JP3597978B2 - Sample dilution analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a sample dilution analyzer for diluting and analyzing sample water obtained by collecting steam / condensate / supply water from a plant such as a thermal power plant.
[0002]
[Prior art]
In a power plant of a thermal power plant, for example, pipes are corroded by oxygen dissolved in steam, condensate water, or water in a water supply system.In order to prevent this, hydrazine that reduces the dissolved oxygen is injected. ing.
[0003]
The concentration of this hydrazine in the sample water (residual hydrazine concentration) is set to a reference value such that the reducing action is necessary and sufficient, and in a normal operation state (between the start-up step and the normal operation), The residual hydrazine concentration is measured by a hydrazine meter, the hydrazine supply amount is adjusted by feedback control, and control is performed so that the residual hydrazine concentration becomes a reference value. Alternatively, the amount of hydrazine corresponding to the flow rate of the system water is calculated in advance, the replenishment amount is controlled in proportion to the flow rate of the system water, and the hydrazine meter monitors the residual hydrazine concentration so as to be a reference value.
[0004]
However, during the period from the time of shutdown to the time of next start-up, such as when starting up after shutting down the power plant and opening the system water piping to the atmosphere, or when starting up after completion of the plant, a large amount of Since air (oxygen) is mixed, the amount of hydrazine to be injected needs to be larger than that in the normal operation. At that time, the concentration of the residual hydrazine to be controlled becomes a maximum, for example, about 100 ppm.
[0005]
However, the measurement range of a commercially available hydrazine meter is 0 to 10 ppm, and the measurement of the high concentration as described above was impossible. For this reason, at present, the residual hydrazine concentration is measured by hand analysis, and replenishment based on the measurement result is manually performed. In addition, even if automation is performed to some extent, it is not necessary to control the appropriate amount only by injecting a predetermined amount in accordance with the operation of the plant. Was forced to uselessly resupply.
[0006]
Therefore, in order to solve such a problem, even if the residual hydrazine has a high concentration, it is possible to measure with a conventional commercially available hydrazine meter, and based on this, it is possible to control the automatic supply of an appropriate amount of hydrazine. Japanese Utility Model Laid-Open Publication No. 6-86056, entitled "Pure Water Dilution Sampling Apparatus" filed by the present applicant. In this apparatus, a desired analysis is performed after diluting a sample water collected from system water with pure water, and the analysis result is corrected by a dilution factor to obtain a true analysis measurement value.
[0007]
[Problems to be solved by the invention]
However, in this apparatus, although the amounts of sample water and pure water are measured by a flow meter, when there is a flow rate fluctuation, the analysis value correction processing performed by a dilution factor based on the flow rate value at the time of the fluctuation is performed. There is a problem that the timing is delayed and an error is included in the analysis correction value.
[0008]
In addition, in order to reduce such a delay in timing, it is necessary to shorten the pipe length from the flow meter to the analyzer as much as possible. However, the shorter the pipe length, the lower the stirring effect of the sample water and pure water. Therefore, there is still a problem that the accuracy of the analysis correction value is deteriorated.
[0009]
The present invention has been made in view of such a point, and an object of the present invention is to improve the analysis correction accuracy by preventing a flow rate variation between sample water and pure water, and to solve the above-described problem. is there.
[0010]
[Means for Solving the Problems]
In order to achieve this object, a first aspect of the present invention is to connect a pure water introduction pipe for taking in pure water for dilution to a sample water introduction pipe for taking in sample water, and to dilute the sample water with the pure water. In a sample dilution analyzer that performs various measurements on water in the measurement section and corrects the measurement results with the dilution ratio of the sample water, a head vessel that sets a predetermined water head pressure is provided, and the head vessel is disposed at a subsequent stage. Each equipped with a metering pump for discharging a constant flow of liquid,
These two metering pumps are configured such that the flow rate can be adjusted by setting the stroke length and driven by a common motor.
[0011]
According to a second aspect, in the first aspect, the metering pump includes a drive unit for setting a stroke length, and a sensor for detecting the set stroke length. The setting signal is taken in by the flow control device, the drive unit is controlled so as to have a stroke length corresponding to the setting signal, and the actual stroke length at that time is detected by a sensor.
[0012]
According to a third invention, in the first or second invention, a stirring means for stirring the dilution water is provided at a stage preceding the measurement section , and a head vessel is provided, and the dilution water stirred by the stirring means is supplied to the head vessel. The measurement was performed by the measuring unit after the head pressure was kept constant.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a system diagram of a sample dilution analyzer according to an embodiment of the present invention, which is applied to measurement of a residual hydrazine concentration in system water of a thermal power plant. A is a sample water introduction pipe which takes in sampled water which is collected from system water such as a steam pipe, a water supply pipe, or a condensate pipe of a power generation plant, and receives a sample water whose temperature has been reduced and decompressed. A head vessel 2, a defoamer 3, and the like are provided. Here, the sample water taken in by the solenoid valve 1 is set to a predetermined head pressure by the head vessel 2 and the inside of the air is removed by the defoamer 3. When the float switch 2a of the head vessel 2 operates, it outputs a detection signal indicating that the supply amount of the sample water is equal to or less than a predetermined value (for example, the supply is cut off). This detection signal is used for alarms and the like.
[0014]
B is a pure water introduction pipe for taking in pure water for dilution from a tank (not shown), and an electromagnetic valve 4, a head vessel 5 with a float switch 5a, a defoamer 6, etc. are provided at the first stage. ing. Here, the pure water taken in by the solenoid valve 4 is set to a predetermined head pressure (it is not necessary to be the same as the sample water) by the head vessel 5, and the internal air is vented by the defoamer 6. Done. When the float switch 5a of the head vessel 5 operates, the float switch 5a outputs a detection signal indicating that the supply amount of pure water is equal to or less than a predetermined value (for example, the supply is cut off). This detection signal is also used for alarms and the like.
[0015]
Reference numerals 7 and 8 denote plunger-type metering pumps attached to the sample water introduction pipe A and the pure water introduction pipe B, respectively. The pumps are driven by a common motor 9. The fixed-quantity pump 8 on the pure water side has a flow rate of 3.6 to 36 cc / min, for example, 30 to 300 cc / min. The fine flow rate adjustment is performed by adjusting the stroke length.
[0016]
Reference numeral 10 denotes a back pressure valve for applying a predetermined back pressure to the discharge side of the sample water pump 7, and reference numeral 11 denotes a relief valve for preventing the pressure on the discharge side of the pump 7 from exceeding a predetermined value. Reference numeral 12 denotes a back pressure valve for applying a predetermined back pressure to the discharge side of the pure water pump 8, and reference numeral 13 denotes a relief valve for preventing the pressure on the discharge side of the pump 8 from exceeding a predetermined value.
[0017]
14 to 17 are manual valves, and 18 and 19 are flow meters. One flow meter 18 measures and displays the flow rate of sample water, and the other flow meter 19 measures and displays the flow rate of pure water.
[0018]
C is a dilution water pipe for connecting the sample water introduction pipe A and the pure water introduction pipe B to mix the sample water and the pure water, in which a line mixer 20 is provided. The line mixer 20 agitates diluting water, which is a mixture of sample water and pure water, discharged from the flow meters 18 and 19 by passing the diluting water through a spiral passage formed therein, thereby diluting the diluted water. This is for uniformizing the concentration distribution of the substance to be measured such as residual hydrazine in water.
[0019]
21 is a head vessel, and 22 is a hydrazine meter. The dilution water discharged from the line mixer 20 is affected by the pulsating flow at the time of discharge of the metering pumps 7 and 8, and is supplied to the hydrazine meter 22 while being set to a predetermined stable head pressure by the head vessel 21. Then, the concentration of the residual hydrazine is measured. 23 and 24 are manual valves.
[0020]
Now, in this embodiment, the sample water and the pure water are each separated by a predetermined head pressure and air is evacuated, then sucked by the metering pumps 7 and 8 and set to a predetermined flow rate there, and then mixed and diluted. The mixture is further stirred by the line mixer 20, and the residual hydrazine concentration is measured by the hydrazine meter 22.
[0021]
If the flow rate of the sample water discharged from the metering pump 7 is f1 and the flow rate of the pure water discharged from the metering pump 8 is f2, the sample water is
1 / K = f1 / (f1 + f2) (1)
And the dilution ratio becomes K times. If the hydrazine concentration measured by the hydrazine meter 22 at this time is d, the true concentration D is
D = Kd (2)
Can be obtained by
[0022]
FIG. 2 is a diagram showing the configuration of the hydrazine concentration measurement system. The metering pumps 7, 8 are provided with drive units 7a, 8a using a servomotor as an actuator for setting the stroke length (flow rate), and a sensor (not shown) for detecting the set stroke length. I have.
[0023]
25 is a sample water flow control device, 26 is a pure water flow control device, 27 is a sample water flow setting device, and 28 is a pure water flow setting device. When the stroke length of the metering pump 7 is set by the sample water flow rate setting device 27, the sample water flow rate control device 25 takes in the setting signal S1 and sets the drive unit 7a to have a stroke length corresponding to the setting signal S1. Then, the actual stroke length signal at that time is detected by the sensor and fed back as the flow rate f1, and the target value control is performed. The flow rate f1 at this time is sent back to the sample water flow rate setting device 27 and displayed.
[0024]
Further, when the stroke length of the metering pump 8 is set by the pure water flow setting device 28, the pure water flow control device 26 takes in the setting signal S2 and sets the drive unit so that the stroke length corresponds to the setting signal S2. 8a, and the signal of the actual stroke length at that time is detected by the sensor and fed back as the flow rate f2, and the target value control is performed. The flow rate f2 at this time is sent back to the pure water flow rate setting device 27 and displayed.
[0025]
Numeral 29 denotes an arithmetic unit which takes in the flow rates f1 and f2 and the measured value d of the hydrazine concentration and calculates the above-mentioned equations (1) and (2) to calculate the dilution ratio K and the true hydrazine concentration value D. calculate. The dilution ratio K is displayed on the dilution ratio display 30, the true hydrazine concentration D is displayed on the hydrazine concentration display 31, and is input to the hydrazine supply control device 32 as a control signal.
[0026]
As described above, even if the hydrazine concentration in the sample water taken in by the sample water introduction pipe A is higher than the measurement range of the hydrazine meter 22, the dilution ratio K with pure water should be set to a predetermined value. Accordingly, the measurement can be performed after dilution so as to fall within the measurement range of the hydrazine meter 22, and automation of hydrazine replenishment control can be realized.
[0027]
In addition, in the present embodiment, since the sample water or pure water is converted into a predetermined head pressure by the head vessels 2, 5, even if the flow rate of intake of the sample water or pure water fluctuates slightly, it is absorbed. be able to. At this time, excess sample water and pure water are drained to the drain. Further, since the metering pumps 7, 8 are interposed at the subsequent stage of the head vessels 2, 5, fluctuations in the intake flow rate of the sample water or pure water can be almost completely absorbed.
[0028]
Moreover, the metering pump 7, 8 can be set arbitrarily in a fairly wide range flow out come its ejection, it is possible to arbitrarily set the dilution ratio of the sample water. In this case, for example, the valve 14 may be closed and the valve 15 may be opened, and the hydrazine concentration of the sample water may be measured in advance by manual analysis before setting the dilution ratio. In this way, when the measurement sensitivity of the hydrazine meter 22 varies depending on the concentration range, the dilution concentration can be set to fall within the highest sensitivity measurement concentration range.
[0029]
When the concentration deviates from the high-sensitivity measurement concentration range to the high concentration side, the discharge flow rate of the metering pump 8 is increased according to the measurement result to increase the dilution ratio. If feedback is applied to the metering pump 8 so that the flow rate is reduced and the dilution ratio is reduced, the measured concentration can be automatically controlled so as to fall within the highly sensitive measurement concentration range of the hydrazine meter 22.
[0030]
Further, in the present embodiment, the sample water and the dilution water of pure water are stirred by the line mixer 20 and the head pressure is made constant by the head vessel 21 before flowing into the hydrazine meter 22. When the concentration distribution of hydrazine dilution water flowing through is uniform both because it is stabilized, the measurement accuracy of the hydrazine concentration increases.
[0031]
The valves 16 and 17 are for extracting pure water and can be used for pure water inspection and the like. The valves 23 and 24 are for extracting dilution water, and can be used for analysis of other than hydrazine concentration, such as total iron concentration, turbidity, and other dilution analysis.
[0032]
In the sample water dilution analyzer described above, when the system of the pure water introduction pipe B is not used, that is, when the sample is not diluted, the flow rate set value of the metering pump 8 may be set to 0, At this time, the electromagnetic valve 4, the valve 16, and the like are closed as necessary. This makes it possible to directly measure the residual hydrazine concentration in the normal concentration range.
[0033]
Further, in the above description, the flow rate f1 of the sample water is obtained by the feedback signal of the stroke length of the metering pump 7 and the flow rate f2 of the pure water is obtained by the feedback signal of the stroke length of the metering pump 8, respectively. , 19 can be similarly processed.
[0034]
【The invention's effect】
As described above, according to the first invention, since the sample water or pure water is converted into a predetermined head pressure by the head vessel , even if the flow rate of intake of the sample water or pure water fluctuates slightly, it can be absorbed. Further, since a metering pump having a common motor is interposed at the subsequent stage of the head vessel, fluctuations in the intake flow rate of the sample water or pure water can be reliably absorbed. Therefore, there is an advantage that the flow rates of the sample water and the pure water can be stabilized, and thereby a measurement error based on a time delay due to the flow rate fluctuation can be prevented. In addition, since the metering pump can arbitrarily set the discharge flow rate, the dilution ratio of the sample water can be arbitrarily set.
According to a second aspect, in the first aspect, the metering pump includes a drive unit for setting a stroke length, and a sensor for detecting the set stroke length, and the stroke length is set by a flow setting device. When the setting signal is received by the flow control device, the drive unit is controlled to have a stroke length corresponding to the setting signal, and the actual stroke length at that time is configured to be detected by the sensor. Can be fed back as a flow rate, thereby performing target value control.
Further, according to the third aspect, the sample water and the diluted water of pure water are stirred by the stirring means, and the head pressure is made constant by the head vessel before flowing into the measuring section. Since the concentration distribution is made uniform and stabilized, the measurement accuracy is increased.
[Brief description of the drawings]
FIG. 1 is a system diagram of a sample dilution analyzer according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a measurement system according to the embodiment.
[Explanation of symbols]
A: sample water introduction pipe, B: pure water introduction pipe, C: dilution water pipe,
1: solenoid valve, 2: head vessel, 2a: float switch, 3: defoamer, 4: solenoid valve, 5: head vessel, 5a: float switch, 6: defoamer, 7, 8: metering pump, 7a , 8a: actuator, 9: motor, 10: back pressure valve, 11: relief valve, 12: back pressure valve, 13: relief valve, 14 to 17: manual valve, 18, 19: flow meter, 20: line mixer, 21: Head vessel, 22: hydrazine meter, 23, 24: manual valve, 25: sample water flow control device, 26: pure water flow control device, 27: sample water flow setting device, 28: pure water flow setting device, 29: calculation Apparatus, 30: dilution magnification display, 31: hydrazine concentration display, 32: hydrazine supply control device.

Claims (3)

A pure water introduction pipe that takes in pure water for dilution is connected to a sample water introduction pipe that takes in sample water, and various measurements are performed in a measuring section on the dilution water obtained by diluting the sample water with the pure water, and the measurement results are described above. In the sample dilution analyzer that was corrected by the dilution ratio of the sample water,
The sample water introduction pipe and the pure water introduction pipe are each provided with a head vessel set at a predetermined head pressure, and each of the metering pumps for discharging a constant flow rate of liquid is provided at a stage subsequent to the head vessel.
These two metering pumps can adjust the flow rate by setting the stroke length, and are configured to be driven by a common motor,
A sample dilution analyzer, wherein the sample water and pure water set at a predetermined flow rate are mixed and diluted by the two metering pumps, and the diluted water is measured by a measuring unit. The metering pump includes a drive unit for setting a stroke length, and a sensor for detecting the set stroke length, and when the stroke length is set by the flow setting device, the flow control device captures the setting signal and sets the setting signal. The sample dilution analyzer according to claim 1, wherein the drive unit is controlled so as to have a stroke length corresponding to the signal, and an actual stroke length at that time is detected by a sensor . In front of the measuring unit, Rutotomoni provided stirring means for stirring the dilution water, the head vessel provided to measure the water head pressure of the dilution water and stirred by the stirring means in the head vessel by the measurement unit from the constant sample dilution analysis apparatus according to the to claim 1 or 2, characterized in the.

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