JPH07265867A - Method for measuring and controlling chlorine dioxide concentration in seawater and device therefor - Google Patents

Abstract

PURPOSE:To easily measure the chlorine dioxide concn. and to use the low- pollution chlorine dioxide as the organism toxic chemical in a seawater utilizing system by subjecting the sampled seawater to spectrophotometry and measuring the chlorine dioxide concn. based on the obtained data of the specified wavelength corresponding to chlorine dioxide. CONSTITUTION:A chlorine dioxide generator 20 is provided to an equipment 10 of a power plant, etc., and chlorine dioxide is generated by using the seawater pumped up by a pump P1 and a raw material stored in a tank 21. The generated chlorine dioxide is stored in a tank 22, and the stored aq. chlorine dioxide soln. is introduced into a water channel 13 close to an intake 12 by a pump 2 to exterminate the organism such as flue mussel. At this time, seawater is pumped up by a pump P3, introduced into a spectrophotometer 24 through a pipeline 23 and subjected to spectrophotometry in an analytical part 24c, the chlorine dioxide concn. in the sampled water is measured based on the measured data of the specified wavelength corresponding to the optical characteristic of chlorine dioxide, and the amt. of an aq. chlorine dioxide soln. to be injected is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seawater utilization system that takes in seawater, uses it, and then drains it back to the sea, for example, a system that utilizes seawater as secondary cooling water for a power plant. The present invention relates to a method and an apparatus for measuring and controlling the concentration of chlorine dioxide injected into seawater for killing pests such as mussels in the seawater for cooling.

[0002]

2. Description of the Related Art When seawater is used as secondary cooling water for plants such as power plants, it is not preferable because mussels and the like breed and adhere to the waterways of equipment from the intake of seawater to drainage, which significantly reduces the cooling capacity. . At present, no effective countermeasures have been taken to prevent the adhesion of mussels, and at the very least it is necessary to stop the operation of the equipment and manually remove the adhered shells. But,
Then, the cost required for the removal work is high, and the operation of the equipment must be stopped.

On the other hand, when fresh water is used as secondary cooling water for industrial use, a similar problem of adhesion of mussels and the like arises, but as a countermeasure against this, disinfection / sterilization action of chlorine dioxide with low pollution is performed. It has been used recently. Since chlorine dioxide does not generate harmful substances such as dioxins and trihalomethanes, it has recently been attracting attention as an alternative chemical to chlorine. Although chlorine dioxide is a low-pollution chemical, it is necessary to control the concentration of chlorine dioxide in used wastewater below the standard in order to prevent adverse effects on the environment. for that reason,
Although it is necessary to properly measure the concentration of chlorine dioxide in the used wastewater, it has been conventionally known that the concentration of chlorine dioxide in fresh water is measured by a potentiometric method.

[0004]

However, the conventionally known potentiometric chlorine dioxide concentration measurement technique is applicable to chlorine dioxide concentration measurement in seawater because seawater originally contains sodium. There wasn't. Therefore, even though it is known that chlorine dioxide is suitable for killing organisms such as mussels in seawater because there is currently no effective technique for measuring chlorine dioxide concentration in seawater, Chlorine dioxide could not be used as a biocidal agent in utilization systems.

The present invention has been made in view of the above points, and it is an object of the present invention to make it possible to measure the concentration of chlorine dioxide in seawater. Furthermore,
The aim is to enable the use of low-pollution chlorine dioxide as a biocidal agent in seawater utilization systems. Further, another object of the present invention is to make it possible to control the concentration of chlorine dioxide in the used seawater so as not to adversely affect the environment.

[0006]

The method for measuring the concentration of chlorine dioxide in seawater according to the present invention corresponds to chlorine dioxide in the first step of sampling the seawater to be inspected and spectrophotometrically measuring the sampled seawater. The second to measure the concentration of chlorine dioxide based on the photometric data of a predetermined wavelength
It is characterized by including steps and.

The chlorine dioxide concentration control method in seawater according to the present invention comprises the steps of taking in seawater, injecting chlorine dioxide into the taken seawater, using the seawater containing chlorine dioxide, and The step of draining the seawater, the step of spectrophotometrically measuring the used seawater, and the step of measuring the concentration of chlorine dioxide based on the photometric data of a predetermined wavelength corresponding to chlorine dioxide; If the value exceeds the value, a step of injecting a neutralizing agent into the used seawater to dilute the concentration of chlorine dioxide, and then performing the drainage is provided. is there.

The chlorine dioxide concentration measuring apparatus in seawater according to the present invention includes means for pumping up seawater to be inspected and guiding it to a pipe, and a transparent cell portion provided in the middle of the flow path of the pipe, the transparent cell Spectrophotometrically measuring the concentration of chlorine dioxide in the sample liquid based on the photometric data of a predetermined wavelength corresponding to chlorine dioxide is there.

A chlorine dioxide concentration control device in seawater according to the present invention uses seawater which takes in seawater, injects chlorine dioxide into the taken seawater, uses seawater containing chlorine dioxide, and drains used seawater. In the system, a means for pumping the used seawater and guiding it to a pipe, and a transparent cell part provided in the middle of the flow path of the pipe, spectrophotometrically measuring the seawater sample liquid passing through the transparent cell part, and chlorine dioxide When the spectrophotometric measuring means for measuring the concentration of chlorine dioxide in the sample solution from the photometric data of a predetermined wavelength corresponding to, and the measured concentration of chlorine dioxide exceeds a predetermined reference value,
And a control means for performing a treatment for diluting the concentration of chlorine dioxide in the used seawater.

[0010]

It is known that an aqueous solution of chlorine dioxide has predetermined optical characteristics. Focusing on this point, in the present invention, the seawater sample solution to be inspected is spectrophotometrically measured by a spectrophotometer (that is, a spectrophotometer) to obtain the seawater sample based on photometric data of a predetermined wavelength corresponding to chlorine dioxide. The feature is that the concentration of chlorine dioxide in the liquid is measured. Therefore, since it is possible to measure the concentration of chlorine dioxide in seawater, it becomes possible to use chlorine dioxide, which is a low-pollution agent, as a biological killing agent such as mussels in a seawater utilization system, It is possible to prevent shellfish from adhering to the waterway and solve problems such as time and effort for removing the shellfish that has adhered. Furthermore, it will also be possible to control the concentration of chlorine dioxide in used seawater to a low level that does not adversely affect the environment, which will adversely affect marine life when draining used seawater into the sea. It can be properly controlled not to give.

By the way, when an aqueous solution of chlorine dioxide is stirred and air is mixed, its optical characteristics change (the color level is lowered or the color disappears). Therefore, if the water is appropriately agitated while passing through the water channel of the seawater utilization system, the color of the sample liquid may become light regardless of the concentration of chlorine dioxide. However, chlorine dioxide is likely to be chemically decomposed by being combined with bacteria in seawater and to be eliminated relatively quickly. In this case, the color of the sample liquid becomes lighter as the concentration of chlorine dioxide becomes thinner. As described above, the reason why the color of the sample liquid becomes faint or disappears may be either case, but it is generally considered that the latter is often due to relatively rapid decomposition. However, as in the former case, the color of the sample liquid may become pale despite the concentration of chlorine dioxide, so it is desirable to take thorough measures in consideration of this point.

Therefore, in one embodiment of the present invention, when spectrophotometrically measuring the seawater sample solution, an appropriate amount of acid is injected into the sample solution to set the pH value of the sample solution to a predetermined value. Concentration measurement is performed on a sample liquid set to a predetermined pH value. By setting the pH value to the predetermined value in this way, the optical characteristics (color) of the sample solution are restored to the characteristics corresponding to the actual concentration of chlorine dioxide in the sample solution, so that the measurement accuracy can be maintained. it can. Further, when this oxidation method is applied to a sample liquid into which a neutralizing agent has been injected, it is possible to measure the residual amount of chlorine dioxide before the neutralization treatment, and thereby to prove the usage amount.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 illustrates an overview of a seawater utilization system according to an embodiment of the present invention.
The facility 10 is, for example, a plant such as a power plant, and is a system that uses seawater as secondary cooling water in the facility 10. That is, the seawater in the sea 11 is taken into the main waterway 13 from the water inlet 12, and the main waterway 13 to the watershed 13
It is introduced into the facility 10 via a and used for cooling. The used seawater is returned to the main waterway 13 from the water diversion channel 13a, and is drained to the sea 11 from the drainage port 14 via the water gate 15.

FIG. 2 is a system configuration diagram showing an embodiment of the chlorine dioxide concentration measuring and controlling system according to the present invention. A chlorine dioxide generator 20 is attached to the facility 10 and generates chlorine dioxide using the seawater pumped by the pump P1 and the raw material stored in the raw material tank 21. The generated chlorine dioxide is made into, for example, an aqueous solution of chlorine dioxide diluted to about 0.2% or any other arbitrarily selected concentration, and stored in the tank 22. The chlorine dioxide aqueous solution stored in this tank 22 is introduced into the water channel 13 near the water intake 12 via the pump P2, and the water channel 1
It is injected into seawater in 3, 13a. This chlorine dioxide solution may be injected by any method. For example,
The flow rate, temperature, and other factors are controlled to predetermined values, and a predetermined amount of chlorine dioxide solution is automatically injected for a predetermined time, and this is automatically performed at any time or at predetermined time intervals as needed. You may Thus, the equipment 10
Chlorine dioxide is injected into the cooling seawater introduced inside,
It is possible to kill organisms such as mussels, and equipment 10
It can be prevented from adhering to the inside.

The seawater sample solution to be inspected for concentration measurement is pumped up by a pump P3 from an appropriate location near the drainage port 14 in the water channel 13 and introduced into a spectrophotometer (that is, a spectrophotometer) 24 through a pipe 23. It FIG. 3 is a diagram showing a novel system configuration example of a spectrophotometer 24 capable of spectrophotometrically measuring a seawater sample liquid continuously flowing in the pipe 23. The spectrophotometer 24 is roughly classified into a light source 24a and a light receiving unit. 24b and an analysis processing unit 24c. The pumped-up seawater sample liquid is continuously guided to the installation location of the spectrophotometer 24 through the pipe 23. At a location corresponding to the spectrophotometer 24, the flow path of the pipe 23 is configured by the transparent cell portion 23a, and the light emitted from the light source 24a (for example, a tungsten light bulb) passes through the transparent cell portion 23a and the seawater sample solution. The light receiving unit 24
b (for example, CCD; charge-coupled device) receives light, and an electrical signal corresponding to the amount of light received is output. The output signal of the light receiving section 24b is given to the analysis processing section 24c.

In the analysis processing unit 24c, spectrophotometry is performed based on the received light output signal corresponding to the amount of received light that has passed through the sample liquid, and photometric data of a predetermined wavelength (for example, 358 nm (nanomillimeter)) corresponding to the optical characteristics of chlorine dioxide. Based on the above, processing for measuring the concentration of chlorine dioxide in the sample solution is performed. That is, the spectral wavelength vs. absorption (optical density or absorbance) characteristic of the sample solution containing chlorine dioxide is obtained, the absorption of a predetermined wavelength corresponding to chlorine dioxide is detected from this, and the sample solution is based on the detected absorption. Determine the concentration of chlorine dioxide in the product.

The chlorine dioxide concentration measurement data obtained by the analysis processing section 24c is sent to the controller 25 and used for chlorine dioxide concentration control. The control device 25 includes a CPU (central processing unit) 25a and a display (for example, a CR).
T) 25b, a computer system including a memory device, a printer, etc., not shown, and controls the entire chlorine dioxide concentration measurement and control system according to this embodiment. Based on the chlorine dioxide concentration measurement data, if the concentration exceeds a predetermined reference value (for example, exceeds 0.2 ppm), the control device 25 pumps P
4 is controlled to introduce the neutralizing agent from the neutralizing agent tank 26 into the water channel 13 to dilute the concentration of chlorine dioxide in the seawater to be drained. It is preferable to automatically close the water gate 15 during the injection of the neutralizing agent so that the waste water having a chlorine dioxide concentration exceeding a predetermined reference value does not flow. During the injection of the neutralizing agent, the chlorine dioxide concentration is measured several times as appropriate to properly control the amount of the neutralizing agent to be injected. Also, after the injection of the neutralizing agent, the chlorine dioxide concentration is appropriately measured, and after confirming that the concentration is below a predetermined reference value, the water gate 15 is opened and the water is drained to the sea.
As a modification to dilute the concentration of chlorine dioxide,
The sluice gate 15 may be simply closed and the drainage to the sea may be stopped until the concentration of chlorine dioxide naturally falls below the reference value due to the decomposition action of microorganisms and other natural actions.

By the way, when an aqueous solution of chlorine dioxide is stirred and air is mixed in, its optical characteristics are changed (the color level is lowered or the color disappears). Therefore, if the water is appropriately agitated while passing through the water channel of the seawater utilization system, the color of the sample liquid may become light regardless of the concentration of chlorine dioxide. However, chlorine dioxide is likely to be chemically decomposed by being combined with bacteria in seawater and to be eliminated relatively quickly. In this case, the color of the sample liquid becomes lighter as the concentration of chlorine dioxide becomes thinner. As described above, the reason why the color of the sample liquid becomes faint or disappears may be either case, but it is generally considered that the latter is often due to relatively rapid decomposition. However, as in the former case, the color of the sample liquid may become pale despite the concentration of chlorine dioxide, so it is desirable to take thorough measures in consideration of this point. Therefore, in this example, when spectrophotometrically measuring the seawater sample solution, an appropriate amount of acid was injected into the sample solution to set the pH value of the sample solution to a predetermined value, and the pH value was set to the predetermined pH value. Concentration measurement is performed on the sample liquid. By setting the pH value to the predetermined value in this way, the optical characteristics (color) of the sample solution are restored to the characteristics corresponding to the actual concentration of chlorine dioxide in the sample solution, so that the measurement accuracy can be maintained. it can.

For this purpose, the sample liquid measured by the spectrophotometer 24 is introduced into the processing container 27, and the pump P5 is used.
Is appropriately driven to introduce an appropriate amount of acid from the tank 28 into the processing container 27 to oxidize the sample liquid. At this time, the pH of the solution in the processing container 27 is adjusted by the pH meter 29.
The H degree is measured, and the oxidation treatment is performed until a predetermined pH value is reached. For example, it is conceivable to perform the oxidation treatment until the pH reaches about 2, but the pH value is not limited to this. The sample liquid after the oxidation treatment is again subjected to spectrophotometry with the spectrophotometer 30 to measure the concentration of chlorine dioxide in the sample liquid. As a result, the actual concentration of chlorine dioxide in the sample liquid can be accurately measured. The measured sample liquid is returned to the water channel 13 through the pipe 23.

The above-mentioned oxidation treatment can be applied to the neutralized sample liquid. In that case,
It is possible to measure the residual amount of chlorine dioxide before the neutralization process, and the difference between the amount of chlorine dioxide initially injected and the above residual amount can be used to prove the amount of chlorine dioxide used in this system. can do.

FIG. 4 is a graph showing an example of measurement according to the present invention. Example 1 shows a result of spectrophotometry when a chlorine dioxide solution having a concentration of 1652 ppm was diluted to one-fifth with seawater. Is. In the case of Example 1, the absorption at a wavelength of 358 nm is about 0.121, which is the concentration of the chlorine dioxide seawater solution as the sample, 1652 ppm × 1/500.
It corresponds to ≈3.304 ppm. Example 2 shows the spectrophotometric result of measuring the chlorine dioxide concentration after heating the chlorine dioxide seawater solution of Example 1 at a temperature of 40 ° C. for about 7 minutes. In the case of Example 2, the absorption for the wavelength of 358 nm is about 0.008, and when converted to the chlorine dioxide concentration in the ratio with Example 1, 3.304 ppm × 0.008 / 0.121≈0.2
It is 184 ppm. Example 3 shows the results of spectrophotometry in which the chlorine dioxide concentration in the chlorine dioxide seawater solution of Example 2 was measured by adding an appropriate amount of acid and returning the pH value to pH 2. In the case of Example 3, the absorption for the wavelength of 358 nm is about 0.052, and when converted to the chlorine dioxide concentration in the ratio with Example 1, it is 3.304 ppm × 0.052 / 0.121.
≈1.420 ppm. This is about 43 of the original concentration
It shows that the concentration has returned to%.

Absorbance can be measured on the order of 0.001 and therefore the chlorine dioxide concentration is 0.1
It can be measured with a resolution of ppm to 0.2 ppm. Further, by adopting the oxidation method as described above,
The concentration of chlorine dioxide can be returned so that it can be measured by spectrophotometry, and the measurement accuracy can be improved.

In the above embodiment, the chlorine dioxide concentration and the spectrophotometer 2 at the first stage near the water intake 12 were measured.
The chlorine dioxide concentration at each stage measured in 4 and 30 may be appropriately recorded by the control device 25, and the time-dependent change of chlorine dioxide concentration at each stage may be displayed by the display 25b or a printer. Further, in the above-described embodiment, the function of the analysis processing unit 24c in the spectrophotometers 24, 30 may be assigned to the CPU 25a of the control device 25. In addition, in the above-described embodiment, the spectrophotometer 24 has a novel structure such that the sample liquid to be inspected can be continuously guided to the spectrophotometer 24 through the pipe 23. Not limited to this, it is possible to use a conventionally known spectrophotometer as it is. In that case, the sample solution is pumped into an appropriate container and brought to the spectrophotometer for concentration measurement, but since continuous measurement cannot be performed as in the above-mentioned embodiment, concentration measurement and control are automated. Is difficult. However, if the configuration is such that continuous measurement is possible as in the above embodiment, automation is easy.

[0024]

As described above, according to the present invention, it becomes possible to easily measure the concentration of chlorine dioxide in seawater, which enables the use of low-pollution chlorine dioxide as a biocidal agent in a seawater utilization system. As well as being able to be used, it becomes possible to control the concentration of chlorine dioxide in the used seawater to such an extent that it does not adversely affect the environment.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an overview of a seawater utilization system according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram showing an embodiment of a chlorine dioxide concentration measurement and control system according to the present invention.

FIG. 3 is a diagram showing a system configuration example of the spectrophotometer in FIG.

FIG. 4 is a graph showing a measurement example according to the present invention.

[Explanation of symbols]

 10 Facilities 11 Sea 12 Intake 13 Main canal 13a Water diversion 14 Drain 15 Sluice 20 Chlorine dioxide generator 23 Piping 24, 30 Spectrophotometer 24a Light source 24b Light receiving part 24c Analytical processing part 25 Control device 26 Neutralizer tank 27 Oxidation Processing container for processing

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location A01N 59/00 A C02F 1/00 ZAB U G01J 3/42

Claims (11)

[Claims] 1. A first step of sampling seawater to be inspected, and a second step of spectrophotometrically measuring the sampled seawater and measuring the concentration of chlorine dioxide based on photometric data of a predetermined wavelength corresponding to chlorine dioxide. A method for measuring the concentration of chlorine dioxide in seawater, which comprises a step. 2. In the first step, seawater to be inspected is pumped through a pipe and continuously guided to the spectrophotometer through the pipe, and the pipe of the pipe is connected to the spectrophotometer at a position corresponding to the spectrophotometer. The flow path is constituted by a transparent cell section, and in the second step, the seawater sample continuously guided to the transparent cell section can be continuously measured by the spectrophotometer. The measuring method according to claim 1. 3. The method further comprising the step of injecting an appropriate amount of acid into the sampled seawater to set the pH value of the sample solution to a predetermined value, and the second step for the sample solution set to the predetermined pH value. The measuring method according to claim 1 or 2, wherein concentration measurement is performed by steps. 4. A step of taking in seawater, a step of injecting chlorine dioxide into the taken seawater, a step of using the seawater containing chlorine dioxide, a step of draining the used seawater, and a step of draining the used seawater. The step of spectrophotometrically measuring seawater and measuring the concentration of chlorine dioxide based on the photometric data of a predetermined wavelength corresponding to chlorine dioxide, and if the measured concentration of chlorine dioxide exceeds a predetermined standard value, the used seawater A method for controlling the chlorine dioxide concentration in seawater, comprising the steps of injecting a neutralizing agent to dilute the concentration of chlorine dioxide, and then performing the drainage. 5. The method further comprising the step of injecting an appropriate amount of an acid into a used seawater sample liquid to be photometrically measured during the spectrophotometry to set the pH value of the sample liquid to a predetermined value. The control method according to claim 4, wherein concentration measurement by the spectrophotometry is performed on the set sample liquid. 6. A means for pumping seawater to be inspected and guiding it to a pipe, and a transparent cell portion provided in the middle of the flow path of the pipe,
Spectrophotometric means for spectrophotometrically measuring the seawater sample liquid passing through the transparent cell portion and measuring the concentration of chlorine dioxide in the sample liquid based on photometric data of a predetermined wavelength corresponding to chlorine dioxide. Measuring equipment for chlorine dioxide concentration in seawater. 7. A seawater utilization system in which seawater is taken in, chlorine dioxide is injected into the taken seawater, seawater containing chlorine dioxide is used, and used seawater is drained, and the used seawater is pumped up and piped. And a transparent cell portion provided in the middle of the flow path of the pipe,
A spectrophotometric means for spectrophotometrically measuring the seawater sample liquid passing through the transparent cell portion and measuring the concentration of chlorine dioxide in the sample liquid based on photometric data of a predetermined wavelength corresponding to chlorine dioxide, and the measured concentration of chlorine dioxide Is above a predetermined reference value, the chlorine dioxide concentration control device is provided with a control means for performing a treatment for diluting the concentration of chlorine dioxide in the used seawater. 8. The apparatus according to claim 7, wherein the control unit dilutes the concentration of chlorine dioxide by injecting a neutralizing agent into the used seawater. 9. The apparatus according to claim 7, wherein the control means closes the drainage gate until the concentration of chlorine dioxide becomes low. 10. A means for injecting an appropriate amount of acid into the seawater sample liquid guided to the transparent cell portion to set a pH value of the sample liquid to a predetermined value, the sample liquid having a predetermined pH value. 8. The apparatus according to claim 6, wherein the density measurement can be performed by the spectrophotometry. 11. The seawater is used as cooling water for a plant, and the chlorine dioxide is injected to kill organisms in the cooling seawater. The method or apparatus according to.