Boil-off gas (BOG) liquefying process and device

Abstract

The invention relates to a boil-off gas (BOG) liquefying process and device. The BOG liquefying process comprises reheated low-temperature BOG is compressed to high pressure through a compressor, precooled and throttled, and most of the BOG is liquefied according to the high-pressure throttling and refrigerating principle. The BOG liquefying process is simple, single refrigerating fluid is adopted, no influence is imposed on an original system, a unified skid-mounting device can be manufactured easily, and the BOG liquefying process and device are particularly suitable for LNG storage and distribution stations and LNG charging stations.

Description

technical field [0001] The invention provides a BOG (Boil Off Gas, boil-off gas) liquefaction process and device, which are suitable for reliquefaction of BOG produced by LNG storage tanks and LNG loading and unloading systems. Background technique [0002] At present, my country's LNG industry is still in the development period, and BOG release is a relatively common phenomenon. For some LNG facilities with insufficient supporting vehicles and users, the annual release volume can often account for more than 10% of the total purchased gas volume. Serious It can even reach 30%. Reliquefaction of BOG can effectively alleviate the problem of frequent release of BOG in LNG filling stations and other LNG facilities. With a design gas filling capacity of 10000Nm 3 / d LNG filling station as an example, if the release rate is 10%, the annual direct economic loss is close to 200,000 yuan. It is extremely economical to reliquefy BOG to avoid this part of the cost loss as much as pos...

AI Technical Summary

Problems solved by technology

The release of BOG not only wastes energy, but also brings the risk of combustible gas combustion and explosion. At the same time, it causes serious greenhouse effect and pollutes the environment, which runs counter to my country's planning goals of environmental protection, energy conservation and emission reduction, and sustainable development.

[0004] At present, the liquefaction of BOG is mostly applied in that BOG enters the cold box after being pressurized by the compressor, and is liquefied under the cooling action of the refrigerant in the cold box by using expansion refrigeration, mixed refrigeration, cascade refrigeration and other refrigeration methods. The original natural gas liquefaction system has a certain dependence, especially when the amount of BOG fluctuates greatly, it is easy to affect the stability of the natural gas-refrigerant heat exchange system in the cold box, and it is necessary to add a special BOG heat exchange flow channel, so the cold box The structure and refrigeration process of the box are relatively complicated, and the investment is high

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