Method for preparing industrial silicon powder for synthesizing organic silicon monomer from high-iron industrial silicon melt

Abstract

The invention relates to a method for preparing industrial silicon powder for organic silicon monomer synthesis from high-iron industrial silicon melt, and belongs to the technical field of industrial silicon production. Based on the practical problems that the content of FeSi2 in an industrial silicon product is high due to the fact that the content of Fe impurities in the melt is too high after the silicon melt is subjected to external refining, and the selectivity of dimethyldichlorosilane is low when the industrial silicon is used as a raw material to synthesize an organic silicon monomer, the method comprises the following steps: obtaining the content of main metal impurities in the high-iron type silicon melt after the silicon melt is subjected to external refining; the preparation method comprises the following steps: adding an alloying agent Al quantitatively to adjust the components of a silicon melt, pouring and controlling the solidification rate of the silicon melt after heat preservation is finished, so that a large amount of beneficial Si8Al6Fe4Ca phases are formed, and the industrial silicon powder for synthesizing the organic silicon monomer is prepared to improve the selectivity and activity of the synthesis process of the organic silicon monomer. The method has the advantages of no special requirement on the impurity content of the silicon melt, full utilization and energy conservation, low capital construction investment, simple process flow, high operability, no environmental pollution and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-speed iron industrial silicon melt, belonging to the technical field of industrial silicon production. Background Art

[0002] Industrial silicon is an important basic raw material for the preparation of silicon-based alloys, organosilicon monomers and silicon-based photovoltaic cells, among which organosilicon and silicon-based photovoltaic cells both 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 in industrial silicon, the Fe impurity content in industrial silicon will show an upward trend. In fact, high-iron industrial silicon with higher output and lower price and low-impurity industrial silicon are basically the same in composition, with only slight differences in impurity content. In addition, industrial silicon converts Si into organosilicon monomers through the Rochow-Müller method. Compared with the price difference 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 insignificant, which makes it possible to use high-iron industrial silicon for the synthesis of organosilicon monomers.

[0003] The organosilicon monomers synthesized from industrial silicon include dimethyldichlorosilane, trimethylchlorosilane and monomethyltrichlorosilane, among which dimethyldichlorosilane has the widest application, the largest dosage and the highest value. In industrial practice, when synthesizing organosilicon monomers from industrial silicon, selectivity and activity are usually used to evaluate the quality of industrial silicon for organosilicon. Selectivity refers to the amount of dimethyldichlorosilane relative to other by-products, and activity refers to the reaction rate of industrial silicon synthesizing organosilicon monomers. Relevant literature and production experience show that the physical phases in industrial silicon can seriously affect the activity and selectivity of industrial silicon synthesizing dimethyldichlorosilane. Typical physical phases in industrial silicon specifically 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 harmful phases for the synthesis of dimethyldichlorosilane from industrial silicon. After refining outside the furnace, industrial silicon is classified into different grades according to the difference in impurity content. Among them, a large amount of FeSi2, Si2Al2Ca and a small amount of Si8Al6Fe4Ca phases will be formed in high-speed iron industrial silicon after solidification, and Si2Al3Fe and Si7Al8Fe5 may exist. Therefore, in order to avoid the adverse effects of harmful phases in high-speed iron industrial silicon on the synthesis of dimethyldichlorosilane, silicone companies often purchase expensive industrial silicon with low impurity content to prepare silicone products, which to a certain extent reduces the competitiveness of related companies. Summary of the invention

[0004] In view of the practical problems that the existing industrial silicon melt has unstable composition due to differences in smelting raw materials and refining processes, cannot match the use demand of industrial silicon for silicone, and has low selectivity of high-Fe industrial silicon for silicone monomer synthesis, the present invention proposes a method for preparing industrial silicon powder for silicone monomer synthesis from high-iron industrial silicon melt, that is, after obtaining the main metal impurity content in the high-iron silicon melt when refining outside the silicon melt furnace is completed, alloying agent Al is quantitatively added to adjust the composition of the silicon melt, and after the insulation is completed, the silicon melt is poured and the solidification rate is controlled to form a large amount of beneficial Si8Al6Fe4Ca, so as to prepare industrial silicon powder for silicone monomer synthesis, so as to improve the selectivity and activity of the silicone monomer synthesis process.

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

[0006] (1) After the refining of high-iron silicon melt is completed, the content of the main metal impurities in the high-iron silicon melt is quickly detected and analyzed, wherein the mass ratio of Fe to Ca in the high-iron silicon melt is greater than 5.56; the main metal impurities include iron, aluminum, calcium, titanium, vanadium, nickel and manganese;

[0007] (2) Calculate the amount of alloying agent Al added according to the content of the main metal impurities iron, aluminum and calcium in the high-iron silicon melt to control the melt composition; the calculation formula for the amount of alloying agent Al added is:

[0008]

[0009] In the formula, m Al Addition is the content that needs to be added to the silicon melt; m Fe 、m Ca 、m Al are the impurity contents of Fe, Ca and Al obtained after refining; M Fe 、M Ca 、M Al are the relative atomic masses of Fe, Ca, and Al respectively;

[0010] (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high-iron silicon melt, and the melt is kept warm 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. 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 synthesizing organic silicon 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 of the heat preservation and refining in step (3) is 1450-1650° C., and the time is 10-60 min.

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

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

[0015] The beneficial effects of the present invention are:

[0016] (1) In view of the problems that the types and contents of the phases of the high-iron industrial silicon with the largest yield obtained during the off-furnace refining of existing industrial silicon are uncontrollable due to the differences in raw materials and refining processes, enterprises purchase expensive low-impurity industrial silicon to prepare organic silicon, and the phase growth is not thorough during pouring and air cooling, the present invention directly adds alloying agent Al to the high-iron industrial silicon melt after off-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 proportion, to adjust the melt composition and fully keep the temperature to make it fully mixed, and while casting and forming, controls the solidification rate of the ingot, crushes and mixes it, and finally achieves the purpose of controlling the phase, thereby obtaining an industrial silicon product for organic silicon synthesis, which 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 adopts the alloying agent Al to adjust the melt composition, the furnace heat preservation to make the melt composition uniform, the casting and forming while controlling the solidification rate, the crushing and powder making and other means, to prepare industrial silicon for synthetic organic under the conditions of existing equipment or simple modification, avoiding the problems of the mismatch between the demand for industrial silicon and industrial silicon for organic silicon, and the related enterprises purchasing expensive low-impurity content industrial silicon for preparing organic silicon, which is conducive to increasing the added value of high-Fe industrial silicon products;

[0018] (3) The industrial silicon prepared by the present invention can be used for the synthesis of organic silicon monomers to improve the selectivity of synthesizing dimethyldichlorosilane monomers. At the same time, there is no clear requirement for the composition of high-Fe industrial silicon products, which has a positive effect on alleviating the tight supply of industrial silicon materials with low impurity content, achieving "cost reduction and efficiency improvement" for related enterprises, and improving resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention;

[0020] Figure 2The phase components precipitated in the high-speed iron industrial silicon in Example 1: (ab) before regulation; (cd) after regulation;

[0021] Figure 3 This is Example 1 based on the typical X-ray diffraction analysis spectrum of industrial silicon combined with Rietveld-refining and mass conservation to obtain the phase content: (a) high-speed iron industrial silicon before regulation; (b) high-speed iron industrial silicon after regulation. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0023] Example 1: A method for preparing industrial silicon powder for synthesizing organic silicon monomer from high-speed iron industrial silicon melt (see Figure 1 ), the specific steps are as follows:

[0024] (1) After the high-iron silicon melt is refined outside the furnace, the contents of the main metal impurities iron, aluminum, calcium, titanium, vanadium, nickel and manganese in the high-iron silicon melt are quickly detected and analyzed, wherein Fe is 3200ppmw, Al is 1200ppmw, Ca is 200ppmw, Ti is 400ppmw, V is 99ppmw, Ni is 46ppmw, Mn is 88ppmw, and the mass ratio of Fe to Fe in the high-iron silicon melt is 16>5.56;

[0025] (2) Calculating the amount of alloying agent Al added according to the contents of the main metal impurities iron, aluminum and calcium in the high-iron 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 added per ton of industrial silicon melt (calculated based on the Al content in the Al-Si alloy) is:

[0026]

[0027] In the formula, m Al Addition is the content that needs to be added to the silicon melt; m Fe 、m Ca 、m Al are the impurity contents of Fe, Ca and Al obtained after refining; M Fe 、M Ca 、M Al are the relative atomic masses of Fe, Ca, and Al respectively;

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

[0029] (3) According to the calculated addition amount of alloying agent Al, Al-Si alloy is added to the high-iron silicon melt, and the melt is kept at 1600°C in a refining furnace for 50 minutes to make the melt composition uniform, and then the silicon melt is poured and the solidification rate of the silicon melt is controlled to be 30°C / min and cooled to 500°C, and then naturally cooled and solidified to room temperature. After the solidification is completed, an industrial silicon ingot with controllable precipitate phase is obtained, and the industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for synthesis of organic silicon monomer;

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

[0031] This example is based on the typical X-ray diffraction analysis of industrial silicon, combined with Rietveld-refining and mass conservation to obtain the phase content. Figure 3 , Figure 3 (a) is the high-speed rail industrial silicon before regulation. Figure 3 Middle (b) is high-speed iron industrial silicon after regulation; further quantitative analysis of the content of intermetallic compounds shows that the content of FeSi2 precipitated in high-speed iron industrial silicon before regulation ranges from 0.18% to 0.41%, and the content of Si8Al6Fe4Ca ranges from 0.08% to 0.16%; after adding alloy regulation, the content of FeSi2 is as high as 0.006%, while the content of Si8Al6Fe4Ca ranges from 0.38% to 0.61%; the regulation process significantly reduces the content of harmful FeSi2, while increasing the content of beneficial Si8Al6Fe4Ca.

[0032] Example 2: A method for preparing industrial silicon powder for synthesizing organic silicon monomer from high-speed iron industrial silicon melt (see Figure 1 ), the specific steps are as follows:

[0033] (1) After the high-iron silicon melt is refined outside the furnace, the contents of the main metal impurities iron, aluminum, calcium, titanium, vanadium, nickel and manganese in the high-iron silicon melt are quickly detected and analyzed, wherein Fe is 5600ppmw, Al is 2000ppmw, Ca is 800ppmw, Ti is 600ppmw, V is 54ppmw, Ni is 78ppmw, Mn is 74ppmw, and the mass ratio of Fe to Fe in the high-iron silicon melt is 7>5.56;

[0034] (2) Calculating the amount of alloying agent Al added according to the contents of the main metal impurities iron, aluminum and calcium in the high-iron 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 added per ton of industrial silicon melt (calculated based on the Al content in the Al-Cu alloy) is:

[0035]

[0036] In the formula, m Al Addition is the content that needs to be added to the silicon melt; m Fe 、m Ca 、m Al are the impurity contents of Fe, Ca and Al obtained after refining; M Fe 、M Ca 、M Al are the relative atomic masses of Fe, Ca, and Al respectively;

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

[0038] (3) According to the calculated addition amount of alloying agent Al, Al-Cu alloy is added to the high-iron silicon melt, and the melt is kept and refined at 1550°C in a refining furnace for 60 minutes to make the melt composition uniform, and then the silicon melt is poured and the solidification rate of the silicon melt is controlled to be 20°C / min and cooled to 500°C, and then naturally cooled and solidified to room temperature. After the solidification is completed, an industrial silicon ingot with controllable precipitate phase is obtained, and the industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for synthesis of organic silicon monomer;

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

[0040] Example 3: A method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-speed iron industrial silicon melt (see Figure 1 ), the specific steps are as follows:

[0041] (1) After the high-iron silicon melt is refined outside the furnace, the contents of the main metal impurities iron, aluminum, calcium, titanium, vanadium, nickel and manganese in the high-iron silicon melt are quickly detected and analyzed, wherein Fe is 5200ppmw, Al is 3200ppmw, Ca is 610ppmw, Ti is 550ppmw, V is 59ppmw, Ni is 88ppmw, Mn is 50ppmw, and the mass ratio of Fe to Fe in the high-iron silicon melt is 8.52>5.56;

[0042] (2) Calculating the amount of alloying agent Al added according to the contents of the main metal impurities iron, aluminum and calcium in the high-iron silicon melt to control the melt composition; the alloying agent Al is added in the form of metallic Al alone, and the calculation formula for the amount of alloying agent Al (Al alone) added per ton of industrial silicon melt is:

[0043]

[0044] In the formula, m Al Addition is the content that needs to be added to the silicon melt; m Fe 、m Ca 、m Al are the impurity contents of Fe, Ca and Al obtained after refining; M Fe 、M Ca 、M Al are the relative atomic masses of Fe, Ca, and Al respectively;

[0045] The addition amount of alloying agent Al (metal Al single substance) in this embodiment is 4.73 kg / t;

[0046] (3) According to the calculated addition amount of alloying agent Al, Al-Cu alloy is added to the high-iron silicon melt, and the melt is kept and refined at 1650°C in a refining furnace for 40 minutes to make the melt composition uniform, and then the silicon melt is poured and the solidification rate of the silicon melt is controlled to be 15°C / min and cooled to 500°C, and then naturally cooled and solidified to room temperature. After the solidification is completed, an industrial silicon ingot with controllable precipitate phase is obtained, and the industrial silicon ingot is crushed and powdered to obtain industrial silicon powder for synthesis of organic silicon monomer;

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

[0048] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-speed iron industrial silicon melt, characterized in that: The specific steps are as follows: (1) After the refining of high-iron silicon melt is completed, the content of the main metal impurities in the high-iron silicon melt is quickly detected and analyzed, where the mass ratio of Fe to Ca in the high-iron silicon melt is greater than 5.56; the main metal impurities include iron, aluminum, calcium, titanium, vanadium, nickel and manganese; (2) According to the contents of the main metal impurities iron, aluminum and calcium in the high-iron silicon melt, the addition amount of the alloying agent Al is calculated to control the melt composition; the calculation formula for the addition amount of the alloying agent Al is: ； In the formula, mAl Addition is the content required to be added to the silicon melt; mFe , mCa , mAl are the impurity contents of Fe, Ca and Al obtained after refining; MFe , MCa , MAl are the relative atomic masses of Fe, Ca, and Al respectively; (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high-iron silicon melt, and the melt is kept warm and refined in a refining furnace to make the melt composition uniform. The silicon melt is then 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 synthesizing organic silicon monomers.

2. The method for preparing industrial silicon powder for synthesizing organic silicon monomer from high-speed iron industrial silicon melt according to claim 1, characterized in that: The insulation temperature of step (3) is 1450-1650° C. and the insulation time is 10-60 min.

3. The method for preparing industrial silicon powder for synthesizing organic silicon monomer from high-speed iron industrial silicon melt according to claim 1, characterized in that: The solidification rate of the silicon melt in step (3) is: when the temperature of the silicon melt is higher than 500°C, the solidification rate of the silicon melt is 5-50°C / min; when the temperature of the silicon melt is not higher than 500°C, it is naturally cooled and solidified.

4. The method for preparing industrial silicon powder for synthesizing organic silicon monomer from high-speed iron industrial silicon melt according to claim 1, characterized in that: In the step (4), the industrial silicon powder used for synthesizing the organosilicon monomer Si8Al6Fe4Ca Content is 0.10~0.50wt.%, FeSi2 The content is less than 0.60%.

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