Precooling method before unloading of LNG (Liquefied Natural Gas) tank wagon

Abstract

The invention relates to a precooling method before unloading of an LNG (Liquefied Natural Gas) tank wagon. The precooling method comprises the steps of opening a first liquid inlet control valve of a storage tank, opening a self-pressurization gaseous phase and liquid inlet pipeline communicating valve of an unloading deck, opening a second upper liquid inlet control valve of a liquid-unloading storage tank to form an included angle of 25-35 degrees to precool a liquid inlet pipeline, opening the second upper liquid inlet control valve of the liquid-unloading storage tank to form an included angle of 55-65 degrees after 4-6min, completely opening the second upper liquid inlet control valve of the liquid-unloading storage tank after 4-6min again, opening a gaseous phase control valve of a self-pressurization system, a self-pressurization gaseous phase control valve of the tank wagon and a first gaseous phase control valve of the tank wagon, opening a self-pressurization liquid phase control valve of the unloading deck, opening a self-pressurization liquid phase control valve of the tank wagon to form an included angle of 10-20 degrees, pressurizing the tank wagon, opening a first self-pressurization gaseous phase and BOG (Boil Off Gas) system communicating valve of the unloading deck after the pressure is increased to be 0.5-0.6MPa, opening the self-pressurization gaseous phase and liquid inlet pipeline communicating valve of the unloading deck, enlarging the opening degree of the self-pressurization liquid phase control valve of the tank wagon to form an included angle of 60-90 degrees after the pressure of the tank wagon is reduced to be 0.3-0.4MPa, and completely opening after 4-5min. The pipe network can be well precooled, the precooling speed is high, and the precooling effect is thorough without blind areas.

Description

technical field [0001] The invention relates to the field of natural gas storage, in particular to a method for precooling an LNG tank car before unloading. Background technique [0002] The traditional precooling process is: open the gas phase control valve of the self-pressurization system; 2. Open the self-pressurization liquid phase control valve of the unloading platform; Pressurize, when the pressure increases to 0.5~0.6 MPa, open the first connecting valve and the second connecting valve between the self-pressurized gas phase of the unloading platform and the BOG system, and open the connecting valve between the self-pressurized gas phase of the unloading platform and the liquid inlet pipeline, BOG and The connection valve of the liquid inlet pipeline, confirm to open the first control valve of the liquid inlet of the storage tank, and pre-cool the liquid inlet pipeline; Degree to 60~90°, until fully open. 5. After 35-45 minutes of pre-cooling, the outer wall of the...

AI Technical Summary

Problems solved by technology

[0004] In order to solve the problems of long pre-cooling time and blind spots in the traditional pre-cooling method, the present invention provides a pre-cooling method before unloading LNG tankers, which can pre-cool the pipe network very well, and not only have a fast pre-cooling speed , and the pre-cooling is thorough, without blind spots

Images