JPH10148612A - Sensor head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform measurement continuously by directly dipping a sensor head into a solution such as a waste fluid treating facility, by forming a light projection housing and a light reception housing into a watertight structure, and retaining them at a set height position in a solution with a specified interval. SOLUTION: The sensor head part 31 of a Cr concentration has light projection and reception housing 32 and 33, is fixed on nearly horizontal base plate 34 with an interval, and a measurement is made while the sensor head part 3 is directly dipped into a solution. A through hole 33d, a horizontal hole 42a, and a vertical hole 42b are formed at a light reception part block 42 that is fixed to the light reception housing 33. A half mirror 43 is provided at the cross position on the horizontal hole 42a and the vertical hole 42b and light reception elements 44 and 45 are provided at an open edge. Then, light that enters the light reception housing 33 from the side of the light projection housing 32 is divided by the half mirror 43, enters the light reception elements 44 and 45 through an infrared ray cut filter 46 or a visible light cut filter 47, a signal according to the intensity of a incidence light is outputted, and a Cr concentration is calculated based on the signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sensor head.

[0002]

2. Description of the Related Art Chrome plating is frequently used in the steel, automobile, and electronics industries. Since hexavalent chromium in the waste liquid discharged from these plating plants is harmful to humans, its concentration when discharged into public waters has an environmental standard value of 0.05 according to the Water Pollution Control Law.
It is regulated to mg / liter (0.05 ppm) or less.

At present, a hexavalent chromium concentration meter (hereinafter abbreviated as Cr concentration meter) in a low concentration range of 0 to 1 ppm is used to measure the hexavalent chromium concentration near the above environmental standard value. Has been put to practical use. This densitometer has a configuration based on an absorbance measurement method as shown in FIG. 11, and is provided with an optical cell 81 composed of a glass container into which a waste liquid 80 is injected. A light source 82 and a light receiver 83 are arranged. Then, a diphenylcarbazide reagent is added to the waste liquid 80 injected into the optical cell 81 to cause a color-forming reaction.
The light of m 2 is emitted from the light source 82, and the concentration of hexavalent chromium in the waste liquid is measured from the intensity of light received by the light receiver 83 when this light is transmitted through the optical cell 81.

[0004] On the other hand, the treatment process in the waste liquid treatment equipment in the plating plant and the like will be described with reference to FIG. 2 which is an explanatory diagram of the present invention.
Wastewater containing hexavalent chromium having a high concentration of several thousand ppm is received in the plating wastewater tanks 1 and 2 and then sent to the primary pH adjusting tank 3 where sulfuric acid is added to adjust the pH. Next, the mixture is sent to a reduction tank 4 where sodium bisulfite as a reducing agent is injected to reduce hexavalent chromium to harmless trivalent chromium. Thereafter, neutralization treatment is performed with sodium hydroxide injected in the secondary and tertiary pH adjusting tanks 5 and 6, and the trivalent chromium becomes water-insoluble chromium hydroxide. This is the next settling tank 7
Is settled and separated.

[0005] The separated chromium is collected in a sludge storage tank together with other metals such as zinc and iron, and the supernatant water of the precipitation tank 7 is sent to the next collecting raw water tank to check the concentration. It is released at. In such a waste liquid treatment process, the above-mentioned Cr concentration meter is used for concentration measurement immediately before final discharge. However, the concentration of the waste liquid in the middle of treatment greatly deviates from the measurement range, so that direct measurement with the above-mentioned Cr concentration meter is impossible.
On the other hand, a Cr concentration meter capable of measuring a high concentration region has not been put into practical use until now.Thus, in the process of waste liquid treatment, periodic concentration measurement by chemical analysis etc. is performed, The conditions are set by trial and error by the operator using the above-mentioned concentration measurement results as a guide. For example, since the waste liquid has a yellow tint in accordance with the hexavalent chromium concentration, the concentration of the waste liquid in the primary pH adjustment tank 3 is visually observed to estimate the concentration. By observing the reaction state from the state of the liquid, the processing amount per unit time and the injection amount of a chemical such as sodium bisulfite into the reduction tank 4 are adjusted.

[0006]

However, if the wastewater treatment process conditions are based on the visual observation of the operator as described above, it is difficult to accurately grasp the hexavalent chromium concentration. Tend to be overdosed,
For this reason, there has been a problem that the waste liquid treatment cost is high.

In addition, the operator must frequently perform visual monitoring. In addition, the operator is required to look into the waste liquid tank from above while paying attention to the scattering of the waste liquid in strong winds. There is a demand for improvement. Therefore, for example, it is conceivable to measure the hexavalent chromium concentration in the primary pH adjusting tank 3 with the above-mentioned Cr concentration meter and to set process conditions according to the measurement result. However, in this case, it is necessary to perform a pretreatment for diluting the waste liquid to be measured in advance so as to fall within the measurement range of 0 to 1 ppm in the Cr concentration meter. At this time, since the concentration of the target waste liquid greatly fluctuates, the degree of dilution is unknown. And the operation becomes extremely complicated.

Further, as described above, since the above-mentioned Cr concentration meter uses a method in which a reagent is added and measurement is carried out after a color-forming reaction, the management cost of the reagent is also required, resulting in an increase in operating costs. The present invention has been made in view of the above-described conventional problems, and has as its object to provide a sensor head that can be continuously immersed in a solution and can be continuously measured so that the sensor head can be easily applied to the waste liquid treatment facility described above. Is to do.

[0009]

In order to achieve the above object, the present invention relates to a sensor head immersed in a solution, wherein the light emitting housing houses light emitting means for emitting light into the solution. And a light-receiving housing for receiving light-receiving means for receiving light emitted from the light-emitting means and transmitted through the solution are formed in a watertight structure, and both housings are fixed at a predetermined interval, and the solution It is characterized in that it can be held at a predetermined height position inside.

In this case, the sensor head is immersed directly in the solution to perform continuous measurement of the solution, and the measurement reliability is excellent.
Handling is easy. Further, it is preferable that a circuit board constituting a power supply is disposed above the light receiving means in the light receiving housing, and it is preferable that a waterproof cord for supplying power from the outside be provided.

A Cr concentration meter for measuring the concentration of hexavalent chromium contained in a waste liquid or the like treated in a waste liquid treatment facility in a plating plant is a wavelength in the near ultraviolet region where the absorbance of the hexavalent chromium solution peaks. A light projecting means for emitting light having a center wavelength with a wavelength deviated to the blue side from
Light receiving means for receiving light emitted from the light projecting means and transmitted through the solution, and signal processing means for outputting a signal corresponding to the concentration of hexavalent chromium in the solution based on an intensity signal output from the light receiving means according to the amount of light received And can be provided.

When the concentration is determined from the absorbance in the solution as described above, the intensity of the transmitted light decreases exponentially with respect to the product of the concentration and the absorbance coefficient. In other words, when the absorbance coefficient is small, the degree of decrease in transmitted light intensity decreases even when the concentration increases. Therefore, in the above description, a light projecting unit that emits light having a wavelength at which the absorbance coefficient of the hexavalent chromium solution becomes appropriately small, that is, light having a wavelength deviated toward the blue side from the wavelength region in the near ultraviolet region where the absorbance peaks. The absorbance of the hexavalent chromium solution with respect to this light is detected. This makes it possible to detect a change in transmitted light intensity according to a change in density up to a higher density range. As a result, for example, 0
It can be configured as a Cr concentration meter having a wide measurement range of up to 4000 ppm.

Further, the Cr concentration meter is characterized in that the light source provided in the light projecting means comprises a blue light emitting diode which emits light having a center wavelength of 450 nm. By using a blue light emitting diode as a light source in this manner, a compact, lightweight, and long-life device can be achieved, and a device configuration that is inexpensive and easy to handle can be provided. And Cr
The densitometer is provided with a high-frequency power supply for applying a high-frequency voltage of a predetermined frequency to a light source provided in the light projecting means to blink the emitted light, and for extracting a signal of the frequency component from an intensity signal from the light receiving means. A pass filter is provided in the signal processing means.

In this way, the light emitted from the light source is flickered,
By detecting the Cr concentration based on the absorbance of the blinking light, the influence of disturbance light in, for example, outdoor use is prevented, and as a result, more accurate detection can be performed. Further, the Cr concentration meter is characterized in that a light emitting housing for housing the light emitting means and a light receiving housing for housing the light receiving means are arranged at a predetermined interval, and both of these housings are formed in a watertight structure. I have.

With such a watertight structure, continuous measurement can be performed by immersing both housings directly in, for example, a waste liquid in a waste liquid treatment tank. Therefore, it is not necessary to adopt a configuration in which the waste liquid is separately guided from the waste liquid treatment tank to the optical cell for measurement, and the measurement can be applied to the conventional waste liquid treatment tank, etc., so that the operation cost is reduced and the operability is reduced. improves. In particular, in a configuration in which the light source is composed of a light emitting diode, it is not necessary to apply a high voltage to operate the light source, so that sufficient safety is ensured.

Further, in the Cr concentration meter, the signal processing means is provided with data conversion means for comparing a signal based on the intensity signal from the light receiving means with a calibration curve data, converting the signal into a concentration value and outputting the result. It is characterized by. As described above, since the concentration is output after being converted into the concentration value, the concentration in the solution can be directly grasped, so that it is possible to immediately respond to, for example, the occurrence of an abnormality and to facilitate the monitoring operation.

The Cr densitometer includes a reference light source that emits light having a wavelength whose absorbance is not affected by the hexavalent chromium concentration;
Reference light receiving means for receiving light emitted from the reference light source and transmitted through the solution is further provided, and the signal processing means converts the intensity signals output from the light receiving means and the reference light receiving means to respective intensity signals. It outputs a signal corresponding to the concentration of hexavalent chromium in the solution based on this.

By using the reference light in this manner, a decrease in the intensity signal at the light receiving means due to the scattering of light due to dust or the like in the solution can be corrected by comparison with the above-described reference light. Highly reliable measurement can be performed in a processing facility or the like.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. First, an example of a waste liquid treatment facility will be described with reference to FIG. FIG. 1 shows a configuration of a waste liquid treatment facility in a steel plant that manufactures various steel materials.
In this waste liquid treatment facility, waste liquid discharged from many surface treatment plants and cold rolling plants is received, and harmful hexavalent chromium contained therein is reduced to harmless trivalent chromium and precipitated. For this purpose, first, as a receiving tank, a thick plating wastewater tank 1 for storing a high-concentration waste liquid having a hexavalent chromium concentration exceeding 1000 ppm, and a hexavalent chromium concentration of 100 ppm
A general plating wastewater tank 2 for storing a certain amount of waste liquid is provided. The waste liquid in the concentrated plating waste water tank 1 is sent to the general plating waste water tank 2 little by little, diluted with the waste liquid in the waste water tank 2, and further processed together with the waste liquid.

The waste liquid from the general plating waste water tank 2 is first
The solution is sent to a pH adjusting tank 3 where sulfuric acid is added to promote a reduction reaction described later to adjust the pH to about 2 to 3. Next, it is sent to the reduction tank 4, where sodium bisulfite as a reducing agent is injected, and hexavalent chromium is reduced to trivalent chromium as shown in the following reaction formula. 4H ₂ CrO ₄ + 6NaHSO ₃ + 3H ₂ SO ₄ → 2Cr ₂ (SO ₄ ) ₃ + 3Na ₂ SO ₄ + 10H ₂ O After reduction, alkaline agent such as sodium hydroxide injected into secondary and tertiary pH adjusting tanks 5 and 6 , The trivalent chromium becomes water-insoluble chromium hydroxide as shown in the following formula.

Cr ₂ (SO ₄ ) ₃ + 6NaOH → 2Cr (OH) ₃ + 3Na ₂ SO _{4 In} order to remove these precipitates, an auxiliary agent is further injected and sent to the next precipitation tank 7, whereby Chromium is settled and separated in this settling tank 7. The sedimented chromium compound is collected in a sludge storage tank together with other metals such as zinc and iron, and the supernatant water of the sedimentation tank 7 is sent to the next collecting raw water tank to confirm the final concentration. It is released at.

The primary pH adjusting tank 3 and the secondary and tertiary pH adjusting tanks 5 and 6 are provided with pH meters 8.9 and 10, respectively. Primary depending on the value
Supply amount of sulfuric acid to pH adjustment tank 3, secondary and tertiary pH adjustment tanks 5.6
The supply amount of the alkali agent is controlled. The reduction tank 4 is provided with a reduction potentiometer (ORP meter) 11 so that the degree of progress of the reduction reaction in the tank 4 can be monitored.

The above-mentioned primary pH adjusting tank 3 is further provided with a Cr concentration meter 30 for detecting the hexavalent chromium concentration in the waste liquid. In accordance with the concentration detected by the densitometer 30, the amount of waste liquid sent from the thick plating wastewater tank 1 to the general plating wastewater tank 2 is controlled by the flow control valve 12, and the primary pH adjustment tank is fed from the general plating wastewater tank 2. The adjustment of the amount of waste liquid sent to the fuel cell 3, ie, the amount of waste liquid processed per unit time, is controlled by the flow control valve 13.
It is performed in. Further, the opening degree of the flow control valve 14 provided in the reducing agent supply line is adjusted in accordance with the concentration detected by the Cr concentration meter 30, whereby the sodium bisulfite is supplied to the reducing tank 4. The injection amount is controlled.

The waste liquid 6 flowing into the primary pH adjusting tank 3
The chromium (VI) concentration varies over a wide range of over 1,000 ppm. Therefore, the Cr concentration meter 30 installed in the tank 3 has a wide measurement range, and furthermore, the reliability of detection is not affected by other metal ions or complex ions such as zinc and iron contained in the plating waste liquid. Is required. The detection method of the Cr concentration meter 30 configured to have such performance will be described below.

FIG. 3 shows the results of an investigation of the light absorbance of the wastewater sent from the primary pH adjusting tank 3 to the reducing tank 4. This is because, as shown in FIG. 4, the wastewater 21 is put into a glass measuring cell 20 of a predetermined shape with a thickness dimension (optical path length) d of, for example, 5 mm, and the wavelength of light applied to the measuring cell 20 is changed. This is a measurement of a change in the intensity of the transmitted light when the light is applied. As shown in FIG. 3, the wastewater received before the injection of the reducing agent, that is, the wastewater having a hexavalent chromium concentration of “large”, the wastewater during the reduction treatment having a concentration of “medium”, and the wastewater having a concentration of “small”
3 shows measurement results of three types of wastewater having been subjected to reduction treatment.

As shown in the figure, wastewater having a high concentration of hexavalent chromium has absorbance peaks at a wavelength of about 260 nm and near UV of 340 to 350 nm, respectively. Even when the concentration of hexavalent chromium is reduced, the influence of other metal ions and the like is large, and there is little change in absorbance with respect to the concentration of hexavalent chromium. In contrast, 340-3
In the absorption band having a peak at 50 nm and extending up to 500 nm, the substance having an absorption band in this region is not contained in the waste liquid in the waste liquid treatment facility described above, and therefore, corresponds only to the hexavalent chromium concentration. The change in absorbance appears.

Therefore, the Cr concentration meter 30 is premised on measuring the Cr concentration by detecting a change in absorbance in the above-mentioned absorption band, and further expanding the measured concentration range from 0 to several thousand ppm. , Shifted from the peak wavelength range of 340 to 350 nm,
A method of detecting hexavalent chromium concentration in wastewater with blue light having a wavelength of 450 nm is adopted, and a high-luminance blue light emitting diode having a peak at the above wavelength is used as a first light source (hereinafter also referred to as a blue LED).
Used as

Further, dust and the like are also contained in the wastewater, which scatters light transmitted through the wastewater and lowers the transmitted light intensity. A two-color detection method that separately irradiates reference light is adopted. As shown in FIG. 3, since the absorbance of the light having a wavelength of 500 nm or more is not affected by a change in the concentration of hexavalent chromium as shown in FIG. 3, light in the near infrared region having a wavelength of 850 nm is used as the reference light. A light emitting diode having a peak in this wavelength region is used as a second light source (hereinafter, also referred to as a red LED).

FIG. 5 shows the respective emission spectrum distributions of the blue LED and the red LED. Furthermore, in the wastewater treatment equipment, it is assumed that the Cr concentration meter 30 is used outdoors,
At this time, as shown in FIG. 6, there is a possibility that disturbance light is further mixed into the light from each of the light sources. Therefore, to prevent the detection accuracy from deteriorating due to the disturbance light, the red LED
A 3 kHz high-frequency power supply is applied to each of the blue and blue LEDs to make them blink, and the transmitted light intensity of these blinking lights is detected.

FIG. 7 shows the structure of Cr formed by adopting each of the above methods.
2 shows a sensor head unit 31 of the densitometer 30. The sensor head section 31 includes a light emitting housing 32 and a light receiving housing 33. The two housings 32 and 33 are spaced apart from each other at a predetermined interval on a substantially horizontal base plate 34, as shown in FIG. Fixed. Since the distance between the housings 32 and 33 is fixed as described above, the distance does not fluctuate, and the measurement of the solution can be performed accurately while the sensor head is directly immersed in the solution.

In particular, since the waste liquid in the waste liquid treatment equipment in which the sensor head 31 is immersed is flowing, if the housings 32 and 33 are not fixed to each other, the flowing waste liquid causes the two housings 32 and 33 to flow. The interval is easily fluctuated, and if the interval fluctuates, accurate concentration measurement cannot be performed.
In the sensor head section 31, since the distance between the housings 32 and 33 is fixed, accurate measurement can be performed without fluctuation of the distance.

The light-transmitting housing 32 having a rectangular parallelepiped block shape is formed with a recessed hole 32a which is recessed substantially inward from the outer wall surface on the light-receiving housing 33 side, and an inner end of the recessed hole 32a. The first light source (blue LE) constituting the light projecting means
D) 35 and a second light source (red LED) 36 as a reference light source are provided. The light sources 35 and 36 are fixed to be adjacent to each other, with the light emitting direction of each light being directed horizontally to the light receiving housing 33 side. A transparent quartz glass 37 is hermetically attached to the outer wall surface on the light receiving housing 33 side so as to cover the opening end of the concave hole 32a. Further, a condensing lens 38 is provided inside the quartz glass 37 in the recessed hole 32a, and the light emitted from both light sources 35 and 36 becomes substantially parallel light by the condensing lens 38. Are emitted to the light receiving housing 33 side.

On the other hand, as shown in FIG. 3A, a light receiving housing 33 formed larger than the light projecting housing 32 is provided with a box-shaped container 33c on a side wall plate 33a via a seal packing 33b. It is formed so as to be assembled and has a substantially rectangular parallelepiped shape as a whole. As shown in FIG. 2B, a through hole 33d coaxial with the recessed hole 32a is formed in the bottom surface of the wall surface facing the light emitting housing 32. A transparent quartz glass 39 is hermetically attached along the wall surface so as to cover the opening end of 33d. Further, a scattering plate 40 and a condenser lens 41 are sequentially disposed in the through hole 33d.

Inside the light receiving housing 33, a light receiving unit block 42 which is in contact with the above-mentioned wall surface from the inside is fixed on the bottom side thereof. This light receiving section block 42 has
A horizontal hole 42a penetrating horizontally on the same axis as 33d, and a vertical hole 42b penetrating upward from an intermediate position of the horizontal hole 42a are formed. A half mirror 43 is provided at the intersection of the two holes 42a and 42b, and at each opening end of the two holes 42a and 42b, a first light receiving element 44 as a light receiving means composed of a photodiode and a reference light source as a light source. The second light receiving element 45 is attached. Accordingly, light that enters the light-receiving housing 33 from the light-emitting housing 32 side through the quartz glass 39 sequentially passes through the scattering plate 40 and the condensing lens 41, then passes through the half mirror 43, and proceeds straight as it is horizontally. The light is split into light and light that is reflected by the half mirror 43 and travels upward. One light is incident on the first light receiving element 44 and the other light is incident on the second light receiving element 45.

Note that an infrared light cut filter 46 is provided on the front surface of the first light receiving element 44 so that
The light receiving element 44 includes a first light emitting diode including the blue light emitting diode.
Light from the light source 35 is incident, and outputs a signal corresponding to the intensity of the incident light. On the other hand, a visible light cut filter 47 is provided on the front surface of the second light receiving element 45, whereby light from the second light source 36 composed of an infrared light emitting diode is incident on the second light receiving element 45, A signal corresponding to the light intensity is output.

On the other hand, on the upper side in the light receiving housing 33, a circuit board 48 on which circuit elements constituting a high-frequency power supply and the like to be described later are mounted is provided. in this way,
When the circuit board 48 is arranged above the light receiving means, the sensor head becomes compact. That is, when the light receiving means and the circuit board 48 are arranged horizontally in the light receiving housing 33, the sensor head portion 31 becomes large in the lateral direction (the bottom area becomes large). When the width increases in the lateral direction, the resistance increases when the sensor head section 31 advances and retreats to the waste liquid.

By arranging the circuit board 48 above the light receiving means, the sensor head 31 becomes compact without being enlarged in the lateral direction, and has a small resistance when moving into and out of the waste liquid, so that the handling is easy. Waterproof cord connectors 49 and 50 are attached to the upper end surfaces of the light receiving housing 33 and the light emitting housing 32, respectively. Power is supplied and a detection signal is output.

As described above, power is supplied from the outside via the waterproof cord, and continuous measurement is possible in a state of being immersed in the solution, so that handling is easy. Further, the entirety of the sensor head 31 is immersed in the waste liquid of the primary pH adjustment tank 3 on the wall surface above the quartz glass 39 in the light receiving housing 33, and the sensor head 31 is held at an upper position for holding at a predetermined height position. An extending operation pipe 53 is fixed via a mounting plate 54.

Therefore, if the sensor head 31 is held at a predetermined height in the waste liquid, continuous measurement in a immersed state is possible. Thus, the above-described sensor head unit 31
The whole is immersed in a waste liquid to measure the hexavalent chromium concentration and is configured as an immersion type. For this reason, each of the housings 32 and 33 is manufactured in a water-tight structure, and is further configured to enclose a desiccant such as silica gel so as to prevent dew condensation from occurring in each built-in optical component. In addition, if the specific shape and dimensions of the sensor head unit 31 having the above configuration are shown as examples, the length indicated by L in the figure is 120 mm, and the width indicated by W is
The height dimension indicated by 70 mm and H is 135 mm, and the distance between the two quartz glasses 37 and 39, that is, the optical path length d in the waste liquid is set to 5 to 15 mm.

As shown in FIG. 1, circuit elements constituting a 3 kHz power supply 61 and a 10 kHz power supply 62 are mounted on the circuit board 48 in the light receiving housing 33. Commercial power supplied from the outside is reduced to a predetermined light emitting diode operating voltage and converted to a high frequency voltage by the high frequency power supplies 61 and 62, respectively, and applied to the first and second light sources 35 and 36. Thereby, as described above, the first light source 35
Blue light blinking at 3 kHz, and 10 kHz from the second light source 36
Infrared light blinking at z is emitted.

These emitted lights are respectively transmitted to the first light receiving element 44
The light enters the second light receiving element 45, and a signal corresponding to the intensity of the incident light is output from each of the light receiving elements 44 and 45. These output signals are sent to a signal processing device (signal processing means) 63.
The signal processing device 63 includes first and second bandpass filters 64 and 65. First bandpass filter 64
Is for passing the frequency component of 3 kHz in the output signal from the first light receiving element 44. Therefore, the signal A after passing through the filter 64 is the light emitted from the first light source 35 and transmitted through the waste liquid. Is obtained, and the influence of disturbance light is removed. Similarly, the second band-pass filter 65 passes the frequency component of 10 kHz in the output signal from the second light receiving element 45. Therefore, the signal B after passing through the filter 65 is emitted from the second light source 36 to be a waste liquid. The signal corresponds to the intensity of the light transmitted through the inside.

From these two signals A and B, the hexavalent chromium concentration C in the waste liquid is calculated. That is, assuming that the intensity of the blue light emitted from the first light source 35 is S and the optical path length in the waste liquid is d, for the signal A, log (A / S) = − εCd, where ε: molar extinction coefficient The relationship is established.

On the other hand, between the intensity R of the infrared light emitted from the second light source 36 and the intensity B when the infrared light is detected by the second light receiving element 45 after passing through the waste liquid, there is a hexavalent value in the waste liquid. A relational expression that attenuates depending on the optical path length d in the waste liquid without being influenced by the chromium concentration C is derived. From these, the hexavalent chromium concentration C is eventually obtained as follows: C = k1 + k2 · log (A / B) (1) However, k1 and k2 are calculated as constants.

In order to perform the operation based on the above equation (1), the signal processor 63 is provided with a divider 66 for calculating the ratio A / B of the signals A and B passing through the filters 64 and 65, A logarithmic converter 67 for calculating the logarithm of the output signal and performing the calculation based on the equation (1) is provided. The logarithmic converter 67 outputs a voltage signal Vo corresponding to the concentration of hexavalent chromium in the waste liquid. FIG. 8 shows the result of measuring the relationship between this voltage signal (hereinafter referred to as sensor output) Vo and the concentration of hexavalent chromium. As shown in the figure, the sensor output Vo changes from 0 ppm to 5
After showing a steep change to about 00 ppm, when the concentration further increases, the change gradient gradually becomes gentler, but the sensor output Vo gradually increases with an increase in the hexavalent chromium concentration until the concentration exceeds 4000 ppm. Therefore, it is possible to uniquely determine the hexavalent chromium concentration from the sensor output Vo over a wide range of 0 to 4000 ppm.

Therefore, as shown in FIG. 1, the signal processing device 63 has a storage device 68 for storing calibration curve data corresponding to the sensor output-concentration curve shown in FIG. 8 over a range of 0 to 4000 ppm. A density data converter 69 as data conversion means is further provided. In this concentration data converter 69, the sensor output Vo output from the logarithmic converter 67
Is compared with the above-mentioned calibration curve data at every predetermined sampling time, converted into a digital value as a density value C and output.

FIG. 9 shows the concentration value C and the chemical analysis value (manual analysis value) measured and output by the Cr concentration meter 30 for the same waste liquid or hexavalent chromium solution prepared at various concentrations. In the figure, ■ represents on-line data obtained by immersion in the waste liquid of the primary pH adjustment tank 3,
○ is off-line data obtained particularly for a hexavalent chromium solution prepared over a high concentration range. As shown in the figure, good measurement accuracy is obtained over a high range.

On the other hand, in FIG. 10, based on the sensor output Vo and the density value C output from the signal processing device 63,
The example which displayed the measurement result on the CRT for operation monitoring is shown. As indicated by an arrow in the figure, a digital display based on the density value C is performed in the No. 1 column in the upper table.
Measurement results based on the sensor output Vo are continuously displayed in the lower chart.

As described above, the Cr concentration meter 30 in the present embodiment is a high-intensity blue light emitting diode (center wavelength: 450 nm).
m) and a near-infrared light emitting diode (center wavelength: 850 nm) in combination with a two-wavelength absorbance measurement method. In particular, the measurement wavelength is shifted from the wavelength at which the absorbance of the hexavalent chromium solution peaks. By setting, concentration measurement over a wide range is possible.

Further, by using a light emitting diode as a light source, it is possible to reduce the weight and size, and further reduce the manufacturing cost and improve the durability. That is, for example, a mercury lamp that is usually used as a light source having a wavelength near the ultraviolet region requires a high voltage, so that it is difficult to use it in water from the viewpoint of safety, generates a large amount of heat, and cannot be compact, Although a problem such as a need for a countermeasure arises, the Cr concentration meter 30 of the present embodiment solves these problems. In particular, the Cr concentration meter 30 can be configured as a direct immersion type and can perform continuous measurement. Furthermore, the modulation is performed by blinking the light source itself, and the effect of disturbance light is removed by detecting the transmitted light, so that highly accurate measurement can be performed.

Such a Cr concentration meter 30 is installed in the primary pH adjusting tank 3 shown in FIG. 2 described above, and based on a detection signal from the Cr concentration meter 30, as described above, When the amount of sodium bisulfite injected into the tank is adjusted, and the hexavalent chromium concentration detected in the primary pH adjusting tank 3 is low, for example, sending the waste liquid from the thick plating wastewater tank 1 to the general plating wastewater tank 2 Control to increase the amount or amount of waste liquid sent from the general plating waste water tank 2 to the primary pH adjustment tank 3, or, conversely,
If the detected concentration is excessive, control is performed to reduce the amount of waste liquid from the general plating wastewater tank 2.

As a result, the processing efficiency is improved, and
The operation can be continued while maintaining the operation state corresponding to the processing capacity. In addition, it is not necessary to frequently monitor the color of the waste liquid in the primary pH adjusting tank 3 by visual observation at a high frequency, so that labor can be saved. Further, it is possible to suppress an increase in cost due to excessive injection of the medicine.

The above embodiment does not limit the present invention, and various changes can be made within the scope of the present invention. For example, in the above description, the first
Although an example in which the light projecting means is constituted by the light source 35 has been described, the light projecting means can be constituted by, for example, combining a white light source having a wide wavelength range with a filter that selectively transmits light near 450 nm. In this case, the light source may be further combined with a filter that transmits light near 850 nm, so that the light source also functions as a reference light source.

In the above embodiment, the signal processing device 63
The conversion into the density value C by the density data converter 69 in
Although the operation is performed by comparison with the calibration curve data stored in the storage means 68, for example, an operational amplifier to which a reference voltage corresponding to the calibration curve data is input is provided in the density data converter 69, and the density value C It is also possible to adopt another configuration such as outputting a signal corresponding to the above through an operational amplifier.

The above-mentioned Cr concentration meter 30 can also be used for a waste liquid treatment facility such as a plating factory for automobiles and home electric parts, and for other plating processes. It can greatly contribute to the improvement of the efficiency. As described above, the Cr concentration meter is 6
From the wavelength in the near-ultraviolet region where the absorbance of the chromium (VI) solution peaks, light with a center wavelength centered on the blue side is detected, and the transmitted light intensity is detected according to the change in the hexavalent chromium concentration in the solution I do. As a result, it is possible to measure up to a higher concentration range, and it is possible to configure a Cr concentration meter having a wide measurement range of, for example, 0 to 4000 ppm.

Further, since the Cr concentration meter is provided with a light source composed of a blue light emitting diode and irradiates the above-mentioned light, it is possible to reduce the size and weight, further extend the service life, and achieve an inexpensive and easy-to-handle device configuration. can do. Then, the Cr concentration meter blinks the light emitted from the light source and detects the Cr concentration based on the absorbance of the blinking light, so that the influence of disturbance light when used outdoors, for example, is prevented. As a result, more accurate detection can be performed.

Further, since the light transmitting housing and the light receiving housing of the Cr concentration meter are each formed in a watertight structure, it is possible to continuously measure both housings by directly immersing them in, for example, a waste liquid in a waste liquid treatment tank. is there. Therefore,
Since it can be directly applied to a conventional waste liquid treatment tank or the like, the operation cost is reduced and the operability is improved. In particular, in a configuration in which the light source includes a light emitting diode, it is not necessary to apply a high voltage to operate the light source, so that safety is also ensured.

Further, since the signal based on the intensity signal from the light receiving means is further converted into a concentration value and outputted from the Cr concentration meter, the concentration in the solution is directly displayed, whereby For example, the occurrence of an abnormality can be immediately grasped, thereby facilitating the monitoring operation. Then, since the Cr concentration meter further performs the concentration measurement using the reference light, a decrease in the intensity signal at the light receiving unit based on, for example, scattering of light due to dust or the like in the solution is also corrected by comparison with the reference light. Accordingly, highly reliable measurement can be performed even in a waste liquid treatment facility or the like.

As described above, it is possible to measure the concentration of hexavalent chromium in the liquid to be measured up to a high altitude region, and it is excellent in the reliability of the measurement, and is easy to handle and advantageous in cost. The total is obtained.

[0059]

As described above, according to the present invention,
Continuous measurement of the solution can be performed by immersing the sensor head directly in the solution.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a Cr concentration meter according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a waste liquid treatment facility provided with the Cr concentration meter.

FIG. 3 is a graph showing a measurement result of absorbance of a waste liquid in the waste liquid treatment facility.

FIG. 4 is a schematic diagram showing a method for measuring the absorbance.

FIG. 5 shows blue as a light source used in the Cr concentration meter.
4 is a graph showing emission spectrum distributions of an LED and a red LED.

FIG. 6 is an explanatory diagram for explaining a measuring method in the Cr concentration meter.

7A and 7B show a sensor head of the Cr concentration meter, wherein FIG. 7A is a partially cutaway side view, and FIG. 7B is a partially cutaway front view.

FIG. 8 is a graph showing a relationship between a sensor output and a hexavalent chromium concentration in the Cr concentration meter.

FIG. 9 is a graph showing a relationship between an output value from the Cr concentration meter and a chemical analysis value (manual analysis value).

FIG. 10 is an explanatory diagram showing a display example on a CRT based on an output from the Cr concentration meter.

FIG. 11 is a schematic diagram for explaining a conventional method for measuring hexavalent chromium concentration.

[Explanation of symbols]

 30 Cr concentration meter 31 Sensor head 32 Light emitting housing 33 Light receiving housing 35 First light source (light emitting means) 36 Second light source (reference light source) 44 First light receiving element (light receiving means) 45 Second light receiving element (reference light) Light receiving means) 48 Circuit board 51 Waterproof cord 52 Waterproof cord 61 3kHz power supply (high frequency power supply) 63 Signal processing device (Signal processing means) 64 First band pass filter 69 Concentration data converter (Data conversion means)

Claims (3)

[Claims] 1. A sensor head immersed in a solution, comprising: a light projecting housing for housing light projecting means for emitting light into the solution; and receiving light emitted from the light projecting means and transmitted through the solution. The light-receiving housings for housing the light-receiving means are each formed in a watertight structure, and both housings are fixed at a predetermined distance and are configured to be able to be held at a predetermined height position in the solution. Characteristic sensor head. 2. The sensor head according to claim 1, wherein a circuit board constituting a power supply is disposed above the light receiving means in the light receiving housing. 3. The sensor head according to claim 1, further comprising a waterproof cord for supplying power from outside.