JP2019190803A - Drain recovery system - Google Patents

Abstract

To provide a drain recovery system which can inhibit occurrence of cavitation when water is supplied from an open tank to a boiler etc.SOLUTION: According to the invention, a drain recovery system 1 recovers drain generated by condensed steam that occurred in a boiler 2 and was used in a load device 4 to supply the drain to the boiler 2. The drain recovery system includes: an open type open tank 6 which recovers the drain generated in the load device 4 as makeup water; circulation means 7 which circulates the makeup water in the open tank 6; temperature detection means 91 which detects a temperature of the makeup water in the open tank 6; a drain return line L6 connecting the load device 4 to the open tank 6; a drain discharge line L10 branched from the drain return line L6; and control means 9 which stops circulation operation conducted by the circulation means 7 when a detected temperature T of the temperature detection means 91 exceeds a first setting temperature T1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drain recovery system that recovers drain discharged from a load device and supplies the drain to a boiler.

  Conventionally, a drain recovery system has been proposed in which drain generated by condensing steam supplied to a load device is recovered in a tank and supplied again to a boiler. For example, Patent Document 1 discloses a drain that condenses and recovers drain by circulating makeup water in an open tank (open tank) by circulation means and mixing it with drain (steam) flowing into the open tank. A collection device is disclosed.

JP-A-9-53804

  However, depending on the drain (steam) returning to the open tank, the makeup water stored in the open tank may become high temperature, which may cause cavitation in the water supply path to the boiler or the like.

  This invention is made | formed in view of such a situation, and it aims at providing the drain recovery system which can suppress generation | occurrence | production of the cavitation at the time of supplying water to a boiler etc. from an open tank.

  According to the present invention, there is provided a drain recovery system that recovers drain generated by condensing steam generated in a boiler and used in a load device and supplies the drain to the boiler. An open-type open tank to be recovered as: a circulating means for circulating makeup water in the open tank; a temperature detection means for detecting the temperature of makeup water in the open tank; the load device; and the open tank. A drain return line to be connected, an exhaust drain line branched from the drain return line, and a control means for stopping the circulation operation by the circulation means when the detected temperature of the temperature detection means exceeds a first set temperature. A drain recovery system is provided.

  According to the present invention, the control means is configured to stop the circulation operation by the circulation means when the temperature detected by the temperature detection means exceeds the first set temperature. Moreover, since the drain drain line branched from the drain return line is provided, it is also possible to suppress the inflow of drain into the open tank. As a result, the temperature increase of the makeup water in the open tank can be suppressed, and the occurrence of cavitation when supplying water to the boiler or the like can be suppressed.

  Hereinafter, various embodiments of the present invention will be exemplified. The following embodiments can be combined with each other.

  Preferably, the control unit opens the drain line when the temperature detected by the temperature detection unit exceeds a second set temperature higher than the first set temperature.

  Preferably, a new water supply line capable of supplying fresh water to the open tank is provided, and the control means supplies fresh water to the open tank when the temperature detected by the temperature detection means exceeds the second set temperature. To do.

It is a figure showing composition of drain recovery system 1 concerning a 1st embodiment of the present invention. It is a flowchart which shows the temperature control of the drain collection | recovery system 1 of FIG.

  Hereinafter, embodiments of the present invention will be described. Various characteristic items shown in the following embodiments can be combined with each other. The invention is established independently for each feature.

  Hereinafter, a drain recovery system 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. The drain collection system 1 collects the drain generated in the load device 4 and supplies it to the boiler 2. The drain collection system 1 of the present embodiment is configured to be able to collect a drain in a closed system and collect a drain in an open system.

1 Configuration of Drain Recovery System 1 First, the configuration of the drain recovery system 1 of the present embodiment will be described with reference to FIG. The drain recovery system 1 of this embodiment includes a boiler 2, a steam header 3, a load device 4, a drain tank 5, an open tank 6, and a control means 9. Further, the drain recovery system 1 includes, as lines, a connecting pipe L1, a load equipment line L2, a recovery line L3, a drain tank steam line L4, a pressure relief line L5, a drain return line L6, and a makeup water supply. A line L7, a closed water supply line L8, an open water supply line L9, an exhaust drain line L10, and a new water supply line L11 are provided.

  In the present embodiment, the boiler 2 is a small once-through boiler provided with a can body (not shown). The steam generated in the boiler 2 is supplied to the steam header 3 through the connecting pipe L1, and the steam collected in the steam header 3 is supplied to the load equipment 4 through the load equipment line L2. In addition, it is good also as a structure provided with the some boiler 2, the vapor | steam from the several boiler 2 gathering in the steam header 3, and supplying to the load apparatus 4. FIG.

  The load device 4 uses the steam generated in the boiler 2 as a heat source, and performs heat exchange with the object to be heated. A plurality of load devices 4 may be provided in series or in parallel.

  The drain tank 5 collects and stores in a high-temperature and high-pressure state drain that is generated by condensing a part of the steam used for heat exchange in the load device 4. The drain tank 5 is constituted by a sealed pressure vessel having pressure resistance and capable of being sealed. Further, the drain tank 5 is preferably arranged above the boiler 2. The drain tank 5 is preferably provided with a circulating means for circulating the drain flowing through the closed water supply line L8 to the gas phase portion of the drain tank 5 and condensing the vapor in the drain tank 5. However, as the circulation means provided in the drain tank 5, a conventionally known configuration is applied, and the description thereof is omitted.

  The open tank 6 is an open tank that is open to the atmosphere, and stores makeup water to be supplied to the drain tank 5 and the boiler 2. The open tank 6 is preferably disposed above the boiler 2. The open tank 6 is provided with temperature detecting means 91 for detecting the temperature T of the makeup water in the open tank 6.

  In addition, the open tank 6 of the present embodiment includes a circulation means 7 that circulates makeup water in the open tank 6. Specifically, the circulation means 7 includes two circulation means, a first circulation means 70 and a second circulation means 80. Hereinafter, the configuration of the first circulation means 70 and the second circulation means 80 will be described.

  The first circulation means 70 includes a circulation line 71, a circulation pump 72, and a mixing means 73. The mixing unit 73 includes a mixing unit 73a and a water guiding unit 73b.

  The circulation line 71 is a line connecting the lower part (liquid phase part) of the open tank 6 and the mixing part 73 a of the mixing means 73. A circulation pump 72 is installed in the circulation line 71. The circulation pump 72 supplies makeup water below the open tank 6 to the mixing unit 73a via the circulation line 71. In addition, it is preferable to provide a diffusion means (not shown) for spraying makeup water into the mixing unit 73a in the form of a shower on the downstream side of the circulation line 71, that is, the end on the mixing unit 73a side.

  The above-described circulation line 71 and pressure relief line L5 are connected to the mixing unit 73a. In the mixing unit 73a, the mixing unit 73 mixes steam (flash steam) from the pressure relief line L5 and makeup water supplied through the circulation line 71 to condense the steam. Further, the water guiding portion 73 b is a cylindrical pipe that guides the condensed water generated in the mixing portion 73 a into the liquid phase portion of the open tank 6. As the specific structure of the mixing means 73, a conventionally known arbitrary configuration is applied, and detailed description thereof is omitted.

  The second circulation unit 80 includes a circulation line 81, a circulation pump 82, and a mixing unit 83. The mixing unit 83 includes a mixing unit 83a and a water guiding unit 83b. The circulation line 81 is a line connecting the lower part (liquid phase part) of the open tank 6 and the mixing part 83 a of the mixing means 83, and a circulation pump 82 is installed in the circulation line 81.

  The second circulation means 80 mixes steam (flash steam) generated from the drain flowing from the drain return line L6 and make-up water supplied by the circulation line 81 in the mixing section 83a of the mixing means 83, thereby generating steam. Condense. Since the configuration of each element of the second circulation means 80 is the same as that of the first circulation means 70, the description thereof is omitted.

  The first circulation means 70 and the second circulation means 80 configured as described above are used for condensing and recovering steam from the pressure relief line L5 and the drain return line L6. By recovering the steam by the first circulation means 70 and the second circulation means 80, it is possible to improve the thermal efficiency during the open water supply through the open water supply line L9.

  The recovery line L3 is a line that connects the load device 4 and the drain tank 5. The recovery line L <b> 3 recovers the drain generated in the load device 4 and supplies it to the drain tank 5. The downstream end of the recovery line L3 is connected to the upper part (gas phase part) of the drain tank 5. Further, a steam trap 21 that discharges the drain generated in the load device 4 and prevents the discharge of steam is disposed in the recovery line L3. In addition, a drain recovery valve V3 is disposed downstream of a connection position with a drain return line L6 described later.

  The drain tank steam line L <b> 4 is a line connecting the steam header 3 and the drain tank 5. The drain tank steam line L <b> 4 supplies steam generated in the boiler 2 to the drain tank 5. The downstream end of the drain tank steam line L4 is connected to the upper part (gas phase part) of the drain tank 5. In the drain tank steam line L4, a pressure regulating valve V4 for supplying steam to the drain tank 5 at a predetermined pressure is disposed.

  The pressure relief line L5 is a line connecting the drain tank 5 and the open tank 6. The pressure relief line L5 discharges the flash vapor generated in the drain tank 5 to the open tank 6. The upstream end portion of the pressure relief line L5 is connected to the upper portion (gas phase portion) of the drain tank 5. The downstream end of the pressure relief line L5 is connected to the mixing means 73 of the first circulation means 70. A pressure regulating valve V5 is disposed in the pressure relief line L5. When the pressure inside the drain tank 5 exceeds a predetermined pressure, the pressure regulating valve V5 releases the flash vapor to the open tank 6 side and reduces the pressure inside the drain tank 5.

  The drain return line L6 is a line connecting the load device 4 and the open tank 6. The drain return line L <b> 6 introduces surplus drain from the load device 4 into the open tank 6. The surplus drain is drain that could not be accommodated in the drain tank 5 for some reason. Here, the upstream side of the drain return line L6 and the upstream side of the recovery line L3 are configured by a common line. In addition, a drain relief valve V6 is installed at a position downstream of the branch position of the drain return line L6 and the recovery line L3.

  The closed water supply line L8 is a line that connects the drain tank 5 and the boiler 2. The closed water supply line L8 supplies the drain accommodated in the drain tank 5 to the boiler 2. The upstream end portion of the closed water supply line L8 is connected to the bottom portion (liquid phase portion) of the drain tank 5. A drain supply pump P8 is installed in the closed water supply line L8. The drain supply pump P8 boosts the drain supplied from the drain tank 5 and sends it out to the boiler 2 side. Further, a closed water supply valve V8 is disposed at a position downstream of the drain supply pump P8 in the closed water supply line L8.

  The open water supply line L9 is a line connecting the open tank 6 and the boiler 2. The open water supply line L9 supplies makeup water stored in the open tank 6 to the boiler 2. The upstream end of the open water supply line L9 is connected to the bottom (liquid phase part) of the open tank 6. A booster pump Pb is installed in the open water supply line L9. The booster pump Pb boosts the makeup water supplied from the open tank 6 and sends it out to the boiler 2 side. The booster pump Pb is provided to prevent cavitation in the open water supply line L9. In the present embodiment, the installation position of the booster pump Pb on the open water supply line L <b> 9 is a position closer to the open tank 6 than the intermediate position between the open tank 6 and the boiler 2. The installation position of the booster pump Pb is more preferably the position closest to the open tank 6 when the open water supply line L9 is divided into four equal parts. In addition, a check valve Vb that blocks the flow in the direction of the booster pump Pb is disposed downstream of the booster pump Pb (boiler 2 side). In addition, the auxiliary water supply line L9 is provided with an auxiliary pump P9 and a check valve V9 also at the boiler 2 side position shown in FIG.

  The makeup water supply line L7 is a line branched from the open water supply line L9, and connects the open water supply line L9 and the drain tank 5. The makeup water supply line L7 branches from the open water supply line L9 at a position downstream of the check valve Vb and upstream of the auxiliary pump P9. The makeup water supply line L7 supplies makeup water stored in the open tank 6 to the drain tank 5 via the open water supply line L9. A makeup water supply pump P7 is disposed in the makeup water supply line L7, and the makeup water is supplied from the open tank 6 to the drain tank 5 by driving the makeup water supply pump P7. Further, a check valve V7 is provided on the downstream side of the makeup water supply pump P7 to prevent the makeup water from flowing backward in the direction of the open water supply line L9.

  The exhaust drain line L10 is a line branched from the drain return line L6. One end of the exhaust drain line L10 is connected to the drain return line L6, and the other end side of the exhaust drain line L10 is connected to a tank or the like (not shown). An exhaust drain valve V10 is provided in the exhaust drain line L10. Then, when the drain drain valve V10 is opened, the drain drain line L10 branches the drain flowing through the drain return line L6 and stores it in a tank (not shown) or the like, thereby reducing the drain circulation to the open tank 6. Note that the drain drain valve V10 may be a ball valve or the like whose flow rate can be adjusted, and the flow rate of the drain to be discharged (the amount of drain flowing into the open tank 6 at the same time) may be adjustable.

  The fresh water supply line L11 is a line for supplying fresh water to the open tank 6 from the outside. The fresh water supply line L11 is connected to the bottom (liquid phase part) of the open tank 6. Further, a new water valve V11 is installed in the new water supply line L11. The fresh water is preferably cold water in order to lower the temperature of the makeup water. Further, in the present embodiment, the open tank 6 stores water in which this fresh water is mixed with the drain from the drain return line L6 and the drain condensed with the steam from the pressure relief line L5.

  The control means 9 controls the recovery of the drain and the supply to the boiler 2 by controlling the opening and closing of the valves provided in the respective lines and the driving of the pumps based on signals from the boiler 2 and the like. Moreover, the control means 9 of this embodiment also performs temperature control of the makeup water in the open tank 6 based on the temperature T detected by the temperature detection means 91. Details of the temperature control of the makeup water by the control means 9 will be described later.

  The control means 9 is specifically composed of a CPU and various memories. The operation of the control means 9 is stored in a storage medium such as a hard disk or SSD (solid state drive) in the form of a program. Each control is performed by the CPU reading and executing this program.

  The drain recovery system 1 configured as described above stores the drain generated in the load device 4 in the drain tank 5 or the open tank 6. The drain accommodated in the drain tank 5 is supplied to the boiler 2 via the closed water supply line L8 (closed water supply), and the drain accommodated in the open tank 6 is supplied to the boiler 2 via the open water supply line L9 (open water supply) )

  In the case of closed water supply, the control means 9 is based on temperature, pressure, water level, etc. measured by a temperature sensor, pressure sensor, water level sensor, etc. (not shown) installed in the drain tank 5. Controls line valves and pumps. For these controls, a conventionally known method is used and detailed description thereof is omitted. Moreover, the drain collection system 1 of this embodiment is controlled so that closed water supply with high thermal efficiency is preferentially performed during normal times, and open water supply is performed when a failure occurs in the closed water supply.

2 Temperature control of makeup water Next, temperature control of makeup water in the open tank 6 in the drain recovery system 1 having the above configuration will be described using the flowchart of FIG. In the present embodiment, the temperature control is achieved by a circulation operation by the circulation means 7 and a drain discharge operation by opening and closing the exhaust drain line L10.

  When the drain recovery operation of the drain recovery system 1 is started, the temperature control of the makeup water in the open tank 6 is also started. After the start of the temperature control, the control means 9 first starts the circulation operation of the circulation means 7 in step S1. Specifically, the control means 9 drives the circulation pump 72 to execute the circulation operation of the makeup water via the circulation line 71 by the first circulation means 70. At the same time, the control means 9 drives the circulation pump 82 to execute the circulation operation of the makeup water via the circulation line 81 by the second circulation means 80. By performing the circulation operation, the steam supplied to the open tank 6 is condensed and heat recovery is performed, so that the temperature T of the makeup water rises.

  Next, in step S2, the control means 9 determines whether or not the temperature T of the makeup water in the open tank 6 detected by the temperature detection means 91 has exceeded the first set temperature T1. Here, the first set temperature T1 is preferably set to 85 ° C. to 95 ° C., for example. The first set temperature T1 is more preferably 88 ° C. to 92 ° C. This determination step S2 is always executed until the next step S3 is entered. When the temperature T of the makeup water exceeds the first set temperature T1, the process proceeds to the next step S3. In step S3, the circulation operation of the circulation means 7, that is, the first circulation means 70 and the second circulation means 80 is performed. Stop circulating operation.

  Next, in step S4, the control means 9 determines whether or not the temperature T of the makeup water in the open tank 6 detected by the temperature detection means 91 has exceeded a second set temperature T2 that is higher than the first set temperature T1. To do. Here, it is preferable that 2nd preset temperature T2 shall be 90 degreeC-99 degreeC, for example. The second set temperature T2 is more preferably 93 ° C to 97 ° C. This determination step S4 is always executed until the process proceeds to the next step S5. If the temperature T of the makeup water exceeds the second set temperature T2, the process proceeds to the next step S5, where the control means 9 opens the drain drain valve V10 and opens the drain drain line L10. Thereby, at least a part of the drain that has flowed into the open tank 6 is stored in the tank or the like via the drain line L10. Further, at substantially the same timing, in step S6, the new water valve V11 is opened, and fresh water is supplied to the open tank 6 via the new water supply line L11.

  After the drain drain line L10 is opened in step S5 and the supply of fresh water is started in step S6, the makeup water supplied by the circulation means 7 is stopped until the boiler 2 is stopped and the drain recovery operation of the drain recovery system 1 is completed. The state where the circulation is stopped is continued, and the state where the drain line L10 is opened is continued. And if the boiler 2 stops and the water supply to the boiler 2 stops, the control means 9 will complete | finish the temperature control of the open tank 6. FIG.

  The control means 9 closes the drain line L10 (closes the drain drain valve V10) and closes the new water valve V11 when the makeup water temperature T again falls below the second set temperature T2. You may control to stop supply of water. Further, when the makeup water temperature T again falls below the first set temperature T1, control may be performed so that the circulation operation of the circulation means 7 is resumed.

3 Effect The drain recovery system 1 as described above is configured such that the control means 9 stops the circulation operation by the circulation means 7 when the temperature T detected by the temperature detection means 91 exceeds the first set temperature T1. When the detected temperature T detected by the temperature detecting means 91 exceeds the second set temperature T2, the control means 9 opens the drain drain valve V10 and opens the drain drain line L10, and opens the new water valve V11. The new water is supplied to the open tank 6 from the new water supply line L11. Therefore, the drain recovery system 1 of this embodiment can suppress the rise in the temperature of the makeup water in the open tank 6 by these controls by the control means 9, and as a result, supplies water to the boiler or the like. It is possible to suppress the occurrence of cavitation.

  By the way, in this embodiment, the replenishment water of the open tank 6 is pressurized by the booster pump Pb and supplied to the boiler 2, but this booster pump Pb may not be used for some reason. In this case, even if the supply to the boiler 2 is possible, there is a high possibility that cavitation will occur in the open water supply line L9. However, in the drain recovery system 1 of the present embodiment, even if the booster pump Pb cannot be used, the control means 9 performs the temperature control of the makeup water in the open tank 6 by the above-described steps. It is possible to suppress the occurrence of cavitation in the open water supply line L9.

  When the booster pump Pb cannot be used, water is supplied to the boiler 2 via the bypass line (not shown) that bypasses the booster pump Pb without passing through the booster pump Pb, or the booster pump Pb is removed and connected to the pipeline. It is preferable to replace and supply water to the boiler 2 through the pipe line.

4 Modifications The present invention can also be implemented in the following modes.
In the above embodiment, the open / close control of the drain drain valve V10 of the drain line L10 is controlled by the control unit 9 according to the temperature T of the makeup water in the open tank 6 detected by the temperature detection unit 91. However, it is not limited to this configuration. That is, it is also possible to adopt a configuration in which the user manually opens and closes the drain drain valve V10 according to the state of the open tank 6 and the state of the booster pump Pb. In addition, when the drain valve V10 is a ball valve or the like whose flow rate can be adjusted, the flow rate of the drain to be discharged is adjusted according to the temperature T of the makeup water, and the amount of drain that flows into the open tank 6 is adjusted. You may comprise.
In the above embodiment, the exhaust drain line L10 is connected to a tank or the like (not shown), but the other end of the exhaust drain line L10 can be simply opened to the atmosphere. .
In the above embodiment, when the temperature T of the makeup water in the open tank 6 is controlled, if the makeup water temperature T exceeds the first set temperature T1, the circulation operation of the first circulation means 70 and the second circulation means 80 is performed simultaneously. Although it was the structure which stops, it is not limited to this structure. That is, it is possible to have a configuration in which only one of the circulating means is stopped. Also, when the third set temperature T3 (> T1) is defined and the makeup water temperature T exceeds the first set temperature T1, one of the first set temperature T1 is set. It is also possible to stop the circulation of the circulation means and then stop the circulation of the other circulation means when the temperature T of the makeup water exceeds the third set temperature T3.
In the above embodiment, the circulation means 7 includes two circulation means: the first circulation means 70 to which the pressure relief line L5 is connected, and the second circulation means 80 to which the first circulation means 70 and the drain return line L6 are connected. However, only one of the circulation means may be provided.
In the above embodiment, the second set temperature T2 that is a threshold value for opening the drain line L10 is set to be higher than the first set temperature T1 that is a threshold value for stopping the circulation operation of the circulation means 7. However, the threshold setting is not limited to this. That is, the first set temperature T1 and the second set temperature T2 can be set to the same temperature, or the first set temperature T1 can be set to be higher than the second set temperature T2.

1: Drain recovery system 2: Boiler 3: Steam header 4: Load device 5: Drain tank 6: Open tank 7: Circulation means 9: Control means 21: Steam trap 70: First circulation means 71: Circulation line 72: Circulation pump 73: Mixing means 73a: Mixing section 73b: Water conveyance section 80: Second circulation means 81: Circulation line 82: Circulation pump 83: Mixing means 83a: Mixing section 83b: Water conveyance section 91: Temperature detection means L1: Connection pipe L2: Load Equipment line L3: Recovery line L4: Drain tank steam line L5: Pressure relief line L6: Drain return line L7: Makeup water supply line L8: Closed water supply line L9: Open water supply line L10: Drain drain line L11: Fresh water supply line P7: makeup water supply pump P8: drain supply pump P9: auxiliary pump Pb : Booster pumps S1 to S6: Step T: Temperature (detected temperature)
T1: First set temperature T2: Second set temperature T3: Set temperature V3: Drain recovery valve V4: Pressure adjustment valve V5: Pressure adjustment valve V6: Drain relief valve V7: Check valve V8: Closed water supply valve V9: Check Valve V10: Drain drain valve V11: Fresh water valve Vb: Check valve

Claims (3)

A drain recovery system that recovers drain generated by condensation of steam generated in a boiler and used in load equipment, and supplies the drain to the boiler,
An open-type open tank that collects drain generated in the load device as makeup water;
Circulating means for circulating makeup water in the open tank;
Temperature detecting means for detecting the temperature of makeup water in the open tank;
A drain return line connecting the load device and the open tank;
An exhaust drain line branched from the drain return line;
Control means for stopping the circulation operation by the circulation means when the temperature detected by the temperature detection means exceeds a first set temperature;
A drain recovery system. The drain recovery system according to claim 1,
The control means opens the drain drain line when the temperature detected by the temperature detection means exceeds a second set temperature that is higher than the first set temperature. The drain recovery system according to claim 2,
It has a new water supply line that can supply new water to the open tank,
The control means is a drain recovery system for supplying fresh water to the open tank when the temperature detected by the temperature detection means exceeds the second set temperature.