JPH07198282A - City gas reliquefying, storing and conveying apparatus - Google Patents

Abstract

PURPOSE:To effectively utilize pressure energy of city gas in the case of reliquefying. CONSTITUTION:City gas supplied from a high-pressure main line 1 is heated by a heater 101, pressure-reduced by an expansion turbine 102, and fed to an intermediate-pressure A line 4. Power recovered by the turbine 102 drives a nitrogen refrigerating facility 90. Cold obtained by the facility 90 is utilized for cooling reliqeuefaction of city gas containing LNG as a main ingredient or cooling of cold storage agent. The cooled agent is stored in a cold storage vessel 30, and used for cooling in the case of reliquefying the gas. Liquefied city gas in an LNG tank 10 is vaporized and fed when a demand is much. Cold in the case of vaporizing is stored in the agent in the vessel 30. Exhaust heat from the facility 90 is utilized for warm heat for heating the heater 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a city gas reliquefaction storage / delivery device for reliquefying and storing when the demand for city gas is low, and vaporizing and delivering it when the demand for city gas is high.

[0002]

2. Description of the Related Art Conventionally, it has been known that the demand for city gas has a large daily fluctuation. The peak demand is in the time zone from 5 pm to 9 pm, and a large amount of city gas is used for bath heating and cooking in ordinary households. The amount of city gas used is low at midnight. For this reason, city gas is stored in a gas holder, etc., at midnight when demand is low, and when the demand for city gas is high, the city gas is discharged from the gas holder, etc. It is smoothed.

Since the gas holder stores city gas in a gas state, it requires a large capacity facility. Therefore, a technique has been proposed in which city gas is reliquefied and can be stored in a small volume. For example, Japanese Patent Application Laid-Open No. 3-236589 proposes a technique of utilizing a cold heat storage agent to collect and store cold heat required for liquefaction of city gas during vaporization of city gas. In this prior art, 10-40 kg /
from the high pressure trunk lines city gas is supplied cm ² G, it is reduced to the city gas supply pressure called medium pressure A of 7 kg / cm ² G through the governor.

[0004]

When decompressing city gas with a governor, for example, if decompressing by 1 kg / cm ² , the temperature of the city gas decreases by about 0.6 ° C. Therefore, 30k
When the high pressure gas of g / cm ² G is reduced to 7 kg / cm ² G, there is a temperature drop of about 15 ° C. Since the temperature of the city gas is higher than 0 ° C, it is necessary to generate hot water in the upstream of the governor by, for example, a gas-fired boiler, and heat the high-pressure city gas to around 30 ° C by the hot water tank. This boiler heating system goes against the downsizing of equipment. When an expansion turbine is installed adjacent to the governor and power is generated using the recovered power, for example, 30 kg / cm ² G of city gas with a flow rate of 100,000 Nm ³ per hour is used.
From 2kg to 7kg / cm ² G, about 2800k
The power of W can be recovered. When the entire amount of this recovered power cannot be used at the city gas supply station, it is necessary to send it back to the power company for reverse flow.

An object of the present invention is to provide a city gas reliquefaction storage / delivery device which can be effectively utilized for the pressure energy of city gas.

[0006]

SUMMARY OF THE INVENTION The present invention is an expansion turbine for expanding city gas to reduce its pressure from a primary pressure to a secondary pressure,
The nitrogen refrigeration means driven by the recovery power from the expansion turbine, the heating means for heating the city gas drawn into the expansion turbine by using the exhaust heat from the nitrogen refrigeration means, and the reliquefied city gas Liquefied gas tank for storing, cold storage tank for storing cold heat storage agent, cold heat from nitrogen refrigeration means,
Alternatively, the cold heat from the cold storage agent stored in the cold storage tank is used to cool the city gas for reliquefaction, and the cold storage agent is cooled by the cold heat when vaporizing and delivering the liquefied city gas or the cold heat from the nitrogen refrigeration means. A city gas reliquefaction storage / delivery device comprising heat exchange means for cooling.

Further, the heating means of the present invention is characterized by including a hot water tank for storing the heat generated by the nitrogen freezing means.

[0008]

According to the present invention, the pressure energy for expanding the city gas to reduce the pressure from the primary pressure to the secondary pressure is recovered by the expansion turbine. The nitrogen refrigeration means driven by the power recovered by the expansion turbine cools the city gas for reliquefaction or cools the regenerator, and heats the city gas drawn into the expansion turbine by exhaust heat. The pressure energy of city gas is effectively used for heating during depressurization and cooling for reliquefaction, and can also be stored as cold heat by the cold storage heat agent.

Further, according to the present invention, since the heat generated by the nitrogen freezing means is stored in the hot water tank, even if the freezing means is stopped, the hot water stored in the hot water tank is used. The heating of the city gas sucked into the expansion turbine can be continued.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of the main part of one embodiment of the present invention. From the high-pressure main line 1, for example, city gas containing liquefied natural gas (hereinafter sometimes abbreviated as “LNG”) as a main component is supplied at a pressure of 30 kg / cm ² G and a flow rate of 100,000 Nm ³ / h. It From the intermediate pressure A line 4, which is the secondary side of the governor 2, the pressure is reduced to 7 kg / cm ² G and the gas is delivered. When a heater 101 is inserted in the high-pressure main line 1 and the heated city gas is decompressed by the expansion turbine 102 and sent to the medium-pressure A line 4, 1 hour from 8:00 am to 10:00 pm
About 40,000 kWh can be recovered in 4 hours.
When the nitrogen refrigeration equipment 90 is driven by the recovered power, the cold heat generated is a natural gas realized by the boil-off gas (sometimes abbreviated as “BOG”) liquefier 11 and the liquefaction / vaporization heat exchanger 20. The city gas can be cooled by the vaporizer / liquefier, reliquefied, and stored in the LNG tank 10. Exhaust heat from the nitrogen refrigeration equipment 90 is 2.
45 × 10 ⁶ kcal / h, which is supplied to the heater 101 as 60 ° C. hot water. The liquefied city gas stored in the LNG tank 10 is vaporized again according to the demand and sent to the medium pressure A line 4. At the time of vaporization, cold heat is recovered from the natural gas vaporizer / liquefier 20 in the cold heat storage agent. The cooled regenerator is stored in the regenerator 30 and used for cooling when reliquefying the city gas. Reliquefaction and delivery of city gas can be switched by opening / closing the operation valves 26 and 28.

FIG. 2 shows an overall system diagram of the embodiment shown in FIG. The high-voltage trunk line 1 is generally 10 to 40 kg / cm
² , high pressure city gas is supplied. The main component of city gas is natural gas. The high-pressure city gas is stepped down by the governor 2, passed through the silencer 3, and then supplied from the medium pressure A pipe 4 to the consumer side. In the medium pressure A pipe line 4, the pressure is adjusted to, for example, 7 kg / cm ² .

[0012] In general, the demand for city gas peaks from the evening to the night, and the demand is low at midnight. Since it is uneconomical to match the capacity of gas supply facilities to peak demand, city gas is liquefied and stored when demand is low, and gas is vaporized during peak demand, and silencer 3 to medium pressure A pipeline Add to 4.

When the city gas is liquefied, the city gas flows through the operation valve 28 and the opening / closing valve 29 into the pipeline 22, so that the opening / closing valve 2
9 is opened, and the flow rate is adjusted by the operation valve 28. A safety valve 23 is provided so that the pressure in the conduit 22 does not rise abnormally. The pipe line 22 is connected to the heat transfer pipe 21 of the liquefaction / vaporization heat exchanger 20. The city gas containing natural gas as a main component, which is supplied to the heat exchanger 20 for liquefaction and vaporization, is cooled by the cold nitrogen generated in the nitrogen refrigeration facility 90 described later and the cold heat of the cold storage agent 44, and is liquefied to form the pipeline 16 , 17, and stored as LNG 12 in the LNG tank 10. BO
The low temperature nitrogen is supplied to the G liquefier 11 from the refrigeration equipment,
Cool for BOG liquefaction.

LN stored in the LNG tank 10
G12 is line 13, when the demand for city gas increases.
It is supplied to the pipeline 16 via the on-off valve 14 and the operation valve 15. From this pipe line 16, a pipe line 17 connected to the lower portion of the LNG tank 10 branches via an opening / closing valve 18 and an operation valve 19. However, the on-off valve 18 is the LNG tank 1
It is closed when 0 to LNG 12 are supplied to the conduit 13. The LNG at this time flows into the pipe line 22 via the heat transfer pipe 21 provided in the liquefaction / vaporization heat exchanger 20. In the heat transfer tube 21, the city gas containing liquefied natural gas as the main component is vaporized by the cold storage agent depriving the cold heat. A safety valve 23 is provided to prevent a pressure increase in the conduit 22. Further, it is mixed with city gas from the governor 2 by the silencer 3 via the flow meter 24, the opening / closing valve 25 and the operation valve 26, and the medium pressure A pipe line 4
Is supplied to.

The cold heat for liquefying the city gas using the liquefaction / vaporization heat exchanger 20 is stored in the cold storage container 30 as sensible heat or latent heat of the cold storage agent. In the cold storage container 30, a plurality of inlet / outlet nozzles 31 to 41 are provided at intervals in the vertical direction from the bottom to the top. The cool storage container 30 is formed of a heat insulating material 42, and the cool storage agent 44 is stored in the inner tank 43 thereof. Although the outer tank 45 is in contact with the atmosphere, the heat storage container 30 keeps the cold storage container 30 cool by minimizing the heat transfer. As the cold storage agent 44, for example, ethanol and methanol are mixed and used at a weight ratio of 55:45. The cool storage agent 44 has a temperature distribution in which the density is different depending on the temperature, the upper part has a relatively high temperature, and the lower part has a relatively low temperature.

The inlet / outlet nozzle 31 capable of sucking or ejecting the cold storage agent of the lowest temperature is connected to the heat transfer tube 48 of the regenerator 47 via the pipe line 46. The heat transfer tube 48 is connected to the other one in the regenerator 47 via the circulation pump P1 and the operation valve 49.
It is connected to two heat transfer tubes 50. In the regenerator 47, heat exchange is performed between the heat transfer tube 48 and the heat transfer tube 50. The low temperature regenerator has a large viscosity, and the load on the circulation pump P1 increases. Further, the temperature of the cold storage agent rises due to the operation of the circulation pump P1. In the regenerator 47, heat exchange is performed to raise the temperature of the cold storage agent sucked into the circulation pump P1 and lower the temperature of the discharged cool storage agent.

The inlet / outlet nozzles 32 to 36 are provided with selection valves 51 to 51.
It is connected to the pipeline 56 via 55 respectively. Pipeline 56
The cold storage agent is taken out from the tank via the circulation pump P2 and the operation valve 57, and is returned via the opening / closing valve 58. Such removal or return of the cold storage agent is performed by the conduit 59.
Done through. The lowest temperature regenerator is returned to the conduit 46 via the on-off valve 60.

The entry / exit nozzles 37-40 are selected valves 61-.
It is connected to the pipeline 65 via 64 respectively. Pipeline 65
Takes out the cool storage agent via the circulation pump P3 and the operation valve 66, or returns the cool storage agent via the opening / closing valve 67. Extraction or return of the cold storage agent is performed via a pipe line 68. The uppermost entry / exit nozzle 41 is connected to the conduit 69. From the pipe 69, the cold storage agent is taken out through the circulation pump P4 and the operation valve 70, and returned through the opening / closing valve 71. Extraction or return of the cold storage agent is performed via the pipe line 72.

The lowest temperature cold storage agent is taken out or returned through the flow meter 73 and the pipe line 74. The line 59 for taking out and returning the second coldest regenerator is connected to the line 76 via the flow meter 75. The pipe line 68 for taking out and returning the third coldest regenerator is connected to the pipe line 78 via the flow meter 77. The pipe 72 for taking out and returning the highest temperature regenerator is connected to the pipe 80 via the flowmeter 79. The pipe line 74 is a three-divided heat transfer pipe 81 provided in the liquefaction / vaporization heat exchanger 20,
It is connected to one end of one heat transfer tube 81 of 82 and 83. The conduit 76 is connected to the connection portion between the heat transfer tube 81 and the heat transfer tube 82. The conduit 78 is connected to the connection portion between the heat transfer tube 82 and the heat transfer tube 83. The conduit 80 is connected to one end of the heat transfer tube 83.

The liquefaction / vaporization heat exchanger 20 is formed by a plate fin type heat exchanger and has the above-mentioned heat transfer tubes 21 and 8.
In addition to 1, 82, 83, a heat transfer tube 85 is further formed. Nitrogen gas expanded and cooled by the N ₂ compander 96 is supplied to the heat transfer tube 85 via a pipe line 86. The cold nitrogen gas used to liquefy BOG in the BOG liquefier 11 is returned to the line 87.

The nitrogen refrigeration facility 90 is provided, for example, for cooling the regenerator or for liquefying city gas. The nitrogen refrigeration equipment 90 has N ₂ compressors 91, 97 for performing a refrigeration cycle of nitrogen gas. N ₂ compressor 91
Compresses nitrogen gas to a high pressure (about 9 kg / cm ² G) and supplies it to the N ₂ cooler 92. In the N ₂ cooler 92, the nitrogen gas whose temperature has risen during the compression process is cooled, and the nitrogen gas having a high pressure at room temperature is supplied to the pipe line 84.
It is guided to the heat transfer tube 94 of the N ₂ main heat exchanger 93 therein. N ₂
A heat transfer tube 95 is also provided in the main heat exchanger 93, and a conduit 86 is provided.
The heat transfer tube 94 is relatively cooled and the heat transfer tube 95 is relatively heated by heat exchange with the nitrogen gas after cooling the regenerator or the city gas. The nitrogen gas cooled in the heat transfer tube 94 is expanded and cooled by the N ₂ compander 96 and supplied to the heat transfer tube 85 of the liquefaction vaporizer and the BOG liquefier 11. The nitrogen gas heated by the heat transfer tube 95 is N ₂
The pressure is increased by a compressor 97 axially coupled to the compander 96,
It is supplied to the N ₂ cooler 98. The N ₂ cooler 98 cools the nitrogen whose temperature has risen during the compression process, and the N ₂ compressor 91 further compresses the nitrogen. A safety valve 99 is provided to prevent an increase in pressure in the pipe line 84.

The nitrogen refrigeration facility 90 is further provided with a hot water tank 100. In the hot water tank 100, the N ₂ coolers 92 and 98 are cooled and the water heated by heat exchange is stored as hot water. A heater 101 is provided to heat the city gas supplied from the high-pressure main line 1 using the hot water stored in the hot water tank 100. Heater 1
The city gas heated by 01 is supplied to the expansion turbine 102 provided in parallel with the governor 2. The power that is supplied to the expansion turbine 102 and is recovered when the city gas is depressurized drives the N ₂ compressor 91.

In the nitrogen refrigerating equipment 90, the signs of ~ correspond to the states of nitrogen in ~ of the Mollier diagram shown in FIG. That is, the nitrogen in the above state is compressed by the N ₂ compressor 97 to obtain the state. Between and, N ₂ cooler 9
The nitrogen gas is cooled by 8 and heat energy is taken out as hot water. The nitrogen in the state of is compressed by the N ₂ compressor 91,
To the state of. During the period from to, the nitrogen gas is cooled by the N ₂ cooler 92 and the heat energy is taken out as hot water.
From the end to the end, it is cooled by the N ₂ main heat exchanger 93. From the end to the end, it is cooled when it is expanded under reduced pressure by the N ₂ compander 96. In the state (1), the city gas is cooled to about −140 ° C. by the BOG liquefier 11 to be reliquefied and the liquefaction / vaporization heat exchanger 20 is cooled. The cold heat given to the heat exchanger 20 for liquefaction and vaporization in the state of is also used for cooling the cool storage material 44 of the cool storage container 39. The cold heat that has been cooled and stored is used for cold heat replenishment of city gas reliquefaction at night.

FIG. 4 shows the structure of the main part of still another embodiment of the present invention. The other parts of the configuration are similar to those of the embodiment shown in FIG. It should be noted that the expansion turbine is divided into two stages and the city gas is heated even in the middle. That is, the city gas from the high voltage main line 1 is heated by the heater 101.
It is heated at a and decompressed at the expansion turbine 102a of the first stage. The city gas emitted from the first-stage expansion turbine 102a is heated by the intermediate heater 101b, decompressed by the second-stage expansion turbine 102b, and supplied to the silencer 3.

The hot water in the hot water tank 100 is supplied to the pump 10
3 to remove the N ₂ cooler 92,
The exhaust heat of the nitrogen refrigeration equipment 90 heats up to about 60 ° C. The heated warm water is returned to the upper part of the warm water tank 100. From the vicinity of the upper part of the hot water tank 100, the pump 104
The hot water of about 60 ° C. by the heaters 101a, 101b
Supply to. The hot water cooled by heating the city gas with the heaters 101a and 101b is heated by the hot water tank 10
It is set back to 0. In the hot water tank, the hot water of high temperature is distributed upward so that the hot water of low temperature is distributed downward according to the density difference depending on the temperature of the water. Expansion turbine 102a,
The power recovered by 102b is used to drive the N ₂ compressor 91. The N ₂ compressor 91 can also be driven by the motor 105. Motor 105
Is driven when the cold heat of the cold storage agent stored in the cold storage container 30 or the like is insufficient by using, for example, late-night power. The control of the motor 105, the adjustable valve shown in FIG. Control device 1
In 06, a control program for realizing various operations as described with reference to FIG. 2 is set in advance. In addition, when the pressure of the high-pressure main line 1 is higher or the intermediate pressure is lower, the number of stages of the expansion turbine may be further increased to efficiently recover the pressure energy.

According to each of the above embodiments, city gas can be stored at night when demand is low, for example, at 20,000 Nm ³ / h, and can be delivered up to 200,000 Nm ³ / h at the peak of demand. This makes it possible to easily increase the activity of the gas supply facility.

[0027]

As described above, according to the present invention, the city gas reliquefaction can be made efficient by effectively utilizing the pressure energy of city gas. Since high-pressure city gas can be reliquefied and stored and delivered according to demand, it is possible to manufacture city gas and smooth supply facilities. Further, even when reducing a large pressure difference, the temperature of the city gas can be prevented from lowering and power can be efficiently recovered.

Further, according to the present invention, since the city gas is heated by the hot water stored in the hot water tank, the city gas can be kept heated even when the nitrogen refrigeration means is stopped. it can.

[Brief description of drawings]

FIG. 1 is a simplified system diagram showing a main part of an embodiment of the present invention.

2 is an overall system diagram of the embodiment of FIG.

FIG. 3 is a Mollier diagram for explaining the operation of the nitrogen refrigeration equipment 90 of the embodiment of FIG.

FIG. 4 is a system diagram showing a main part of another embodiment of the present invention.

[Explanation of symbols]

1 High-pressure main line 2 Governor 4 Medium-pressure A line 10 LNG tank 11 BOG liquefier 12 LNG 20 Liquefaction / vaporization heat exchanger 30 Regenerator 90 Nitrogen refrigeration equipment 91,97 N ₂ Compressor 92,98 N ₂ Cooler 100 Hot water tank 101, 101a, 101b Heater 102, 102a, 102b Expansion turbine 105 Motor 106 Control device

Claims (2)

[Claims] 1. An expansion turbine for expanding city gas to reduce its pressure from a primary pressure to a secondary pressure, a nitrogen refrigeration means driven by recovery power from the expansion turbine, and exhaust heat from the nitrogen refrigeration means. A heating means for heating the city gas drawn into the expansion turbine, a liquefied gas tank for storing the reliquefied city gas, a cold storage tank for storing the cold heat storage agent, and a cold heat from the nitrogen refrigeration means, or a cold storage tank. Heat for cooling the city gas for reliquefaction by the cold heat from the cold energy storage agent stored in the tank, and heat for cooling the cold energy storage agent by the cold heat when vaporizing and delivering the liquefied city gas or the cold heat from the nitrogen refrigeration means. A city gas reliquefaction storage / delivery device comprising: an exchange means. 2. The city gas reliquefaction storage / delivery device according to claim 1, wherein the heating means includes a hot water tank for storing the heat generated by the nitrogen refrigeration means.