JPS587878B2 - natural gas supply equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention connects a storage tank and a vaporizer for delivering liquefied natural gas from the storage tank to a natural gas supply pipe through a pump. The present invention relates to a natural gas supply device provided with a conduit with a compressor for delivering the gas to the natural gas supply pipe.

In the above apparatus, conventionally, generally, as shown in FIG. However, since the internal pressure of the natural gas supply pipe 7 is quite high, a compressor 8 with a high pressure discharge capacity of, for example, 20 to 40 atmospheres is required, which is disadvantageous in terms of equipment cost. In addition, since the power efficiency of pressurized gas delivery is low, a large amount of power is required to drive the compressor 8,
It was also disadvantageous in terms of operating costs.

In addition, in order to eliminate the above-mentioned drawbacks, we have developed
As shown in Publication No. 12 (see drawings attached to this specification, FIG. 4), a boil-off gas absorption tower 3 is provided between the pump 2 and the vaporizer 6, and a pipe with the compressor 8 for delivering the boil-off gas is provided. The passage 9 is connected to the absorption tower 3, and the boil-off gas is liquefied and absorbed by the sensible heat of the liquefied natural gas whose pressure has been increased by the pump 2 and the evaporation temperature has increased, thereby lowering the discharge pressure required of the compressor 8. Proposals have been made to reduce the equipment and operating costs required for compressors.

However, in order to provide the liquefied natural gas with enough sensible heat to sufficiently liquefy and absorb the boil-off gas through simple gas-liquid contact in the absorption tower 3, it is necessary to significantly increase the pressure of the liquefied natural gas itself using the pump 2. In order to supply the boil-off gas to the downstream side of the pump 2, the pressure of the boil-off gas must be increased above the discharge pressure of the pump 2, and therefore,
In view of the above-mentioned conventional circumstances, an object of the present invention is to reduce the discharge pressure of the compressor 8 with low power efficiency, which is still insufficient in terms of reducing equipment costs and operating costs. In order to liquefy and absorb natural gas, the discharge pressure of the boil-off gas pumping compressor, which has low power efficiency, is significantly reduced, significantly reducing the equipment cost required for the compressor, and greatly increasing the power efficiency of the entire device. It is an object of the present invention to provide a natural gas supply device which is highly economical and has improved performance and is extremely advantageous in terms of operating costs.

Next, embodiments of the present invention will be described in detail based on illustrative drawings.

As shown in FIG. 1, there is a primary pump 2 for sending liquefied natural gas into a liquefied natural gas storage tank 1, an ejector 3 for the primary pump 2, and a secondary pump 4 for the ejector 3.
A precooler 5 is connected to the secondary pump 4, and a vaporizer 6 is connected to the precooler 5, and the liquefied natural gas from the tank 1 is gasified by the vaporizer 6 and sent to the natural gas supply pipe I. It is structured as follows.

A compressor 8 for pumping the boil-off gas generated in the tank 1 is provided, and the precooler 5 and ejector 3 are connected to the compressor 8 in that order through a pipe 9, and By supplying the boil-off gas to the ejector 3 in a sufficiently cooled state in the precooler 5 by utilizing the sensible heat of the liquefied natural gas whose pressure has been sufficiently increased to the delivery pressure and the evaporation temperature has been raised, the ejector 3 is kept in a relatively low pressure state. The boil-off gas is liquefied and absorbed into the liquefied natural gas from the primary pump 2 by its cooling effect.

Next, data for the case where 1 part by weight of boil-off gas (BOG) (at -100°C) is absorbed into 4 parts by weight of liquefied natural gas (LNG) is shown in Japanese Patent Application Laid-Open No. 48-76112 (No. Table 1 and Figure 5 show a comparison with Figure 4).

The symbols AK in Table 1 and FIG. 5 correspond to the symbols AK in FIGS. 1 and 4, and indicate each state point in the path of both devices.

In the case of the device shown in Figure 4, the amount of heat required for liquefying the boil-off gas between K and E is completely replenished by the sensible heat of the liquefied natural gas between C and E. In order to maintain the liquefied state in
Liquefied natural gas between latm and 14.6
Therefore, the boil-off gas discharge pressure of the compressor 8 is also required to be 14.6 atm.

On the other hand, in the case of the apparatus shown in FIG. 1 of the present invention, the boil-off gas is converted to 1 by using the liquid sensible heat between F and G of the liquefied natural gas whose pressure has been increased to 40 atm by the secondary pump 4. By cooling from the state to the J state, the sensible heat of the liquefied natural gas between B and D, which is required to liquefy the boil-off gas between J and D, can be reduced.
Liquefied natural gas between A and B from latm to 7.8
It is sufficient to increase the pressure to 7.8 atm, and therefore the boil-off gas discharge pressure of the compressor 8 can be reduced to 7.8 atm.
The power of the compressor 8 can be reduced to about 2/3 compared to the device shown in the figure.

On the other hand, when comparing the power to raise the pressure of gas and the power to raise the pressure of liquid, gas generally requires 50 to 100 times more power than liquid to raise the same pressure.

Therefore, by further reducing the boil-off gas discharge pressure of the compressor 8, the power of the entire apparatus can be reduced.

Incidentally, instead of the ejector 3, for example, a premix nozzle (for example, the one disclosed in JP-A-49-48557) may be used.
, a bubble column, a spray column, etc. can be used, and these are collectively referred to as a gas-liquid contactor 3.

In addition, if the boil-off gas cannot be liquefied sufficiently in the gas-liquid contactor 3, as shown in FIG.
By providing a gas-liquid separator 10 between the pump and the secondary pump 4 to return unliquefied boil-off gas to the compressor 8, it is possible to suppress the deterioration in the function of the secondary pump 4 due to the mixing of non-condensable gas. It's fine.

Furthermore, the apparatus of the present invention can be applied not only to liquefied natural gas but also to low-temperature liquefied gases such as liquid oxygen and liquid nitrogen.

In summary, the present invention provides the above-mentioned natural gas supply device, in which a secondary pump is provided between the pump and the vaporizer, a gas-liquid contactor is provided between the pump and the secondary pump, and , a precooler is provided between the secondary pump and the vaporizer, and the boil-off gas from the compressor-equipped pipeline is cooled in the precooler by liquefied natural gas from the secondary pump. It is characterized in that it is connected to the gas-liquid contactor via the precooler so as to be brought into contact with the liquefied natural gas from the pump.

That is, since the boil-off gas is pre-cooled, it is possible to lower the pressure increase of the liquefied natural gas by the primary pump 2, which is necessary for the liquefaction and absorption of the boil-off gas in the gas-liquid contactor 3, and the pre-cooling of the boil-off gas is performed by the secondary pump. 4, even though the discharge pressure of the primary pump 2 is low, it is possible to increase the pressure of the liquefied natural gas for precooling, increase the sensible heat of the liquid, and perform sufficient precooling. As a result, the discharge pressure of the primary pump 2 can be reduced, and as a result of these factors, the discharge pressure of the primary pump 2 can be significantly reduced. The discharge pressure of the compressor 8 can be significantly reduced, the equipment cost required for the compressor 8 can be significantly reduced, and the power efficiency of the entire device can be greatly improved, making it extremely advantageous in terms of operating costs. We have now been able to provide a natural gas supply system that is extremely economical.

[Brief Description of the Drawings] The drawings illustrate an embodiment of the natural gas supply device according to the present invention, FIG. 1 is a flow sheet, FIG. 2 is a flow sheet showing another embodiment, and FIG. 3 is a conventional device. Flow sheet showing the 4th
The figure is a flow sheet showing another conventional device.
FIG. 2 is a state diagram showing the boil-off gas liquefaction process of the conventional device shown in the figure and the device of the present invention shown in FIG. 1; 1...Storage tank, 2...Pump, 3
...-... Gas-liquid contactor, 4... Secondary pump,
5... precooler, 6... vaporizer, 7...
...Natural gas supply pipe, 8...Compressor, 9.
...Pipeline.

Claims (1)

[Claims] 1. A storage tank 1 and a vaporizer 6 that sends liquefied natural gas from there to a natural gas supply pipe 7 are connected via a pump 2, and the boil-off gas generated in the storage tank 1 is connected to the natural gas supply pipe 7. A natural gas supply device including a pipe line 9 with a compressor 8 to be delivered to a pipe 7, the pump 2
A secondary pump 4 is provided between and the vaporizer 6, and
A gas-liquid contactor 3 is provided between the pump 2 and the secondary pump 4.
and a precooler 5 is provided between the secondary pump 4 and the vaporizer 6, and the conduit 9 with the compressor 8 is connected to the boil-off gas from the liquefied natural gas from the secondary pump 4. A natural gas supply device characterized in that the natural gas is connected to the gas-liquid contactor 3 via the precooler 5 so that the liquefied natural gas from the pump 2 is brought into contact with the liquefied natural gas cooled by the precooler 5.