Method for producing silicon metal

Abstract

Provided is a method for producing silicon metal, with which it is possible to reduce the energy consumed when producing silicon metal by recycling glass waste or the like. A method for producing silicon metal according to the present disclosure comprises: a first pulverization step for pulverizing a material to be treated containing silica; a second pulverization step in which a reduction material containing aluminum is pulverized; a material mixing step for mixing the material to be processed pulverized in the first pulverizing step and the reducing material pulverized in the second pulverizing step; and a heating reduction step in which the material to be processed and the reducing material, which have been mixed in the material mixing step, are subjected to a heating reduction reaction in a heating atmosphere in the range of 800 DEG C to 1200 DEG C, thereby obtaining silicon metal.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for producing metallic silicon from a recycled material containing silicon dioxide. BACKGROUND

[0002] In recent years, efforts to drastically reduce the generation of waste are being actively made by preventing, reducing the generation of waste, recycling, and reusing waste. In order to achieve this purpose, research and development related to the recycling of metallic silicon are being conducted.

[0003] For example, Patent Literature 1 discloses a method for producing metallic silicon by heating a glass containing silicon dioxide and metallic aluminum to 1450°C or higher to melt it, reducing the silicon dioxide, thereby generating metallic silicon.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-193612 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the technology related to the recycling of metallic silicon, the problem is to reduce the consumed energy consumed at the time of production of metallic silicon.

[0009] In order to solve the above problem, the purpose of the present application is to achieve a reduction in energy consumed at the time of production of metallic silicon by recycling of glass waste and the like. Furthermore, it contributes to a drastic reduction in the generation of waste.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] As a means for achieving the above purpose, a method for producing metallic silicon can be cited, which includes: a first pulverization step of pulverizing a treatment target material containing silicon dioxide; a second pulverization step of pulverizing a reduction material containing aluminum; a material mixing step of mixing the treatment target material pulverized by the first pulverization step and the reduction material pulverized by the second pulverization step; and a heating reduction step of causing the treatment target material and the reduction material mixed by the material mixing step to undergo a heating reduction reaction based on a heating atmosphere in the range of 800°C to 1200°C, thereby obtaining metallic silicon.

[0012] In the above method for producing metallic silicon, the treatment target material can be waste glass or silicate plant, and the reduction material can be waste aluminum.

[0013] In the production method of the metal silicon, the heating reduction step can be performed in a non-active gas atmosphere.

[0014] In the production method of the metal silicon, the heating reduction step can be performed by adding potassium carbonate.

[0015] In the production method of the metal silicon, the heating reduction step can be performed by a heating atmosphere of 1000°C or less.

[0016] In the production method of the metal silicon, the processing target material and the reducing material in the material mixing step can be mixed in a state of being pulverized to a particle size of 1 mm or less.

[0017] In the production method of the metal silicon, the production method can further include a silicone rubber production step of producing a silicone rubber using the metal silicon obtained in the heating reduction step as a material.

[0018] Effects of the Invention

[0019] According to the production method of the metal silicon, energy consumed in the production of the metal silicon from recycled glass waste or the like can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a process diagram of a production method of metal silicon.

[0021] Figure 2 is an explanatory diagram showing an evaluation of a production result of metal silicon using waste glass as a processing target material.

[0022] Figure 3 is an explanatory diagram showing a result of XRD measurement in the production of metal silicon using waste glass as a processing target material without adding potassium carbonate.

[0023] Figure 4 is an explanatory diagram showing a result of XRD measurement in the production of metal silicon using waste glass as a processing target material with the addition of potassium carbonate. DETAILED DESCRIPTION

[0024] [1. Process of Production Method of Metal Silicon]

[0025] REFERENCE Figure 1The process of the method of producing metal silicon according to the present embodiment will be described. The method of producing metal silicon according to the present embodiment produces metal silicon by a first pulverization process PR1, a second pulverization process PR2, a material mixing process PR3, and a heating reduction process PR4, using crushed glass as a treatment target material and aluminum chips as a reducing material. Furthermore, the method of producing metal silicon according to the present embodiment produces silicone rubber by a silicone rubber production process PR5, using the metal silicon produced by the processes PR1 to PR4 as a material.

[0026] In the first pulverization process PR1, the crushed glass, which is a treatment target material containing silicon dioxide, is pulverized to a size that can be fed into a planetary ball mill used in the material mixing process PR3. Note that, in a case where the crushed glass is carried in a state of being broken into a size that can be fed into the planetary ball mill, a process of breaking the waste glass into the crushed glass corresponds to the first pulverization process according to the present disclosure.

[0027] The crushed glass is a glass chip recovered by breaking a glass product when recycling the glass product. The treatment target material can be a material containing silicon dioxide, and can be, in addition to the waste glass, a plant such as a silicate plant. The silicate plant includes a grass plant, a moss plant, a fern plant, and the like, and, for example, a rice hull ash of a rice can be used as the treatment target material to produce metal silicon.

[0028] In the second pulverization process PR2, the aluminum chips, which are a reducing material containing aluminum, are pulverized to a size that can be fed into a planetary ball mill used in the material mixing process PR3. Note that, in a case where the aluminum chips are carried in a state of being broken into a size that can be fed into the planetary ball mill, a process of breaking an aluminum can and the like, which is a waste aluminum, corresponds to the second pulverization process 2 according to the present disclosure. The aluminum contained in the aluminum chips functions as a reducing agent for silicon dioxide.

[0029] In the material mixing process PR3, as indicated in the text box B1, the crushed glass pulverized in the first pulverization process PR1 and the aluminum chips pulverized in the second pulverization process 2 are fed into a planetary ball mill, and the crushed glass and the aluminum chips are mixed while being further pulverized. In this case, a process of pulverizing the crushed glass by the planetary ball mill corresponds to the first pulverization process according to the present disclosure, and a process of pulverizing the aluminum chips by the planetary ball mill corresponds to the second pulverization process according to the present disclosure. Through the pulverization and mixing, the contact area between the crushed glass and the aluminum chips increases, and a state in which the crushed glass and the aluminum chips are uniformly dispersed can be formed.

[0030] In the heating reduction process PR4, as shown in text box B2, the mixture of broken glass and aluminum shavings mixed in the material mixing process PR3 is placed in a sample container such as a crucible, and heated and reduced in an electric furnace at a set temperature of 800℃ to 1200℃ under an Ar atmosphere. This results in the aluminothermic reaction of the following reaction formula (1), yielding metallic silicon. It should be noted that the broken glass contains Na2O3 and other substances originally added to improve the glass's processability.

[0031] 3SiO2+4Al→3Si+2Al2O3·····(1)

[0032] Here, through the first crushing step PR1, the second crushing step PR2, and the material mixing step PR3, as described above, the crushed glass and aluminum shavings are mixed in a state where they are crushed to a very small particle size (preferably less than 1 mm, more preferably less than 50 μm). This increases the contact area between the crushed glass and the aluminum shavings, and the silica and aluminum become uniformly dispersed. As a result, the aluminothermic reaction is promoted, and the heat generated by the aluminothermic reaction increases, thus allowing for a reduction in the heating temperature setting of the electric furnace (preferably less than 1000°C), thereby reducing energy consumption.

[0033] In addition, potassium carbonate can be added in the heating reduction process PR4. By adding potassium carbonate, the melting point of the shattered glass can be lowered, thus reducing the set temperature of the electric furnace and further reducing energy consumption.

[0034] In the silicone rubber manufacturing process PR5, as shown in text box B3, the mixture of metallic silicon and alumina generated in the aluminothermic reaction of the above reaction formula (1) in the heating reduction process PR4 is reacted with chloromethane at 300°C to 560°C. Then, the resulting dimethyldichlorosilane is separated and purified by distillation, and silicone rubber precursors are synthesized using dimethyldichlorosilane. It should be noted that high-purity metallic silicon can also be obtained by reacting the mixture of metallic silicon and alumina with hydrochloric acid at 300°C to separate and purify the resulting trichlorosilane.

[0035] [2. Evaluation]

[0036] Reference Figures 2 to 4 , for execution based on Figure 1 The evaluation of the results of the manufacturing method of metallic silicon shown in the process is explained. Figure 2 T1 shows the measurement results when the heating temperature setting of the electric furnace in the heating reduction process PR4 is switched to 800℃, 1000℃, and 1200℃, and the presence or absence of potassium carbonate is switched, and the micro Raman measurement of the generated sample is performed.

[0037] It is confirmed from T1 that metal silicon is obtained in the case where the setting of the heating temperature of the electric furnace is set to any one of 800°C, 1000°C, and 1200°C, and in the case where potassium carbonate is added and in the case where potassium carbonate is not added.

[0038] Next, Figure 3 A comparative result of XRD measurement when potassium carbonate is not added and the setting temperature of the electric furnace is set to 800°C and 1000°C in the heating reduction step PR4 is shown. Figure 3 T2 is a measurement result when the setting temperature of the electric furnace is set to 800°C, and T3 is a measurement result when the setting temperature of the electric furnace is set to 1000°C.

[0039] Metal silicon is identified in either of T2 and T3, so it is confirmed that metal silicon is obtained. Comparing T2 and T3, the FOM (figure of merit) is smaller in T2, so it is confirmed that the degree of agreement of T2 with metal silicon at the setting temperature of 800°C is high.

[0040] Next, Figure 4 A comparative result of XRD measurement when potassium carbonate is added and the setting temperature of the electric furnace is set to 800°C and 1000°C in the heating reduction step PR4 is shown. Figure 4 T4 is a measurement result when the setting temperature of the electric furnace is set to 800°C, and T5 is a measurement result when the setting temperature of the electric furnace is set to 1000°C.

[0041] Metal silicon is identified in either of T4 and T5, so it is confirmed that metal silicon is obtained. Comparing T4 and T5, the FOM is smaller in T4, so it is confirmed that the degree of agreement of T4 with the pattern data of metal silicon at the setting temperature of 800°C is high.

[0042] In addition, in the case where rice husk ash is used as the treatment target material and aluminum scraps are used as the reduction material, metal silicon is confirmed to be obtained by the above-described Figure 1 processes by XRD measurement, as in the case where crushed glass is used as the treatment target material.

[0043] [3. Other Embodiments]

[0044] In the above-described embodiments, crushed glass, which is waste glass, is used as the treatment target material containing silicon dioxide, but other waste glass (hot crushed glass discarded from a glass melting furnace, glass powder discarded in glass processing, and the like) can be used. In addition, instead of using waste glass, a general glass can be used as the treatment target material containing silicon dioxide.

[0045] In addition, as examples of the plant silicas that can be used as the treatment target material, plants of the Gramineae family such as rice, corn, sugarcane, horsetail, wheat, barley, rye, Job's tears, millet, millet, millet, and miscanthus can be given.

[0046] In the above embodiment, the heating reduction step PR4 is performed in an argon atmosphere, but another non-reactive gas can be used.

[0047] In the above embodiment, in the material mixing step PR3, the processing target material and the reduction material are mixed while being pulverized by a planetary ball mill, and thus the configuration in which the first and second pulverization steps of the present disclosure are included in the material mixing step, but the configuration in which the first and second pulverization steps of the present disclosure are separated from the material mixing step can be used.

[0048] In the heating reduction step PR4, the residue (SiO2+Al2O3) generated from unreacted aluminum and the like can be used as a ceramic raw material such as mullite (composition: 3Al2O3·2SiO2~2Al2O3·SiO2).

[0049] [4. Configuration supported by the above embodiment]

[0050] The above embodiment is a specific example of the following configuration.

[0051] (1) A method of manufacturing metallic silicon, comprising: a first pulverization step of pulverizing a processing target material containing silicon dioxide; a second pulverization step of pulverizing a reduction material containing aluminum; a material mixing step of mixing the processing target material pulverized by the first pulverization step and the reduction material pulverized by the second pulverization step; and a heating reduction step of causing the processing target material and the reduction material mixed by the material mixing step to undergo a heating reduction reaction based on a heating atmosphere in a range of 800°C to 1200°C, to obtain metallic silicon.

[0052] According to the method of manufacturing metallic silicon of the configuration 1, the processing target material and the reduction material are mixed after being pulverized by the first and second pulverization steps and the material mixing step, and thus the temperature of the heating atmosphere in the heating reduction step can be reduced. Thus, the energy consumed when manufacturing metallic silicon by recycling glass waste and the like can be reduced.

[0053] (2) The method of manufacturing metallic silicon according to the configuration 1, in which the processing target material is waste glass or plant silicate, and the reduction material is waste aluminum.

[0054] According to the method of manufacturing metallic silicon of the configuration 2, waste glass or plant silicate containing silicon dioxide is used as the processing target material, and waste aluminum is used as the reduction material, and thus metallic silicon can be manufactured.

[0055] (3) The method of manufacturing metallic silicon according to the configuration 1 or the configuration 2, in which the heating reduction step is performed in a non-reactive gas atmosphere.

[0056] According to the method for manufacturing metal silicon according to the constitution 3, by performing the heating reduction step in a non-active gas atmosphere, oxidation of the obtained metal silicon can be suppressed.

[0057] (Constitution 4) The method for manufacturing metal silicon according to any one of the constitutions 1 to 3, wherein the heating reduction step is performed with addition of potassium carbonate.

[0058] According to the method for manufacturing metal silicon according to the constitution 4, by adding potassium carbonate, the melting point of the processing target material containing silicon dioxide can be lowered, and the temperature of the heating atmosphere in the heating reduction step can be lowered.

[0059] (Constitution 5) The method for manufacturing metal silicon according to any one of the constitutions 1 to 4, wherein the heating reduction step is performed with a heating atmosphere of 1000°C or lower.

[0060] According to the method for manufacturing metal silicon according to the constitution 5, by setting the temperature of the heating atmosphere in the heating reduction step to 1000°C or lower in the range of 800°C to 1200°C, the energy consumption at the time of manufacturing metal silicon can be further reduced.

[0061] (Constitution 6) The method for manufacturing metal silicon according to any one of the constitutions 1 to 5, wherein in the material mixing step, the processing target material and the reducing material are mixed in a state of being pulverized to a particle size of 1 mm or less.

[0062] According to the method for manufacturing metal silicon according to the constitution 6, by mixing the processing target material and the reducing material in a state of being pulverized to a particle size of 1 mm or less, the contact area of the processing target material and the reducing material in the material mixing step can be increased, and the dispersion of the processing target material and the reducing material can be homogenized. Thus, the reaction (aluminothermic reaction) of the processing target material and the reducing material is promoted, and the heat generated along with the reaction increases, so the energy required to maintain the temperature of the heating atmosphere can be reduced.

[0063] (Constitution 7) The method for manufacturing metal silicon according to any one of the constitutions 1 to 6, further comprising a silicone rubber manufacturing step of manufacturing silicone rubber using the metal silicon obtained by the heating reduction step as a material.

[0064] According to the method for manufacturing metal silicon according to the constitution 7, the metal silicon manufactured with reduced energy consumption can be used as a material for silicone rubber.

[0065] Explanation of symbols

[0066] PR1: 1st pulverization step, PR2: 2nd pulverization step, PR3: material mixing step, PR4: heating reduction step, PR5: silicone rubber production step.

Claims

1. A method for producing silicon metal, comprising: a first pulverization step of pulverizing a treatment target material containing silicon dioxide; a second pulverization step of pulverizing a reducing material containing aluminum; a material mixing step of mixing the treatment target material pulverized by the first pulverization step and the reducing material pulverized by the second pulverization step; and a heating reduction step of causing the treatment target material and the reducing material mixed by the material mixing step to undergo a heating reduction reaction based on a heating atmosphere in a range of 800°C to 1200°C, to obtain silicon metal. The treatment target material is waste glass or a plant silicate, 2. The method of producing silicon metal according to claim 1, wherein The reducing material is waste aluminum. The heating reduction step is performed in a non-active gas atmosphere.

3. The method of producing silicon metal according to claim 1 or 2, wherein, The heating reduction step is performed with the addition of potassium carbonate.

4. The method of producing silicon metal as claimed in claim 1 or 2, wherein, The heating reduction step is performed by a heating atmosphere of 1000°C or lower.

5. The method of producing silicon metal as claimed in claim 1 or 2, wherein, In the material mixing step, the treatment target material and the reducing material are mixed in a state of being pulverized to a particle size of 1 mm or less.

6. The method of producing silicon metal as claimed in claim 1 or 2, wherein, 7. The method for producing silicon metal according to claim 1 or 2, further comprising an organosilicon rubber production step of producing organosilicon rubber using silicon metal obtained by the heating reduction step as a material. ​

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