Method and system for preparing trichlorosilane from silicon iron

Abstract

The invention relates to a method and a system for preparing trichlorosilane from ferrosilicon, the method comprises the following steps: taking ferrosilicon, silicon tetrachloride and hydrogen as raw materials, fully reacting in a fluidized bed reactor to obtain trichlorosilane and FeSiy alloy, xlt; 40). The system comprises a fluidized bed reactor (200), a cyclone separator (300), a washing tower (400), a gas-liquid separator (500) and a coarse distillation tower (600). Compared with the prior art, the method has the remarkable characteristics that the silazite is used as a silicon source and is low in cost and easy to obtain, the reaction activity of trichlorosilane and FeSiy generated by reaction of the silazite, silicon tetrachloride and hydrogen is high, the utilization rate of silicon elements in the compound is high, no extra catalyst needs to be added in the co-hydrogenation reaction, meanwhile, the byproduct FeSiy alloy is produced, and the production cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polycrystalline silicon production process, and particularly relates to a method and system for preparing trichlorosilane from ferrosilicon. BACKGROUND

[0002] Silicon material, especially high-purity polycrystalline silicon, is the most basic raw material in the semiconductor industry and the photovoltaic industry. At present, the most mainstream process for industrial production of high-purity polycrystalline silicon is the trichlorosilane reduction method, but more than 10 tons of silicon tetrachloride by-product will be produced for every ton of polycrystalline silicon. As the main by-product in the polycrystalline silicon production process, silicon tetrachloride is a highly toxic substance. If it cannot be recycled and treated, not only will it seriously pollute the environment, but also will cause resource waste. Through the co-hydrogenation of silicon tetrachloride and silicon, the silicon tetrachloride is re-converted into trichlorosilane raw material. Not only can the silicon tetrachloride be recycled, but also it is an environmentally friendly and atom-economical green chemical production path.

[0003] Currently, the mainstream method for preparing trichlorosilane from silicon tetrachloride is cold hydrogenation method, that is, silicon tetrachloride and metallurgical silicon are co-hydrogenated under the action of a catalyst, and the reaction temperature is 400-600℃, which has the advantages of low energy consumption and low cost. The key technology in the process of preparing trichlorosilane from silicon tetrachloride by cold hydrogenation is to develop a catalyst with high activity, long service life and low cost, and to improve the single conversion rate of silicon powder. At present, most of the cold hydrogenation production processes use cuprous chloride (Industrial & Engineering Chemistry Research 53(43):16725-16735) catalyst, which is simply pre-mixed with metallurgical silicon powder before cold hydrogenation reaction. The price of cuprous chloride catalyst is cheap, but the simple mechanical mixing makes the contact between silicon powder and catalyst loose and the mixture uneven, resulting in problems such as long induction period of cuprous chloride catalytic activity, poor thermal stability, easy loss, and low single conversion rate of silicon powder. In the actual production process, it is necessary to continuously add cuprous chloride catalyst to maintain the reaction activity, resulting in high production cost of silicon tetrachloride cold hydrogenation reaction. There are also some patents on the modification of silicon tetrachloride catalyst. CN114558593A discloses a method for improving catalytic activity by using different metal chlorides instead of single cuprous chloride, but this method has the problems of complex catalyst components and easy loss of active components. CN109718781A provides a silicon tetrachloride hydrogenation catalyst, the catalyst composition includes silicon dioxide, aluminum oxide, active component and additive, the active component is Ni or Co, and the additive is one or more of Cu, Fe, Cr and Ba, the catalyst components are complex, and expensive Ni or Co is used as the active metal. CN108283925A also discloses a catalyst using Ni or Co as the active metal for silicon tetrachloride hydrogenation. CN103754883A discloses a catalyst for preparing trichlorosilane by hydrogenation and dechlorination of silicon tetrachloride, which selects nickel, copper and palladium as the main active components of the hydrogenation and dechlorination catalyst, and uses activated carbon as the carrier. The raw materials of the catalyst are expensive, the preparation steps are complex, and the activated carbon carrier is easy to wear in the fluidized bed reactor, causing catalyst loss, which is not suitable for industrial production. CN114011451A discloses a copper-silicon catalyst, which includes a carrier and an active component, the active component is a silicon-copper multi-component compound containing Cu and Si elements, and at least one of Cr, Ni, Mo, Ti, Zr, Ce, La and Sc, and the carrier includes at least one of quartz powder, corundum powder, fly ash, coal gangue, clay mineral and kaolin. The components and preparation process of the catalyst are complex, and too many metal components are not conducive to obtaining high-purity products. Chinese patent CN102909006A discloses a catalyst for preparing trichlorosilane by reacting silicon tetrachloride with hydrogen, the active component of the catalyst is nano platinum particles, and the carrier is silicon dioxide. As we all know, platinum metal is expensive, which leads to high cost of the catalyst.Centersum photovoltaic America limited company announced silicide such as chromium silicide, nickel silicide and iron silicide as metal catalyst, catalyzing silicon tetrachloride into trichlorosilane (CN104039699A), the catalyst needs to be formed in the reactor, resulting in a long induction period of the catalyst and low catalytic activity, for example, when the reaction temperature is 600 DEG C and H2 / STC is 4:1, the conversion rate of trichlorosilane is only 8.8%. Tokuyama co., ltd. discloses a method for manufacturing trichlorosilane (CN102753478B), which includes a first manufacturing process of reacting hydrogen chloride with metal silicon to generate trichlorosilane and a second manufacturing process of reacting tetra-chloro-silane and hydrogen with metal silicon to generate trichlorosilane, although metallurgical metal silicon, silicon iron or polycrystalline silicon and other solid substances containing metal state silicon elements are used as silicon sources in the second process, the reaction process is complex, and the second process still needs to add copper catalyst including copper powder, copper chloride or copper silicide, the catalyst activity is low, the catalyst induction period is long, and a long time reaction is needed to obtain trichlorosilane with high selectivity.

[0004] Therefore, the reported catalysts still have problems of complex system, complicated preparation steps, high catalyst cost and difficulty in industrialization. In the field, there are still problems of low single conversion rate of silicon powder, long catalyst induction time, poor thermal stability and easy loss. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a method and system for preparing trichlorosilane from silicon iron, which uses silicon iron ore, silicon tetrachloride and hydrogen as raw materials and fully reacts in a fluidized bed reactor to obtain trichlorosilane and FeSi y alloy, has high efficiency of preparing trichlorosilane and high single conversion rate of silicon, and significantly reduces the cost in the production process.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The first purpose of the present application is to provide a method for preparing trichlorosilane from silicon iron, which uses silicon iron ore, silicon tetrachloride and hydrogen as raw materials and fully reacts in a fluidized bed reactor to obtain trichlorosilane and FeSi y alloy, and specifically includes the following steps:

[0008] Silicon tetrachloride, hydrogen and silicon iron ore powder enter the fluidized bed reactor and fully react to obtain reacted materials; the reacted materials enter the cyclone separator for separation, the unreacted silicon iron ore solid phase at the bottom of the cyclone separator is circulated back to the fluidized bed reactor, and the top of the cyclone separator contains reacted FeSi yThe solid particles enter a washing tower for spray washing; hydrogen, trichlorosilane and silicon tetrachloride gas taken from the top of the washing tower are condensed and then enter a gas-liquid separator, hydrogen taken from the top of the gas-liquid separator is recycled back to the fluidized bed reactor, trichlorosilane and silicon tetrachloride liquid taken from the bottom of the gas-liquid separator are partially sent to a crude distillation column for rectification and partially recycled back to the washing tower for spray washing of FeSi y containing a small amount of chlorosilane y is discharged at the bottom of the washing tower; crude trichlorosilane is obtained at the top of the crude distillation column, and silicon tetrachloride product is obtained at the bottom of the crude distillation column and recycled back to the fluidized bed reactor.

[0009] Further, in the ferrosilicon ore, the atomic ratio of silicon element to iron element is greater than 1:1, preferably not less than 2:1, to ensure optimal reaction performance and silicon utilization rate.

[0010] Further, in the ferrosilicon ore FeSi x , 1 < x < 40.

[0011] Further preferably, in the ferrosilicon ore FeSi x , 2 ≤ x ≤ 20.

[0012] Further, the reaction equation of silicon tetrachloride, hydrogen and ferrosilicon is:

[0013] FeSi x + 3SiCl4 + H2→ FeSi y + HSiCl3 (x > 1, y ≤ 1).

[0014] Further, the molar ratio of hydrogen to silicon tetrachloride in the raw material is 1-10.

[0015] Further, the reaction pressure is 2.0-3.0 Mpa.

[0016] Further, the reaction temperature is 450-600℃.

[0017] Further, the temperature of the gas-liquid separator is -40 to -60℃.

[0018] Further, the working pressure of the gas-liquid separator is 0.5-1.0 MPa.

[0019] Further, the top temperature of the crude distillation column is 100-120℃.

[0020] Further, the bottom temperature of the crude distillation column is 120-150℃.

[0021] Further, the working pressure of the crude distillation column is 0.5-1.0 Mpa.

[0022] Further, the separation conditions are as follows: the silicon powder with a diameter greater than 10 μm is collected.

[0023] Further, the spray washing conditions are as follows: the spray density at the top of the spray tower is 10-30 L / (m 2 ·s).

[0024] Further, the part of the crude distillation tower is sent to the rectification tower, and the reflux ratio of the part circulating back to the washing tower process is 1:1-10:1.

[0025] Further, the crude product of trichlorosilane obtained at the top of the crude distillation tower is sent to downstream rectification purification.

[0026] In an embodiment of the present application, the ferrosilicon ore raw material is transported from a ferrosilicon ore storage tank to a fluidized bed reactor; a hydrogen / silicon tetrachloride mixed gas is input from the bottom of the fluidized bed reactor, and reacts with the ferrosilicon ore raw material in the fluidized bed reactor; the mixed gas after reaction is separated by a cyclone separator, and the separated ferrosilicon powder is circulated back to the reactor from the bottom of the cyclone separator for continuous reaction, and a small amount of fine FeSi y powder is carried from the upper end outlet of the cyclone separator into a washing tower; the washing tower washes and condenses the hydrogen and chlorosilane gas, and the chlorosilane containing FeSi y powder at the bottom of the washing tower is discharged as washing residue to residue slurry treatment, and the condensed hydrogen mixed with chlorosilane liquid at the top outlet of the washing tower is sent to a gas-liquid separator, hydrogen obtained at the top of the gas-liquid separator is circulated back to the fluidized bed reactor, and the chlorosilane liquid obtained at the bottom of the gas-liquid separator is partially sent to a crude distillation tower for separation, and partially circulated back to the washing tower for spraying; the trichlorosilane obtained at the top of the crude distillation tower after separation is sent to downstream rectification purification, and the silicon tetrachloride flowing out of the bottom of the tower is circulated back to the fluidized bed reactor for reuse.

[0027] A second object of the present application is to provide a trichlorosilane preparation system for realizing the method for preparing trichlorosilane from ferrosilicon, the system comprising a fluidized bed reactor, a cyclone separator, a washing tower, a gas-liquid separator, and a crude distillation tower; the fluidized bed reactor is connected with the cyclone separator; the cyclone separator is connected with the washing tower; the washing tower is connected with the gas-liquid separator; the gas-liquid separator is connected with the fluidized bed reactor; the gas-liquid separator is connected with the crude distillation tower; and the crude distillation tower is connected with the fluidized bed reactor.

[0028] Further, the system further comprises a ferrosilicon ore storage tank; the ferrosilicon ore storage tank is connected with the fluidized bed reactor; and the ferrosilicon ore storage tank is used for transporting the ferrosilicon ore raw material to the fluidized bed reactor.

[0029] Further, the ferrosilicon ore storage tank, the fluidized bed reactor, the cyclone separator, the washing tower, the gas-liquid separator, and the crude distillation tower in the system are directly connected mainly through pipelines.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] The present application uses ferrosilicon as a silicon source for preparing trichlorosilane, and does not need to add a catalyst. The iron and silicon elements in the ferrosilicon raw material are uniformly and closely combined, greatly improving the reaction efficiency, significantly reducing the induction time of the reaction, and solving the problems of poor thermal stability, easy loss and low efficiency of the added catalyst (such as copper-based catalyst) in the traditional cold hydrogenation reaction. The ferrosilicon provided by the present application has the advantages of low price, wide source, high efficiency and high single conversion rate of silicon, and significantly reduces the cost in the production process. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a process schematic diagram for preparing trichlorosilane from ferrosilicon.

[0033] Indicated in the figure:

[0034] 100: ferrosilicon ore storage tank; 200: fluidized bed reactor; 300: cyclone separator; 400: washing tower; 500: gas-liquid separator; 600: crude distillation column. DETAILED DESCRIPTION

[0035] The present application will be described in detail below in conjunction with the drawings and specific examples. In the technical solution, components, material names, connection structures, control methods and other features not explicitly described are considered as common technical features disclosed in the prior art.

[0036] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] It should be noted that in the present application, the terms "including", "containing" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or device. Without more limitations, the element defined by the sentence "including a..." does not exclude the presence of another identical element in the process, method, article or device including the element.

[0038] This invention provides a method for preparing trichlorosilane from ferrosilicon. The method uses ferrosilicon, silicon tetrachloride, and hydrogen as raw materials, and reacts them fully in a fluidized bed reactor 200 to obtain trichlorosilane and FeSi. y The alloying process specifically includes the following steps: silicon tetrachloride, hydrogen, and ferrosilicon powder are fed into a fluidized bed reactor 200 for complete reaction; the reacted material is then separated in a cyclone separator 300; the unreacted ferrosilicon solid phase at the bottom of the cyclone separator 300 is recycled back to the fluidized bed reactor 200, while the top of the cyclone separator 300 contains the reacted FeSi... y The solid particles in the gas enter the scrubbing tower 400; the hydrogen, trichlorosilane, and silicon tetrachloride gases collected from the top of the scrubbing tower 400 are condensed and then enter the gas-liquid separator 500. The hydrogen collected from the top of the gas-liquid separator is recycled back to the fluidized bed reactor 200, and the trichlorosilane and silicon tetrachloride liquids collected from the bottom of the gas-liquid separator 500 are partially collected and sent to the crude distillation tower 600, and partially recycled back to the scrubbing tower 400 for FeSi y Spray washing was performed on FeSi containing a small amount of chlorosilane. y The product is discharged from the bottom of the 400-unit washing tower; crude trichlorosilane is obtained at the top of the crude distillation tower, and silicon tetrachloride is obtained from the bottom of the 600-unit crude distillation tower and recycled back to the fluidized bed reactor 200. A significant feature of this invention is that ferrosilicon ore is used as the silicon source, which is inexpensive and readily available. Furthermore, ferrosilicon ore, silicon tetrachloride, and hydrogen react to produce trichlorosilane and FeSi. y It exhibits high reactivity, high silicon utilization in the compound, and requires no additional catalyst in the co-hydrogenation reaction, while simultaneously producing FeSi as a byproduct. y Alloys have low production costs.

[0039] The present invention further provides a trichlorosilane preparation system for implementing the above-described method for preparing trichlorosilane from ferrosilicon. The system includes a fluidized bed reactor 200, a cyclone separator 300, a washing tower 400, a gas-liquid separator 500, and a crude distillation tower 600. The fluidized bed reactor 200 is connected to the cyclone separator 300; the cyclone separator 300 is connected to the washing tower 400; the washing tower 400 is connected to the gas-liquid separator 500; the gas-liquid separator 500 is connected to the fluidized bed reactor 200; the gas-liquid separator 500 is connected to the crude distillation tower 600; and the crude distillation tower 600 is connected to the fluidized bed reactor 200. The system also includes a ferrosilicon ore storage tank 100; the ferrosilicon ore storage tank 100 is connected to the fluidized bed reactor 200; the ferrosilicon ore storage tank 100 is used to transport ferrosilicon ore raw material to the fluidized bed reactor 200.

[0040] In the following examples, FeSi 6.0 ,FeSi 3.8 ,FeSi 2.4 All were purchased from Wanxiang Metal Alloy Materials Company.

[0041] Example 1

[0042] This embodiment provides a method for preparing trichlorosilane from ferrosilicon, including the following steps:

[0043] H2 and STC feedstocks with a molar ratio of 8 are fed into the preheating gasifier via flow meters and feed pumps, respectively. The gasified material then enters the mixer, where it is thoroughly mixed before entering the fluidized bed reactor 200, along with ferrosilicon FeSi from the ferrosilicon storage tank 200. 6.0 The reaction occurs, and the reacted material enters the cyclone separator 300 for separation. The unreacted ferrosilicon solid phase at the bottom of the cyclone separator 300 is recycled back to the fluidized bed reactor, while the top of the cyclone separator 300 contains the reacted FeSi. y The solid particles in the gas enter the scrubbing tower 400 for spray washing. Hydrogen, trichlorosilane, and silicon tetrachloride gases are collected from the top of the scrubbing tower 400, condensed, and then enter the gas-liquid separator 500. Hydrogen gas from the top of the gas-liquid separator is recycled back to the fluidized bed reactor 200, while trichlorosilane and silicon tetrachloride liquids are collected from the bottom of the gas-liquid separator 500. A portion of these liquids enters the crude distillation tower 600 for rectification, and the other portion is recycled back to the scrubbing tower 400 for FeSi... y Spray washing was performed on FeSi containing a small amount of chlorosilane. y The product is discharged from the bottom of the scrubbing tower 400; crude trichlorosilane is obtained from the top of the crude distillation tower 600, and silicon tetrachloride is obtained from the bottom of the crude distillation tower 600 and recycled back to the fluidized bed reactor 200. The resulting gaseous products (a mixture of hydrogen, trichlorosilane, and silicon tetrachloride obtained from the top of the scrubbing tower 400) are analyzed by online chromatography to obtain the solid product after the reaction (FeSi containing a small amount of chlorosilane discharged from the bottom of the scrubbing tower 400). y ) is FeSi 0.88 The liquid hourly space velocity (WHSV) of STC relative to ferrosilicon is 1.0 h⁻¹. -1 STC's single-pass conversion rate was 25.4%, while TCS's selectivity was 96.8%.

[0044] Example 2

[0045] This embodiment provides a method for preparing trichlorosilane from ferrosilicon, comprising the following steps: H2 and STC raw materials with a molar ratio of 8 are fed into a preheating gasifier via a flow meter and a feed pump, respectively; the gasified material enters a mixer, is mixed evenly, and then enters a fluidized bed reactor with ferrosilicon FeSi. 6.0 The reaction occurred, and the remaining steps were the same as in Example 1. The resulting product was analyzed and detected by online chromatography, and the solid product obtained after the reaction was FeSi. 0.88 The liquid hourly space velocity (WHSV) of STC relative to ferrosilicon is 20.0 h⁻¹. -1STC's single-pass conversion rate was 17.7%, while TCS's selectivity was 97.9%.

[0046] Example 1 and Example 2 are both methods for preparing trichlorosilane from ferrosilicon. The specific process conditions for Example 1 and Example 2 are shown in Table 1.

[0047] Table 1. Methods for preparing trichlorosilane from ferrosilicon at different air velocities.

[0048]

[0049] Reaction conditions for Examples 1 and 2: reaction temperature 600℃, raw material FeSi 6.0 (Silicon-iron atomic ratio is 6.0:1, mass ratio is 75:25), H2 / STC molar ratio is 8, reaction pressure is 2.0MPa, STC: silicon tetrachloride, TCS: trichlorosilane.

[0050] Examples 3-6

[0051] Examples 3-6 provide a method for preparing trichlorosilane from ferrosilicon, comprising the following steps: H2 and STC raw materials with a molar ratio of 8 are fed into a preheating gasifier via a flow meter and a feed pump, respectively; the gasified material enters a mixer, is mixed uniformly, and then enters a fluidized bed reactor with ferrosilicon FeSi. 6.0 The reaction occurred, and the remaining steps were the same as in Example 1. The resulting product was analyzed and detected by online chromatography, and the solid product obtained after the reaction was FeSi. 0.88 The reaction activity was investigated within a reaction temperature range of 450-600℃. The results showed that the single-pass conversion of STC gradually increased with increasing reaction temperature. At a reaction temperature of 550℃, the single-pass conversion of STC stabilized at 23.4%, and at a reaction temperature of 600℃, the single-pass conversion of STC stabilized at 25.4%. The selectivity of TCS was above 96% in all cases.

[0052] Examples 3-6 all describe methods for preparing trichlorosilane from ferrosilicon. The specific process conditions for Examples 3-6 are shown in Table 2. Table 2: Preparation of trichlorosilane by cold hydrogenation of silicon tetrachloride at different temperatures.

[0053]

[0054]

[0055] Reaction conditions for Examples 3-6: Liquid hourly space velocity (LHSV) of STC was 1.0 h⁻¹. -1 Ferrosilicon is FeSi 6.0 (Silicon-to-iron atomic ratio is 6.0:1, mass ratio is 75:25), H2 / STC molar ratio is 8, reaction pressure is 2.0 MPa.

[0056] Examples 7-8

[0057] Examples 7-8 provide a method for preparing trichlorosilane from ferrosilicon, comprising the following steps: raw materials of H2 and STC with different molar ratios are fed into a preheating gasifier via flow meters and feed pumps, respectively; the gasified material enters a mixer, is mixed evenly, and then enters a fluidized bed reactor with ferrosilicon FeSi. 6.0 The reaction proceeded as described in Example 1, with the remaining steps identical. The resulting product was analyzed using online chromatography. The results showed that increasing the molar ratio of H2 to STC was beneficial for the conversion of STC and ferrosilicon. When the H2 / STC molar ratio was 3, the resulting solid product was FeSi, with a TCS selectivity of 98.6%.

[0058] Examples 7-8 are methods for preparing trichlorosilane from ferrosilicon. The specific process conditions for Examples 7-8 are shown in Table 3.

[0059] Table 3. Preparation of trichlorosilane by cold hydrogenation of silicon tetrachloride at different molar ratios.

[0060]

[0061] Reaction conditions for Examples 7-8: Liquid hourly space velocity (LHSV) of STC was 3.5 h⁻¹. -1 Ferrosilicon is FeSi 6.0 (Silicon-to-iron atomic ratio is 6.0:1, mass ratio is 75:25), H2 / STC molar ratio is 8, reaction pressure is 2.0 MPa.

[0062] Examples 9-11

[0063] Examples 9-11 provide a method for preparing trichlorosilane from ferrosilicon, comprising the following steps: H2 and STC raw materials with a molar ratio of 8 are fed into a preheating gasifier via a flow meter and a feed pump, respectively; the gasified material enters a mixer, is mixed uniformly, and then enters a fluidized bed reactor with ferrosilicon FeSi. 6.0 The reaction proceeded as described in Example 1, with the remaining steps identical. The resulting product was analyzed using online chromatography. The results showed that the conversion rate of STC increased with increasing reaction pressure. At a reaction pressure of 2.4 MPa, the resulting solid product was FeSi. 0.87 The selectivity of TCS was 98.5%; at a reaction pressure of 2.6 MPa, the obtained iron product was FeSi. 0.85 The selectivity of TCS was 98.7%; at a reaction pressure of 3.0 MPa, the solid product obtained after the reaction was FeSi. 0.82 The selectivity of TCS is 99.3%.

[0064] Examples 9-11 are all methods for preparing trichlorosilane from ferrosilicon. The specific process conditions for Examples 9-11 are as follows:

[0065] Table 4 shows the preparation of trichlorosilane by cold hydrogenation of silicon tetrachloride under different reaction pressures.

[0066]

[0067] Reaction conditions for Examples 9-11: Liquid hourly space velocity (LHSV) of STC was 3.5 h⁻¹. -1 Ferrosilicon is FeSi 6.0 The H2 / STC molar ratio is 8, and the reaction temperature is 550℃.

[0068] Examples 12-13

[0069] Examples 12-13 provide a method for preparing trichlorosilane from ferrosilicon, comprising the following steps: H2 and STC, with a molar ratio of 8, are fed into a preheating gasifier via a flow meter and a feed pump, respectively. The gasified material enters a mixer, is mixed uniformly, and then enters a fluidized bed reactor with ferrosilicon FeSi. 2.4 or FeSi 3.8 The reaction proceeded as described in Example 1, with the remaining steps identical. The resulting product was analyzed using online chromatography. When the silicon-to-iron atomic ratio was 3.7:1 and the mass ratio was 65:35, the STC conversion rate was 24.5%, yielding a solid product of FeSi. 0.81 The selectivity of TCS was 99.5%; when the silicon-to-iron atomic ratio was 2.4:1 and the mass ratio was 55:45, the conversion rate of STC was 26.7%, and the solid product obtained after the reaction was FeSi. 0.78 The selectivity of TCS is 99.6%.

[0070] Examples 12-13 are methods for preparing trichlorosilane from ferrosilicon. The specific process conditions for Examples 12-13 are shown in Table 5.

[0071] Table 5. Preparation of trichlorosilane by cold hydrogenation of silicon tetrachloride under different ferrosilicon ores.

[0072]

[0073] Reaction conditions for Examples 12-13: The reaction time-space velocity of STC was 3.5 h⁻¹. -1 The H2 / STC molar ratio was 8, the reaction temperature was 550℃, and the reaction pressure was 2.0 MPa. In all embodiments of this invention, the single-pass utilization rate of silicon in ferrosilicon ore exceeded 80%.

[0074] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing trichlorosilane from ferrosilicon, characterized in that, The method uses ferrosilicon, silicon tetrachloride, and hydrogen as raw materials, where the ferrosilicon FeSi x has 1 < x < 40, and reacts in a fluidized bed reactor to obtain trichlorosilane and FeSi y , and includes the following steps: Silicon tetrachloride, hydrogen and ferrosilicon are fed into a fluidized bed reactor (200) to react and obtain the reacted material; The reacted material enters a cyclone separator (300) for separation. The unreacted ferrosilicon solid phase at the bottom of the cyclone separator (300) is recycled back to the fluidized bed reactor, while the material at the top of the cyclone separator (300) contains the reacted FeSi. y The gas containing solid particles enters the scrubbing tower (400) for spray washing; Hydrogen, trichlorosilane, and silicon tetrachloride gases are collected from the top of the scrubbing tower (400). After condensation, they enter the gas-liquid separator (500). The hydrogen gas collected from the top of the gas-liquid separator is recycled back to the fluidized bed reactor (200). The trichlorosilane and silicon tetrachloride liquids collected from the bottom of the gas-liquid separator (500) are partially fed into the crude distillation tower (600) for rectification, and the other part is recycled back to the scrubbing tower (400) for FeSi... y Spray washing was performed on FeSi containing a small amount of chlorosilane. y Discharged at the bottom of the scrubbing tower (400); The crude product of trichlorosilane is obtained at the top of the crude distillation column (600), and the product of silicon tetrachloride is obtained at the bottom of the crude distillation column (600) and recycled back to the fluidized bed reactor (200).

2. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The FeSi y In the case of y≤1.

3. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The molar ratio of hydrogen to silicon tetrachloride in the raw materials is 1-10.

4. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The reaction pressure is 2.0-3.0 MPa.

5. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The reaction temperature is 450-600℃.

6. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The temperature of the gas-liquid separator (500) is -40℃ to -60℃.

7. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The gas-liquid separator (500) operates at a pressure of 0.5-1.0 MPa.

8. The method for preparing trichlorosilane from ferrosilicon according to claim 1, characterized in that, The top temperature of the crude distillation column (600) is 100-120℃; The bottom temperature of the crude distillation column (600) is 120-150℃; The working pressure of the crude distillation column (600) is 0.5-1.0 MPa.

9. A trichlorosilane preparation system for implementing the method for preparing trichlorosilane from ferrosilicon as described in any one of claims 1-8, characterized in that, The system includes a fluidized bed reactor (200), a cyclone separator (300), a scrubbing tower (400), a gas-liquid separator (500), and a crude distillation tower (600); The fluidized bed reactor (200) is connected to the cyclone separator (300); The cyclone separator (300) is connected to the scrubbing tower (400); The scrubbing tower (400) is connected to the gas-liquid separator (500); The gas-liquid separator (500) is connected to the fluidized bed reactor (200); The gas-liquid separator (500) is connected to the crude distillation column (600); The coarse distillation tower (600) is connected to the fluidized bed reactor (200).

10. The trichlorosilane preparation system according to claim 9, characterized in that, The system also includes a ferrosilicon storage tank (100); The ferrosilicon storage tank (100) is connected to the fluidized bed reactor (200); The ferrosilicon storage tank (100) is used to transport ferrosilicon raw materials to the fluidized bed reactor (200).

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