BOG reliquefaction circulating system for LNG (Liquefied Natural Gas) ship based on mixed working medium refrigeration technology

Abstract

The invention relates to a BOG reliquefaction circulating system for an LNG ship based on a mixed working medium refrigeration technology. The system comprises a main cold cycle and a reliquefaction cycle, wherein the reliquefaction cycle exchanges heat with a mixed working medium in the main cold cycle through a multi-stage heat exchanger, the multi-stage heat exchanger comprises at least one intermediate heat exchanger used for joint heat exchange of gas and liquid refrigerants and a low-temperature heat exchanger used for heat exchange of gaseous refrigerants, the reliquefaction cycle comprises a normal-temperature supercharger, a BOG cooler, the multi-stage heat exchanger, a first throttling device, a gas-liquid separator and an LNG storage tank which are sequentially arranged in a feed gas flowing direction, BOG generated by the LNG storage tank sequentially enters the low-temperature heat exchanger and the intermediate heat exchanger, exchanges heat with the mixed working medium, is heated and then flows to the inlet end of the normal-temperature supercharger to form a loop, and medium-and-low-temperature BOG at the outlet end of the BOG cooler sequentially enters the intermediate heat exchanger and the low-temperature heat exchanger to be cooled step by step so as to realize liquefication. The reliquefaction system achieves near-normal-temperature pressurization of BOG, and meanwhile, mixed refrigerants and BOG cold energy are effectively utilized.

Description

technical field [0001] The invention relates to the technical field of LNG storage and transportation, in particular to a BOG reliquefaction cycle system for LNG ships based on mixed working medium refrigeration technology. Background technique [0002] With the increasing share of LNG in the global energy market, the LNG transportation industry has achieved unprecedented development. The demand for LNG is growing steadily at a rate of more than 5% per year, and the development of the LNG industry will continue to improve in the long run. In the LNG marine transportation industry, the LNG ship is an important tool connecting the natural gas liquefaction plant and the LNG receiving terminal. In this context, the global LNG ship shipping market is on the rise, and the demand for LNG ships has soared. From 2018 to 2020, the global LNG ship orders will reach 190. With the launch of new LNG projects, the super cycle of LNG ships will come. It is estimated that the global demand...

AI Technical Summary

Problems solved by technology

[0006] In the conventional mixed working fluid reliquefaction system, BOG cryogenic compressor is its core equipment, long-term dependence on imports increases the cost of equipment; during the process of marine use of the mixed working medium BOG reliquefaction device, the system reliability is reduced due to the neck problem of the core equipment ; In addition, in the circulation system, the cold energy of the mixed refrigerant and BOG has not been effectively utilized, and the energy efficiency of the reliquefaction system is low

Images