KR101208431B1 - Recycling of Nikel sludge - Google Patents

Abstract

The present invention relates to a method for producing nickel metal products by purifying nickel from sludge generated in a nitrogen trifluoride production method using electrolysis.
According to the present invention, it is possible to efficiently purify nickel from the sludge generated in the nitrogen trifluoride production method using electrolysis to produce a high purity nickel metal product. In addition, as a result, it is possible to recycle the nickel that is thrown away in the form of sludge, not only to reduce the waste of raw materials, but also to effectively solve the environmental pollution problem caused by the discarded nickel sludge.

Description

Recycling of Nikel sludge

The present invention relates to a method for regenerating nickel, and more particularly, to a method for refining nickel from a sludge generated in a nitrogen trifluoride production method using electrolysis to produce a nickel metal product.

Nitrogen trifluoride (NF ₃ ) gas is used to clean dry etchant and CVD equipment in semiconductor manufacturing, as a fuel for rockets, and there is no environmental problem.

The nitrogen trifluoride production method includes a direct fluorination reaction, a plasma method, or an electrolysis method. Of these, the electrolysis method can produce a higher purity product than the other two methods, and the yield is high. It is advantageous for mass production.

Briefly, a method of producing nitrogen trifluoride using electrolysis is generally described by using an electrode made of carbon or nickel inside an electrolytic cell, and as an electrolyte from ammonium fluoride (NH ₄ F) and hydrofluoric acid (HF). KF-NH ₄ F-HF or LiF-NH ₄ F-HF derived by adding potassium fluoride (KF) to the NH ₄ F-HF or NH ₄ F-HF is derived.

Nitrogen trifluoride (NF ₃ ) and nitrogen (N ₂ ) gases are generated at the anode, hydrogen (H ₂ ) is generated at the cathode, and the gas evolution reaction Simultaneously occurring at the poles, the produced nitrogen trifluoride gas is produced separately by collecting it separately.

The reaction at both poles is represented by the following formula (1).

[Formula 1]

^{Anodes: N - + 3F - → NF} 3 + 4e

Cathode: 2H ⁺ + 2e → H ₂

Of NH ₃ N ^- ions and HF of F ^- there is an ion binding to NF ₃ produced, it is at the same time the Ni ⁺ ion of the nickel electrode plate separated from the positive electrode plate moves toward the negative electrode plate, some of which only adhere to the anode part is an electrolytic cell On the floor of the building.

Repeating the process for producing nitrogen trifluoride, a large amount of sludge builds up on the bottom of the electrolytic cell, and the sludge is usually disposed of.

However, this sludge contains a large amount of nickel, and if it can be reused, it can not only save a lot of costs for the manufacturing process but also can be considerably desirable from an environmental point of view.

Accordingly, the present inventors have made diligent research efforts to develop a method for purifying nickel from sludge generated in the process of producing nitrogen trifluoride using electrolysis. After melting and cooling, it was confirmed that the high-purity nickel metal could be recovered, thereby completing the present invention.

Therefore, the main object of the present invention is to provide a method for recovering nickel from sludge generated during the production of nitrogen trifluoride using electrolysis.

According to an aspect of the present invention, the present invention provides a method for purifying nickel from sludge produced during the production process of nitrogen trifluoride (NF ₃ ), characterized by electrolysis of NH ₃ and HF using a nickel electrode as an anode. ,

a) drying the sludge;

b) grinding the dry sludge to obtain a pulverized product;

c) removing impurities of the pulverization with a vacuum dust collector to obtain nickel metal;

d) filtering the pulverized product passed through step c) with a sieve of 50 to 200 mesh to obtain a pulverized product that did not pass through the sieve;

e) melting the ground product obtained in step d) to obtain a melt;

f) provides a nickel regeneration method comprising the step of cooling the solid obtained in step e) to solidify.

According to the method for producing nitrogen trifluoride by electrolysis, a precipitate is formed at the bottom of the electrolytic cell, and when collected, it becomes a sludge, which contains a large amount of nickel.

The present invention relates to a method for purifying nickel from such sludge, which can be roughly divided into drying, grinding, removing impurities and melting.

In order to apply the method of the present invention, it is necessary to remove the water of the sludge. When using sludge in a state of containing water, the grinding step is difficult to be made smoothly, and impurities and moisture are agglomerated, it may be difficult to remove the dust collector. In addition, a large amount of water vapor can be generated during the dissolution process, which is not efficient in operation.

As a method of drying the sludge, a natural drying or an artificial drying method may be used. In order to shorten the process time, it is preferable to use an artificial drying method. It is good to use.

When the sludge is dried in this way, sludge may be relatively easily crushed due to impurities present between the sludges in the crushing step.

It is preferable to use a hammer mill or a roll mill to grind the sludge, and it is preferable to grind it using a hammer mill. It is preferable to grind | pulverize so that the grind | pulverized thing may consist mainly of the particle | grains of about 1 cm-8 mm. In this grinding process, the nickel metal maintains a relatively large lump, and other impurities are pulverized into smaller particles than the nickel metal lump.

After the crushing step, a dust collector is used to remove impurities from the pulverized product. The dust collector is preferably a dust collector that can separate from the pulverized product by using air pressure and suctioning a relatively light substance. It is good to be included. Impurity removal using a pulverizer and a dust collector may be performed separately, and by connecting the pulverizer and the dust collector, the impurity removal by the dust collector may be performed simultaneously with the pulverization. Typically, about 90% of the impurities are removed from the mill during this process.

It is preferable to remove impurities by using a sieve to grind the firstly removed impurities through a dust collector, wherein the sieve used is preferably 50 to 200 mesh, more preferably about 100 mesh. It is good.

When the pulverized material, which is primarily free of impurities, is filtered through a sieve, small particles of impurities are passed through the sieve and relatively large particles of nickel metal remain in the sieve.

If the impurities are removed secondarily using a sieve, then a chunk of nickel metal which has not passed through the sieve is obtained and melted, most of the impurities remaining unremoved are oxidized or vaporized.

By cooling and solidifying the melt obtained in the melting step, it is possible to obtain a high purity nickel metal. In this case, the molten material is poured into a mold having a desired shape to be solidified, subjected to hot working, and then subjected to post-processing such as grinding to produce a nickel metal product of a desired shape. The nickel metal product thus prepared has a purity of about 98%.

In the manufacturing process of the present invention, a gas is generated in the melting step, so that the melting step is performed more efficiently, and in consideration of the working environment and environmental pollution, the fume generated simultaneously with the melting is collected by a dust collector. In addition, it is preferable to remove the harmful gas present in the discharge.

When collecting the gas, it is preferable to use a vacuum dust collector including a filter. Due to the characteristics of the present invention, a large amount of salt (ammonia fluoride salt) is included in the generated gas, and the salt component absorbs moisture in the air. And adhere to and adhere to the surface of the filter. If this phenomenon persists, the filter will be clogged, causing the need for frequent replacement. To prevent this, a method of heating the gas passing through the dust collector or removing moisture from the air may be used. Heating may be achieved by a method using a separate heating device, and water removal may be achieved by spraying a dust absorber such as slaked lime or kaolin to the dust collector. By using this method, the clogging of the filter is reduced, so that gas generated during melting can be collected without changing the filter for a long time.

Since the gas collected by the dust collector contains a large amount of harmful gas, it is necessary to have a separate wet scrubber to remove the harmful gas.

In the nature of the present invention, the collected gas contains a large amount of hydrofluoric acid component. Since hydrofluoric acid corrodes glass, stainless steel and the like, it is preferable to use a wet scrubber composed of a material having hydrofluoric acid resistance. Suitable hydrofluoric acid resistant materials include PVC and the like.

As described above, according to the present invention, high purity nickel metal products can be manufactured by efficiently regenerating nickel from sludge generated in the nitrogen trifluoride production method using electrolysis.

As a result, it is possible to recycle nickel that is thrown away in the form of sludge, thereby reducing waste of raw materials and effectively solving the environmental pollution problem caused by discarded nickel sludge.

1 is a diagram illustrating an embodiment of the present invention, in which black arrows show a path of nickel and white arrows show a path of impurities or gas.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and the scope of the present invention is not to be construed as being limited by these examples.

Example 1.

The sludge used in this embodiment is a sludge generated in the process of producing nitrogen trifluoride by the method of using a nickel metal plate as an anode and electrolyzing NH ₃ and HF, the components of the sludge are shown in Table 1. The sludge is bulky and the size of the large particles is about 10 cm.

ingredient content Nickel Metal 50 to 95% Nickel fluoride 1 to 20% Nickel oxide 1 to 10% Hydrofluoric acid ammonia 1 to 20% moisture 1 to 20% Etc

In order to remove the water of the sludge was used a drying chamber, the drying chamber is ondol type to heat the bottom, it was produced in a way that air is circulated through the fan.

The temperature of the drying chamber was maintained at 20 ~ 60 ℃, humidity below 50%, and the sludge was dried in the drying chamber for 20 to 80 hours.

The dry sludge was pulverized using a hammer-type hammer mill so that the particles of the pulverized product were less than 1 cm, and a small particle diameter and light impurities were firstly removed by a dust collector. At this time, the hammer mill and the dust collector were manufactured by one device (Junheung machine, 30㎥ / min, 50 ~ 150 mmH 2 O) was used.

After removal of the first impurity, the pulverized product was sieved through a sieve of about 100 mesh to obtain a pulverized product that did not pass through the sieve and then heated to melt.

A dust collector (Sewoo ENG Co., Ltd., 200㎥ / min, 50 ~ 150 mmH2O) was installed at the upper part of the melting section to collect the fumes generated during melting, and the collected gas was transferred to a wet scrubber. The gas was allowed to be removed. At this time, the dust collector was heated and the lime was dispersed so that the dust collector and the wet scrubber were used as one device.

The melt obtained through the melting was poured into a mold, cooled and solidified, and then melted and ground to prepare a nickel metal product.

Experimental Example 1

The component content of the nickel metal product prepared in Example 1 was analyzed using a spectrometer (product name: Maxx) manufactured by Spectro, Germany.

The results are shown in Table 2.

Claims (1)

A method of purifying nickel from sludge produced during the production process of nitrogen trifluoride (NF ₃ ), characterized by electrolysis of NH ₃ and HF using a nickel electrode as an anode,
a) drying the sludge to obtain dried sludge;
b) grinding the dried sludge to obtain a pulverized product;
c) removing impurities from the mill by a vacuum dust collector to obtain nickel metal;
d) filtering the pulverized product passed through step c) with a sieve of 50 to 200 mesh to obtain a pulverized product that did not pass through the sieve;
e) melting the ground product obtained in step d) to obtain a melt;
f) cooling the solid obtained in step e) to solidify the nickel.

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