KR20120075305A - A method for preparing silicone with methane - Google Patents

Abstract

The present invention relates to a method for producing silicon using methane as a reducing agent, and more particularly, to a method for producing silicon having improved productivity of introducing methane into the electric furnace through the bottom and / or side of an electric furnace for producing silicon as a reducing agent. . According to one aspect of the invention, the reducing agent may be from 70% to 100% by weight of carbon source and from 30% to 0% by weight of methane gas, from 55% to 75% by weight of quartzite and the reducing agent (carbon source and methane). Gas) A method for producing silicon by reaction of wollastonite, carbon and methane, wherein 45% to 25% by weight is used. According to the method of the present invention, the rate of silicon production by reduction of silicon dioxide to silicon, specifically, the rate of reduction to silicon, is increased, thus improving the productivity of silicon.

Description

A Method for Preparing Silicone With Methane

The present invention relates to a method for producing silicon using methane as a reducing agent, and more particularly, to a method for producing silicon having improved productivity of introducing methane into the electric furnace through the bottom and / or side of an electric furnace for producing silicon as a reducing agent. .

Silicon is used in electronics, semiconductors, and photovoltaic power generation (eg, solar cells), and the demand for silicon is increasing as the development and utilization of the technology field in which silicon is used.

Solar silicon is generally used to increase the purity by reprocessing the metal silicon produced by the electric furnace method. In order to reduce the manufacturing cost of the silicon, research is being actively conducted for the efficiency of the electric furnace process and reprocessing process. As for the research on the electric furnace, the increase of productivity through the heat recovery part and the management of the yellowing of the electric furnace are intensively studied.

In the silicon manufacturing process using the conventional electric furnace method, silicon has been manufactured by reducing silica ore (SiO ₂ ) using carbon in a high temperature environment by an arc of the electric furnace. In addition, in the conventional electric furnace method, a carbon-thermal process and a submerged arc process are basically used. However, the process takes a long time because the reaction process is carried out in several steps. Therefore, there is a need for a more efficient method for producing silicon.

According to one embodiment of the present invention, there is provided a silicon manufacturing method having improved productivity by improving the production rate of silicon.

According to another embodiment of the present invention, there is provided a method for producing silicon having improved productivity by optimizing a reduction reaction in which a reducing agent is added at a specific point in an electric furnace for producing silicon.

According to one aspect of the invention,

Quartzite, carbon with an amount of less than 70 to 100% by weight of carbon source and more than 30 to 0% by weight of methane gas and from 55 to 75% by weight of quartzite and 45 to 25% by weight of reducing agent (carbon source and methane) Provided is a method for producing silicon by reaction of a source and methane.

According to another aspect of the present invention,

In the method for producing silicon by reacting silica with carbon in an electric furnace,

At least a portion of the bottom and side of the furnace such that there is less than 70-100% by weight of carbon source and more than 30-0% by weight of methane gas and 55-75% by weight of quartzite and 45-25% by weight of reducing agent Methane gas is introduced into the electric furnace through the silicon silica, a carbon source and a method for producing silicon by the reaction of the introduced methane is provided.

Silicon production rate by reduction of silicon to silicon dioxide By a reducing agent to the silicon of the silicon dioxide (SiO ₂₎ of silicon produced raw material silica optical mainly composed of SiO ₂ used in addition to methane, specifically, reduction of a silicon This speeds up and thus increases the productivity of the silicon.

Furthermore, direct injection of SiO and / or SiO ₂ and methane in the reactants inside and / or outside of the cavity by the gas formed in the furnace by introducing methane into the furnace from the bottom and / or side of the furnace By the reduction reaction, the rate of reduction of silicon dioxide into silicon and the productivity of silicon in the silica are markedly improved.

1 is a view schematically showing an electric furnace for producing a general silicon.
2 is a view showing a reaction in which silicon is produced in an electric furnace.

Generally, silicon is produced by reducing silicon dioxide in the silica ore into silicon. Generally, the production of silicon from quartzite is carried out in an electric furnace. In the production of silicon using the silica, the process of reducing the silica, that is, the reaction of removing oxygen from silicon dioxide is the most important. Conventionally, carbon has generally been used as a reducing agent for the reduction of silicon dioxide. In addition, although it may be considered to use hydrogen having a better reactivity with oxygen than carbon as a reducing agent, it is difficult to prepare hydrogen separately and input it into an electric furnace.

Therefore, in the method according to one embodiment of the present invention, methane is used as a reducing agent of silicon dioxide in the silicon production process in which silicon dioxide in the silica is reduced to obtain silicon. That is, since hydrogen has better reactivity with oxygen than carbon, which is a reducing agent used in the related art, the rate of reduction of silicon dioxide to silicon is increased and thus the productivity of silicon is improved. That is, according to the method according to the present invention, silicon dioxide in the silica is reacted with carbon and methane and reduced to silicon. In addition, it is preferable to perform the said reaction in an oxygen free atmosphere. Also, if necessary, hydrogen or carbon monoxide may be optionally added.

Specifically, the methane gas reducing agent may be introduced into the electric furnace from the bottom and / or side of the electric furnace for producing silicon. Preferably it is introduced from the lower surface of the electric furnace. Methane gas, which is introduced to the lower side of the furnace, moves upward through the fine pores between the silica and the carbon source charged in the furnace. As such, the silica ore and methane may be contacted in a large area while moving upwards through the reactants, thus reducing the reaction. Furthermore, the methane gas introduced from the lower surface has the advantage of moving to the upper side without applying a separate pressure. Relatively from the side, methane gas is difficult to reach to the quartzite and carbon sources, and requires extra pressure so that they can be introduced into the furnace.

On the other hand, in the vicinity of the arc generated from the electrode in the electric furnace, silicon dioxide in the silica is partially reduced in a high temperature atmosphere, specifically, a temperature of about 900 ° C. to 2000 ° C., and SiO and CO gas are generated. A cavity is formed around the electrode by the gas formed therein.

Methane gas introduced from the bottom and / or side of the furnace is reduced and reacted directly with SiO and / or SiO ₂ directly at the inside and outside of the cavity, thereby improving silicon productivity. Specifically, methane mainly reacts with SiO inside the cavity to promote the formation of silicon and outside of the cavity mainly reacts with SiO ₂ to induce the formation of SiO. Reduction of silicon dioxide into silicon in the silica is not a simple reaction but a reaction through various intermediate products, but it is difficult to define a clear mechanism of the complex reaction. The starting materials are SiO ₂ and C, the intermediates are SiC and SiO (g) and the final products are Si and CO (g).

Final reaction formula: SiO ₂ + 2C = Si + 2CO (g)

Intermediate Product Scheme

SiO ₂ + C = SiO (g) + CO (g)

SiO ₂ + 3C = SiC + 2CO (g)

SiO (g) + SiC = 2Si + CO (g)

SiO (g) + C = Si + CO (g)

Intermediate reaction when methane is added

SiO ₂ + 3 CH ₄ (g) = SiC + 2CO (g) + 6H ₂ (g)

SiO ₂ + H ₂ (g) = SiO (g) + H ₂ O (g)

The amount of methane gas added may be controlled by measuring mass and heat balance and sulfur. For example, the material involved in the production of silicon in the quartzite is SiO _2, but it is difficult to calculate SiO ₂ in the quartzite, and the reaction does not proceed uniformly in the whole part of the silicate, so the reduction reaction of the silicate in the furnace The amount of methane needed can be determined by calculating the inverse of the amount of unreacted material released in. In addition, the amount of methane can be determined by predicting the degree of reaction from the reaction temperature.

In the method according to one embodiment of the present invention, when methane gas is added to the reaction of wollastonite and carbon, the carbon source and the methane gas as the reducing agent are 70% to 100% by weight of the carbon source (excluding 100% by weight) and Methane gas may be used in an amount of 30 wt% to more than 0 wt% (except when the methane gas content is 0), preferably 70 wt% to 90 wt% of a carbon source and 30 wt% to 10 wt% of methane gas. As long as small amounts of methane are added, the productivity of silicon is improved. However, methane gas is preferably added at least 10% by weight of the carbon source, in view of the cost efficiency by retrofitting the electric furnace for methane addition and increasing productivity by adding methane gas. On the other hand, when the methane gas is added, heat is required for the decomposition reaction of the methane gas, and therefore, the amount of heat in the electric furnace is consumed, thereby lowering the temperature in the electric furnace. Therefore, when a large amount of methane gas is added, the temperature in the electric furnace is lowered due to the endotherm by the methane gas, and thus, the reduction reaction rate of the quartzite in the electric furnace may be lowered. Therefore, it is preferable that methane gas is added at a conventionally added reducing agent, that is, at most 30% by weight of the carbon source. On the other hand, in the present electric furnace, the silica and the reducing agent, that is, the carbon source is reacted by adding 55 to 75% by weight of the silica ore and 45 to 25% by weight of the reducing agent. Therefore, when methane gas is added, 55 wt% to 75 wt% of silica may be added and 45 wt% to 25 wt% of a reducing agent (a sum of a carbon source and methane).

At this time, any material generally known in the art may be used as the carbon source, but is not limited thereto. For example, coal, coke, charcoal, carbon electrode, etc. may be used as the carbon source.

On the other hand, methane gas is decomposed into C and H ₂ in an electric furnace, and C formed by the decomposition of methane is a highly reactive carbon form, and H _{2 is} also involved in the reaction to improve the rate of reduction of silicon dioxide to silicon as a whole. do. Since the decomposition reaction of methane proceeds vigorously at a temperature of 1600 ° C. or higher, it is preferable to inject methane into an area in which the temperature is 1600 ° C. or higher.

SiO production rate of silicon to the silicon dioxide By _2, the main component in addition to methane as the reducing agent to the silicon of the silicon manufacturing raw material for silica dioxide (SiO ₂₎ of the light used for, specifically, and enhance the reduction rate according silicon The productivity of can be improved. In addition, the use of methane gas can reduce the amount of carbon source added conventionally. Even if the amount of carbon source used is reduced, the productivity of silicon can be improved.

Hereinafter, with reference to the drawings will be described in detail an embodiment of the present invention. 1 schematically shows an electric furnace for producing a general silicon. 2 shows the reaction in the electric furnace.

Inside the electric furnace 10 is charged with a silica ore and a carbon source, which is a reactant 11. As the carbon source, but not limited thereto, for example, coal, coke, charcoal, a carbon electrode, or the like can be used. Methane gas is from the bottom of the furnace via the lower porosity plug 13 on which the electrode 12 is located and / or from the side of the furnace via the side wall lance 14 to the interior of the furnace 10. It can be put into.

The arc generated in the electrode 12 causes the interior of the furnace to be heated to a high temperature, for example, between about 900 ° C. and 2000 ° C., at which temperature the reaction of silicon dioxide in the quartzite with carbon and methane by a carbon source As a result, silicon dioxide is reduced to form silicon. The furnace interior is also oxygen free.

At this time, the carbon source and methane gas used as the reducing agent as described above are 70% to 100% by weight (excluding 100% by weight) of carbon source and 30% to 0% by weight of methane gas (methane gas content is 0 ), Preferably from 70% to 90% by weight of carbon source and from 30% to 10% by weight of methane gas. In addition, silica ore and reducing agent may be used in the range of 55% to 75% by weight of quartzite and 45% to 25% by weight of the reducing agent (sum of carbon source and methane).

In the reduction reaction of the silicon dioxide, SiC, SiO, CO, Si and the like are formed. Among them, a cavity is formed around the electrode 12 as shown in FIG. 2 by SiO and CO gas. On the other hand, the methane introduced into the electric furnace through the porous plug 13 in the lower part of the electric furnace moves finely between the silica ore and the carbon source charged in the electric furnace through the pores, and inside the cavity and / or Reacts with SiO and / or SiO ₂ outside the cavity to reduce them to silicon. Methane introduced from the side lance 14 of the electric furnace serves to promote the formation of SiO by a reduction reaction with SiO ₂ at a high ambient temperature in the electric furnace without reaching most of the reaction inside the cavity. However, the methane introduced into the side lance 14 may also reach inside the cavity and react with SiO and / or SiO ₂ .

By using methane as the reducing agent, specifically, the rate of silicon production, specifically the rate of reduction of silicon dioxide in the silica, is achieved by adding methane to the furnace at the bottom and / or side of the furnace to react the silica, carbon and methane. Is faster and the productivity of silicon is increased. In addition, the amount of carbon source used can be reduced.

The method according to the present invention uses methane gas as a reducing agent in the production of silicon by the reaction of conventional silica with ore, unless otherwise mentioned in the present specification. The process according to the invention can be carried out depending on the operating process variables, and this general matter is not particularly limited.

Hereinafter, the present invention will be described in detail through examples.

Example 1

The furnace was charged with 3 tonnes of silica ore, 0.7 tonnes of charcoal, 1.2 tonnes of coke, 0.1 tonnes of carbon electrode, 0.35 tonnes of methane gas and 5 ㎥ of oxygen, and operated by applying electricity to the electrode at 13 kWh / kg. Accordingly, silicon dioxide in the silica was reduced to silicon in charcoal, coke and carbon electrode and methane gas as a carbon source to obtain silicon.

Comparative Example 1

The furnace was charged with 3 tonnes of silica, 0.7 tonnes of charcoal, 1.5 tonnes of coke, 0.1 tonnes of carbon electrode, 0.35 tonnes of methane gas and 5 ㎥ of oxygen, and operated by applying electricity to the electrode at 13 kWh / kg. Accordingly, silicon dioxide in the silica was reduced to silicon by charcoal, coke and carbon electrode rods as carbon sources to obtain silicon.

As described above, by using not only a carbon source but also methane gas for silicon production using silica ore, the use amount of the carbon source was reduced, and silicon was obtained efficiently.

10 ... Furnace 11 ... Reactant (silicite and carbon source)
12 ... electrode 13 ... porous plug
14 ... Lance

Claims (4)

70% to less than 100% by weight of carbon source and 30% to 0% by weight of methane gas, and 55% to 75% by weight of quartzite and 45% to 25% by weight of reducing agent (carbon source and methane gas) as reducing agent Process for the production of silicon by the reaction of quartzite, carbon source and methane in the amount of%. In the method for producing silicon by reacting silica with carbon in an electric furnace,
Used as a reducing agent in a carbon source of less than 70% to 100% by weight and methane gas 30% to more than 0% by weight, 55% to 75% by weight of quartzite and 45% to 25% by weight of reducing agent (carbon source and methane gas) And methane gas is introduced into the electric furnace through at least one of the lower and side surfaces of the electric furnace so as to be%. The method of claim 1 or 2, wherein at least one gas selected from the group consisting of hydrogen and carbon monoxide is further introduced. The method of claim 1, wherein the reaction is performed at a temperature of 900 ° C. to 2000 ° C. 4.

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