JPH07128283A - Solution composition measuring system - Google Patents

Abstract

PURPOSE:To measure the composition of a condensing can internal solution in salt manufacturing process on-line at real time by providing each ion selective electrode of chloride ion, calcium ion, divalent positive ion, and potassium ion. CONSTITUTION:A bypass 2 is provided on the piping part to a crystallizing can of a condensing can internal solution, and an electrode 8 is set there. A measuring part 4 is formed of four ion selective electrodes (responding to chloride ion, calcium ion, divalent positive ion, and potassium ion, respectively), four reference electrodes, a temperature sensor 10 for temperature compensation, and an ion meter 12 for electrode potential measurement. An arithmetic part 6 is formed of a computer 14 for conducting a calculation on the basis of the electrode potential obtained from the ion meter 12 and the solution temperature obtained from the temperature sensor 10, and calculating various ion concentrations. Thus, the optimum control of the crystallizing process in salt manufacturing process can be automatically performed to allow a stable production of the product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution composition measuring system using an ion selective electrode, and more particularly to a solution composition measuring system suitable for measuring a liquid composition in a concentrated can in a salt making process.

[0002]

2. Description of the Related Art At a salt factory, seawater is concentrated by ion exchange membrane electrodialysis to obtain concentrated salt water (brine water), which is further concentrated in an evaporator to precipitate salt crystals (crystallization method). Is making salt. The solution in the salt-making step contains sodium ions, chloride ions as main components, and calcium ions, magnesium ions, potassium ions as impurities. The concentration of each of these ions changes depending on the concentration of brine.

Product crystals grow in the crystallization process while the solution is contained in the crystals as liquid bubbles. In addition, since the growth rate varies depending on the composition of the solution, the solution composition affects the quality such as product crystal composition and particle size. Therefore, in order to control the quality of product crystals, it is necessary to control the composition of the solution. The solution composition measurement is also necessary for determining the concentration ratio of the liquid in the concentrated can and the concentration limit of the solution, which are the operation standards of the crystallization operation.

Conventionally, a salt factory does not have a sensor for measuring the solution composition, and therefore the solution composition is measured by the following analysis method. Chloride ion: Titrated with silver nitrate standard solution Calcium ion, Magnesium ion: EDT
Titrated potassium ion with standard solution A: sodium ion measured with flame spectrophotometer or flame photometer:
Combined calculation by the above 4 components

[0005]

In the conventional solution composition measurement described above, the analysis by the titration method (analysis of Cl ⁻ , Ca ²⁺ , Mg ²⁺ ) requires manual and time-consuming work. Also,
The measurement range (K ⁺ analysis) by a photometer is limited to 0.01 to 0.30% in terms of potassium concentration, so the sample solution must be diluted. For this reason, it is the current situation that the solution composition can be analyzed only once a day, and since online measurement is also impossible, the following problems occur.

Problems in Quality Control of Product Crystals In salt production plants, dialysis brackish water and brine in which miscellaneous salt (a salt that does not become a product in a salt production plant) are redissolved are used as supply brine. Since these ratios change with time, the liquid supply composition also changes.

On the other hand, as described above, the product crystal grows while the solution is contained in the crystal as a liquid bubble in the crystallization step, but since the growth rate varies depending on the composition of the solution, the solution composition is the product crystal composition, Affects quality such as particle size.
Therefore, in order to control the quality of product crystals, it is necessary to control the composition of the solution, and to control the quality of the product, it is necessary to perform optimal control according to the solution composition. However, in a current salt factory, it is not possible to quickly measure the solution composition, so that the measurement result of the solution composition cannot be reflected in the product crystal control.

Problems in Controlling Crystallization Operations When conducting crystallization operations, there are mainly two control criteria. The first is the solution composition of the liquid in the concentrated can (the can that concentrates the supplied brine to saturation). Optimum operation in terms of product quality and energy cost is to concentrate the solution so that crystals do not precipitate in the concentrator and to a state as close to saturation as possible. By measuring the composition of the liquid inside the concentrated can in real time, the current composition can be grasped, so it becomes possible to determine the optimal concentration ratio for the concentrated can and control the composition of the liquid inside the concentrated can. Conceivable.

The second is the solution composition of the bitter juice concentrated can (can for boiling brackish water to the limit). At salt production plants, the limit of concentration of the solution is used as a control standard. The limit of concentration in an ionic brine system is the potassium chloride precipitation point. Concentration above this point results in the precipitation of potassium chloride, which significantly reduces product quality. Concentrating to the concentration limit as close as possible is an energy-optimal operation. This optimal concentration limit can be determined from the composition of the liquid in the concentrated can and the material balance in the crystallization process.

The above is the control standard for performing the crystallization operation, but at present there is no solution composition measuring system and the solution composition can be analyzed only once a day, so the operation near the limit cannot be performed, and it is considerably Since the operation is performed on the safety side, it is the current situation that the optimal crystallization operation cannot be performed.

As described above, at present, there is no solution composition measuring system during the salt making process, and since the composition analysis is performed manually, it takes time and labor, and the analysis result cannot be fed back to the process promptly. It is impossible to perform the optimum crystallization operation. Therefore, automation of the salt making process,
A system that can measure the composition of a solution is required for labor saving and optimization.

The present invention has been made in view of the above circumstances, and is suitable for measuring the composition of the liquid in the concentrated can in the solution in the salt-making step for the purpose of stable production of the product by optimal automatic control of the crystallization step. The purpose is to provide a measuring system.

[0013]

Means and Actions for Solving the Problems In order to achieve the above-mentioned object, the present inventor has examined the construction of a solution composition measuring system for a liquid in a can of a concentrated can using an ion selective electrode. The ion-selective electrode has an ion-selective membrane and selectively responds to the ion to be measured. And
An electric potential is generated on both sides of the membrane according to the activity (chemically effective concentration) of the ion to be measured in the solution. The potential difference between this generated potential and a constant reference potential due to the reference electrode is measured. The relationship between the measured electrode potential and the activity of the ion to be measured in the solution is represented by the following Nernst equation.

E = E ₀ + XlogA E: electrode potential A: activity of ion to be measured E ₀ : reference potential (constant) X: potential gradient

The activity A of the measurement target ion has the following relationship with the measurement target ion concentration C. Here, γ is an ion activity coefficient. A = γC

The ion activity coefficient γ greatly changes depending on the total ionic strength of the solution. The total ionic strength is defined by the following equation. Total ionic strength = 1 / 2ΣC _i Z _i ² C _i : Concentration of ion i Z _i : Charge of ion i

When the intensity of the background ion is higher than the measured ion concentration, the activity coefficient of the ion to be measured is constant, and the activity is directly proportional to the concentration. Therefore, the concentration can be measured from the relationship between the electrode potential and the concentration.

Conventionally, when the ion concentration is measured using an ion selective electrode, the sample solution is usually diluted so as not to affect the total ionic strength of the background solution, and an ionic strength adjusting agent is added to this. It was necessary to add the above to make the ionic strength constant and then perform the measurement. However, in order to measure the ion concentration with an ion-selective electrode online, it is necessary to carry out the measurement without dilution and without adding an ionic strength adjusting agent.

Therefore, as a first step, the present inventor
In order to investigate how the total ionic strength affects the measurement of the ion concentration in the solution during the salt-making process, an ion-selective electrode that responds selectively to the ions to be measured was used. An attempt was made to directly measure each ion concentration. However, for measurements of calcium ions, divalent cations, and potassium ions other than chloride ion concentration measurement using a chloride ion selective electrode, the correlation between the analytical value and the measured value can be obtained even if each ion selective electrode is used alone. It was bad and could not be used for practical purposes. That is, it was found that the ion activity coefficient is influenced by the total ionic strength, and thus it is not possible to measure the concentration with a single ion-selective electrode. However, with respect to chloride ions, since the total ion intensity and the chloride ion concentration are in a proportional relationship as described later, measurement was possible with a single electrode.

Next, as a second step, the inventor of the present invention examined whether the correction based on the total ion intensity is effective for the unmeasurable ions. The correction formula based on the total ion intensity is as shown below.

LogC _i = d ₀ + d ₁ E _i + d ₂ μC _i : concentration of ion to be measured [M] (i = Ca, Div., K, where Div. Represents divalent cation) E _i : measurement Electrode potential of target ion-selective electrode [mV] μ: Total ion intensity [−] _dj : Constant (j = 0, 1, 2)

As a result, by using this correction formula for correcting the electrode potential of the ion selective electrode with the total ion intensity,
It was found that the correlation between the analytical value and the measured value was improved for all the ions, and the correction by the total ion intensity was effective. However, since there is no sensor for measuring the total ionic strength, it was necessary to analyze the concentration of each ion in the solution and calculate from the analyzed value.

Further, as a third step, the present inventor conducted various studies on a sensor for measuring total ionic strength. As a result, it was found that the electrode potential of the chloride ion-selective electrode is proportional to the total ionic strength of the solution in the composition range of the liquid in the concentrated can, and this can be used as a sensor for measuring the total ionic strength. Then, it was found that by compensating the electrode potential of the ion electrode to be measured with the electrode potential of the chloride ion selective electrode, it is possible to construct a composition measuring system capable of measuring the liquid composition in a concentrated can, Came to make.

Therefore, the present invention provides a chloride ion-selective electrode, a calcium ion-selective electrode, a divalent cation-selective electrode, a potassium ion-selective electrode, a reference electrode for each of the ion-selective electrodes, and each of the ion-selective electrodes. A measuring system including a measuring unit including an ion meter for measuring an electrode potential of a positive electrode and a calculating unit that calculates each ion concentration from an electrode potential of each ion-selective electrode, wherein the calculating unit is The chloride ion concentration is calculated from the electrode potential of the chloride ion selective electrode, and the chloride ion selective electrode is used as the electrode potential of the calcium ion selective electrode, the divalent cation selective electrode and the potassium ion selective electrode. The calculation is based on the calculation of calcium ion concentration, divalent cation concentration and potassium ion concentration by adding the correction based on the electrode potential of Providing a solution composition measurement system that.

In the system of the present invention, the potential difference between each ion-selective electrode and the reference electrode is detected by an ion meter,
The electrode potential of each ion-selective electrode is measured, and the concentrations of chloride ion, calcium ion, divalent cation, and potassium ion in the solution are calculated from these electrode potentials.

In this case, in the calculation of calcium ion concentration, divalent cation concentration and potassium ion concentration,
The calculation is performed by adding the total ion intensity correction based on the electrode potential of the chloride ion selective electrode by the multiple regression method to the electrode potentials of the calcium ion selective electrode, the divalent cation selective electrode and the potassium ion selective electrode. The concentration of chloride ion can be calculated without correction from only the electrode potential of the chloride ion selective electrode. The calculation can be performed by the following formula.

When not corrected log C _i = a ₀ + a ₁ E _i C _i : measurement target ion concentration [M] (i = Cl, Ca, Div., K, where Div. Represents a divalent cation) E _i : electrode potential of measurement target ion-selective electrode [mV] a _j : constant (j = 0, 1)

Therefore, the chloride ion concentration can be calculated by the following formula. log C _Cl = a ₀ + a ₁ E _cl C _Cl : chloride ion concentration [M] E _cl : electrode potential of chloride ion selective electrode [mV] a _j : constant (j = 0, 1)

In case of correction (calcium ion, divalent cation, potassium ion concentration) log C _i = b ₀ + b ₁ E _i + b ₂ E _cl C _i : measurement target ion concentration [M] (i = Ca, Div. , K, where Div. Indicates a divalent cation) E _i : Electrode potential of the ion-selective electrode to be measured [mV] E _cl : Electrode potential of chloride ion-selective electrode [mV] b _j : Constant (j = 0, 1, 2)

The sodium ion concentration can be calculated from the measured values of chloride ion concentration, divalent cation concentration and potassium ion concentration by binding calculation.

Further, the magnesium ion concentration can be calculated by taking the difference between the divalent cation concentration and the calcium ion concentration.

In the present invention, the type of each ion-selective electrode is not limited, but as the chloride-ion selective electrode, for example, an amorphous solid membrane electrode, a calcium ion-selective electrode,
A liquid membrane electrode or the like can be used as the divalent cation selective electrode and the potassium ion selective electrode. There is no limitation on the type of reference electrode, single junction type,
Any type such as a double junction type can be used.
Further, the ion-selective electrode and the reference electrode may be installed separately, or a composite electrode in which these are integrated may be used.

In the system of the present invention, ion selective electrodes other than chloride ion selective electrodes, calcium ion selective electrodes, divalent cation selective electrodes and potassium ion selective electrodes and their references, if necessary. The electrodes may be provided in the measuring section.

In the system of the present invention, it is preferable that a temperature sensor for compensating the solution temperature is further provided in the measuring section, and the calculating section calculates each ion concentration from the electrode potential of each ion selective electrode and the solution temperature. Then, the composition of the liquid in the concentrated can can can be correctly measured by performing the temperature compensation calculation in the calculation unit in the temperature range of 30 ° C. to 60 ° C. which is the solution temperature range in the actual process.

[0035]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to the following examples.

(1) System Outline FIG. 1 shows an outline of a solution composition measuring system according to an embodiment of the present invention. In this system, a bypass 2 was provided in the pipe portion to the crystallization can of the liquid in the can of the concentrated can, and the electrode was installed there. This system includes a measuring unit 4 and a computing unit 6. The measurement unit 4 includes four ion-selective electrodes (chloride ion, calcium ion, divalent cation, potassium ion) and four reference electrodes (indicated by reference numeral 8 in the figure), and a temperature sensor 10 for temperature compensation. , And an ion meter 12 for measuring electrode potential. Further, the calculation unit 6 includes a computer 14 for calculating each ion concentration by performing calculation based on the electrode potential obtained from the ion meter 12 and the solution temperature obtained from the temperature sensor 10.

Here, the ion-selective electrode and reference electrode actually used are shown for reference, but the solution composition can be measured not only by the electrodes shown here but also by other electrodes.

Chloride ion Chloride ion selective electrode: Orion chlorine electrode 94-17 Reference electrode: Orion double junction comparison electrode
90-02 Internal liquid: Orion 90002 External liquid: KNO ₃ 10% aqueous solution

Calcium ion Calcium ion selective electrode: Orion calcium electrode 93-20 Reference electrode: Orion single junction comparison electrode 90-01 Internal liquid: KCl saturated aqueous solution

Divalent cation Divalent cation selective electrode: Orion divalent cation electrode
93-32 Reference electrode: Orion single junction reference electrode 90-01 Internal liquid: KCl saturated aqueous solution

· Potassium ion Potassium ion selective electrode: potassium electrode manufactured by Orion
93-19 Reference electrode: Orion double junction reference electrode
90-02 Internal liquid: Orion 90002 External liquid: NaCl 0.1M aqueous solution

(2) Sample solution composition and temperature The sample solution was prepared in a range that could correspond to the liquid composition in the concentrated can in the actual process of all salt manufacturing plants. That, Cl ^-
The concentration was 4 to 5M, and the pure salt rate was 88 to 94%. The measurement temperature was set to 30 to 60 ° C. so that it could correspond to the temperature of the liquid in the concentrated can in the actual process of all salt manufacturing plants. Table 1 shows the analysis results (12 points) of the solution composition.

[0043]

[Table 1]

(3) Effectiveness of this system This system pays attention to the fact that the electrode potential of the ion selective electrode is affected by the total ionic strength of the solution, and the electrode potential of the ion selective electrode is regarded as the total ionic strength. It is a system that compensates with the electrode potential of the chloride ion selective electrode in a proportional relationship. The following studies were conducted to show the effectiveness of this system.

In this system, the electrode potential of the chloride ion selective electrode is used instead of the total ionic strength.
In order to investigate whether or not it can be actually used, the relationship between the total ionic strength and the electrode potential of the chloride ion selective electrode was investigated. The results are shown in Figure 2. From the figure, the correlation coefficient between the total ionic strength and the electrode potential of the chloride-selective electrode is 0.99.
It can be seen that there is a linear relationship of 0 and that the electrode potential of the chloride ion selective electrode can be used to indicate total ionic strength.

Next, the effectiveness of the correction based on the total ionic strength and the correction based on the electrode potential of the chloride ion selective electrode was examined using calcium ion concentration measurement as an example.
FIG. 3 shows the relationship between the analysis value and the measured value when no correction was made, and FIG. 4 shows the case where the correction was made with the actual total ion intensity.

From FIG. 3, the correlation coefficient without correction is 0.
Since it is 880, the electrode potential of the calcium ion selective electrode varies due to the influence of the total ionic strength, and therefore it is recognized that correction is necessary. On the other hand, when the correction is performed with the total ion intensity, the correlation coefficient is 0.999 as shown in FIG. 4, and the linear relationship is considerably improved. Therefore, it is understood that the correction with the total ion intensity is effective.

FIG. 5 shows the relationship between the analytical value and the measured value when the chloride ion selective electrode is corrected by the electrode potential. From the figure, a good linear relationship with a correlation coefficient of 0.997 can be seen. Therefore, it is recognized that the correction by the electrode potential of the chloride ion selective electrode has the same effect as the correction by the total ion intensity and is an effective means.

In the above, the effectiveness of the present system was shown taking calcium ions as an example, but the following is a relational expression in which concentration measurements were performed for calcium ions and other ions. There is no need to correct the chloride ion concentration, and it is possible to measure with only one ion-selective electrode.
For the measurement of calcium ion, divalent cation and potassium ion concentration, correction by the electrode potential of the chloride ion selective electrode is necessary. In the following relational expression, C
_i is the i-ion concentration [M] in the solution, and E _i is the electrode potential [mV] of the i-ion selective electrode.

Chloride ion 30 ° C .: log C _cl = −0.1124-0.0132E _cl 40 ° C .: log C _cl = −0.0905-0.0127E _cl 50 ° C.:log C _cl = −0.0600−0.0119E _cl 60 ° C.:log C _cl = -0.0753-0.0116E _cl

Calcium ion 30 ° C .: log C _ca = −1.7998 + 0.0322E _ca + 0.0369E _cl 40 ° C.:log C _ca = −1.6323 + 0.0308E _ca + 0.0374E _cl 50 ° C.:log C _ca = −1.8917 + 0 .0315E _ca + 0.0333E _cl 60 ° C: log C _ca = -1.5832 + 0.0282E _ca + 0.0329E _cl

Divalent cation 30 ° C _. : log C _Div. = − 5.1125 + 0.0595E _Div. + 0.0582
E _cl 40 ° C: log C _Div. = -7.8444 + 0.0808 E _Div. + 0.0607
E _cl 50 ° C: log C _Div. = -9.5692 + 0.0976 E _Div. + 0.0751
E _cl 60 ° C: log C _Div. = -8.0298 + 0.0874 E _Div. + 0.0800
E _cl

Potassium ion 30 ° C .: log C _k = -1.4442 + 0.0027E _k + 0.0076E _cl 40 ° C .: log C _k = -1.5583 + 0.0004E _k + 0.0103E _cl 50 ° C .: log C _k = -1.3871 + 0 .0027E _k + 0.0064E _cl 60 ° C .: log C _k = −1.5281 + 0.0006E _k + 0.0091E _cl

From the above equations, the concentrations of chloride ion, calcium ion, divalent cation and potassium ion can be obtained. Also, magnesium ion can be calculated by taking the difference between the measured value of divalent cation concentration and the measured value of calcium concentration. The sodium ion concentration can be calculated from the chloride ion, divalent cation and potassium ion concentrations by binding calculation.

Table 2 shows the correlation coefficient with and without the correction of the electrode potential of the chloride ion-selective electrode. In all of the ions, a significant improvement in linearity was observed when the correction was performed, as compared with the case where the correction was not performed, and the correlation coefficient was 0.980 or more. Therefore, it is found that the correction by the electrode potential of the chloride ion selective electrode is effective, and that this system can be used practically.

[0056]

[Table 2]

(4) Temperature Compensation Mechanism This system can be used at a solution temperature of 30 to 60 ° C. based on the data of the solution temperatures of 30, 40, 50 and 60 ° C. That is, a mechanism for measuring the concentration by the interpolation method is attached. The calculation formula for the temperature compensation is shown below. By measuring the solution temperature using this temperature compensation mechanism, the solution composition can be measured in the actual solution temperature range of 30 to 60 ° C.

Chloride ion 30 ° C .: log C _Cl30 = a ₀ + a ₁ E _Cl30 40 ° C .: log C _Cl40 = a ₀ '+ a ₁ ' E _Cl40 50 ° C .: log C _Cl50 = a ₀ "+ a ₁ ''E _Cl50 60 ° C: when log C _Cl60 = a ₀ ''' + a ₁ '''E _Cl60

[0059] When the solution temperature _{30~40 ℃ (T ℃) logC ClT} = {(T-30) / 10} (a 0 '+ a 1' E Cl40) + {(40-
T) / 10}} (a ₀ + a ₁ E _Cl30 ) When the solution temperature is 40 to 50 ° C. (T ° C.) _{logC ClT} = {(T-40) / 10}} (a ₀ ″ + a ₁ ″ E _Cl50 ) ＋ {(50-
T) / 10}} (a 0 + a 1 'E Cl40) For solution temperature _{50~60 ℃ (T ℃) logC ClT} = {(T-50) / 10}} (a 0''' + a 1 ''' E _Cl60 ) + {(60-
T) / 10}} (a _{0 ``</sub> + a <sub>1 ``} E _Cl50 )

Other ions (calcium ion, 2
Divalent cation, 30 ° C. for potassium _{ions): log C i30 = b 0} + b 1 E i30 + b 2 E Cl30 40 ℃: log C i40 = b 0 '+ b 1' E i40 + b 2 'E Cl40 50 ℃: log C _{i50 = b 0 '' + b} 1 '' E i50 + b 2 '' E Cl50 60 ℃: log C i60 = b 0 '''+ b 1''' E i60 + b 2 '''E
_When it is _Cl60

When the solution temperature is 30 to 40 ° C. (T ° C.) log C _iT = {(T-30) / 10}} (b ₀ '+ b ₁ ' E _i40 + b ₂ 'E
_{Cl40) + {(40-T} ) / 10}} (b 0 + b 1 E i30 + b 2 E Cl30) If the solution temperature 40 to 50 ° C. for _{(T ℃) log C iT =} {(T-40) / 10} (b ₀ ″ ＋ b ₁ ″ E _i50 ＋ b ₂ ″ E
_{Cl50) + {(50-T} ) / 10} (b 0 '+ b 1' E i40 + b 2 'E Cl40) For solution temperature 50~60 ℃ (T ℃) log C iT = {(T-50) / 10}} (b ₀ '''+ b ₁ ''' E _i60 + b ₂ '''
E _Cl60 ) ＋ {(60-T) / 10}} (b ₀ ″ ＋ b ₁ ″ E _i50 ＋ b ₂ ″ E
_Cl50 )

(5) Example of application to actual process FIG. 6 shows an example of application of this system to an actual process of salt production. The concentrating can is a can for concentrating the supplied brine to saturation. Also, in order to prevent crystals from precipitating in the concentrated can,
Moreover, concentrating the solution to a state as close to saturation as possible is the optimum operation in terms of product quality and energy cost. Therefore, by measuring the composition of the liquid in the concentrated can using this system, the solution was saturated at 95%.
Control was performed so as to concentrate until.

The control was performed by an operation of decreasing the amount of supplied steam when the concentration was advanced from the setting and increasing the amount of supplied steam when the concentration was insufficient. FIG. 7 shows the time-dependent changes in the concentration of the liquid in the can of the concentrated can with and without the use of this system.

From the figure, when the present system is used, the enrichment is almost stable at the set value of about 95%, but when not used, the enrichment varies and the crystals do not precipitate. It can be seen that the concentration is much lower than the saturation. From the above, it was confirmed that this system is effective in controlling the liquid in the concentrated can.

[0065]

EFFECT OF THE INVENTION The solution composition measuring system of the present invention can measure the composition of the concentrated in-can solution in the salt making process without diluting the sample solution at the time of measurement and without adding the ionic strength adjusting agent. Therefore, it is possible to accurately measure the liquid composition in the can of the concentrated can in real time online. Therefore, by using the measurement system of the present invention, optimum automatic control of the crystallization process in the salt-making process can be performed, and stable production of products becomes possible. Further, the system of the present invention is effective in determining the concentration ratio of the liquid in the concentrated can and the concentration limit of the solution, which are the operation criteria of the crystallization operation, and can achieve stabilization of product quality and energy optimization. it can.
Furthermore, by performing temperature compensation within a fixed solution temperature range, the composition of the liquid in the concentrated can can be accurately measured even if the temperature of the solution changes.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of a solution composition measuring system according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the electrode potential and the total ionic strength of a chloride ion selective electrode.

FIG. 3 is a graph showing a calcium ion concentration measurement result when no correction is performed.

FIG. 4 is a graph showing a calcium ion concentration measurement result when correction is performed based on total ionic strength.

FIG. 5 is a graph showing the calcium ion concentration measurement results when correction is performed by the electrode potential of the chloride ion selective electrode.

FIG. 6 is a schematic view showing an example in which the measurement system of the present invention is applied to an actual process.

FIG. 7 is a graph showing changes over time in the degree of concentration of the liquid in the concentrated can with and without the use of the measurement system of the present invention.

[Explanation of symbols]

 4 Measuring Section 6 Computing Section 8 Ion Selective Electrode and Reference Electrode 10 Temperature Sensor 12 Ion Meter 14 Computer

Claims (7)

[Claims] 1. A chloride ion-selective electrode, a calcium ion-selective electrode, a divalent cation-selective electrode, a potassium ion-selective electrode, a reference electrode for each of the ion-selective electrodes, and an electrode for each of the ion-selective electrodes. A measurement system comprising a measuring unit having an ion meter for measuring potential and a calculating unit for calculating each ion concentration from the electrode potential of each of the ion-selective electrodes, wherein the calculating unit is the chloride ion selector. The chloride ion concentration is calculated from the electrode potential of the acidic electrode, and the calcium ion selective electrode, the divalent cation selective electrode and the potassium ion selective electrode are set to the electrode potential of the chloride ion selective electrode. A solution composition measuring system characterized by calculating calcium ion concentration, divalent cation concentration and potassium ion concentration with correction based on Stem. 2. The calculation unit calculates the electrode potential of the chloride ion selective electrode from the following formula log C _Cl = a ₀ + a ₁ E _cl C _Cl : chloride ion concentration [M] E _cl : chloride ion selective electrode. 2. The chloride ion concentration is calculated by the electrode potential [mV] a _{j of} : (constant) (j = 0, 1).
The described measurement system. 3. The total ionic strength based on the electrode potential of the chloride ion selective electrode by a multiple regression method to the electrode potentials of the calcium ion selective electrode, the divalent cation selective electrode and the potassium ion selective electrode, by the arithmetic unit. The measurement system according to claim 1, wherein the calcium ion concentration, the divalent cation concentration, and the potassium ion concentration are calculated by adding a correction. 4. An arithmetic unit calculates the following formula logC _i = b ₀ from the electrode potentials of the calcium ion selective electrode, the divalent cation selective electrode and the potassium ion selective electrode and the chloride ion selective electrode. + B ₁ E _i + b ₂ E _cl C _i : Target ion concentration [M] (i = Ca, Div., K, where Div. Is a divalent cation) E _i : Target ion-selective electrode Potential [mV] E _cl : Electrode potential of chloride ion selective electrode [mV] b _j : Calculating calcium ion concentration, divalent cation concentration and potassium ion concentration by constant (j = 0, 1, 2) The measurement system according to claim 3, wherein 5. The calculation unit calculates the chloride ion concentration,
The measurement system according to any one of claims 1 to 4, wherein the sodium ion concentration is calculated by a binding calculation from the divalent cation concentration and the potassium ion concentration. 6. The measuring unit includes a temperature sensor for compensating the solution temperature, and the calculating unit calculates each ion concentration from the electrode potential of each ion-selective electrode and the solution temperature. The measurement system according to claim 1. 7. The measurement system according to claim 1, wherein the calculation unit performs temperature compensation calculation in a solution temperature range of 30 ° C. to 60 ° C.