JPS586120B2 - Method for preventing rollover of low temperature liquefied gas tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technology belongs to a technology for preventing rollover caused by a layering phenomenon of heavy low-temperature liquefied gas and light low-temperature liquefied gas in a storage tank of low-temperature liquefied gas such as LNG by stirring.

Therefore, this invention solves the problem of rollover caused by stratification of low-temperature liquefied gas such as LNG in a tank due to density differences, by making the density uniform by stirring the stored low-temperature liquefied gas itself. This technology relates to rollover prevention technology, in particular, self-agitation and mixing by suctioning and circulating the upper layer liquid into the lower layer via a suction pipe attached to a float using a receiving pipe and a discharging pipe installed in the tank. The present invention relates to a rollover prevention method for a low-temperature liquefied gas tank.

As is well known, various problems actually occur when storage tanks for low-temperature liquefied gases such as LNG are recently constructed and operated.

One of them is the so-called rollover problem, and various types of L
When operating by receiving low-temperature liquefied gas such as NG, the component ratio of the received LNG and the residual LNG in the tank is different, so a so-called stratification phenomenon occurs due to the difference in density.

Generally, heavy LNG is placed in the lower layer and light LNG is placed in the upper layer.
When the fuel cell is operated, the density of the upper light LNG increases through the evaporation process, and the density gradually becomes balanced.

However, the heavy LNG in the lower layer has a huge amount of accumulated energy due to latent energy and heat input during transportation and storage, and before and after the above density equilibrium state, it suddenly releases evaporated gas equal to the accumulated energy. A so-called rollover occurs, which cannot be treated by a normal evaporative gas treatment mechanism, and as a result, the internal pressure of the tank becomes excessive, resulting in a dangerous situation.

To deal with this problem, it has been found that it is effective to provide stirring action to prevent the layering phenomenon by creating a homogeneous density, but mechanical means such as a mixer method are not effective. The disadvantage is that it is extremely difficult to drive and operate in low-temperature liquids.

The purpose of this invention is to solve the technical problem of preventing rollover of low-temperature liquefied gas tanks based on the above-mentioned prior art, and to prevent rollover by circulating and mixing the stored liquid without mechanically forced stirring. The present invention aims to provide an excellent rollover prevention method for low-temperature liquefied gas tanks that is useful in the field of low-temperature liquefied gas utilization in the resource industry.

The structure of the present invention in accordance with the above-mentioned purpose is to use a dispensing pump to suck in light low-temperature liquefied gas near the liquid surface through a suction pipe, send it out through a dispensing pipe, pass through a bypass pipe, and then liquefy heavy low-temperature gas at the bottom of the tank using a receiving pipe. The gas liquid is discharged below the lower layer of the liquid, and as a result, the light, low-temperature liquefied gas liquid in the upper part, which has a lower density, naturally rises through the heavier, lower-temperature liquefied gas liquid with a higher density due to its buoyancy, making the density uniform over the entire area and forming a layer. The gist is that technical measures have been taken to prevent the phenomenon from occurring and prevent rollover.

Next, an embodiment of the present invention that achieves the above object will be described below with reference to the drawings.

1 is a low-temperature liquefied gas tank, which is underground.
A frame 3 with a dome roof 2 is built in the ground 4, and an inner tank 5 is provided via a cold insulating material 6. A hanging deck 8 is connected to the dome roof 2 by suspension rods 7, 7... It is suspended.

Further, a submerged pump 9 for discharging is immersed and fixed in the inner bottom of the inner tank 5, and a discharging pipe 10 is connected to the submerged pump 9, and is passed through the dome roof 2 to the next stage treatment facility. It has been extended to

On the other hand, at the inner bottom of the inner tank 5, a receiving pipe 12 having a discharge nozzle 11 penetrates through the dome roof 2 and is connected to the previous stage receiving facility.

Guide wires 13 and 13 are stretched between the bottom surface 5' of the inner layer 5 and the dome roof 2, and a float 15 that is loosely inserted into the guide wires 13 and 13 and floated on the LNG 14 is provided. , suction pipes 18, 18, . has been done.

Further, a bypass line 21 is interposed and connected to the discharge pipe 10 and the receiving pipe 12 via switching valves 19 and 20.

In the low-temperature liquefied gas tank 1 having the above configuration, when heavy LNG is received from the receiving pipe 12, the stratification phenomenon as described above is likely to occur due to the density difference between it and the upper light LNG. By switching the switching valve 19.20 through a control mechanism (not shown), the bypass line 21 is connected to the receiving and receiving pipe 10.12 to create a closed system, and when the submerged pump 9 is operated, the suction attached to the float 15 is Light LNG is sucked from the port 16, and the swivel joint 17.17.
..., a suction pipe 18, a discharge pipe 10 from the submerged pump 9K via a suction pipe 18, a switching valve 1
9. It is ejected from the discharge nozzle 11 to the bottom heavy LNG via the bypass line 21, the switching valve 20, and the receiving pipe 11, and is stirred by the buoyancy effect due to the density difference between the light LNG and heavy LNG.

As this circulation process is repeated, the inside of the tank gradually becomes lighter L.
NG and heavy LNG are stirred and mixed to make the density uniform, and as a result, no stratification phenomenon occurs, and therefore no rollover phenomenon occurs.

The generated steam is then processed in a predetermined manner via a gas collection pipe (not shown).

When the density uniformization is completed, the switching valves 19 and 20 are returned to the receiving and discharging line, contrary to the above, and the density is uniformized from the suction port 16 of the float 15 by the operation of the submerged pump 9. Connect LNG to swivel joints 17, 17..., suction pipes 18, 18,
...is sucked in and sent to the next stage of processing through the discharge pipe 10.

The liquid level rises and falls due to receiving and discharging the LNG 14, which is sucked by the float 15 moving up and down along the guide wire 13.13, and the suction vitrees 18, 18... is absorbed.

Incidentally, it goes without saying that the embodiments of the present invention are not limited to the above embodiments, and various embodiments are possible.

As described above, according to the present invention, in a rollover prevention method by circulating and stirring a stored liquid in a tank of low-temperature liquefied gas such as LNG, the upper layer of low-temperature liquefied gas is sucked through a submerged pump, a discharge pipe, and a receiving pipe. By discharging it to the bottom, the light low-temperature liquefied gas in the tank can be sucked and discharged into the heavy low-temperature liquefied gas at the bottom. The fluidity allows the upper and lower layers to be stirred and mixed, thus homogenizing the density over time, resulting in
The stratification phenomenon is prevented, and as long as the occurrence of the rollover is also prevented, an excellent effect is achieved.

Furthermore, since a submerged pump for dispensing, a dispensing pipe, and a receiving pipe are used for circulating the stored liquid, there is an advantage that the configuration of the device is simplified accordingly.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention and are overall schematic explanatory views. 1...tank, 14...low temperature liquefied gas, 10...
Dispensing pipe, 12... receiving pipe.

Claims (1)

[Claims] 1. A method for preventing rollover by imparting a density-uniforming stirring action to the inside of the low-temperature liquefied gas when a stratification phenomenon occurs between the heavy low-temperature liquefied gas and the light low-temperature liquefied gas in the tank. The upper light liquefied gas liquid is sucked from near the low temperature liquefied gas liquid level through a payout pump provided near the inner bottom, and is spouted into the heavy liquefied gas liquid through a receiving pipe also provided at the inner bottom for circulation. , characterized in that the heavy low-temperature liquefied gas and the light low-temperature liquefied gas are mixed and stirred to have a uniform density by allowing the upper light liquefied gas liquid to naturally rise through the density difference between the lower heavy liquefied gas liquid. A method to prevent rollover of low-temperature liquefied gas tanks.