GAS SUPPLY SYSTEM

A system for supplying a gas to a supply target from a fluid of a gas-liquid mixture stored in a pressure vessel, comprising: a first line connected to a layer of the gas in the pressure vessel; a second line connected to a layer of the liquid in the pressure vessel and having a vaporizer in the middle and merging into the first line downstream of the vaporizer; a valve disposed between the pressure vessel and the vaporizer in the second line; a pressure gauge for obtaining a pressure in the pressure vessel; and a control device, wherein the control device receives pressure information from the pressure gauge and, when the internal pressure of the pressure vessel falls below a predetermined value, controls to open the valve and supply the vaporized gas in the vaporizer in the second line from the first line to the pressure vessel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2022-180342 filed on Nov. 10, 2022, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a gas supply system.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2004-308844 (JP 2004-308844 A) discloses the installation of a second tank with an adsorbent as a means for effectively using the boil-off gas in a cryogenic tank without discharging the boil-off gas to the outside of the system. JP 2004-308844 A discloses that a back pressure valve is installed between a first tank and the second tank, and the pressure on the first tank side is maintained as high as possible to reduce the amount of the boil-off gas, thereby suppressing the discharge amount of the boil-off gas from the second tank to the atmosphere.

SUMMARY

However, in the conventional technique described in JP 2004-308844 A, the tank internal pressure changes according to the magnitude of the intrusion heat, and it is difficult to cope with a change in the internal pressure.

In view of the above problems, an object of the present disclosure is to provide a gas supply system capable of adjusting the internal pressure in response to the change in the internal pressure of a pressure vessel.

The present application discloses a gas supply system, and the gas supply system for supplying a gas to a supply target from a gas-liquid mixture fluid stored in a pressure vessel includes:a first line connected to a layer of the gas in the pressure vessel;a second line connected to a layer of liquid in the pressure vessel and including a vaporizer in a middle of the second line, and merging into the first line downstream of the vaporizer;a valve disposed between the pressure vessel and the vaporizer in the second line;a pressure gauge for obtaining a pressure in the pressure vessel; anda control device.

The control device receives pressure information from the pressure gauge, and opens the valve and performs control to supply the gas vaporized by the vaporizer in the second line from the first line to the pressure vessel when an internal pressure of the pressure vessel falls below a predetermined value.

Further, the present application discloses a gas supply system, and the gas supply system for supplying a gas to a supply target from a gas-liquid mixture fluid stored in a pressure vessel includes:a first line connected to a layer of the gas in the pressure vessel;a second line connected to a layer of liquid in the pressure vessel and including a vaporizer in a middle of the second line, and merging into the first line downstream of the vaporizer;a valve disposed between the pressure vessel and the vaporizer in the second line;a pressure gauge for obtaining a pressure in the pressure vessel; anda control device.

The control device receives pressure information from the pressure gauge, and closes the valve and performs control to supply the gas from the first line to the supply target when an internal pressure of the pressure vessel exceeds a predetermined value.

The gas supply system may be configured such that the first line is also provided with a valve, and opening and closing of the valve is controlled by the control device.

According to the present disclosure, the internal pressure can be adjusted in response to the change in the internal pressure in the pressure vessel.

DETAILED DESCRIPTION OF EMBODIMENTS

1. Configuration of the Gas Supply System

FIG.1conceptually illustrates a configuration of a gas supply system10according to one embodiment. Such a gas supply system10is a system that supplies a cryogenic fluid such as liquid nitrogen or liquid oxygen stored in a pressure vessel in a gas-liquid mixed state to a supply target in a gas state.

The gas supply system10comprises a pressure vessel11. A cryogenic fluid is stored in a gas-liquid mixed state inside the pressure vessel11. The pressure vessel11includes a first line12and a second line13. The first line12is a piping system that connects to the gas layer of the stored cryogenic fluid and serves as a flow path for extracting and flowing a gas. The second line13is a piping system that is connected to the liquid layer of the stored cryogenic fluid and serves as a flow path through which the cryogenic fluid is taken out in a liquid state and flows. Therefore, the first line12is connected to the upper portion of the pressure vessel11. The second line13is connected to the lower portion of the pressure vessel11. The first line12and the second line13merge in the middle (portion G) and are connected to the supply target1.

The pressure vessel11is provided with a safety valve14for releasing gas from the inside of the pressure vessel11and a pressure gauge15for obtaining the pressure (internal pressure) inside the pressure vessel11. The pressure gauge15is configured to transmit the measured value as a signal to a control device20, which will be described later.

In addition, a switching valve12afor switching between the permission and prohibition of the flow of the fluid is disposed in the first line12. In the second line13, a switching valve13afor switching between the permission and the prohibition of the flow of fluid is arranged in the middle thereof. The switching valve12a,13ais a solenoid valve and is configured to be capable of switching between an open state (an allowable state of fluid flow) and a closed state (a prohibited state of fluid flow) upon receiving a signal from a control device20, which will be described later.

Further, a vaporizer16is provided between the switching valve13aand the merging portion G in the second line13. The vaporizer16is a device that heats and vaporizes a liquid cryogenic fluid flowing in the second line13. The vaporizer16is not particularly limited as long as it can be heated so as to vaporize the liquid flowing in the pipe, and a known vaporizer can be used.

The control device20obtains the pressure information from the pressure gauge15, performs calculation, and issues a command to the switching valve12a,13abased on the calculation result, thereby controlling the flow of the fluid and appropriately holding the internal pressure of the pressure vessel11. Such a control device20includes a processor and Central Processing Unit (CPU) a Random Access Memory (RAM) that functions as a working area, a Read-Only Memory (ROM) that functions as a recording medium), a receiving unit that is an interface to which a device is connected and receives information from the device to the control device20, and a transmitting unit that is an interface that is connected from the device and transmits information to the outside from the control device20.

The control device20stores a program that processes information from each device and determines and operates the operation of the device. In the control device20, a CPU, RAM and a ROM as hardware resources and programs cooperate with each other. Specifically, a CPU controls a device by executing a computer program recorded in a ROM in a RAM functioning as a working area. The data acquired or generated by CPU is stored in RAM. In addition, a recording medium may be separately provided inside or outside the control device20, and programs and various data may be recorded therein. Such a control device20can typically be constituted by a computer.

2. Internal Pressure Control of the Pressure Vessel

As an example, the internal pressure control S1of the pressure vessel by the gas supply system10will be described. This control is performed by the control device20calculating the pressure obtained by the pressure gauge15and controlling the switching valve12a,13a. InFIG.2, the flow of the pressure vessel internal pressure control S1is shown.

As a precondition, as the pressure related to the pressure vessel11, the pressure lower limit specified value shall be Pl, the pressure upper limit specified value shall be Pu, the safety valve set value shall be Ps, and the pressure vessel internal pressure shall be P. Here, Pl is the pressure defined as the minimum required to deliver the gases to the supply target1. Pu is the maximum pressure that can be tolerated by the pressure vessel11(not the pressure of the nature of the pressure vessel11to rupture, but the maximum pressure in terms of gas-supply control). Ps is the pressure at which the safety valve14operates. These pressures are set to a predetermined value, and the relation of Pl<Pu<Ps is established. P is the pressure in the pressure vessel11obtained by the pressure gauge15, and varies depending on the situation.

As can be seen fromFIG.2, the internal pressure control S1of the pressure vessel includes the steps of the measurement S2of P, the valve control calculation P3based on the P, and the valve control S4.

In the measurement S2of P, an internal pressure of the pressure vessel11is obtained by the pressure gauge15, and the measurement data is signaled to the control device20. In the valve control calculation S3based on the value of P, the control device20performs calculation based on the pressure value obtained by the measurement S2of P, thereby determining a command (valve control) for the switching valve12a,13a. In the valve control S4, a command is given to the switching valve12a,13abased on the P determined by the valve control calculation S3based on the P. The opening and closing status of the specific switching valve12a,13ain the valve control S4varies depending on the P, and the flow thereof is shown inFIGS.3to6.

If P≥Ps, the control S10proceeds as shown inFIG.3. This is when the internal pressure of the pressure vessel11is equal to or higher than the operating pressure of the safety valve14, and the safety valve14is opened (process S11), the gas is discharged from the pressure vessel11, and the internal pressure of the pressure vessel11is lowered. Thereafter, P is measured by the pressure gauge15again (process S12), and P≥Ps is determined by the control device20(process S13). If Yes in the process S13, the internal pressure is still higher, so that the safety valve remains open (process S14) and returns to the process S12. On the other hand, if it is No in the process S13, the internal pressure becomes lower than Ps, so that the safety valve is closed (process S15), and the process returns to the measurement S2of P.

When 2.2.Pl≤P≤Pu

When Pl≤P≤Pu, the control S20proceeds as shown inFIG.4. This is the case when the internal pressure of the pressure vessel11is between the pressure lower limit specified value Pl and the pressure upper limit specified value Pu, and the internal pressure of the pressure vessel11does not need to be positively changed. At this time, the switching valve12a(valve1) of the first line12is closed, and the switching valve13a(valve2) of the second line13is opened (process S21). As a result, the fluid in the liquid state flows from the pressure vessel11through the second line13, is vaporized by the vaporizer16, and is supplied with gas to the supply target1. Then, the process returns to the measurement S2of P.

When 2.3.Pu<P<Ps

When Pu<P<Ps, the control S30proceeds as shown inFIG.5. This is the case when the internal pressure of the pressure vessel11has not reached the operating pressure Ps of the safety valve14but exceeds the pressure upper limit specified value Pu. At this time, the switching valve12aof the first line12is opened, and the switching valve13aof the second line13is closed (process S31). As a result, the fluid in the gaseous state flows from the pressure vessel11through the first line12, and the gas is supplied to the supply target1. Therefore, the internal pressure of the pressure vessel11is reduced. Thereafter, P is measured by the pressure gauge15again (process S32), and the control device20determines P=Pl (process S33). If it is No in the process S33, since the internal pressure of the pressure vessel11has not reached the pressure lower limit specified value Pl, the switching valve12a,13ais maintained in the process S31(process S34) and returns to the process S32. On the other hand, if it is Yes in the process S33, the internal pressure has reached Pl, so that the switching valve12aof the first line12is closed (process S35), and the process returns to the measurement S2of P.

For 2.4.P<Pl

When P<Pl, the control S40proceeds as shown inFIG.6. This is the case when the internal pressure of the pressure vessel11falls below the pressure lower limit specified value Pl. At this time, both the switching valve12aof the first line12and the switching valve13aof the second line13are opened (process S41). According to this, the internal pressure of the pressure vessel11is reduced, and there is a pressure difference by an amount corresponding to the height of the liquid in the pressure vessel11. Therefore, a part of the fluid vaporized by the vaporizer16branches at the position G, and gas flows toward the gas layer of the pressure vessel11as indicated by the straight arrow A inFIG.1. This increases the internal pressure of the pressure vessel11. Note that another part of the fluid vaporized by the vaporizer16is supplied to the supply target1. Thereafter, P is measured by the pressure gauge15again (process S42), and the control device20determines P=Pu (process S43). If it is No in the process S43, since the internal pressure of the pressure vessel11has not reached the pressure upper limit specified value Pu, the switching valve12a,13ais maintained in the process S41(process S44) and returns to the process S42. On the other hand, if it is Yes in the process S43, the internal pressure P has reached Pu, so that the switching valve12aof the first line12is closed (process S45), and the process returns to the measurement S2of P.

According to the present disclosure, when the internal pressure of the pressure vessel falls below the pressure lower limit specified value, the internal pressure of the pressure vessel is increased by the process S40. If the internal pressure of the pressure vessel exceeds the pressure upper limit specified value, the internal pressure of the pressure vessel is lowered by the process S30. As a result, the internal pressure of the pressure vessel can be appropriately controlled, and the internal pressure of the pressure vessel can be stably stored between the lower limit value and the upper limit value.

3. Other Forms

In another embodiment, the gas supply system10may be a gas supply system that does not include a switching valve12ain the first line12. As a result, the effect of the gas supply system10can be achieved, and the number of components of the system can be reduced and simplified. In the other embodiment, control is performed as in the control S101as shown inFIG.7. The measurement S2of P constituting the control S101, the valve control calculation S3based on the P, and the valve control S4are the same as those described above. However, the valve control S4performed here is advanced by the control S10shown inFIG.3and the control S110shown inFIG.8. The details are as follows.

When 3.2.Pl≤P≤Pu

If Pl≤P≤Pu, it is advanced by the control S110as shown inFIG.8. At this time, the switching valve13aof the second line13is closed (process S111). As a result, the fluid in the gaseous state flows from the pressure vessel11through the second line13, and the gas is supplied to the supply target1. If this is continued, the internal pressure of the pressure vessel11decreases. Then, the internal pressure of the pressure vessel11is obtained by the pressure gauge15(process S112), and it is determined whether or not P≤Pl (process S113). If this is No, the vessel11is not yet below Pl, so that the valve condition of the process S111is maintained (process S114) and the process S112is returned. On the other hand, if it is Yes in the process S113, since P has fallen below Pl, the switching valve13aof the second line13is changed to the open state (process115). As a result, the gas can be supplied to the supply target1while increasing the internal pressure of the pressure vessel11as described in the control S40. Continuing this, the internal pressure of the pressure vessel11increases. Then, the internal pressure of the pressure vessel11is obtained by the pressure gauge15(process S116), and it is determined whether or not P>Pu (process S117). If this is No, the vessel11has not yet reached Pu, so that the valve condition of the process S115is maintained (process S118) and the process S116is returned. On the other hand, if it is Yes in the process S117, since P exceeds Pu, it returns to the process S111to change the switching valve13aof the second line13to the closed state, and thereafter, the above is repeated.

When 3.3.Pu<P<Ps

If Pu<P<Ps, the process S111of the control S110shown inFIG.8may be started.

For 3.4.P<Pl

If P<Pl, the process S115of the control S110shown inFIG.8may be started.