KR101200185B1 - Method for regenerating nickel sludge occurred in production process of nitrogen trifluoride gas - Google Patents

Abstract

The present invention relates to a method for regenerating nickel sludge generated in the production of nitrogen trifluoride (NF ₃ ) gas. The present invention includes the steps of adding nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas to a pyrolysis furnace to thermally remove and remove acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge; And melting the nickel sludge from which the acidic ammonium fluoride (NH ₄ HF ₂ ) has been removed, and then casting the nickel sludge into a nickel-electrode plate, regeneration of the nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas. Provide a method. According to the present invention, the acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge is effectively removed through thermal decomposition, thereby improving electrical characteristics such as current density and electrical conductivity of the regenerated nickel-electrode plate, and generating amount of nickel sludge. Is minimized to extend life.

Description

Regeneration method of nickel sludge generated in the production of nitrogen trifluoride gas {METHOD FOR REGENERATING NICKEL SLUDGE OCCURRED IN PRODUCTION PROCESS OF NITROGEN TRIFLUORIDE GAS}

The present invention relates to a method for regenerating nickel sludge (Ni Sludge) generated during the production of nitrogen trifluoride (NF ₃ ) gas, more specifically nickel sludge generated in the process of producing nitrogen trifluoride (NF ₃ ) gas. (Ni Sludge) is recycled to the nickel-electrode plate, but by effectively removing impurities contained in the nickel sludge through pyrolysis, the electrical characteristics of the recycled nickel-electrode plate are improved, and the amount of nickel sludge is minimized to extend the life. The present invention relates to a method for regenerating nickel sludge which can be used.

Nitrogen trifluoride gas (hereinafter referred to as "NF ₃ gas") is usefully used as a dry etching agent for semiconductors or as a cleaning gas for CVD apparatuses. Recently, the demand for NF ₃ gas is increasing due to the activation of the semiconductor industry.

In general, NF ₃ gas is prepared by the electrolysis of a molten salt of acidic ammonium fluoride (NH ₄ HF ₂ ) in an electrolytic cell. At this time, the electrolytic cell is provided with electrodes of the positive electrode and the negative electrode, and a diaphragm for dividing the positive electrode and the negative electrode. The diaphragm prevents mixing of anode gas (NF ₃ gas, etc.) generated at the anode and cathode gas (H _2, etc.) generated at the cathode. In the process of producing NF ₃ gas through electrolysis, stability to heat or generated gas must be ensured and the electrode can be used for a long time. In addition, the production rate of NF ₃ gas, which is a target product, should be high and the production rate of by-products should be low.

For example, Korean Patent Laid-Open Publication No. 10-1991-0008172 [Patent Document 1] describes a distance between an anode (or cathode) and a diaphragm, a distance between a bottom of an anode (or cathode) and a bottom of an electrolytic cell, and the like for a generated gas. Techniques aimed at stability and long-term usability have been proposed. And the Republic of Korea Patent No. 10-0742484 [Patent Document 2] and Republic of Korea Patent No. 10-0515412 [Patent Document 3] has a technology for suppressing heat or generated gas by installing a cooling tube or heat exchange means in the electrolytic cell upper plate Presented. In addition, Korean Patent No. 10-0541978 [Patent Document 4] is proposed a technique for increasing the production efficiency of NF ₃ gas through the control of the ratio of HF to NH ₄ F of ammonium fluoride during the electrolysis of molten salt have.

As also shown in the preceding patent documents, nickel plate (Ni Plate) is mainly used as an electrode in the production of NF ₃ gas through molten salt electrolysis. That is, the electrolytic cell is provided with a Ni-electrode plate as an electrode of the positive electrode and the negative electrode. At this time, nickel sludge is generated during electrolysis. The nickel sludge contains a large amount of acidic ammonium fluoride (NH ₄ HF ₂ ) as an impurity together with nickel.

In general, the nickel-electrode plate is used by regenerating the nickel sludge as described above. Specifically, the nickel sludge generated during the electrolysis process is recovered and melted in a high temperature furnace, and then regenerated and used as a nickel-electrode plate through casting.

However, the nickel-electrode plate regenerated by the conventional method as described above has a problem of low electrical characteristics, and a large amount of nickel sludge is generated, thereby shortening the lifespan. Specifically, as described above, the nickel sludge contains a large amount of acidic ammonium fluoride (NH ₄ HF ₂ ). If the nickel sludge is melted and cast directly without any treatment, the acidic ammonium fluoride ( NH ₄ HF ₂ ) is pyrolyzed to generate gas. At this time, a gas pocket hold-up phenomenon occurs due to the gas of the acidic ammonium fluoride (NH ₄ HF ₂ ) that is not able to escape to the surface of the nickel-electrode plate, and the gas collection retention phenomenon causes fine Holes are formed so that the degree of integration of the regenerated Ni-electrode plate is significantly reduced. For this reason, during electrolysis using the regenerated Ni-electrode plate, the electrical characteristics such as current density and electrical conductivity of the Ni-electrode plate are low, and internal cracks are generated by bubbles.

In addition, due to the cracks generated, the Ni-electrode plate is separated and deposited in the form of agglomerates, thereby generating a large amount of nickel sludge and shortening the life of the nickel-electrode plate. Accordingly, nickel sludge produced after electrolysis using a conventionally regenerated Ni-electrode plate is usually 30% or more and has a large amount of generation. For example, when using a regenerated nickel-electrode plate of about 27.5 kg, nickel sludge of about 9.0 kg or more is generated after electrolysis.

Republic of Korea Patent Publication No. 10-1991-0008172 Republic of Korea Patent No. 10-0742484 Republic of Korea Patent No. 10-0515412 Republic of Korea Patent No. 10-0541978

Accordingly, in the present invention, in the regeneration (recycling) of the nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas, by regeneration after removing the acidic ammonium fluoride (NH ₄ HF ₂ ) through a specific treatment, It is an object of the present invention to provide a method for regenerating nickel sludge which can improve the electrical characteristics of the nickel-electrode plate and minimize the amount of nickel sludge to extend its life.

The present invention to achieve the above object,

Adding nickel sludge (Ni Sludge) generated during the production of nitrogen trifluoride (NF ₃ ) gas to a pyrolysis furnace to thermally remove and remove acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge; And

The acidic ammonium fluoride (NH ₄ HF ₂₎ This was removed molten nickel sludge and then, nickel-play of a nickel sludge generated during the preparation of comprising the step of casting the electrode plate, a nitrogen trifluoride (NF ₃₎ gas method To provide.

At this time, the temperature of the pyrolysis furnace is preferably 100 ~ 300 ℃. In addition, the pyrolysis furnace is preferably a rotary type.

According to the present invention, in regenerating nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas, the acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge is effectively removed through pyrolysis, thereby regenerating nickel The electrical characteristics such as current density and electrical conductivity of the electrode plate are improved, and the amount of nickel sludge is minimized, thereby extending the service life.

1 is an exemplary schematic diagram of a pyrolysis apparatus that may be used in the present invention.

Hereinafter, the present invention will be described in detail.

In the present invention, in regenerating nickel sludge (Ni Sludge) generated during the production of nitrogen trifluoride (NF ₃ ) gas into a nickel-electrode plate, acid fluoride through pyrolysis before melting and casting the nickel sludge. Ammonium (NH ₄ HF ₂ ) is decomposed and regenerated.

Specifically, the present invention is a pyrolysis to remove the acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge by injecting nickel sludge generated in the production of nitrogen trifluoride (NF ₃ ) gas into a cracking furnace. And melting / casting the molten nickel sludge from which the acidic ammonium fluoride (NH ₄ HF ₂ ) has been removed, and then casting the nickel sludge into a nickel-electrode plate. More specifically described as follows.

First, in the production of nitrogen trifluoride (NF ₃ ) gas, the nickel sludge generated during the electrolysis process is recovered. Specifically, the nickel sludge in the electrolytic cell is separated and recovered by filtration or the like. Thereafter, the recovered nickel sludge is introduced into a pyrolysis furnace 12 (see FIG. 1) to be cracked. Nickel sludge contains acidic ammonium fluoride (NH ₄ HF ₂ ) in addition to nickel, and the acidic ammonium fluoride (NH ₄ HF ₂ ) is thermally decomposed into a gas by heat. Specifically, acidic ammonium fluoride (NH ₄ HF ₂ ) is thermally decomposed into NH ₄ F gas and HF gas by heat.

At this time, the pyrolysis furnace 12, the acidic ammonium fluoride (NH ₄ HF ₂ ) may be maintained at a temperature at which nickel does not volatilize while pyrolysis. The temperature of the pyrolysis furnace 12 is preferably 100 to 300 ° C. In this case, when the temperature of the pyrolysis furnace 12 is less than 100 ° C., pyrolysis efficiency (removal efficiency) of acidic ammonium fluoride (NH ₄ HF ₂ ) may be lowered. And when the temperature of the pyrolysis furnace 12 exceeds 300 ℃, nickel may be volatilized. In consideration of this point, the temperature of the pyrolysis furnace 12 is 180 to 220 ° C., which is closer to 200 ° C.

Various pyrolysis devices may be used in the pyrolysis process. The pyrolysis apparatus is not limited as long as it includes a pyrolysis furnace 12 that applies heat of an appropriate temperature to the introduced nickel sludge. The pyrolysis device may use, for example, a rotary kiln type device. 1 is an exemplary configuration diagram of a pyrolysis apparatus that may be used in the present invention, showing a schematic configuration diagram of a rotary cologne installation.

Referring to FIG. 1, the pyrolysis apparatus may include a pyrolysis unit 10 and a separation unit 20 installed at a rear end of the pyrolysis unit 10 according to an exemplary embodiment of the present invention. The pyrolysis unit 10 may include a pyrolysis furnace 12 into which nickel sludge is introduced, and heat supply means 16 for supplying heat to the pyrolysis furnace 12.

At this time, the pyrolysis furnace 12 is preferably rotatable, that is, rotatable so that heat is uniformly supplied and the pyrolysis efficiency is good. This pyrolysis furnace 12 may be selected from, for example, a rotary drum or the like. The heat supply means 16 is not limited as long as it can supply heat to the pyrolysis furnace 12. The heat supply means 16 may be selected from, for example, a heating wire that generates heat by electricity, a burner that generates heat by fossil fuels (gasoline, diesel, kerosene, coal, etc.), and the like. Can be.

In addition, when a burner using fossil fuel is used as the heat supply means 16, the pyrolysis unit 10 further includes a kiln 14 and a stack 18 as shown in FIG. It may include. And the kiln 14 may be installed in a rotary pyrolysis furnace 12 is interpolated form. The stack 18 is installed at the upper end of the kiln 14 to discharge the smoke generated during the combustion of the fossil fuel.

Nitrogen sludge is added to the pyrolysis furnace 12 of the pyrolysis apparatus as described above to thermally decompose. At this time, the acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge is pyrolyzed into NH ₄ F gas and HF gas in the pyrolysis furnace 12. Thereafter, the processed material subjected to the pyrolysis process is supplied to the separation unit 20 to separate and remove the gas in the processed product. Specifically, NH ₄ F gas and HF gas generated through pyrolysis are separated and removed in the separation unit 20 to obtain nickel sludge that is almost pure water.

The separator 20 is not limited. The separation unit 20 may be capable of separating and removing the NH ₄ F gas and the HF gas generated through pyrolysis. The separation unit 20 may be configured as, for example, a vaporization tower separating gas in a natural gravity manner, and the vaporization tower may be multistage. In addition, the NH ₄ F gas and the HF gas separated and removed may be collected and scrubbed, or may be re-synthesized with acidic ammonium fluoride (NH ₄ HF ₂ ) and reused as a molten salt of electrolysis.

According to the present invention, when pre-treating nickel sludge through the above pyrolysis, the acidic ammonium fluoride (NH ₄ HF ₂ ) contained in the nickel sludge is effectively removed, so that the product containing only high purity nickel sludge, that is, almost pure Ni Can be obtained. At this time, the pyrolysis is not particularly limited, but may be, for example, 10 seconds to 5 minutes. The pyrolysis can be carried out more specifically for 20 seconds to 2 minutes, more specifically about 1 minute.

Next, acidic ammonium fluoride (NH ₄ HF ₂ ) is removed through pyrolysis as described above, followed by melting / casting. That is, the nickel sludge from which the acidic ammonium fluoride (NH ₄ HF ₂ ) has been removed is melted, and then regenerated into a nickel-electrode plate through casting.

The melting is not limited as long as it proceeds at a temperature above the melting point of nickel. For example, the melting may be performed at a temperature of 1455 ° C. or higher in a furnace or the like. The melting may be performed at a temperature of 1460 ° C to 1650 ° C, for example, and at a temperature of 1500 ° C to 1600 ° C.

In addition, in the casting, the nickel melt obtained through melting is poured into a casting mold and molded into a nickel-electrode plate having a desired shape and regenerated. At this time, the casting mold may have various shapes and sizes (volumes), which are not particularly limited.

In the nickel-electrode plate regenerated by the method according to the present invention described above, the acidic ammonium fluoride (NH ₄ HF ₂ ) is effectively removed through pyrolysis, so that the amount of gas generated during the melting / casting process is significantly smaller, thereby improving the degree of integration of nickel. Accordingly, the regenerated nickel-electrode plate has excellent electrical characteristics such as current density and electrical conductivity. In particular, during electrolysis, the generation amount of nickel sludge is minimized to have a long service life.

Hereinafter, examples and comparative examples of the present invention will be exemplified. The following examples are provided to illustrate the present invention in order to facilitate understanding of the present invention, and thus the technical scope of the present invention is not limited thereto.

[Example]

Nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas was introduced into a rotary kiln facility as shown in FIG. 1 and pyrolyzed. At this time, the temperature of the pyrolysis furnace 12, that is, the temperature inside the rotary drum of the rotary cologne plant was maintained at 200 ° C. The gaseous material generated through pyrolysis was removed by volatilization, and the nickel sludge in solid content was separated and recovered. Thereafter, the recovered nickel sludge was melted at 1500 ° C., and then poured into a casting mold, thereby regenerating by molding (casting) a 27.5 kg Ni-electrode plate.

The regenerated Ni-electrode plate was then used for electrolysis in a conventional process in an electrolytic cell containing acidic ammonium fluoride (NH ₄ HF ₂ ). After the electrolysis, the weight (generation amount) and the generation rate of the nickel sludge generated in the electrolytic cell were measured, and the results are shown in the following [Table 1]. In this case, in Table 1, the occurrence rate (%) is a value calculated according to Equation 1 below.

[Equation 1]

% Incidence = (weight of nickel sludge produced after electrolysis / weight of regenerated nickel-electrode plate before electrolysis) x 100

[Comparative Example]

Compared with the above example, the Ni-electrode plate was molded (cast) and regenerated in the same manner except that nickel sludge was not pyrolyzed. Specifically, nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas was melted and cast under the same conditions without pyrolysis to regenerate a 27.5 kg Ni-electrode plate. After electrolysis using the regenerated Ni-electrode plate in the same manner as in the above example, the weight (generated amount) and the generation rate of the generated nickel sludge were measured, and the results are shown together in the following [Table 1].

Nickel Sludge Generation Remarks Before electrolysis
Weight of Regenerated Ni-electrode Plate After electrolysis
Nickel sludge generation amount (weight) Incidence Example 27.5 kg 2.75kg 10.0% Comparative example 27.5 kg 9.5 kg 34.5%

As shown in Table 1 above, it can be seen that the generation rate of nickel sludge is remarkably low, when used after regeneration after thermal decomposition treatment according to an embodiment of the present invention. In addition, when the incidence of nickel sludge is low, it can be seen that the Ni-electrode plate can be used for a long time, thereby extending the life.

10: pyrolysis unit 20: separation unit
12: pyrolysis 14: kiln
16 heat supply means 18 stack

Claims (3)

In the production of nitrogen trifluoride (NF ₃ ) gas, a method of regenerating nickel sludge generated by electrolysis and regenerating nickel sludge containing an acidic ammonium fluoride (NH ₄ HF ₂ ) into a nickel-electrode plate To
Charged into the nickel sludge in the pyrolysis furnace, wherein the nickel-acidic ammonium fluoride contained in the sludge (NH ₄ HF ₂₎ a but the thermal decomposition was removed, the thermal decomposition by thermal decomposition for 10 seconds to 5 minutes acidic ammonium fluoride in a (NH ₄ HF ₂ ) removing; And
The acidic ammonium fluoride (NH ₄ HF ₂₎ This was removed molten nickel sludge and then, nickel-comprising the steps of: casting the electrode plate, a nitrogen trifluoride (NF ₃₎ The nickel generated during the production of gas How to recycle sludge
The method of claim 1,
The temperature of the pyrolysis furnace is 100 ~ 300 ℃, characterized in that the regeneration of nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas.
The method according to claim 1 or 2,
The pyrolysis furnace is a rotary, characterized in that the regeneration of nickel sludge generated during the production of nitrogen trifluoride (NF ₃ ) gas.

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