JP2019086230A - Drain recovery system and drain recovery method - Google Patents

Abstract

To reduce residual drain in a device.SOLUTION: A drain recovery system 100 comprises: a heater roll 1 using steam; a steam pipe 2 supplying steam to the heater roll 1; a high-pressure drain pipe 3 in which drain discharged from the heater roll 1 circulates; a low-pressure drain pipe 4 in which drain of lower pressure than the drain circulating the high-pressure drain pipe 3 circulates; a communication pipe 51 communicating between the high-pressure drain pipe 3 and the low-pressure drain pipe 4; a first blow valve 53 for switching an activated/inactivated state of the communication pipe 51; and a control unit 6 for controlling the first blow valve 53. The control units 6 opens the first blow valve 53 as stopping supplying steam to the heater roll 1, to thereby make the communication pipe 51 activated.SELECTED DRAWING: Figure 1

Description

  The technology disclosed herein relates to a drain recovery system and a drain recovery method.

  BACKGROUND Conventionally, a drain recovery system for recovering drain is known. For example, in the drain recovery system disclosed in Patent Document 1, the apparatus is supplied with steam via a steam supply line, and the steam is used in this apparatus. The drain generated by condensation in the device is recovered to the drain tank via the drain recovery line.

JP, 2017-172838, A

  By the way, when the operation of the entire system is stopped, the supply of steam to the device is stopped. When the supply of steam is stopped, the pressure difference between the upstream side (i.e., the steam side) of the device and the downstream side (i.e., the drain side) of the device decreases. As a result, drainage is not easily discharged from the device and tends to remain. If drain remains in the device, it will take time to drain the residual drain when resuming operation, which will take time to resume. Furthermore, if the residual drain in the device freezes in a cold area or the like, the device may be damaged.

  The technique disclosed herein has been made in view of such circumstances, and the purpose thereof is to reduce the residual drain in the device.

  The drain recovery system disclosed herein comprises an apparatus using steam, a steam pipe for supplying steam to the apparatus, a first drain pipe through which drain discharged from the apparatus flows, and the first drain pipe. A second drain pipe in which a drain having a lower pressure than the draining drain flows, a communication pipe connecting the first drain pipe and the second drain pipe, and a first valve switching the open / close of the communication pipe; And a control unit for controlling the first valve, the control unit opening the first valve and opening the communication pipe in response to a stop of supply of steam to the device.

  The drain recovery method disclosed herein comprises a device using steam, a steam pipe for supplying steam to the device, and a first drain pipe through which the drain discharged from the device flows. A recovery method, comprising: a step of determining a supply stop of steam to the device; and a drain having a lower pressure than a drain flowing through the first drain pipe flowing along with the supply stop of the steam to the device And (2) connecting the first drain pipe to the drain pipe.

  According to the drain recovery system, residual drain in the device can be reduced.

  According to the drain recovery method, residual drain in the device can be reduced.

FIG. 1 is a piping diagram of a drain recovery system. FIG. 2 is a flowchart of the stop operation of the drain recovery system. FIG. 3 is a diagram showing the flow of drain during the first stop operation in the drain recovery system. FIG. 4 is a diagram showing the flow of drain during the second stop operation in the drain recovery system. FIG. 5 is a timing chart in the stop operation.

  Hereinafter, exemplary embodiments will be described with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a drain recovery system.

  The drain recovery system 100 includes a heater roll 1 using steam, a steam pipe 2 supplying steam to the heater roll 1, a high pressure drain pipe 3 through which drain discharged from the heater roll 1 flows, and a high pressure drain pipe 3 A low pressure drain pipe 4 through which a low pressure drain flows than a draining drain, a communication pipe 51 connecting the high pressure drain pipe 3 and the low pressure drain pipe 4, and a first blow valve 53 switching the open / close of the communication pipe 51 A second blow valve 54 for opening the high pressure drain pipe 3 to the atmosphere and a control unit 6 for controlling the first blow valve 53 and the second blow valve 54 are provided.

  The steam pipe 2 has a steam main flow pipe 20 and a branch pipe 21 branched from the steam main flow pipe 20 and connected to the heater roll 1. The steam pipe 2, more specifically, the steam mainstream pipe 20 is connected to the boiler 7, and the steam generated by the boiler 7 is in circulation. The steam pipe 2 may be connected to a steam header instead of the boiler 7.

  Steam is supplied to the inside of the heater roll 1 via a branch pipe 21. The heater roll 1 heats an object in contact with the outer peripheral surface thereof. Inside the heater roll 1, the steam condenses to generate a drain. The heater roll 1 is an example of an apparatus using steam.

  The high pressure drain pipe 3 has a drain main flow pipe 30 and a connection pipe 31 for joining the drain discharged from the heater roll 1 to the high pressure drain pipe 30. The drain main flow pipe 30 is disposed at a position higher than the heater roll 1. The drain main flow pipe 30 is provided with a pressure sensor 35 for detecting the pressure of the drain flowing through the high pressure drain pipe 3. The drain generated by the heater roll 1 is discharged through the connection pipe 31 and flows into the drain main flow pipe 30. The connection pipe 31 is provided with a drain trap 33 for passing the drain while preventing the passage of steam. Furthermore, on the downstream side of the drain trap 33, the connection pipe 31 is provided with a check valve 34 that allows the flow toward the drain main flow pipe 30 and blocks the flow in the opposite direction. The drain main flow pipe 30 is an example of a main flow pipe.

  The communication pipe 51 connects the drain main flow pipe 30 and the low pressure drain pipe 4. The first blow valve 53 is provided in the communication pipe 51. By opening the first blow valve 53, the communication pipe 51 is opened, and the high pressure drain pipe 3 and the low pressure drain pipe 4 communicate with each other. On the other hand, when the first blow valve 53 is closed, the communication pipe 51 is shut off, and the high pressure drain pipe 3 and the low pressure drain pipe 4 are shut off.

  The blow pipe 52 is branched from a portion of the connection pipe 31 downstream of the drain trap 33. The downstream end of the blow pipe 52 is connected to the drain pot 84 and is open to the atmosphere. The second blow valve 54 is provided in the blow pipe 52. The second blow valve 54 switches the open / close of the blow pipe 52. As the second blow valve 54 is opened, the blow pipe 52 is opened, and the connection pipe 31 and hence the high pressure drain pipe 3 are opened to the atmosphere. On the other hand, when the second blow valve 54 is closed, the blow pipe 52 is shut off, and the connection pipe 31 and hence the high pressure drain pipe 3 are shut off from the atmosphere.

  The drain trap 33 is disposed at a lower position than the drain main flow pipe 30. The blow pipe 52 is connected to a portion of the connection pipe 31 lower than the drain main flow pipe 30, and the second blow valve 54 is also disposed at a position lower than the drain main flow pipe 30.

  The high pressure drain pipe 3 is an example of a first drain pipe, and the low pressure drain pipe 4 is an example of a second drain pipe. The first blow valve 53 is an example of a first valve, and the second blow valve 54 is an example of a second valve.

  The downstream end of the drain main flow pipe 30 is connected to the first pump 81. The first pump 81 is, for example, an ejector pump, and supplies drain to the boiler 7. The downstream end of the low pressure drain pipe 4 is connected to a water storage tank 83. The drain stored in the water storage tank 83 is supplied to the boiler 7 via the second pump 82. The second pump 82 is, for example, an electric pump. Thus, the drain recovery system 100 constitutes a part of a steam system including the boiler 7, the water supply tank 83, the first pump 81, and the second pump 82.

  The control unit 6 is formed of a processor. The control unit 6 receives the detection result of the pressure sensor 35. The control unit 6 controls the first blow valve 53 and the second blow valve 54.

  Subsequently, the operation of the drain recovery system 100 will be described.

  First, an operation of the drain recovery system 100 in normal operation in which steam is supplied to the heater roll 1 (hereinafter, referred to as “normal operation”) will be described. In normal operation, steam and drain flow as indicated by the thick arrows in FIG. The thick broken line represents the flow of steam, and the thick solid line represents the flow of drain.

  Specifically, the steam generated by the boiler 7 flows through the steam mainstream pipe 20 and a part thereof is supplied to the heater roll 1 through the branch pipe 21. The vapor supplied to the heater roll 1 exchanges heat with the object contacting the heater roll 1 and condenses to become a drain.

  The drain generated by the heater roll 1 is discharged from the heater roll 1 via the connection pipe 31. The drain passes through the drain trap 33 and the check valve 34 and flows into the drain main flow pipe 30. The drain that has flowed into the drain main flow pipe 30 flows through the drain main flow pipe 30 and is supplied to the boiler 7 by the first pump 81. The boiler 7 heats the drain to generate steam.

  In the normal operation, the first blow valve 53 and the second blow valve 54 are fully closed.

  Next, the operation of the drain recovery system 100 when the supply of steam to the heater roll 1 is stopped (hereinafter, referred to as “stop operation”) will be described. In the stop operation, the drain recovery system 100 first performs the first stop operation, and then performs the second stop operation. FIG. 2 is a flowchart of the stop operation of the drain recovery system 100. FIG. 3 is a view showing the flow of drain during the first stop operation in the drain recovery system 100, and FIG. 4 is a view showing the flow of drain during the second stop operation in the drain recovery system 100.

  Specifically, in step S1, the control unit 6 determines whether the vapor supply to the heater roll 1 has been stopped. For example, when the control unit other than the control unit 6 controls the boiler 7, the control unit 6 supplies steam by receiving a signal indicating stop of the boiler 7 from another control unit. Is determined to have been stopped. Alternatively, when the control unit 6 also controls the boiler 7, the control unit 6 determines that the steam supply has been stopped when the boiler 7 is stopped. In addition, when the steam header is provided on the downstream side of the boiler 7, the control unit 6 determines that the steam supply is stopped when the valve for adjusting the flow rate of steam from the steam header is fully closed. You may Step S1 is an example of the process which determines supply stop of steam.

  The control unit 6 repeats step S1 and monitors the stop of the vapor supply to the heater roll 1.

  When the steam supply is stopped, the control unit 6 executes the first stop operation in step S2. Specifically, the control unit 6 opens the first blow valve 53. When the first blow valve 53 is opened, as shown in FIG. 3, the drain discharged from the heater roll 1 flows in the order of the connection pipe 31, the drain main flow pipe 30, and the communication pipe 51 to the low pressure drain pipe 4. To flow. The drain that has flowed into the low pressure drain pipe 4 flows into the storage tank 83. Step S2 is an example of the process which makes a 2nd drain pipe connect a 1st drain pipe.

  Thereafter, in step S3, the control unit 6 determines whether the pressure Ph of the high pressure drain pipe 3 is equal to or less than a predetermined pressure threshold Pa, based on the detection result of the pressure sensor 35. The pressure threshold Pa is set to a pressure lower than the set pressure of the high pressure drain pipe 5 in the normal operation and higher than the set pressure of the low pressure drain pipe 4 in the normal operation. For example, the set pressure of the low pressure drain pipe 4 in the normal operation is the atmospheric pressure, and the pressure threshold Pa is a pressure slightly higher than the atmospheric pressure. The controller 6 maintains the first blow valve 53 in the open state until the pressure Ph of the high pressure drain pipe 3 becomes equal to or less than the pressure threshold Pa.

  When the pressure Ph of the high pressure drain pipe 3 becomes equal to or less than the pressure threshold Pa, the control unit 6 executes the second stop operation in step S4. Specifically, the control unit 6 opens the second blow valve 54. When the second blow valve 54 is opened, as shown in FIG. 4, the drain discharged from the heater roll 1 flows in the order of the connection pipe 31 and the blow pipe 52 and flows into the drain pot 84. Step S4 is an example of the process of opening the first drain pipe to the atmosphere.

  Thus, the control unit 6 completes the stopping operation.

  The pressure change of the steam pipe 2, the high pressure drain pipe 3 and the low pressure drain pipe 4 in such a stop operation will be described with reference to FIG. FIG. 5 is a timing chart in the stop operation. Specifically, FIG. 5 shows the opening and closing of the first blow valve 53, the opening and closing of the second blow valve 54, the presence or absence of steam supply, and the pressure changes of the steam pipe 2, the high pressure drain pipe 3 and the low pressure drain pipe 4. .

  First, when the supply of steam to the heater roll 1 is stopped at time t1, the first blow valve 53 is opened. At this time, the second blow valve 54 remains closed. When the steam supply is stopped, the heat of the steam is absorbed by the pipe and the heater roll 1 and the pressure Ps of the steam pipe 2 gradually decreases. Although the pressure Ph of the high pressure drain pipe 3 also decreases, the pressure decrease rate (that is, the decrease rate) of the steam pipe 2 is faster than the pressure decrease rate of the high pressure drain pipe 3. Therefore, if the first blow valve 53 is not opened as described above, the differential pressure ΔP between the steam pipe 2 and the high pressure drain pipe 3 becomes smaller. When the differential pressure ΔP becomes smaller, the drain is less likely to be discharged from the heater roll 1 and the drain tends to remain on the heater roll 1. When the supply of steam is resumed and the heating by the heater roll 1 is restarted, it is necessary to drain the drain of the heater roll 1. When the residual drain of the heater roll 1 is large, the time required to restart heating by the heater roll 1 becomes long. Furthermore, if the residual drain of the heater roll 1 freezes in a cold area or the like, parts such as a strainer may be damaged.

  On the other hand, by opening the first blow valve 53, the high pressure drain pipe 3 communicates with the low pressure drain pipe 4, and the pressure reduction rate of the high pressure drain pipe 3 becomes large. Thereby, the differential pressure ΔP between the steam pipe 2 and the high pressure drain pipe 3 is maintained. As a result, discharge of drain from the heater roll 1 is promoted.

  Eventually, when the pressure Ph of the high pressure drain pipe 3 approaches the pressure Pl of the low pressure drain pipe 4, the pressure Ph of the high pressure drain pipe 3 does not easily decrease, and the differential pressure ΔP between the steam pipe 2 and the high pressure drain pipe 3 decreases. It will Further, since the heater roll 1 is disposed at a lower position than the drain main flow pipe 30, a pressure corresponding to a water head from the heater roll 1 to the drain main flow pipe 30 acts on the heater roll 1. This also makes it easy for the drain to remain on the heater roll 1.

  Therefore, at time t2 when the pressure Ph of the high pressure drain pipe 3 reaches the pressure threshold Pa, the second blow valve 54 is opened. As a result, the pressure Ph of the high pressure drain pipe 3 is further reduced, and the differential pressure ΔP between the steam pipe 2 and the high pressure drain pipe 3 is secured. As a result, even if the pressure Ph of the high pressure drain pipe 3 approaches the pressure Pl of the low pressure drain pipe 4, draining of the drain from the heater roll 1 is promoted. Further, since the entire blow pipe 52 including the connection portion to the connection pipe 31 is disposed at a position lower than the drain main flow pipe 30, the water head acting on the heater roll 1 from the downstream side can be reduced. More specifically, since the entire blow pipe 52 is disposed at a lower position than the heater roll 1, it is possible to eliminate the water head acting on the heater roll 1 from the downstream side.

  Thus, the residual drain of the heater roll 1 after the supply of steam is stopped can be reduced. As a result, resumption of the operation of the heater roll 1 after resumption of steam supply can be realized at an early stage. Moreover, in a cold area etc., damage to parts of the heater roll 1 due to freezing of the residual drain can be prevented.

  As described above, the drain recovery system 100 includes the heater roll 1 (apparatus) using steam, the steam pipe 2 for supplying the steam to the heater roll 1, and the high pressure drain pipe through which the drain discharged from the heater roll 1 flows. 3 (the first drain pipe), the low pressure drain pipe 4 (the second drain pipe) through which the drain having a lower pressure than the drain flowing through the high pressure drain pipe 3 flows, and the high pressure drain pipe 3 and the low pressure drain pipe 4 A communication pipe 51, a first blow valve 53 (first valve) that switches opening / closing of the communication pipe 51, and a control unit 6 that controls the first blow valve 53 are provided. When the supply of steam is stopped, the first blow valve 53 is opened to open the communication pipe 51.

  In other words, the drain recovery method in the drain recovery system 100 includes the step of determining the supply stop of the steam to the heater roll 1 (device) and the stop of the supply of the steam to the heater roll 1. (1) connecting the high pressure drain pipe 3 to the low pressure drain pipe 4 (second drain pipe) in which the drain having a lower pressure than the drain flowing through the (1 drain pipe) flows.

  According to this configuration, since the first blow valve 53 is opened with the stop of the supply of steam, the pressure drop of the high pressure drain pipe 3 is promoted, and the differential pressure of the steam pipe 2 and the high pressure drain pipe 3, ie, the heater roll The differential pressure between the upstream side and the downstream side of 1 is secured. Thereby, the draining of the drain from the heater roll 1 is promoted, and the residual drain of the heater roll 1 is reduced.

  Furthermore, the drain recovery system 100 further includes a second blow valve 54 (second valve) that opens the high pressure drain pipe 3 to the atmosphere, and the control unit 6 causes the second blow valve to open after the first blow valve 53 is opened. Open 54

  In other words, the drain recovery method in the drain recovery system 100 further includes the step of opening the high pressure drain pipe 3 to the atmosphere after communication with the high pressure drain pipe 3 and the low pressure drain pipe 3.

  According to this configuration, even if the pressure of the high pressure drain pipe 3 does not easily decrease after the first blow valve 53 is opened, the pressure of the high pressure drain pipe 3 is further reduced by opening the second blow valve 54. become. Since the differential pressure between the steam pipe 2 and the high pressure drain pipe 3 is secured even if the pressure of the high pressure drain pipe 3 decreases, the draining of the drain from the heater roll 1 is further promoted.

  Further, the control unit 6 opens the second blow valve 54 when the pressure of the high pressure drain pipe 3 becomes equal to or less than a predetermined pressure threshold Pa.

  According to this configuration, the second blow valve 54 is maintained in the closed state for a while after the first blow valve 53 is opened. When the pressure in the high pressure drain pipe 3 is reduced to a certain extent, the second blow valve 54 is opened. In other words, while the pressure of the high pressure drain pipe 3 is high, the second blow valve 54 remains closed. For example, the second blow valve 54 is opened when the pressure of the high pressure drain pipe 3 decreases to such a pressure that the drain does not rapidly re-evaporate even if the high pressure drain pipe 3 is opened to the atmosphere.

  Furthermore, the high pressure drain pipe 3 has a drain main flow pipe 30 (main flow pipe) and a connection pipe 31 connecting the heater roll 1 and the drain main flow pipe 30. The heater roll 1 is lower than the drain main flow pipe 30 The second blow valve 54 is disposed at a position lower than the drain main flow pipe 30 in the connection pipe 31.

  According to this configuration, a pressure corresponding to a water head from the heater roll 1 to the height of the drain main flow pipe 30 acts on the heater roll 1. Since the second blow valve 54 is provided at a lower position than the drain main flow pipe 30, the above-described water head can be reduced to facilitate the draining of the drain from the heater roll 1.

<< Other Embodiments >>
As mentioned above, the said embodiment was described as an illustration of the technique disclosed in this application. However, the technology in the present disclosure is not limited to this, and is also applicable to embodiments in which changes, replacements, additions, omissions, and the like are appropriately made. Moreover, it is also possible to combine each component demonstrated by the said embodiment, and to set it as a new embodiment. Further, among components described in the attached drawings and the detailed description, not only components that are essential for solving the problem but also components that are not essential for solving the problem in order to illustrate the above-mentioned technology. May also be included. Therefore, the fact that those non-essential components are described in the attached drawings and the detailed description should not immediately mean that those non-essential components are essential.

  The following configuration may be adopted for the embodiment.

  For example, an apparatus using steam is not limited to the heater roll 1. Any device that uses steam and generates drain can be employed.

  The above-mentioned composition of drain recovery system 100 is only an example, and is not limited to this. For example, the heater roll 1 is disposed at a position lower than the drain main flow pipe 30 of the high pressure drain pipe 3, but is not limited thereto. Moreover, although the drain recovery system 100 is integrated in the steam system, it is not limited to this. Further, the configuration of the steam system is not limited to the above-described configuration including the boiler 7, the water supply tank 83, the first pump 81, and the second pump 82.

  The timing at which the first blow valve 53 is opened can be set arbitrarily as long as the supply of steam is stopped. For example, the opening of the first blow valve 53 may be simultaneous with the supply stop of the steam, may be after a while after the supply stop of the steam, or may be immediately before the supply stop of the steam.

  Further, the timing at which the second blow valve 54 is opened can be arbitrarily set as long as the first blow valve 53 is opened. For example, the second blow valve 54 may be opened when the pressure Ps of the steam pipe 2, the pressure Ph of the high pressure drain pipe 3, and the differential pressure ΔP become less than or equal to a predetermined differential pressure threshold.

  As described above, the technology disclosed herein is useful for a drain recovery system and a drain recovery method.

100 drain recovery system 1 heater roll (apparatus)
2 Steam pipe 3 High pressure drain pipe (1st drain pipe)
30 drain main flow pipe (main flow pipe)
31 connection pipe 4 low pressure drain pipe (second drain pipe)
51 communication pipe 53 first blow valve (first valve)
54 2nd blow valve (2nd valve)
6 Control unit

Claims (6)

A device that uses steam,
A steam pipe for supplying steam to the device;
A first drain pipe through which drain discharged from the device flows;
A second drain pipe through which drain having a lower pressure than the drain flowing through the first drain pipe flows;
A communicating pipe for connecting the first drain pipe and the second drain pipe;
A first valve that switches opening / closing of the communication pipe;
And a controller configured to control the first valve.
The said control part opens the said 1st valve with the supply stop of the vapor | steam to the said apparatus, and makes the said communicating pipe open, The drain collection | recovery system characterized by the above-mentioned. In the drain recovery system according to claim 1,
The system further comprises a second valve for opening the first drain pipe to the atmosphere,
The drain recovery system, wherein the control unit opens the second valve after the first valve is opened. In the drain recovery system according to claim 2,
The control unit is configured to set the pressure when the pressure of the first drain pipe falls below a predetermined pressure threshold or when the differential pressure between the steam pipe and the first drain pipe falls below a predetermined differential pressure threshold. A drain recovery system characterized by opening a second valve. In the drain recovery system according to claim 2 or 3,
The first drain pipe includes a main flow pipe, and a connection pipe that connects the device and the main flow pipe.
The device is located below the main flow pipe,
The said 2nd valve is provided in the position lower than the said mainstream pipe in the said connection pipe, The drain collection | recovery system characterized by the above-mentioned. A drain recovery method in a drain recovery system, comprising: a device using steam; a steam pipe supplying steam to the device; and a first drain pipe through which a drain discharged from the device flows.
Determining the stop of the supply of steam to the device;
Connecting the first drain pipe to a second drain pipe through which a drain having a lower pressure than the drain flowing through the first drain pipe flows in accordance with the supply stop of the steam to the device. Characteristic drain collection method. In the drain recovery method according to claim 5,
The method according to claim 1, further comprising the step of opening the first drain pipe to the atmosphere after the first drain pipe is in communication with the second drain pipe.

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