KR100335601B1 - Apparatus for continuously reducing iron chloride aqueous solution - Google Patents

Abstract

In the present invention, in order to reduce the waste iron chloride solution in order to regenerate, in order to maintain an appropriate reduction rate and to enable continuous operation while using a column-filled column reactor, the iron-filled column into which the waste iron chloride solution is introduced A stirred reactor (2) including a reactor (1), an iron chloride solution discharged from the column reactor, a level indication control system (LIC) and a redox potential control system (AIC), and an aqueous solution of iron chloride in the stirred reactor It consists of a circulation pump (3) for circulating to the column reactor, the level indicator control system (LIC) measures the height of the aqueous iron chloride solution in the stirred reactor to control the flow rate of the waste iron chloride solution introduced into the column reactor, The redox potential control system (AIC) measures the redox potential of the aqueous solution of iron chloride in the stirred reactor It provides a continuous reduction apparatus of ferric chloride aqueous solution of iron chloride solution to control the flow rate discharged from the group stirred reactor.

Description

Continuous reduction apparatus of aqueous iron chloride solution {APPARATUS FOR CONTINUOUSLY REDUCING IRON CHLORIDE AQUEOUS SOLUTION}

The present invention relates to a method for reducing trivalent ferric chloride in a ferric chloride solution to divalent ferric chloride in a method for efficiently regenerating an aqueous waste iron chloride solution which is an etching solution used to etch iron or an iron-nickel alloy or the like. More specifically, in a method of depositing / removing a metal having a less ionization tendency than iron by reacting a waste iron chloride solution containing heavy metals such as nickel with iron, trivalent ferric chloride in the iron chloride solution is converted into divalent ferric chloride. It is a method of reducing. By supplying the ferric chloride solution reduced in this way to a two-step process for removing heavy metals such as nickel, the waste etching solution regeneration method by the iron reduction method becomes more useful.

Ferric chloride (FeCl ₃₎ The aqueous solution of metal after (pure iron and an iron alloy, copper alloy, nickel alloy, etc.) is used as the etching solution (etchant) for etching was typically dissolved iron in hydrochloric acid, made of ferrous chloride (FeCl ₂₎ It is produced by oxidizing with chlorine gas. The ferric chloride aqueous solution used for etching is somewhat different depending on the metal to be etched, the etching rate, and the etching unit, but a mixture of 30% to 45% ferric chloride and 5% to 15% ferric chloride is usually used. In particular, highly pure aqueous iron chloride solution is used as an etching solution used to produce shadow masks and semiconductor lead frames used in CRTs.

The shadow mask material used for small TVs or small computer monitors of 25 inches or less is pure iron, and the waste iron chloride solution used for etching thereof can be recovered and oxidized with chlorine gas for simple regeneration. However, the shadow masks used in the CRTs of large 25-inch and larger TVs, high definition televisions (HDTV), and high-end large computer monitors are made of iron-nickel alloys (Invar alloy, Alloy-42), and these alloys are etched solutions. (Iron chloride solution) contains nickel ions and the like, so that the iron chloride solution cannot be recycled with high purity by the existing treatment technology. In addition, when nickel ions are accumulated in the aqueous iron chloride solution, etching holes are uneven and etching efficiency is lowered, making it impossible to use. Therefore, it is necessary to remove heavy metal ions, such as nickel, from the spent etching solution using a new iron chloride solution.

Metal ions such as nickel are removed from the spent iron chloride solution (containing 30% -45% ferric chloride and 5% -15% ferric chloride and 0.2% -2% nickel and other heavy metals) used in etching. Iron reduction methods for depositing / removing metals (copper, chromium, nickel, etc.) that have less ionization tendency than iron by adding excessive amounts of iron are mainly used. In addition, there are ion exchange, electrolysis, and crystal formation.

In the iron reduction method (Japanese Patent Laid-Open No. 62-192588 and Japanese Patent Laid-Open No. Hei 1-67235), metal iron is added to an iron chloride etching waste solution, and ferric chloride is reduced to ferric chloride by the following first reaction. The metal iron powder is added in excess to precipitate nickel ions into nickel metal by the following second reaction.

First reaction (reduction reaction): 2FeCl ₃ + Fe = 3FeCl ₂

Second reaction (nickel removal reaction): NiCl ₂ + Fe = FeCl ₂ + Ni

In Japanese Patent Publication No. 61-44814, the above two reactions were simultaneously performed in one reactor (using a bulk iron and a stirred reactor) to remove chromium, copper, and lead, but nickel removal was not efficient. Japanese Patent Application Laid-Open No. 62-192588, Japanese Patent Application Laid-Open No. Hei 1-167235, Hei 5-255869, Hei 5-263273, Hei 9-156930, etc., is a first step reduction reaction and a second step with relatively low calorific value. The nickel reduction reaction was separated to improve the iron reduction method. In the two-step nickel elimination reaction, nickel precipitates on the surface of the steel, and the reaction rate is drastically reduced. Therefore, to improve this, it is necessary to use iron with a large surface area and to increase the nickel content in solids separated from iron to effectively recover and recycle the nickel. It became possible.

In the first reaction, the reduction reaction, iron (JP-A-10-18061, H6-128760) is used for the continuous reaction, but the reduction reaction occurs spontaneously even at room temperature. It's faster. Therefore, in the first reaction, inexpensive iron materials such as iron scrap without using expensive iron powder (Japanese Patent Laid-Open Publication No. 62-192588, Pt. 1-67235, Pt. 5-125563, Pt. 5-255869, Pt. 9-156930) Also used. In the case of using iron scraps such as iron pieces and iron rods, a reactor in the form of a column in which steel is added to a stirring tank or filled with iron is used, and is operated in a batch process rather than in a continuous process.

In the reduction process, which is the first step of the iron reduction method to remove heavy metals such as nickel by adding iron to the waste etching solution of iron chloride solution, the method of using iron materials such as iron scrap, which is inexpensive and inexpensive, does not use expensive iron. Economics can be increased, but there is a problem in that it is complicated and the device becomes large according to the use of the ash process. In the case of using a column type reactor, it is impossible to stir due to the characteristics of the reactor, and thus it is not possible to promote contact between the steel and the aqueous solution, and it is difficult to maintain a constant reduction rate of the aqueous solution discharged from the reactor. do. In addition, a method of injecting iron materials such as iron pieces or iron ingots into a stirred reactor without using a column reactor may be attempted. However, in the case of using a stirring tank, it is not easy to continuously input iron materials having a irregular shape by a certain amount. In the case of iron, a large amount cannot be added to the agitation tank, and thus the contact area cannot be sufficiently increased. If iron pieces or iron bars are present together with the aqueous solution in the stirring bath, stirring is also not easy.

When reducing the waste iron chloride solution, if there is a lot of unreduced trivalent iron chloride, it is necessary to reduce the trivalent iron chloride to divalent iron chloride in the nickel removal step, thus consuming expensive iron. Meanwhile, when trivalent iron chloride is completely reduced to divalent iron chloride in the reduction step, a reaction in which some nickel ions are precipitated in the iron material occurs. In this case, the nickel deposited on the surface of the steel is dissolved again by the waste iron chloride solution to be added next to increase the content of nickel ions in the aqueous solution. In addition, nickel content is reduced in the nickel removal process, making it difficult to recover nickel.

Therefore, there is a need for a method for reducing waste iron chloride solution capable of maintaining an appropriate reduction rate and enabling continuous operation while using a column reactor filled with iron.

1 is a schematic view of the iron chloride aqueous solution continuous reduction apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

1: column reactor 2: stirred reactor

3: circulation pump

1a: Control valve controlled by level indicator

2a: regulating valve controlled by redox potential control system

In the present invention, a column reactor (1) filled with iron material into which an aqueous waste iron chloride solution is introduced, and iron chloride solution discharged from the column reactor are introduced, and a level indication control system (LIC) and a redox potential control system (AIC) are introduced. It comprises a stirred reactor (2) and a circulation pump (3) for circulating the iron chloride aqueous solution of the stirred reactor to the column reactor, the level indicator control system (LIC) is measured by measuring the height of the iron chloride aqueous solution in the stirred reactor The flow rate of the waste iron chloride solution introduced into the column reactor is controlled, and the redox potential control system (AIC) controls the flow rate of the iron chloride solution discharged from the stirred reactor by measuring the redox potential of the aqueous iron chloride solution in the stirred reactor. It provides a continuous reduction device of the aqueous iron chloride solution.

Here, the total content of ferrous chloride and ferric chloride in the waste iron chloride solution supplied to the column reactor is preferably 45% or less, and the ferric chloride concentration is 40% or less. In addition, the nickel ion concentration of the waste iron chloride solution supplied to the column reactor is preferably 3% or less. In addition, when the redox potential value of the ferric chloride solution corresponding to the concentration of ferric chloride in the aqueous solution of iron chloride is 0.5 to 3% is measured by the redox potential indicator control system, the aqueous solution of iron chloride is preferably discharged from the stirring reactor.

The configuration of the present invention is composed of a conventional column reactor, a conventional stirred reactor and a circulation pump as shown in FIG. 1 and equipped with a redox potential indicator (AIC: Analysis Indicating Controller) to continuously measure the reduction rate. . The column reactor is filled with iron scraps such as iron strips and iron bars, and a waste iron chloride solution is supplied thereto to cause a reduction reaction.

Referring to the configuration of the present invention by the flow chart shown in Figure 1 as follows.

(A) Continuously introducing the waste iron chloride solution and the iron chloride solution circulated through the column reactor and the stirring reactor into the column reactor (1) filled with iron material, and b) The iron chloride solution discharged from the column reactor (1) is stirred. And (c) circulating the iron chloride solution in the stirred reactor (2) to the column reactor (1) using a circulation pump (3) and measuring the concentration of trivalent iron chloride in the redox potential control system (AIC). It is composed of a step of continuously flowing out the iron chloride solution reduced to the appropriate concentration to the next step.

In the present invention, the iron chloride solution discharged from the column reactor is added to the stirring reactor to mix the solution, and the iron chloride solution is circulated in the column reactor so that the iron and the aqueous solution are sufficiently in contact with each other. In addition, the concentration of trivalent iron chloride in the aqueous solution of iron chloride discharged from the stirred reactor was continuously measured so that the concentration of ferric chloride in the discharged iron chloride solution was 0.3 to 5% by weight, thereby maintaining an appropriate reduction rate of 94 to 99%. will be. As the liquid height of the stirred reactor changes according to the amount of outflow from the stirred reactor to the next process, it is measured by a Level Indicating Controller (LIC) and the amount of waste etching liquid supplied to the column reactor is controlled.

To implement the present invention, the relationship between the trivalent iron chloride concentration and the redox potential of an aqueous solution measured using a redox potential is shown in the following table. It is the redox potential (ORP) according to the reduction rate or the concentration of trivalent iron chloride when reducing the trivalent iron chloride 32 wt.% Aqueous solution (divalent iron chloride 0 wt.%). Here, the reduction rate is a value calculated as follows.

Reduction rate and redox potential (80 ℃) Ferric Chloride Concentration (wt.%) Reduction Rate (wt.%) Redox potential (ORP, mV) 31.6 0.0 752.3 27.4 13.3 579.3 23.6 25.3 552.6 19.6 38.0 534.9 15.5 50.9 519.5 11.8 62.7 501.4 7.9 75.0 485.0 4.0 87.3 456.5 0.0 100.0 349.7

As shown in the table, ORP changes from 457mV to 350mV in the process of reducing trivalent ferric chloride from 4% to 0%, so it can be seen that the reduction end point can be accurately identified using the redox potential value. That is, the trivalent iron chloride concentration can be adjusted in the range of 0-4%, and it is possible to reduce the trivalent iron chloride to divalent as much as possible using inexpensive iron while minimizing the precipitation of nickel in the reduction step.

Through the following examples will be described in detail the effect of the present invention is not limited to the scope of the present invention by the following examples.

Example 1

In order to fill the steel, a 0.9 m ³ sized FRP (fiber reinforced plastic) column reactor with a diameter of 9 cm and a height of 150 cm was used, and a 1.5 m ³ sized diameter (110 cm, 160 cm high) agitator was also used. .

As the iron material, scrap generated during the manufacture of a shadow mask of pure iron was used, and the column reactor was filled with an amount that can be used for 10 hours by cutting the amorphous form without distinguishing the perforated and non-perforated parts. The composition of the waste iron chloride etching solution supplied to the reduction reaction was 34% ferric chloride, 9% ferric chloride, and 11,000 ppm nickel ion. The reaction was started after filling 1.2m ³ of the stirring tank. The stirring speed of the agitator tank was 100 rpm to allow the liquid to be sufficiently mixed. The flow rate of the pump for circulating the reaction liquid of the agitator tank to the column reactor was operated to 50 liters per minute, and the liquid discharged from the column reactor was increased in the column reactor. It was to be naturally transported to the stirred reactor in a constant state.

At the beginning of the reaction, the temperature of the liquid discharged from the column reactor by the heat of reaction increased from room temperature to 83 ° C., but after 5 hours, the temperature was maintained at 75 ° C. A plate type heat exchanger was installed in the line circulated to the column reactor in the stirred reactor to maintain the temperature of the reaction liquid in the column reactor to around 80 ° C. After 5 hours, the redox potential of the ferric chloride solution in the stirred reactor was about 410 mV and the ferric chloride concentration was 2.5%-2.0%.

At this time, the waste iron chloride solution was supplied to the column reactor at a flow rate of 4 liters per minute. When the iron chloride solution was discharged to maintain the liquid level of the stirred reactor, the ORP of the iron chloride solution in the stirred reactor was maintained at 415-420mV for 6 hours, and the ferric chloride concentration of the reduced iron chloride solution discharged from the stirred reactor was 2.2-2.5%. Was maintained.

Example 2

As in Example 1, when the redox potential of the iron chloride solution in the stirred reactor reached about 410 mV, the flow rate of the waste iron chloride solution supplied to the column reactor was maintained at 3 liters per minute. The redox potential of the ferric chloride solution in the stirred reactor was maintained at 385-400 mV for 6 hours, and the ferric chloride concentration of the reduced aqueous iron chloride solution was 1.0-1.3%. Meanwhile, the nickel content decreased from 11,000 ppm to 9,950 ppm.

Comparative Example 1

As in Example 1, when the redox potential of the iron chloride solution in the stirred reactor became about 410 mV, the flow rate of the waste iron chloride solution supplied to the column reactor was maintained at 2 liters per minute. The redox potential of the ferric chloride solution in the stirred reactor was maintained at 350-360 mV for 4 hours, but gradually increased to 420 mV after 8 hours. The ferric chloride concentration of the reduced aqueous iron chloride solution discharged from the stirred reactor also increased from 0.5% to 3%. Meanwhile, the nickel content decreased to 8,300ppm after the first 4 hours, but gradually increased to 12,500ppm after 8 hours.

The effect of the present invention is to provide an easy method of continuously reducing trivalent iron chloride to divalent iron chloride in a waste iron chloride solution by using iron materials such as inexpensive iron pieces, iron bars and iron scraps. The iron chloride solution is circulated to the column reactor filled with iron to allow sufficient contact with the iron without stirring, and if necessary, it is easy to control the reaction rate by controlling the temperature of the circulated iron chloride solution.

Claims (4)

A column reactor (1) filled with iron material into which an aqueous waste iron chloride solution is introduced, A stirred reactor (2) into which the iron chloride solution discharged from the column reactor is introduced, comprising a level indication control system (LIC) and a redox potential control system (AIC); A circulation pump (3) for circulating the aqueous iron chloride solution of the stirred reactor to the column reactor, The level indicating control system (LIC) measures the height of the aqueous iron chloride solution in the stirred reactor to control the flow rate of the waste iron chloride solution introduced into the column reactor, the redox potential control system (AIC) of the aqueous solution of iron chloride in the stirred reactor Measuring a redox potential to control the flow rate of the iron chloride aqueous solution discharged from the stirred reactor characterized in that the continuous reduction device of the aqueous iron chloride solution. The apparatus of claim 1, wherein the total content of ferrous chloride and ferric chloride in the spent iron chloride solution supplied to the column reactor is 45% or less, and the ferric chloride concentration is 40% or less. 2. The continuous reduction apparatus of aqueous iron chloride solution according to claim 1, wherein the nickel ion concentration of the aqueous waste iron chloride solution supplied to the column reactor is 3% or less. The iron chloride solution is discharged from the stirring reactor when the redox potential value of the ferric chloride solution corresponding to the concentration of ferric chloride in the aqueous solution of iron chloride is 0.5 to 3% by the redox potential control system. Continuous reduction apparatus of the aqueous solution of iron chloride.