KR101088901B1 - Manufacturing method of polysilicone using silica recovered from slag - Google Patents

Abstract

The present invention relates to a method for producing polysilicon, and more particularly, to a method for producing polysilicon based on silica recovered from slag generated in a steelmaking process.

The present invention includes a first step of recovering silica from the slag generated in the steelmaking process, and a second step of reducing the silica to form metal silicon.

As described above, according to the method for producing polysilicon using silica recovered from the slag of the present invention, high value can be created through slag by recycling the silica recovered from the slag generated in the steelmaking process as a raw material of a semiconductor or a solar cell. have.

Solar Cell, Semiconductor, Polysilicon, Slag, Metal Silicon, Trichlorosilane, Monosilane

Description

Manufacturing method of polysilicone using silica recovered from slag

The present invention relates to a method for producing polysilicon, and more particularly, to a method for producing polysilicon based on silica recovered from slag generated in a steelmaking process.

The steel industry consumes large quantities of raw materials and energy to produce steel, as well as through complex connection production systems such as raw materials, steelmaking, steelmaking, and rolling, producing a large amount of various by-products and wastes.

These by-products and waste account for 65% of the main product, steel. About 80% of the solid by-products and waste are slag, and the remainder is in the form of dust or sludge.

In general, slag generated in steelworks is divided into blast furnace slag generated in the blast furnace process and steel slag generated in the steelmaking process. In addition, there is a pretreatment slag generated in the pretreatment process of steelmaking, slag generated during the oxidation and reduction of the electric furnace, refining furnace slag of the stainless steel making process.

The blast furnace slag melts iron ore, coke and limestone in the blast furnace, and the molten slag is generated by dissolving the mineral component together with the molten iron at about 1500 ℃. Molten slag is separated from water using the difference in specific gravity. The molten slag is classified into palletized slag-air cooled and granulated slag-water cooled according to the cooling method. And steelmaking slag is produced in the process of removing carbon and silicon components dissolved in iron to make steel from iron.

The main components of these slags are composed of CaO, SiO ₂ and are recycled as cement raw materials, concrete product raw materials, road furnace materials, landfill materials, loading materials, etc. according to the particle properties and characteristics of the slag.

However, as described above, so far, the value added of the slag is recycled. In order to use it as roadbed, it is necessary to leave a certain period of time in order to prevent expansion or pretreatment process with water vapor, etc., which leads to many restrictions on recycling. In addition, even when used as a raw material for cement, it is expensive to atomize it, and also the burden of logistics costs is not enough, which is an obstacle to the smooth utilization of slag.

As such, one of the most fundamental reasons that slag has many difficulties and problems in its use is that its use and method are simple and passive, so that they can only be used as low-value materials. In the case of blast furnace slag, most of them are rarely applied to generate special treatment technology or added value, and most of them are recycled only as cement raw materials by very simple physical processing.

On the other hand, polysilicon (polysilicon) is a compound having a high purity polycrystalline molecular structure, it is made by purifying quartz or sand. Polysilicon having a purity of 6N (99.9999%) or more is used as a raw material (SoG-Si) of a solar cell substrate, and polysilicon having a purity of 9N or more is used as a single crystal raw material (EG-Si) for semiconductor wafer manufacturing. Polysilicon manufacturing industry is directly related to industries such as fine chemicals / materials, optical communication, and organosilicon in addition to semiconductor and solar power generation.

The demand for polysilicon is increasing rapidly due to the rapid development of the information and communication industry, the depletion of petroleum energy, and the use of solar energy for preventing global warming.

As of 2006, the global polysilicon market size was 45,000 tons, while its production capacity was 35,000 tons and the supply was insufficient. The polysilicon market is expected to grow at an average annual rate of 12-20%, and 80,000 in 2010. It is expected to reach t scale.

The share of solar cells in polysilicon production is expected to rise from 29% in 2005 to 40% in 2007 and 69% in 2010. In addition, due to the rapid development of the photovoltaic industry, the shortage of polysilicon is expected to intensify worldwide. As a result, the price of silicon raw materials is rising. Therefore, efforts to secure smooth supply and demand of silicon raw materials have emerged as an issue in related industries.

The present invention has been made to improve the above problems, and provides a method for producing polysilicon that can create high added value through slag by recycling the silica recovered from the slag generated in the steelmaking process as a raw material of a semiconductor or a solar cell. Its purpose is to.

Method for producing polysilicon using the silica recovered from the slag of the present invention for achieving the above object comprises a first step of recovering silica from the slag generated in the steelmaking or steelmaking process; And a second step of reducing the silica to form metal silicon.

In the first step, the slag is characterized in that the blast furnace slag or nickel slag.

In the first step, the silica is characterized in that the slag is mixed with an acid solution and reacted, and then recovered by filtration.

The acid solution is a nitric acid solution of 60%, the first step is characterized in that the reaction mixture by mixing 2.5 to 50 times the nitric acid solution in weight ratio with respect to the slag.

The acid solution is 30% aqueous hydrochloric acid solution, the first step is characterized in that the reaction by mixing the aqueous hydrochloric acid solution of 3 to 100 times by weight ratio with respect to the slag.

The acid solution is an aqueous solution of hydrochloric acid and an aqueous solution of nitric acid. The first step is characterized in that the slag is mixed with the aqueous solution of hydrochloric acid for the first reaction and further mixed with the aqueous solution of nitric acid for the second reaction.

After performing the second step, the third step of reacting the metal silicon with hydrogen chloride and then purified to form a trichlorosilane; further comprising a.

After performing the second step, the third step of reacting the metal silicon with silicon tetrachloride and hydrogen and then purified to form a trichlorosilane; further comprising a.

It characterized in that it further comprises; a fourth step of forming the trichloride silane to monosilane by an inhomogeneous reaction.

And a fourth step of depositing silicon from the trichlorosilane.

The silicon of the fourth step is characterized in that the trichlorosilane is added to the inside of the reactor and reduced by precipitation in a hydrogen atmosphere.

As described above, according to the method for producing polysilicon using silica recovered from the slag of the present invention, the silica recovered from the slag is removed from the conventional slag recycling field having a very low added value because it is mostly recycled to cement raw materials by simple physical processing. By using it as a raw material for semiconductors or solar cells, high added value can be created through slag.

In addition, in general, silica is obtained through a complex purification process from quartz or sand to manufacture polysilicon for semiconductors or solar cells, and the present invention recovers silica having a purity of 98% or more by a simple process of crushing slag and acid treatment. The invention is very useful industrially.

In addition, polysilicon may be manufactured using silica recovered from slag of polysilicon, which is mostly dependent on import, and thus import substitution effect of raw materials is very large. In addition, in line with the rapidly increasing demand for polysilicon, it is possible to stably supply domestically using inexpensive raw materials, which can greatly enhance the international competitiveness of domestic companies or Korea.

Hereinafter, a method of manufacturing polysilicon according to a preferred embodiment of the present invention with reference to the accompanying drawings will be described in detail.

1 is a block diagram schematically illustrating a method for producing polysilicon using silica recovered from slag according to a preferred embodiment of the present invention.

The present invention provides a method for producing polysilicon using the silica recovered from the slag rotor as a raw material so that the slag generated in the steel mill can be recycled in the field of semiconductors and solar cells with high added value.

Referring to Figure 1, the slag used in the present invention uses the slag generated in the steelmaking process or steelmaking process of the steel mill. Specifically, blast furnace slag and steelmaking slag may be used as slag. In addition, pre-processing slag generated during the pretreatment process of steelmaking, slag generated during oxidation and reduction of the electric furnace, slag generated in the stainless steelmaking process, etc. may be used.

Preferably, blast furnace slag having a high content of silica is used. While melting ore, coke and limestone in the blast furnace, the molten slag is generated by dissolving the mineral component together with the molten iron at about 1500 ° C. The molten slag is separated from the molten slag by using the difference in specific gravity. The slag-air cooled is gradually cooled in air according to the cooling method and the granulated slag-water cooled by spraying water. Are distinguished.

Among them, the reclaimed slag is about 32 to 34% of the silica content, which is higher than that of the aggregated slag, which is about 11 to 15%. Therefore, it is particularly preferable to use handmade slag as slag in the present invention.

The slag used in the present invention was used for the slag discharged from Gwangyang Works, the composition thereof is shown in Table 1.

SiO ₂ CaO Fe ₂ O ₃ Al ₂ O ₃ MgO P ₂ O ₅ TiO ₂ Zn 33.45 wt% 41.07 wt% 0.55 wt% 13.62 wt% 6.78 wt% 0.01 wt% 0.62 wt% 0.002 wt%

The slag used in the present invention may use nickel slag in addition to the blast furnace slag. For example, in the manufacture of ferronickel, nickel slag generated during melt reduction of an electric furnace may be used. The nickel slag has a high silica content of about 52 to 55 wt% compared to the blast furnace slag, as well as a small amount of impurities to recover high purity silica.

The composition of the reclaimed slag discharged from Gwangyang Ferronickel plant is shown in Table 2 below.

SiO ₂ MgO Fe Al ₂ O ₃ CaO 53.45 wt% 35.50 wt% 4.50 wt% 1.45 wt% 0.65 wt%

In the present invention, to recover the silica from the slag containing silica as an example to recover the silica by reacting the slag with an acid solution. In this case, other metals except silica in the slag react with acid to dissolve and exist in the form of metal salt, but silica does not dissolve in acid but precipitates and exists in solid form.

As the acid solution, an aqueous solution of nitric acid (HNO ₃ ), sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), phosphoric acid (H ₃ PO ₄ ), or the like may be used. The reaction formula of slag and various acids is as follows.

Slag (Si, Ca, Al, Mg ...) + HNO ₃ → SiO ₂ ↓ + M (NO ₃ ) n, M = Ca, Al, Mg ...

Slag (Si, Ca, Al, Mg ...) + HCl → SiO ₂ ↓ + M (Cl) n, M = Ca, Al, Mg ...

Slag (Si, Ca, Al, Mg ...) + H ₂ SO ₄ → SiO ₂ ↓ + M (SO ₄ ) n, M = Ca, Al, Mg ...

Slag (Si, Ca, Al, Mg ...) + H ₃ PO ₄ → SiO ₂ ↓ + M (PO ₄ ) n, M = Ca, Al, Mg ...

In the reaction with acid, the slag is pulverized to an appropriate size for rapid reaction and used for micronization. If the particle size is too large, the reaction rate is low and the reaction time is long, which is inefficient in terms of productivity. If the particle size is too small, micronization is difficult and costs are increased. Therefore, slag powder having a size of approximately 20 to 100 mesh particles is used.

It is preferable to use 60% aqueous nitric acid solution or 30% aqueous hydrochloric acid solution as the acid solution. When the nitric acid concentration is less than 60% or the hydrochloric acid concentration is less than 30%, the reaction rate is slow or hardly occurs. In particular, the aqueous nitric acid solution is preferably 2.5 to 50 times with respect to the slag in a weight ratio to react with the slag. When the amount of the nitric acid solution is less than 2.5 times, the gelation occurs due to the precipitation of calcium nitrate, so that stirring and reaction are not performed well. And when more than 50 times, there is a problem that the recovery of silica is difficult. And when the nitric acid concentration exceeds 60%, the mixed amount can be reacted at 2.5 times or less. For example, in the case of 60% aqueous nitric acid solution, about 2.0 times of the slag weight may be mixed.

And in the case of aqueous hydrochloric acid solution it is preferable to react with the slag by mixing 3 to 100 times with respect to the slag by weight ratio. This is because when the amount of aqueous hydrochloric acid solution is less than 2.5 times, gelation occurs due to precipitation of calcium chloride, so that stirring and reaction are not performed well. And when more than 50 times, there is a problem that the recovery of silica is difficult.

As the acid solution, an aqueous hydrochloric acid solution and an aqueous nitric acid solution can be used together. In this case, firstly, the aqueous hydrochloric acid solution is mixed with slag and subjected to the first reaction, followed by further mixing the aqueous nitric acid solution with the secondary reaction. As described above, when the slag and hydrochloric acid are first reacted and the pretreatment is not completed, a large amount of calcium remains. Therefore, in order to recover high purity silica, post-treatment by adding nitric acid is required. The purity of the silica may be increased by dissolving remaining impurities other than silica by reaction with nitric acid. In addition, it is an environmentally friendly process because it can reduce the generation of nitrogen oxides relative to the reaction with only nitric acid. This is because only fume is generated during hydrochloric acid treatment. In addition, since hydrochloric acid is cheaper than nitric acid, an economical process can be achieved by reducing the amount of nitric acid used.

When the reaction of slag and acid is terminated, the precipitated solid silica is separated from the solution containing the metal salt by using a filter. Filtration can separate silica from solution using various solid-liquid separators such as pressure filters, centrifuges, belt presses and fibrous filters. In addition, it can be easily filtered using filter paper.

The separated silica is washed with deionized water. As the deionized water, distilled water or the like can be used. The washed silica is dried. In this case, the filtration process may be further processed before drying.

As described above, the silica recovered from the slag is very high and separated into 98% or more purity, and the average particle size shows 30 to 50 μm. It has sufficient quality that can be used as a raw material of polysilicon used in semiconductors or solar cells.

The silica recovered from the slag is reduced to metal silicon. For example, the recovered silica is obtained by reacting the recovered silica in a high temperature furnace using an arc discharge or an electron beam under a carbon atmosphere to reduce the silica. The reaction at this time is as follows.

SiO ₂ + C → Si + CO ₂

Metallurgical grade silicon produced as described above has a purity of about 95%. In addition, silica can be reduced using magnesium to obtain metal silicon (SiO ₂ + 2Mg → Si + 2MgO).

The metal silicon needs to be purified to high purity silicon by removing various impurities contained in the metal silicon in order to have a purity of 5N (Si 99.999%) required for solar cells or 9N or more required for semiconductors.

Various methods may be used to purify metal silicon into high purity silicon.

For example, polysilicon of high purity may be prepared by reacting metal silicon with hydrogen chloride gas in a fluidized bed reactor to trichlorosilane and then hydrogen reduction or pyrolysis in a vertical reactor.

In order to convert the metal silicon into trichlorosilane (SiHCl ₃ ), the fluidized bed reactor was filled with metal silicon, and then the temperature of the reactor was raised to about 200 to 400 ° C., and then hydrogen chloride gas was supplied. Trichlorosilane is produced.

Si + 3HCl → SiHCl ₃ + H ₂

The trichlorosilane is produced by the above reaction, but in addition to the reaction, silicon tetrachloride (SiCl ₄ ), dichlorosilane (SiH ₂ Cl ₂ ) or monochlorosilane (SiH ₃ Cl) may be partially produced. In addition, impurities such as Al, Fe, Cu, Ca, B, and P included in the metal silicon may also be generated in the form of metal chlorides (AlCl ₃ , FeCl ₃ , BCl _3, etc.) by reacting with hydrogen chloride.

In this case, the metals included as impurities may act as a catalyst of the hydrogen chloride reaction to speed up the reaction rate. If necessary, 3 to 6 wt% of Cu may be used as a catalyst.

Hydrogen generated in the hydrogen chloride reaction is preferably stored separately and used as a reducing gas in a silicon precipitation process to be described later. In addition, the hydrogen chloride used as a reactant in the reaction has the advantage that can be recycled in the silicon precipitation process to be described later.

The trichlorosilane produced by the reaction is subjected to a purification process to enhance impurities generated by side reactions in order to increase the purity.

The gas discharged from the reactor during the refining process is discharged through a dust filter. The discharged gas is then condensed by cooling to precipitate and separate the metal chlorides. The condensed liquid mixture removes other impurities through a distillation process to obtain high purity trichlorosilane. In addition, the purification process may be purified by a conventional purification process for making silicon for semiconductors or solar cells.

Hydrogenation is used as another method to convert metalsilicon to trichlorosilane (SiHCl ₃ ).

 When the metal bed is charged to the fluidized bed reactor for the hydrogenation reaction and then silicon tetrachloride and hydrogen are simultaneously supplied to the inside of the reactor, trichlorosilane is produced by the hydrogenation reaction as follows.

3SiCl ₄ + 2H ₂ + Si → 4SiHCl ₃ + H ₂

The hydrogenation reaction is an endothermic reaction, the reaction temperature is high to 400 to 700 ℃ it is preferable to use a fluidized bed reactor to maintain the surface area and effective reaction temperature. In addition, the hydrogen generated in the reaction has the advantage that can be recycled to the hydrogen used as a reducing gas in the silicon precipitation process to be described later.

The high-purity trichlorosilane produced as described above is made of polysilicon using a conventional Siemens method or a method of precipitation in a fluidized bed reactor (FBR).

For example, the purified high-purity trichlorosilane and hydrogen gas may be reduced in a bellows reactor equipped with a silicon rod therein to form polycrystalline silicon. At this time, the reaction of depositing silicon in the reactor is represented by the following reaction formula.

2SiHCl ₃ + 2H ₂ → 2Si + 6HCl

In addition, trichlorosilane can be pyrolyzed to high temperature in the reactor to form polycrystalline silicon.

On the other hand, in order to prepare the polysilicon of the present invention, after converting the trichlorosilane into monosilane (SiH ₄ ) which is easy to reduce and easy to purify, the monosilane may be precipitated by silicon by conventional pyrolysis or hydrogen reduction.

Trichlorosilane is converted to monosilane through disproportionation. In this case, silicon tetrachloride is also produced as a by-product. The mechanism of the disproportionation reaction of trichlorosilane is shown below.

2SiHCl ₃ ↔ SiH ₂ Cl ₂ + SiCl ₄

2SiH ₂ Cl ₂ ↔ SiH ₃ Cl + SiHCl ₃

2SiH ₃ Cl ↔ SiH ₄ + SiH ₂ Cl ₂

In the reaction, dichlorosilane (SiH ₂ Cl ₂ ) and monochlorosilane (SiH ₃ Cl) are formed as intermediates. And the catalyst used in the reaction may be used an ion exchanger in the form of conventional amine-functionalized polystyrene, amine-functionalized inorganic support, organopolysiloxane catalyst.

Meanwhile, in order to purify the metal silicon into silicon of high purity, a metal refining method may be used unlike the above. In the metal refining method, metal silicon is placed in a refining crucible, infused with argon gas or water vapor, and heated to oxidize impurities and remove residues floating on the top to produce high purity silicon (UMG: upgrade metaiiugical grade silicon). The metal refining method has a disadvantage in that an impurity content is higher than that of the above-described polysilicon manufacturing method, but the installation is relatively simple and the manufacturing cost is low.

(Example 1)

The reaction experiment of slag and acid solution was carried out. The blast furnace slag discharged from Gwangyang Works was pulverized in a grinder to select only powders of about 50 mesh particle size. In this case, the composition of the slag is as described in Table 1 above.

Next, the mixture was mixed with an aqueous solution of nitric acid and slag powder in a reaction vessel, followed by stirring for 40 minutes at room temperature. The results are shown in FIGS. 4 to 10.

First, FIG. 4 is a photograph of a 60% nitric acid solution mixed with slag and a weight ratio of 1: 2, and FIG. 5 is a photo of a 60% nitric acid solution mixed with a slag and a weight ratio of 1: 2.5. FIG. 6 is a photograph of a 60% nitric acid solution mixed with slag and a weight ratio of 1: 3, and FIG. 7 is a photograph of a 60% nitric acid solution mixed with a slag and a weight ratio of 1: 8. FIG. 5 is a photograph of 60% nitric acid solution mixed with slag at a weight ratio of 1:10.

In FIG. 4, as shown in the photograph, the reaction hardens like clay from the start of the reaction, and the fume suddenly occurs. However, when mixed in a 1: 2.5 ratio, as shown in FIG. 5, the solution was maintained in a solution state and it was confirmed that the stirring was in a good state. This was the same in FIGS. 6 to 8.

9 and 10 show photographs of 20% nitric acid solution mixed with slag and reacted. In the case of mixing 1: 2 in the slag and the weight ratio, as shown in FIG. 9, the phenomenon of hardening like clay occurred from the start of the reaction. In the case of mixing 1:12 in slag and weight ratio, it was maintained as a liquid phase at the beginning of the reaction and then changed like jelly as time passed.

(Example 2)

In order to find out whether the silica recovered from the slag is commercially available as a raw material for semiconductors or solar cells, component analysis was performed on the silica recovered from the slag.

For the experiment, first, the blast furnace slag discharged from Gwangyang Works was pulverized in a pulverizer to select only powder of about 50 mesh particle size. In this case, the composition of the slag is as described in Table 1 above.

Next, 60% nitric acid solution and the selected slag powder were added to the reaction vessel in a weight ratio of 1: 6, and the reaction was performed while stirring at room temperature for 40 minutes. After the reaction is completed, the vessel is cooled, and the contents in the vessel are separated by a centrifuge to separate solid solution. The separated solid silica particles are washed with distilled water and dried at 125 ° C. in a dryer to remove silica from the water slag. Recovered.

Scanning electron micrograph of the silica recovered from the slag as described above in Figure 2 it can be seen that the average particle size is 30 to 50㎛.

And the results of the component analysis of the silica recovered from the slag is attached to FIG.

Referring to FIG. 3, it was confirmed that the purity of the silica was very high, about 98.873 wt%. In view of the fact that silica for use as a silicon for semiconductors or solar cells is generally obtained by refining quartz or sand to obtain silica having a purity of about 90% or more, the present invention simplifies the process by using silica recovered from slag. It can be seen that high-quality polysilicon for semiconductors and solar cells can be manufactured at a cost. Furthermore, as a result of the analysis, it is possible to remove impurities because it does not contain boron or phosphorus, which is difficult to remove than other impurities in the production of polysilicon.

Although the present invention has been described with reference to the embodiments, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible therefrom.

Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

1 is a block diagram schematically showing a method for producing polysilicon using silica recovered from slag according to a preferred embodiment of the present invention,

2 is a scanning electron micrograph of silica powder recovered from slag,

3 is an analysis report showing the results of the component analysis of the silica recovered from the slag,

Figure 4 is a photograph of the reaction mixture by mixing 60% nitric acid solution in a 1: 2 ratio of slag and weight,

FIG. 5 is a photograph of 60% nitric acid solution mixed with slag and 1: 2.5 in weight ratio for reaction.

FIG. 6 is a photograph of 60% nitric acid solution mixed with slag in a weight ratio of 1: 3 and reacted.

FIG. 7 is a photograph of 60% nitric acid solution reacted with a slag and a weight ratio of 1: 8.

FIG. 8 is a photograph of 60% nitric acid solution mixed with slag at a weight ratio of 1:10 and reacted.

Figure 9 is a photograph of the reaction mixture by mixing the nitric acid solution of 20% in the ratio of slag 1: 2,

FIG. 10 is a photograph of reacting 20% nitric acid solution by mixing 1:12 in slag and weight ratio.

Claims (11)

delete delete delete delete delete delete Recovering silica from slag generated in the steelmaking or steelmaking process; A second step of forming the metal silicon by reducing the silica; And a third step of reacting the metal silicon with hydrogen chloride and then purifying the second step to form trichlorosilane. 2. The method of claim 1, further comprising a silica recovered from the slag. Recovering silica from slag generated in the steelmaking or steelmaking process; A second step of forming the metal silicon by reducing the silica; And performing a second step of reacting the metal silicon with silicon tetrachloride and hydrogen after the second step to purify to form trichlorosilane. 2. The method of manufacturing polysilicon using silica recovered from slag, further comprising: The method of claim 7 or 8, wherein the trichloride silane is formed into monosilane by an inhomogeneous reaction. The method of manufacturing polysilicon using the silica recovered from the slag, characterized in that it further comprises. The method of claim 7 or 8, further comprising the step of precipitating silicon from the trichlorosilane; polysilicon using a silica recovered from the slag, characterized in that it further comprises. The method of claim 10, wherein the silicon of the fourth step is added to the trichloride silane inside the reactor and reduced by precipitation in a hydrogen atmosphere to precipitate polysilicon using the silica recovered from the slag.

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