JPH05280696A - Method and apparatus for liquefying and gasifying town gas - Google Patents

Abstract

PURPOSE:To smooth the operational situation of a required compressor and miniaturize equipment in sending out liquefied natural gas with high pressure. CONSTITUTION:In cooling and refrigerating equipment for obtaining liquefied natural gas stored in a tank and reduced in pressure by a pressure reducing valve 19, a coldness and heat accumulating agent in a coldness and heat accumulating means is always cooled by an overcooling heat exchanger 10 and heat exchangers 23, 27 for the coldness and heat accumulating agent. To liquefy the gasified liquefied natural gas, the gas is cooled by the latent heat and sensible heat of the coldness and heat accumulating agent and further cooled by the overcooling heat exchanger 10 to be liquefied and stored in a tank. When the demand for town gas is great, the liquefied natural gas is boosted by a pump and heated by the coldness and heat accumulating agent so that the gas is sent out with high pressure. Thus, the gas can be sent out in the great demand with pressure higher than that received for liquefacation in the small demand of the town gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to liquefied natural gas (abbreviated as L).
NG), and a method and apparatus for liquefying and vaporizing city gas or the like containing it as a main component.

[0002]

2. Description of the Related Art Conventionally, an increase in demand for city gas has been dealt with by adding a vaporizer for liquefied natural gas and laying a high-pressure pipe. The demand for city gas is highest around 5 pm to 9 pm, and at midnight the amount of city gas used is small, so the operation status of the carburetor is smoothed,
It is desired to reduce the size of the equipment and smooth the transportation amount of the high-pressure conduit so that the installation of the high-pressure conduit can be suppressed.

Conventionally, vaporized liquefied natural gas is stored in a gas holder, and when the demand for city gas is large as described above, the vaporized liquefied natural gas is discharged from the gas holder to operate the liquefied natural gas vaporizer. And we are trying to smooth the operating status of the conduit.

[0004]

In such a prior art, since the gas holder is used, there is a problem that the structure becomes large. Also, the desired pressure, for example 1.5-2.
5 kg / cm at which not only the so-called medium pressure line B ² G, it is desirable to deliver the city gas to medium pressure line A or 10 kg / cm ² G or more high-pressure line is 4~7kg / cm ² G ..

It is an object of the present invention to provide a method and a device for liquefying and vaporizing city gas (natural gas) which can be liquefied and vaporized with a miniaturized structure. ..

[0006]

According to the present invention, the cold storage heat agent is constantly cooled and the cold storage heat agent is cooled by a cold and refrigeration facility obtained by decompressing liquefied natural gas stored in a tank. When the vaporized liquefied natural gas is liquefied by liquefying the vaporized liquefied natural gas, the vaporized liquefied natural gas is constantly pressurized and sent out by the compressor, and the vaporized liquefied natural gas is cooled by the latent heat and sensible heat of the cold heat storage agent. When cooled by heat, the cooled gas is further cooled by the cold and refrigeration equipment and stored in the tank, and the liquefied natural gas stored in the tank is vaporized,
This is a method for liquefying / vaporizing city gas (natural gas), which comprises heating the liquefied natural gas in the tank by a pump, heating the liquefied natural gas with a regenerator, and delivering the gas at high pressure.

Further, according to the present invention, a cold heat storage means for storing a cold heat storage agent and supplying vaporized liquefied natural gas, a tank for storing the liquefied natural gas, and a pressure reducing valve for decompressing the liquefied natural gas from the tank are provided. A heat exchanger for supercooling, which is interposed between the cold heat storage means and the tank, for supercooling heat exchange of liquefied natural gas from the cold heat storage means or from the tank with the liquefied natural gas from the pressure reducing valve; A heat exchanger for cold storage heat agent that cools the cold storage heat agent by liquefied natural gas from the heat exchanger for cooling, and a compressor that pressurizes and delivers vaporized liquefied natural gas from the heat exchanger for cold storage heat agent, A refrigeration facility that is provided in association with the supercooling heat exchanger and the heat exchanger for cold storage heat agent, and cools the cold storage agent from the cold storage heat means or the liquefied natural gas from the tank, and the heat exchanger for supercooling Liquefied natural gas from Liquefaction and vaporization of city gas (natural gas), which includes an on-off valve that leads to the tank, and a pump that boosts the liquefied natural gas from the tank and sends it to the supercooling heat exchanger only when vaporizing. It is a device.

[0008]

According to the present invention, the cold storage obtained by decompressing the liquefied natural gas stored in the tank by the decompression valve, and the compression type refrigeration equipment using nitrogen gas or the like as the heat medium are used for the cold heat storage means. To cool the cold storage heat agent at all times, for example, at night when the demand for city gas is small, in order to liquefy the vaporized liquefied natural gas that is the city gas received from the high-pressure pipe, the liquefied liquefied natural gas to be liquefied, It is cooled by the latent heat and sensible heat of the cold storage agent in which the cold heat is stored, and then further cooled by the cold storage and the refrigeration equipment to be liquefied and stored in the tank.
In the evening when the demand for city gas delivery increased, in order to vaporize the liquefied natural gas stored in the tank, the liquefied natural gas in the tank was boosted by a pump,
The heat of cold storage is used to heat the product and it is sent out at a high pressure, and the pressure of the liquefied natural gas is increased by this pump, so the structure is made smaller than when sending the liquefied liquefied natural gas by the compressor. In addition, it is possible to deliver vaporized liquefied natural gas at high pressure as described above.

Liquefied natural gas from the tank is reduced by the pressure reducing valve 19
Is constantly decompressed, and in the supercooling heat exchanger, the liquefied natural gas to be liquefied from the cold heat storage means is supercooled and liquefied, and the liquefied natural gas to be vaporized from the tank is supercooled to cool the heat storage means. It makes it possible to store cold in the cold storage heat agent, and after the liquefied natural gas from this pressure reducing valve passes through the supercooling heat exchanger, cools the cold storage heat agent in the cold heat storage agent heat exchanger, and then , Boosted by the compressor and delivered constantly. By using the compressor as described above and the pump for increasing the pressure of the liquefied natural gas in the tank as described above, the gas can be delivered at a pressure higher than the pressure of the city gas received from the high-pressure conduit or the like. Although pumping liquefied natural gas from a tank has the advantage of lowering the power consumption of the pump compared to boosting gas, the low temperature cold of the cold storage agent required for liquefaction is insufficient. The lack of cold is supplemented by the cold by the valve and the operation of the refrigeration equipment. In this way, the equipment can be downsized and the power can be reduced as compared with the case where the compressor is configured to send the gas to the high pressure line when the demand for city gas is high.

Since the compressor, the refrigerating equipment, and the pressure reducing valve are constantly operating, the operation status of the device of the present invention can be smoothed, and the structure can be downsized. It becomes possible to store cold for liquefaction of.

[0011]

1 to 3 are overall system diagrams of one embodiment of the present invention, of which FIG. 1 shows the gasified liquefied natural gas, which is city gas, at night when the demand for city gas is low, For example, a state when liquefied from 11:00 pm to 7:00 am is shown, and FIG. 2 shows a state where cold is stored in the cold heat storage agent during the daytime, for example, 7:00 am to 5:00 pm, and FIG.
Evening with high demand for city gas, for example, 5 pm to 1 pm
The state at the time of vaporization of liquefied natural gas at 1 o'clock is shown respectively. In FIGS. 1 to 3, the phantom line portions indicate portions that are not used during liquefaction, cold storage, and liquefaction, respectively. In FIG. 1, when the city gas, which is the vaporized liquefied natural gas from the high-pressure conduit 1, is to be liquefied, the liquefied natural gas is supplied from the on-off valve V1 at about 11 kg / cm ² G through the conduit 2
To 20 ° C. in the heat exchanger 3 by using cooling water CW or the like, and is led to the upper portion of the heat transfer pipe 5 of the cold heat storage means 4 via the pipe 6. This cold storage means 4 is a container 7
The cold heat storage agent 8 is stored therein, and the heat transfer tube 5 is stored in the cold heat storage agent 8. The heat transfer tube 5 extends vertically, and liquefied natural gas of, for example, −120 ° C. from the lower part of the heat transfer tube 5 is introduced from the pipe 9 to the heat transfer tube 11 of the supercooling heat exchanger 10 and is supercooled. , About -127 ℃, pipeline 12
9 kg / cm ² G is decompressed by the pressure reducing valve 14 to, for example, 7 kg / cm ² G from the on-off valve V2 via the pipe 15 to the upper part of the LNG tank 16,
Guided and stored. Liquefied natural gas in the tank 16 is
It is -127 degreeC.

Liquefied natural gas is delivered from a pipe line 17 in the lower part of the tank 16, and flows from the on-off valve V3 via a pipe line 18 to
The pressure is reduced to, for example, 5 kg / cm ² G by the pressure reducing valve 19, the liquefied natural gas is -133 ° C., and the reduced pressure liquefied natural gas is supplied from the pipe 20 to the heat transfer pipe 21 of the supercooling heat exchanger 10. To cool the liquefied natural gas in the heat transfer tube 11, and from the conduit 22 to the heat transfer tube 24 of the heat exchanger 23 for cold storage agent, thus cooling the cold storage heat agent flowing in the heat transfer tube 25, Then, the liquefied natural gas from the heat transfer pipe 24 at -95 ° C is guided from the pipe line 26 to the heat transfer pipe 28 of the warmer 27 which is another heat exchanger for the regenerator, and thus from the pipe line 29, for example. Liquefied natural gas at 5 ° C. and 4 kg / cm ² G is supplied to the compressor 30 and compressed, for example, 1
Compressed liquefied natural gas at 00 ° C is sent from conduit 31 to conduit 3
2 and the on-off valve V5, is introduced into the pipeline 2, and is supplied with the vaporized liquefied natural gas from the high-pressure conduit 1 to the heat exchanger 3 using cooling water as described above to be liquefied. ..

The container 7 of the cold heat storage means 4 is provided with inlets at intervals from top to bottom, and opening / closing valves 33a to 33c (generally indicated by reference numeral 33) to the coolant pump P1. The regenerator thus pumped out is guided to the heat transfer pipe 25 of the heat exchanger 23 for regenerator, cooled as described above, and supplied from the pipe 34 to the bottom of the container 7. In this way, the cold storage heat agent 8 is circulated in the container 7 to promote convection, and the cold obtained in the cold storage heat agent heat exchanger 23 is stored. The cold storage heat agent 8 generates convection in the container 7 to improve the heat transfer efficiency with the heat transfer tube 5, and the cold storage heat agent is agitated, so that the cold storage heat agent is likely to be in a sherbet shape. A pipe 35 is connected to the upper part of the tank 7 of the cold heat storage means 4 so that the cold heat storage agent is pumped by the pump P.
2 and is led from the pipe 36 to the heat transfer pipe 37 of the warmer 27 at, for example, 10 ° C., where the cold storage heat agent is cooled to, for example, −90 ° C., and is taken from the pipe 38 to the container 7
It is supplied inside and circulated. In this way the tank 16
The liquefied natural gas stored in is stored in the heat exchangers 23 and 27 using the cold obtained by decompressing the open / close valve V3 by the decompression valve 19 to cool the regenerator 8 of the regenerator 4. Then, the cold is stored and the pressure is increased by the compressor 30.

A refrigerating facility 39 is provided in association with the supercooling heat exchanger 10 and the cold storage heat exchanger 23. This refrigeration equipment 39 uses nitrogen as a heat medium and uses a compressor 40.
Is introduced into the heat transfer pipe 43 of the main heat exchanger 42 through the heat exchanger 41 using cooling water, and the temperature is adjusted to about −100 ° C., and adiabatic expansion is performed by the expander 44, and −130 from the pipe 45. Nitrogen gas at 3 ° C./3 kg / cm ² G is guided to the heat transfer tube 46 of the heat exchanger 10 for supercooling, whereby the liquefied natural gas in the heat transfer tube 11 is supercooled. Heat transfer tube 46
From the pipe 47 is supplied to the heat transfer pipe 48 of the heat exchanger 23 for cold storage heat agent at about -125 ° C. from the pipe 47.
The cold regenerator in 5 is cooled to, for example, −105 ° C., and is led from the pipe 49 to the heat transfer pipe 50 of the main heat exchanger 42 and then to the compressor 40. Such a compression type refrigeration equipment 39
The continuous operation is continuously performed, whereby cold is stored in the cold heat storage agent of the cold heat storage means 4 and the configuration can be downsized. Table 1 shows the operation states of FIG. 1 and FIGS. 2 and 3 described below. ON of the on-off valve indicates open, and OFF indicates close.

[0015]

[Table 1]

Referring to FIG. 2, during the daytime when the demand for city gas is not so high, the vaporized gas of the liquefied natural gas in the tank 16 is compressed from the pipeline 51 through the on-off valve V6 using the compressor 30. , Further the heat exchanger 3 and the pipe 2, the on-off valve V
1 to the high-pressure conduit 1. The regenerator 8 in the regenerator 4 is cooled to about -100 to -130 ° C at its bottom.

Referring to FIG. 3, in the evening when the demand for city gas is high, the liquefied natural gas in the tank 16 is pumped from the pipeline 17 through the on-off valve V3 and the pipeline 52 to the pump P3, for example, about 15 pumps.
Liquefied natural gas is pressurized to kg / cm ² G and the on-off valve V4
Through the pipe 12 to the heat transfer pipe 11 of the supercooling heat exchanger 10 at −125 ° C., the temperature is set to −130 ° C., and the lower part of the heat transfer pipe 5 of the cold heat storage means 4 is supplied from the pipe 9 In this way, the cold storage heat agent 8 heats up the temperature to -20 ° C. near the upper part of the heat transfer tube 5, and the temperature from the conduit 6 to the normal temperature via the heat exchanger 3 and the opening / closing valve V1 from the conduit 2 is changed. It is then delivered to the high-pressure conduit 1. Thus, it is possible to deliver the liquefied natural gas by vaporizing it in FIG. 3 at a pressure higher than the pressure of the city gas from the high-pressure conduit 1 received for liquefaction in FIG. 1 described above. The compressor 30, the refrigeration equipment 39, and the pressure reducing valve 19 are always operating in each state of FIGS.

The cold heat storage agent 8 of the cold heat storage means 4 can store cold heat in a relatively small amount by mixing ethanol and methanol in a weight ratio of 89.5 to 80 / 10.5 to 20. ..

FIG. 4 shows a phase diagram (melting point) of the ethanol / methanol mixed system of the cold storage heat agent 8. In order to liquefy the liquefied natural gas, the cold storage agent 8 needs to be lowered to about -125 ° C or lower, and for this purpose, the weight ratio of ethanol / methanol is selected as described above. Lines 71 and 7 in FIG.
As shown in 2, by changing the ethanol / methanol weight fraction, freezing, sherbet state,
It changes to a sleet state and reference numeral 73 indicates a eutectic point. In order to keep the cold storage agent 8 in a sherbet state and to bring the temperature to about -125 ° C as described above, the ethanol / methanol weight ratio is selected as described above. In this FIG. 4, when the weight ratio of ethanol / methanol is set to the weight fraction R1 of ethanol, at a temperature of −125 ° C.,
There is an advantage that the weight fraction R2 of ethanol is frozen against the weight fraction R1 of ethanol, and the amount of ice frozen is relatively large. In this way, a cold storage agent having a melting point of about −120 ° C. or lower is realized.

[0020]

As described above, according to the present invention, cold obtained by decompressing liquefied natural gas stored in a tank,
In addition, in order to liquefy the vaporized liquefied natural gas at night when the demand for city gas is small, the latent heat and the latent heat of the cold storage heat agent and In order to vaporize the liquefied natural gas stored in the tank in the evening when there is a large demand for gas delivery, the gas that has been vaporized by heat is cooled and then cooled and chilled by refrigeration equipment to be liquefied and stored in the tank. ,
After the pressure of the liquefied natural gas in the tank is increased by the pump, it can be heated by the cold storage heat agent and sent out at a high pressure, whereby the pump can be downsized, and the compressor and the refrigeration equipment, and the pressure reducing valve 19 It is possible to reduce the size of the equipment of the device by smoothing the operating status of the equipment, while keeping the operation continuously.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing a state during liquefaction according to an embodiment of the present invention.

FIG. 2 is an overall system diagram showing a state during cold storage of the embodiment shown in FIG.

FIG. 3 is an overall system diagram showing a state at the time of vaporization of the embodiment shown in FIGS. 1 and 2.

FIG. 4 is a phase diagram of an ethanol / methanol mixed system of the cold storage agent 8.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure conduit pipe 3 Heat exchanger using cooling water 4 Cooling heat storage means 5 Heat transfer tube 7 Container 8 Cold storage heat agent 10 Supercooling heat exchanger 16 Tank 19 Pressure reducing valve 23 Cold storage heat agent heat exchanger 27 Heater 30 Compression Machine 39 Refrigeration equipment 40 Compressor 44 Expander V1-V6 Open / close valve

Front page continuation (72) Inventor Katsumi Oka 4-1-2, Hiranocho, Chuo-ku, Osaka, Osaka Gas Co., Ltd. (72) Eiji Nakanishi 4-1-2, Hiranocho, Chuo-ku, Osaka Osaka Gas Co., Ltd. In the company

Claims (2)

[Claims] 1. A cold storage obtained by decompressing liquefied natural gas stored in a tank, and a refrigerating facility constantly cool the cold storage heat agent, and vaporize the liquefied natural gas after cooling the cold storage heat agent. When the liquefied vaporized liquefied natural gas is liquefied by constantly boosting it with a compressor and cooling it, the vaporized liquefied natural gas is cooled by the latent heat and sensible heat of the cold heat storage agent in which cold heat is stored, and cooled. When the gas is further cooled by the cold and refrigeration equipment and stored in the tank, and the liquefied natural gas stored in the tank is vaporized,
A method for liquefying / vaporizing city gas, characterized in that liquefied natural gas in the tank is pressurized by a pump, heated by a cold heat storage agent, and then delivered at high pressure. 2. A cold storage heat means for storing a cold storage heat agent and supplying vaporized liquefied natural gas, a tank for storing the liquefied natural gas, a pressure reducing valve for reducing the pressure of the liquefied natural gas from the tank, and a cold storage heat A heat exchanger for supercooling, which is interposed between the heat storage means and the tank to exchange liquefied natural gas from the cold heat storage means or from the tank with the liquefied natural gas from the pressure reducing valve. A heat exchanger for cold storage heat agent that cools the cold storage heat agent by liquefied natural gas from the exchanger, a compressor that pressurizes and sends out the liquefied liquefied natural gas from the heat exchanger for cold storage heat agent, and a supercooling Refrigeration equipment installed in association with the heat exchanger and the heat exchanger for cold storage heat agent to cool the cold storage heat agent of the cold storage heat means and the liquefied natural gas from the tank, and liquefaction from the supercooling heat exchanger. Open natural gas to the tank only when it is liquefied Off valve, the liquefied natural gas from the tank, liquefaction and vaporization apparatus city gas, characterized in that it comprises a pump for delivering steps up only when vaporized heat exchanger for supercooling.