JP6687474B2 - Waste heat recovery equipment - Google Patents

Description

  The present application relates to a steam waste heat recovery device that re-evaporates high-temperature drain in a re-evaporation tank and reuses it.

  For example, Patent Document 1 discloses a steam waste heat recovery device that re-evaporates high-temperature drain in a re-evaporation tank and reuses it. The waste heat recovery apparatus of Patent Document 1 has a re-evaporation tank to which a drain supply pipe (condensate supply pipe) is connected, an ejector for steam, and an ejector for drain. The vapor ejector is connected to the upper surface of the re-evaporation tank via a pipe line, and the drain ejector is connected to the lower surface of the re-evaporation tank via a communication pipe. In this waste heat recovery device, the upper portion of the re-evaporation tank is in a vacuum pressure state due to the suction action of the ejector for steam. A part of the drain that has flowed into the re-evaporation tank from the drain supply pipe is re-evaporated and is sucked into the vapor ejector. The re-evaporated steam (flash steam) sucked by the steam ejector is supplied to the steam use location and reused. On the other hand, the rest of the drain that has flowed into the re-evaporation tank is sucked and discharged by the drain ejector.

JP, 2009-300011, A

  By the way, in the waste heat recovery apparatus as described above, instead of the drain ejector, a pump is provided to discharge the drain of the re-evaporation tank. However, in that case, the required suction head (NPSH: Net Positive Suction Head) of the pump is not satisfied, and there is a possibility that cavitation may occur in the pump.

  The technology disclosed in the present application has been made in view of such circumstances, and an object thereof is to prevent cavitation in a pump in a waste heat recovery device including a pump for discharging drain of a re-evaporation tank. To do.

  The waste heat recovery device of the present application includes a drain inflow pipe, a re-evaporation tank, a suction mechanism, and a drain discharge system. The re-evaporation tank is connected to the drain inflow pipe, and the drain flows in from the drain inflow pipe. The suction mechanism communicates with the upper portion of the re-evaporation tank and brings the inside of the re-evaporation tank into a predetermined vacuum pressure state by a suction action to re-evaporate the drain. The drain discharge system has a pump provided at a position lower than the re-evaporation tank, and is connected to a position higher than the connection position of the drain inflow pipe in the liquid layer portion of the re-evaporation tank, and the re-evaporation tank The drain of the above is discharged by the pump.

  According to the waste heat recovery device of the present application, since the drain discharge system is connected to a position higher than the connection position of the drain inflow pipe in the liquid layer portion of the re-evaporation tank, the drain flowing from the drain inflow pipe into the re-evaporation tank is connected. Drain having a lower temperature and pressure flows out of the re-evaporation tank. Since the drain discharge system pump is provided at a position lower than the re-evaporation tank, the drain flowing out from the re-evaporation tank can be sucked into the pump while being pressurized only by the pressure without changing the temperature. . That is, the drain having a temperature lower than the saturation temperature can be made to flow into the pump. This can prevent cavitation in the pump caused by drain re-evaporation.

FIG. 1 is a piping system diagram showing a schematic configuration of a waste heat recovery device according to an embodiment.

  Hereinafter, embodiments of the present application will be described with reference to the drawings. The following embodiments are essentially preferable exemplifications, and are not intended to limit the scope of the technology disclosed in the present application, its application, or its application.

  The waste heat recovery apparatus 1 of the present embodiment recovers the waste heat of the steam by re-evaporating and reusing the high temperature drain generated by condensation of the steam in the steam system. As shown in FIG. 1, the waste heat recovery device 1 includes a re-evaporation tank 10 (also called a flash tank), an ejector 13, and a drain discharge system 15.

  The re-evaporation tank 10 is a vertically long closed container that extends vertically and is connected with a drain inflow pipe 11. The high-temperature drain generated by the condensation of the steam in the steam system flows into the re-evaporation tank 10 via the drain inflow pipe 11. The drain inflow pipe 11 is provided below the re-evaporation tank 10 and is connected to the bottom portion (lower surface) of the re-evaporation tank 10.

  An ejector 13 is connected to the re-evaporation tank 10 via a steam discharge pipe 12. The vapor discharge pipe 12 is connected to the upper surface of the re-evaporation tank 10. The ejector 13 is provided in the steam pipe 14 in the steam system. The ejector 13 is configured such that a suction action is generated in the suction portion 13a when the steam flowing through the steam pipe 14 passes through. The steam discharge pipe 12 is connected to the suction portion 13 a of the ejector 13. The upper portion of the re-evaporation tank 10 is decompressed by the suction action of the ejector 13 (suction unit 13a) to be in a predetermined vacuum pressure state. The ejector 13 corresponds to the suction mechanism according to the claims of the present application.

  In the re-evaporation tank 10, the drain that has flowed in from the drain inflow pipe 11 is stored. Here, when the suction action of the ejector 13 is not generated, that is, when the inside of the re-evaporation tank 10 is in the atmospheric pressure state, the water surface of the drain in the re-evaporation tank 10 is the “reference water surface (at the atmospheric pressure)” shown in FIG. It is in. Then, when the suction action of the ejector 13 occurs and the upper portion of the re-evaporation tank 10 is in a vacuum pressure state, the water surface of the drain in the re-evaporation tank 10 is raised to the "normal water surface (during vacuum pressure)" shown in FIG.

  In the re-evaporation tank 10 in which the water surface of the drain has been raised in this manner, the drain is re-evaporated (flashes) on the water surface of the drain due to the reduced pressure to become steam (flash steam). In this way, the inside of the re-evaporation tank 10 is divided into a vapor gas layer portion 10a and a drain liquid layer portion 10b.

  The drain discharge system 15 is for discharging the drain of the re-evaporation tank 10. The drain discharge system 15 includes a pressure tank 17, a communication pipe 16, a drain discharge pipe 19, and a pump 20. The pressure tank 17 corresponds to the downstream tank according to the claims of the present application.

  The pressure tank 17 is a vertically long closed container that extends vertically and has substantially the same size and shape as the re-evaporation tank 10. The pressure tank 17 is provided at the same height as the re-evaporation tank 10. The communication pipe 16 is connected to the re-evaporation tank 10 and the pressure tank 17, and the drain of the re-evaporation tank 10 is configured to flow into the pressure tank 17. A steam discharge pipe 18 is connected to the upper surface of the pressure tank 17, and the steam discharge pipe 18 is connected to the middle of the steam discharge pipe 12. That is, the upper portion of the pressure tank 17 communicates with the suction portion 13 a of the ejector 13, and is in the same vacuum pressure state as the re-evaporation tank 10.

  In the pressure tank 17, the drain of the re-evaporation tank 10 flows in from the communication pipe 16 and is stored therein, and the water surface of the drain becomes the "normal water surface (at vacuum pressure)" shown in FIG. In the pressure tank 17, a part of the drain on the water surface of the drain re-evaporates to become vapor. In this way, the interior of the pressure tank 17 is divided into a vapor gas layer portion 17a and a drain liquid layer portion 17b. Both ends of the communication pipe 16 communicate with the liquid layer portion 10b of the re-evaporation tank 10 and the liquid layer portion 17b of the pressure tank 17. Specifically, both ends of the communication pipe 16 are located at the same height. That is, one end (inflow end) of the communication pipe 16 is connected to a position higher than the connection position of the drain inflow pipe 11 in the re-evaporation tank 10, and the interface between the gas layer portion 10 a and the liquid layer portion 10 b in the re-evaporation tank 10 is connected. It communicates with a slightly lower position. On the other hand, the other end (outflow end) of the communication pipe 16 communicates with a position slightly below the interface between the gas layer 17a and the liquid layer 17b in the pressure tank 17.

  Thus, the drain discharge system 15 is connected to the liquid layer portion 10b of the re-evaporation tank 10 at a position higher than the connection position of the drain inflow pipe 11. In the pressure tank, the drain of the re-evaporation tank 10 that has flowed in from the communication pipe 16 flows out to the drain discharge pipe 19 while being pressurized by the water level in the pressure tank 17. That is, the pressurizing tank 17 pressurizes the drain that has flowed in from the re-evaporation tank 10 without changing the temperature and causes it to flow out.

  A pump 20 is connected to the pressure tank 17 via a drain discharge pipe 19. Specifically, the drain discharge pipe 19 has one end connected to the bottom portion (lower surface) of the pressure tank 17 and the other end connected to the suction side of the pump 20. The pump 20 is provided below the re-evaporation tank 10, the pressure tank 17, and the drain inflow pipe 11. That is, on the suction side of the pump 20, a head (H1 + H2) that is a combination of a head H1 corresponding to the height from the reference water surface to the normal water surface and a head H2 corresponding to the height from the pump 20 to the reference water surface is pushed. Acting as pressure. The drain of the pressure tank 17 is sucked into the pump 20 via the drain discharge pipe 19. The drain sucked by the pump 20 is pressurized and supplied from the drain pressure-feeding pipe 21 to the drain use location.

<Driving operation>
The operation of the waste heat recovery device 1 described above will be described. Drain at a high temperature (for example, 100 ° C.) under atmospheric pressure flows into the re-evaporation tank 10 through the drain inflow pipe 11. The drain flowing into the re-evaporation tank 10 is decompressed as it rises, and when it rises to the normal water level, the pressure becomes a predetermined vacuum pressure (for example, -20 kPaG) that is the pressure of the gas layer portion 10a. Strictly speaking, the drainage is normally evaporated by the reduced pressure even while rising to the water surface, and reaches a saturation temperature corresponding to the pressure. Normally, the drain that has risen to the water surface evaporates and becomes vapor at a saturation temperature (for example, 94 ° C.) corresponding to the vacuum pressure. On the other hand, the drain that cannot be completely evaporated remains as the drain at the saturation temperature corresponding to the vacuum pressure. That is, the drain near the water surface of the liquid layer portion 10b has a lower pressure and temperature than the drain flowing into the re-evaporation tank 10 from the drain inflow pipe 11. The drain at the saturation temperature (94 ° C.) corresponding to the vacuum pressure flows into the pressure tank 17 via the communication pipe 16.

  The drain of the saturation temperature corresponding to the vacuum pressure flowing into the pressurization tank 17 is pressurized by the water level as it goes downward. That is, the pressure of the drain rises from a predetermined vacuum pressure. When the drain reaches the reference water surface in the pressure tank 17, the pressure of the drain rises to the atmospheric pressure. At this time, the temperature of the drain remains unchanged at the saturation temperature (94 ° C.) corresponding to the vacuum pressure. Therefore, the drain flowing from the re-evaporation tank 10 into the pressurizing tank 17 is pressurized to the atmospheric pressure state, becomes a drain whose temperature remains at the saturation temperature corresponding to the vacuum pressure, and flows out to the drain discharge pipe 19. It is sucked into the pump 20.

  The pressure of the drain sucked into the pump 20 is atmospheric pressure, and the temperature is 94 ° C. which is lower than the saturation temperature (100 ° C.) corresponding to the atmospheric pressure. Therefore, the drain is re-evaporated in the pump 20. It can be surely prevented. Therefore, in the pump 20, cavitation caused by re-evaporation of drain can be prevented.

  As described above, according to the waste heat recovery apparatus 1 of the above embodiment, the drain discharge system 15 is connected to the liquid layer portion 10b of the re-evaporation tank 10 at a position higher than the connection position of the drain inflow pipe 11. . Therefore, the drain having a lower temperature and pressure than the drain flowing into the re-evaporation tank 10 from the drain inflow pipe 11 flows out from the re-evaporation tank 10 to the drain discharge system 15. Then, in the waste heat recovery system 1 of the above-described embodiment, the pump 20 of the drain discharge system 15 is provided at a position lower than the re-evaporation tank 10. Therefore, the drain flowing out from the re-evaporation tank 10 is sucked into the pump 20 while being pressurized to a pressure higher than the atmospheric pressure (pressure of the drain flowing into the re-evaporation tank 10 from the drain inflow pipe 11) without changing the temperature. Can be made. That is, the drain having a temperature lower than the saturation temperature can flow into the pump 20. This can prevent cavitation in the pump 20 caused by re-evaporation of drain.

  Further, the waste heat recovery apparatus 1 of the above-described embodiment is provided with the pressure tank 17 in which the drain flows from the re-evaporation tank 10 in the drain discharge system 15. Therefore, the drainage flowing out from the re-evaporation tank 10 can be reliably stored in the pressure tank 17. As a result, the behavior of the drain can be stabilized in the pressure tank 17, and the drain can be reliably pressurized by the stored water level. Therefore, the above-mentioned cavitation can be prevented more reliably.

  Further, in the waste heat recovery apparatus 1 of the above embodiment, the drain inflow pipe 11 is connected to the lower surface of the re-evaporation tank 10, and one end of the communication pipe 16 (that is, one end of the drain discharge system 15) is connected to the gas in the re-evaporation tank 10. The connection was made near the interface between the layer portion 10a and the liquid layer portion 10b (that is, near the water surface in the re-evaporation tank 10). Thus, the drain of the saturation temperature corresponding to the predetermined vacuum pressure in the re-evaporation tank 10, that is, the drain of the lowest temperature in the re-evaporation tank 10 can be discharged from the re-evaporation tank 10 to the drain discharge system 15. Therefore, the drain having a temperature lower than the saturation temperature can be surely sucked into the pump 20.

(Other embodiments)
In the waste heat recovery device 1 of the present application, the connection position of the drain inflow pipe 11 and the communication pipe 16 (drain discharge system 15) in the re-evaporation tank 10 is not limited to the position described in the above embodiment. For example, the drain inflow pipe 11 may be connected to the lower side surface of the re-evaporation tank 10, or the communication pipe 16 may be connected to an intermediate position of the liquid layer portion 10b. That is, in the waste heat recovery apparatus 1 of the present application, the connection position of the communication pipe 16 (drain discharge system 15) in the liquid layer portion 10b of the re-evaporation tank 10 may be higher than the connection position of the drain inflow pipe 11.

  Further, in the drain discharge system 15 of the above embodiment, the communication pipe 16 and the pressure tank 17 may be omitted, and the drain discharge pipe 19 may be extended and directly connected to the re-evaporation tank 10. That is, in the drain discharge system 15 of the present application, the re-evaporation tank 10 and the pump 20 may be connected by a normal pipe. In this case, the connection position between the re-evaporation tank 10 and the drain discharge pipe 19 is higher than the connection position between the re-evaporation tank 10 and the drain inflow pipe 11.

  Further, in the waste heat recovery device 1 of the above embodiment, a suction mechanism other than the ejector 13 may be used.

  INDUSTRIAL APPLICABILITY The technique disclosed in the present application is useful for a steam waste heat recovery device that re-evaporates high-temperature drain in a re-evaporation tank and reuses it.

1 Waste Heat Recovery Device 10 Re-evaporation Tank 10a Gas Layer 10b Liquid Layer 11 Drain Inflow Pipe 13 Ejector (Suction Mechanism)
15 Drain discharge system 16 Communication pipe 17 Pressurized tank (downstream tank)
19 Drain discharge pipe 20 Pump

Claims (3)

Drain drain pipe,
A re-evaporation tank, to which the drain inflow pipe is connected, into which drain flows from the drain inflow pipe,
A suction mechanism that communicates with the upper portion of the re-evaporation tank and re-evaporates the drain by a suction action to bring the inside of the re-evaporation tank into a predetermined vacuum pressure state;
While having a pump provided at a position lower than the re-evaporation tank, connected to a position higher than the connection position of the drain inflow pipe in the liquid layer portion of the re-evaporation tank, the drain of the re-evaporation tank by the pump A waste heat recovery device comprising a drain discharge system for discharging the waste heat. The waste heat recovery device according to claim 1,
The drain discharge system is
A downstream tank,
One end is connected to a position higher than the connection position of the drain inflow pipe in the liquid layer portion of the re-evaporation tank, the other end is connected to the downstream side tank, and the drain of the re-evaporation tank flows into the downstream side tank. Communication pipe to
A waste heat recovery device comprising: a drain discharge pipe having one end connected to the liquid layer portion of the downstream tank and the other end connected to the pump. The waste heat recovery device according to claim 2,
The drain inflow pipe is connected to the lower surface of the re-evaporation tank,
The waste heat recovery device, wherein one end of the communication pipe is connected to the vicinity of the interface between the gas layer portion and the liquid layer portion in the re-evaporation tank.

Images