Liquefied natural gas (LNG) low temperature liquefied three-level refrigeration spiral wound tube type heat exchanger

Abstract

The invention belongs to the field of natural gas low temperature liquefied technology, and relates to a liquefied natural gas (LNG) three-level low temperature liquefied process device and a mixed refrigerant refrigeration technology, which cools 6.0MPa, -120DEG C natural gas into -164DEG C to be liquefied in two-steam spiral wound tube type heat exchanger by applying a certain proportion of non-azeotropic N2-CH4 mixed refrigerant, thereby being convenient for LNG to be stored in a surpercooling mode and being convenient to transport. The non-azeotropic N2-CH4 mixed refrigerant is firstly precooled and liquefied by a three-level refrigerant spiral wound tube type heat exchanger, and is throttled to a shell pass after being liquefied to cool a LNG tube bundle and a N2-CH4 mixed refrigerant precooling tube bundle from a secondary outlet in -120DEG C, thereby leading natural gas and precoolded refrigerant in the tube pass to be liquefied, and achieving the purpose of precooling mixed refrigerant before throttling and liquefying nature gas at low temperature. The LNG three-level low temperature liquefied process device is compact in structure and high in heat exchange efficiency, can be used to exchange heat for mixed gas with low-temperature phase transition, solves the difficult problem of LNG three-level low temperature technology, and increases low temperature heat exchange efficiency of a LNG system.

Description

technical field [0001] The invention belongs to the technical field of low-temperature liquefaction of natural gas, and relates to equipment for a three-stage low-temperature liquefaction process of LNG and a mixed refrigerant refrigeration technology, which uses a certain ratio of non-azeotropic N 2 —CH 4 The mixed refrigerant cools 6.0MPa, -120°C natural gas to -164°C and liquefies it in a two-flow spiral wound tube heat exchanger, so as to facilitate LNG storage and transportation. The three-stage refrigeration spiral wound tube heat exchanger first precools and liquefies non-azeotropic N 2 —CH 4 Mixed refrigerant, after being liquefied, the mixed refrigerant is throttled to the shell side to cool the LNG tube bundle with an outlet temperature of -120°C and N 2 —CH 4 The mixed refrigerant pre-cooling tube bundle liquefies the natural gas and pre-cooling refrigerant in the tube side, achieving the purpose of pre-cooling the mixed refrigerant before throttling and low-tem...

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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