A method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-iron industrial silicon melt

Abstract

This invention relates to a method for preparing industrial silicon powder for organosilicon monomer synthesis from high-speed rail industrial silicon melt, belonging to the field of industrial silicon production technology. This invention addresses the practical problem of excessive Fe impurities in the melt after ladle refining of silicon melt, leading to high FeSi2 content in industrial silicon products and low selectivity for dimethyldichlorosilane when synthesizing organosilicon monomers using this industrial silicon as a raw material. By obtaining the content of the main metallic impurities in the high-speed rail type silicon melt after ladle refining, a quantitative alloying agent Al is added to adjust the composition of the silicon melt. After heat preservation, the melt is poured and the solidification rate is controlled to form a large amount of beneficial Si8Al6Fe4Ca phase, thus preparing industrial silicon powder for organosilicon monomer synthesis, thereby improving the selectivity and activity of the organosilicon monomer synthesis process. This invention has advantages such as no special requirements on the impurity content of the silicon melt, full utilization and energy saving, low infrastructure investment, simple process flow, high operability, and no environmental pollution.

Description

Technical Field

[0001] This invention relates to a method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt, belonging to the field of industrial silicon production technology. Background Technology

[0002] Industrial silicon is a crucial raw material for the preparation of silicon-based alloys, organosilicon monomers, and silicon-based photovoltaic cells. Both organosilicon and silicon-based photovoltaic cells require industrial silicon products with low impurity content. With the rapid consumption of high-quality low-Fe silica and reducing agents, and the inability of secondary refining to effectively remove Fe impurities from industrial silicon, the Fe impurity content in industrial silicon is expected to increase. In fact, high-iron industrial silicon, which has a higher yield and lower price, is essentially identical in composition to low-impurity industrial silicon, with only slight differences in impurity content. Furthermore, industrial silicon can be converted into organosilicon monomers via the Rochow-Müller method. Compared to the price differences between industrial silicon products with different Fe impurity contents, the difference in Si content between high-Fe industrial silicon and low-impurity industrial silicon is negligible, making the use of high-iron industrial silicon for organosilicon monomer synthesis possible.

[0003] Organosilicon monomers synthesized from industrial silicon include dimethyldichlorosilane, trimethylchlorosilane, and monomethyltrichlorosilane, among which dimethyldichlorosilane has the widest application, the largest usage, and the highest value. In industrial practice, selectivity and activity are commonly used to evaluate the quality of industrial silicon used in the synthesis of organosilicon monomers. Selectivity refers to the amount of dimethyldichlorosilane relative to other byproducts, and activity is the reaction rate of the industrial silicon synthesis of organosilicon monomers. Relevant literature and production experience show that the phase composition of industrial silicon can significantly affect the activity and selectivity of dimethyldichlorosilane synthesis. Typical phases in industrial silicon include FeSi2, CaSi2, Si2Al2Ca, TiFeSi2, Si2Al3Fe, Si7Al8Fe5, and Si8Al6Fe4Ca phases. Among them, Si2Al2Ca has a significant effect on improving activity, Si8Al6Fe4Ca is the only phase that can improve selectivity, Si2Al3Fe has no effect on selectivity and activity, and the remaining phases are all harmful phases relative to the synthesis of dimethyldichlorosilane from industrial silicon. After ladle refining, industrial silicon is classified into different grades based on differences in impurity content. High-iron industrial silicon, after solidification, will form a large amount of FeSi2, Si2Al2Ca, and a small amount of Si8Al6Fe4Ca phases, and may also contain Si2Al3Fe and Si7Al8Fe5. Therefore, to avoid the adverse effects of harmful phases in high-iron industrial silicon on the synthesis of dimethyldichlorosilane, organosilicon companies often purchase expensive, low-impurity industrial silicon to prepare organosilicon products, which to some extent reduces the competitiveness of these companies. Summary of the Invention

[0004] To address the practical problems of existing industrial silicon melts, such as unstable composition due to differences in smelting raw materials and refining processes, inability to match the requirements of industrial silicon for organosilicon applications, and low selectivity of high-Fe industrial silicon for organosilicon monomer synthesis, this invention proposes a method for preparing industrial silicon powder for organosilicon monomer synthesis from high-iron industrial silicon melts. Specifically, after obtaining the content of major metallic impurities in the high-iron type silicon melt during furnace refining, a quantitative alloying agent Al is added to adjust the composition of the silicon melt. After heat preservation, the melt is poured and the solidification rate is controlled to form a large amount of beneficial Si8Al6Fe4Ca, thus preparing industrial silicon powder for organosilicon monomer synthesis, thereby improving the selectivity and activity of the organosilicon monomer synthesis process.

[0005] A method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt, the specific steps of which are as follows:

[0006] (1) When the refining of high-speed iron type silicon melt outside the furnace is completed, the content of the main metal impurities in the high-speed iron type silicon melt is rapidly detected and analyzed. Among them, the mass ratio of Fe to Ca in the high-speed iron type silicon melt is >5.56; the main metal impurities include iron, aluminum, calcium, titanium, vanadium, nickel and manganese.

[0007] (2) The amount of alloying agent Al added is calculated based on the content of the main metallic impurities iron, aluminum, and calcium in the high-speed iron type silicon melt to control the melt composition; the formula for calculating the amount of alloying agent Al added is:

[0008] ;

[0009] In the formula, m Al Add to the required amount of silicon melt; m Fe m Ca m Al These represent the Fe, Ca, and Al impurity contents obtained after refining, respectively; M Fe M Ca M Al These are the relative atomic masses of Fe, Ca, and Al, respectively;

[0010] (3) According to the calculated amount of alloying agent Al, the alloying agent Al is added to the high-speed iron type silicon melt. The melt is kept warm in the refining furnace to make the melt composition uniform. Then the silicon melt is poured and the solidification rate of the silicon melt is controlled. After solidification, an industrial silicon ingot with controllable precipitate phase is obtained. The industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for the synthesis of organosilicon monomers.

[0011] Preferably, the alloying agent Al in step (2) includes, but is not limited to, Al-Si alloy, Al metal, and Al-Cu alloy.

[0012] Preferably, the temperature for heat preservation and refining in step (3) is 1450~1650℃ and the time is 10~60min.

[0013] Preferably, the solidification rate of the silicon melt in step (3) is: when the silicon melt temperature is higher than 500℃, the solidification rate of the silicon melt is 5~50℃ / min; when the silicon melt temperature is not higher than 500℃, it is naturally cooled and solidified.

[0014] Preferably, the Si8Al6Fe4Ca content in the industrial silicon powder used for synthesizing organosilicon monomers in step (4) is 0.10~0.50 wt.%, and the FeSi2 content is less than 0.60%.

[0015] The beneficial effects of this invention are:

[0016] (1) In view of the problems that the types and contents of phases precipitated from high-speed rail industrial silicon with the largest output are uncontrollable due to the difference in raw materials and refining processes during the existing industrial silicon furnace refining process, enterprises purchase expensive low-impurity industrial silicon to prepare organosilicon, and the phase growth is incomplete during casting and air cooling, this invention directly adds alloying agent Al to the high-speed rail industrial silicon after furnace refining based on the silicon melt composition adjustment and phase formation and transformation mechanism, according to the weight of the industrial silicon melt and its impurity content and ratio, to adjust the melt composition and keep it fully heated to make it fully mixed. At the same time, the casting solidification rate of the ingot is controlled and crushed and mixed, so as to achieve the purpose of controlling the phase and obtain industrial silicon products for organosilicon synthesis. It has the advantages of high product added value, strong raw material applicability, use of existing equipment or only simple modification, high production efficiency, and suitability for industrial production.

[0017] (2) The present invention uses alloying agent Al to adjust the melt composition, heat preservation in the furnace to make the melt composition uniform, casting and forming while controlling the solidification rate, crushing and powdering, etc., to prepare industrial silicon for synthesizing organic silicon under existing equipment or simple modification conditions. This avoids the problems of mismatch between the demand for industrial silicon and industrial silicon for organic silicon, and related enterprises purchasing expensive low-impurity industrial silicon to prepare organic silicon. It is conducive to increasing the added value of high-Fe type industrial silicon products.

[0018] (3) The industrial silicon prepared by this invention can improve the selectivity of synthesizing dimethyldichlorosilane monomers when used in the synthesis of organosilicon monomers. At the same time, there are no specific requirements for the composition of high-Fe type industrial silicon products. It plays a positive role in alleviating the tight supply of low-impurity industrial silicon materials, realizing the "cost reduction and efficiency improvement" of relevant enterprises, and improving resource utilization. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the present invention;

[0020] Figure 2The phase composition of the precipitated material in silicon from the high-speed rail industry in Example 1: (ab) before regulation; (cd) after regulation;

[0021] Figure 3 The phase content of high-speed rail industrial silicon obtained by combining typical X-ray diffraction analysis patterns of industrial silicon with Rietveld-refining and mass conservation in Example 1 is as follows: (a) High-speed rail industrial silicon before regulation; (b) High-speed rail industrial silicon after regulation. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0023] Example 1: A method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt (see...) Figure 1 The specific steps are as follows:

[0024] (1) When the high-speed iron type silicon melt is refined outside the furnace, the contents of the main metallic impurities iron, aluminum, calcium, titanium, vanadium, nickel and manganese in the high-speed iron type silicon melt are rapidly detected and analyzed. Among them, Fe is 3200 ppmw, Al is 1200 ppmw, Ca is 200 ppmw, Ti is 400 ppmw, V is 99 ppmw, Ni is 46 ppmw and Mn is 88 ppmw. The mass ratio of Fe to Fe in the high-speed iron type silicon melt is 16 > 5.56.

[0025] (2) The amount of alloying agent Al added is calculated based on the content of the main metallic impurities iron, aluminum, and calcium in the high-speed iron type silicon melt to control the melt composition; the alloying agent Al is added in the form of Al-Si alloy, and the calculation formula for the amount of alloying agent Al (calculated based on the Al content in the Al-Si alloy) added per ton of industrial silicon melt is as follows:

[0026] ;

[0027] In the formula, m Al Add to the required amount of silicon melt; m Fe m Ca m Al These represent the Fe, Ca, and Al impurity contents obtained after refining, respectively; M Fe M Ca M Al These are the relative atomic masses of Fe, Ca, and Al, respectively;

[0028] In this embodiment, the amount of alloying agent Al (calculated based on Al in Al-Si alloy) added is 2.63 kg / t;

[0029] (3) Based on the calculated amount of alloying agent Al added, Al-Si alloy is added to high-speed iron type silicon melt. The melt is kept at 1600℃ for 50 min in a refining furnace to make the melt composition uniform. Then the silicon melt is poured and the solidification rate of the silicon melt is controlled at 30℃ / min and cooled to 500℃. Then it is naturally cooled and solidified to room temperature. After solidification, an industrial silicon ingot with controllable precipitate phase is obtained. The industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for the synthesis of organosilicon monomers.

[0030] The phase composition of the silicon precipitated in the high-speed rail industry in this embodiment is shown below. Figure 2 , where (a) and (b) are before regulation, and (c) and (d) are after regulation; Figure 2 The results showed that before the high-speed rail type industrial silicon was regulated, a large amount of harmful FeSi2 and a small amount of beneficial Si8Al6Fe4Ca phase were precipitated; after the addition of 2.63 kg / t of alloying agent Al, more beneficial Si8Al6Fe4Ca and harmless Si2Al3Fe phase were precipitated, while the harmful FeSi2 phase almost disappeared.

[0031] The phase content obtained in this embodiment, based on typical X-ray diffraction patterns of industrial silicon combined with Rietveld-refining and mass conservation, is shown in the figure. Figure 3 , Figure 3 (a) represents silicon in the high-speed rail industry before regulation. Figure 3 (b) shows the high-speed rail industrial silicon after regulation. Further quantitative analysis of the content of intermetallic compounds showed that the content of FeSi2 precipitated before regulation ranged from 0.18 to 0.41%, and the content of Si8Al6Fe4Ca ranged from 0.08 to 0.16%. After alloy regulation, the content of FeSi2 was the highest at 0.006%, while the content of Si8Al6Fe4Ca ranged from 0.38 to 0.61%. The regulation process significantly reduced the content of harmful FeSi2 while increasing the content of beneficial Si8Al6Fe4Ca.

[0032] Example 2: A method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt (see...) Figure 1 The specific steps are as follows:

[0033] (1) When the high-speed iron type silicon melt is refined outside the furnace, the contents of the main metallic impurities iron, aluminum, calcium, titanium, vanadium, nickel and manganese in the high-speed iron type silicon melt are rapidly detected and analyzed. Among them, Fe is 5600 ppmw, Al is 2000 ppmw, Ca is 800 ppmw, Ti is 600 ppmw, V is 54 ppmw, Ni is 78 ppmw and Mn is 74 ppmw. The mass ratio of Fe to Fe in the high-speed iron type silicon melt is 7 > 5.56.

[0034] (2) The amount of alloying agent Al added is calculated based on the content of the main metallic impurities iron, aluminum, and calcium in the high-speed iron type silicon melt to control the melt composition; the alloying agent Al is added in the form of Al-Cu alloy, and the calculation formula for the amount of alloying agent Al (calculated based on the Al content in the Al-Cu alloy) added per ton of industrial silicon melt is as follows:

[0035] ;

[0036] In the formula, m Al Add to the required amount of silicon melt; m Fe m Ca m Al These represent the Fe, Ca, and Al impurity contents obtained after refining, respectively; M Fe M Ca M Al These are the relative atomic masses of Fe, Ca, and Al, respectively;

[0037] In this embodiment, the amount of alloying agent Al (calculated based on Al in Al-Si alloy) added is 2.89 kg / t;

[0038] (3) Based on the calculated amount of alloying agent Al, Al-Cu alloy is added to the high-speed iron type silicon melt. The melt is refined at 1550℃ in a refining furnace for 60 min to make the melt composition uniform. Then the silicon melt is poured and the solidification rate of the silicon melt is controlled at 20℃ / min and cooled to 500℃. Then it is naturally cooled and solidified to room temperature. After solidification, an industrial silicon ingot with controllable precipitate phase is obtained. The industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for the synthesis of organosilicon monomers.

[0039] In this embodiment, the main phases in the industrial silicon used for organosilicon are Si2Al3Fe and Si8Al6Fe4Ca. The content of Si8Al6Fe4Ca phase is increased from 0.18 wt.% to 0.41 wt.%, which can significantly improve the selectivity and activity of the organosilicon monomer synthesis process.

[0040] Example 3: A method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt (see...) Figure 1 The specific steps are as follows:

[0041] (1) When the high-speed iron type silicon melt is refined outside the furnace, the contents of the main metallic impurities iron, aluminum, calcium, titanium, vanadium, nickel and manganese in the high-speed iron type silicon melt are rapidly detected and analyzed. Among them, Fe is 5200 ppmw, Al is 3200 ppmw, Ca is 610 ppmw, Ti is 550 ppmw, V is 59 ppmw, Ni is 88 ppmw and Mn is 50 ppmw. The mass ratio of Fe to Fe in the high-speed iron type silicon melt is 8.52 > 5.56.

[0042] (2) The amount of alloying agent Al added is calculated based on the content of the main metallic impurities iron, aluminum, and calcium in the high-speed iron type silicon melt to control the melt composition; the alloying agent Al is added in the form of elemental Al metal, and the calculation formula for the amount of alloying agent Al (elemental Al) added per ton of industrial silicon melt is as follows:

[0043] ;

[0044] In the formula, m Al Add to the required amount of silicon melt; m Fe m Ca m Al These represent the Fe, Ca, and Al impurity contents obtained after refining, respectively; M Fe M Ca M Al These are the relative atomic masses of Fe, Ca, and Al, respectively;

[0045] In this embodiment, the amount of alloying agent Al (metallic Al element) added is 4.73 kg / t;

[0046] (3) Based on the calculated amount of alloying agent Al, Al-Cu alloy is added to high-speed iron type silicon melt. The melt is refined at 1650℃ in a refining furnace for 40 min to make the melt composition uniform. Then the silicon melt is poured and the solidification rate of the silicon melt is controlled at 15℃ / min and cooled to 500℃. Then it is naturally cooled and solidified to room temperature. After solidification, an industrial silicon ingot with controllable precipitate phase is obtained. The industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for the synthesis of organosilicon monomers.

[0047] In this embodiment, the main phases in the industrial silicon used for organosilicon are Si2Al3Fe and Si8Al6Fe4Ca. The content of Si8Al6Fe4Ca phase is increased from 0.12 wt.% to 0.38 wt.%, which can significantly improve the selectivity and activity of the organosilicon monomer synthesis process.

[0048] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt, characterized in that, The specific steps are as follows: (1) When the refining of high-speed iron type silicon melt outside the furnace is completed, the content of the main metal impurities in the high-speed iron type silicon melt is rapidly detected and analyzed. Among them, the mass ratio of Fe to Ca in the high-speed iron type silicon melt is >5.56; the main metal impurities include iron, aluminum, calcium, titanium, vanadium, nickel and manganese. (2) The amount of alloying agent Al added is calculated based on the content of the main metallic impurities iron, aluminum, and calcium in the high-speed iron type silicon melt to control the melt composition; the formula for calculating the amount of alloying agent Al added is: ； In the formula, m Al Add to the required amount of silicon melt; m Fe m Ca m Al These represent the Fe, Ca, and Al impurity contents obtained after refining, respectively; M Fe M Ca M Al These are the relative atomic masses of Fe, Ca, and Al, respectively; (3) According to the calculated amount of alloying agent Al, the alloying agent Al is added to the high-speed iron type silicon melt. The melt is kept warm and refined in the refining furnace to make the melt composition uniform. Then the silicon melt is poured and the solidification rate of the silicon melt is controlled. After solidification, an industrial silicon ingot with controllable precipitate phase is obtained. The industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for the synthesis of organosilicon monomers.

2. The method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt according to claim 1, characterized in that: The heat preservation temperature in step (3) is 1450~1650℃, and the time is 10~60min.

3. The method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt according to claim 1, characterized in that: The solidification rate of the silicon melt in step (3) is as follows: when the temperature of the silicon melt is higher than 500℃, the solidification rate of the silicon melt is 5~50℃ / min; when the temperature of the silicon melt is not higher than 500℃, it will solidify naturally by cooling.

4. The method for preparing industrial silicon powder for synthesizing organosilicon monomers from high-speed rail industrial silicon melt according to claim 1, characterized in that: In step (3), the industrial silicon powder used for synthesizing organosilicon monomers contains 0.10~0.50 wt.% Si8Al6Fe4Ca and less than 0.60% FeSi2.

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