JP2016008724A - Drain recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a drive state of a drain pump irrespectively of a variation in drain header pressure.SOLUTION: A drain recovery system comprises: a steam boiler supplying steam to a load device; a drain tank 1 storing drain discharged from the load device; a drain pump 7 connected to a drain supply line 5 connecting the steam boiler to the drain tank 1; detection means 10 provided between the drain pump 7 and the drain tank 1 in the drain supply line 5 and detecting a specific parameter indicating a state of the flowing drain; and control means 11 controlling the drain pump 7 to be driven on the basis of a detection value by the detection means 10.

Description

  The present invention relates to a drain recovery system.

  Conventionally, a drain recovery system is known in which drain (condensed water) discharged from a load device is recovered in a sealed drain tank, and the recovered drain is returned to a steam boiler by driving a drain pump ( For example, see Patent Document 1).

  However, in the conventional drain recovery system, the drain pump is only controlled by an inverter. For this reason, the discharge capacity of the drain pump may vary due to fluctuations in the drain header pressure (pump primary pressure). In particular, there is a possibility that the ink cannot be discharged by cavitation.

JP 2012-9887 A

  An object of the present invention is to provide a drain recovery system that can stabilize the driving state of the drain pump regardless of fluctuations in the drain header pressure.

As a means for solving the above problems, the present invention provides:
A steam boiler for supplying steam to the load equipment;
A drain tank for storing drain discharged from the load device;
A drain pump connected to a drain supply line connecting the steam boiler and the drain tank;
Among the drain supply lines, a detection means provided between the drain pump and the drain tank for detecting a specific parameter indicating the state of the flowing drain,
Control means for driving and controlling the drain pump based on a value detected by the detection means;
A drain recovery system is provided.

  With this configuration, by automatically controlling the driving of the drain pump, it is possible to stabilize the driving state of the drain pump regardless of fluctuations in the primary pressure.

  The detection means may be a pressure sensor that detects the pressure of the drain.

  The detection means may be a flow rate sensor that detects the flow rate of the drain.

  The control means preferably controls the drive of the drain pump on the condition that cavitation does not occur in the drain pump based on the detection signal from the detection means.

  With this configuration, the drain pump can always be driven in a stable state.

  The control means may perform PID control of the drain pump so that the detection value of the detection means becomes a target value that satisfies a condition in which cavitation does not occur in the drain pump.

  According to the present invention, since the drain pump is automatically driven and controlled based on the secondary pressure, the driving state of the drain pump can be stabilized regardless of the fluctuation of the primary pressure.

It is a mimetic diagram showing a drain recovery system concerning this embodiment.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In addition, the following description is only illustrations essentially and does not intend restrict | limiting this invention, its application thing, or its use. Further, the drawings are schematic, and the ratio of each dimension is different from the actual one.

FIG. 1 shows a drain recovery system according to this embodiment. The drain recovery system is provided with a closed drain tank 1.
The drain discharged from the load device 3 through the drain return line 2 is collected in the drain tank 1. The first valve 4 is connected in the middle of the drain recovery line, and the flow rate of the drain returning to the drain tank 1 is limited. The drain discharged from the load device 3 is generated when the steam generated in the evaporation tank 6 is supplied to the load device 3 and heat is exchanged there.

  The drain stored in the drain tank 1 is returned to the evaporation tank 6 through the drain supply line 5. The drain supply line 5 is connected to the lower part of the drain tank 1. In the middle of the drain supply line 5, a drain pump 7, a check valve 8, and a second valve 9 are connected in order from the drain tank 1 side. The pressure on the downstream side of the drain pump 7 (between the drain pump 7 and the check valve 8) is detected by a pressure sensor 10 which is an example of a detection unit. The pressure detected by the pressure sensor 10 is one of the parameters indicating the state of the drain discharged from the drain tank 1 and is input to the controller 11.

  The middle of the drain supply line 5 (between the drain pump 7 and the check valve 8) and the drain pump 7 are connected by a drain circulation line 12. The drain pump 7 can be cooled by circulating the drain in the drain tank 1 through the drain circulation line 12. Therefore, the circulation amount is set to be equal to or higher than the flow rate required for drain pump cooling.

  Connected to the upper part of the drain tank 1 is a pressurized steam line 13 branched from a line from the evaporation tank 6 to the load device 3. The pressurized steam line 13 supplies pressurized steam having a predetermined pressure exceeding the atmospheric pressure to the drain tank 1 from a steam boiler (including a steam header provided at the steam outlet of the steam boiler). A third valve 14 is connected in the middle of the pressurized steam line 13, and the pressure in the drain tank 1 is maintained at a predetermined pressure by opening and closing the third valve 14.

  The drain tank 1 is supplied with water from a supply water tank (not shown) via a supply water line 15 connected to the lower part of the drain tank 1. The makeup water line 15 is provided with a makeup water pump (not shown). The drain tank 1 is provided with a water level detector 16. Connected to the upper portion of the drain tank 1 is a pressure relief line 17 that communicates with the upper portion of the makeup water tank. When the pressure in the gas phase portion of the drain tank 1 exceeds a set value, the pressure can be exhausted through the pressure relief line 17.

  The controller 11 performs PID control on the driving of the drain pump 7 based on the detected pressure input from the pressure sensor 10. Here, an existing control device can be used as the controller 11. Examples of the control device that can be used include a temperature controller used to adjust the temperature of the evaporation tank 6, an inverter for controlling the drain pump 7, and the like. Further, a signal is input to the controller 11 from a water level detector 16 that detects the water level in the drain tank 1. Based on this signal, the controller 11 adjusts the amount of makeup water supplied from the outside and the amount of water supplied to the evaporation tank 6 by drivingly controlling the makeup water pump, the third valve, and the like.

Next, the operation of the drain recovery system having the above configuration will be described.
If there is an input of a detection signal indicating that the water level in the drain tank 1 has exceeded the set water level by the water level detector 16, the controller 11 opens the second valve 9. Further, the driving of the drain pump 7 is started. Thereby, the water stored in the drain tank 1 is returned to the evaporation tank 6. At this time, based on the water pressure on the secondary side (downstream of the drain pump 7) of the drain supply line 5 detected by the pressure sensor 10, the drain pump 7 is driven by PID control so that the water pressure becomes the set target pressure. Adjust the frequency. Here, as the set target pressure, a value that can secure a suction pressure at which no cavitation occurs in the drain pump 7 is used. As a result, even if the primary pressure of the drain pump 7, that is, the required suction head (required NPSH) varies, the driving state of the drain pump 7 can be stabilized.

  As described above, since the drain pump 7 is driven and controlled based on the water pressure on the secondary side of the drain supply line 5, the driving state of the drain pump 7 is automatically stabilized regardless of the fluctuation of the primary pressure. Can be made. Moreover, even if the effective suction head (available NPSH: available Net Positive Suction Head) is not so large, the drain pump 7 can be used safely. Furthermore, there is no need to pressurize the drain tank 1, and the pressurized steam line 13 can be dispensed with.

In addition, this invention is not limited to the structure described in the said embodiment, A various change is possible.
In the above embodiment, the secondary pressure of the drain pump 7 is detected by the pressure sensor 10 as a parameter indicating the state of the drain, and the drain pump 7 is driven and controlled based on the detected pressure. Instead of this, it is also possible to provide a flow rate sensor and drive and control the drain pump 7 based on the flow rate detected by the flow rate sensor.

  Moreover, in the said embodiment, although the drain pump 7 was PID-controlled, if the drive state of the drain pump 7 can be stabilized based on the parameter which shows the state of drains, such as detected pressure and a detected flow volume. Other control methods such as PI control and duty control can also be employed.

DESCRIPTION OF SYMBOLS 1 ... Drain tank 2 ... Drain return line 3 ... Load apparatus 4 ... 1st valve 5 ... Drain supply line 6 ... Evaporation tank 7 ... Drain pump 8 ... Check valve 9 ... 2nd valve 10 ... Pressure sensor (detection means)
11 ... Controller (control means)
DESCRIPTION OF SYMBOLS 12 ... Drain circulation line 13 ... Pressurized steam line 14 ... 3rd valve 15 ... Supply water line 16 ... Water level detector 17 ... Pressure relief line

Claims (5)

A steam boiler for supplying steam to the load equipment;
A drain tank for storing drain discharged from the load device;
A drain pump connected to a drain supply line connecting the steam boiler and the drain tank;
Among the drain supply lines, a detection means provided between the drain pump and the drain tank for detecting a specific parameter indicating the state of the flowing drain,
Control means for driving and controlling the drain pump based on a value detected by the detection means;
A drain collection system characterized by comprising:   The drain recovery system according to claim 1, wherein the detection unit is a pressure sensor that detects a pressure of the drain.   The drain recovery system according to claim 1, wherein the detection unit is a flow rate sensor that detects a flow rate of the drain.   4. The control unit according to claim 1, wherein the control unit controls driving of the drain pump under a condition in which cavitation does not occur in the drain pump, based on a detection signal from the detection unit. 5. The drain collection system described.   The said control means performs said PID control of the said drain pump so that the detected value by the said detection means may become the target value which satisfies the conditions where cavitation does not generate | occur | produce in the said drain pump. The drain collection system of any one of these.

Images