JPH0444159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquefied gas reliquefaction device, and more particularly to a liquefied gas reliquefaction device that prevents pressure increase in a liquefied gas storage container.

FIG. 1 is a conceptual diagram of an LNG reliquefaction device as an example of a conventional liquefied gas reliquefaction device.

At an LNG ground base or an LNG tanker, LNG2 is stored in an insulated container 1, but a portion of it evaporates (vaporizes) due to external heat input, resulting in gas space 7.
pressure increases. In order to suppress this pressure increase within a certain limit, the vaporized gas is taken out of the container 1 through a pipe 3, heated with a heater 9, and then raised to a sufficient circulation pressure with a compressor or fan 4, and then re-circulated. It is re-liquefied by a liquefier 5 and returned to the container 1 through a pipe line 6.

However, as a practical matter, LNG mainly contains nitrogen gas (GN ₂ ) as an impure component, and because this nitrogen gas has a lower boiling point than LNG, it vaporizes relatively faster than LNG and cannot be reliquefied. LNG will not liquefy at the temperature at which it liquefies. For this reason, in the conventional apparatus as shown in FIG. 1, the nitrogen gas component gradually increases in the reliquefaction circulation systems 3 to 6 and the gas space 7, and if this continues, it becomes impossible to prevent the internal pressure from increasing. Therefore, it is necessary to appropriately dump the vaporized gas out of the system using the relief valve 8.

The present invention was made in order to eliminate the above-mentioned drawbacks, and its purpose is to prevent pressure increase in a liquefied gas storage container.

The vaporized gas extracted from the liquefied gas storage container is
Heating via a warmer, pressurization device, and reliquefaction device,
In a liquefied gas reliquefaction device having a piping system that increases the pressure, reliquefies it, and returns it to the liquefied gas storage container, the liquefied gas is not reliquefied by the pressure increasing device and/or the reliquefaction device upstream of the heater. This can be achieved by inserting an adsorption device that selectively adsorbs impure component gases by using a liquefied gas reliquefaction device.

The device of the present invention described above avoids releasing the vaporized gas of the stored liquefied gas and the vaporized gas of the impure components mixed therein as a mixture, and selectively releases only the vaporized gas of the impure components to the outside of the system. This system is characterized in that an adsorption device filled with an adsorbent that selectively adsorbs vaporized gases of impurity components is added to the reliquefaction system to make it possible.

FIG. 2 is a conceptual diagram of an embodiment of the apparatus of the present invention. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same parts as in FIG.

The vaporized LNG gas is introduced into the adsorption device 10 at a low temperature. Since the adsorption device 10 is filled with an adsorbent (for example, Molecular Sieves (trade name)) that selectively adsorbs nitrogen gas, only nitrogen gas in the vaporized gas is adsorbed and leaves the adsorption device 10. become.

The vaporized gas leaving the adsorption device 10 is returned to the heater 11 (in this example, a heat exchanger that exchanges heat with the return gas (which has become high temperature due to compression) from the pressure booster (compressor 4)). After being cooled (that is, heated by return gas), it enters a compressor 4 where it is increased to the pressure necessary for circulation, cooled with a heat exchanger 11, and further liquefied with a reliquefaction machine 5. At this time, since the nitrogen component in the vaporized gas is very low, most of it is reliquefied. The reliquefied gas and the remaining gas are returned to the container 1 via line 6.

Since the nitrogen gas in the system is removed by the adsorption device 10 in this way, the increase in the nitrogen gas component that causes the pressure increase in the gas space 7 is eliminated, and as in the case of FIG. Pressure increase phenomenon can be prevented.

Note that when the adsorbent in the adsorption device 10 becomes saturated, after closing the valve 12, the adsorbent is regenerated by heating or reducing the pressure by means not shown. The nitrogen gas released at this time is discharged out of the system by opening the valve 13. Alternatively, two or more adsorption devices 10 can be provided in parallel and operated continuously while switching between use and regeneration.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional liquefied gas reliquefaction device.
FIG. 2 is a diagram showing an embodiment of the apparatus of the present invention.

Claims (1)

[Claims] 1 The vaporized gas derived from the liquefied gas storage container is passed through a warmer, a pressure booster, and a reliquefaction device,
In a liquefied gas reliquefaction apparatus having a piping system that heats, pressurizes, reliquefies and returns to the liquefied gas storage container, the liquefied gas is heated, pressurized, reliquefied, and returned to the liquefied gas storage container. A reliquefaction device for liquefied gas is equipped with an adsorption device that selectively adsorbs impure component gases that do not reliquefy.