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

Abstract

The invention relates to a method for preparing industrial silicon powder for organic silicon monomer synthesis from high-calcium industrial silicon melt, and belongs to the technical field of industrial silicon production. Based on the practical problems that the content of CaSi2 in an industrial silicon product is high due to the fact that the content of Ca 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-calcium silicon melt after the silicon melt is subjected to external refining; the preparation method comprises the following steps: quantitatively adding an alloying agent Al to adjust the components of a silicon melt, carrying out heat preservation and refining, pouring, and controlling the solidification rate of the silicon melt, so that a large amount of beneficial Si8Al6Fe4Ca and Si2Al2Ca phases are formed, and meanwhile, the precipitation of a harmful inclusion phase CaSi2 is avoided, and the industrial silicon powder for synthesizing the organic silicon monomer is prepared, so that the selectivity and activity of the synthesis process of the organic silicon monomer are improved.

Description

Technical Field

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

[0002] Industrial silicon is the basic raw material for silicon-based alloys, organic silicon and silicon-based photovoltaic cells. The industrial silicon raw materials required for organic silicon are required to have low Fe, Ca and other characteristics. However, with the rapid development of the organic silicon and photovoltaic industries, the demand and price of industrial silicon with low impurity content have shown a rapid growth trend, which has seriously affected the competitiveness of organic silicon companies. In fact, for industrial silicon, the composition of high-calcium industrial silicon and industrial silicon with low impurity content is basically the same, with only a slight difference in impurity content, which makes it possible to use high-calcium industrial silicon for the synthesis of organic silicon 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. 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 synthesizing dimethyldichlorosilane. Relevant literature and production experience show that the physical phases in industrial silicon can seriously affect the activity and selectivity of dimethyldichlorosilane synthesized from industrial silicon. The 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 but is not conducive to improving selectivity. 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. Therefore, industrial silicon can achieve a balance between selectivity and activity by adjusting the relative content of Si2Al2Ca and Si8Al6Fe4Ca. However, after the solidification of high-calcium industrial silicon, a large amount of CaSi2, FeSi2, Si2Al2Ca and a small amount of Si8Al6Fe4Ca phases will be formed. From the perspective of physical phases, CaSi2 and FeSi2 are not conducive to the synthesis of organosilicon monomers. In order to avoid the influence of harmful phases in high-calcium industrial silicon on the synthesis of dimethyldichlorosilane, organosilicon companies tend to purchase expensive industrial silicon with low impurity content to prepare organosilicon products, which to a certain extent weakens the profitability of related companies. Summary of the invention

[0004] Aiming at the practical problems such as the unstable phase composition and content of high-calcium industrial silicon precipitated due to the characteristics of smelting raw materials, the low added value of high-calcium industrial silicon, and the low yield of dimethyldichlorosilane caused by a large amount of CaSi2 in the synthesis of organic silicon monomers by high-calcium industrial silicon, the present invention proposes a method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-calcium industrial silicon melt, that is, after obtaining the main metal impurity content in the high-calcium silicon melt after refining outside the silicon melt furnace, based on The transformation mechanism of intermetallic compounds and the calculation formula for the amount of alloying agent (Al) were studied. , alloying agent Al is quantitatively added to adjust the composition of the silicon melt, and after heat preservation and refining, the silicon melt is poured and the solidification rate is controlled to form a large number of beneficial Si8Al6Fe4Ca and Si2Al2Ca phases, while avoiding the precipitation of harmful inclusion phase CaSi2, and preparing industrial silicon powder for organosilicon monomer synthesis to improve the selectivity and activity of the organosilicon monomer synthesis process.

[0005] In view of the fact that the current off-furnace refining industry has poor effect on removing Fe and Ti impurities, but better effect on Al and Ca, the present invention comprehensively considers the influence of various phases in industrial silicon on the efficiency of synthesizing dimethyldichlorosilane and adopts Al to fine-tune the composition to achieve the purpose of targeted regulation of phases. After adding Al for targeted regulation, the CaSi2 and FeSi2 phases disappear, and the impurity components will completely form Si8Al6Fe4Ca and Si2Al2Ca phases, which is conducive to the selectivity and activity of the synthesis process of organic silicon monomers.

[0006] A method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-calcium industrial silicon melt, the specific steps are as follows:

[0007] (1) After the high-calcium silicon melt is refined outside the furnace, the content of the main metal impurities in the high-calcium silicon melt is quickly analyzed, wherein the mass ratio of Fe to Ca in the high-calcium silicon melt is less than 5.56; the main metal impurities include iron, aluminum, calcium, titanium, vanadium, nickel and manganese;

[0008] (2) calculating the amount of alloying agent Al to be added based on the contents of the main metal impurities iron, aluminum, and calcium in the high-calcium silicon melt to control the melt composition;

[0009] (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high-calcium 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.

[0010] The calculation formula for the addition amount of the alloying agent Al in step (2) is:

[0011]

[0012] In the formula, mAl Addition amount is the amount of silicon melt to be added; 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;

[0013] Preferably, the temperature of the heat preservation and refining in step (3) is 1450-1650° C., and the time is 10-60 min.

[0014] Preferably, the solidification rate of the silicon melt in step (3) is: when the temperature of the silicon melt is higher than 700°C, the solidification rate of the silicon melt is 5-50°C / min; when the temperature of the silicon melt is not higher than 700°C, it is naturally cooled and solidified.

[0015] The content of Si8Al6Fe4Ca in the industrial silicon powder used for synthesizing the organosilicon monomer in the step (4) is 0.10-0.60wt.%, and the content of CaSi2 is less than 0.30%.

[0016] The beneficial effects of the present invention are:

[0017] (1) In view of the problems that the physical composition of high-calcium industrial silicon is uncontrollable due to differences in raw materials and refining processes during the existing off-furnace refining of industrial silicon, enterprises purchase expensive industrial silicon with low impurity content to prepare organosilicon, and the physical phase growth is not thorough during pouring and air cooling, the present invention directly adds alloying agent Al to the industrial silicon melt after off-furnace refining according to the weight of the industrial silicon melt and its impurity content and proportion to adjust the melt composition and fully insulate it to make it fully mixed, and then pour it to solidify. After the silicon melt is poured, the controlled formation of the physical phase is achieved under the premise of controlling the solidification rate. After the solidification is completed, the industrial silicon product for organosilicon synthesis is obtained after crushing and powdering. The product has the advantages of high added value, strong raw material applicability, use of existing equipment or only simple modification, high production efficiency, and suitability for industrial production;

[0018] (2) The present invention adopts the methods of adding alloying agent Al metal to adjust the melt composition, heat preservation in the furnace to make the melt composition uniform, casting and forming while controlling the cooling rate, crushing and powder making, etc., to prepare industrial silicon for synthetic organic under the conditions of existing equipment or simple modification, thereby improving the efficiency of synthesizing dimethyldichlorosilane from high-calcium industrial silicon, avoiding the problem of related enterprises purchasing expensive low-impurity content industrial silicon to prepare organic silicon, and is conducive to increasing the added value of high-calcium industrial silicon products;

[0019] (3) The industrial silicon prepared by the present invention can be used for the synthesis of organic silicon monomers to improve the production efficiency of dimethyldichlorosilane monomers. At the same time, there is no specific requirement for the impurity content of high-calcium industrial silicon products. It has a positive effect on alleviating the tight supply of low-impurity industrial silicon materials, achieving "cost reduction and efficiency improvement" for related enterprises, and improving resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the present invention;

[0021] Figure 2 EPMA microscopic images of typical high-calcium industrial silicon before and after solidification in Example 1;

[0022] Figure 3 The typical X-ray diffraction analysis pattern and Rietveld-refining of the top of the ingot (2.5wt.%) after directional solidification before and after typical high-calcium industrial silicon regulation in Example 1;

[0023] Figure 4 This is the intermetallic compound content obtained by maintaining mass at the top of the ingot (2.5 wt.%) after directional solidification before and after regulation of typical high-calcium industrial silicon in Example 1. DETAILED DESCRIPTION

[0024] 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.

[0025] Example 1: A method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-calcium industrial silicon melt (see Figure 1 ), the specific steps are as follows:

[0026] (1) After the high-calcium 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-calcium silicon melt are quickly analyzed, wherein Fe is 4100ppmw, Al is 2000ppmw, Ca is 1200ppmw, Ti is 600ppmw, V is 200ppmw, Ni is 122ppmw, Mn is 87ppmw, and the mass ratio of Fe to Ca in the high-calcium silicon melt is 3.417<5.56;

[0027] (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-calcium silicon melt to control the melt composition; the calculation formula for the amount of alloying agent Al added is:

[0028]

[0029] In the formula, m Al Addition amount is the amount of silicon melt to be added; 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;

[0030] The addition amount of alloying agent Al in this embodiment is 1.60 kg / t;

[0031] (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high-calcium silicon melt, and the melt is kept and refined at 1600° C. in a refining furnace for 40 min 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 700° 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;

[0032] The EPMA microscopic images of typical high calcium industrial silicon before and after solidification are shown in the figure. Figure 2 Typical X-ray diffraction analysis pattern and Rietveld-refining of the top of the ingot (2.5wt.%) after directional solidification before and after typical high-calcium industrial silicon regulation Figure 3 ; Typical high calcium industrial silicon before and after directional solidification ingot top (2.5wt.%) mass conservation obtained by intermetallic compound content Figure 4 As can be seen from the figure, the CaSi2 phase content in industrial silicon for organosilicon is reduced from 0.25wt.% to almost disappear, and the Si8Al6Fe4Ca phase content is increased from 0.20wt.% to 0.60wt.%, which greatly reduces the content of harmful phases and can improve the selectivity and activity of the organosilicon monomer synthesis process.

[0033] Example 2: A method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-calcium industrial silicon melt (see Figure 1 ), the specific steps are as follows:

[0034] (1) When the high-calcium 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-calcium silicon melt are quickly analyzed, wherein Fe is 3092 ppmw, Al is 1084 ppmw, Ca is 1038 ppmw, Ti is 494 ppmw, V is 172 ppmw, Ni is 175 ppmw, Mn is 265 ppmw, and the mass ratio of Fe to Ca in the high-calcium silicon melt is 2.98<5.56;

[0035] (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-calcium silicon melt to control the melt composition; the calculation formula for the amount of alloying agent Al added is:

[0036]

[0037] In the formula, m Al Addition amount is the amount of silicon melt to be added; 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;

[0038] The addition amount of alloying agent Al in this embodiment is 1.81 kg / t;

[0039] (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high calcium silicon melt, and the melt is kept and refined at 1630° C. in a refining furnace for 60 min 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 700° 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;

[0040] In this embodiment, the CaSi2 phase content in the industrial silicon for organosilicon is reduced from 0.26wt.% to almost disappearance, and the Si8Al6Fe4Ca phase content is increased from 0.23wt.% to 0.56wt.%, which greatly reduces the content of harmful phases and can improve the selectivity and activity of the organosilicon monomer synthesis process.

[0041] Example 3: A method for preparing industrial silicon powder for synthesizing organic silicon monomers from high-calcium industrial silicon melt (see Figure 1 ), the specific steps are as follows:

[0042] (1) After the high-calcium 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-calcium silicon melt are quickly analyzed, wherein Fe is 4100 ppmw, Al is 1483 ppmw, Ca is 3877 ppmw, Ti is 380 ppmw, V is 158 ppmw, Ni is 128 ppmw, Mn is 287 ppmw, and the mass ratio of Fe to Ca in the high-calcium silicon melt is 1.06<5.56;

[0043] (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-calcium silicon melt to control the melt composition; the calculation formula for the amount of alloying agent Al added is:

[0044]

[0045] In the formula, m Al Addition amount is the amount of silicon melt to be added; 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;

[0046] The addition amount of alloying agent Al in this embodiment is 5.73 kg / t;

[0047] (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high-calcium silicon melt, and the melt is kept and refined at 1630° C. in a refining furnace for 50 min 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 25° C. / min and cooled to 700° 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;

[0048] In this embodiment, the CaSi2 phase content in the industrial silicon for organosilicon is reduced to almost disappear, and the Si8Al6Fe4Ca phase content is increased from 0.17wt.% to 0.51wt.%, which greatly reduces the content of harmful phases and can improve the selectivity and activity of the organosilicon monomer synthesis process.

[0049] 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-calcium industrial silicon melt, characterized in that: The specific steps are as follows: (1) After the high-calcium silicon melt is refined outside the furnace, the content of the main metal impurities in the high-calcium silicon melt is quickly analyzed, wherein the mass ratio of Fe to Ca in the high-calcium silicon melt is less than 5.56; the main metal impurities include iron, aluminum, calcium, titanium, vanadium, nickel and manganese; (2) calculating the amount of alloying agent Al to be added based on the contents of the main metal impurities iron, aluminum, and calcium in the high-calcium silicon melt to control the melt composition; (3) According to the calculated addition amount of alloying agent Al, the alloying agent Al is added to the high-calcium 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 calcium industrial silicon melt according to claim 1, characterized in that: The calculation formula for the addition amount of the alloying agent Al in step (2) is: In the formula, m Al Addition amount is the amount of silicon melt to be added; m Fe 、m Ca 、m Al are the impurity contents of Fe, Ca and Al obtained after refining; M Fe 、M Ca 、M Al Then they are the relative atomic masses of Fe, Ca, and Al respectively.

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

4. The method for preparing industrial silicon powder for synthesizing organic silicon monomer from high calcium type 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 700°C, the solidification rate of the silicon melt is 5-50°C / min; when the temperature of the silicon melt is not higher than 700°C, it is naturally cooled and solidified.

5. The method for preparing industrial silicon powder for synthesizing organic silicon monomer from high calcium industrial silicon melt according to claim 1, characterized in that: The content of Si8Al6Fe4Ca in the industrial silicon powder used for synthesizing the organosilicon monomer in the step (4) is 0.10-0.60wt.%, and the content of CaSi2 is less than 0.30%.

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