KR101405886B1 - Preparation method of silicone compound prepared from chaff or rice straw - Google Patents

Abstract

The present invention relates to a process for producing a silicon compound produced from rice hulls or rice straw, comprising the steps of milling a rice husk or a rice straw, acid-treating the mixture, mixing the resultant with a reducing agent and then reducing the silicon compound under an inert atmosphere will be.

In this method, a high-purity silicon compound can be obtained from a rice husk or a rice straw by a simple process, and various silicon compounds can be produced by further introduction of other raw material gases. The silicon compound thus produced is applied to solar cells.

Silicone, rice husk, rice straw

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing a silicon compound produced from rice hulls or rice straw,

The present invention relates to a method for producing a silicon compound from a rice husk or rice straw which can obtain a high purity silicon compound through a simple process from rice hulls or rice straw and which is capable of producing various silicon compounds due to the introduction of other raw material gases.

There is growing interest in renewable energy that does not use hydrocarbon fuels to produce low-carbon green growth and does not generate carbon dioxide or other harmless foreign substances. There is much interest in using solar energy as a part of renewable energy to get the energy needed for living.

At the heart of solar technology is solar cells that convert sunlight directly into electricity.

In recent solar cells, photoelectric conversion efficiency reaches up to 25%, which is very high, but the manufacturing cost is high, and the electricity production cost is still very high compared to the conventional power generation cost such as thermal power and water power. Supply is also not smooth.

Accordingly, it is essential to supply the materials and equipment necessary for the construction of the photovoltaic power system in order to develop the market of the newly emerging solar industry and to enhance the competitiveness as alternative energy. In addition, it is necessary to develop new material, process and design technology that can make the conversion efficiency from solar energy to electric energy remarkably, or to make solar cell very cheaply. Especially, cheap and stable supply of silicon for solar battery It must be premise.

Solar cells operate on the same principle as semiconductors, and the typical materials used in their manufacture are also silicon used in semiconductors. However, silicon for semiconductors has a large impurity content, which leads to a reduction in the efficiency of manufacturing solar cells. Since solar cell supply silicon (6N-7N) as a raw material is manufactured using a non-standard product of ultra high purity silicon (11N-12N) for semiconductor or manufactured by the same method as silicon for semiconductor, it is difficult to be.

Silicon in standard commercial processes is produced by performing a thermal carbonization process on a mixture of a carbon source and silica. The purity of the silicon produced is 98% to 99%, which is used as a metal, but is insufficient for 6N (99.9999%) purity used in fields such as semiconductor and photovoltaic industries. In order to produce silicon for solar cell through such a thermal carbonization process, it is necessary to use a raw material of high purity and complicated process is required, which shows an adverse effect of increasing manufacturing cost.

On the other hand, all plants contain silica containing carbon. In particular, the rice husks have a weight ratio of about 90% or more, and rice straw contains about 30% or more of silica, although there is a difference depending on the type of rice, climate, and geographical environment. Therefore, rice husks and rice straws are suitable raw materials for the production of silicon for solar cells, which is attracting attention due to high silica content and low cost.

Hunt et al., LP Hunt, JP Dismukes, JA Amick, "Rice Hulls as a Raw Material for Producing Silicon ", J. Electrochem . Soc., 131 (7), 1984], to provide a sufficiently pure and cost-effective silicon to be produced with solar cells.

Also, rice hulls and rice straw are proposed as raw materials for silicon carbide [RV Krishnarao, et.r., J. Am. Chem. Soc . 74, 2869, 1991).

PCT International Patent Publication No. WO 2005/099893 discloses a process for producing a plant and an acid solution by contacting a plant comprising silica, non-silica minerals and about 3% by weight or more of metal with an aqueous sulfuric acid solution having an acid concentration of from about 0.01% to about 30% And then reacting at a temperature of from about 10 캜 to about 250 캜 for a reaction time of about 6 seconds to about 48 hours to excrete the minerals from the plant so that the molar ratio of fixed carbon to silica is about 1.0: Refers to a process for producing a carbon-silica product, i.e., silicon carbide, that has been adjusted to a desired level.

Korean Patent Laid-Open Publication No. 2006-102605 discloses a method of producing silicon carbide from rice husks and rice straw as raw materials. Specifically, washed and dried rice hulls and rice straw were carbonized at 300 to 600 ° C, respectively, and pulverized to obtain powders having a powder size of 1 mm or less. A mixture of 50 to 80% by weight of rice husks and 20 to 50% The mixture is sintered at 750 to 1,200 ° C for 3 to 13 hours, left at 300 to 600 ° C for 1 to 3 hours, pulverized and selected to produce silicon carbide. However, this process is complicated by several steps including carbonization, sintering, and heat treatment after sintering.

In addition, it has been studied for the use of cement additives using rice hulls and rice straw [Jose James, et . Al . , J. Sci. Ind. Res . 51, 383, 1992).

Korean Patent Laid-Open Publication No. 2001-0096628 discloses porous silica having a bone or pore of 10 nm or less by oxidizing rice hulls or rice straw with an acid treatment and carbonization in an oxygen-free atmosphere, followed by oxidation in an aerobic atmosphere.

As described above, a method of using silica contained in rice husk and rice straw in various fields has been researched and developed. In the present invention, a silicon compound usable for a solar cell can be obtained from the rice hull and rice straw in high purity, A method for producing a silicon-based compound is proposed.

It is an object of the present invention to provide a method for producing a silicon compound capable of directly producing a high purity silicon compound without changing the rice hull or rice straw into a powder and capable of producing various silicon compounds by further introduction of other raw material gases .

In order to achieve the above object,

Milling rice husk or rice straw and acid-treating the same;

Mixing the treated rice hull or rice straw with a reducing agent; And

And performing a reduction reaction at 1000 占 폚 to 2000 占 폚 in an inert atmosphere in the obtained mixture.

At this time, hydrocarbon gas is injected in the reduction reaction in the present invention to produce polycrystalline silicon carbide as a silicon compound.

Further, the present invention further provides an alkali metal hydride gas during the reduction reaction to produce silicon hydride as a silicon compound.

In the present invention, a silicon compound can be directly obtained without converting rice hulls or rice straw into powder, and a high-purity silicon compound is produced through a simple process.

In addition, it is possible to manufacture various silicon compounds due to the introduction of other raw material gases during the manufacturing process.

The silicon compound thus prepared can be used as a silicon for a solar cell, and it is possible to supply cheap and stable silicon through the above method.

Hereinafter, the present invention will be described in more detail.

In the present invention, various kinds of silicon compounds are prepared by reducing rice hulls or rice straw with a reducing agent under an inert atmosphere. The silicon compound is silicon (SiO ₂ ), silicon carbide (SiC), and silicon hydride (SiH ₄ , monosilane), which will be described in detail below with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a method for producing polycrystalline silicon from rice hulls or rice straw. FIG.

Referring to FIG. 1, a pretreatment process is performed in which rice husk or rice straw used as a raw material is milled and subjected to acid treatment to increase the purity of the finally produced silicon.

First, rice husk or rice straw is milled to a certain size and acid treatment is performed.

The milling is performed using a milling machine that is commonly used, such as a nylon milling machine, a bed milling machine, a universal milling machine, an upright milling machine, and the like. Through milling, rice husk or rice straw has a size of 50 to 500 mu m.

The milled raw material is immersed in an acid solution for a predetermined time or sprayed with an acid solution to minimize the content of impurities in the polycrystalline silicon finally obtained.

It dissolves organic components, metal components or impurities contained in rice hulls or rice straw through acid treatment, and it uses 0.1 to 10M strong acid. The strong acid is typically selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof.

The immersing time is appropriately adjusted according to the concentration of acid solution, throughput, etc. For example, it is performed for 10 minutes to 6 hours. The acid treatment may be performed by applying heat when necessary, preferably at 40 to 150 캜, more preferably at 60 to 100 캜. The acid treatment is carried out one or more times, preferably 1 to 10 times. In this case, it is possible to carry out the multistage process by varying the type, concentration and temperature of the acid solution.

Next, the rice husk or rice straw pretreated in the previous step is introduced into a reactor performing reduction, and alkali metal, which is a reducing agent, is added thereto.

Various materials can be used as a reducing agent for reducing rice hulls or rice straw, and alkali metals are preferably used. Typically, one alkali metal selected from the group consisting of sodium, potassium, magnesium, calcium, manganese, iron, boron, aluminum, and combinations thereof is possible.

These alkali metals are used in an amount of 100 g to 120 g per 1 kg of rice hull or rice straw. If the content of the alkali metal is less than the above range, sufficient reduction is not achieved, or the time for reduction is prolonged. If the amount exceeds the above range, the amount of the reducing agent is increased and the amount of impurities increases. .

Next, an inert gas is injected into the reactor to perform the reduction reaction.

The inert atmosphere is formed by injecting argon (Ar), nitrogen (N ₂ ), helium (He) or a mixed gas thereof.

The reduction reaction of rice hull or rice straw using the reducing agent is performed at 1000 ° C to 2000 ° C, preferably at 1000 ° C to 1500 ° C. If the treatment temperature is lower than the above temperature, the reduction reaction is less likely to occur and SiO ₂ remains unreacted. On the contrary, if the temperature is higher than the above temperature, the reduced Si is oxidized again to return to the oxidized form SiO ₂ A problem occurs in which the reaction occurs in an undesired direction.

The reactor used in the reduction reaction can be carried out in a conventional reactor, for example, in a hot electric furnace, an arc furnace, a fluidized bed reactor or a plasma reactor.

The rice and rice straw are carbonized to produce silica and carbon components, and the resulting silica is reduced by alkali metals and carbon to produce polycrystalline silicon. According to the preferred embodiment 1, it is understood that the process of producing silicon from rice hulls is very simple, and it is possible to expect a great economical advantage, and the reaction mechanism is simple and the reaction is easy. According to Fig. 4, it can be seen that the produced silicon has a polycrystal and the purity is 99.95% or more.

In the method according to the present invention, it is possible to produce silicon carbide, silicon hydride, etc. in addition to silicon by adding various raw material gases together with a reducing agent.

2 is a block diagram showing a method for producing silicon carbide from rice hulls or rice straw.

Referring to FIG. 2, silicon carbide is prepared by pretreating rice hulls or rice straw, adding an alkali metal as a reducing agent, and performing a reduction reaction while injecting an inert gas and a hydrocarbon gas.

The hydrocarbon gas is used as a raw material for the carbon (C) of silicon carbide and is preferably selected from the group consisting of methane (CH ₄ ), ethane (CH ₃ CH ₃ ), propane (CH ₃ CH ₂ CH ₃ ) One species selected from the group is available.

The hydrocarbon gas is used in an amount of 5 to 40 cc / min for 1 kg of rice hull or rice straw used as a raw material. If the content of the hydrocarbon gas is less than the above range, generation of silicon carbide is reduced and unreacted silica is present as an impurity. If it exceeds the above range, silicon carbide and other impurities are generated, which is not economical. Therefore, it is properly performed within the above range. These hydrocarbon gases are injected at 5 to 40 cc per minute in the reactor.

Silicon carbide is produced through these steps. According to the second preferred embodiment, the present silicon carbide process is also similar to the silicon manufacturing process, and it can be seen that it is economically advantageous. According to Fig. 5, it can be seen that the produced silicon carbide has a polycrystal and the purity is 99.5% or more.

3 is a block diagram showing a method for producing silicon hydride (SiH ₄ ) from rice hulls or rice straw.

Referring to FIG. 3, the silicon hydride is prepared by pretreating rice hulls or rice straw, adding an alkali metal as a reducing agent, and performing a reduction reaction while injecting an inert gas and an alkali metal hydride gas.

The alkali metal hydride gas is used as a raw material for hydrogen (H) of silicon hydride, and preferably one species selected from the group consisting of calcium hydride (CaH ₂ ), sodium hydride (NaH), and combinations thereof.

The alkali metal hydrate gas is used in an amount of 20 to 60 cc per 1 kg of rice hull or rice straw used as a raw material. If the content of the alkali metal hydride gas is less than the above range, silicon is formed in addition to silicon carbide. If the content of the alkali metal hydride gas is above the range, excess silicon hydride and excess excessive impurities are generated, . This alkali metal hydride gas is injected at a rate of 20 to 60 cc in the reactor.

Silicon hydride is produced through this step. According to the preferred embodiment 3, it can be seen that the silicon hybrid also has a simple process and brings a great economic benefit to the actual process.

Silicon hydrides are currently produced by dismutation of trichlorosilanes (see, for example, German Patent Publication No. 100 17 168 A1, U.S. Patent No. 3 968 199). The silicon hydride thus produced must be subjected to a separate purification step due to the presence of impurities such as dichlorosilane and monochlorosilane. However, according to the present invention, high-purity silicon hydride can be recovered by condensing under economical conditions after the reduction process. Condensation is carried out at a desired pressure for disproportionation, i.e. at a temperature of +50 to -80 DEG C, particularly preferably -50 to 10 DEG C at an absolute pressure of, for example, 5 to 25 bar.

The above-described method can be carried out by simply carrying out a reduction treatment at a high temperature together with a reducing agent to produce various silicones such as silicon, silicon carbide, and silicon hydride. This method is not only simple and economical in the treatment process as compared with the conventional method, but also can be applied to various fields because the final prepared silicon compounds are also highly pure.

The silicon compounds produced by the present invention can be preferably used as silicon for solar cells and have high purity to achieve high photoelectric efficiency. In this way, cheap and stable silicon supply is possible.

Hereinafter, preferred embodiments and experimental examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited by these examples.

Example 1: Production of polycrystalline silicon

Manufacture of polycrystalline silicon

The rice husk and rice straw were mixed at a weight ratio of 1: 1 and then milled to an average particle size of about 138 μm. The milled mixture was immersed in an aqueous 1% sulfuric acid solution, heated at 110 DEG C for 5 hours, washed with distilled water and dried. This procedure was repeated twice.

The dried mixture and Mg were mixed at a weight ratio of 10: 1 and then injected into a tubular furnace using an alumina tube. The furnace was purged with Ar gas and then subjected to a reduction process at 2000 占 폚 for 3 hours to 5 hours.

The obtained polycrystalline silicon was washed with an aqueous sulfuric acid solution and distilled water, respectively, and then dried.

X-ray diffraction analysis

The prepared polycrystalline silicon was measured by an X-ray diffractometer, and the obtained results are shown in FIG.

4 is an X-ray diffraction pattern of the polycrystalline silicon produced in Example 1. Fig. Referring to FIG. 4, only the intrinsic peak of the crystalline silicon is seen, and no peaks of the other impurities are observed, and it can be seen that high purity crystalline silicon is produced.

ICP analysis

ICP analysis was performed to confirm the impurities in the prepared polycrystalline silicon, and the obtained results are shown in Table 1 below. Referring to Table 1, it can be seen that the content of impurities is less than 0.1% and the purity of silicon is 99.9% or more.

element Content (ppb) element Content (ppb) Al 492,744 P 18,608 B 8,544 Ti 151,973 Cr 30,249 V 1,228 Cu 11.70 Zr 92,676 Fe 999,773 Ca 491,383 Mn 361,678 Mo 3,646 Ni 0.008 Na 46,803 Co 553 K 135,261 Mg 1,310,204 Nb 1,536

Example 2: Preparation of silicon carbide

Manufacture of silicon carbide

The rice husk and rice straw were mixed at a weight ratio of 1: 1 and then milled to an average particle size of about 138 μm. The milled mixture was immersed in an aqueous 1% sulfuric acid solution, heated at 110 DEG C for 5 hours, washed with distilled water and dried. This procedure was repeated twice.

The dried mixture and Mg were mixed at a weight ratio of 10: 1 and then injected into a tubular furnace using an alumina tube. The furnace was purged with Ar gas, methane gas was injected at 30 cc, and a reduction process was performed at 2000 ° C for 5 hours.

The obtained silicon carbide was washed with an aqueous sulfuric acid solution and distilled water, respectively, and then dried.

X-ray diffraction analysis

The silicon carbide thus prepared was measured with an X-ray diffractometer, and the obtained results are shown in FIG.

5 is an X-ray diffraction pattern of the silicon carbide produced in Example 2. Fig. Referring to FIG. 5, it can be seen that silicon carbide (SiC) peaks are predominant and the other peaks are also found to be very small compared to the silicon carbide peaks, and this impurity is also removed by acid cleaning.

ICP analysis

ICP analysis was performed to confirm impurities in the silicon carbide thus produced, and the results obtained are shown in Table 2 below. Referring to Table 2, it can be seen that the content of impurities is less than 0.5% and the purity of silicon carbide is not less than 99.5%.

element Content (ppb) element Content (ppb) Al 1,085,062 P 45,311 B 14,477 Ti 281,120 Cr 35,394 V 1,879 Cu 25,954 Zr 122,552 Fe 418,257 Ca 180,705 Mn 404,149 Mo 5,365 Ni 57,656 Na 65,477 Co 8,006 K 898,340 Mg 1,053,942 Nb 1,744

Example  3: Silicon Hydride  Produce

Preparation of silicon hydride

The rice husk and rice straw were mixed at a weight ratio of 1: 1 and then milled to an average particle size of about 138 μm. The milled mixture was immersed in an aqueous 1% sulfuric acid solution, heated at 110 DEG C for 5 hours, washed with distilled water and dried. This procedure was repeated twice.

The dried mixture and Mg were mixed at a weight ratio of 10: 1 and then injected into a tubular furnace using an alumina tube. The furnace was purged with Ar gas, and 50 cc of NaH was introduced thereinto, followed by reduction at 2000 ° C for 5 hours.

At this time, gaseous silicon hydride formed through the reduction process was condensed and collected at 5 bar and -40 ° C. The obtained silicone hydride was confirmed by gas chromatography, and as a result of the purity measurement, it was confirmed that it had a high purity of 99% or more.

The process according to the invention is applied to the preparation of various silicone compounds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a method for producing polycrystalline silicon from rice hulls or rice straw. FIG.

2 is a block diagram showing a method for producing polycrystalline silicon carbide from rice hulls or rice straw.

3 is a block diagram showing a method for producing silicon hydride from rice hulls or rice straw.

4 is an X-ray diffraction pattern of the polycrystalline silicon produced in Example 1. Fig.

5 is an X-ray diffraction pattern of the polycrystalline silicon carbide produced in Example 2. Fig.

Claims (11)

Milling rice husk or rice straw and acid-treating the same; Mixing the treated rice hull or rice straw with a reducing agent; And And performing a reduction reaction at 1000 占 폚 to 2000 占 폚 in an inert atmosphere in the resulting mixture. The method according to claim 1, wherein the acid treatment is carried out at 40-150 캜 for 10 minutes to 6 hours with one strong acid selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof. Gt; The method according to claim 1, wherein the reducing agent comprises one alkali metal selected from the group consisting of sodium, potassium, magnesium, calcium, manganese, iron, boron, aluminum and combinations thereof. The method of producing a silicon compound according to claim 1, wherein the inert atmosphere is formed by implanting argon (Ar), nitrogen (N ₂ ), helium (He), or a mixed gas thereof. The method for producing a silicon compound according to claim 1, wherein the reduction is carried out at 1000 ° C to 1500 ° C. The method of producing a silicon compound according to claim 1, further comprising injecting a hydrocarbon gas or an alkali metal hydride gas during the reduction reaction. The method of claim 6, wherein the hydrocarbon gas comprises one hydrocarbon gas selected from the group consisting of methane (CH ₄ ), ethane (CH ₃ CH ₃ ), propane (CH ₃ CH ₂ CH ₃ ) ≪ / RTI > 8. The method of claim 6 or 7, wherein the silicon is polycrystalline silicon carbide. The method of producing a silicon compound according to claim 6, wherein the alkali metal hydride gas comprises one selected from the group consisting of calcium hydride (CaH ₂ ), sodium hydride (NaH), and combinations thereof. 10. The method of claim 9, wherein the silicon is silicon hydride. The method of claim 1, wherein the silicon compound is polycrystalline silicon.

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