Three-stream spiral wound type heat exchange equipment for secondary refrigeration and low-temperature liquefaction of LNG (liquefied natural gas)

Abstract

The invention belongs to the technical field of low-temperature natural gas liquefaction, and relates to LNG (liquefied natural gas) secondary low-temperature liquefaction equipment and the technique of refrigeration by mixed refrigerant. C2H4 refrigerant and N2-CH4 mixed refrigerant steam of 0.3MPa and -130 DEG C from an LNG three-level outlet are used for cooling and liquefying natural gas of 5.8MPa and -53 DEG C in a three-stream spiral wound type heat exchanger, so that LNG can conveniently enter a three-level undercooling stage. The three-stream spiral wound type heat exchanger for secondary liquefaction is used for undercooling the C2H4 refrigerant first, the undercooled C2H4 refrigerant is throttled to a shell side to be mixed with the N2-CH4 to cool a -53-DEG C LNG pipeline, a N2-CH4 precooling tube bundle and a C2H4 undercooling tube bundle, so that undercooling of the C2H4 and precooling of the N2-CH4 and liquefaction of natural gas are realized. The equipment is compact in structure and high in heat exchange efficiency, and can be used for the field of phase-variable low-temperature heat exchange of gas at temperature ranging from -53 DEG C to -120 DEG C, the problem of LNG secondary low-temperature liquefaction is solved, and low-temperature heat exchanging efficiency of an LNG system can be improved.

Description

technical field [0001] The invention belongs to the technical field of low-temperature liquefaction of natural gas, and relates to LNG secondary low-temperature liquefaction equipment and mixed refrigerant refrigeration technology. 2 h 4 Refrigerant and LNG secondary inlet 0.3MPa, N at -130°C 2 —CH 4 The mixed refrigerant vapor cools the 5.8MPa, -53°C natural gas to -120°C and liquefies in the three-stream spiral wound tube heat exchanger, so that the LNG enters the third-stage subcooling section; the second-stage refrigeration three-stream spiral wound tube heat exchanger The heater is first supercooled C 2 h 4 Refrigerant, C 2 h 4 After subcooling, it is throttled to the shell side and N 2 —CH 4 After mixing, cool the -53°C LNG tube bundle from the first stage, N 2 —CH 4 Precooling tube bundle and C 2 h 4 The subcooled tube bundle makes the natural gas and N in the tube pass 2 —CH 4 Middle CH 4 liquefied, reaching supercooled C 2 h 4 , precooling N 2 —CH 4...

AI Technical Summary

Problems solved by technology

At present, most mixed-refrigerant natural gas liquefaction systems adopt an integral heat exchange method, which connects the three-stage refrigeration process as a whole. The height of the heat exchanger can reach 60-80 meters, and the heat exchange efficiency has been significantly improved. The technological process is too complicated, and the volume of the heat exchange equipment is too large, which brings serious inconvenience to the processing and manufacturing, on-site installation and transportation, and once there are problems such as pipeline leakage, it is difficult to detect, and it is easy to cause the entire heat exchanger to be scrapped and the complete set of process equipment to stop production

In addition, because ordinary tube-and-tube heat exchangers adopt the tube-sheet connection parallel tube bundle method, the structure is simple, and the self-shrinking ability is poor. Generally, the heat exchange is performed by a single flow, the heat exchange efficiency is low, the volume is large, and the temperature difference is small. Cool and liquefy natural gas in one process

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