JP2018165511A - Working fluid supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working fluid supply control device.SOLUTION: In this working fluid supply control device for supplying a working fluid to a power generation cycle having a compressor for compressing the working fluid, and a precooler for cooling the working fluid supplied to the compressor, the working fluid supply control device includes a storage tank for storing the working fluid supplied to the power generation cycle, and a floatation tank which is arranged between the precooler and the compressor, and in which the working fluid circulates, or is temporarily stored. Pressure in the floatation tank and a flow rate of the working fluid are controlled according to the pressure of an inlet of the compressor and the pressure of an outlet of the precooler. According to this invention, the pressure of the inlet and the pressure of the outlet of the compressor can be controlled, the flow rate of the working fluid can be efficiently controlled without using an expensive inventory tank, and thus the working fluid supply device has an effect for reducing a cycle constitution expense and improving economical efficiency.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a working fluid supply control device, and more particularly, to a working fluid supply control device capable of efficiently and economically controlling the flow rate and pressure of a working fluid and supplying the same into a power generation cycle.

In order to increase electricity production while reducing the generation of pollutants as the need for internationally efficient power production increases and the movement to reduce the generation of pollutants becomes more and more active I am committed to various efforts. As part of such efforts, research and development related to a supercritical carbon dioxide power generation system (Power generation system using Supercritical CO ₂ ) using supercritical carbon dioxide as a working fluid has been actively conducted.

  Since carbon dioxide in the supercritical state has a density similar to that in the liquid state and a viscosity similar to that in the gas, not only miniaturization of the equipment but also minimization of power consumption required for fluid compression and circulation is achieved. Can do. In addition, carbon dioxide in the supercritical state has a critical point of 31.4 degrees Celsius and 72.8 atmospheres, which is much lower than water with a critical point of 373.95 degrees Celsius and 217.7 atmospheres, There is an advantage that it is easy to handle.

  In addition, the supercritical carbon dioxide power generation system is mostly operated in a closed cycle that does not discharge the carbon dioxide used for power generation to the outside, which can greatly help reduce emissions of pollutants by country. Can do.

  Generally, a supercritical carbon dioxide power generation system has a closed cycle that does not discharge carbon dioxide used for power generation to the outside, and uses carbon dioxide in a supercritical state as a working fluid.

  The working fluid is supplied into the cycle for two purposes: for power generation, which is injected into the power generation cycle to drive the turbo equipment, and for turbo equipment for turbo equipment bearing lubrication and sealing. An example of a method for supplying a working fluid is disclosed in US Pat. No. 8,281,593.

  The working fluid charging system disclosed in the above-mentioned prior art is a system in which the working fluid stored in the storage tank is supplied to the inside of the cycle and the turbomachine using a high-pressure piston pump. In addition, a mass control tank is provided for controlling the flow rate of the working fluid and controlling the pressure at the inlet and outlet of the compressor. The mass control tank is also called an inventory tank. Generally, the mass control tank is installed so as to be connected to an outlet high pressure line of a compressor and an inlet low pressure line of a precooler. When the compressor outlet pressure increases, the pressure can be reduced by opening a high pressure valve and sending a portion of the flow to the mass control tank. When the compressor inlet pressure decreases, the pressure can be increased by opening a low pressure valve to send a portion of the mass control tank flow to the compressor inlet line.

  Therefore, since the mass control tank is connected to the outlet high-pressure line of the compressor, it is indispensable to be composed of expensive materials and parts that can withstand high pressure, so there is a problem that the cost is high and the cost is inferior.

US Patent Registration No. 8281593 (registered on October 9, 2012)

  An object of the present invention is to provide a working fluid supply control device that can efficiently and economically control the flow rate and pressure of a working fluid and supply the working fluid into a power generation cycle.

  The working fluid supply control device of the present invention is a working fluid for supplying a working fluid to a power generation cycle provided with a compressor that compresses the working fluid and a precooler that cools the working fluid supplied to the compressor. In the supply control device, a storage tank that stores the working fluid supplied to the power generation cycle, and a flotation tank that is disposed between the precooler and the compressor and in which the working fluid flows or is temporarily stored. The pressure in the flotation tank and the flow rate of the working fluid are controlled in accordance with the pressure at the inlet of the compressor and the outlet of the precooler.

  Provided between the storage tank and the flotation tank, provided between the storage tank and the flotation tank, a supply pump for supplying the working fluid from the storage tank to the flotation tank, And a control valve for discharging the working fluid from a flotation tank to the storage tank.

  The flotation tank is a piston accumulator type tank.

  The flotation tank includes a tank body into which the working fluid flows, and a piston that is installed inside the tank body and moves up and down by a control fluid supplied from the outside.

  The flotation tank is provided at a lower end of the tank main body, is provided with a control fluid inflow portion into which the control fluid flows in, and is provided at one side of the tank main body, and the working fluid flows in from the supply pump. It further includes an inlet and a first outlet that is provided on the other side of the tank body and discharges the working fluid to the control valve.

  The flotation tank is provided at an upper part of the tank body, and is provided at a second inlet through which the working fluid flows from the precooler, and at an upper part of the tank body, and the working fluid is discharged to the compressor. And a second outlet.

Wherein when the pressure P ₂ at the front stage of the pressure P ₁ or the compressor in the subsequent stage of the pre-cooler is increased, the control fluid to the control fluid inlet is supplied, by opening the control valve The working fluid in the flotation tank is discharged to the storage tank through the first outlet.

  The supply of the control fluid and the discharge of the working fluid to the storage tank are performed until the height of the piston reaches a height corresponding to a set value.

If the pressure P ₂ becomes lower at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler, said working fluid through said first inlet by operating the supply pump to the flotation tank It is characterized by supplying.

  The working fluid is supplied into the flotation tank until the height of the piston reaches a height corresponding to a set value.

  Further, the present invention provides a working fluid supply control device for supplying a working fluid to a power generation cycle provided with a compressor for compressing the working fluid and a precooler for cooling the working fluid supplied to the compressor. A storage tank that stores the working fluid supplied to the power generation cycle, a flotation tank that is disposed in an inlet low pressure line of the compressor, and in which the working fluid flows or is temporarily stored, the storage tank, and the flotation A supply pump that is provided between the storage tank and the flotation tank, and is provided between the storage tank and the flotation tank. And a control valve for discharging the fluid to the storage tank. Rukoto can.

  When the pressure at the outlet of the precooler or the inlet of the compressor becomes high, the working fluid is discharged from the flotation tank to the storage tank, and when the pressure at the outlet of the precooler or the inlet of the compressor becomes low, The working fluid is supplied from the storage tank to the flotation tank.

  The flotation tank is a piston accumulator type tank.

  The flotation tank includes a tank body into which the working fluid flows, and a piston that is installed inside the tank body and moves up and down by a control fluid supplied from the outside.

  The flotation tank is provided at a lower end of the tank main body, is provided with a control fluid inflow portion into which the control fluid flows in, and is provided at one side of the tank main body, and the working fluid flows in from the supply pump. It further includes an inlet and a first outlet that is provided on the other side of the tank body and discharges the working fluid to the control valve.

  The flotation tank is provided at an upper part of the tank body, and is provided at a second inlet through which the working fluid flows from the precooler, and at an upper part of the tank body, and the working fluid is discharged to the compressor. And a second outlet.

If the pressure P ₂ at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler is increased, the control and the control fluid is supplied to the fluid inlet, the first to open the control valve The working fluid in the flotation tank is discharged to the storage tank through an outlet.

  The supply of the control fluid and the discharge of the working fluid to the storage tank are performed until the height of the piston reaches a height corresponding to a set value.

If the pressure P ₂ becomes lower at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler, said working fluid through said first inlet by operating the supply pump to the flotation tank It is characterized by supplying.

  The working fluid is supplied into the flotation tank until the height of the piston reaches a height corresponding to a set value.

  The working fluid supply control device according to an embodiment of the present invention can control the pressure at the inlet and outlet of the compressor without using an expensive inventory tank, and can efficiently control the flow rate of the working fluid. Therefore, there is an effect that the cost of the cycle configuration is reduced and the economy is improved.

It is a mimetic diagram showing an example of the power generation cycle to which the working fluid supply control device concerning one embodiment of the present invention was applied. It is a schematic diagram which shows an example of the working fluid supply control apparatus by FIG. It is a schematic diagram which shows the operating state of the working fluid supply control apparatus by FIG. It is a schematic diagram which shows the operating state of the working fluid supply control apparatus by FIG.

  Hereinafter, a working fluid supply control apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  Generally, a supercritical carbon dioxide power generation system has a closed cycle that does not discharge carbon dioxide used for power generation to the outside, and uses carbon dioxide in a supercritical state as a working fluid.

  In the supercritical carbon dioxide power generation system, since the working fluid is carbon dioxide in a supercritical state, exhaust gas discharged from a thermal power plant can be used. Therefore, not only a single power generation system but also a thermal power generation system can be used. It can also be used for hybrid power generation systems. The working fluid of the supercritical carbon dioxide power generation system may supply carbon dioxide separated from the exhaust gas or may supply additional carbon dioxide.

  Supercritical carbon dioxide (hereinafter referred to as “working fluid”) in the cycle passes through the compressor and is heated while passing through a heat source such as a heater to become a high-temperature and high-pressure working fluid to drive the turbine. A generator or a pump is connected to the turbine, electric power is produced by the turbine connected to the generator, and the pump is driven using the turbine connected to the pump. The working fluid that has passed through the turbine is cooled through a heat exchanger, and the cooled working fluid is supplied again to the compressor and circulates in the cycle. A plurality of turbines or heat exchangers may be provided.

  The supercritical carbon dioxide power generation system according to various embodiments of the present invention is not only a system in which all of the working fluid flowing in the cycle is in the supercritical state, but also the majority of the working fluid is in the supercritical state and remains. Is used to include systems that are in a subcritical state.

  Further, in various embodiments of the present invention, carbon dioxide is used as a working fluid. Here, carbon dioxide is pure carbon dioxide in a chemical sense, and some impurities are included from a general viewpoint. Carbon dioxide in a state of being present, and fluid in a state where one or more fluids are mixed with carbon dioxide as an additive.

  FIG. 1 is a schematic diagram showing an example of a power generation cycle to which a working fluid supply control device according to an embodiment of the present invention is applied.

  As shown in FIG. 1, the power generation cycle to which the working fluid supply control device is applied includes a supercritical carbon dioxide having one turbine, a plurality of recuperators 200, and a plurality of external heat exchangers 300. It can be a power generation cycle.

  Each configuration of the present invention is connected by a transfer tube through which the working fluid flows, and it should be understood that the working fluid flows along the transfer tube, unless otherwise specified. However, in the case where a plurality of components are integrated, there is a part or region that substantially functions as a transfer pipe in the integrated configuration. (In the present invention, the transfer pipe is indicated by a number in parentheses).

  The working fluid supplied into the cycle via the working fluid supply control device is compressed to a high pressure by the compressor 100, a part branches to the recuperator 200, and a part branches to the external heat exchanger 300.

  The recuperator 200 includes a first recuperator 210 and a second recuperator 230. These recuperators are arranged in series, and the working fluid that has passed through the first recuperator 210 sequentially flows into the second recuperator 230. Since the working fluid that has passed through the turbine 400 flows into the first recuperator 210 first, the first recuperator 210 exchanges heat with the working fluid having a relatively higher temperature than the second recuperator 230.

  The external heat exchanger 300 includes a first heat exchanger 310 and a second heat exchanger 330. The first and second heat exchangers 310 and 330 use a gas having waste heat (hereinafter referred to as “waste heat gas”) like exhaust gas discharged from a boiler of a power plant as a heat source. It serves to heat the working fluid with heat supplied from the waste heat gas by heat exchange with the working fluid circulating inside.

  When a plurality of heat exchangers 300 are provided, the heat exchanger 300 can be classified into a relatively low temperature, a medium temperature, a high temperature, and the like according to the temperature of the waste heat gas. In other words, the heat exchanger can exchange heat at a higher temperature as it is closer to the inlet end side where the waste heat gas flows in, and heat exchange is performed at a lower temperature as it is closer to the outlet end side where the waste heat gas is discharged. .

  In the present embodiment, the first heat exchanger 310 is a heat exchanger that uses waste heat gas that is relatively hot or medium compared to the second heat exchanger 330, and the second heat exchanger 330 has a relative In particular, it may be a heat exchanger using a medium-temperature or low-temperature waste heat gas. That is, an example in which the first heat exchanger 310 and the second heat exchanger 330 are sequentially arranged from the inlet end where the waste heat gas flows in to the discharge end side will be described.

  As described above, a part of the working fluid that has passed through the compressor 100 is sent to the second recuperator 230, exchanged heat with the working fluid that has passed through the first recuperator 210, and heated primarily, and then the first recuperator 210. To the working fluid that has passed through the turbine 400 and heated. Thereafter, it is transferred to the front stage of the first heat exchanger 310.

  Part of the working fluid that has passed through the compressor 100 is sent to the second heat exchanger 330, exchanged heat with waste heat gas and heated primarily, and then mixed with the heated working fluid by the first recuperator 210. And sent to the first heat exchanger 310. The working fluid heated by the first heat exchanger 310 is supplied to the turbine 400.

  The turbine 400 is driven by a working fluid, and a generator (not shown) is connected to the turbine 400 so that electric power can be produced by the turbine. Since the working fluid expands while passing through the turbine 400, the turbine 400 also serves as an expander. The working fluid that has passed through the turbine 400 is transferred to the first recuperator 210.

  The working fluid that has passed through the compressor 100 and the working fluid cooled by exchanging heat with the first recuperator 210 and the second recuperator 230 are transferred to the precooler 50.

  The precooler 50 uses air or cooling water as a refrigerant to secondary-cool the working fluid that has been primarily cooled after passing through the recuperator 200. The working fluid cooled through the precooler 50 is supplied to the compressor 100 through a flotation tank 500.

  The working fluid supply control device for supplying the working fluid to the compressor 100 includes a flotation tank 500 disposed between the precooler 50 and the compressor 100 described above, and a storage tank 10 for storing the working fluid. And a supply pump 20 that supplies the working fluid from the storage tank 10 to the flotation tank 500, and a control valve 30 that discharges the working fluid from the flotation tank 500 to the storage tank 10.

  The storage tank 10 is a large-capacity reservoir capable of storing and supplying the flow rate of the working fluid necessary for the entire cycle, and can store at least the amount of the working fluid necessary for the initial driving of the cycle. With the size of Since the storage tank 10 is also used when extracting a partial flow rate of the working fluid in the cycle, it is desirable that the storage tank 10 can store a flow rate larger than the total working fluid flow rate of the cycle. The pressure of the working fluid supplied from the storage tank 10 to the flotation tank 500 can be first increased by the supply pump 20 and secondarily controlled in the flotation tank 500 to be supplied to the compressor 100.

  Since the flotation tank 500 is installed at the inlet end of the compressor 100, the flotation tank 500 acts as a buffer against a change in pressure at the inlet of the compressor 100. Therefore, the pressure control at the inlet of the compressor 100 can be automatically controlled by the flotation tank 500.

  The buffer action for the pressure change at the inlet of the compressor 100 is performed by the buffer action for the pressure change in the flotation tank 500. To this end, the flotation tank 500 is preferably provided as a piston accumulator type tank. The maximum allowable flow rate of the flotation tank 500 may be, for example, 215 L / sec. The piston accumulator type tank has the advantage that the response speed and reaction time of the control reaction are very fast.

  Since the flotation tank 500 is installed at the inlet end of the compressor 100, the working fluid before being compressed is temporarily stored or fluidized. Therefore, the flotation tank 500 is located in the low pressure line in the cycle and does not require expensive materials and parts that can withstand high pressure unlike the conventional inventory tank, so that an economical cycle configuration is possible. There is.

  The storage tank 10 must have a minimum size that can store the flow rate of the working fluid required for the entire cycle, whereas the flotation tank 500 is entirely for pressure buffer function. It is sufficient if a working fluid of about 1/3 of the cycle flow rate can be stored. Therefore, since the size of the flotation tank 500 can be reduced to 1/3 compared to the conventional inventory tank, there is an effect that the cycle configuration cost can be reduced.

  Next, the pressure buffer function of the flotation tank 500 will be described in detail.

  FIG. 2 is a schematic diagram illustrating an example of the working fluid supply control device according to FIG. 1, and FIGS. 3 and 4 are schematic diagrams illustrating an operating state of the working fluid supply control device according to FIG.

  As shown in FIG. 2, the flotation tank 500 includes a tank main body 510, a piston 530 installed inside the tank main body 510, and a piston position control fluid that is provided at the lower end of the tank main body 510 and raises and lowers the piston 530. Is provided on one side of the tank main body 510 and the first inlet 512 through which the working fluid flows from the supply pump 20, and provided on the other side of the tank main body 510 and operates to the control valve 30. And a first outlet 514 through which fluid is discharged. In addition, the upper part of the tank body 510 that is separated from the first inlet 512 and the first outlet 514 is located apart from the second inlet 516 through which the working fluid flows from the precooler 50 and the second inlet 516, And a second outlet 518 through which the working fluid is discharged to the compressor 100.

In FIG. 2, _{P 1} denotes the pressure at the later stage of the pre-cooler 50, _{P 2} indicates the pressure at the preceding stage of the compressor 100, _{P S} represents a pressure floatation tank 500. F ₁ indicates the flow rate of the control fluid for controlling the position of the piston 530 (a fluid separate from the working fluid supplied into the cycle, and other working fluid is not supercritical carbon dioxide. Can be used). H _S indicates the height of the piston 530 at a set point in the flotation tank 500, and H _A indicates the height of the piston 530 due to a pressure change in the flotation tank 500. P _S and H _S are in the design cycle, is set to a preset set value, the set value is controlled to be maintained in floatation tank 500 in response to pressure changes. Next, a method for controlling the flotation tank 500 according to a pressure change will be described in detail with reference to the above-described content.

As shown in FIG. 3, there may be a case where P ₁ is increased occurs.

When P ₁ rises, the height of the piston 530 falls from H 2 _S to H _A in the flotation tank 500. At this time, along with raising the piston 530 to set the height H _S of the flotation tank 500, in order to maintain the reference pressure P _S is injected control fluid at a flow rate of F _1. At the same time, the control valve 30 is opened to discharge the flow rate of a part of the working fluid in the flotation tank 500 and send it to the storage tank 10. Such processes, when P _S and H _S are maintained at the set value, as well as stops the discharge of the working fluid from flotation tank 500 by closing the control valve 30, the control fluid injection at F ₁ flow rate Discontinue. At this time, the supply pump 20 is not driven.

On the other hand, even in the event that if P ₂ is high, as shown in FIG. 3, it is possible to piston 530 descends to the height of the H _A. Also in this case, the height of the piston 530 falls from H 2 _S to H 2 _A in the flotation tank 500. Therefore, the control valve 30 is opened and a part of the working fluid in the flotation tank 500 so that the control fluid is injected at F ₁ to maintain the reference pressure P _S and the piston 530 can be raised to H _S. Is discharged to the storage tank 10. When P _S and H _S are maintained at the set value, as well as stops the discharge of the working fluid from flotation tank 500 by closing the control valve 30, it stops the control fluid injection at F ₁ flow rate.

Conversely, as shown in FIG. 4, there may be a case where P ₁ is lower occur.

When P ₁ decreases, the height of the piston 530 increases from H _S to H _A in the flotation tank 500. At this time, the piston 530 is lowered to the set height H _S in the flotation tank 500 and the supply pump 20 is operated to maintain the reference pressure P _S to replenish the flow rate of the working fluid in the flotation tank 500. To do. When this process by P _S and H _S reaches the set value, to maintain P _S and H _S by the supply pump 20 is stopped to stop the supply of the working fluid into the flotation tank 500. At this time, the control valve 30 is not driven, and the control fluid for setting the position of the piston 530 is not supplied.

Further, even occurs when the P ₂ becomes lower, as shown in FIG. 4, it is possible to piston 530 is raised to a height of H _A. Therefore, the piston 530 is lowered to the set height H _S in the flotation tank 500, and the supply pump 20 is operated to maintain the reference pressure P _S to replenish the flow rate of the working fluid into the flotation tank 500. To do. When this process by P _S and H _S reaches the set value, to maintain P _S and H _S by the supply pump 20 is stopped to stop the supply of the working fluid into the flotation tank 500.

  As described above, since the pressure in the flotation tank and the flow rate of the working fluid vary according to the pressure changes at the compressor inlet and the precooler outlet, the pressure in the flotation tank and the height of the piston are constant. The set value can be maintained. Since the flotation tank acts as a buffer according to the pressure change at the inlet of the compressor in this way, there is no need for separate pressure control, so expensive materials and parts like conventional inventory tanks are not used. Therefore, there is an effect that the cost of cycle configuration is reduced. In addition, the flow rate of the working fluid can be efficiently controlled only by the flotation tank, and the pressure at the inlet / outlet of the compressor can be controlled. is there.

  The embodiment of the present invention described above and shown in the drawings should not be construed as limiting the technical idea of the present invention. The scope of the present invention is limited only by the matters described in the claims. A person having ordinary knowledge in the technical field of the present invention can improve and change the technical idea of the present invention into various forms. Therefore, it can be said that those improvements and modifications belong to the scope of the present invention as long as it is obvious to those having ordinary knowledge.

DESCRIPTION OF SYMBOLS 10 Storage tank 20 Supply pump 30 Control valve 50 Precooler 100 Compressor 200 Recuperator 300 Heat exchanger 400 Turbine 500 Flotation tank

Claims (20)

A working fluid supply control device for supplying a working fluid to a power generation cycle provided with a compressor that compresses the working fluid and a precooler that cools the working fluid supplied to the compressor;
A storage tank for storing the working fluid supplied to the power generation cycle;
A flotation tank disposed between the precooler and the compressor, in which the working fluid flows or is temporarily stored,
A working fluid supply control device in which a pressure in the flotation tank and a flow rate of the working fluid are controlled in accordance with pressures at an inlet of the compressor and an outlet of the precooler.   Provided between the storage tank and the flotation tank, provided between the storage tank and the flotation tank, a supply pump for supplying the working fluid from the storage tank to the flotation tank, The working fluid supply control device according to claim 1, further comprising a control valve for discharging the working fluid from a flotation tank to the storage tank.   The working fluid supply control device according to claim 2, wherein the flotation tank is a piston accumulator type tank.   4. The working fluid supply according to claim 3, wherein the flotation tank includes a tank body into which the working fluid flows, and a piston that is installed inside the tank body and moves up and down by a control fluid supplied from outside. Control device.   The flotation tank is provided at a lower end of the tank main body, is provided with a control fluid inflow portion into which the control fluid flows in, and is provided at one side of the tank main body, and the working fluid flows in from the supply pump. The working fluid supply control device according to claim 4, further comprising: an inlet; and a first outlet provided on the other side of the tank body and discharging the working fluid to the control valve.   The flotation tank is provided at an upper part of the tank body, and is provided at a second inlet through which the working fluid flows from the precooler, and at an upper part of the tank body, and the working fluid is discharged to the compressor. The working fluid supply control device according to claim 5, further comprising a second outlet. If the pressure P ₂ at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler is increased, the control and the control fluid is supplied to the fluid inlet, the first to open the control valve The working fluid supply control device according to claim 6, wherein the working fluid in the flotation tank is discharged to the storage tank through an outlet.   The supply of the control fluid and the discharge of the working fluid to the storage tank are performed until the height of the piston reaches a height corresponding to a set value. Working fluid supply control device. If the pressure P ₂ becomes lower at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler, said working fluid through said first inlet by operating the supply pump to the flotation tank The working fluid supply control device according to claim 5, wherein the working fluid supply control device is supplied.   The working fluid supply control device according to claim 9, wherein the working fluid is supplied into the flotation tank until the height of the piston reaches a height corresponding to a set value. A working fluid supply control device for supplying the working fluid to a power generation cycle provided with a compressor for compressing the working fluid and a precooler for cooling the working fluid supplied to the compressor;
A storage tank for storing the working fluid supplied to the power generation cycle;
A flotation tank disposed in an inlet low pressure line of the compressor and in which the working fluid flows or is temporarily stored;
A supply pump provided between the storage tank and the flotation tank, for supplying the working fluid from the storage tank to the flotation tank;
A working fluid supply control device comprising a control valve provided between the storage tank and the flotation tank and for discharging the working fluid from the flotation tank to the storage tank.   When the pressure at the outlet of the precooler or the inlet of the compressor becomes high, the working fluid is discharged from the flotation tank to the storage tank, and when the pressure at the outlet of the precooler or the inlet of the compressor becomes low, The working fluid supply control device according to claim 11, wherein the working fluid is supplied from the storage tank to the flotation tank.   The working fluid supply control device according to claim 11 or 12, wherein the flotation tank is a piston accumulator type tank.   The flotation tank includes a tank body into which the working fluid flows, and a piston that is installed inside the tank body and moves up and down by a control fluid supplied from the outside. The working fluid supply control device according to Item.   The flotation tank is provided at a lower end of the tank main body, is provided with a control fluid inflow portion into which the control fluid flows in, and is provided at one side of the tank main body, and the working fluid flows in from the supply pump. The working fluid supply control device according to claim 14, further comprising an inlet and a first outlet provided on the other side of the tank main body and discharging the working fluid to the control valve.   The flotation tank is provided at an upper part of the tank body, and is provided at a second inlet through which the working fluid flows from the precooler, and at an upper part of the tank body, and the working fluid is discharged to the compressor. The working fluid supply control device according to claim 15, further comprising a second outlet. If the pressure P ₂ at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler is increased, the control and the control fluid is supplied to the fluid inlet, the first to open the control valve The working fluid supply control device according to claim 15 or 16, wherein the working fluid in the flotation tank is discharged to the storage tank through an outlet.   18. The working fluid supply control device according to claim 17, wherein the supply of the control fluid and the discharge of the working fluid to the storage tank are performed until the height of the piston reaches a height corresponding to a set value. . If the pressure P ₂ becomes lower at the front stage of the pressure P ₁ or the compressor at a subsequent stage of the pre-cooler, said working fluid through said first inlet by operating the supply pump to the flotation tank The working fluid supply control device according to any one of claims 15 to 18, which supplies the working fluid.   The working fluid supply control device according to claim 19, wherein the supply of the working fluid into the flotation tank is performed until a height of the piston reaches a height corresponding to a set value.