JP2016198697A - Organic acid solution decomposition system and organic acid solution decomposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic acid solution decomposition system and an organic acid solution decomposition method capable of combining high decomposition efficiency with suppression of progress of local corrosion (in particular, intergranular corrosion) of a reaction vessel, when decomposing an organic acid solution containing a carboxylic acid using ozone.SOLUTION: The organic acid solution decomposition system related to the present invention includes a decomposition tank to house an organic acid solution containing a carboxylic acid, an ozone injection device to inject ozone into the organic acid solution, and a measurement device to measure at least one parameter among potential of the decomposition tank, pH of the organic acid solution, carboxylic acid concentration, and carbon dioxide concentration. The ozone injection device controls a rate of ozone injection based on the measured value of the parameter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic acid solution decomposition system and an organic acid solution decomposition method, and more particularly to a decomposition system and a decomposition method for an organic acid solution containing a carboxylic acid.

  The quality of wastewater discharged into public water bodies due to industrial activities is strictly limited by the Water Pollution Control Law. Regarding organic matter in wastewater, BOD (biochemical oxygen demand), COD (chemical oxygen demand), and in some cases TOC (total organic carbon) are used as a concentration index of organic matter contained in wastewater. Conventional methods for removing organic substances in wastewater include many means such as activated sludge, coagulation separation, biodegradation, and high-temperature pyrolysis. Among these, the decomposition method using the oxidizing power of ozone is a system with a relatively low temperature around normal temperature because the organic substance decomposes and produces carbon dioxide, so there is little waste after treatment. Therefore, ozone is used because it has many advantages, such as being highly safe and reliable, being economical because it can use air as a raw material for ozone, and being able to easily decompose and remove excess ozone. In addition to organic decomposition systems, they have been extensively developed and commercialized for processes such as deodorization, bleaching, sterilization and chemical synthesis.

  As an organic substance decomposition treatment apparatus and treatment method using ozone, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2013-188655), a raw material gas for generating ozone includes a first gas containing oxygen and nitrogen. The flow rate of the first gas containing oxygen and the second gas containing nitrogen is a mixed gas of the second gas, based on the signal of the sensor group provided in the decomposition tank or the pipe connected to the decomposition tank, The raw material gas is supplied to an ozone generator to generate ozone and nitrogen oxides, and then supplied to a decomposition tank containing water to be treated. Discloses a system for decomposing organic matter using ozone, characterized by comprising means for measuring the corrosion potential.

  Patent Document 2 (Japanese Patent Laid-Open No. 2012-185013) measures the dissolved ozone concentration and oxidation-reduction potential of a radioactive liquid waste containing organic matter, and based on at least one measured value of the dissolved ozone concentration and the oxidation-reduction potential. There is disclosed a method for treating radioactive waste liquid, characterized in that the amount of ozone injected into the radioactive waste liquid is controlled.

  In Patent Document 3 (Japanese Patent Laid-Open No. 2001-353492), leachate containing an organochlorine compound and an organic substance is adjusted to a pH greater than 7.0 and less than or equal to 9.5, and ozone and A method of treating leachate, characterized by adding hydrogen peroxide, is disclosed.

  Patent Document 4 (Japanese Patent Application Laid-Open No. 2000-107778) discloses a water treatment method in which ozone gas is introduced into water to be treated for purification treatment, and a contact tank for contacting and mixing the water to be treated and ozone gas in a contact tank; Monitoring the pH of the water to be treated flowing inside each residence tank to ensure the reaction time between ozone and organic matter dissolved in the water to be treated, and adjusting the pH of the treated water to flow through the tank. A water treatment method characterized by suppression is disclosed.

  In Patent Document 5 (Japanese Patent Laid-Open No. 11-262833), water treatment is performed using an organic matter decomposing means that decomposes organic matter contained in the water to be treated by adding ozone to the water to be treated under alkaline conditions. The amount of alkali added to the water to be treated is controlled so that the pH of the treated water of the organic matter decomposition means is 7 or more, and the amount of ozone added to the water to be treated is 5% of the total organic carbon concentration in the water to be treated. Disclosed is a method for removing organic substances in water, characterized in that the amount of ozone added to the water to be treated is controlled so as to be 50 times by weight.

JP 2013-188655 A JP 2012-185013 A JP 2001-353492 A JP 2000-107778 A Japanese Patent Application Laid-Open No. 11-262833

  Generally, stainless steel such as SUS304 and SUS316L steel, which is a general-purpose material having both economic efficiency and corrosion resistance, is used in a decomposition treatment tank for wastewater containing organic matter. However, the water to be treated contains chloride ions, the temperature is high, the intermediate substance generated in the oxidation process of organic substances is organic acid, or there are excessive substances with high oxidizing power such as ozone. If this occurs, pitting corrosion or crevice corrosion, which is characteristic of stainless steel corrosion, may occur. In some cases, intergranular corrosion, and when stress is applied, progresses to stress corrosion cracking, which may cause serious equipment damage. In particular, care must be taken because the welded portion and its heat-affected zone, flanges, sludge pools, and other sites where gaps are formed are inferior in corrosion resistance.

  The organic acid solution to be decomposed by ozone may contain carboxylic acids such as formic acid and oxalic acid. Since this oxalic acid is generally used as a metal etching solution, particularly as an etching for producing a grain boundary structure, intergranular corrosion of stainless steel is inevitably caused by oxalic acid. In addition, when ozone coexists, intergranular corrosion is promoted because the potential of the constituent material increases. In order to suppress or reduce the intergranular corrosion, the solution is diluted to reduce the concentration of oxalic acid, or the amount of ozone to be injected (ozone injection rate) is reduced to reduce the actual ozone concentration in the solution. It is necessary. However, in this operation, the amount of the solution to be treated is increased in the former, and the decomposition rate of the organic acid is decreased in the latter. That is, there is a trade-off between increasing the efficiency of organic acid decomposition and inhibiting corrosion.

  The above Patent Documents 1 to 5 are not intended to decompose an organic acid solution containing a carboxylic acid, but include an improvement in decomposition efficiency when decomposing an organic acid solution containing a carboxylic acid with ozone, and a carboxylic acid. It does not sufficiently suppress the occurrence and development of local corrosion of stainless steel in an environment where organic acid solutions are decomposed by ozone.

  In view of the above circumstances, the present invention can achieve both high decomposition efficiency and suppression of progress of local corrosion (particularly intergranular corrosion) in a reaction tank when decomposing an organic acid solution containing carboxylic acid using ozone. An organic matter decomposition system and an organic acid solution decomposition method are provided.

  An organic acid solution decomposition system according to the present invention includes a decomposition tank that contains an organic acid solution containing a carboxylic acid, an ozone injection device that injects ozone into the organic acid solution, the potential of the decomposition tank, and the organic acid solution a measurement device that measures at least one parameter of pH, carboxylic acid concentration, or carbon dioxide concentration, wherein the ozone injection device controls an injection amount of ozone based on the measured value. And

  Further, the organic acid solution decomposition treatment method according to the present invention accommodates an organic acid solution containing a carboxylic acid in a decomposition tank, and the potential of the decomposition tank, the pH of the organic acid solution, the carboxylic acid concentration or the dioxide dioxide is measured by a measuring device. Measure at least one parameter of carbon concentration, and inject ozone into the organic acid solution with an ozone injection device at an injection amount determined based on the measured value to decompose the carboxylic acid It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, when decomposing | disassembling the organic acid solution containing formic acid and oxalic acid using ozone, it is possible to achieve both high decomposition efficiency and suppression of progress of local corrosion (particularly intergranular corrosion) in the reaction tank. An organic matter decomposition system and an organic acid solution decomposition method can be provided.

It is a block diagram showing the 1st example of the organic acid solution decomposition system concerning the present invention. It is a block diagram which shows the 2nd example of the organic acid solution decomposition | disassembly system which concerns on this invention. It is a graph which shows the time change of the potential of stainless steel at the time of ozone injection. It is a graph which shows the ozone injection rate and oxalic acid concentration dependence of the electric potential of stainless steel. It is the photograph which observed the surface of the stainless steel with the optical microscope at the time of hold | maintaining at a fixed electric potential (0.8V) for 4 h in an oxalic acid containing solution. It is the photograph which observed the surface of the stainless steel with the optical microscope at the time of hold | maintaining at a fixed electric potential (1.0V) for 4 h in an oxalic acid containing solution. It is the photograph which observed the surface of the stainless steel with the optical microscope at the time of hold | maintaining at a fixed electric potential (1.2V) for 4 h in an oxalic acid containing solution. It is a graph which shows the oxalic acid density | concentration dependence of the ozone injection rate when the electric potential of stainless steel is 0.8V. It is a graph which shows the oxalic acid concentration dependence of pH of an organic acid solution. It is a graph which shows the pH dependence of ozone injection | pouring speed | rate. It is a cross-sectional schematic diagram which shows the apparatus structure for measuring the electric potential of the decomposition tank.

  Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to these, and various improvements and modifications can be made without departing from the scope of the present invention.

[Organic acid solution decomposition system]
FIG. 1 is a block diagram showing a first example of an organic acid solution decomposition system according to the present invention. As shown in FIG. 1, an organic acid solution decomposition treatment system 100 a according to the present invention includes a mixing tank 3 for mixing an organic acid solution 1 (in this embodiment, oxalic acid 1 a and formic acid 1 b), and an organic acid solution 1. Hydrogen peroxide water injection device 4 for injecting hydrogen peroxide water to decompose formic acid 1b, decomposition tank 9 for storing organic acid solution 1 after decomposition of formic acid, and ozone injection for injecting ozone into decomposition tank 9 It has the apparatus 6 and the measuring apparatus 8a. The ozone injection device 6 includes an ozone generation device 6a and an ozone injection amount control device 6b.

  In this embodiment, an organic acid solution containing formic acid and oxalic acid is used as an object to be decomposed by ozone (organic acid solution 1). The organic acid solution containing formic acid and oxalic acid is assumed as, for example, a nuclear power plant waste. An organic acid solution containing formic acid and oxalic acid is used as a decontamination agent in order to remove iron oxide containing radioactive substances on the surface of the structural members constituting the nuclear power plant. In order to reduce the volume of the organic acid solution containing the radioactive material after decontamination, it is necessary to decompose the organic acid solution. Therefore, formic acid is decomposed mainly by hydrogen peroxide solution and oxalic acid is decomposed by ozone.

  It is preferable to use stainless steel having corrosion resistance for the mixing tank 3 and the decomposition tank 9 containing the organic acid solution. However, as described above, oxalic acid is used as a metal etching solution, and the decomposition tank 9 is exposed to a severe corrosive environment when ozone, which is a strong oxidizing agent, coexists. Therefore, in order to suppress the progress of corrosion in the decomposition tank 9, the present invention is based on measured values of various parameters in the organic acid solution (potential of the decomposition tank 9, pH of the organic acid solution, carboxylic acid concentration, carbon dioxide concentration, etc.). The amount of ozone injected into the decomposition tank 9 is controlled. Hereinafter, this ozone injection amount control method will be described in detail.

[Organic acid solution decomposition method]
First, oxalic acid 1a and formic acid 1b are respectively injected into the mixing tank 3 and mixed. Then, the mixed solution is transferred to the decomposition tank 9 through the pipe 5. In the middle of the transfer process (formic acid decomposition part 5a), hydrogen peroxide solution is injected by the hydrogen peroxide solution injection device 4 to decompose most of the formic acid. The organic acid solution in which most of the formic acid is decomposed is stored in the decomposition tank 9, and ozone generated by the ozone generator 6 is injected into the organic acid solution in the decomposition tank 9. A measuring device 8a is installed in the decomposition tank 9, and the ozone amount (concentration) injected into the decomposition tank 9 is controlled by the ozone injection amount control device 6b based on the measured value (signal). It has become.

  In the above configuration, since most of formic acid can be decomposed by injecting hydrogen peroxide water before injecting ozone, the decomposition tank 9 for injecting ozone (corrosion is most concerned) Oxalic acid accounts for the majority. In the formic acid decomposition part 5a (hydrogen peroxide injection environment), the potential of stainless steel is 0.6 V (vs. Ag / AgCl KCl saturation), so that corrosion hardly occurs (shown in FIGS. 5A to 5C described later). ).

(1) Behavior of potential of decomposition tank FIG. 3 is a graph showing a time change of potential of stainless steel at the time of ozone injection. In this experiment, an alloy containing welded portions of 32750 and SUS329J4L, which are duplex stainless steels, was used as the decomposition tank 9. Simulating the organic acid solution accommodated in the decomposition tank 9, adjusting the oxalic acid solution having a concentration of 4000 ppm (including 10 ppm formic acid and 10 ppm hydrazine), and the ozone injection rate was 10 g / h (per 0.2 L of the solution amount). The potential of the decomposition tank 9 when injected at a rate was measured. The temperature is 60 ° C. As shown in FIG. 3, when ozone is injected 20 minutes after the start of the potential measurement, the ozone concentration in the system increases, so that the potential is suddenly shifted to the noble side, and then shows a constant value near 0.8V. This is because ozone is consumed by the decomposition of oxalic acid. Further, after 200 min, the potential is shifted to the noble side again. The increase in the potential at this point is because the oxalic acid concentration in the system (in the solution) decreases, the consumption of ozone decreases, and the ozone concentration in the system increases accordingly. After that, it becomes a constant value again around 1.12V. This shows that the potential of stainless steel during oxalic acid decomposition depends on the ozone injection rate and the oxalic acid concentration.

  Next, the relationship between the potential of the decomposition tank 9, the ozone injection rate, and the oxalic acid concentration was examined in more detail. FIG. 4 is a graph showing the dependency of the potential of stainless steel (SUS329J4L) on the ozone injection rate and the oxalic acid concentration. The ozone injection rate (ozone injection amount) is a value per 0.2 L of solution volume, and the temperature is 60 ° C. As the oxalic acid concentration increases, the potential decreases. However, as described above, when the oxalic acid concentration is high, ozone is consumed for decomposition of oxalic acid, and the amount of ozone remaining in the system decreases. It is. Therefore, at the same oxalic acid concentration, the higher the rate of ozone to be injected (the greater the amount injected), the more excess ozone that is not consumed for the decomposition of oxalic acid, and the higher the potential.

(2) Corrosion potential of stainless steel The corrosion situation of stainless steel depends on the potential. 5A to 5C are photographs of the surface of stainless steel observed with an optical microscope when held at a constant potential for 4 h in an oxalic acid-containing solution. FIG. 5A shows the case of holding at 0.8V, FIG. 5B shows the case of holding at 1.0V, and FIG. 5C shows the case of holding at 1.2V. As shown in FIG. 5A, no corrosion was observed on the surface of the stainless steel when it was held at 0.8V. When maintained at 1.0 V in FIG. 5B, slight intergranular corrosion was confirmed on the surface of the stainless steel. Furthermore, remarkable intergranular corrosion was confirmed when held at 1.2 V in FIG. 5C. Therefore, it can be seen that corrosion can be avoided if the potential of the stainless steel is always kept at 0.8 V or less. This 0.8 V is defined as a corrosion inhibition critical value in the present invention.

(3) Determination of ozone injection rate The potential of stainless steel is determined by the ozone injection rate and the oxalic acid concentration as shown in FIGS. FIG. 6 is a graph showing the oxalic acid concentration dependence of the ozone injection rate when the potential of stainless steel is 0.8V. From FIG. 6, if the ozone injection amount is controlled according to the oxalic acid concentration in the decomposition tank 9, the potential of the stainless steel can be kept below the corrosion inhibition critical value (0.8 V) and the corrosion can be reduced. FIG. 6 is a graph when the temperature is kept constant at 60.degree. The graph of FIG. 6 naturally depends on the temperature. Here, the temperature is set to 60 ° C., and when the oxalic acid is decomposed with ozone, it can be decomposed most efficiently at 60 ° C. This is because the temperature is basically controlled at 60 ° C. Therefore, in general, control for changing the ozone flow rate with temperature change is not necessary, but a temperature sensor is added as a measuring device 8 to the decomposition tank 9, and the ozone injection amount is controlled by the ozone injection amount control device 6b based on the signal. It is also possible to control.

  As shown in FIG. 3, when ozone is injected into the oxalic acid solution, the potential is constant for 20 to 200 minutes after the ozone injection, and the potential is suddenly shifted to the noble side after 200 minutes. This is because there is a certain time lag until oxalic acid decomposes after ozone injection. Accordingly, the corrosion of the apparatus can be prevented by monitoring the potential and the oxalic acid concentration and reducing the ozone injection amount with the time when these values start to change as a trigger. A specific ozone injection amount may be obtained by measuring the oxalic acid concentration of the organic acid solution in the decomposition tank 9 using FIG. 6 as a calibration curve and controlling the ozone injection amount based on this value.

  There are no particular limitations on the method for measuring the potential of the decomposition tank 9 and the oxalic acid concentration of the organic acid solution, and conventional techniques can be used. FIG. 9 is a schematic diagram showing a configuration for measuring the potential of the decomposition tank 9. As a potential measuring device for the decomposition tank 9, for example, a configuration shown in FIG. 9 described later can be used (details will be described later). Further, as a method for quantifying oxalic acid, there is generally ion chromatography (Ion Chromatography, IC), but a commercially available simple measurement kit can also be used. In this case, a part of the organic acid solution is sampled, and the sampled solution can be analyzed outside the organic acid solution decomposing apparatus to determine the oxalic acid concentration.

  FIG. 2 is a block diagram showing a second example of the organic acid solution decomposition system according to the present invention. In the organic acid solution decomposition system 100b shown in FIG. 2, the difference from the organic acid solution decomposition processing apparatus 100a shown in FIG. 1 is that a catalyst layer 5b is provided in the middle of the pipe 5, and a measuring device 8b of the decomposition tank 9. Is composed of the sampling unit 10 and the analysis unit 11.

  In the embodiment shown in FIG. 2, oxalic acid 1a and a mixture 1c containing formic acid and hydrazine are contained. In this case, formic acid and hydrazine are decomposed in the catalyst layer 5b. Hydrazine is included as a decontamination agent. At this time, a Ru (ruthenium) -supported activated carbon catalyst can be used as the catalyst layer 5b. As described above, even when the organic acid solution contains other than formic acid and oxalic acid, the organic acid solution decomposition treatment method according to the present invention is applied by appropriately changing the configuration of the previous stage of the decomposition tank 9. Can do. Other portions are the same as those of the organic acid solution decomposition treatment apparatus 100a.

  As described above, according to the present invention, corrosion caused by a strong oxidizing environment when ozone or hydrogen peroxide is added in an environment where carboxylic acid is contained in an organic acid solution that is a liquid to be treated. In particular, local corrosion can be prevented. Since this system can maintain corrosion resistance even in a severe corrosive environment for metal materials, it is possible to use a general-purpose metal as the decomposition tank 9, and to provide a highly reliable and long-life organic material decomposition system. it can.

  Further, according to the present invention, corrosion of the decomposition tank 9 can be suppressed without excessively reducing the ozone injection rate. In other words, the ozone injection rate can be maintained to the maximum as long as the corrosion of the decomposition tank 9 is not suppressed. As a result, it is possible to provide an organic matter decomposition system and an organic acid solution decomposition method capable of achieving both high decomposition efficiency and suppression of progress of local corrosion (particularly intergranular corrosion) of the reaction vessel.

  There has never been an example of studying corrosion inhibition of stainless steel in an environment where carboxylic acid and ozone coexist with an organic acid solution containing carboxylic acid, and the present invention has been made based on a new problem. It is.

  In this example, a case where a pH measuring electrode is used as a measuring device will be described. In Example 1, the ozone injection amount is controlled based on the measured value of the oxalic acid concentration. However, since the oxalic acid concentration is an acid, the pH (hydrogen ion) changes according to the concentration change. Therefore, the ozone injection amount can be determined using a pH sensor so that corrosion does not occur. In this case, the horizontal axis of the diagram shown in FIG. 6 is not oxalic acid concentration but pH. As described above, since most of the components in the decomposition tank 9 are oxalic acid (formic acid is mostly decomposed by the preceding hydrogen peroxide solution), the pH is determined by the oxalic acid concentration.

  FIG. 7 is a graph showing the oxalic acid concentration dependence of the pH of the organic acid solution. FIG. 8 is a graph showing the pH dependence of the ozone injection rate. FIG. 8 is a graph produced from FIG. 6 and FIG. Based on FIG. 8, it is possible to determine the ozone injection rate for making the potential region (corrosion suppression critical value) that does not cause corrosion of the decomposition tank 9 from the pH value measured by the pH measurement electrode. Although there is no limitation in particular as a pH sensor, it is possible to use the semiconductor pH sensor etc. which use a glass electrode and an ion response field effect transistor.

  In this embodiment, the case where the potential measuring device 8c is used as the measuring device will be described. As shown in FIGS. 5A to 5C described above, in the oxalic acid environment, no significant corrosion occurs when the potential of the stainless steel is 0.8 V (Ag / AgClKCl saturation) or less. Corrosion can be suppressed by controlling the ozone injection amount so that the potential is always 0.8 V or less.

  FIG. 9 is a schematic cross-sectional view showing a configuration for measuring the potential of the decomposition tank 9. A metal electrode 20 and a reference electrode 21 are installed on the wall surface of the decomposition tank 9 using bolts 25, and lead wires 26 of the respective electrodes are connected to a potentiometer 22. The potentiometer 22 is connected to two voltage floor type differential amplifiers, and the potential difference between the two differential amplifiers is sent to the ozone flow rate controller as a corrosion potential signal. The metal electrode is insulated from the container wall 9 'of the decomposition tank. The reference electrode 21 and the metal electrode 20 can define a more accurate potential difference as close as possible.

  The metal electrode 20 needs to be the same material as the container of the target decomposition tank 9. In particular, since remarkable corrosion occurs in a welded part and a HAZ (Heat Affected Zone) part, it is desirable to use a metal electrode 20 having a welded part. In general, a commercially available silver-silver chloride electrode can be used as the reference electrode. A saturated potassium chloride solution is used as the internal solution.

  As described above, according to the present invention, when decomposing an organic acid solution containing formic acid and oxalic acid using ozone, high decomposition efficiency and suppression of the progress of local corrosion (particularly intergranular corrosion) of the reaction vessel are suppressed. It has been demonstrated that an organic matter decomposition system and an organic acid solution decomposition treatment method that can be compatible with each other can be provided.

Note that the above-described embodiments have been specifically described in order to help understanding of the present invention, and the present invention is not limited to having all the configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, a part of the configuration of each embodiment can be deleted, replaced with another configuration, or added with another configuration. For example, the parameters for determining the ozone injection rate are not limited to the oxalic acid concentration, pH, and potential of the decomposition tank described above, but may be the CO ₂ concentration generated during the decomposition of oxalic acid. In addition, the present invention is not limited to decontamination of the decontamination agent, but is also applicable to various processes (such as drifting, sludge treatment, sterilization, antifouling, deodorization, and pharmaceutical synthesis) that decompose the organic acid solution containing carboxylic acid using ozone. can do.

  DESCRIPTION OF SYMBOLS 1 ... Organic acid solution, 1a ... Oxalic acid, 1b ... Formic acid, 1c ... Mixture of formic acid and hydrazine, 3 ... Mixing tank, 4 ... Hydrogen peroxide injection device, 5a ... Formic acid decomposition part, 5b ... Catalyst layer, 6 ... Ozone injection device, 6a ... ozone generation device, 6b ... ozone injection speed control device, 8a, 8b ... measuring device, 9 ... decomposition tank, 10 ... sampling part, 11 ... analysis part, 100a, 100b ... organic acid solution decomposition system.

Claims (12)

A decomposition tank containing an organic acid solution containing a carboxylic acid;
An ozone injection device for injecting ozone into the organic acid solution;
A measuring device for measuring at least one parameter of the potential of the decomposition tank, the pH of the organic acid solution, the carboxylic acid concentration or the carbon dioxide concentration,
The ozone injection device controls an injection amount of ozone based on the measured value, and decomposes the organic acid solution.   The organic acid solution decomposition system according to claim 1, wherein the carboxylic acid is formic acid and oxalic acid. The measuring device has a sampling unit and an analysis unit,
The sampling unit collects a part of the organic acid solution,
The organic acid solution decomposition system according to claim 1, wherein the analysis unit performs the measurement on a part of the collected organic acid solution.   2. The organic acid solution decomposition system according to claim 1, wherein the ozone injection device controls an injection amount of ozone when the measured value starts to change. 3.   The organic acid solution decomposition system according to claim 1, wherein the ozone injection device controls an injection amount of ozone in accordance with a change amount of the measurement value.   The ozone injection device obtains a corrosion inhibition critical value of the parameter calculated from a relationship between the corrosion potential of the decomposition vessel measured in advance and the corrosion potential and the parameter, and the parameter is equal to or lower than the corrosion critical value. The organic acid solution decomposition system according to claim 1, wherein the ozone injection amount is controlled so as to be. An organic acid solution containing carboxylic acid is placed in a decomposition tank,
The measurement device measures at least one parameter of the potential of the decomposition tank, the pH of the organic acid solution, the carboxylic acid concentration or the carbon dioxide concentration,
An organic acid solution decomposition method comprising decomposing the carboxylic acid by injecting ozone into the organic acid solution by an ozone injection device at an injection amount determined based on the measured value.   The organic acid solution decomposition method according to claim 7, wherein the carboxylic acid is formic acid and oxalic acid.   The organic acid solution decomposition method according to claim 7, wherein the measurement is performed by collecting a part of the organic acid solution.   8. The organic acid solution decomposition method according to claim 7, wherein the ozone injection amount is controlled when the measured value starts to change.   8. The method for decomposing an organic acid solution according to claim 7, wherein the amount of ozone injected is controlled in accordance with the amount of change in the measured value.   The corrosion potential of the decomposition vessel measured in advance and the corrosion critical value of the parameter calculated from the relationship between the corrosion potential and the parameter are obtained, and the ozone injection amount is set so that the parameter is equal to or less than the corrosion critical value. The organic acid solution decomposition method according to claim 7, wherein the organic acid solution decomposition method is controlled.

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