JP2675700B2 - Liquefied natural gas transportation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to liquefied natural gas (LNG).
Regarding the transportation method. More specifically, the present invention relates to a method for energetically and efficiently transporting LNG between LNG storage facilities installed at remote locations.

[0002]

2. Description of the Related Art Natural gas, which is a type of fossil fuel, has a rich reserve, and since methane is the main component, the amount of CO ₂ generated relative to the calorific value of combustion exhaust gas is relatively small and liquefied into LNG. Since impurities are removed in the process, the amount of NOx and SOx, which are pollution sources during combustion, is small,
Demand is increasing as a clean energy source. In particular, the conversion of city gas to natural gas has recently been promoted.
Also in the power industry, in addition to the NOx and SOx, in view of the trend of emission regulations strengthening CO _2, compared with coal or heavy oil and the like CO ₂
There is a tendency toward fuel conversion to natural gas, which produces a relatively small amount.

Natural gas is usually cryogenic (about -1) under normal pressure.
It is transported and stored as LNG (at 62 ° C). Also,
Mass transport of LNG is usually done by LNG carriers. LNG storage bases are located around urban areas where LNG is consumed and around ports near thermal power plants. Therefore, these LNG storage bases are often installed deep inside the bay or inland sea as seen in Tokyo Bay or the Seto Inland Sea. However, due to the dramatic increase in marine traffic in recent years, L
There is a tendency for ships such as NG transport ships carrying dangerous goods to navigate in bays and inland seas, and as a result, it is necessary to reexamine LNG transport methods.

As an alternative transportation method to the in-bay transportation by the LNG transport ship, a landing / storage base from the transport ship is installed at a place far from the storage base in the bay or in the inland sea and facing the open sea or the open sea, and the LNG is boosted. -A method is known in which gas is vaporized and transported in a gas state under pressure by a pipeline to other consumption areas. As described above, when pipeline transportation is carried out in a high-pressure gas state, storage in the consumption area is difficult, and the pipeline itself plays a storage role as well as a transportation role, but sufficient capacity cannot be expected. . Therefore,
There is a problem in that the pressure of the supplied gas also fluctuates greatly due to fluctuations in consumption.

Although LNG has been transported over a very short distance, for example, it has already been carried out by a pipeline between a jetty and a storage tank or between adjacent bases, but it is still transported even if the thermal insulation of the pipeline is extremely increased. The temperature rise is unavoidable. Therefore, the vaporized gas is reliquefied using a compressor and stored in a tank.

[0006] In foreign countries, an idea has been proposed in which a plurality of relay refrigerating facilities are installed on the way by using pipelines to transport several thousand kilometers of LNG, but this transport method is very difficult to operate the relay refrigerating facility. Needing power.

By the way, when LNG is used for city gas or a thermal power plant, it is necessary to heat and vaporize the cryogenic LNG. Seawater is usually used for this heating,
There is no use for cooled seawater, and it is simply thrown into the sea. LNG such as the extremely low temperature that LNG has and the large amount of latent heat that occurs when LNG vaporizes
There is a call for effective use of the cold energy of the LN.
It is limited to the production of liquid oxygen and liquid nitrogen, etc. within a range that is not affected by the temporal fluctuation of G consumption. It is considered that one of the reasons is that there was no suitable use for utilizing a large amount of such latent heat and extremely low temperature in the vicinity thereof.

[0008]

[Problems to be Solved by the Invention]
Currently, NG transportation is rarely adopted in practice, except in the case of very short distances in Japan. on the other hand,
As described above, the cold energy of LNG such as latent heat of vaporization generated when consuming LNG is not effectively used.

As a result of intensive investigations by the present inventors in view of the above-mentioned problems of transportation by LNG pipeline and utilization of cold heat of LNG , the LNG is erased at or near the LNG storage base.
By utilizing LNG's cold heat energy such as latent heat of vaporization of LNG, which is generated when spending, to liquefy air, and by using the obtained liquid air to cool LNG before or after pipeline transportation , it can be transported over long distances by LNG state, thereby completing the <br/> seen out Shi present invention that these problems can be solved together.

That is, according to the present invention, in a method of transporting liquefied natural gas by a pipeline, liquefied natural gas before transportation or liquefied natural gas after transportation is consumed.
A method for transporting liquefied natural gas, characterized in that the liquefied natural gas is cooled by liquid air produced by using cold energy generated during cooling.

[0011]

FIG. 1 shows one embodiment of the method for transporting LNG according to the present invention. In the figure, only the main equipment is shown and the auxiliary equipment is omitted.

In FIG. 1, 1 is a delivery terminal LNG tank, 2 is a pressure pump, 3 is a transportation pipeline, 4 is a heat exchanger for cooling, 5 is a liquid air supply line which is manufactured in a separate process (not shown), and 6 Is a receiving terminal LNG tank.

LNG is stored in the LNG tank 1 at the delivery base under atmospheric pressure at about -162 ° C. This is pressurized by the pressure pump 2 and transported to the receiving terminal by the pipeline 3. The pressurization takes into account the temperature rise during transportation by the transportation pipeline, and is adjusted so that LNG does not vaporize. For example, if the temperature rise during transportation is about 20 ° C,
Pressurization of about 5 ata is sufficient.

The pipeline is LNG due to heat input during transportation.
In order to prevent the temperature rise as much as possible, it is preferable to adopt a material and structure having excellent heat insulating properties. As an example, it is preferable that a double tube structure is used, LNG is circulated in the innermost tube, a heat insulating material such as pearlite is filled between the inner tube and the outer tube, and further vacuum is applied.

At the LNG receiving terminal, the LNG transported by the heat exchanger 4 is stored at a temperature below the atmospheric pressure storable temperature (about It is cooled to −162 ° C. and stored in tank 6.

FIG. 2 shows another embodiment of the method for transporting LNG according to the present invention. FIG. 2 shows a mode that can be adopted in the delivery base when LNG cold energy used for producing liquid air described below can be used. In this aspect, the LNG before transportation is preliminarily cooled using liquid air so that the temperature of the LNG after transportation becomes equal to or lower than the storable temperature (about -162 ° C) at normal pressure in anticipation of the temperature increase during transportation. Keep it. Alternatively, liquid air cooling as shown in FIG. 1 or 2 may be performed at both the LNG sending terminal and the receiving terminal.

The liquid air used here consumes LNG.
It is manufactured in a separate process by using the LNG cold energy such as latent heat of vaporization that occurs during the process. In another step, the cold energy is used to cool the air and then compressed, or the compressed air is used as the cold energy of LNG .
There are to produce liquid air by cooling. The method for producing liquid air by compression and cooling may be a known method. When liquid air is produced, by cooling the air with the cooling energy of LNG, the liquid air can be produced with half or less power as compared with the case where LNG is not used for cooling. Since liquid air is a lower temperature source (boiling point: about -190 ° C) than the atmospheric pressure storage temperature of LNG, it is possible to cool LNG that has been heated during transportation to below the storage temperature again, or to store LNG in advance at the storage temperature before transportation. Cool down and send out,
It is also possible to allow it to be received below the storage temperature without being recooled after transportation. Alternatively, as described above, it may be cooled with liquid air before and after transportation, if necessary.

In the present invention, L before and after transporting liquid air
It is used for cooling NG, but it is produced by separating it from liquid air, such as liquid oxygen (boiling point -183 ° C) and liquid nitrogen (boiling point -19).
5.8 ° C.) may be used instead of liquid air. Such an aspect is also included in the cooling of LNG with liquid air according to the present invention.

[0019]

EXAMPLE The heat balance when transporting LNG by a pipeline according to the present invention is shown below. (1) Basis of calculation (LNG transport pipeline structure, heat insulation) Inner pipe diameter: 300 mm Outer pipe diameter: 500 mm Gap between outer and inner pipes: Filler: Perlite Vacuum degree: 3 × 10 ^-2 mmHg Heat conduction Rate (λ): 3 × 10 ⁻³ Kcal / m · H · ° C. Heat input q per 1 m of pipeline (temperature difference from outside air is 1
80 ° C., heat transfer cross-section is logarithmic average): q = 15.3 Kcal / m · H (flow rate of LNG) Flow rate of LNG: 1/5 m / s Flow rate of LNG: 381.7 m ³ / H (physical properties of LNG) ) Specific gravity: 0.475 T / m ³ Specific heat: 0.76 Kcal / Kg · ° C (electric energy required for producing liquid air by using LNG cold heat) About 0.38 KW / Kg liquid air (does not use LNG cold energy) Case: About 0.8KW / Kg) (Physical properties of liquid air) Heat of vaporization: 49.06Kcal / Kg

(2) In the case of FIG. 1 Pressurization by the pressurizing pump 2 at the delivery station: 4.6 at LNG delivery temperature: -162 ° C. LNG arrival temperature: -140 ° C. (transportation distance 32.7 K)
m) Cooling storage temperature after arrival: -162 ° C Cooling liquid air usage (using heat of vaporization of liquid air): 1
Converted electric energy required to cool LNG after transportation of 0.2 T / H LNG: Approximately 10.2 KW / m ³ LNG (when LNG cold energy is not used: Approximately 21.4 KW / m ³ LNG)

(3) In the case of FIG. 2 Pressurization by the pressurizing pump 2 at the delivery station: 4.6 ata LNG delivery temperature (cooling with liquid air): -180 ° C. Liquid air usage for cooling (heat of vaporization of liquid air) use):
Arrival temperature of 9.2T / H LNG: -162 ° C (transportation distance 29.6K
m) Cooled storage temperature after arrival: -162 ° C Converted electric energy required for LNG cooling before LNG transportation: Approx. 9.2 KW / m ³ LNG (If LNG cooling energy is not used: Approx. 19.3 KW / m ³ LNG)

[0022]

As described above, the method of the present invention is adopted,
Consume LNG at or near the LNG storage base
LNG pipes can be liquefied by using the cold energy of LNG such as latent heat of vaporization of LNG that is generated at the time of liquefaction and cooling the LNG before or after transportation using the obtained liquid air. It has become possible to carry out transportation by line at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a method for transporting LNG according to the present invention.

FIG. 2 is an explanatory view showing another embodiment of the LNG transport method according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-17300 (JP, A) JP-A-52-143540 (JP, A) JP-A-59-180270 (JP, A) JP-A-53- 33771 (JP, A)

Claims (1)

(57) [Claims] 1. A method for transporting liquefied natural gas by a pipeline, wherein liquefied natural gas before transportation or liquefied natural gas after transportation is used by using cold heat energy generated when liquefied natural gas is consumed. A method for transporting liquefied natural gas, which comprises cooling with liquid air produced by the method.