partition walls and substantially submerged in a liquid part of said propane refrigerant in each of said separation drums.