JPH11325714A - Heat exchange type gas liquefier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchange type gas liquefier which can make gas into liquefied gas stably and with good response, even if there is fluctuation in operating conditions. SOLUTION: This is a heat exchange type of gas liquefier which cools and liquefies gas by exchanging heat with liquefied gas, and this is equipped with a gas compressing pump 8 which compresses the gas, a first valve 16 which supplies the gas coming out of the gas compressive pump to a heat exchanger, a heat exchanger 13 which condenses the gas supplied from the first valve by exchanging heat with the liquefied gas, a liquefied gas drum 14 which reserves the condensed gas, a second valve 17 which injects a part of the gas coming out of the gas compressing pump into the liquefied gas drum, and a third valve 18 which returns the gas within the liquefied gas drum to the line before the gas compressing pump. Then, the flow of gas passing through the second valve 17 is adjusted, and the flow of gas passing through the third valve 18 is adjusted, according to the gas pressure within the liquefied gas drum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a liquefied gas by cooling a gas such as natural gas by heat exchange, and more particularly to an apparatus for producing a liquefied gas such as liquefied natural gas as a refrigerant. The present invention relates to a heat exchange gas liquefaction apparatus for producing a liquefied gas by cooling and condensing a gas.

[0002]

2. Description of the Related Art Liquefied natural gas (LNG) is obtained by liquefying natural gas and has been widely used in recent years as clean energy. Natural gas is liquefied at the producing area, transported in the form of liquefied gas, and stored once near the natural gas consuming area. Liquefied natural gas is stored in a low-temperature storage tank at a liquefied natural gas storage base, and is vaporized according to the demand of a power plant or the like that consumes natural gas (hereinafter referred to as a consumer side) and sent to the consumer side in a gaseous state. . At the storage base,
Part of the stored liquefied natural gas is constantly vaporized by heat input from outside the low-temperature storage tank, and boil-off gas (hereinafter B)
(Called OG) from the cold storage tank. In a conventional storage terminal, BOG is sent to the consumer in a gaseous state.

[0003] Conventional liquefied natural gas (hereinafter referred to as LN)
G) will be described with reference to the drawings. FIG. 3 is a process flow diagram of the storage base. The storage base includes a low-temperature storage tank 1, a primary booster pump 2, a low-pressure flow control valve 3, a low-pressure vaporizer 4, a BOG compression pump 8, a low-pressure gas pressure controller 5, and a low-pressure main valve 6. When the consumer demands a high pressure gas in addition to the low pressure gas, the storage base further includes a secondary booster pump 9, a high pressure vaporizer 10, and a high pressure main valve 11. The low-temperature storage tank 1 stores LNG at a pressure slightly higher than the atmospheric pressure. The primary pressurizing pump 2 discharges LNG from the low-temperature storage tank 1 and pressurizes it. A part of the pressurized LNG is sent to the low-pressure vaporizer 4 through the low-pressure flow control valve 3. The low-pressure vaporizer 4 gasifies the pressurized LNG. The low-pressure main valve 6 is provided on an outlet pipe of the low-pressure vaporizer 4 and serves as a gas sending outlet for sending low-pressure natural gas to the demand side. The low-pressure gas pressure controller 5 measures the pressure of the pipe connecting the low-pressure carburetor 4 and the low-pressure main valve 6, and controls the low-pressure flow control valve 3 so that the outlet pressure of the low-pressure carburetor 3 becomes a predetermined pressure. LNG flowing
Adjust the flow rate. The BOG compression pump 8 compresses the BOG discharged from the low-temperature storage tank 1 into a low-pressure BOG, and joins the low-pressure BOG with the low-pressure natural gas discharged from the low-pressure vaporizer 4. The secondary boosting pump 9 boosts the remainder of the low-pressure LNG boosted by the primary boosting pump to a higher pressure. High pressure vaporizer 10
Gasifies LNG pressurized to a high pressure. The high-pressure main valve is provided in an outlet pipe of the high-pressure vaporizer 10 and serves as a gas sending outlet for sending high-pressure natural gas to a consumer side.

[0004] The operation of the conventional liquefied natural gas storage station process will be described along the flow of natural gas. LNG is
It is stored in the low-temperature storage tank 1. LNG is discharged from the low-pressure storage tank 1 by the primary pressure-boosting pump, and is boosted to a low pressure (for example, 7 kg / cm ² ). Next, LNG:
The flow rate is controlled by the low-pressure flow control valve, sent to the low-pressure carburetor 4, and vaporized into low-pressure natural gas. Natural gas is sent to the consumer side via the low-pressure main valve 6. When the demand side is a power plant, natural gas is burned in a boiler. A part of the low-pressure LNG is further supplied to the secondary booster pump 9.
To a high pressure (for example, 30 kg / cm ² ), and sent to the high-pressure vaporizer 10. High pressure LNG is a high pressure vaporizer 1
It is vaporized by zero and becomes high-pressure natural gas. The high-pressure natural gas is sent to the consuming side via the high-pressure main valve 11. When the demand side is a power plant, high-pressure natural gas is generally burned in a gas turbine. On the other hand, BOG is generated from the cold storage tank 1. The BOG is compressed by the BOG compression pump 8 to become a low-pressure BOG. The low-pressure BOG is combined with the low-pressure natural gas from the low-pressure vaporizer 4.

[0005] Recent liquefied natural gas storage bases are often required to supply both low pressure and high pressure natural gas as described above. On the consumer side, combined gas power generation of boilers and gas turbines is performed. Boilers consume low-pressure natural gas, and gas turbines consume high-pressure natural gas. Since a gas turbine has better thermal efficiency than a boiler, gas turbine power generation is generally used according to base load, and boiler power generation is used according to fluctuating demand. When the overall demand decreases, it may be desirable to stop boiler power generation. However, in the conventional LNG storage base, boiler power generation cannot be completely stopped because BOG generated inevitably needs to be sent to the consumer side. BO generated to completely stop boiler power generation
It is conceivable that G is converted to high-pressure natural gas and supplied for gas turbine power generation. However, a method of directly compressing BOG into high-pressure natural gas is not practical because it requires a large amount of compression energy. Therefore, it is preferable to re-liquefy the low-pressure BOG, raise the pressure to a necessary high pressure, and then vaporize. In order to re-liquefy BOG, there is a method of exchanging heat between LNG and BOG with a heat exchanger to condense BOG. B
The OG is condensed in the heat exchanger to become liquefied natural gas (hereinafter, liquefied BOG). That is, BOG is BOG
After being compressed by the compression pump 8 and pressurized, the LNG discharged from the low-temperature storage tank 1 exchanges heat with the heat exchanger of the gas liquefier to condense and liquefy into liquefied BOG. Liquefied BO
G is then pressurized by a pressurizing pump, merged into LNG exiting the gas liquefier, vaporized, and sent to the consuming side.

At a liquefied natural gas storage station, it is required to maintain the pressure of the natural gas to be sent at a predetermined constant value. BOG liquefaction pressure) is desired to maintain a constant value and not fluctuate. However, LNG
In a gas liquefaction apparatus having a structure in which BOG is merely flowed through a heat exchanger using a gas as a refrigerant, the BOG liquefaction pressure depends on operating conditions such as the amount of BOG and the amount of LNG as a refrigerant, the performance of the heat exchanger, and the like. That is, in a heat exchanger having a fixed heat transfer area and a heat transfer structure, the BOG liquefaction pressure decreases when the BOG amount is smaller than the LNG amount. Conversely, LNG
When the amount of BOG increases as compared to the amount, the BOG liquefaction pressure increases. Therefore, to keep the BOG liquefaction pressure constant, L
It is desirable that the ratio between the NG amount and the BOG amount is constant.
However, the amount of LNG changes sequentially according to a request from the consumer. In addition, the BOG amount sequentially changes according to the ambient temperature of the low-temperature storage tank 1 and the operating conditions. Under such conditions,
In a gas liquefaction apparatus having a structure in which BOG is simply passed through a heat exchanger using LNG as a refrigerant, the BOG liquefaction pressure fluctuates, and the operation of the process is not stable. For example, when the BOG liquefaction pressure decreases, a problem arises in that the boosting pump for increasing the liquefied BOG causes cavitation and trips. When the BOG liquefaction pressure increases, there is no pressure difference between the BOG pressure at the inlet of the heat exchanger and the BOG liquefaction pressure, so that a problem occurs in that BOG does not flow through the heat exchanger.

[0007] A proposal for maintaining the BOG liquefaction pressure constant under such conditions is disclosed in Japanese Patent Application Laid-Open No. 5-118497. FIG. 4 is a process flow diagram of an LNG storage facility equipped with the disclosed gas liquefaction apparatus. That is, while maintaining the liquid level of the liquefied BOG in the BOG flow path inside the plate fin type heat exchanger 13 and exchanging heat between BOG and LNG, the liquid level is adjusted to a predetermined B level.
The BOG liquefaction system discloses that the amount of heat exchange between OG and LNG is controlled. Further, as this control means, the liquefied BOG from the heat exchanger is
4 and dispenses a predetermined amount, and the drum is installed above the heat exchanger, and the BOG liquefaction pressure and liquefied BO
The liquid level is adjusted by controlling the pressure difference from the internal pressure of the G drum 14. The principle of this system is to increase or decrease the heat transfer area of the heat exchanger 13 according to the ratio of the amount of LNG to the amount of BOG,
The point is to keep the OG liquefaction pressure constant. In this system,
If the fluctuation between the LNG amount and the BOG amount is small, B
The OG liquefaction pressure can be kept constant. But,
Since it is a method of indirectly controlling the BOG liquefaction pressure, quick response is difficult, and when the LNG amount or BOG amount changes suddenly, the BOG liquefaction pressure may fluctuate.

[0008] Further, in a storage base capable of simultaneously supplying low-pressure natural gas and high-pressure natural gas, it is required to operate the process in a plurality of control modes according to the demands of consumers. For example, there are a first mode in which two types of natural gas, low pressure and high pressure, are simultaneously supplied, and a second mode, in which only high pressure natural gas is supplied. In general, settings for optimal control of the liquefaction apparatus are different between the first mode and the second mode. For example, in the first mode, L
It is conceivable to adjust the amount of the BOG amount according to the LNG amount so that the ratio between the NG amount and the BOG amount becomes constant. In the second mode, it is conceivable to adjust the amount of liquefied BOG so that the pressure in the BOG pipe becomes constant. Even for such a change in the control mode, the gas liquefier must be operated properly and the BOG liquefaction pressure must be stabilized.

[0009]

As described above, in a gas liquefaction apparatus having a structure in which a gas simply flows through a heat exchanger using a liquefied gas as a refrigerant, the flow rate of the gas fluctuates or the flow rate of the liquefied gas is reduced. Under the condition of fluctuation, the ratio of the flow rate of the gas to the flow rate of the liquefied gas fluctuates, so that there is a problem that the liquefaction pressure of the gas cannot be kept constant. Further, when the flow rate of the gas and the flow rate of the liquefied gas fluctuate rapidly, there is a problem that the gas liquefaction pressure cannot be kept constant in a prompt response. Furthermore, when the control mode of the gas liquefaction apparatus changes, there is a problem that the optimum control conditions fluctuate and it is difficult to keep the liquefaction pressure of the gas constant.

The present invention has been devised in view of the above-mentioned problems, and has been developed in view of the fact that even if the amount of the liquefied gas as the refrigerant or the amount of the gas fluctuates, the heat which can keep the liquefaction pressure of the gas constant. Attempts to provide an exchangeable gas liquefaction device. Also, even when the flow rate of the gas or the flow rate of the liquefied gas fluctuates suddenly,
An object of the present invention is to provide a heat exchange type gas liquefaction apparatus capable of promptly responding and maintaining a constant gas liquefaction pressure. Still another object of the present invention is to provide a heat exchange type gas liquefaction apparatus which can stably control the gas liquefaction apparatus even if the control mode of the gas liquefaction apparatus is changed, and can keep the gas liquefaction pressure constant.

[0011]

In order to achieve the above object, a heat exchange gas liquefaction apparatus according to the present invention is a heat exchange gas liquefaction apparatus for exchanging heat with a liquefied gas, cooling and liquefying the gas, A gas compression pump (8) for compressing the gas;
First to supply the gas discharged from the gas compression pump to the heat exchanger
(16), a heat exchanger (13) for exchanging the gas supplied from the first valve with the liquefied gas by heat exchange, a liquefied gas drum (14) for storing the condensed gas, and a gas compressor. A second valve (17) for injecting a part of the gas discharged from the pump into the liquefied gas drum, and adjusting a gas flow rate through the second valve (17) according to the gas pressure in the liquefied gas drum. I did it.

According to the configuration of the present invention, the gas compression pump (8) compresses the gas to increase the pressure of the gas. First
The valve (16) supplies the gas discharged from the gas compression pump to the heat exchanger and regulates the flow rate of the gas flowing to the heat exchanger. The heat exchanger (13) exchanges heat of the gas supplied from the first valve with a liquefied gas to cool, condense, and convert the gas into a liquefied gas. The liquefied gas drum (14) stores the liquefied gas formed by condensing the gas, and maintains the pressure of the liquefied gas. The second valve (17) injects a portion of the gas from the gas compression pump into the liquefied gas drum and increases the pressure in the liquefied gas drum. Further, the gas flow rate through the second valve (17) can be adjusted in accordance with the gas pressure in the liquefied gas drum to maintain the gas pressure in the liquefied gas drum at a predetermined pressure or higher.

[0013] In order to achieve the above object, a heat exchange gas liquefaction apparatus according to the present invention is a heat exchange gas liquefaction apparatus for exchanging heat with a liquefied gas, cooling and liquefying the gas, and compressing the gas. And a first valve (1) for supplying gas from the gas compression pump to the heat exchanger.
6), a heat exchanger (13) for exchanging the gas supplied from the first valve with the liquefied gas by heat exchange, a liquefied gas drum (14) for storing the condensed gas, and a gas in the liquefied gas drum. Return to the line before the gas compression pump
And the flow rate of gas passing through the third valve (18) is adjusted according to the gas pressure in the liquefied gas drum.

According to the configuration of the present invention, the gas compression pump (8) compresses the gas to increase the pressure of the gas. First
The valve (16) supplies the gas discharged from the gas compression pump to the heat exchanger and regulates the flow rate of the gas flowing to the heat exchanger. The heat exchanger (13) exchanges heat of the gas supplied from the first valve with a liquefied gas to cool, condense, and convert the gas into a liquefied gas. The liquefied gas drum (14) stores the liquefied gas formed by condensing the gas, and maintains the pressure of the liquefied gas. The third valve (18) returns the gas in the liquefied gas drum to a line before the gas compression pump and reduces the pressure in the liquefied gas drum. Further, the gas flow rate through the third valve (18) is adjusted according to the gas pressure in the liquefied gas drum, and the gas pressure in the liquefied gas drum can be maintained at a predetermined pressure or less.

[0015] More preferably, in the heat exchange gas liquefaction apparatus according to the present invention, the gas flow rate through the first valve is adjusted according to the flow rate of the liquefied gas passed through the heat exchanger. With this configuration, the gas flow rate passing through the first valve is adjusted according to the flow rate of the liquefied gas passing through the heat exchanger, and the ratio of the flow rate of the liquefied gas to the flow rate of the gas is maintained at a predetermined value.

More preferably, in the heat exchange gas liquefaction apparatus according to the present invention, the gas flow rate through the first valve is adjusted according to the outlet temperature of the liquefied gas discharged from the heat exchanger. With this configuration, the gas flow rate passing through the first valve is adjusted according to the outlet temperature of the liquefied gas discharged from the heat exchanger, and the outlet temperature of the liquefied gas is set to a predetermined temperature.

More preferably, in the heat exchange type gas liquefaction apparatus according to the present invention, the gas flow rate through the first valve is adjusted according to the gas pressure at the inlet of the first valve. With this configuration, the first valve adjusts the gas flow rate through the first valve according to the gas pressure at the inlet of the first valve, and adjusts the gas pressure inside the pipe connected to the inlet of the first valve. To a predetermined pressure.

More preferably, in the heat exchange type gas liquefaction apparatus according to the present invention, the gas generated from the liquefied gas storage facility may be a B gas.
The liquefied gas was OG, which was discharged from the liquefied gas storage facility and sent to the vaporizer. With this configuration, B generated from the liquefied gas storage facility
The OG is cooled by the liquefied gas discharged from the liquefied gas storage facility and sent to the vaporizer, condensed and converted into a liquefied gas.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, common portions are denoted by the same reference numerals, and redundant description will be omitted.

FIGS. 1 and 2 are process diagrams of a liquefied natural gas storage facility equipped with one heat exchange gas liquefaction apparatus according to an embodiment of the present invention. In this process, the primary booster pump 2
Increases the pressure of LNG discharged from the low-temperature storage tank 1 to a low pressure (for example, 7 kg / cm ² ). A part of the pressurized LNG is supplied to the low-pressure vaporizer 4 with its flow rate adjusted by the low-pressure flow control valve 3. The low-pressure vaporizer 4 vaporizes LNG,
The natural gas is sent to the consumer via the low pressure main valve 6. The remainder of the boosted LNG is supplied to the secondary boosting pump 9.
The secondary boosting pump 9 further increases the pressure of the LNG to a higher pressure (for example, 30 Kg / cm ² ) to make it a high-pressure LNG. The heat exchange gas liquefaction device is supplied with its high pressure LNG. Further, the heat exchange gas liquefaction apparatus is supplied with BOG generated in the low-temperature storage tank 1. The heat exchange type gas liquefier liquefies BOG using high-pressure LNG as a refrigerant. The heat exchange type gas liquefaction apparatus supplies the liquefied BOG to the liquefied BOG boosting pump 15. The liquefied BOG pressurizing pump 15 pressurizes the liquefied BOG, merges with the high-pressure LNG output from the heat exchange type gas liquefier, and supplies it to the high-pressure vaporizer 10.
The high-pressure vaporizer 10 vaporizes the high-pressure LNG and sends high-pressure natural gas to the consuming side via the high-pressure main valve 11.

The heat exchange type gas liquefaction apparatus of this embodiment includes a gas compression pump 8 (hereinafter, referred to as a BOG compression pump), a heat exchanger 13, a liquefied gas drum 14, and a first flow control valve 1.
6, second flow control valve 17, third flow control valve 18, liquefied gas flow controller 21, liquefied gas drum pressure controller 19
And a low-pressure gas pressure controller 5 and a liquefied gas temperature controller 20. The BOG compression pump 8 compresses the BOG discharged from the low-temperature storage tank 1 to a low pressure, merges a part of the BOG with the low-pressure natural gas discharged from the low-pressure vaporizer 4, and further combines the BOG.
The remainder of G is supplied to the first flow control valve 16. The first flow control valve 16 flows BOG to the heat exchanger 14. The first flow control valve 16 synthesizes a gas flow control signal supplied from the liquefied gas flow controller 21 and a liquefied gas temperature control signal supplied from the liquefied gas temperature controller 20 at a predetermined ratio. The flow rate of the BOG is adjusted and flowed according to the control signal. Further, when the low-pressure gas pressure control signal is supplied from the low-pressure gas pressure controller 5, the first flow control valve 16
Adjusts the flow rate according to the lower control flow rate signal of the combined control signal and the low-pressure gas pressure control signal to adjust the BOG
Flow. The heat exchanger 13 uses the supplied high-pressure LNG as a refrigerant, and supplies the BOG supplied from the first flow control valve.
Is cooled and condensed to form a liquefied BOG. The liquefied gas drum 14 stores the liquefied BOG supplied from the heat exchanger 13 and holds the BOG liquefaction pressure inside. Liquefied BOG
The pump 8 discharges the liquefied BOG from the liquefied gas drum 14 and keeps the amount of the liquefied BOG in the liquefied gas drum 14 constant. The second flow control valve 17 converts a part of the BOG coming out of the outlet of the BOG compression pump 8 into a liquefied BOG drum 1.
Inject into 4. The second flow control valve 17 adjusts the flow according to the liquefied gas drum pressure lower limit control signal supplied from the liquefied gas drum pressure controller 19 to flow the BOG.
The third flow control valve 18 is connected to the B in the liquefied BOG drum 14.
Return OG to the line upstream of BOG compression pump 8. The third flow control valve 18 is provided with a liquefied gas drum pressure controller 19.
BOG is flowed by adjusting the flow rate in accordance with the liquefied gas drum upper limit pressure control signal supplied from the control unit. The liquefied gas flow controller 21 detects the liquefied gas flow supplied to the heat exchanger 13 and outputs a gas flow control signal to the first flow control valve 16 so that the ratio of the LNG flow to the BOG flow is BOG is made to flow so as to have a predetermined value. The liquefied gas drum pressure controller 19 detects the pressure in the liquefied gas drum 14 and outputs a liquefied gas drum pressure lower limit control signal to the second flow rate control valve 17 so that the pressure in the liquefied gas drum becomes lower than a predetermined lower limit pressure. Make BOG flow so that it does not drop. Further, the liquefied gas drum pressure controller 19 transmits the liquefied gas drum pressure upper limit control signal to the third flow control valve 18.
And the BOG is made to flow so that the pressure in the liquefied gas drum 14 does not exceed a predetermined upper limit pressure. The liquefied gas temperature controller 20 detects the temperature of LNG coming out of the heat exchanger 13 and outputs a liquefied gas temperature control signal to the first flow control valve 16 so that the LNG temperature becomes a predetermined value. , BOG flow. The low-pressure gas pressure controller 5 detects the gas pressure of the gas line coming out of the low-pressure vaporizer 4 and sends a low-pressure gas pressure control signal via the control signal switch 24 to the first flow control valve 16 and the low-pressure flow rate. It is output to one of the control valves 3 so that BOG flows so that the gas pressure becomes a predetermined pressure. The control signal switch 24 is
By switching the control mode, the supplied low-pressure gas pressure control signal is supplied to one of the low-pressure flow control valve 3 and the first flow control valve 16.

The operation of the same process in a liquefied natural gas storage facility equipped with the gas liquefaction apparatus of the present invention will be described in accordance with gas treatment. First, a process in which both the high-pressure gas and the low-pressure gas are sent to the consumer will be described. FIG. 1 is a process flow in the case of a control mode in which both the high-pressure gas and the low-pressure gas are sent to the consuming side. Low pressure gas pressure controller 5
Is supplied to the low-pressure flow control valve 3 via the signal switch 24. LNG is stored in the low-temperature storage tank 1. LNG is boosted by the primary boosting pump 2 to be low-pressure (for example, 7 Kg / cm ² ) low-pressure LNG. Part of the low-pressure LNG is a low-pressure flow control valve 3
, And is vaporized by the low-pressure vaporizer 4 and sent to the consumer side via the low-pressure main valve 6. At this time, the gas pressure discharged from the low-pressure vaporizer is set to a predetermined pressure (for example, 7 kg / c).
m ² ) so that the low pressure LN through the low pressure flow control valve 3
The flow rate of G is adjusted. The rest of the low pressure LNG is 2 more
The pressure is increased by the next pressure increasing pump 9 and the pressure is increased (for example, 30 kg / c).
m ² ). The high-pressure LNG passes through the heat exchanger 13 of the gas liquefier, is vaporized by the high-pressure vaporizer 10, and is sent to the consumer side 12 via the high-pressure main valve 11. On the other hand, the BOG generated from the low-temperature storage tank 1 is BOG
It is compressed by the OG compression pump 8 and becomes low-pressure BOG.
Since the low-pressure BOG line communicates with the line connecting the low-pressure carburetor 4 and the low-pressure main valve 6, the pressure of the low-pressure BOG becomes equal to the gas pressure discharged from the low-pressure carburetor 4. The low pressure BOG enters the heat exchanger 13 through the first flow control valve 16. The low-pressure BOG is cooled in the heat exchanger 13, condensed, and becomes liquefied BOG. At this time, the flow rate of the low pressure BOG passing through the first flow rate control valve is adjusted, and the high pressure LNG is adjusted.
The ratio of the flow rate of the BOG to the flow rate of the BOG becomes a predetermined value. Further, the flow rate of the low-pressure BOG passing through the first flow rate control valve is adjusted, and the temperature of the high-pressure LNG exiting the heat exchanger 13 becomes a predetermined value. Liquefied BO condensed
G is stored in the liquefied gas drum 14 and the liquefied gas drum 1
The pressure in 4 is maintained at the BOG liquefaction pressure. At this time, the low pressure BOG that has exited the BOG compression pump 8 is put into the liquefied gas drum 14 by the second flow rate control valve 17 in accordance with the liquefied gas drum pressure lower limit control signal, so that the gas pressure inside the liquefied gas drum 14 is predetermined. Does not fall below the lower limit pressure (for example, 6 kg / cm ² ). Further, the third flow control valve 1 is controlled according to the liquefied gas drum pressure upper limit control signal.
8, the gas inside the liquefied gas drum 14 is returned to the BOG line upstream of the BOG compression pump 8, so that the gas pressure inside the liquefied gas drum 14 exceeds a predetermined upper limit pressure (for example, 6.5 kg / cm ² ). No. Therefore, the gas pressure inside the liquefied gas drum 14 is maintained at a pressure between the upper limit pressure and the lower limit pressure. The liquefied BOG stored in the liquefied gas drum 14 is discharged by the liquefied BOG boosting pump 15 while the amount thereof is maintained at a fixed storage amount. The discharged liquefied BOG is pressurized by the liquefied BOG pressurizing pump 15 and has a high pressure (for example, 30 kg).
/ Cm ² ) of liquefied BOG. High pressure liquefied BOG is
It is combined with the high-pressure LNG and supplied to the high-pressure vaporizer 10. The LNG and the liquefied BOG are vaporized by the high-pressure vaporizer 10 and sent to the consuming side 12 via the high-pressure main valve 11.

Next, when only the high-pressure gas is sent to the consuming side,
The process in the case is described. Figure 2 shows only the high-pressure gas consuming side
3 is a process flow in the case where air is supplied. Low pressure gas pressure
The low-pressure gas control signal output from the controller 5 is transmitted to a signal switch 24.
Is supplied to the first flow control valve 16 via
The low pressure flow control valve and the low pressure main valve are closed. LNG
Are stored in the low-temperature storage tank 1. LNG is the first rise
The pressure is increased by the pressure pump 2 and further increased by the secondary pressure pump 9
And a high pressure (for example, 30 kg / cm^Two) LNG
You. High-pressure LNG is a heat exchanger for heat exchange gas liquefaction equipment
13 and is vaporized by the high-pressure vaporizer 10
Air is supplied to the consumer side 12 via the valve 11. On the other hand, low temperature
The BOG generated from the storage tank 1 is a BOG compression pump
8 to form a low pressure BOG. This low pressure BOG
Is a line connecting the low-pressure carburetor 4 and the low-pressure main valve 6.
Communication, so the line pressure is always low pressure BOG
Equal to the pressure of Low pressure B through the first flow control valve 16
The OG enters the heat exchanger 13. Low pressure BOG is a heat exchanger
It cools at 13 and condenses to liquefied BOG. On this occasion,
The flow rate of the low-pressure BOG through the first flow control valve 16 is adjusted.
Between the BOG compression pump 8 and the first flow control valve 16
Line and low-pressure carburetor 4 and low-pressure main valve 6
A predetermined pressure (for example,
7kg / cm ^Two)become. However, the first flow control valve
The maximum value of the flow through the pump is limited, and the LNG flow at high pressure and B
BOG flow such that the ratio of the OG flow becomes a predetermined value
High-pressure LN so as not to exceed the quantity and further out of the heat exchanger
The temperature of G does not exceed a predetermined value. Coagulation
The compressed liquefied BOG is stored in a liquefied gas drum 14.
The pressure in the liquefied gas drum 14 maintains the BOG liquefaction pressure.
Carry. At this time, the low pressure before passing through the first flow control valve 16
When the BOG is in the second state according to the liquefied gas drum pressure lower limit control signal,
Into the liquefied gas drum 14 by the flow control valve 17
The gas pressure inside the liquefied gas drum 14 is
Lower limit pressure (for example, 6 kg / cm^Two)less than
No. Further, the gas inside the liquefied gas drum 14
Third flow rate control according to liquefied gas drum pressure upper limit control signal
The BOG lane upstream of the BOG compression pump 8 by the node valve 18
The gas inside the liquefied gas drum 14
The pressure is a predetermined upper limit pressure (for example, 6.5 kg / c
m^Two). Therefore, the liquefied gas drum 14
The internal gas pressure is maintained at a pressure between the upper and lower pressure limit.
Be held. Liquefied BO stored in the liquefied gas drum 14
G is liquefied BO while its amount is maintained at a constant storage amount.
Discharged by the G boost pump 15. Dispensed liquid
Liquefied BOG is boosted by the liquefied BOG boosting pump 15.
High pressure (for example, 30 kg / cm^Two) Liquefied BOG
Become. High pressure liquefied BOG is combined with high pressure LNG
And supplied to the high-pressure vaporizer 10. LNG and liquefied BOG
Is vaporized by the high pressure vaporizer 10 and passes through the high pressure main valve 11.
Therefore, the air is sent to the consumer side 12.

According to this embodiment, when the amount of BOG becomes smaller than the amount of LNG passing through the heat exchanger 14 of the heat exchange type gas liquefaction apparatus and the BOG liquefaction pressure falls, the low pressure BO
Since G is introduced into the liquefied gas drum 14, the internal pressure of the liquefied gas drum 14 does not drop too much. Also,
When the amount of BOG increases and the BOG liquefaction pressure increases as compared with the amount of LNG passing through the heat exchanger 13 of the heat exchange type gas liquefaction apparatus, the BOG in the liquefied gas drum 14 is discharged and BO
Since the pressure is returned to the line before the G compression pump, the internal pressure of the liquefied gas drum 14 does not rise too much. Therefore, even if the LNG amount and the BOG amount fluctuate, the pressure in the liquefied gas drum can be always stabilized, and the liquefied BOG
There is no problem such as the booster pump 15 tripping due to the cavitation phenomenon. Further, since the heat exchange type gas liquefaction apparatus can be operated stably, the BOG generated from the low-temperature storage tank 1 can be stably processed, and the pressure in the low-temperature storage tank 1 and the supply pressure of the low-temperature gas can be easily increased. Can be stabilized. In addition, the liquefied gas drum 1
Since the internal pressure of the fuel cell 4 is controlled, the BOG can be stably processed even if the BOG amount fluctuates due to the surrounding environment of the low-temperature storage tank 1 or the LNG amount to be dispensed at the demand of the consumer side is changed. Furthermore, since the BOG liquefaction unit is always operated stably, the liquefied natural gas storage facility can freely change the high-pressure gas amount and the low-pressure gas amount coming to the consumer side, or reduce the low-pressure gas amount to zero. Process can be easily controlled. Furthermore, the pressure of the line connecting the low-pressure vaporizer 4 and the low-pressure main valve 6 and the pressure of the line connecting the BOG compression pump 8 and the first flow control valve 16 communicating with the line are determined according to the process control mode. Irrespective of the pressure, it can always be maintained at a predetermined pressure (for example, 7 kg / cm ² ). Furthermore, L which comes out of the heat exchange type gas liquefaction unit
The temperature of the NG can always be maintained at a predetermined temperature, and even if the flow rate of the LNG changes rapidly, it is possible to respond quickly.

The present invention is not limited to the embodiment described above, and various changes can be made without departing from the gist of the invention. For example, the pressures of the low pressure gas and the high pressure gas are merely examples, and any pressure can be set for the operation of the process. In addition, the lower limit pressure and the upper limit pressure for controlling the pressure in the liquefied gas drum are examples, and any pressure can be set for the operation of the process, or may be different depending on the operation mode. . In addition, how to combine the gas flow control signal, the liquefied gas temperature control signal, and the low-pressure gas pressure control signal to control the first flow control valve is only an example, and it is necessary to operate the process. Any combination can be set. Further, in the flowchart, the heat exchanger 13 is described as one, but a plurality of heat exchangers may be combined. For example, a shell-and-tube heat exchanger may be provided as a pre-cooler in a preceding stage, and a plate-fin type heat exchanger may be provided as a condenser in a subsequent stage.

[0025]

As described above, due to the structure of the heat exchange type gas liquefaction apparatus of the present invention, even if the amount of the liquefied gas as the refrigerant or the amount of the gas fluctuates, the liquefaction pressure of the gas falls below a certain pressure. Since the gas liquefaction pressure does not rise above a certain pressure, the gas liquefaction pressure can always be kept constant. Further, even if the control mode of the heat exchange gas liquefaction apparatus is changed, the gas liquefaction apparatus can be stably controlled, and the liquefaction pressure of the gas can be kept constant. Furthermore, even when the flow rate of the gas or the flow rate of the liquefied gas fluctuates suddenly, the gas liquefaction pressure can be kept constant in a prompt response. Furthermore, since the gas flow rate corresponding to the flow rate of the liquefied gas passed through the heat exchange type gas liquefaction apparatus is liquefied, the ratio between the liquefied gas and the gas can be directly controlled. Furthermore, the outlet temperature of the liquefied gas passing through the heat exchange gas liquefaction device can be directly controlled within a predetermined temperature range. Furthermore, since the gas flow rate according to the gas pressure at the inlet of the first valve flows, the inlet pressure of the first valve can be directly controlled. Furthermore, the heat exchange gas liquefaction apparatus according to the present invention is used for liquefying BOG generated from a liquefied gas storage facility, and liquefied gas discharged from the liquefied gas storage facility and sent to a vaporizer is used as a refrigerant. Therefore, the liquefied gas storage facility can be operated stably.

[Brief description of the drawings]

FIG. 1 is a first process diagram of a liquefied natural gas storage facility equipped with a heat exchange gas liquefaction apparatus according to an embodiment of the present invention.

FIG. 2 is a second process diagram of a liquefied natural gas storage facility equipped with a heat exchange gas liquefaction apparatus according to an embodiment of the present invention.

FIG. 3 is a process diagram of a conventional liquefied natural gas storage facility.

FIG. 4 is a second process diagram of a liquefied natural gas storage facility equipped with a conventional gas liquefaction apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low-temperature storage tank 2 Primary booster pump 3 Low-pressure flow control valve 4 Low-pressure vaporizer 5 Low-pressure gas pressure controller 6 Low-pressure main valve 7 Consumption side (power plant consuming low-pressure gas) 8 BOG compression pump (gas compression pump) 9 Secondary booster pump 10 High-pressure vaporizer 11 High-pressure main valve 12 Consumer side (power plant consuming high-pressure gas) 13 Heat exchanger 14 Liquefied gas drum 15 Liquefied BOG booster pump (liquefied gas booster pump) 16 First flow control valve ( 1st valve) 17 2nd flow control valve (2nd valve) 18 3rd flow control valve (3rd valve) 19 liquefied gas drum pressure controller 20 liquefied gas temperature controller 21 liquefied gas flow controller 22 Control signal synthesizer 23 Control signal comparator 24 Control signal switch 25 BOG pressure controller 26 Drum pressure control valve 27 High pressure flow control valve 28 High pressure flow controller

Claims (6)

[Claims] A heat exchange type gas liquefaction apparatus for exchanging a gas with a liquefied gas for heat exchange, cooling and liquefying the gas, comprising: a gas compression pump (8) for compressing the gas; A first valve (16) for supplying to the exchanger, a heat exchanger (13) for exchanging heat supplied with gas from the first valve with liquefied gas and condensing the gas, and a liquefied gas drum for storing the condensed gas (14) and a second valve (1) for injecting a part of the gas discharged from the gas compression pump into the liquefied gas drum.
7) according to the gas pressure in the liquefied gas drum,
Adjusting the gas flow rate through the second valve (17). 2. A heat exchange gas liquefaction apparatus for exchanging a gas with a liquefied gas for heat exchange, cooling and liquefying the gas, comprising: a gas compression pump (8) for compressing the gas; A first valve (16) for supplying to the exchanger, a heat exchanger (13) for exchanging heat supplied with gas from the first valve with liquefied gas and condensing the gas, and a liquefied gas drum for storing the condensed gas (14) a third valve (18) for returning the gas in the liquefied gas drum to a line before the gas compression pump, and the gas passing through the third valve (18) according to the gas pressure in the liquefied gas drum Adjusting the flow rate, heat exchange type gas liquefaction apparatus 3. The heat exchange gas liquefaction according to claim 1, wherein the gas flow rate passing through the first valve is adjusted according to the flow rate of the liquefied gas passing through the heat exchanger. apparatus 4. The heat exchange type gas according to claim 1, wherein a gas flow rate passing through the first valve is adjusted according to a temperature of the liquefied gas discharged from the heat exchanger. Liquefaction equipment 5. The heat exchange gas liquefaction according to claim 1, wherein the gas flow rate through the first valve is adjusted according to the gas pressure at the inlet of the first valve. apparatus 6. B generated from a liquefied gas storage facility
The heat exchange gas according to any one of claims 1 to 5, wherein the liquefied gas is OG, and the liquefied gas is discharged from the liquefied gas storage tank and sent to the vaporizer. Liquefaction equipment