JP2001201041A - City gas supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of equipment required for the boil off gas treatment of the LPG of a city gas supply system. SOLUTION: The boil off gas generated from an LPG tank 12 is mixed with the low temperature boil off gas generated from an LNG tank 11 by a mixer 20, and the most of the gas is re-liquefied by cooling. By cooling to -130 deg.C or lower, impurity in LPG is coagulated and can be removed by filtering with a filter 21. Mixture is separated into gas and liquid by a gas-liquid separator 22, the gas is compressed by an LNG-BOG compressor 16 and given the final adjustment of the calorie mixing with petroleum gas vaporized by an LPG carburetor 17, and supplied in the city. The liquid separated by the gas- liquid separator 22 is mixed with the LNG by a mixer 29 and heat vaporized by the LNG carburetor 15 provided with a liquid-liquid heat regulator, and supplied in the city. As the impurity is removed, the cost of equipment for the prevention of the coagulation of the impurity can be reduced in the LNG carburetor 15 provided with the liquid-liquid heat regulator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a combustion calorie obtained by mixing liquefied petroleum gas (hereinafter sometimes abbreviated as "LPG") with liquefied natural gas (hereinafter sometimes abbreviated as "LNG"). The present invention relates to a city gas supply device that adjusts the supply of gas and supplies it as city gas.

[0002]

2. Description of the Related Art FIG. 2 shows a schematic configuration of a conventional city gas supply device. LNG tank 1 stores liquefied natural gas which is a main raw material of city gas. Liquefied natural gas has a low temperature of about −160 ° C. and a pressure of about 0.12 MPa (about 20 MPa).
It is stored under low pressure conditions (gauge pressure of 00 mm H ₂ O). LPG tank 2 for city gas
The oil and gas supplied from are mixed. LPG tank 2
In LPG, LPG is stored at a low temperature of about −38 ° C. under low pressure conditions of about 0.12 MPa. L stored in LNG tank 1
NG is delivered by the LNG pump 3. The LPG stored in the LPG tank 2 is sent out by the LPG pump 4. The LNG and LPG delivered by the LNG pump 3 and the LPG pump 4 are mixed by an LNG vaporizer 5 with liquid-liquid heat control, heated and vaporized, and supplied as underground as city gas.

[0003] LNG tank 1 for storing low-temperature liquefied gas
In the LPG tank 2 and the LPG tank 2, the stored liquefied gas is vaporized by heat entering from the outside, and boil-off gas (hereinafter sometimes abbreviated as “BOG”) is generated. If the boil-off gas is retained in the LNG tank 1 or the LPG tank 2, the pressure inside the LNG tank 1 or the LPG tank 2 increases, and a large strength is required. Thus, it is necessary to prevent the pressure inside the LNG tank 1 and the LPG tank 2 from becoming excessive.

With respect to the boil-off gas generated from the LNG tank 1, an LNG-BOG compressor 6 is provided,
The pressure is increased to a predetermined pressure, mixed with the petroleum gas vaporized by the LPG vaporizer 7, adjusted for the amount of combustion heat, and supplied to the city as city gas. The boil-off gas generated from the LPG tank 2 is supplied to a dedicated LPG-BOG compressor 8
And heat is sent to the heat exchanger 9 in a state of high temperature and high pressure, exchanges heat with LNG in the heat exchanger 9, cools and reliquefies, and discharges together with LPG from the LPG tank 2.

[0005]

In the conventional city gas supply apparatus as shown in FIG. 2, boil-off gas generated in a low-temperature LPG tank 2 is pressurized by a dedicated LPG-BOG compressor 8 and then heated and pressurized. The boil-off gas is cooled and reliquefied in the heat exchanger 9 and discharged, so that a dedicated compressor and heat exchanger are required. For this reason, the capital investment and running cost of the city gas supply device increase, and the city gas production cost also increases.

The LPG stored in the LPG tank 2
There is also a trace amount of impurities such as alcohol content, and when it is mixed with LNG and vaporized by the LNG vaporizer 5 with liquid-liquid heat control, it is cooled by LNG and solidifies impurities such as alcohol content. , LNG with liquid-liquid heat control
There is a possibility that a heat transfer tube or the like in the vaporizer 5 may be clogged. For this reason, the LNG vaporizer 5 with the liquid-liquid thermal control needs to be provided with a heat transfer panel for preventing the solidification of impurities so that the temperature does not become lower than about −130 ° C. at which the solidification of the impurities occurs. Would.

[0007] It is an object of the present invention to provide a city gas supply apparatus capable of reducing equipment costs associated with the treatment of boil-off gas generated during storage of liquefied petroleum gas in the city gas supply apparatus.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a city gas supply apparatus for storing liquefied natural gas and liquefied petroleum gas, mixing natural gas and petroleum gas to adjust the amount of combustion heat, and supplying the gas as city gas. The LPG tank for storing liquefied petroleum gas under predetermined low-temperature and low-pressure conditions, the LNG tank for storing liquefied natural gas under predetermined low-temperature and low-pressure conditions, and the boil-off gas generated in the LPG tank,
Mix with the boil-off gas generated in the NG tank,
A mixer for reliquefying the boil-off gas of liquefied petroleum gas.

According to the present invention, liquefied petroleum gas stored in the LPG tank under predetermined low-temperature and low-pressure conditions and liquefied natural gas stored in the LNG tank under predetermined low-temperature and low-pressure conditions are mixed, and the amount of combustion heat is reduced. It is regulated and supplied as city gas. The boil-off gas generated in the LPG tank is mixed with the boil-off gas generated in the LNG tank by a mixer. The boil-off gas generated from the LNG tank has a lower temperature than the boil-off gas generated from the LPG tank, and the boil-off gas generated from the LPG tank is cooled and reliquefied. Since the boil-off gas from the LPG tank is re-liquefied with the boil-off gas from the LNG tank, it is not necessary to use a dedicated compressor or heat exchanger for re-liquefaction of the boil-off gas, and the equipment cost can be reduced.

If the boil-off gas from the LPG tank and the boil-off gas from the LNG tank are mixed by a Venturi-type mixer, the mixing can be performed quickly and efficiently.

The present invention is further characterized by further comprising a gas-liquid separator for separating a reliquefied liquid and a gas not reliquefied from the mixture obtained by the mixer.

According to the present invention, a liquid reliquefied by a gas-liquid separator and a gas not reliquefied can be separated from the mixture mixed by the mixer. The reliquefied liquid contains a large amount of liquefied petroleum gas components, and the gas that has not been reliquefied contains the components of natural gas and the remaining components of petroleum gas.

[0013] The gas separated by the gas-liquid separator is composed of natural gas components and petroleum gas components.
The pressure can be increased to a predetermined pressure by a compressor and sent to a demand destination, and the amount of combustion heat for use as city gas can be easily adjusted.

Further, the present invention is characterized by further comprising a recovery means for returning the liquid separated by the gas-liquid separator to the LPG tank.

According to the present invention, the liquid separated by the gas-liquid separator contains a large amount of liquefied petroleum gas, and can be returned to the LPG tank by the recovery means and reused.

Further, in the present invention, the ratio of the boil-off gas from the LPG tank mixed with the mixer to the boil-off gas from the LNG tank is adjusted to a predetermined value, and the mixture by the mixer is cooled to a predetermined temperature or lower. And a filter for removing solidified impurities.

According to the present invention, LPG mixed in a mixer
The ratio between the boil-off gas from the tank and the boil-off gas from the LNG tank is adjusted to a predetermined value, and the mixture mixed in the mixer is cooled to a predetermined temperature or lower to remove solidified impurities by a filter. When the temperature is increased and vaporized by an open rack type heat exchanger with liquid-liquid control after the removal of impurities by the above method, measures for preventing the removal of impurities become unnecessary, and the equipment cost can be reduced.

Further, the present invention is characterized in that the liquid from which impurities have been removed by the filter is sent to an LNG vaporizer for mixing with liquefied natural gas in a liquid state and adjusting the amount of combustion heat.

According to the present invention, the liquid from which impurities have been removed by the filter is sent to an LNG vaporizer for mixing with natural gas in a liquid state and adjusting the heat of combustion.
In the NG vaporizer, it is not necessary to additionally provide a heat transfer panel or the like for preventing solidification of impurities, so that an increase in equipment cost can be suppressed.

Since the liquid from which impurities have been removed by the filter contains a component of petroleum gas and has a higher calorific value than natural gas, the liquid is returned to the LNG tank to increase the calorific value of LNG and the boil-off gas is recovered without waste. It can be used effectively.

[0021]

FIG. 1 shows a schematic configuration of a city gas supply device 10 as one embodiment of the present invention. The city gas supply device 10 includes an LNG tank 11, an LPG tank 12, an LNG pump 13, an LPG pump 14, an LNG vaporizer 15 with liquid-liquid heat control, an LNG-BOG compressor 16, an LPG vaporizer 17, a mixer 20, and a filter 2.
1, gas-liquid separator 22, gas pipe 23, liquid pipe 2
4, including valves 25, 26, 27, 28 and mixer 29. In the LNG tank 11, at a low temperature of about -160 ° C,
LNG is stored under low pressure conditions of about 0.12 MPa.
The LPG tank 12 has a low temperature of about −38 ° C. and about 0.1
Under low pressure conditions of 2 MPa, LPG is stored. LN
G generates boil-off gas containing methane (CH ₄ ) as a main component. LPG is propane (CH ₃ CH ₂ CH ₃ )
A boil-off gas mainly containing butane (CH ₃ (CH ₂ ) ₂ CH ₃ ) is generated.

The LNG in the LNG tank 11 is sent by a LNG pump 13 to an LNG vaporizer 15 with liquid-liquid heat control. The LPG in the LPG tank 12 is sent to the LNG vaporizer 15 with liquid-liquid heat control by the LPG pump 14. LNG vaporizer 15 with liquid-liquid heat control is an Open Rack Vacuum.
It has a structure abbreviated as ORV from a porizer, and raises the temperature of the mixed low-temperature liquefied gas to vaporize it. The conventional open rack type LNG vaporizer with liquid-liquid heat control has an extra heat transfer panel for the purpose of raising the temperature of LNG to about -130 ° C or more.

The boil-off gas generated from the LPG tank 12 is mixed with the boil-off gas generated from the LNG tank 11 by a mixer 20. The boil-off gas generated from the LPG tank 12 is generated at about −38 ° C., for example, containing propane as a main component at a rate of 0.5 t / h. The boil-off gas from the LNG tank 11 mixed therewith is
At about -160 ° C, methane is used as a main component and used at a rate of 20 t / h. By the mixing, almost all of the boil-off gas generated from the LPG tank 12 is cooled to about -150 ° C and reliquefied.

A good mixing property can be obtained by using a Venturi type mixer or the like as the mixer 20. A filter 21 is provided downstream of the mixer 20. In the liquid mixture cooled to about -150 ° C., impurities such as alcohol are coagulated, and thus can be easily removed by the filter 21. A gas-liquid separator 22 is provided downstream of the filter 21. The gas-liquid separator 22 includes:
The mixture is gas-liquid separated into a gas component and a liquid component. The gas mainly composed of methane that has not been reliquefied is approximately -150 ° C.
And separated into gas pipes 23. The reliquefied propane-based liquid is also at about −150 ° C., and is separated into the liquid pipe 24. The gas separated into the gas pipe 23 is pressurized by the LNG-BOG compressor 16 and mixed with the oil gas vaporized by the LPG vaporizer 17 to be calorie-adjusted and supplied to a demand destination such as a consumer in the city. Is done. The LNG-BOG compressor 16 and the LPG vaporizer 17 are the LNG-BOG compressor 6 and the LPG vaporizer 7 used in the conventional city gas supply device shown in FIG.
It is a facility equivalent to each. The liquid containing propane as a main component recovered by the gas-liquid separator 22 becomes about 0.49 t / h, and is returned to the LPG tank 12 via the valve 25 and stored. At this time, the valve 26 is also opened. By closing the valve 26 and opening the valve 27, it is possible to store in the LNG tank 11.

The liquid separated into the liquid pipe 24 is supplied to the valve 2
By closing 5 and opening valve 28, it can also be sent to mixer 29. In the mixer 29, the mixture is mixed with LNG sent from the LNG tank 11 by the LNG pump 13, and the mixture is heated and vaporized in the LNG vaporizer 15 with liquid-liquid heat control. In the present embodiment, the boil-off gas from the LPG tank 12 is mixed with the boil-off gas from the LNG tank 11 in the mixer 20, cooled, re-liquefied, and then the filter 21 is used to remove impurities. LNG vaporizer 1
In 5, it is not necessary to provide an extra heat transfer panel to prevent solidification of impurities, and the equipment cost can be reduced as compared with the conventional LNG vaporizer 5 with liquid-liquid heat control shown in FIG. 2. Also,
The filter 21 can be provided not only on the downstream side of the mixer 20 but also on the liquid pipe 24 side of the gas-liquid separator 22.

In this embodiment, the LNG-BOG compressor 6 of the conventional city gas supply device is the same as the LNG-BOG compressor 6.
The use of the G compressor 16 eliminates the need for the dedicated LPG-BOG compressor 8 as shown in FIG. 2, so that the capital investment cost can be significantly reduced. Further, as shown in FIG. 2, the boil-off gas from the LPG tank 12 is
After the pressure is increased by the PG-BOG compressor 8, the heat exchanger 9 required for cooling is also unnecessary, so that the capital investment cost can be further reduced.

Further, in the mixer 20, the LPG tank 1
Since the boil-off gas from the LNG tank 11 is cooled using the boil-off gas from the LNG tank 11 as a cold heat source, the boil-off gas from the LNG tank 11 which is constantly generated is effectively used. The boil-off gas from the tank 12 can be stably processed.

The mixer 20 mixes the boil-off gas from the LNG tank 11 with the boil-off gas from the LPG tank 12 at an appropriate ratio, so that the combustion heat of the mixed boil-off gas can be reduced to about 3 per m ³ in a standard state.
9900 to 41800 kJ (9540 to 10000 kc
al). For this reason, 45 m / m ³ in the standard condition that is ultimately required for city gas
When it is necessary to adjust the heat of combustion to 980 kJ (11000 kcal), the amount of LPG gasified can be reduced. Generally, in order to vaporize LPG in the LPG vaporizer 17, high-temperature and high-pressure steam is used, so that the running cost required to generate this steam can be reduced. Further, the reliability of the final heat quantity adjustment is improved.

When the reliquefied boil-off gas from the LPG tank 12 is returned to the LPG tank 12, the boil-off gas can be returned in a supercooled state, so that the amount of boil-off gas generated in the LPG tank 12 can be suppressed. it can.

The temperature of the fluid mixed by the mixer 20 is set to about-
If the temperature is adjusted to 130 ° C., impurities such as alcohol contained in the LPG solidify, and can be removed by a simple filter 21. For this reason, when the LNG vaporizer 15 with liquid-liquid thermal control has an ORV structure, it is possible to reduce capital investment costs related to the heat transfer panel for preventing impurity solidification. After the impurities are removed by the filter 21, the reliquefied liquid can be returned to the LNG tank 11. Thus, the amount of combustion heat of LNG stored in the LNG tank 11 can be easily increased.

[0031]

As described above, according to the present invention, the boil-off gas from the LPG tank storing the liquefied petroleum gas is mixed with the boil-off gas from the LNG tank by the mixer to be re-liquefied. There is no need to use a dedicated compressor or heat exchanger for gas treatment, and equipment costs can be reduced.

According to the present invention, the liquid and the gas can be separated from the boil-off gas mixed by the mixer in the gas-liquid separator.

Further, according to the present invention, the liquid separated by the gas-liquid separator can be recovered by returning to the LPG tank.

Further, according to the present invention, by adjusting the ratio of the boil-off gas to be mixed by the mixer, the mixture can be cooled to a predetermined temperature or less to solidify impurities and to efficiently remove the impurities.

According to the present invention, the liquid from which impurities have been removed by the filter is mixed with liquefied natural gas in a liquid state and sent to the LNG vaporizer for adjusting the amount of heat of combustion. There is no need to take measures against coagulation, and equipment costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a piping diagram showing a schematic configuration of a city gas supply device 10 as one embodiment of the present invention.

FIG. 2 is a piping diagram showing a schematic configuration of a conventional city gas supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 City gas supply apparatus 11 LNG tank 12 LPG tank 15 LNG vaporizer with liquid-liquid heat control 16 LNG-BOG compressor 17 LPG vaporizer 20 Mixer 21 Filter 22 Gas-liquid separator 29 Mixer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K068 AA02 AB04 AB12 AB14 AB16 AB29 4D047 AA10 AB08 BA08 BA09 BB09 CA03 DA01 DA17 4H060 AA02 BB34 CC11 GG08

Claims (5)

[Claims] 1. A city gas supply device for storing liquefied natural gas and liquefied petroleum gas, adjusting the heat of combustion by mixing natural gas and petroleum gas, and supplying the gas as city gas. L stored under low temperature and low pressure conditions
PG tank and L for storing liquefied natural gas under predetermined low temperature and low pressure conditions
A city gas supply device comprising: an NG tank; and a mixer that mixes boil-off gas generated in the LPG tank with boil-off gas generated in the LNG tank to re-liquefy the boil-off gas of liquefied petroleum gas. . 2. The city gas supply according to claim 1, further comprising a gas-liquid separator for separating a reliquefied liquid and a gas not reliquefied from the mixture obtained by the mixer. apparatus. 3. The city gas supply device according to claim 2, further comprising a recovery unit for returning the liquid separated by the gas-liquid separator to the LPG tank. 4. The ratio of the boil-off gas from the LPG tank and the boil-off gas from the LNG tank to be mixed by the mixer is adjusted to a predetermined value, and the mixture obtained by the mixer is adjusted to a temperature below a predetermined temperature. The city gas supply device according to claim 2, further comprising a filter that removes a cooled and solidified impurity. 5. The city according to claim 4, wherein the liquid from which impurities have been removed by the filter is sent to an LNG vaporizer for adjusting the amount of combustion heat by mixing the liquid with liquefied natural gas in a liquid state. Gas supply device.