JPH095315A - Method and device for analyzing concentrated solution - Google Patents

Abstract

PURPOSE: To analyze a concentrated halogen solution in real time by measuring the corrosion rate of a metallic container containing the solution and finding the halogen concentration of the solution from the measured value, etc., by an electrochemical method. CONSTITUTION: A gas 5 containing a halogen element is supplied to a metallic container 1 from the outside. A corrosion rate monitoring sensor 3 which monitors the corrosion rate of the container 1 and a temperature sensor 4 are set in a halogen solution 2 in the container 1. The sensors 3 and 4 are connected to an input section 6 and an arithmetic section 7 analyzes the solution for the halogen concentration of the solution. A displaying section 8 displays the analyzed results and a recording section 9 records the results. Since the concentration of a halogen element in the solution can be measured by electrochemically measuring the corrosion rate of the container 1, the concentration can be measured in real time while the solution is kept as it is. In addition, although the absorbing solution of a CO2 absorbing device used for preventing the global warming also concentrates and corrodes a metal with time, the solution can also be analyzed in the original state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentrated solution analysis method most suitable for analyzing the halogen concentration in a halogen solution concentrated in a metal container.

[0002]

2. Description of the Related Art Fluids handled by refuse incineration plants and chemical plants contain halogen gases such as highly corrosive chlorine (Cl ₂ ), bromine (Br ₂ ) and iodine (I ₂ ). When the halogen gas flows through the container holding the solution, the solution in the container comes into contact with the halogen molecules in the gas phase to absorb the halogen molecules from the gas phase to an equilibrium concentration according to Henry's law. However, if the container is made of metal, corrosive halogen gas corrodes the metal,
At the same time, the concentration of the halogen element in the solution is concentrated by several tens of times the equilibrium concentration according to Henry's law, and the concentration becomes high, which causes a leak accident of the device due to corrosion in the solution or in the high humidity portion. For this reason, in a refuse incineration plant, since corrosion is affected by the concentration, it is necessary to analyze the halogen concentration concentrated during the operation period and take countermeasures against the corrosion. Conventionally, the concentration of concentrated halogen was measured by taking a sample solution from the plant and bringing it back to an external analytical laboratory for analysis. A titration method or an optical analysis method is used for quantitative analysis of the halogen molecule or ion concentration in the solution. In the titration method, other reagents are added to the sampled solution for quantification. The concentration of a halogen molecule whose solution concentration has reached an equilibrium concentration according to the Henry's law can usually be analyzed in the state of a stock solution by using an absorptiometric method. The absorptiometric method irradiates a solution with light and determines the concentration based on the amount of light absorbed in the solution, and it is difficult to analyze a concentrated solution that causes metal corrosion. About 3 × 10 ~ ⁴ mo with iodine ion (I ₃ ~)
l / l is the limit of direct analysis.

[0003]

However, it is difficult to analyze the sampled high-concentration halogen solution as it is by the above-mentioned conventional absorptiometric analysis method, and when it is diluted, it is easily affected by the buffer action of the solution. In addition, since it is a batch analysis in which it is sampled from the plant and transported to an external analysis lab, it takes time to determine the concentration. It is an object of the present invention to analyze a concentrated halogen solution in contact with a metal container in real time.

[0004]

The above object is to measure the corrosion rate of a metal container containing a concentrated halogen solution,
This is achieved by determining the halogen concentration by an electrochemical method using the measured value of the metal corrosion rate.

[0005]

Halogen molecules in droplets formed in a solution to which halogens such as Cl ₂ , Br ₂ and I ₂ are supplied or in a wet gas phase are complex ions such as Cl ₃ ~, Br ₃ ~ and I. Corrodes the metals they come into contact with in the form of ₃ ~, and concentrates over time. Now, the volume of the solution (or droplet) is V, the area of the metal in contact with the solution is S, the equilibrium constant between the halogen molecule and its complex ion is K, the atomic weight of the metal is Wm, the halogen molecule concentration is Ch ₂ , and the complex When the ion concentration is Ch ₃ ~ and the metal corrosion rate is m, the complex ion concentration Ch ₃ ~ is given by the following equation.

[0006]

[Equation 2]

The halogen molecule concentration Ch ₂ in the solution is determined by the Henry's law given the concentration of the halogen gas supplied to the system. The equilibrium constant K is Cl ₂ (Cl ~ + Cl ₂ ⇔
For Cl ₃ ~), K≈0.2, Br ₂ (Br ~ + Br ₂ ⇔ B
It is 23.6 for r ₃ ~) and 710 for I ₂ (I ~ + I ₂ ⇔ I ₃ ~) (both at room temperature). Therefore, by measuring the corrosion rate m of the metal in real time from the equation (1) using an electrochemical sensor, it becomes possible to measure the halogen molecule concentration in the liquid as the halogen complex ion concentration in situ. Even if a liquid is not a large amount of liquid but a small amount of liquid such as water droplets, the concentrated concentration of halogen element in the liquid can be analyzed in the state of undiluted liquid by using the formula (1). Depending on the type of metal or the concentration of corrosive gas, the corrosion form of the metal surface differs from general corrosion, pitting corrosion or intergranular corrosion, but the value of the corrosion rate m depends on the corrosion form of these metals. Do not depend on the melting current. Therefore, the corrosion rate m of the metal can be measured in real time over time by measuring the polarization resistance in a direct current or by an electrochemical sensor measuring an alternating current impedance.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. As shown in the figure, 1 is a metal container, 2 is a halogen solution, 3 is a corrosion rate monitoring sensor, 4 is a temperature sensor, 5 is a gas containing halogen, 6 is an input unit including a key board (not shown), and 7 is a microcomputer. Computation part by, 8 is CR
A display unit 9 by T, and a recording unit 9 by a printer.
A gas 5 containing halogen is supplied to the metal container 1 from the outside. A corrosion rate monitoring sensor 3 and a temperature sensor 4 for monitoring the corrosion rate of the metal container 1 are installed inside the halogen solution 2 in the metal container 1. These sensors 3 and 4 are connected to the input unit 6, and the computing unit 7 analyzes the halogen concentration in the solution. These data are displayed on the display unit 8.
Is displayed and is recorded by the recording unit 9.

FIG. 2 is a flow chart showing the operation of the embodiment of the present invention. This figure shows the step of analyzing the rich halogen concentration in real time. First, in step 10, the volume V of the halogen solution 2 is input from a key board (not shown) of the input unit 6, and similarly, in step 11, the area S of the metal container 1 in contact with the halogen solution 2 is input. Further, in step 12, the atomic weight Wm of the metal is input. The equilibrium constant K is a constant that depends on temperature,
The equilibrium constant K at the temperature of the halogen solution 2 measured in step 13 is input in step 14. Using the halogen molecule concentration in the gas phase of the metal container 1 input in step 15, the halogen molecule concentration Ch ₂ in the halogen solution 2 in step 16 is calculated using the temperature of the halogen solution 2 measured in step 13. Is calculated. In step 17, the corrosion rate m of the metal forming the metal container 1 is measured, and in step 18, the halogen element concentration is calculated using the equation (1). The halogen element concentration calculated in step 19 is displayed on the CRT, and is ejected from the printer in step 20.

As described above, according to this embodiment, the concentration of the halogen element concentrated in the solution or the liquid droplets to which the halogen gas is supplied can be measured in real time because the corrosion rate of the metal container can be measured by an electrochemical method. It can be analyzed as a stock solution. Further, since the absorption liquid of the CO ₂ absorption device for the prevention of global warming also concentrates with time and corrodes the metal, it is possible to analyze the concentrated solution in the state of undiluted solution according to the present embodiment.

[0011]

According to the present invention, the corrosion rate of metal can be measured in real time using an electrochemical sensor, and the halogen molecule concentration in the solution can be analyzed in situ by calculation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

[Explanation of symbols]

 1 Metal Container 2 Halogen Solution 3 Corrosion Rate Monitoring Sensor 4 Temperature Sensor 5 Gas Containing Halogen 6 Input Section 7 Computing Section 8 Display Section 9 Recording Section

Claims (3)

[Claims] 1. A corrosion rate of a metal container holding a concentrated halogen solution is measured, and a measured value of the metal corrosion rate is included.
The contact area between the halogen solution and the metal container, the amount of metal atoms in the metal container, the volume of the halogen solution, the equilibrium constant between the halogen molecule and its complex ion, and the concentration of the halogen molecule are used according to a relational expression. A method for analyzing a concentrated solution, which comprises determining a halogen complex ion concentration of the halogen solution. 2. The method for analyzing a concentrated solution according to claim 1, wherein the halogen complex ion concentration of the halogen solution is determined by the following formula. [Equation 1] 3. A unit for measuring a corrosion rate of a metal container holding a concentrated halogen solution, and a unit for inputting a measured value of the metal corrosion rate to calculate a halogen concentration of the halogen solution. A concentrated solution analyzer characterized by the following.