用碳化稻殼電熱冶金法制備超冶金級硅的研究
發(fā)布時間：2018-09-01 19:16
【摘要】：全球煤、石油等傳統(tǒng)能源的日益枯竭,能源危機已迫在眉睫,太陽能作為安全、分布廣泛、清潔的可再生新能源得到了快速的發(fā)展,已成為21世紀(jì)最重要的新能源。硅是太陽能電池最重要的基礎(chǔ)材料,降低硅材料的成本已成為發(fā)展光伏能源的關(guān)鍵,但是制備多晶硅的主要技術(shù)改良西門子法主要壟斷在美、日、德等國手中。我國因沒有掌握該法的核心技術(shù),多晶硅主要依賴于進口。冶金法制備太陽能級多晶硅具有低成本、低能耗、無污染、生產(chǎn)安全的特點。研究擁有自主知識產(chǎn)權(quán)的冶金法制備多晶硅技術(shù)對發(fā)展我國光伏產(chǎn)業(yè)有著重要的戰(zhàn)略意義。所謂超冶金級硅(UMG-Si)就是指Si純度高于冶金級硅,Fe、Al、Ca、P、B等雜質(zhì)的含量要低于國家A級工業(yè)硅的標(biāo)準(zhǔn),是電熱冶金法制備太陽能級多晶硅的中間產(chǎn)品。本文研究了用碳化稻殼電熱冶金法制備超冶金級硅技術(shù)和機理,為電熱冶金法制備太陽能級多晶硅奠定基礎(chǔ)。由于碳化稻殼(CRH)含碳量較高(50%),而且還含有一定量的Si02(約25%)是冶煉Si時優(yōu)良的碳質(zhì)還原劑。主要內(nèi)容有：(1)碳化稻殼粉的除雜研究；(2)配料及球團物理性能的研究；(3)粉體原料電熱冶金法制備硅過程中熱力學(xué)分析與驗證；(4)碳化稻殼粉體原料熔煉硅的研究；(5)碳化稻殼粉和石油焦粉混合粉體原料熔煉超冶金級硅的研究；(6)冶金級硅吹氣精煉除磷的研究。得到的主要結(jié)論有：(1)碳化稻殼最佳酸浸工藝為：CRH粉在75μm以下,鹽酸濃度為5wt%,反應(yīng)時間3h,水浴溫度為60℃,浸出液固比14：1,攪拌速度60r/min,金屬元素的總?cè)コ蔬_96.41%,非金屬元素的總?cè)コ蕿?6.68%；超聲酸浸后CRH粉中的雜質(zhì)元素去除率要比機械攪拌酸浸后雜質(zhì)去除率高,其中金屬元素的總?cè)コ蔬_99.07%、非金屬元素的總?cè)コ蕿?1.77%。超聲酸浸過程中隨著時間的延長除雜效果不明顯。真空高溫焙燒除雜的最佳工藝條件：CRH粒度在75μm以下、保溫時間120min、保溫溫度1100℃、壓力70kPa。此時,磷的去除率達91.85%、硫的去除率達88.96%。在真空條件下,除去碳化稻殼粉中的磷酸鹽雜質(zhì)是可行的,真空度越高,反應(yīng)溫度降低越顯著。在體系壓力為70kPa時,除磷反應(yīng)的溫度為1100℃(1373K)。(2)碳化稻殼與空氣發(fā)生氧化反應(yīng)的活化能E和指前因子A,分別為78.89 kJ·mol-1和2083.03min-1。計算表明,以碳化稻殼粉為碳質(zhì)還原劑時球團的物料配比為：石英砂粉：碳化稻殼粉：粘結(jié)劑=100：85.14：0.56,其最佳工藝條件為：物料粒度75μm,壓制壓力15MPa,粘結(jié)劑加入量3%,配水量7wt%,此時,球團的抗壓強度為3.0MPa,氣孔率為38.6%。以混合碳質(zhì)還原劑時球團的物料配比為：石英砂粉：碳化稻殼粉：石油焦粉：粘結(jié)劑=100：54.61：22.34：0.53,其最佳工藝條件為：物料粒度75μm,壓制壓力20MPa,粘結(jié)劑加入量3%,配水量6wt%。此時,球團的抗壓強度為5.8MPa,氣孔率為25.2%。(3)計算了Si-C-0體系中各反應(yīng)的吉布斯自由能和溫度的關(guān)系,確定了各反應(yīng)發(fā)生的最低溫度,同時通過HSC熱力學(xué)計算軟件驗證了計算所得結(jié)果。在C還原Si02的‘過程中,存在著SiO和SiC生成和分解反應(yīng),當(dāng)溫度升高到1900℃,產(chǎn)物中才出現(xiàn)了Si相,同時存在SiC、SiO2相和少量的SiO相。(4)研究結(jié)果表明,利用碳化稻殼粉體原料作為碳質(zhì)還原劑來熔煉硅是可行的,且得到了純度為99.32wt%國家二級工業(yè)硅,其主要的鐵、鋁和鈣等金屬雜質(zhì)含量均低于現(xiàn)有國家A級工業(yè)硅(化學(xué)用硅)標(biāo)準(zhǔn),最重要的是產(chǎn)物硅中磷和硼分別只有26ppmw和15ppmw,均低于現(xiàn)有工業(yè)硅中磷(120～200ppmw)和硼(20～60ppmw)的含量,這說明可以通過控制原料中雜質(zhì)含量來控制熔煉產(chǎn)物中雜質(zhì)含量。(5)利用碳化稻殼粉和石油焦粉混合粉體為碳質(zhì)還原劑時,研究結(jié)果表明,礦熱爐冶煉過程中,當(dāng)輸出電流穩(wěn)定在500A時,合適的輸出電壓為25-30V；額外碳配入量為30%時,Si的收率為最大值30.7%,此時爐底渣中的SiC的含量也較少；產(chǎn)物中硅的含量為99.68wt%,已經(jīng)超過了國家A級工業(yè)硅(化學(xué)用硅)的標(biāo)準(zhǔn)(Si%≥99.60%),其主要的鐵、鋁和鈣等金屬雜質(zhì)含量均低于現(xiàn)有國家A級工業(yè)硅標(biāo)準(zhǔn),磷、硼含量分別為24ppmw和14ppmw,也都低于現(xiàn)有工業(yè)硅中磷和硼的含量。制備出了超過冶金級硅最高標(biāo)準(zhǔn)的超冶金級高品質(zhì)硅。(6)冶金級硅吹氣精煉除磷的研究,結(jié)果表明,在使用側(cè)壁和底部多孔型噴嘴,精煉時間為3小時,精煉溫度為1793K,精煉氣溫度為373K,精煉氣流速為2L/min,作為最佳吹氣精煉條件時,硅熔體中的磷元素由94ppmw降低到11 ppmw。從熱力學(xué)和動力學(xué)分析可以得出,精煉氣中的水蒸氣和熔硅反應(yīng)生成硅的氧化物和H2,部分H2溶解于熔硅中。然后熔硅中的[H]再和熔硅中的[P]反應(yīng)生成PH3, PH3隨后被氬氣泡帶離開熔硅。進而得出,吹氣(Ar-H2O)精煉的方法能有效的去除冶金級硅熔液中的雜質(zhì)磷。本研究實現(xiàn)了用碳化稻殼粉體原料電熱冶金法制備超冶金級硅的工藝,這為用高純粉體原料電熱冶金法制備太陽能級多晶硅奠定了基礎(chǔ)。
[Abstract]:As a safe, widely distributed and clean renewable energy, solar energy has developed rapidly and has become the most important new energy in the 21st century. Silicon is the most important basic material for solar cells. Reducing the cost of silicon materials has become the development of photovoltaic energy. The key point is that the main technological improvement of the Siemens method is mainly monopolized in the United States, Japan, Germany and other countries. China has not mastered the core technology of the method, and polycrystalline silicon mainly depends on imports. The technology of metallurgical preparation of polycrystalline silicon by weight is of strategic importance to the development of photovoltaic industry in China. The so-called super-metallurgical grade silicon (UMG-Si) means that the purity of silicon is higher than that of metallurgical grade silicon, such as Fe, Al, Ca, P and B, and the content of impurities is lower than the national A-grade industrial silicon standard. The technology and mechanism of preparing super-metallurgical grade silicon from carbonized rice husk by electrothermal metallurgy were studied, which laid a foundation for the preparation of solar grade polysilicon by electrothermal metallurgy. The carbonized rice husk (CRH) contains high carbon content (50%) and a certain amount of Si02 (about 25%) is an excellent carbon reducing agent for smelting Si. (2) Study on the proportioning and physical properties of pellets; (3) Thermodynamic analysis and verification in the preparation of silicon from powdered materials by electrothermal metallurgy; (4) Study on melting silicon from carbonized rice husk powder; (5) Study on melting super-metallurgical grade silicon from the mixture of carbonized rice husk powder and petroleum coke powder; (6) Study on refining phosphorus removal from metallurgical grade silicon by gas blowing. The main conclusions are as follows: (1) The optimum acid leaching process for carbonized rice husk is as follows: CRH powder is below 75 micron, hydrochloric acid concentration is 5wt%, reaction time is 3h, water bath temperature is 60, leaching liquid-solid ratio is 14:1, stirring speed is 60r/min, the total removal rate of metal elements is 96.41%, the total removal rate of non-metal elements is 66.68%; the impurities in CRH powder after ultrasonic acid leaching are 66.68%. The total removal rate of metal elements and non-metal elements was 99.07% and 71.77% respectively. The removal effect was not obvious with the extension of ultrasonic acid leaching time. The phosphorus removal rate was 91.85% and the sulfur removal rate was 88.96%. It was feasible to remove the phosphate impurities in carbonized rice husk powder under vacuum condition. The higher the vacuum degree, the lower the reaction temperature was. When the system pressure was 70 kPa, the temperature of phosphorus removal reaction was 1100 ((1373K). (2) Carbonized rice husk and air. The activation energy E and pre-exponential factor A of the oxidation reaction were 78.89 kJ.mol-1 and 2083.03 min-1, respectively. The results showed that the material ratio of the pellets with carbonized rice husk powder as carbon reducing agent was quartz sand powder: carbonized rice husk powder: binder = 100:85.14:0.56, and the optimum technological conditions were as follows: the particle size of the pellets was 75 micron, the pressing pressure was 15 MPa, and the binder was 100:85.14:0.56. The compressive strength and porosity of the pellets were 3.0 MPa and 38.6% respectively when the dosage of the additive was 3% and the dosage of water was 7 wt%. When the mixture of carbon reducing agent was used, the pellets were composed of quartz sand powder, carbonized rice hull powder, petroleum coke powder, binder = 100:54.61:22.34:0.53. The compressive strength of the pellets was 5.8 MPa and the porosity was 25.2%. (3) The relationship between Gibbs free energy and temperature of the reactions in the Si-C-0 system was calculated, and the lowest temperature of the reactions was determined. The calculated results were verified by HSC thermodynamic calculation software. The formation and decomposition reactions of iO and SiC occur only when the temperature is raised to 1900 C, and there are SiC, SiO2 and a small amount of SiO phases in the product. (4) The results show that it is feasible to melt silicon by using carbonized rice husk powder as carbon reducing agent, and the secondary industrial silicon with purity of 99.32wt% is obtained. The content of impurities in the product silicon is only 26 ppmw and 15 ppmw respectively, which are lower than that of phosphorus (120-200 ppmw) and boron (20-60 ppmw) in the existing industrial silicon. (5) When the mixed powders of carbonized rice husk powder and petroleum coke powder are used as carbon reductants, the results show that the suitable output voltage is 25-30V when the output current is stable at 500A, and the maximum yield of silicon is 30.7% when the additional carbon content is 30%, and the content of silicon in the bottom slag is also less. The content is 99.68 wt%, which has exceeded the national A-grade industrial silicon (chemical silicon) standard (Si%>99.60%). The main iron, aluminum and calcium impurities are lower than the existing national A-grade industrial silicon standard. The contents of phosphorus and boron are 24 ppmw and 14 ppmw respectively, which are also lower than the existing industrial silicon phosphorus and boron content. High-quality super-metallurgical grade silicon. (6) Study on phosphorus removal from metallurgical grade silicon by gas blowing refining. The results show that phosphorus in silicon melt decreases from 94 ppmw when using side wall and bottom porous nozzles, refining time is 3 hours, refining temperature is 1793 K, refining temperature is 373 K and refining gas velocity is 2 L/min. From thermodynamic and kinetic analysis, it can be concluded that water vapor in refining gas reacts with molten silicon to form silicon oxide and H2, and part of H2 dissolves in molten silicon. Then [H] in molten silicon reacts with [P] in molten silicon to form PH3, which is then taken away from molten silicon by argon bubbles. In this study, the preparation of super-metallurgical silicon from carbonized rice husk powder by electrothermal metallurgy was realized, which laid a foundation for the preparation of solar-grade polysilicon by electrothermal metallurgy with high-purity powder.
【學(xué)位授予單位】：東北大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN304.12
[Abstract]:As a safe, widely distributed and clean renewable energy, solar energy has developed rapidly and has become the most important new energy in the 21st century. Silicon is the most important basic material for solar cells. Reducing the cost of silicon materials has become the development of photovoltaic energy. The key point is that the main technological improvement of the Siemens method is mainly monopolized in the United States, Japan, Germany and other countries. China has not mastered the core technology of the method, and polycrystalline silicon mainly depends on imports. The technology of metallurgical preparation of polycrystalline silicon by weight is of strategic importance to the development of photovoltaic industry in China. The so-called super-metallurgical grade silicon (UMG-Si) means that the purity of silicon is higher than that of metallurgical grade silicon, such as Fe, Al, Ca, P and B, and the content of impurities is lower than the national A-grade industrial silicon standard. The technology and mechanism of preparing super-metallurgical grade silicon from carbonized rice husk by electrothermal metallurgy were studied, which laid a foundation for the preparation of solar grade polysilicon by electrothermal metallurgy. The carbonized rice husk (CRH) contains high carbon content (50%) and a certain amount of Si02 (about 25%) is an excellent carbon reducing agent for smelting Si. (2) Study on the proportioning and physical properties of pellets; (3) Thermodynamic analysis and verification in the preparation of silicon from powdered materials by electrothermal metallurgy; (4) Study on melting silicon from carbonized rice husk powder; (5) Study on melting super-metallurgical grade silicon from the mixture of carbonized rice husk powder and petroleum coke powder; (6) Study on refining phosphorus removal from metallurgical grade silicon by gas blowing. The main conclusions are as follows: (1) The optimum acid leaching process for carbonized rice husk is as follows: CRH powder is below 75 micron, hydrochloric acid concentration is 5wt%, reaction time is 3h, water bath temperature is 60, leaching liquid-solid ratio is 14:1, stirring speed is 60r/min, the total removal rate of metal elements is 96.41%, the total removal rate of non-metal elements is 66.68%; the impurities in CRH powder after ultrasonic acid leaching are 66.68%. The total removal rate of metal elements and non-metal elements was 99.07% and 71.77% respectively. The removal effect was not obvious with the extension of ultrasonic acid leaching time. The phosphorus removal rate was 91.85% and the sulfur removal rate was 88.96%. It was feasible to remove the phosphate impurities in carbonized rice husk powder under vacuum condition. The higher the vacuum degree, the lower the reaction temperature was. When the system pressure was 70 kPa, the temperature of phosphorus removal reaction was 1100 ((1373K). (2) Carbonized rice husk and air. The activation energy E and pre-exponential factor A of the oxidation reaction were 78.89 kJ.mol-1 and 2083.03 min-1, respectively. The results showed that the material ratio of the pellets with carbonized rice husk powder as carbon reducing agent was quartz sand powder: carbonized rice husk powder: binder = 100:85.14:0.56, and the optimum technological conditions were as follows: the particle size of the pellets was 75 micron, the pressing pressure was 15 MPa, and the binder was 100:85.14:0.56. The compressive strength and porosity of the pellets were 3.0 MPa and 38.6% respectively when the dosage of the additive was 3% and the dosage of water was 7 wt%. When the mixture of carbon reducing agent was used, the pellets were composed of quartz sand powder, carbonized rice hull powder, petroleum coke powder, binder = 100:54.61:22.34:0.53. The compressive strength of the pellets was 5.8 MPa and the porosity was 25.2%. (3) The relationship between Gibbs free energy and temperature of the reactions in the Si-C-0 system was calculated, and the lowest temperature of the reactions was determined. The calculated results were verified by HSC thermodynamic calculation software. The formation and decomposition reactions of iO and SiC occur only when the temperature is raised to 1900 C, and there are SiC, SiO2 and a small amount of SiO phases in the product. (4) The results show that it is feasible to melt silicon by using carbonized rice husk powder as carbon reducing agent, and the secondary industrial silicon with purity of 99.32wt% is obtained. The content of impurities in the product silicon is only 26 ppmw and 15 ppmw respectively, which are lower than that of phosphorus (120-200 ppmw) and boron (20-60 ppmw) in the existing industrial silicon. (5) When the mixed powders of carbonized rice husk powder and petroleum coke powder are used as carbon reductants, the results show that the suitable output voltage is 25-30V when the output current is stable at 500A, and the maximum yield of silicon is 30.7% when the additional carbon content is 30%, and the content of silicon in the bottom slag is also less. The content is 99.68 wt%, which has exceeded the national A-grade industrial silicon (chemical silicon) standard (Si%>99.60%). The main iron, aluminum and calcium impurities are lower than the existing national A-grade industrial silicon standard. The contents of phosphorus and boron are 24 ppmw and 14 ppmw respectively, which are also lower than the existing industrial silicon phosphorus and boron content. High-quality super-metallurgical grade silicon. (6) Study on phosphorus removal from metallurgical grade silicon by gas blowing refining. The results show that phosphorus in silicon melt decreases from 94 ppmw when using side wall and bottom porous nozzles, refining time is 3 hours, refining temperature is 1793 K, refining temperature is 373 K and refining gas velocity is 2 L/min. From thermodynamic and kinetic analysis, it can be concluded that water vapor in refining gas reacts with molten silicon to form silicon oxide and H2, and part of H2 dissolves in molten silicon. Then [H] in molten silicon reacts with [P] in molten silicon to form PH3, which is then taken away from molten silicon by argon bubbles. In this study, the preparation of super-metallurgical silicon from carbonized rice husk powder by electrothermal metallurgy was realized, which laid a foundation for the preparation of solar-grade polysilicon by electrothermal metallurgy with high-purity powder.
【學(xué)位授予單位】：東北大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN304.12
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