Heat Recovery System

Abstract

To suppress water seal breakage of a header tank due to an inflow operation of a liquid pumping device.SOLUTION: A heat recovery system 100 comprises: a water-sealed header tank 2; a liquid pumping device 5 that performs an inflow operation of discharging steam in a storage chamber from an exhaust port to flow the drain of the header tank 2 into the storage chamber, and a pumping operation of introducing steam into the storage chamber to pump the drain in the storage chamber; a route switching unit 6 that has a first exhaust pipe 61 provided with a first check valve 63 and communicating with the exhaust port and the header tank 2, and a second exhaust pipe 62 provided with a second check valve 64 and communicating with the exhaust port and a heat exchanger 4, and that during the inflow operation, selectively switches the first exhaust pipe 61 and the second exhaust pipe 62 according to the exhaust pressure of the steam. The first check valve 63 has a valve body that is displaced vertically upward by the exhaust pressure to close the valve when the exhaust pressure is equal to or larger than a predetermined value, and is displaced vertically downward by its own weight to open the valve when the exhaust pressure is less than the predetermined value. The second check valve 64 has a valve body that opens the valve when the exhaust pressure is equal to or larger than a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The disclosed technology relates to heat recovery systems. [Background technology]

[0002] As a heat recovery system, for example, as disclosed in Patent Document 1, a drain recovery device is known that recovers drain generated by condensation of steam in steam-using equipment in a header tank. This drain recovery device includes a liquid pressure-feeding device that supplies drain from the header tank to the user side. The liquid pressure-feeding device alternates between drain inflow and pressure-feeding. In the drain inflow operation, drain from the header tank flows in and is stored in the storage chamber, and steam from the storage chamber is discharged. In the drain pressure-feeding operation, high-pressure steam is introduced into the storage chamber, so that drain from the storage chamber is pressure-feed to the user side. In addition, in the drain inflow operation, steam from the storage chamber is discharged into the header tank. In this way, the header tank and the storage chamber are pressure-equalized, and rapid gas-liquid replacement (replacement of drain and steam) is performed between the two. Therefore, the inflow operation can be performed quickly. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 056481 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, as the header tank described above, a so-called water-sealed tank, which is provided with a water seal trap to prevent steam leakage, is often used. In that case, however, the following problem may occur in the heat recovery system described above. During the drain inflow operation, the steam discharged from the liquid pumping device to the header tank is at a relatively high pressure, so that the impact force of the exhaust steam acts on the header tank, and there is a risk that the water seal of the water seal trap will be broken by the impact force. If the water seal is broken, steam will leak from the header tank. In particular, at the beginning of the inflow operation, the pressure of the exhaust steam is high, so the water seal breakage of the header tank described above is noticeable.

[0005] The technology disclosed herein has been made in consideration of the above circumstances, and its purpose is to provide a heat recovery system that can suppress the breakdown of the water seal in the header tank caused by the inflow operation of the liquid pumping device. [Means for solving the problem]

[0006] The heat recovery system of the present disclosure includes a water-sealed header tank, a liquid pressure-feeding device, and a path switching unit. Drain generated by a steam-using device flows into the header tank and is stored therein. The liquid pressure-feeding device has a casing in which a drain storage chamber and a steam exhaust port are formed, and performs an inflow operation of causing the drain in the header tank to flow into the storage chamber and store the drain by discharging steam from the storage chamber through the exhaust port, and a pressure-feed operation of pressure-feeding the drain in the storage chamber by introducing steam into the storage chamber. The path switching unit has a first exhaust pipe provided with a first check valve and communicating with the exhaust port and the header tank, and a second exhaust pipe provided with a second check valve and communicating with the exhaust port and a location other than the header tank, and selectively switches between the first exhaust pipe and the second exhaust pipe according to an exhaust pressure, which is the pressure of the steam discharged from the exhaust port, during the inflow operation. The first check valve has a valve body that is displaced vertically upward by the exhaust pressure to close when the exhaust pressure becomes equal to or greater than a predetermined value, and that is displaced vertically downward by its own weight to open when the exhaust pressure becomes less than the predetermined value. The second check valve has a valve body that opens when the exhaust pressure becomes equal to or greater than a predetermined value. Effect of the Invention

[0007] According to the heat recovery system of the present disclosure, it is possible to suppress the breakage of the water seal in the header tank caused by the inflow operation of the liquid pumping device. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a piping diagram showing a schematic configuration of a heat recovery system according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the gas-liquid separation section. [Diagram 3] FIG. 3 is a cross-sectional view showing a schematic configuration of the liquid pressure-feeding device. [Figure 4] FIG. 4 is a cross-sectional view showing a schematic configuration of the first check valve and the second check valve. [Diagram 5] FIG. 5 is a view corresponding to FIG. 4, showing one state of the first check valve and the second check valve. [Figure 6] FIG. 6 is a piping diagram showing a schematic configuration of the heat recovery system. [Figure 7] FIG. 7 is a diagram corresponding to FIG. 1, showing a heat recovery system according to the first modification with a part thereof omitted. [Figure 8] FIG. 8 is a view corresponding to FIG. 4, showing the first check valve and the second check valve according to the second modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present application will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the technology disclosed in the present application, its applications, or its uses.

[0010] The heat recovery system 100 of the present embodiment recovers drain generated by condensation of steam in steam-using equipment and flash steam (steam, etc.) from the drain. That is, the heat recovery system 100 recovers heat from the high-temperature drain and the flash steam.

[0011] As shown in FIG. 1, the heat recovery system 100 includes a gas-liquid separation section 1, a header tank 2, a heat exchanger 4, a liquid pressure-feeding device 5, and a path switching section 6.

[0012] The gas-liquid separation section 1 separates drain sent from a steam-using device (not shown) and its flash steam. The gas-liquid separation section 1 has a recovery pipe 10, a liquid pipe 11, and a gas pipe 12.

[0013] Drain and flash steam generated in the steam-using equipment flow into the recovery pipe 10. The liquid pipe 11 and the gas pipe 12 are branch pipes formed by the recovery pipe 10 branching into two. Of the drain and flash steam that flow into the recovery pipe 10, the drain flows into the liquid pipe 11 and the flash steam flows into the gas pipe 12. The gas pipe 12 is a straight pipe extending vertically upward from the end of the recovery pipe 10. The gas pipe 12 is connected to the heat exchanger 4 and supplies flash steam to the heat exchanger 4. The liquid pipe 11 extends downward from the end of the recovery pipe 10. The liquid pipe 11 is connected to the header tank 2 and causes the drain to flow into the header tank 2.

[0014] As shown in FIG. 2, the liquid pipe 11 is a so-called U-shaped pipe that is bent in a U-shape. Specifically, the liquid pipe 11 has a first pipe 11a, a second pipe 11b, a third pipe 11c, and a fourth pipe 11d. The first pipe 11a is a straight pipe that extends vertically downward from the end of the recovery pipe 10. The second pipe 11b is a straight pipe that extends horizontally from the lower end of the first pipe 11a, and is a part that corresponds to the bottom of the U-shape. The third pipe 11c is a straight pipe that extends vertically upward from the end of the second pipe 11b. In other words, the first pipe 11a and the third pipe 11c extend vertically in parallel to each other. The fourth pipe 11d is a straight pipe that extends horizontally from the upper end of the third pipe 11c. The fourth pipe 11d is connected to the side of the header tank 2 (more specifically, the tank body 21).

[0015] In the liquid pipe 11 thus configured, drain is retained in the first pipe 11a, the second pipe 11b, and the third pipe 11c, and the retained drain is water-sealed. More specifically, in the third pipe 11c, drain is retained up to the upper end, while in the first pipe 11a, the head of the drain is lower than the head of the drain in the third pipe 11c. That is, a head difference H of the drain occurs between the first pipe 11a and the third pipe 11c. This head difference H occurs due to the pressure loss in the heat exchanger 4. The pressure loss of the heat exchanger 4 is offset by the head difference H thus generated. The first pipe 11a and the third pipe 11c are set to a sufficient height to ensure the head difference H equivalent to the pressure loss of the heat exchanger 4. Therefore, the pressure loss of the heat exchanger 4 can be reliably offset. This allows the flash steam to easily flow from the gas pipe 12 into the heat exchanger 4.

[0016] The header tank 2 is a water-sealed header tank into which drainage generated in steam-using equipment flows and is stored. Specifically, the header tank 2 has a container-shaped tank body 21 and an overflow pipe 24.

[0017] The tank body 21 has an internal space divided into a liquid phase section 22 of drain and a gas phase section 23 of steam. The tank body 21 is connected to a liquid pipe 11 (fourth pipe 11d), an outflow pipe 13, and an inflow pipe 16a. The liquid pipe 11 opens into the gas phase section 23. The outflow pipe 13 is connected to the top of the tank body 21 and opens into the gas phase section 23. The inflow pipe 16a opens into the liquid phase section 22. The tank body 21 receives drain from the liquid pipe 11 and stores it there. The tank body 21 also receives drain from the heat exchanger 4 via the outflow pipe 13 and stores it there. The tank body 21 also receives drain from the liquid phase section 22 via the inflow pipe 16a and stores it there. One end of the overflow pipe 24, which is an inflow end, opens into the liquid phase section 22, and the other end, which is an outflow end, penetrates the upper side wall of the tank body 21 and opens to the atmosphere.

[0018] The internal space of the tank body 21 is sealed by the water seal of the water seal trap 3. Specifically, the water seal trap 3 is connected to the tank body 21 by the connecting pipe 15a and the outflow pipe 15b. One end of the connecting pipe 15a, which is the inflow end, opens to the gas phase part 23 of the tank body 21, and the other end, which is the outflow end, opens to the seal water of the water seal trap 3. In other words, the other end of the connecting pipe 15a is water sealed. One end of the outflow pipe 15b, which is the inflow end, is connected to the water seal trap 3, and the other end, which is the outflow end, opens to the liquid phase part 22 of the tank body 21. The water seal trap 3 normally prevents the steam of the tank body 21 from leaking out by the water seal, while in an emergency in which the tank body 21 becomes abnormally high pressure, the water seal is broken and the steam of the tank body 21 is released to the atmosphere. In addition, in the water seal trap 3, excess drainage generated by condensation of steam flows into the tank body 21 through the outflow pipe 15b and is stored therein.

[0019] The heat exchanger 4 has a first flow path 41 and a second flow path 42, which are internal flow paths. The first flow path 41 is a heat exchange flow path into which the flash steam of drain flowing from the steam-using equipment into the header tank 2 flows and exchanges heat with the object of the second flow path 42 (for example, water). More specifically, the gas pipe 12 is connected to the inlet end of the first flow path 41, and the outlet pipe 13 is connected to the outlet end of the first flow path 41. The second flow path 42 is connected to an inlet pipe 14a for supplying water and an outlet pipe 14b through which water flows out from the second flow path 42. In the heat exchanger 4, the flash steam of the first flow path 41 exchanges heat with the water of the second flow path 42, and the water is heated. The flash steam is condensed to become drain and flows into the header tank 2 via the outlet pipe 13. In this way, the heat of the flash steam is recovered.

[0020] As shown in FIG. 3, the liquid pumping device 5 has a casing 50 in which a drain storage chamber 51 and a steam exhaust port 55 are formed, and performs an inflow operation in which the drain of the header tank 2 flows into the storage chamber 51 and is stored therein by discharging the steam in the storage chamber 51 from the exhaust port 55, and a pumping operation in which the drain of the storage chamber 51 is pumped by introducing steam into the storage chamber 51.

[0021] Specifically, the liquid pumping device 5 alternates between an inflow operation and a pumping operation. During the pumping operation, the steam introduced into the storage chamber 51 is a working gas, and is high-temperature, high-pressure steam. The liquid pumping device 5 includes a casing 50 which is a sealed container, an intake valve 56, an exhaust valve 57, and a valve operating mechanism 58.

[0022] The casing 50 is formed by connecting a main body 50a and a lid 50b with bolts, and a drain storage chamber 51 is formed inside. The lid 50b is provided with an inlet 52 through which drain flows in, a pressure delivery port 53 through which drain is pressure-delivered, an air supply port 54 through which working gas is supplied, and an exhaust port 55 through which working gas is discharged. All of these inlets 52 and the like are provided in the lid 50b and communicate with the storage chamber 51. The inlet 52 is connected to the inlet pipe 16a, the pressure delivery port 53 is connected to the pressure delivery pipe 16b, the air supply port 54 is connected to the air supply pipe 16c, and the exhaust port 55 is connected to the exhaust pipe 16d. The air supply pipe 16c supplies high-pressure steam generated, for example, by a boiler in the steam system to the air supply port 54. The pressure delivery pipe 16b supplies the drain from the pressure delivery port 53 to a predetermined usage point. This allows the heat of the high-temperature drain to be recovered.

[0023] The air inlet valve 56 is provided in the air inlet 54 and opens and closes the air inlet 54. The exhaust valve 57 is provided in the exhaust port 55 and opens and closes the exhaust port 55. A valve operating rod 57a is connected to the lower part of the exhaust valve 57. A connecting plate 57b extending to the lower area of ​​the air inlet valve 56 is attached to the valve operating rod 57a. With this configuration, when the valve operating rod 57a rises, the air inlet valve 56 opens the air inlet 54, while the exhaust valve 57 closes the exhaust port 55. When the valve operating rod 57a descends, the air inlet valve 56 closes the air inlet 54, while the exhaust valve 57 opens the exhaust port 55.

[0024] The valve operating mechanism 58 is provided inside the casing 50, and moves a valve operating rod 57a up and down to operate the intake valve 56 and the exhaust valve 57. The valve operating mechanism 58 has a float 581 and a snap mechanism 59.

[0025] The float 581 is formed in a spherical shape, and a lever 582 is attached to the float 581. The lever 582 is rotatably supported by a shaft 583 provided on a bracket 584. A shaft 585 is provided on the lever 582 at the end opposite to the float 581 side. The snap mechanism 59 has a float arm 591, a sub-arm 592, a coil spring 593, and two receiving members 594a and 594b. One end of the float arm 591 is rotatably supported by a shaft 596 provided on a bracket 597. A groove 591a is formed on the other end of the float arm 591, and a shaft 585 of the lever 582 is fitted into the groove 591a. With this configuration, the float arm 591 swings around the shaft 596 as the float 581 rises and falls.

[0026] In addition, a shaft 595a is provided on the float arm 591. The upper end of the sub-arm 592 is rotatably supported by a shaft 596, and a shaft 595b is provided on the lower end. The receiving member 594a is rotatably supported by the shaft 595a of the float arm 591, and the receiving member 594b is rotatably supported by the shaft 595b of the sub-arm 592. A coil spring 593 in a compressed state is attached between the receiving members 594a, 594b. In addition, a shaft 598 is provided on the sub-arm 592, and the lower end of the valve operating rod 57a is connected to the shaft 598.

[0027] In the liquid pressure-feeding device 5, when no drain is stored in the storage chamber 51, the float 581 is located at the bottom of the storage chamber 51. In this state, the valve operating rod 57a is lowered, the intake valve 56 is closed, and the exhaust valve 57 is open. As the drain flows in from the inlet 52 and accumulates in the storage chamber 51, the float 581 rises. Meanwhile, in the storage chamber 51, as the drain accumulates, steam is discharged from the exhaust port 55. In this way, the inflow operation is performed. That is, the drain and steam are replaced in the inflow operation. When the water level of the drain in the storage chamber 51 reaches a predetermined high water level, the valve operating rod 57a is raised by the snap mechanism 59. As a result, the intake valve 56 opens and the exhaust valve 57 closes.

[0028] When the intake valve 56 opens, steam (high pressure steam) is supplied from the intake port 54 and introduced into the upper part of the storage chamber 51 (the space above the drain). The drain stored in the storage chamber 51 is then pushed downward by the pressure of the introduced steam and pumped out from the pumping port 53. In this way, the pumping operation is performed. When the drain water level in the storage chamber 51 drops due to this pumping operation, the float 581 descends. Then, when the drain water level in the storage chamber 51 reaches a predetermined low water level, the valve operating rod 57a descends due to the snap mechanism 59. This causes the intake valve 56 to close and the exhaust valve 57 to open.

[0029] The path switching unit 6 has a first exhaust pipe 61 provided with a first check valve 63 and communicating with the exhaust port 55 and the header tank 2, and a second exhaust pipe 62 provided with a second check valve 64 and communicating with the exhaust port 55 and a first flow path 41 of a heat exchanger 4 separate from the header tank 2, and selectively switches between the first exhaust pipe 61 and the second exhaust pipe 62 in response to an exhaust pressure that is the pressure of steam discharged from the exhaust port 55 during an inflow operation of the liquid pressure-feeding device 5. In other words, the path switching unit 6 switches the path of the steam discharged from the exhaust port 55 during an inflow operation of the liquid pressure-feeding device 5.

[0030] Specifically, the path switching unit 6 has a first exhaust pipe 61 in which a first check valve 63 is provided, and a second exhaust pipe 62 in which a second check valve 64 is provided.

[0031] One end of the first exhaust pipe 61, which is an inflow end, is connected to the exhaust port 55, and the other end, which is an outflow end, is connected to the header tank 2. The first check valve 63 is provided midway through the first exhaust pipe 61. One end, which is an inflow end, of the second exhaust pipe 62 is connected to the first exhaust pipe 61 on the exhaust port 55 side (i.e., upstream side) of the first check valve 63. The other end, which is an outflow end, of the second exhaust pipe 62 is connected to the gas pipe 12. That is, one end of the second exhaust pipe 62 communicates with the exhaust port 55 via the first exhaust pipe 61, and the other end of the second exhaust pipe 62 communicates with the first flow path 41 of the heat exchanger 4 via the gas pipe 12.

[0032] As shown in Figs. 4 and 5, the first check valve 63 has a valve seat 631 and a valve body 632. When the exhaust pressure is equal to or greater than a predetermined value, the valve body 632 is displaced vertically upward by the exhaust pressure to close (see Fig. 5), whereas when the exhaust pressure is less than the predetermined value, the valve body 632 is displaced vertically downward by its own weight to open (see Fig. 4). More specifically, the valve body 632 is provided so as to be displaceable in the vertical direction. When the exhaust pressure is equal to or greater than a predetermined value, the valve body 632 is pushed up against its own weight to seat on the valve seat 631. When the exhaust pressure is less than the predetermined value, the valve body 632 drops by its own weight to separate from the valve seat 631. In this way, when the exhaust pressure is equal to or greater than a predetermined value, the first check valve 63 closes to prevent steam from flowing into the header tank 2 from the exhaust port 55. Furthermore, the first check valve 63 opens when the exhaust pressure falls below a predetermined value, allowing steam to flow from the exhaust port 55 into the header tank 2 .

[0033] The second check valve 64 has a valve seat 641 and a valve body 642. The valve body 642 opens when the exhaust pressure is equal to or greater than a predetermined value, and closes when the exhaust pressure is less than the predetermined value. More specifically, the valve body 642 is provided so as to be displaceable in the vertical direction. When the exhaust pressure is equal to or greater than a predetermined value, the valve body 642 is pushed up against its own weight and leaves the valve seat 641 (see FIG. 5). This opens the valve body 642. When the exhaust pressure is less than the predetermined value, the valve body 642 falls under its own weight and seats on the valve seat 641 (see FIG. 4). This closes the valve body 642. In this way, the second check valve 64 opens when the exhaust pressure is equal to or greater than a predetermined value, and allows steam to flow from the exhaust port 55 to the heat exchanger 4 (first flow path 41). Moreover, the second check valve 64 closes when the exhaust pressure falls below a predetermined value, preventing steam from flowing into the heat exchanger 4 (first flow path 41) from the exhaust port 55. The predetermined value is set to a value of the exhaust pressure at which the water seal of the water seal trap 3 is broken during the inflow operation of the liquid pumping device 5.

[0034] In the path switching unit 6 configured as above, when the pressure of the steam discharged from the exhaust port 55 (i.e., exhaust pressure) is equal to or higher than a predetermined value during the inflow operation of the liquid pressure-feeding device 5, the first check valve 63 closes to shut off the first exhaust pipe 61, while the second check valve 64 opens to open the second exhaust pipe 62. Then, as shown in Fig. 6, the steam discharged from the exhaust port 55 to the first exhaust pipe 61 flows through the second exhaust pipe 62 and the gas pipe 12 into the heat exchanger 4. In other words, in the path switching unit 6, high-pressure steam equal to or higher than a predetermined value is prevented from being supplied to the header tank 2, and the heat of the steam is recovered by the heat exchanger 4.

[0035] In addition, in the path switching unit 6, when the pressure of the steam discharged from the exhaust port 55 (i.e., exhaust pressure) falls below a predetermined value during the inflow operation of the liquid pressure-feeding device 5, the second check valve 64 closes to block the second exhaust pipe 62, while the first check valve 63 opens to open the first exhaust pipe 61. Then, as shown in FIG. 1, the steam discharged from the exhaust port 55 flows into the header tank 2 via the first exhaust pipe 61. This equalizes the pressure between the tank body 21 and the storage chamber 51, and gas-liquid replacement (i.e., replacement of drain with steam) is performed between them. Therefore, drain flows smoothly from the header tank 2 into the liquid pressure-feeding device 5.

[0036] As described above, the heat recovery system 100 of the embodiment includes the water-sealed header tank 2, the liquid pumping device 5, and the path switching unit 6. The header tank 2 receives and stores drainage generated by steam-using equipment. The liquid pumping device 5 has a casing 50 in which a drainage storage chamber 51 and a steam exhaust port 55 are formed, and performs an inflow operation of causing drainage from the header tank 2 to flow into and be stored in the storage chamber 51 by discharging steam from the storage chamber 51 through the exhaust port 55, and a pumping operation of pumping the drainage from the storage chamber 51 by introducing steam into the storage chamber 51. The path switching unit 6 has a first exhaust pipe 61 provided with a first check valve 63 and communicating with the exhaust port 55 and the header tank 2, and a second exhaust pipe 62 provided with a second check valve 64 and communicating with the exhaust port 55 and a first flow path 41 of a heat exchanger 4 other than the header tank 2, and selectively switches between the first exhaust pipe 61 and the second exhaust pipe 62 according to the exhaust pressure, which is the pressure of the steam discharged from the exhaust port 55, during the inflow operation. The first check valve 63 has a valve body 632 that displaces vertically upward due to the exhaust pressure to close when the exhaust pressure becomes equal to or greater than a predetermined value, and displaces vertically downward due to its own weight to open when the exhaust pressure becomes less than the predetermined value. The second check valve 64 has a valve body 642 that opens when the exhaust pressure becomes equal to or greater than a predetermined value.

[0037] According to the above configuration, during the inflow operation of the liquid pumping device 5, it is possible to prevent high pressure steam equal to or higher than a predetermined value from being supplied to the header tank 2. Therefore, it is possible to prevent the water seal of the header tank 2 (i.e., the water seal of the water seal trap 3) from being broken by the steam discharged from the exhaust port 55. Furthermore, during the inflow operation of the liquid pumping device 5, if the pressure of the steam discharged from the exhaust port 55 drops to a pressure that has no effect, the steam is supplied to the header tank 2. Therefore, gas-liquid exchange can be performed between the header tank 2 and the liquid pumping device 5, and drain can smoothly flow from the header tank 2 to the liquid pumping device 5.

[0038] The heat recovery system 100 of the embodiment further includes a heat exchanger 4 having a first flow path 41 (heat exchange flow path) through which flush steam of drain flowing from the steam-using equipment into the header tank 2 flows and exchanges heat with an object. The second exhaust pipe 62 is connected to the first flow path 41 separate from the header tank 2.

[0039] According to the above-mentioned configuration, the heat of the high-pressure steam discharged from the exhaust port 55 can be recovered by the heat exchanger 4 .

[0040] First Modification of the Embodiment The present modified example 1 is obtained by modifying the configuration of the path switching unit 6 in the above embodiment. Specifically, the path switching unit 6 of the present modified example further includes a bypass pipe 65, as shown in FIG.

[0041] The bypass pipe 65 is formed with an inner diameter smaller than that of the first exhaust pipe 61. The bypass pipe 65 is connected to the first exhaust pipe 61. The bypass pipe 65 is a pipe that bypasses the first check valve 63. In this path switching unit 6, for example, even if the pressure loss of the heat exchanger 4 is large and the first check valve 63 cannot be opened, that is, even if both the first check valve 63 and the second check valve 64 remain closed despite the exhaust pressure being equal to or higher than a predetermined value, the bypass pipe 65 can allow the inflow of steam from the exhaust port 55 to the header tank 2. Since the inner diameter of the bypass pipe 65 is smaller than that of the first exhaust pipe 61, the amount of steam supplied to the header tank 2 is appropriately suppressed, and therefore no impact force that would affect the water seal of the water seal trap 3 is generated. In this manner, in this modified example, even if both the first check valve 63 and the second check valve 64 are closed during the inflow operation of the liquid pumping device 5, a minimum amount of gas-liquid exchange can be performed between the header tank 2 and the liquid pumping device 5.

[0042] Second Modification of the Embodiment In this modified example 2, the configuration of the first check valve 63 of the path switching unit 6 is changed from that of the above embodiment. Specifically, as shown in Fig. 8, a small hole 633 penetrating in the upstream and downstream directions is formed in the valve body 632 of the first check valve 63.

[0043] In this path switching unit 6, even if both the first check valve 63 and the second check valve 64 remain closed despite the exhaust pressure being equal to or higher than a predetermined value as described above, steam from the exhaust port 55 can be supplied to the header tank 2 through the small hole 633 of the valve body 632. Furthermore, because the small hole 633 appropriately restricts the amount of steam supplied to the header tank 2, no impact force is generated that would affect the water seal of the water seal trap 3. Thus, in this modified example as well, a minimum amount of gas-liquid exchange can be performed between the header tank 2 and the liquid pumping device 5, even if both the first check valve 63 and the second check valve 64 close during the inflow operation of the liquid pumping device 5. [Industrial Applicability]

[0044] As described above, the technology of the present disclosure is useful for a heat recovery system. [Explanation of symbols]

[0045] 100 Heat Recovery System 2 Header Tank 4 Heat exchanger 5. Liquid pumping device 6 Route switching section 41 First flow path (heat exchange flow path) 50 Casing 51 Storage chamber 55 Exhaust port 61 First exhaust pipe 62 Second exhaust pipe 63 First check valve 632 Valve body 633 Small hole 64 Second check valve 642 Valve body 65 Bypass pipe

Claims

1. A water-sealed header tank into which drainage generated by steam-using equipment flows and is stored; a liquid pumping device having a casing in which a drain storage chamber and a steam exhaust port are formed, the liquid pumping device performing an inflow operation of causing drain of the header tank to flow into the storage chamber and be stored therein by discharging steam in the storage chamber from the exhaust port, and a pumping operation of pumping the drain of the storage chamber by introducing steam into the storage chamber; a first exhaust pipe provided with a first check valve and communicating with the exhaust port and the header tank, a second exhaust pipe provided with a second check valve and communicating with the exhaust port and a location other than the header tank, and a path switching unit that selectively switches between the first exhaust pipe and the second exhaust pipe in response to an exhaust pressure that is a pressure of steam discharged from the exhaust port during the inflow operation, the first check valve has a valve body that is displaced vertically upward by the exhaust pressure to close when the exhaust pressure becomes equal to or greater than a predetermined value, and that is displaced vertically downward by its own weight to open when the exhaust pressure becomes less than the predetermined value, The second check valve has a valve body that opens when the exhaust pressure reaches a predetermined value or higher. A heat recovery system comprising:

2. 2. The heat recovery system according to claim 1, The heat exchanger further includes a heat exchange passage through which flush steam of drain flowing from the steam-using equipment into the header tank flows and exchanges heat with an object, The second exhaust pipe is in communication with the heat exchange passage other than the header tank. A heat recovery system comprising:

3. In the heat recovery system according to claim 1 or 2, The path switching unit has an inner diameter smaller than that of the first exhaust pipe, and includes a bypass pipe connected to the first exhaust pipe to bypass the first check valve. A heat recovery system comprising:

4. In the heat recovery system according to claim 1 or 2, The first check valve has a valve body having a small hole passing therethrough in the upstream and downstream directions. A heat recovery system comprising:

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