JP4923599B2 - Chemical injection device - Google Patents

Description

  The present invention relates to a chemical injection device that injects a chemical into a liquid flow of a main liquid. In particular, the present invention relates to a chemical injection device that injects a chemical solution for water quality control such as pH adjustment into the makeup water supplied to the boiler in a boiler water supply system for a power plant.

  A boiler water supply system of a power plant is equipped with a chemical injection device that injects a chemical solution such as a pH adjuster (amine or the like) into the water supply to control the water quality. In such a chemical injection device, a chemical liquid channel extending from the chemical liquid tank is connected to the water supply channel. And a chemical | medical solution is pumped up from a chemical | medical solution tank with a pump, and a chemical | medical solution is inject | poured into a water supply flow path through a chemical | medical solution flow path.

  The required amount of chemical solution such as a pH adjusting agent varies depending on the amount of makeup water. In conventional high-pressure boilers, the replenishment water ratio is stable at about 50 to 100%, so use a general plunger-type metering pump and adjust the amount of water added to achieve optimum water quality. It was.

  By the way, in recent years, with changes in the industrial structure, the demand (operation request) of boilers has been greatly different between day and night. For example, there may be an extremely large difference between the amount of steam generated by the boiler being 100% during the day and 30% at night. Thereby, depending on the recovery condition of the boiler drain, the amount of makeup water may be as large as 100 to 10% during the day and night.

  As described above, when the amount of makeup water is large, chemical solution injection proportional to the amount of makeup water is required. Therefore, the difference in the amount of makeup water increases, for example, the maximum amount of chemical solution added is five times the minimum amount added. In such a case, a single pump cannot cope with such fluctuations in pumping amount. For example, in inverter control, control at 20 to 100% is the limit. Therefore, when the amount of addition should be reduced to less than 20%, if the chemical solution is continuously injected at 20%, which is the lower limit, excessive injection occurs, and the quality of boiler feed water varies. In such a case, in a small addition amount range, it is conceivable to perform intermittent injection by operating the pump on and off. However, in the case of a motor-driven plunger pump generally used in a power plant boiler, the ON-OFF interval needs to be 30 seconds or longer in order to stably operate the pump. Thus, there is a problem that when the interval becomes large, the fluctuation of water quality tends to increase.

  Furthermore, there is also known a method that supports a small capacity range by combining inverter control and plunger variable stroke with a single pump, but pumps capable of variable stroke are generally expensive and complex in structure, There are problems in terms of economy and maintenance.

  By the way, in a muddy water treatment system etc., the proposal of using 2 pumps and adding a chemical | medical agent is made | formed (for example, refer patent document 1 and patent document 2). However, in the muddy water treatment system described in these documents, two pumps are used to inject different chemical solutions.

JP-A-8-299706 JP-A-10-99605

  This invention is made | formed in view of said problem, Comprising: It aims at providing the chemical injection apparatus which can take the injection amount range of a chemical | medical solution wide. In particular, it is an object of the present invention to provide a chemical injection device for a power plant boiler that can inject a chemical solution almost in proportion to the amount of makeup water even when the makeup water flow rate is small.

The chemical injection device of the present invention is a chemical injection device for injecting a chemical liquid into a main liquid flow path through which the main liquid flows,
A main liquid flow meter that detects a flow rate (main liquid flow rate) of the main liquid flow path and generates a flow signal, and a large flow rate variable flow rate provided in a chemical liquid injection flow path connected to the main liquid flow path A chemical injection pump (large capacity pump), a small discharge amount variable flow chemical injection pump (small capacity pump) provided in a chemical injection path connected to the main liquid flow path, and a main liquid flow meter emits by receiving the flow signal and a control unit providing a discharge flow rate signal to the high-capacity pump and a small-capacity pump, the main fluid flow in a large area dispensed medicines are driving the large capacity pump, the main In the region where the liquid flow rate is small, the small-capacity pump is operated to perform drug injection.

  According to the present invention, when the required injection amount of the chemical solution is relatively large (for example, when the maximum is 100, the required amount is about 20 to 100) with respect to the flow rate detected by the flow meter, the capacity is large. When the pump is operated to inject the chemical liquid and the required injection amount of the chemical liquid is relatively small (for example, about 1 to 20), the small capacity pump is operated to inject the chemical liquid. By using two types of pumps having different capacities as described above, a wide injection volume range capable of highly accurate control of the drug injection volume can be obtained.

In the present invention, the large capacity pump is a plunger pump, if said small capacity pump is a solenoid driven pump, can select appropriate pump in accordance with the magnitude of the injection amount of the liquid medicine.

  In the present invention, it is preferable to have an air vent return flow path that returns to the tank in which the chemical liquid is stored from the middle of the chemical liquid supply path provided with the large capacity and / or small capacity pump.

  In this case, when the large and small pumps are switched, the chemical liquid can be circulated in the return flow path and the chemical liquid supply flow path on the pump side to be activated. As a result, the chemical liquid is discharged and bleed in a state where there is no back pressure (the pressure of the main liquid supply flow path is not applied to the discharge side of the pump of the chemical liquid supply flow path). For this reason, even when the pump is switched, the chemical liquid can be stably injected into the makeup water flow path.

  The present invention further includes a liquid quality measuring device that detects the liquid quality of the mixed liquid of the main liquid and the chemical liquid and emits a signal, and the performance of the pump is determined based on the liquid quality measured by the liquid quality measuring device. It is preferable to check and adjust the operation of the pump.

  In this case, if it is found that the liquid quality of the main liquid measured by the liquid quality measuring device is not controlled to a desired value, an abnormality of the pump can be notified. In addition, if the large capacity pump, which seems to have a relatively long operation time, deteriorates and the amount of chemicals to be injected is found to be insufficient, the small capacity pump is also temporarily operated simultaneously. It can control so that the chemical | medical solution of a minute can be inject | poured.

  In the present invention, it is more preferable that the main liquid is make-up water for a power plant boiler, and the chemical liquid is a chemical liquid for controlling the quality of the make-up water.

  In power plant boilers, there is a large difference in operating conditions (power generation) between daytime and nighttime, and the fluctuation in the amount of makeup water is correspondingly large. In the medium and high pressure boilers that have been used in the past, it was not possible to inject an amount of chemical solution suitable for a small makeup water ratio (ratio of the makeup water flow rate to the feed water flow rate). However, in the present invention, when the makeup water ratio is small, Since it operates a small capacity pump, it can always inject an appropriate amount of chemical solution. For this reason, since an amount of the chemical solution substantially proportional to the makeup water ratio can be injected, the concentration of the chemical solution in the makeup water can be kept substantially constant. Even if the makeup water ratio exceeds 100% for some reason, in the present invention, both the large flow pump and the small flow pump can be operated.

  As is clear from the above description, according to the present invention, since the large-capacity pump and the small-capacity pump are selected and used according to the injection amount of the chemical solution, the range of the injection amount can be widened. In particular, in the water supply system of the power plant boiler, the chemical liquid can be injected in proportion to the makeup water ratio, and the quality of the water supply can be kept almost constant. As a result, the corrosion of iron and the adhesion of iron scale to the boiler are suppressed, leading to energy saving and global warming suppression.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a chemical liquid injector according to an embodiment of the present invention.
The chemical injection device 10 of this example is provided in a flow path for supplying water from a supply water source 55 to a water supply tank 51 in which boiler supply water is stored in a boiler circulation system 50.

First, the boiler circulation system 50 will be described.
Although not shown in the drawing, a pump is provided in the water supply passage connecting the water supply tank 51 to the boiler 52, and water is supplied from the tank 51 to the boiler 52. The water supply channel is also provided with an economizer (not shown). Steam generated from the boiler 52 stays in a steam reservoir (not shown) through a steam pipe and is introduced into a steam turbine (not shown). The steam discharged from the steam turbine passes through the condensate passage and is returned to water by a condenser (not shown) provided in the passage, and the condensate is returned to the water supply tank 51 again. A drain port 52a is provided on the wall surface of the boiler 52, and the water in the boiler is drained when necessary.

  A makeup water channel 56 from a makeup water source 55 is connected to the feed water tank 51, and a pump 57 is provided in the channel 56. When the water level in the water supply tank 51 falls below a predetermined level, the makeup water is pumped up from the makeup water source 55 by the pump 57 and sent to the water supply tank 51, and the water supply tank 51 is always managed to be at a predetermined water level.

The chemical solution injection device 10 of the present invention is provided in the replenishing water channel 56, and adjusts the pH of the water to be replenished by injecting a pH adjusting agent such as amine into the replenishing water.
A flow meter 11 is provided between the pump 57 and the water supply tank 51 in the makeup water flow path 56. The flow meter 11 measures the makeup water flow rate in the makeup water flow path 56. Two chemical solution injection channels 21 and 31 extending from the chemical solution tank 13 are connected to the makeup water channel 56 upstream of the flow meter 11. One chemical solution injection channel 21 is provided with a large capacity pump 22, and the other chemical solution injection channel 31 is provided with a small capacity pump 32. Note that the large-capacity pump 22 and the small-flow pump 32 may be provided in any chemical solution injection channel.

  The large flow rate pump 22 is a variable flow rate pump having a relatively large discharge amount. For example, a plunger pump (for example, a plunger pump) that moves the plunger in and out of the cylinder by the AC motor 23 and opens and closes the valve to transfer the liquid. Pump WS series (trade name) manufactured by Shinyo Co., Ltd. can be used. In this type of pump, by changing the frequency of the voltage applied to the AC motor by an inverter, the pump rotation speed (plunger reciprocation) is changed to vary the flow rate. The small flow rate pump 32 is a flow rate variable pump with a relatively small discharge amount, for example, an electromagnetically driven pump (for example, Cliffider BX (registered trademark)) that moves the diaphragm with a plunger using the driving force of the solenoid 33. , Manufactured by Kurita Kogyo Co., Ltd.). In this type of pump, the flow rate is varied by changing the number of reciprocating movements of the plunger by changing the pulse width of the voltage supplied to the solenoid.

  Check valves (check valves) 24 and 34 are provided downstream of the pumps 22 and 32 in the chemical liquid injection channels 21 and 31 to prevent replenishment water from flowing back into the chemical solution supply channels 21 and 31. is doing.

  The flow meter 11 is electrically connected to the control unit 12, and a flow signal detected by the flow meter 11 is input to the control unit 12. The motor 23 of the large-capacity pump 22 and the solenoid 33 of the small-capacity pump 32 are also electrically connected to the control unit 12, and the control unit 12 responds to the flow rate signal with the large discharge pump 22 and the small discharge amount. The pump 32 is controlled.

  For example, when the required injection amount of the chemical solution with respect to the flow rate detected by the flow meter 11 is 100 at the maximum, when the required amount is about 20 to 100, a signal is sent from the control unit 12 to the motor 23 and the large capacity pump 22 is operated, and the chemical solution is injected from the chemical solution tank 13 through the injection flow channel 21 into the replenishment water flow channel 56. On the other hand, when the required amount is about 1 to 20, a signal is sent from the control unit 12 to the solenoid 33 to operate the small-capacity pump 32 and from the chemical liquid tank 13 through the injection channel 31 to the makeup water channel 56. Inject chemicals.

FIG. 2 is a graph schematically showing the relationship between the chemical injection amount with respect to the water supply flow rate and the chemical concentration (chemical injection concentration) in the water supply. In each graph, the horizontal axis represents the feed water flow rate, and the vertical axis represents the chemical injection amount (left side) and the chemical injection concentration (right side).
In the medicinal injection device 10, the injection amount of the chemical liquid can be controlled substantially in proportion to the feed water flow rate as shown in FIG. For this reason, the density | concentration of the chemical | medical solution in water supply can be kept substantially constant.

  On the other hand, when a conventional plunger-type metering pump is used, as shown in FIG. 2B, even when the feed water flow rate is small, the injection amount of the chemical solution cannot be lowered to a certain level or more. For this reason, in the area | region where a feed water flow rate is low, the density | concentration of the chemical | medical solution in feed water will become high.

FIG. 3 is a diagram for explaining the configuration of the chemical injection device according to the second embodiment of the present invention.
The medicinal injection device 10 'in this example has substantially the same configuration as that of the medicinal injection device 10 of FIG. ) To the chemical liquid tank 13 are provided. Electromagnetic valves 26 and 36 are provided in the flow paths 25 and 35. These electromagnetic valves 26 and 36 are electrically connected to the control unit 12, and the control unit 12 controls the opening and closing of the electromagnetic valves 26 and 36.

  In this example, when the large and small pumps 22 and 32 are switched and one of the pumps is started, the control valve 12 opens the electromagnetic valve in the return flow path on the pump side and simultaneously operates the pump for a predetermined time. Control. Then, for example, when switching to the large-capacity pump 22, the chemical solution circulates through the chemical solution tank 13, the chemical solution injection channel 21, and the return channel tube 25. As a result, the pressure of the makeup water flow path 56 is not applied to the discharge side of the pump 22 of the chemical solution injection flow path 21 (there is no back pressure), and the flow path of the discharge path of the chemical solution injection flow path 21 on the discharge side of the pump 22 is vented. The After operating the pump 22 for a predetermined time, the electromagnetic valve 26 is closed, and the chemical solution is sent from the tank 13 through the chemical solution injection channel 21 to the makeup water channel 56.

FIG. 4 is a diagram for explaining the configuration of a chemical injection device according to the third embodiment of the present invention.
The medicinal injection device 10 ″ in this example has substantially the same configuration as that of the medicinal injection device of FIG. 41 is attached. The liquid quality measuring instrument 41 measures, for example, the pH of the makeup water in the flow path 56 and the electrical conductivity. The measuring instrument 41 is electrically connected to the control unit 12, and a measurement signal is sent to the control unit 12.

  In the medicinal injection device 10 ″, the liquid quality measuring device 41 measures the liquid quality of the replenishing water, so that it can be determined whether or not the chemical liquid has been properly injected. If the liquid quality is not controlled to a desired value in spite of being controlled as described above, there may be a problem that the pumps 22 and 32 are defective. In this case, measures such as repair or replacement of the pump can be taken by notifying the pump abnormality.

  In this apparatus, as described above, the large-capacity pump 22 is driven when the required amount is about 20 to 100. That is, it is estimated that the time for which the large capacity pump 22 is driven is longer than the time for which the small capacity pump 32 is driven. Therefore, in this example, the quality of the makeup water does not meet the predetermined standard from the measurement result of the quality of the makeup water (pH and electrical conductivity), and the control as described above is performed. Nevertheless, if it is found that the quality of the makeup water is not controlled as desired, the cause is considered to be a malfunction due to deterioration of the large capacity pump 22 over time. Therefore, if the quality of the makeup water does not satisfy the predetermined standard during the operation of the large-capacity pump 22 and the chemical injection amount is insufficient, the small-capacity pump 32 can also be activated to inject the chemical solution by the shortage. Like that.

It is a figure which shows the structure of the chemical injection device which concerns on embodiment of this invention. It is a graph which shows typically the relation between the amount of chemical injection with respect to the flow rate of water supply, and the chemical concentration (chemical injection concentration) in the water supply. It is a figure explaining the structure of the chemical injection apparatus which concerns on the 2nd Embodiment of this invention. It is a figure explaining the structure of the chemical injection apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Chemical liquid injection apparatus 11 Flowmeter 12 Control part 13 Chemical liquid tank 21 Chemical liquid injection flow path 22 Large capacity pump 23 AC motor 24 Check valve 25 Return flow path 26 Solenoid valve 31 Chemical liquid injection flow path 32 Small capacity pump 33 Solenoid 34 Check Valve 35 Return flow path 36 Solenoid valve 41 Liquid quality measuring device 50 Boiler circulation system 51 Water supply tank 52 Boiler 52a Drain outlet 55 Supply water source 56 Supply water flow path 57 Pump

Claims (5)

A chemical injection device for injecting a chemical into a main liquid flow path through which a main liquid flows,
A main liquid flow meter for detecting a flow rate of the main liquid flow path (main liquid flow rate) and generating a flow signal;
A large flow rate variable volume chemical injection pump (large capacity pump) provided in a chemical liquid injection flow channel connected to the main liquid flow channel;
A small discharge amount variable flow rate chemical injection pump (small capacity pump) provided in a chemical liquid injection flow channel connected to the main liquid flow channel;
A control unit for receiving a flow rate signal from the main liquid flow meter and giving a discharge flow rate signal to the large capacity pump and the small capacity pump;
With
In the region where the flow rate of the main liquid is large, the large-capacity pump is operated to inject medicine,
In a region where the flow rate of the main liquid is small, the small volume pump is operated to perform chemical injection. The large capacity pump is a plunger pump,
The dosing device according to claim 1, wherein the small capacity pump is a solenoid driven pump.   3. A return flow path for air venting that returns to a tank in which the chemical liquid is stored from the middle of the chemical liquid supply flow path provided with the large capacity and / or small capacity pump. Chemical injection device.   It further comprises a liquid quality measuring device that detects the liquid quality of the mixed liquid of the main liquid and the chemical liquid and emits a signal, and checks the performance of the pump based on the liquid quality measured by the liquid quality measuring device and the pump The medicine injection device according to any one of claims 1 to 3, wherein operation is adjusted.   The chemical injection device according to any one of claims 1 to 4, wherein the main liquid is makeup water for a power plant boiler, and the chemical liquid is a chemical liquid for controlling the quality of the makeup water.

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