KR100348894B1 - Feeding Method of Fe-powder for Removing Ni from the Used Iron-chloride Aqueous Solution - Google Patents

Abstract

The present invention relates to a method for injecting iron in depositing and removing nickel by adding iron (鐵粉) to the waste iron chloride solution containing nickel, and aims to minimize the amount of iron input and the amount of sludge generated.

As the nickel concentration in the spent iron chloride is changed, iron in an amount determined by the following Equation 6 is periodically added.

[Equation 6]

W _Fe / W _L = Δ / [k ' * (ln (C _Ni ^o (1-Δ * t)) + b ' )]

Here, W _Fe / W _L is the amount of iron added per unit volume of waste iron chloride solution, △ is the reaction rate, C _Ni ^o is the initial concentration of nickel, the unit is ppm, the unit of t is time, k ' and b ' is a constant that depends on iron.

Description

Feeding Method of Fe-powder for Removing Ni from the Used Iron-chloride Aqueous Solution

The present invention relates to a method of removing and regenerating nickel in a waste iron chloride solution containing nickel, and more particularly, to a method of adding iron in a method of depositing and removing nickel by adding iron (鐵粉).

The shadow mask used for small-sized TVs and small computer monitors of 25 inches or smaller is made of pure iron, so the iron chloride solution used for etching can be recovered by simply oxidizing with chlorine gas. However, shadow masks used in large-sized TVs larger than 25 inches, high definition television (HDTV), and CRT of large computer monitors are made of iron-nickel alloys (Invar alloy, Alloy-42, etc.). The waste iron chloride solution contains about 1 to 3% of nickel, and the accumulated nickel makes the etching holes uneven and the etching efficiency decreases. Therefore, there is a need for a method for effectively removing nickel from nickel-containing waste iron chloride solution.

The method of removing nickel from waste iron chloride solution includes iron reduction method, ion exchange method, electrolysis method, crystal formation method, etc.However, iron reduction method is used to precipitate and remove nickel having lower ionization tendency than iron by adding iron in excess. It is becoming.

The iron reduction method consists of a first reaction (Scheme 1) in which ferric chloride is reduced to ferrous chloride by adding metal iron, and a second reaction (Scheme 2) in which an excess amount of iron is added to precipitate nickel.

2FeCl ₃ + Fe → 3FeCl ₂

NiCl ₂ + Fe → FeCl ₂ + Ni

Here, the first reaction, the reduction reaction, is a reaction occurring spontaneously at room temperature due to an exothermic reaction, so it is not limited to the type of iron introduced. For example, inexpensive scrap and the like can be used. However, the second nickel removal reaction is not only slow but also inhibits the reaction of nickel precipitated on the surface of the iron, so that the iron in powder form, i.e. iron powder, is used to improve the reaction area. It is essential to use. In general, iron is used three to seven times the theoretical demand is expensive, and various methods have been proposed to minimize the amount used.

For example, Japanese Patent Application Laid-open No. Hei 3-253584 and No. Hei 5-85740 have approached in terms of the form of iron. Japanese Patent Laid-Open No. 3-253584 discloses a method of using iron powder having a particle size of 150 to 350 mesh and a specific surface area of 1 m ² / g or more, and Japanese Patent Laid-Open Publication No. 5-85740 discloses a method of using porous iron powder.

In addition, there is a method of reducing the amount of use by reuse, and there are Japanese Patent Laid-Open Nos. Hei 1-67235, Hei 5-140667, Hei 9-156930 and Hei 8-260166. Japanese Patent Laid-Open No. Hei 1-67235 discloses a method of recovering and reusing a slurry of iron and nickel. Japanese Laid-Open Patent Publication Hei 5-140667 discloses a method of precipitating used iron powder in a reactor and repeatedly using it. In Patent Laid-Open Nos. 9-156930 and 8-260166, the second reaction is composed of multiple steps to remove nickel by increasing the nickel content of the iron slurry by filtration in one step to remove nickel, and filtering the iron slurry having low nickel content in two steps. To use again in a one-step reaction. However, this method has a problem in that the reaction rate is sharply lowered and the iron / nickel slurry pulverization device is added when reused three or more times. In particular, in the case of multi-stage reaction according to nickel concentration, several stirring reactors are required, and it is not economical because a process and apparatus for filtering / separating iron / nickel slurry in each reactor must be added.

In order to improve the problem, a method of regenerating iron / nickel slurry using ultrasonic waves (Korean Patent Application No. 96-35940) has been proposed, but this method also requires a filtration / separation device, and an additional ultrasonic generator is required. There are disadvantages.

In addition, there is a method of dividing the iron powder, there are Japanese Patent Laid-Open No. Hei 5-125562 and Japanese Patent Laid-Open No. Hei 5-263273. In Japanese Patent Laid-Open Publication No. 5-125562, a method of dividing iron into two pieces is presented, but the method of determining the input amount is not specified, and Japanese Patent Laid-Open Publication No. Hei 5-263273 discloses a method of dividing iron into two to four times. The method of filtering and re-nickel slurry is used together.

As described above, in order to minimize the use of iron and to minimize the amount of solid waste generated by the use of excess iron, the optimal method of iron input considering the removal rate of nickel has not yet been proposed. Therefore, in the method of adding iron to remove nickel from the waste iron chloride solution, practical optimization of the amount of iron added, the number of divided doses, and the timing of addition is required.

It is an object of the present invention to provide an efficient iron input method for minimizing the use of expensive iron in the removal of nickel from the waste iron chloride solution containing nickel and maintaining an appropriate reaction rate.

1 shows a change in the concentration of nickel when iron is added to a waste iron chloride solution at one time.

Figure 2 shows a comparison of the concentration change of nickel in the case of the iron in the waste iron chloride solution at the time and in the case of split dosing according to the method of the present invention.

The reaction rate at which nickel is removed by the reaction of [Scheme 2] may be assumed to depend on the amount of iron and nickel concentration. However, it is observed that the reaction rate drops rapidly when nickel is deposited on the iron surface (particle surface and the wall of internal pores in the porous case) by the initial reaction to form a nickel layer. This is because the nickel ions must pass through the nickel layer deposited on the iron surface in order to react with iron, and the iron ions produced by the reaction with the unreacted iron below the nickel layer must pass through the nickel layer and diffuse into the solution. . That is, when nickel ions in the solution react with iron on the surface and the iron surface is covered with the deposited nickel layer, the reaction rate is controlled by the diffusion rate of nickel and iron ions in the nickel layer.

Therefore, the nickel removal reaction can be divided into an initial reaction stage governed by the amount of reactant iron and nickel concentration, and a late reaction stage governed by the diffusion rate of nickel and iron ions in the nickel layer.

This is confirmed by the experiment [FIG. 1]. As a result of a series of experiments, the initial reaction rate holding time maintained at the initial reaction rate (r _ini ) depends on the concentration of nickel and the type and amount of iron added, but the concentration of nickel is 3%. When the amount of the porous iron to be added is 1 to 10 times the nickel equivalent, it was confirmed that it is maintained for about 1 hour.

The inventors of the present invention performed a series of experiments and mathematical operations as follows to optimize the amount of iron input, the number of times of recovery, and the timing of input.

1. Determination of Initial Reaction Rate Formula

First, the initial reaction rate (r _ini ) is a function of the amount of iron input (W _Fe / W _L , where W _Fe and W _L are the amounts of iron and solution, respectively) and the initial nickel concentration (C _Ni ) Can be displayed as:

r _ini = -dC _Ni / dt = f (W _Fe / W _L ) * g (C _Ni )

To determine the functions f (W _Fe / W _L ) and g (C _Ni ), (1) make W _Fe / W _L constant, change the C _Ni , measure the initial reaction rate, and (2) set C _Ni constant The initial reaction rate was measured by changing W _Fe / W _L. The experiment proceeded as follows.

(1) Determination of the function f (W _Fe / W _L )

The initial nickel concentration was constant, and a series of reactions were performed while varying the amount of iron added to the 32% ferrous chloride solution. Iron powder used was porous reduced iron (average specific gravity 2.71, DKP-100 manufactured by Dowa Iron Powder, Japan) having a particle size of 45 to 150 µm (average 75 µm) and a purity of 95% or more. The reaction temperature was maintained at 60 ℃ and stirred at 150rpm.

Experiments in which the initial nickel concentration was kept constant at 10,000 ppm and the W _Fe / W _L was changed from 0.01 to 0.04 (1 to 4 times the molar amount of the initial nickel content), and the initial nickel concentration was kept at 1,000 ppm at constant W _Fe Experiments in which / W _L was changed from 0.001 to 0.01 (1 mole to 10 times mole of initial nickel content), the initial nickel concentration was kept constant at 200 ppm, and W _Fe / W _L was 0.00025 to 0.005 (1 mole of initial nickel content). The initial reaction rate was found to be directly proportional to W _Fe / W _L in the experiment. Therefore, the function f (W _Fe / W _L ) can be expressed as follows.

f (W _Fe / W _L ) = k ₁ * (W _Fe / W _L )

(2) Determination of the function g (C _Ni )

The iron input was made constant, and the reaction was performed while changing the initial nickel concentration. The remaining conditions were the same as in (1).

In the experiment where the initial nickel concentration (C _Ni ) was changed from 200ppm to 10,000ppm while maintaining W _Fe / W _L constant at 0.01, 0.005 and 0.001, the log of concentration It was found to be proportional to the linear equation of the value. This is expressed as an equation.

g (C _Ni ) = k ₂ * (a * lnC _Ni + b)

The substitution rate of Equation 2 and Equation 3 in Equation 1 is expressed as follows.

r _ini = -dC _Ni / dt = k * (W _Fe / W _L ) * (a * lnC _Ni + b)

Where k is k ₁ * k ₂ .

In a series of additional experiments using another porous reduced iron DKPC (average specific gravity 2.15, manufactured by Dowa Iron Powder Co., Ltd.), which has an average particle size of 45 µm and a purity of 95% or more, the values of the constants k, a, and b are different. ] Is maintained.

However, when the iron is added at the same time as described above, the iron surface is covered with the precipitated nickel, so that the nickel removal reaction rate is drastically reduced when the nickel concentration of the solution decreases. Therefore, it is important to keep the removal rate of nickel, that is, the reaction rate constant, by appropriately dividing iron powder. (It is an object of the present invention to provide a suitable method of split supply of iron.) This will be described in detail with reference to [2] as follows.

Concentration curve 1 (same as [Fig. 1]) shows the change in the concentration of nickel when all iron is initially added. The initial reaction rate is fast, but a considerable time is required to reach a commercially required nickel concentration of 100 ppm or less. It can be seen that required.

However, in order to mathematically reach the commercially required nickel concentration in the shortest time while minimizing the iron requirement, the concentration curve 1 should be approached to a straight line (concentration curve 2). It can be seen that it can be achieved by doing.

That is, in order to maintain a constant initial reaction rate throughout the entire process of removing the nickel in [Equation 4] to be maintained at -dC _Ni / dt = △ (constant), to the nickel concentration (C _Ni ) of the solution The iron input amount W _Fe / W _{L according} to the following [Equation 5] is to be adjusted.

W _Fe / W _L = Δ / [k * (a * lnC _Ni + b)]

Since the reaction rate X = C _Ni / C _Ni ^o [Equation 5] can also be expressed as [Equation 6].

W _Fe / W _L = Δ / [k ' * (ln (C _Ni ^o (1-Δ * t)) + b ' )]

Here, W _Fe / W _L is the amount of iron added per unit volume of waste iron chloride solution, △ is the reaction rate, C _Ni ^o is the initial concentration of nickel (ppm), t is the reaction time, k ' and b ' Is a constant that depends on iron. For example, in the case of the above-described DKP-100, k ' = -12.29, b ' = -11.

For example, using Equation 6, for example, DKP-100 is injected every hour with porous iron to reduce the nickel concentration of the waste iron chloride solution with an initial nickel concentration (C _Ni ^o ) of 10,000 ppm to 500 ppm in 6 hours. We can calculate the amount of iron that should be put in every hour.

△ = (10,000-500) / 10,000 / 6 = 0.1583, and the amount of iron added per hour is as follows.

Hours (hr) Nickel concentration of the solution (ppm) W _Fe / W _L (kg / kg) 0 10,000 0.00720 One 8,417 0.00672 2 6,834 0.00593 3 5,251 0.00529 4 3,668 0.00461 5 2,085 0.00384 6 500 -

The total dose of iron is 0.03359 kg per kg of solution, and the initial dose of iron is about 17% lower than the iron requirement of 0.04 kg per kg of solution.

Thus, in the removal of nickel by adding iron to the waste iron chloride solution containing nickel, it can be seen that it is most effective to add the iron determined by Equation 6 as the nickel concentration changes.

Iron may be added every hour as described above, but may be added at an appropriate number of times at any time. If the cycle is very short, ultimately iron may be continuously added.

Mathematical manipulations to this will be readily apparent to those of ordinary skill in the art.

The effect of the present invention will be more evident from the following examples.

<Example 1>

The reactor volume of 1m ³ reactor equipped with a stirrer FRP, iron DKP-100 iron oxide powder (JP Dowa Iron Powder Co., Ltd.), the sample waste iron chloride aqueous solution was made using a 34% ferrous chloride solution of nickel concentration 10,000ppm .

Iron (700 kg * 0.03628 = 25.4 kg) required for 700 kg of waste iron chloride solution was dividedly fed hourly as shown in the above table. The reaction temperature was maintained at 80 ℃ and nickel concentration was analyzed using an atomic absorption spectrometer (AA6200, Shimadzu).

After initiation of the reaction, the nickel concentration became 455 ppm after 6 hours and 25 ppm after 7 hours.

<Example 2>

The experiment was carried out using the same reactor and the same sample as in Example 1.

Iron was used to continuously divide and input. During the first hour, the iron input per minute was changed from 0.091kg to 0.077kg, so that the average dose was 0.084kg per minute, and 5.04 kg of iron needed per hour was added. In addition, iron was continuously added in a similar manner.

After the initiation of the reaction, the nickel concentration became 465 ppm after 6 hours and 15 ppm after 7 hours.

Comparative Example 1

The experiment was carried out using the same reactor and the same sample as in Example 1.

28 kg of iron was added at a time and nickel concentration was measured.

After the initiation of the reaction, the nickel concentration became 490 ppm after 6 hours, 380 ppm after 7 hours, and 300 ppm after 8 hours.

Comparative Example 2

The experiment was carried out using the same reactor and the same sample as in Example 1.

28 kg of iron was divided into 6 equal parts and 4.667kg was added every hour, and nickel concentration was measured.

After the start of the reaction, the nickel concentration became 670 ppm after 6 hours, 350 ppm after 7 hours, and 220 ppm after 8 hours.

According to the present invention, in removing nickel from the waste iron chloride solution by the iron reduction method, it is possible to minimize the amount of iron used and to maintain an appropriate reaction rate, and as a result, to minimize the amount of sludge generated.

In addition, when depositing not only nickel but also a metal having a lower ionization tendency than iron, it may be used as an optimal injection method of iron regardless of the type of iron.

Claims (3)

In the removal of nickel by adding iron to the waste iron chloride solution containing nickel, the amount of iron determined by the following [Equation 6] is added so that the reaction rate of nickel removal is kept constant as the nickel concentration changes. Iron injection method characterized in that. [Equation 6] W _Fe / W _L = Δ / [k ' * (ln (C _Ni ^o (1-Δ * t)) + b ' )] Here, W _Fe / W _L is the amount of iron added per unit volume of the waste iron chloride solution, △ is the reaction rate, C _Ni ^o is the initial concentration of nickel, t is the reaction time, k ' and b ' is a constant . The iron injection method according to claim 1, wherein the amount of iron calculated by Equation 6 is added at an arbitrary time point. The iron input method according to claim 1, wherein the amount of iron calculated by Equation 6 is continuously added.