1. Classification of natural gas liquefaction process

At present, the types of natural gas liquefaction processes are mainly divided based on their functions and cooling methods.

(1) According to its function, it can be divided into basic load liquefaction unit and peak load liquefaction unit, and small LNG unit belongs to peak load liquefaction unit.

(2) According to the refrigeration method can be divided into: ① cascade liquefaction process; ② Mixed refrigerant liquefaction process, including closed, open, propane precooling, CII, etc.; (3) Liquefaction process with expander, including natural gas expansion, nitrogen expansion, nitrogen methane expansion, etc.

However, the above classification is not strict, and a composite process is usually used that includes different combinations of some parts of the various liquefaction processes described above, each of which contains multiple forms.

2. Type and composition of natural gas liquefaction unit

The types of natural gas liquefaction units mainly include basic load type liquefaction unit, peak load type liquefaction unit, floating LNG production, storage and unloading unit and LNG receiving terminal, which are defined as follows.

(1) Basic load liquefaction unit: refers to the production of large liquefaction units for local use or external transport.

(2) peaking liquefaction device: refers to the natural gas liquefaction device for peaking load or supplementing winter fuel supply, usually the excess natural gas at low peak load is liquefied and stored, and then vaporized for use in peak or emergency situations.