JP5794171B2 - Drain collection system - Google Patents

Description

  The present invention relates to a drain recovery system that recovers high-temperature drain generated by a load device in a closed drain tank and supplies the recovered drain to a steam boiler for use.

  In this type of drain recovery system, the steam boiler that supplies steam to the load equipment and the drain discharged from the load equipment through the drain return line are stored, and the stored drain is supplied to the steam boiler through the drain supply line having a drain pump. A closed-type drain tank, a supply water tank that is open to the atmosphere that supplies makeup water to the drain tank through a makeup water line that has a makeup water pump, and a pressure valve that opens and closes depending on the pressure in the drain tank, A drain recovery system including a pressurized steam line that supplies high-pressure steam from a steam boiler to a drain tank is known from Patent Document 1 and the like.

  This system of Patent Document 1 is called a closed drain recovery system, and it is possible to prevent the generation of flash steam in the drain tank by increasing the pressure in the drain tank by means of a pressurized steam line. Water can be supplied to the boiler.

JP 2011-237065 A (* Note: Company S application)

  In the drain recovery system of Patent Document 1, if the pressurization valve remains open during a power failure, the steam continues to flow from the pressurization line, and if the pressure relief valve does not operate normally, the inside of the drain tank becomes an abnormally high pressure. The safety valve provided in the drain tank blows (opens). Moreover, since the drain pump stops at the time of a power failure, if the drain continues to flow into the drain tank, the water level in the drain tank becomes an abnormally high water level and the safety valve blows. If the safety valve blows, it will be necessary to replace the safety valve, and even if the power failure recovers, the drain recovery system must be shut down for a while. The shutdown of the drain collection system leads to the shutdown of the user's load equipment.

  The problem to be solved by the present invention is that, in the event of a power failure, even if the pressure relief valve does not operate normally, or even if the drain pump stops, the drain tank does not operate abnormally and the abnormal pressure inside the drain tank It is to prevent becoming.

The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 stores a steam boiler that supplies steam to a load device, and drain discharged from the load device through a drain return line. And a closed drain tank that supplies drainage stored through a drain supply line having a drain pump to the steam boiler, and an open air replenishment that supplies makeup water to the drain tank through a makeup water line having a makeup water pump. A water tank, a pressure valve that opens and closes according to the pressure in the drain tank, a pressure steam line that supplies high-pressure steam from the steam boiler to the drain tank, and a pressure that opens when the pressure in the drain tank rises A drain recovery system having a relief valve and a pressure relief line for escaping steam from the drain tank to the makeup water tank An openable and closable drain return valve provided in the drain return line, and an openable and closable drain relief valve provided in a drain relief line connected between the upstream side of the drain return valve and the makeup water tank. The drain return valve and the pressurizing valve are valves that close when energization is stopped, and the drain relief valve is a valve that opens when power is stopped.

  According to the first aspect of the present invention, when a power failure occurs, the drain return valve and the pressurization valve are closed, and the drain relief valve is opened, so that steam is supplied from the pressurization line to the drain tank. While being stopped, the drain inflow from the drain return line to the drain tank is stopped. As a result, even if the pressure relief valve does not operate normally or the drain pump stops, abnormal high pressure in the drain tank due to a power failure can be prevented without operating the safety valve.

  The invention according to claim 2 includes a preliminary water supply line that connects the makeup water tank and the steam boiler and has an auxiliary pump, and water supply to the steam boiler is normally performed by the drain pump at the time of a power failure of the system. When not, the auxiliary pump is driven.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, there is an effect that the water supply from the makeup water tank to the steam boiler can be continued even if the system fails. .

  According to the present invention, in the event of a power failure, even if the pressure relief valve does not operate normally or the drain pump stops, the inside of the drain tank becomes abnormally high without operating the safety valve. Can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of Example 1 of the drain collection system which implemented this invention. It is a flowchart figure explaining the control program of the 1st valve (drain return valve) of the Example 1. FIG. It is a flowchart figure explaining the control program of the 2nd valve (drain relief valve) of the Example 1. FIG. It is a flowchart figure explaining the control program of the makeup water pump of Example 1. It is a flowchart figure explaining the control program of the drain pump of the Example 1. FIG. It is a flowchart figure explaining the control program of the 3rd valve (pressurization valve) of the Example 1. FIG. It is a flowchart figure explaining the control program of the 4th valve of the Example 1. It is a flowchart figure explaining the control program of the 5th valve of the Example 1. FIG. It is a schematic block diagram of Example 2 of the drain recovery system which implemented this invention. It is a flowchart figure explaining the control program of the 4th valve of Example 3 of the drain collection | recovery system which implemented this invention.

  Next, an embodiment of the present invention will be described. The embodiment of the present invention is suitably implemented in a drain recovery system that supplies and uses drain recovered from a load device that is a steam-using device of a steam boiler.

  This embodiment will be specifically described. The drainage recovery system of this embodiment stores a steam boiler that supplies steam to a load device, a drain that is discharged from the load device through a drain return line, and a drain that has been stored through a drain supply line having a drain pump. A closed drain tank that supplies water, a replenishment water tank that supplies replenishment water to the drain tank through a replenishment water line having a replenishment water pump, and a pressure valve that opens and closes depending on the pressure in the drain tank , Equipped with a pressurized steam line that supplies high-pressure steam from the steam boiler to the drain tank, and a pressure relief line that has a pressure relief valve that opens when the pressure in the drain tank rises, and releases steam from the drain tank to the makeup water tank ing. The drain tank is provided with a safety valve that is mechanically opened at a pressure in the drain tank that is higher than the operating pressure of the drain relief valve.

  This embodiment is characterized by an openable / closable drain return valve provided in the drain return line and an openable / closable provided in the drain relief line connected between the upstream side of the drain return valve and the makeup water tank. And a drain return valve and a pressurizing valve are closed when energization is stopped, and the drain relief valve is a valve that is opened when energization is stopped. The valve that closes when the power supply is stopped and the valve that opens when the power supply is stopped can be referred to as a normally closed valve and a normally open valve, respectively, and are configured by a spring return system or a valve having an equivalent function. The spring return method is a mechanism that performs a closing operation or an opening operation in a certain mechanical direction when the power supply is cut off.

  Further, the pressure relief valve is not limited to an open / close valve such as an electrically operated motor valve as described in Patent Document 1, and is a pressure regulating valve that is mechanically opened / closed instead of being electrically operated. It can be.

  In this embodiment, the inside of the drain tank is pressurized by pressurized steam supplied from a pressurized steam line. The supply of the pressurized steam is maintained at a predetermined pressure higher than the atmospheric pressure by opening and closing the pressurizing valve in the pressurized steam line. During normal operation, since the drain return valve is open and the drain relief valve is closed, the drain from the load device is introduced into the drain tank through the drain return line.

  Here, when a power failure occurs, the pressurization valve is closed, so that the supply of pressurized steam to the drain tank through the pressurization line is stopped. At the same time, since the drain return valve is closed and the drain relief valve is opened, the drain from the drain return line is guided to the makeup water tank without flowing into the drain tank. As a result, even if the pressure relief valve does not operate normally or the drain pump stops during a power failure, the pressure in the drain tank is prevented from becoming an abnormally high pressure (pressure at which the safety valve operates).

  Here, the component which comprises the drainage collection | recovery system of embodiment of this invention is demonstrated. The steam boiler and the load equipment are not limited to specific types and structures.

  Further, the drain tank may be of a sealed type and is not limited to a specific structure. The makeup water tank may be an open type tank and is not limited to a specific structure. Moreover, a motor valve, a solenoid valve, and an air drive valve can be used for the drain return valve and the drain relief valve.

The pressurized steam line has a pressure valve that opens and closes according to the pressure in the drain tank.
A pressurized steam line for supplying pressurized steam having a pressure exceeding the atmospheric pressure from a steam header (including a steam header provided at a steam outlet of the steam boiler) to a drain tank is provided. The pressurizing valve is a valve that opens and closes mechanically in response to pressure, or a valve that opens and closes electrically by a pressure sensor. Further, the pressurizing valve can be composed of a valve for adjusting the supply steam pressure and a valve for shutting off the steam. By providing this pressurized steam line, the steam is supplied into the drain tank and kept above the saturation pressure, so that high-temperature drain can be recovered without generating flash steam and cavitation of the drain pump. Can be prevented.

  Next, a drain recovery system according to Embodiment 1 of the present invention will be described with reference to FIGS.

<Configuration of Example 1>
The drain recovery system 1 of the first embodiment includes a steam boiler 2, a drain return line 3, a drain tank 4, a makeup water line 5, a drain supply line 6, a makeup water tank 7, and a drain relief line 8. , A pressurized steam line 9, a pressure relief line (which can be referred to as a steam relief line) 10, a drain circulation line 11, and a controller 12 as control means. The steam boiler 2 supplies the load equipment 13 that uses steam through the steam supply line 2A. In FIG. 1, the part enclosed with the dashed-dotted line Y is comprised integrally as a drain collection | recovery apparatus.

  The drain return line 3 supplies the drain discharged from the load device 13 to the drain tank 4 via a steam trap (not shown), and the first valve V1 as a drain return valve composed of a normally closed motor valve. It has.

  The drain tank 4 is configured in a sealed type, and supplies the stored drain to the steam boiler 2 through a drain supply line 6 having a drain pump 14. A water level gauge 15 is connected to the drain tank 4 by a first communication pipe 16 that communicates the gas phase parts and a second communication pipe 17 that communicates the liquid phase parts. The first series pipe 16 is provided with a pressure sensor 18 as a first pressure detector for detecting the pressure in the drain tank 4. The pressure sensor 18 may be provided in the liquid phase part (or gas phase part) of the drain tank 4 or the water level gauge 15.

  Further, the water level meter 15 includes a differential pressure type water level sensor 19 as a first water level detector for detecting the water level in the water level meter 15 and a second water level detector for detecting an abnormal water level so as to back up the water level sensor 19. And an open / close switch type pressure switch 21 as a second pressure detector for detecting an abnormal pressure so as to back up the pressure sensor 18. This pressure switch 21 may also be provided in the drain tank 4. A plurality of pressure switches can be provided.

  The makeup water line 5 includes a makeup water pump 22 and a first check valve 23 that blocks the flow in the makeup water tank 7 direction, and drains the makeup water stored in the atmosphere-opening makeup water tank 7. This is supplied to the tank 4. The makeup water tank 7 is provided with a makeup water supplement line 24, and the flow rate of the makeup water supplement line 24 is adjusted by a water level detector (not shown) so that the water level in the makeup water tank 7 becomes the set water level.

  The drain supply line 6 is provided with a drain pump 14 and a second check valve 25 that blocks the flow in the direction of the drain pump 14. A drain circulation line 11 including a part of the drain supply line 6 for circulating the drain in the drain tank 4 is provided between the drain pump 14 outlet side of the drain supply line 6 and the drain tank 4. The circulation amount of the drain circulation line 11 is not less than the minimum flow rate (minimum flow) that is the minimum flow rate required for cooling the drain pump 14.

  The drain circulation line 11 includes a first circulation line 11 </ b> A including an ejection pipe (which can be referred to as an injector) 26 serving as an injection unit having a nozzle that injects drain into the vapor phase portion in the drain tank 4 in a mist form. The second circulation line 11B for returning the drain to the liquid phase part in the drain tank 4 is configured. The first circulation line 11A is provided with a fifth valve V5 composed of a motor valve, and the second circulation line 11B is a flow resistance for adjusting the flow rate (minimum flow) of the second circulation line 11B when the fifth valve V5 is closed. An orifice 27 is provided. Further, in an appropriate place (in the first embodiment, between the drain tank 4 of the drain supply line 6 and the drain pump 14) in the flow path (in the drain tank 4, including the drain supply line 6) constituting the second circulation line 11B. A temperature detector 28 for detecting the temperature of the drain supplied to the steam boiler 2 is provided.

  The drain relief line 8 connects the upstream side of the first valve V1 of the drain return line 3 composed of a normally closed motor valve and the makeup water tank 7, and is a second drain relief valve composed of a normally open motor valve. A valve V2 is provided. In the first embodiment, the first valve V1 and the second valve V2 are of the spring return type.

  The pressurized steam line 9 connects the steam supply line 2A on the steam outlet side of the steam boiler 2 and the drain tank 4, and is provided with a third valve V3 composed of a normally closed motor valve as a pressurizing valve. The third valve V3 is also of a spring return type. A pressure reducing valve (not shown) is provided on the primary side of the third valve V3 as necessary.

  The pressure relief line 10 connects the gas phase part of the drain tank 4 and the make-up water tank 7, a pressure regulating valve 29 as a pressure relief valve that opens above a set pressure, and a motor connected in parallel with the pressure regulating valve 29. A fourth valve V4 comprising a valve is provided. The fourth valve is opened by the pressure sensor 18 at an operating pressure (second operating pressure) higher than the operating pressure (first operating pressure) of the pressure regulating valve, closed at a differential pressure lower than the second operating pressure, and the pressure switch 21. Thus, the on-off valve is closed at an operating pressure higher than the second operating pressure (third operating pressure) and closed at a differential pressure lower than the third operating pressure. The first operating pressure, the second operating pressure PH, and the third operating pressure PHH are, for example, 0.78 MPa, 0.83 MPa, and 0.9 MPa, respectively, but are not limited thereto. These numerical values do not limit the scope of rights of the present invention.

  Further, when the drain pump 14 is stopped between the make-up water tank 7 and the steam boiler 2 and the drain cannot be supplied to the steam boiler 2, preliminary water supply for supplying make-up water from the make-up water tank 7 to the steam boiler 2. A line 30 is provided. The auxiliary water supply line 30 is provided with an auxiliary pump 31 attached to the steam boiler 2 and a third check valve 32 for blocking the flow in the direction of the auxiliary pump 31.

  The makeup water tank 7 is provided with a first mixer 33 and a second mixer 34. The first mixer 33 has a function of mixing the steam from the pressure relief line 10 with the makeup water in the lower portion of the makeup water tank 7 to exchange heat. Further, the second mixer 34 has a function of mixing the steam generated from the drain from the drain return line 8 with the makeup water in the lower portion of the makeup water tank 7 to exchange heat.

The first mixer 33 and the second mixer 34 have the same structure, mixing chambers 33A and 34A for mixing steam and make-up water, and water mixed and communicated with the mixing chambers 33A and 34A. The water guide pipes 33B and 34B leading to the liquid phase part of the water supply pipe 33B, and the steam chambers 33C and 34C formed on the outside of the water guide pipes 33B and 34B with a space therebetween. Each of the water guide pipes 33B and 34B and each of the steam chambers 33C and 34C is formed with a steam hole (not shown), and the steam present in the water guide pipes 33B and 34B is passed through the steam hole to the gas phase portion of the makeup water tank 7. In this way, it is configured to prevent re-dissolution of oxygen by allowing a small amount of vapor to exist in the gas phase.

  The pressure relief line 10 and the makeup water circulation line 35A are connected to the mixing chamber 33A, and the drain return line 8 and the makeup water circulation line 35B are connected to the mixing chamber 34A. Each makeup water circulation line 35A, 35B is provided with circulation pumps 36A, 36B.

  In the case where the configuration of the first mixer 33 and the second mixer 34 is not provided, when the drain of the drain relief line 8 and the steam of the pressure relief line 10 flow into the makeup water tank 7, the makeup water tank 7 is an open type. As a result, the heat held by the drain and steam easily escapes to the atmosphere. On the other hand, by providing the configuration of the first mixer 33 and the second mixer 34, the heat retained by the drain of the drain relief line 8 and the steam of the pressure relief line 10 can be effectively recovered. The circulation of the makeup water by the circulation pumps 36A and 36B can be configured to perform control such as stopping or decreasing the circulation amount when the temperature is high based on the temperature of the liquid phase portion in the makeup water tank 7. .

  The controller 12 inputs signals from the pressure sensor 18, the water level sensor 19, the float switch 20, the pressure switch 21, the temperature detector 28, and the like, and based on the control procedure stored in advance, the first valve V1 to the first valve. Controls the five valves V5, the drain pump 14, the makeup water pump 22, and the like. The auxiliary pump 31 is controlled by the controller on the steam boiler 2 side, but may be configured to be controlled by the controller 12.

  The control procedure of the controller 12 includes a drain tank pressure control procedure, a water level / drain temperature control procedure, a drain circulation control procedure for controlling circulation of the drain circulation line 11, and the like.

  In the drain tank pressure control procedure, when the pressure sensor 18 detects a second operating pressure PH higher than the operating pressure (first operating pressure) of the pressure regulating valve 29, the fourth valve V4 is opened, and the pressure switch 21 is set to the second operating pressure. When the third operating pressure PHH higher than PH is detected, the fourth valve V4 is closed, the pressurized steam line 9 is closed, the first valve V1 is closed, and the second valve V2 is opened. The first operating pressure is set higher than the second set pressure PL. This control procedure is realized by the control procedure shown in FIGS.

  In the first embodiment, in addition to the pressure control procedure of the controller 12, a pressure safety configuration at the time of a hardware power failure is provided. That is, as described above, the drain return valve V1 and the pressurizing valve V3 are valves that are closed when the energization of the spring return method is stopped, and the drain relief valve V2 is a valve that is opened when the energization of the spring return method is stopped. Further, the drain tank 4 is provided with a safety valve 37 as a final pressure safety mechanism when pressure control is not normally performed at the time of a power failure by the controller 12 or when the drain pump is stopped. The safety valve 37 is opened at a pressure higher than the operating pressure PHH of the pressure switch 21 in the drain tank 4 and is generally provided in a pressure vessel such as a boiler.

The water level / drain temperature control procedure includes the following first control and second control. In the first control, the make-up water pump 22 is driven when the temperature detected by the temperature detector 28 is equal to or higher than the first set temperature TH, the make-up water pump 22 is stopped when the temperature is lower than the first set temperature TH, and the make-up water pump 22 is driven. When the water level detected by the water level sensor 19 is equal to or higher than the first set water level LHH, the make-up water pump 22 is stopped, the first valve V1 and the second valve V2 are in the second open / closed state, and replenishment is made below the first set water level LHH. In this control, the water pump 22 is driven so that the first valve V1 and the second valve V2 are in the first open / close state. In the second control, when the makeup water pump 22 is driven, the temperature detected by the temperature detector 28 is equal to or higher than the second set temperature THH higher than the first set temperature TH, and the first valve V1 and the second valve V2 are in the second open / close state. In addition, the first valve V1 and the second valve V2 are controlled to be in the first open / close state at a temperature lower than the second set temperature THH. The first control and the second control are realized by the control procedure shown in FIGS.

  In the first embodiment, the first set temperature TH and the second set temperature THH are set to 170 and 175, respectively, but the temperature can be appropriately set in the range of 100 to 220 according to the system configuration and operating conditions. .

  In the drain circulation control procedure, when the temperature detected by the temperature detector 28 exceeds (or becomes higher) than the first set temperature TH, or is less than (or below) the third set temperature TL lower than the first set temperature TH, A procedure for stopping drain circulation by the first circulation path 11A and a procedure for performing drain circulation by the first circulation path 11A when the detected pressure of the first pressure detector 18 exceeds (or exceeds) the first set pressure PH. Including. An example of this drain circulation control procedure is shown in FIG.

  Further, the control procedure of the first valve V1, the control procedure of the second valve V2, the control procedure of the makeup water pump 22, the control procedure of the drain pump 14, the control procedure of the third valve V3, the fourth valve of the first embodiment. The control procedure for V4 and the control procedure for the fifth valve V5 are shown in FIGS. 2, 3, 4, 5, 6, 7, and 8, respectively.

<Operation of Example 1>
(Water level / drain temperature control)
Here, the operation | movement by the water level and drain temperature control procedure of Example 1 is demonstrated based on FIGS. With reference to FIG. 1, in the load apparatus 13, the vapor | steam supplied from the boiler 2 liquefies. The liquefied drain tends to flow into the drain tank 4 through the drain return line 3.

  2 and 3, when the operation switch (not shown) of the system is turned on, the first valve V1 is closed in processing step S1 (hereinafter, processing step SN is simply referred to as SN) and S11. The second valve V2 is opened (second open / close state), and the process proceeds to S2 to determine whether or not the pressure switch 21 is ON. When the pressure in the water level gauge 15 is equal to or higher than the abnormal high pressure set pressure (set pressure higher than the first set pressure PH described later), the pressure switch 21 is turned on, so YES is determined in S2 and S12, and the process returns to S1 and S11. Maintain the second open / close state.

  Thus, when the pressure in the drain tank 4 is abnormally high, the drain from the load device 13 is prevented from flowing into the drain tank, and instead flows into the makeup water tank 7. As a result, even if the pressure in the drain tank 4 is abnormally high, the drain is collected into the makeup water tank 7 while continuing the operation of the load device 13. This drain recovery is performed through the second mixer 34 as described above.

  At this time, since YES is determined also in S32 of FIG. 5, the drain pump 14 is stopped, and water supply from the drain tank 4 to the steam boiler 2 is stopped. However, when the controller (not shown) of the steam boiler 2 determines that there is no water supply from the drain tank 4, the auxiliary pump 31 is driven. As a result, since the water supply from the makeup water tank 7 to the steam boiler 2 is continued, the operation of the steam boiler 2 is continued, and the steam can be continuously used in the load device 13.

  2 and 3, when NO is determined in S2 and S12, the process proceeds to S3 and S13, and the float switch 20 detects an abnormally high set water level (a set water level higher than the first set water level LHH described later) or more. Determine whether you are doing. When the water level in the water level gauge 15 is equal to or higher than the abnormally high set water level, YES is determined in S3 and S13, and the process returns to S1 and S11 to maintain the second open / close state. In addition, when the water level sensor 19 is operating normally, the float switch 20 is not operated, and YES is not determined in S3 and S13.

  Thus, when the water level in the drain tank 4 is an abnormally high water level, the drain is collected into the makeup water tank 7 while the operation of the load device 13 is continued as in the case where the pressure in the drain tank 4 is abnormally high. . At this time, the drain pump 14 is stopped, but the operation of the steam boiler 2 is continued by driving the auxiliary pump 31 as in the case where the water level in the drain tank 4 is an abnormally high water level.

  If NO is determined in S3 and S13, the process proceeds to S4 and S14, and it is determined whether or not the water level sensor 19 has detected an excess of the first set water level LHH (a value higher than the differential by LHH). When the water level in the water level meter 15 exceeds the first set water level LHH, YES is determined in S4 and S14, and the process returns to S1 and S11 to maintain the second open / close state.

  Thus, when the water level in the drain tank 4 exceeds the first set water level LHH, the inflow of drain into the drain tank 4 is blocked, and the drain tank 4 is prevented from becoming an abnormally high water level. Then, as in the case where the pressure in the drain tank 4 is abnormally high, the drain is collected into the makeup water tank 7 while the operation of the load device 13 is continued. At this time, the drain pump 14 is stopped, but the operation of the steam boiler 2 is continued by driving the auxiliary pump 31 as in the case where the water level in the drain tank 4 is an abnormally high water level.

  Then, when the detected water level of the water level sensor 19 detects the first set water level LHH or less, NO is determined in S4 and S14, the process proceeds to S5 and S15, and the detected temperature of the temperature sensor 28 exceeds the second set temperature THH. Whether or not (a value higher than the THH by a differential amount is detected) is determined. If YES is determined in S5 and S15, the process proceeds to S1 and S11, and the second open / close state is maintained. When the temperature detected by the temperature sensor 28 is equal to or lower than the second set temperature THH, NO is determined in S5 and S15, the process proceeds to S6 and S16, the first valve V1 is opened, and the second valve is closed (first One open / close state), the drain from the load device 13 flows into the drain tank.

  Thus, when the temperature detected by the temperature sensor 28 exceeds the second set temperature THH in the drain tank 4 by the processing of S5 and S15, the inflow of high-temperature drain into the drain tank 4 is prevented, so that the drain tank 4 It is prevented that the drain temperature inside exceeds the second set temperature THH. The drain temperature in the drain tank 4 can be quickly reduced by the drain inflow prevention operation and the drain cooling operation by the control of the makeup water pump 22 described below.

  Next, the operation of the makeup water pump 22 will be described with reference to FIG. In S21, the makeup water pump 22 is stopped. Next, in S22, it is determined whether or not the pressure switch 21 is ON. If YES, the process proceeds to S21 to stop the water supply pump 21, and if NO, the process proceeds to S23 to determine whether the float switch 20 has detected an abnormally high set water level.

  If YES is determined in S23, the makeup water pump 22 is stopped. If NO is determined in S23, the process proceeds to S24, in which it is determined whether or not the water level sensor 19 has detected that the first set water level LHH (> LH) has been exceeded (a value higher than the LHH by a differential amount). If YES, the process proceeds to S21 and the makeup water pump 22 is stopped.

  As will be described later, when the water level in the drain tank 4 decreases due to the driving of the drain pump 14 and the detected water level becomes equal to or lower than the first set water level LHH, NO is determined in S24, the process proceeds to S25, and the temperature sensor 28 is reached. It is determined whether or not the detected temperature exceeds the first set temperature TH (<THH) (a value higher than the differential by TH is detected). If the detected temperature exceeds the first set temperature TH and YES is determined in S25, the process proceeds to S227, and the makeup water pump 22 is driven. By driving the makeup water pump 22, low temperature makeup water is replenished from the makeup water tank 7 into the drain tank 4.

  When the temperature detected by the temperature sensor 28 is equal to or lower than the first set temperature TH and NO is determined in S25, the process proceeds to S26, where the water level in the drain tank 4 exceeds the second set water level LH (a value that is higher by a differential than LH). Is detected). If YES is determined, the process proceeds to S21 and the makeup water pump 22 is stopped. As described later, when the drain pump 14 is driven, the water level in the drain tank 4 is lowered, the water level becomes equal to or lower than the second set water level LH, and when NO is determined in S26, the process proceeds to S27, and the makeup water pump 22 is driven. By driving the makeup water pump 22, low temperature makeup water is replenished from the makeup water tank 7 into the drain tank 4.

  As described above, when the drain temperature in the drain tank 4 exceeds the first set temperature TH and the water level in the drain tank 4 is equal to or lower than the first set water level LHH, the makeup water pump 22 is driven and the drain tank 4 The drain cooling control (first control) is performed. As described above, when the water level in the drain tank 4 exceeds the first set water level LHH or the drain temperature becomes equal to or higher than the second set temperature THH, the first valve V1 and the second valve V2 are opened and closed. Thus, control (second control) is performed so that a large amount of heat held by the drain is not taken into the drain tank 4. As a result, even if the temperature in the drain tank 4 becomes equal to or higher than the second set temperature THH, the first control and the second control cause the drain in the drain tank 4 to be discharged in a short time compared to the system of Patent Document 1. To be cooled. As a result, the operation time of the makeup water pump 22 can be shortened, and power can be saved.

  Next, the operation of the drain pump 14 will be described with reference to FIG. In S31, the drain pump 14 is stopped. Next, the process proceeds to S32 to determine whether or not the pressure switch 21 is ON. If YES, the process proceeds to S31 and the drain pump 14 is stopped.

  If NO is determined in S32, the process proceeds to S33 to determine whether or not the float switch 20 is equal to or higher than the abnormally low set water level. In the case of YES, the process proceeds to S31 and the drain pump 14 is stopped. If NO is determined in S33, the process proceeds to S34, in which it is determined whether or not the sensor 19 has detected an excess of the third set water level LLL (<second set water level LH) (a value higher than the LLL by a differential amount). . When determination is NO, it transfers to S31, the pump 14 is stopped, and the water supply to the steam boiler 2 is not performed.

  If the water level in the drain tank 4 exceeds the third set water level LLL, YES is determined in S34, the process proceeds to S35, and the pressure sensor 18 exceeds the third set pressure PLL lower than the second set pressure PL (differential from the PLL). Whether the value is higher). If it is detected in S35 that the pressure is equal to or lower than the third set pressure PLL, NO is determined, the process proceeds to S31, and the drain pump 14 is stopped. If YES in S35, the process proceeds to S36, and the drain pump 14 is driven.

  In this way, the drain pump 14 is basically driven under the condition that the water level in the drain tank 4 exceeds the third set water level LLL and the pressure exceeds the third set pressure PLL, and the drain pump 4 Drain is supplied to the steam boiler 2. Note that, when the drain pump 14 is stopped by failure, the operation of the steam boiler 2 is continued by driving the auxiliary pump 31 as described above.

(Drain tank pressure control)
Next, pressure control in the drain tank 4 will be described. First, the operation of the third valve V3 will be described with reference to FIG. In S41, the third valve V3 is closed. Next, the process proceeds to S42, where it is determined whether or not the pressure switch 21 (turns ON when the third operating pressure PHH is exceeded and turns OFF when the differential pressure is lowered) is ON. The valve V3 is closed so that the drain tank 4 does not exceed the abnormally high set pressure.

If NO is determined in S42, the process proceeds to S43, and it is determined whether or not the float switch 20 is equal to or lower than the abnormally low set water level. In YES, it transfers to S41 and closes the 3rd valve V3. If NO is determined in S43, the process proceeds to S44, and it is determined whether or not the water level sensor 19 has detected an excess of the third set water level LLL (a value higher than the LLL by a differential amount). When the water level is equal to or lower than the third set water level LLL and NO, the third valve V3 is closed.

  If YES is determined in S44, the process proceeds to S45 to determine whether the pressure sensor 18 exceeds the second set pressure PL that is lower than the abnormally high set pressure and higher than the third set pressure PLL (a value that is higher than the PL by a differential amount). judge. In YES, it transfers to S41 and closes the 3rd valve V3. If it is detected in S45 that the pressure is equal to or lower than the second set pressure PL, NO is determined, the process proceeds to S46, and the third valve V3 is opened.

  In this way, the third valve V3 basically opens under the condition that the water level in the drain tank 4 is equal to or higher than the third set water level LL and the pressure is lower than the second set pressure PL. Steam is supplied into the tank 4 to maintain the pressure in the drain tank 4 at approximately the second set pressure PL.

  Next, the operation of the fourth valve V4 will be described with reference to FIG. In S51, the fourth valve V4 is closed. Referring to FIG. 1, pressure adjusting valve 29 opens when the pressure in drain tank 4 becomes equal to or higher than a set pressure (a value lower than the abnormally high set pressure and higher than the second set pressure PL). Is controlled below the set pressure of the pressure regulating valve 29. However, the pressure rises due to a failure of the pressure regulating valve 29, and the pressure detected by the pressure sensor 18 becomes the first set pressure PH (a value lower than the abnormally high set pressure and higher than the second set pressure PL). If it exceeds (a value higher than the differential by PH), YES is determined in S52, the determination of NO in S53 is made, and the fourth valve V4 is opened in S54.

  If the pressure further increases due to the failure of the fourth valve V4 and the pressure switch 21 detects an abnormally high pressure, the pressure switch 21 is turned on, NO is determined in S53, and the fourth valve V4 is closed. When the pressure switch 21 detects an abnormally high pressure, the system 1 is stopped. Closing the fourth valve V4 is part of the interlock operation. If the interlock state is not set, the fourth valve V4 can be configured to open if YES is determined in S53.

  If the first set pressure PH or lower is detected in S52, NO is determined, the process proceeds to S51, and the fourth valve V4 is closed.

  As described above, the fourth valve V4 basically opens under the condition that the pressure in the drain tank 4 exceeds the first set pressure PH. Therefore, even if the pressure regulating valve 29 fails, the fourth valve V4 passes through the steam release line 10 and drains. The high-pressure steam in the tank 4 is released into the makeup water tank 7 to prevent abnormal high pressure in the drain tank 4.

(Control of heat recovery from flash steam)
Next, heat recovery control from flash steam will be described. First, the operation of the fifth valve V5 will be described with reference to FIG. In S61, the fifth valve V5 is closed. If the drain pump 14 is now driven, the drain in the drain tank 4 circulates through the second circulation line 11B, ensuring a minimum flow of the drain pump 14 and a uniform drain temperature in the drain tank 4. It becomes.

  Next, in S62, it is determined whether or not the pressure switch 21 is ON. If YES, the process proceeds to S61, the fifth valve V5 is closed, and the drain is not injected into the drain tank 4 through the first circulation line 11A.

  In NO, it transfers to S63 and it is determined whether the detected temperature of the temperature sensor 28 is more than 2nd setting temperature THH. If YES is determined in S <b> 33, the process proceeds to S <b> 61, the fifth valve V <b> 5 is closed, and the drain is not ejected into the drain tank 4.

  If NO is determined in S63, the process proceeds to S64, and it is determined whether or not the temperature detected by the temperature sensor 28 is lower than the third set temperature TL. When YES is determined in S64, the process proceeds to S61, the fifth valve V5 is closed, and the drain is not ejected into the drain tank 4. The reason is as follows. If the drain is injected while the drain temperature in the drain tank 4 is low, the pressure in the drain tank 4 decreases, the third valve V3 opens, and steam is prevented from being supplied from the pressurized steam line 9. is there.

  In S64, when a value exceeding the third set temperature TL (a value higher than the TL by a differential value) is detected and NO is determined, the process proceeds to S65, and the pressure in the drain tank 4 exceeds the first set pressure PH. It is determined whether or not (a value higher than the PH by a differential amount). When a pressure equal to or lower than the first set pressure PH is detected, NO is determined in S65, the fifth valve V5 is closed in S61, and the drain is not ejected into the drain tank 4. The reason is as follows. If the drain is injected while the pressure in the drain tank 4 is low, the pressure in the drain tank 4 further decreases, the third valve V3 is opened, and steam is prevented from being supplied from the pressurized steam line 9. is there.

  If it is detected in S65 that the first set pressure PH is exceeded, YES is determined, the process proceeds to S66, and the fifth valve V5 is opened. Then, the drain in the drain tank 4 is ejected from the ejection pipe 26 to the gas phase part of the drain tank 4 through the first circulation line 11A, and the heat of the gas phase part in the drain tank 4 is efficiently recovered by this ejection. High temperature drain can be obtained. Even when the drain is discharged from the second circulation line 11A, the drain is circulated through the second circulation line 11B.

  In this way, the fifth valve V5 basically has a drain temperature in the drain tank 4 of the second set temperature THH or less and a third set temperature TL or more, and the drain tank 4 pressure is the first set pressure. It opens under the condition of exceeding PH, and the drain is ejected from the ejection pipe 26. As a result, it is possible to efficiently recover the heat of the gas phase portion in the drain tank 4 and obtain a high-temperature drain without increasing the drain temperature more than necessary.

(Operation during power failure)
Here, the operation when the power supply of the system 1 is stopped will be described. With reference to FIG. 1, when a power failure occurs, the first valve V1 and the third valve V3 are closed, and the second valve V2 is opened. Since the third valve V3 is closed, the supply of pressurized steam to the drain tank 4 through the pressurizing line 9 is stopped. At the same time, the first valve V1 is closed and the second valve V2 is opened, so that the drain from the drain return line 3 flows into the makeup water tank 7 without flowing into the drain tank 4.

  If the pressure relief valve 29 and the fourth valve V4 do not operate normally, the pressure in the drain tank 4 rises to the operating pressure of the safety valve 37. Finally, the safety valve 37 operates to ensure safety. Secured. However, according to the first embodiment, since the third valve V3 is closed, the first valve V1 is closed, and the second valve V2 is opened, the drain tank by the return drain and the pressurized steam without operating the safety valve 37. The pressure rise of 4 is stopped.

In addition, the drain pump 14 stops at the time of a power failure, and when a large amount of drain flows into the drain tank 4 through the drain return line 3 in this state, the water level of the drain tank 4 rises and the safety valve 37 operates. End up. However, according to the first embodiment, since the inflow of the drain into the drain tank 4 is prevented by closing the first valve V1, the water level of the drain tank 4 is prevented from rising abnormally.

  The present invention is not limited to the first embodiment, but includes the second embodiment of FIG. The second embodiment is different from the first embodiment in that the second circulation line 11A, the first mixer 33, and the second mixer 34 are omitted, and other configurations are the same as those in the first embodiment. The same components are denoted by the same reference numerals, and the description thereof is omitted.

  Further, the present invention is not limited to the first and second embodiments, but includes a modification of the control of the fourth valve V4 shown in FIG. 7 of the first embodiment as shown in FIG. Since other hardware and software configurations are the same as those in the first embodiment, the same configurations as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  In the drain tank pressure control procedure of the third embodiment, when the pressure sensor 18 detects a second operating pressure PH higher than the first operating pressure of the pressure regulating valve 29, the fourth valve V4 is opened and the pressure switch 21 is operated second. This is a control procedure for opening the fourth valve V4 when a third operating pressure PHH higher than the pressure PH is detected.

  The operation of the fourth valve V4 in the third embodiment will be described with reference to FIG. In S71, the fourth valve V4 is opened. Referring to FIG. 1, pressure regulating valve 29 opens when the pressure in drain tank 4 exceeds the first operating pressure, so that the pressure in drain tank 4 is equal to or lower than the first operating pressure of pressure regulating valve 29. It is controlled. However, when the pressure rises beyond the first operating pressure due to reasons such as failure of the pressure regulating valve 29, the pressure sensor 18 detects the second operating pressure PH higher than the first operating pressure, and the fourth in S72. Open valve V4.

  If the pressure further increases due to the failure of the pressure sensor 18, the pressure switch 21 is closed at the third operating pressure PHH, YES is determined in S73, and the fourth valve V4 is opened. Note that the opening / closing characteristics of closing when the pressure of the pressure switch 21 increases and opening when the pressure switch 21 may be reversed.

  If the first set pressure PH or lower is detected in S73, NO is determined, the process proceeds to S74, and the fourth valve V4 is closed.

  Thus, the fourth valve V4 basically opens under the condition that the pressure in the drain tank 4 exceeds the first set pressure PH, so that even if the pressure regulating valve 29 fails, the fourth valve V4 passes through the pressure relief line 10 and drains. The high-pressure steam in the tank 4 is released into the makeup water tank 7 to prevent abnormal high pressure in the drain tank 4. Even if the pressure sensor 18 breaks down, the pressure switch 21 opens the fourth valve V4, so that an abnormally high pressure in the drain tank 4 is prevented.

1 Drain recovery system 2 Steam boiler 3 Drain return line 4 Drain tank 5 Supply water line 6 Drain supply line 7 Supply water tank 8 Drain relief line 12 Controller (control means)
13 Load equipment 14 Drain pump 28 Pressure regulating valve (pressure relief valve)
V1 1st valve (drain return valve)
V2 Second valve (drain relief valve)
V3 3rd valve (pressurizing valve)

Claims (2)

A steam boiler that supplies steam to a load device, a drain that stores drain discharged from the load device through a drain return line, and supplies the drain that has been stored through the drain supply line having a drain pump to the steam boiler From the steam boiler, a tank and a replenishing water tank that supplies replenishing water to the drain tank through a replenishing water line having a replenishing water pump, and a pressure valve that opens and closes according to the pressure in the drain tank. A pressurized steam line that supplies high-pressure steam to the drain tank; and a pressure relief line that has a pressure relief valve that opens when the pressure in the drain tank rises, and that allows steam to escape from the drain tank to the makeup water tank. A drain collection system,
An openable / closable drain return valve provided in the drain return line;
An openable / closable drain relief valve provided in a drain relief line connected between the upstream side of the drain return valve and the makeup water tank;
The drain recovery system according to claim 1, wherein the drain return valve and the pressurizing valve are valves that are closed when energization is stopped, and the drain relief valve is a valve that is opened when the energization is stopped. A preliminary water supply line having an auxiliary pump connecting the makeup water tank and the steam boiler;
2. The drain recovery system according to claim 1, wherein when the water supply to the steam boiler by the drain pump is not normally performed at the time of a power failure of the system, the auxiliary pump is driven.

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