KR20120033434A

KR20120033434A - Preparation and application method of silicone compound prepared from chaff

Info

Publication number: KR20120033434A
Application number: KR1020100094941A
Authority: KR
Inventors: 노창섭; 최영선
Original assignee: 티오켐 주식회사
Priority date: 2010-09-30
Filing date: 2010-09-30
Publication date: 2012-04-09

Abstract

The present invention relates to a method for producing a silicon compound prepared from rice husk or rice straw, and to a method of producing a silicon compound through a reduction reaction under an inert atmosphere after the acid treatment of the rice husk or rice straw after milling, mixed with a reducing agent will be.
The method can obtain a high purity silicon compound from a rice husk or rice straw through a simple process, and the production of a variety of silicon compounds due to the additional introduction of other source gas. The silicon compound thus prepared is applied to a solar cell.

Description

Preparation and Application of High Purity Silicone Compound Using Chaff {Preparation and application method of silicone compound prepared from chaff}

The present invention relates to a method for preparing a silicone compound prepared from rice husk or rice straw, which can be obtained from a rice husk through a simple process, and is capable of producing various silicone compounds due to the further introduction of other raw material gases.

For the purpose of low carbon green growth, there is a growing interest in renewable energy that does not use hydrocarbon fuel and does not generate carbon dioxide or other harmless foreign substances. There is much interest in the part that can obtain the energy necessary for life by using solar energy which is a part of the renewable energy.

The key to solar energy technology lies in solar cells that convert sunlight directly into electricity.

Recently used solar cells have a photoelectric conversion efficiency of up to about 25%, which is very high, but the manufacturing cost is high, and the cost of electricity production is still very high compared to the existing generation cost such as thermal power and hydropower. Supply is also not smooth.

Accordingly, smooth supply of materials and equipment necessary for the construction of the photovoltaic power generation system is essential for the market development of the newly emerging photovoltaic industry and strengthening competitiveness as alternative energy. In addition, it is necessary to develop new materials, processes, and design technologies that can dramatically increase the conversion efficiency from solar energy to electric energy or make solar cells at a very low cost. In particular, the inexpensive and stable supply of silicon for solar cells is needed. It must be premised.

Solar cells operate on the same principle as semiconductors, and the typical material used for manufacturing them is silicon used in semiconductors. However, silicon for semiconductors has a high impurity content, resulting in a decrease in efficiency in manufacturing solar cells. Solar cell-class silicon (6N-7N), which is a raw material, is difficult to supply in large quantities at low cost because non-standard ultra high purity silicon (11N-12N) products are used or manufactured in the same way as semiconductor silicon. to be.

Silicones in standard commercial processes are prepared by performing a thermocarbonization process on a mixture of 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 the semiconductor and photovoltaic industries. In order to manufacture silicon for solar cells through the thermocarbon reduction process, high-purity raw materials must be used, and a complicated process is required, and thus the manufacturing cost is increased.

On the other hand, all plants contain silica containing carbon. In particular, rice hulls vary depending on the type of rice, climate, geographic environment, etc., but the ash weight ratio is about 90% or more and rice straw contains about 30% or more silica. The rice husk and rice straw is a suitable raw material for the production of silicon for solar cells, which is spotlighted 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, suggests a potential use of rice hulls to produce silicon that is sufficiently pure and low enough to be made into solar cells.

Rice husks and rice straws are also suggested as raw materials for silicon carbide [RV Krishnarao, et.r, J. Am . Chem. Soc . 74, 2869, 1991].

PCT International Publication No. WO 2005/099893 discloses contacting a plant comprising at least about 3% by weight of silica, non-silica minerals and metals with an aqueous sulfuric acid solution having an acid concentration of from about 0.01% to about 30% by weight. After the mixture was prepared, it was reacted at about 10 ° C. to about 250 ° C. for a reaction period of about 6 seconds to about 48 hours, and the minerals were exuded from the plant to give a molar ratio of fixed carbon to silica of at least about 1.0: 1. Mention is made of methods for producing carbon-silica products, ie silicon carbides, adapted to be so adjusted.

Korean Patent Laid-Open No. 2006-102605 discloses a method of manufacturing silicon carbide using chaff and crest as a raw material. Specifically, crushed ash obtained by carbonizing the washed and dried rice husk and rice straw at 300 ~ 600 ℃, respectively, to obtain a powder of powder size less than 1mm, and mixed 50 ~ 80% by weight chaff and 20 to 50% by weight straw rice One mixture is sintered at 750-1200 ° C. for 3 to 13 hours and left at 300-600 ° C. for 1 to 3 hours, followed by grinding and screening to produce silicon carbide. However, this method is a complicated process because it goes through several steps such as carbonization and sintering, heat treatment after sintering.

In addition to it using rice husk and rice straw and research applications such as cement additives [Jose James, et.al, J. Sci. Ind . Res . 51, 383, 1992].

In addition, Korean Patent Publication No. 2001-0096628 discloses a porous silica having a bone or pores of 10 nm or less by oxidizing in an aerobic atmosphere after acid treatment and carbonization in an anoxic atmosphere. As such, a method of using silica contained in rice husk and rice straw in various fields has been researched and developed, and in the present invention, a silicon-based compound usable for solar cells can be obtained from the rice hull and rice straw with high purity, and the simple process A method for preparing a silicon compound is proposed.

It is an object of the present invention to provide a method for preparing a silicone compound which can directly obtain a high purity silicone compound without changing chaff or rice straw into a powder, and which can produce various silicone compounds due to the introduction of other raw material gases. .

In order to achieve the above object,

Acid milling the rice husk or rice straw;

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

It provides a method for producing silicon comprising the step of performing a reduction reaction at 1000 ℃ to 2000 ℃ the mixture obtained in an inert atmosphere.

In this case, the present invention further injects hydrocarbon gas during the reduction reaction to produce polycrystalline silicon carbide as the silicon compound.

In addition, the present invention further injects alkali metal hydrate 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 changing chaff or rice straw into a powder to prepare a high purity silicon compound through a simple process.

In addition, the production of various silicone compounds is possible due to the additional introduction of other source gases in the manufacturing process.

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

The present invention is described in more detail below.

In the present invention, chaff or rice straw is reduced with a reducing agent under an inert atmosphere to prepare various silicone compounds. The silicon compound is silicon (SiO ₂ ), silicon carbide (SiC) and silicon hydride (SiH ₄ , monosilane), which will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a method of making polycrystalline silicon from rice husk or rice straw.

Referring to FIG. 1, a pretreatment process is performed in which an acid treatment is performed after milling rice husk or rice straw which is used as a raw material in order to increase the purity of the final manufactured silicon.

First, chaff or rice straw is milled to a certain size to perform acid treatment.

The milling is performed using a milling machine commonly used, such as a needle milling machine, bed milling machine, universal milling machine, upright milling machine. Rice milled rice husk or rice straw has a size of 50 ~ 500 ㎛.

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

The acid treatment dissolves organic components, metal components or impurities contained in rice husk or rice straw and uses a strong acid of 0.1-10M. The strong acid is typically one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof.

The immersion time is appropriately adjusted according to the concentration or throughput of the acid solution, for example, is performed for 10 minutes-6 hours. The acid treatment can be carried out by applying heat if necessary, preferably at 40 ~ 150 ℃, more preferably at 60 ~ 100 ℃. This acid treatment is carried out one or more times, preferably 1 to 10 times, in which case it can be carried out in a multi-step process by varying the type, concentration, temperature, etc. of the acid solution.

Next, the chaff or rice straw pretreated in the previous step is introduced into a reactor to carry out reduction, to which an alkali metal as a reducing agent is added.

Rice husk or rice straw can be various materials as the reducing agent for reducing, and preferably an alkali metal is 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 use between 100 g and 120 g for 1 kg of rice hulls or crests. If the content of the alkali metal is less than the above range, sufficient reduction is not achieved or the time due to the reduction is long, and if it exceeds the above range, impurities are increased as the amount of the reducing agent is increased, so it is uneconomical, and it is appropriate within the above range. To perform.

Next, a reduction reaction is performed by injecting an inert gas into the reactor.

Inert atmosphere is achieved by injecting argon (Ar), nitrogen (N ₂ ), helium (He) or a mixture of these.

Reducing reaction of rice husk or rice straw using the reducing agent is carried out at 1000 ℃ to 2000 ℃, preferably 1000 ℃ to 1500 ℃. If the treatment temperature is less than the above temperature, the reduction reaction is less than the SiO ₂ remains unreacted, on the contrary, if the temperature is above the temperature, the reduced Si again oxidizes, returning to the oxidized foam SiO ₂ The problem arises that the reaction occurs in an unwanted direction.

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

Chaff or rice straw is carbonized to generate silica and carbon components, and the produced silica is reduced by alkali metal and carbon to produce polycrystalline silicon. According to preferred Example 1, it can be seen that the process of producing silicon from chaff is very simple, so that many benefits can be expected economically and the reaction mechanism is simple to facilitate the reaction. According to FIG. 4, it can be seen that the manufactured silicon has polycrystals and has a purity of 99.95% or more.

The method according to the present invention is capable of producing silicon carbide, silicon hydride and the like in addition to silicon by adding various source gases together with a reducing agent.

2 is a block diagram showing a method of making silicon carbide from rice husk or rice straw.

Referring to FIG. 2, silicon carbide is prepared by pretreating chaff 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 of carbon (C) of silicon carbide, preferably consisting of methane (CH ₄ ), ethane (CH ₃ CH ₃ ), propane (CH ₃ CH ₂ CH ₃ ), and combinations thereof One species selected from the group is possible.

The hydrocarbon gas is used 5 to 40 cc per minute for 1 kg of chaff or rice sheath used as a raw material. If the content of hydrocarbon gas is less than the above range, the production of silicon carbide is reduced and unreacted silica is present as an impurity. Exceeding the above range is not economical along with the problem of other impurities other than silicon carbide, so it is properly performed within the above range. This hydrocarbon gas is injected at 5 to 40 cc per minute in the reactor.

This step produces silicon carbide. According to the preferred embodiment 2, the process of the present silicon carbide is also similar to the silicon manufacturing process is simple, it can be seen that a lot of economic benefits can be obtained. According to FIG. 5, it can be seen that the manufactured silicon carbide has polycrystals and has a purity of 99.5% or more.

FIG. 3 is a block diagram showing a method of preparing silicon hydride (SiH ₄ ) from rice husk or rice straw.

Referring to FIG. 3, silicon hydride is prepared by pretreating chaff 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 hydrate gas.

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

The alkali metal hydrate gas is used 20 to 60 cc for 1 kg of chaff or rice hull used as a raw material. If the content of the alkali metal hydrate gas is less than the above range, silicon is formed in addition to the silicon carbide, and if it exceeds the above range, excessive silicon hydride and the remaining excess impurities are uneconomical. Perform. This alkali metal hydrate gas is injected at a rate of 20 to 60 cc in the reactor.

This step produces silicon hydride. According to the third preferred embodiment, the silicon hybrid can also be seen that the process is simple, bringing a lot of economic benefits to the actual process.

Currently silicon hydrides are prepared primarily by dismutation of trichlorosilane (see, eg, WO 100 17 168 A1, US Pat. No. 3 968 199). The silicon hydride thus prepared has impurities such as dichlorosilane and monochlorosilane and must be subjected to a separate purification process.

However, according to the present invention, it is possible to recover high purity silicon hydride by condensation under economic conditions after the reduction process. Condensation is carried out at a temperature of +50 to -80 ° C, particularly preferably -50 to 10 ° C, at a pressure desired for disproportionation, for example, at an absolute pressure of 5 to 25 bar.

The method as described above can be simply subjected to a reduction treatment at a high temperature with a reducing agent to produce a variety of silicon, such as silicon, silicon carbide, silicon hydride. This method is simpler and more economical than conventional methods, and the final manufactured silicon compounds are also highly pure and applicable to various fields.

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

Claims

Acid milling the rice husk or rice straw;
Mixing the treated chaff or rice straw with a reducing agent; And
Method for producing a silicon comprising the step of performing a reduction reaction at 1000 ℃ to 2000 ℃ the mixture obtained in an inert atmosphere.