A particulate silicon production system and method

Abstract

The application provides a granular silicon production system and method, the granular silicon production system comprising a cold hydrogenation device, a disproportionation reactor, a seed reactor and a heterogeneous deposition reactor; an inlet of the cold hydrogenation device is used for receiving hydrogen, silicon powder and carbon tetrachloride, an outlet of the cold hydrogenation device is connected with an inlet of the disproportionation reactor, a silane outlet of the disproportionation reactor is connected with an inlet of the seed reactor and an inlet of the heterogeneous deposition reactor respectively, and a dichlorodihydrogen silicon outlet of the disproportionation reactor is connected with the inlet of the seed reactor; a seed outlet of the seed reactor is connected with the inlet of the heterogeneous deposition reactor, and the inlet of the heterogeneous deposition reactor also receives hydrogen. The application can continuously produce granular silicon seeds on line, and avoids secondary pollution of the seeds.

Description

Technical Field

[0001] This invention belongs to the field of polycrystalline silicon preparation technology, and relates to a particulate silicon production system and method. Background Technology

[0002] Polysilicon (also known as silicon material) is a non-metallic material made from industrial silicon through a series of physicochemical reactions to achieve a certain purity, with a silicon content of over 99.9999%. In the photovoltaic field, polysilicon is processed into silicon wafers, cells, and modules, ultimately used in photovoltaic power generation systems. Crystalline silicon modules account for approximately 97.5% of photovoltaic installations, with the remainder being thin-film modules, etc. Therefore, polysilicon is an important upstream component of the photovoltaic industry.

[0003] Currently, the mainstream polysilicon production technologies are the modified Siemens process using trichlorosilane as raw material and the fluidized bed process using silane gas as raw material. For the Siemens process, the emergence of tail gas recovery systems has improved material utilization, cold hydrogenation has significantly reduced energy consumption by replacing hot hydrogenation, and multi-pair rods and large-diameter reduction furnaces have effectively reduced the power consumption of the reduction furnace. With the primary goal of cost reduction and efficiency improvement, technological innovation is key to a company's competitiveness. Currently, the silane fluidized bed process, with its low power consumption advantage, has successfully achieved mass production, and its development potential is gradually being validated by the industry.

[0004] The silane fluidized bed process refers to a technical route that utilizes the thermal decomposition of silane (SiH4) in a fluidized bed reactor. Specifically, high-purity seed crystals (approximately 0.2-0.6 mm in diameter) are added from the top of the reactor, accumulating to form a seed crystal particle bed. Silane and hydrogen gas are introduced from the bottom of the reactor, fluidizing the bed. Under the action of an external heater, silane decomposes and deposits on the seed crystal surface. The seed crystal particles continuously epitaxially grow until sufficient granular silicon settles to the bottom of the reactor and is discharged. During the production process, solid reactants move from top to bottom, while gaseous reactants flow from bottom to top, thus achieving uninterrupted continuous production.

[0005] In the process of producing granular silicon using the silane fluidized bed method, the reaction seed crystals used are fine granular silicon products screened from the granular silicon product. The seed crystals for producing granular silicon are not produced online continuously. At the same time, when fine granular silicon products are screened from the granular silicon product, the possibility of seed crystals being contaminated by impurities increases, resulting in unstable quality. Summary of the Invention

[0006] To address the problems of the prior art, the present invention provides a particulate silicon production system and method that can continuously produce particulate silicon seeds online, avoiding secondary contamination of the seeds.

[0007] This invention is achieved through the following technical solution:

[0008] A particulate silicon production system includes a cold hydrogenation unit, a disproportionation reactor, a seed reactor, and a heterogeneous deposition reactor. The inlet of the cold hydrogenation unit receives hydrogen, silicon powder, and carbon tetrachloride. The outlet of the cold hydrogenation unit is connected to the inlet of the disproportionation reactor. The silane outlet of the disproportionation reactor is connected to the inlet of the seed reactor and the inlet of the heterogeneous deposition reactor, respectively. The dichlorosilane outlet of the disproportionation reactor is connected to the inlet of the seed reactor. The seed outlet of the seed reactor is connected to the inlet of the heterogeneous deposition reactor, which also receives hydrogen at its inlet.

[0009] Preferably, the granular silicon production system further includes a first distillation unit, a second distillation unit, and a third distillation unit; the outlet of the cold hydrogenation unit is connected to the inlet of the first distillation unit, the chlorosilane outlet of the first distillation unit is connected to the inlet of the disproportionation reactor, the silane outlet of the disproportionation reactor is connected to the inlet of the second distillation unit, and the dichlorosilane outlet of the disproportionation reactor is connected to the inlet of the third distillation unit; the silane gas outlet of the second distillation unit is connected to the inlet of the seed reactor and the inlet of the heterogeneous deposition reactor, respectively, and the dichlorosilane outlet of the third distillation unit is connected to the inlet of the seed reactor.

[0010] Furthermore, the particulate silicon production system also includes a first purification device, the gas outlet of the heterogeneous deposition reactor is connected to the inlet of the first purification device, and the hydrogen outlet of the first purification device is connected to the inlet of the heterogeneous deposition reactor and the inlet of the cold hydrogenation device, respectively.

[0011] Furthermore, the particulate silicon production system also includes a second purification device. The silicon particle outlet of the heterogeneous deposition reactor is connected to the inlet of the second purification device, the gas outlet of the second purification device is connected to the inlet of the first purification device, and the two solid outlets of the second purification device are the outlets of particulate silicon and nano-silicon, respectively.

[0012] Furthermore, the silicon tetrachloride outlet of the first distillation unit is connected to the inlet of the cold hydrogenation unit.

[0013] Preferably, the silicon tetrachloride outlet of the disproportionation reactor is connected to the inlet of the cold hydrogenation unit.

[0014] A method for producing granular silicon, based on the aforementioned granular silicon production system, includes the following steps:

[0015] Trichlorosilane was obtained by hydrogenating silicon powder, silicon tetrachloride and hydrogen in a cold hydrogenation unit.

[0016] Trichlorosilane from the cold hydrogenation unit was disproportionated in a disproportionation reactor, and the reaction products were separated to obtain dichlorosilane, silicon tetrachloride and silane, respectively.

[0017] Silane and dichlorosilane from the disproportionation reactor are reacted in a seed reactor to obtain seed crystals;

[0018] Using hydrogen, silane from a disproportionation reactor, and seeds from a seed reactor as raw materials, a heterogeneous deposition reaction is carried out in a heterogeneous deposition reactor to obtain particulate silicon.

[0019] Preferably, the granular silicon production system further includes a first distillation unit, a second distillation unit, and a third distillation unit; the outlet of the cold hydrogenation unit is connected to the inlet of the first distillation unit, the chlorosilane outlet of the first distillation unit is connected to the inlet of the disproportionation reactor, the silane outlet of the disproportionation reactor is connected to the inlet of the second distillation unit, and the dichlorosilane outlet of the disproportionation reactor is connected to the inlet of the third distillation unit; the silane gas outlet of the second distillation unit is connected to the inlet of the seed reactor and the inlet of the heterogeneous deposition reactor, respectively, and the dichlorosilane outlet of the third distillation unit is connected to the inlet of the seed reactor;

[0020] The process of disproportionating trichlorosilane from the cold hydrogenation unit in a disproportionation reactor and separating the reaction products to obtain dichlorosilane, silicon tetrachloride, and silane specifically includes: purifying and separating the trichlorosilane from the cold hydrogenation unit into a mixture of dichlorosilane and trichlorosilane and silicon tetrachloride using a first distillation unit; and disproportionating the mixture of dichlorosilane and trichlorosilane from the first distillation unit in a disproportionation reactor and separating the reaction products to obtain dichlorosilane, silicon tetrachloride, and silane.

[0021] The process of reacting silane and dichlorosilane from the disproportionation reactor in a seed reactor to obtain seed crystals specifically includes: purifying the silane from the disproportionation reactor using a second distillation unit to obtain silane gas; purifying the dichlorosilane from the disproportionation reactor using a third distillation unit to obtain dichlorosilane; and reacting the silane gas purified by the second distillation unit with the dichlorosilane purified by the third distillation unit in the seed reactor to obtain seed crystals.

[0022] The use of hydrogen, silane from the disproportionation reactor, and seeds from the seed reactor as raw materials specifically refers to using hydrogen, silane gas purified from the second distillation unit, and seeds from the seed reactor as raw materials.

[0023] Preferably, the particulate silicon production system further includes a first purification device, wherein the gas outlet of the heterogeneous deposition reactor is connected to the inlet of the first purification device, and the hydrogen outlet of the first purification device is connected to the inlet of the heterogeneous deposition reactor and the inlet of the cold hydrogenation device, respectively.

[0024] The particulate silicon production method further includes the following steps: purifying and pressurizing the gas from the heterogeneous deposition reactor using a first purification device and then returning it to the heterogeneous deposition reactor and the cold hydrogenation device.

[0025] Preferably, the particulate silicon production system further includes a second purification device, wherein the silicon particle outlet of the heterogeneous deposition reactor is connected to the inlet of the second purification device, the gas outlet of the second purification device is connected to the inlet of the first purification device, and the two solid outlets of the second purification device are the outlets of particulate silicon and nano-silicon, respectively.

[0026] The method for producing granular silicon further includes the following steps: purifying and separating coarse granular silicon from a heterogeneous deposition reactor using a second purification device to obtain granular silicon products and nano-silicon products respectively; and purifying hydrogen gas from the second purification device by entering a first purification device.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention discloses a granular silicon production system using silicon powder, silicon tetrachloride, and hydrogen as raw materials. A hydrogenation reaction is carried out in a cold hydrogenation unit to obtain trichlorosilane. The trichlorosilane undergoes a one-step disproportionation reaction in a disproportionation reactor, and the reaction products are separated to obtain dichlorosilane, silicon tetrachloride, and silane. Silane reacts with dichlorosilane in a seed reactor to obtain seed crystals. Silane reacts with hydrogen in a heterogeneous deposition reactor to generate silicon, which is deposited on the seed crystals to obtain coarse granular silicon. This invention obtains dichlorosilane, silicon tetrachloride, and silane through a one-step disproportionation reaction of trichlorosilane, and uses a portion of the silane to react with dichlorosilane to provide seed crystals for the heterogeneous deposition reactor. Compared to extracting seed crystals from silicon granules, this method allows for continuous online production of granular silicon seed crystals, avoids secondary contamination of the seed crystals, solves the problem of unstable seed crystal quality, and improves the production efficiency of the granular silicon production equipment.

[0029] Furthermore, the present invention includes three distillation units for purifying trichlorosilane, silane, and dichlorosilane, respectively, thereby providing high-purity feed gas for the disproportionation reactor, seed reactor, and heterogeneous deposition reactor, thus improving the purity of the product.

[0030] Furthermore, the present invention includes a first purification device for purifying the gas exiting the heterogeneous deposition reactor, removing silane and microsilica, and returning the hydrogen gas to the heterogeneous deposition reactor and cold hydrogenation device for recycling, which can improve the utilization rate of raw materials.

[0031] Furthermore, in the silane fluidized bed process for producing granular silicon, hydrogen gas adheres to the interior of the granular silicon product, existing in the form of dangling bonds, commonly referred to as molten hydrogen. This molten hydrogen can cause hydrogen jumps during the downstream single crystal pulling process, affecting the continuity and stability of silicon single crystal pulling. Simultaneously, a large amount of microsilica powder adheres to the surface of the granular silicon, making it prone to impurity adsorption and reducing product quality. Therefore, this invention incorporates a second purification device to purify the granular silicon product exiting the heterogeneous deposition reactor, removing microsilica powder from the surface of the granular silicon and hydrogen gas trapped within it. This effectively reduces the residual hydrogen concentration and microsilica powder content in the granular silicon, thereby further improving product quality.

[0032] Furthermore, the present invention connects the silicon tetrachloride outlet of the first distillation unit to the inlet of the cold hydrogenation unit, and the silicon tetrachloride outlet of the disproportionation reactor to the inlet of the cold hydrogenation unit, thereby returning the separated silicon tetrachloride to the cold hydrogenation unit for recycling and improving the raw material utilization efficiency. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a particulate silicon production system according to a specific embodiment of the present invention.

[0035] Wherein: 1 is a cold hydrogenation unit, 2 is a first distillation unit, 3 is a disproportionation reactor, 4 is a second distillation unit, 5 is a third distillation unit, 6 is a seed reactor, 7 is a heterogeneous deposition reactor, 8 is a first purification unit, and 9 is a second purification unit. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0038] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0039] The particulate silicon production system of the present invention includes a cold hydrogenation device 1, a disproportionation reactor 3, a seed reactor 6, and a heterogeneous deposition reactor 7. The inlet of the cold hydrogenation device 1 is used to receive hydrogen, silicon powder, and carbon tetrachloride. The outlet of the cold hydrogenation device 1 is connected to the inlet of the disproportionation reactor 3. The silane outlet of the disproportionation reactor 3 is connected to the inlet of the seed reactor 6 and the inlet of the heterogeneous deposition reactor 7, respectively. The dichlorosilane outlet of the disproportionation reactor 3 is connected to the inlet of the seed reactor 6. The seed outlet of the seed reactor 6 is connected to the inlet of the heterogeneous deposition reactor 7, and the inlet of the heterogeneous deposition reactor 7 also receives hydrogen.

[0040] In some specific embodiments of the present invention, the particulate silicon production system further includes a first distillation unit 2, a second distillation unit 4, and a third distillation unit 5; the outlet of the cold hydrogenation unit 1 is connected to the inlet of the first distillation unit 2, the chlorosilane outlet of the first distillation unit 2 is connected to the inlet of the disproportionation reactor 3, the silane outlet of the disproportionation reactor 3 is connected to the inlet of the second distillation unit 4, and the dichlorosilane outlet of the disproportionation reactor 3 is connected to the inlet of the third distillation unit 5; the silane gas outlet of the second distillation unit 4 is connected to the inlet of the seed reactor 6 and the inlet of the heterogeneous deposition reactor 7, respectively, and the dichlorosilane outlet of the third distillation unit 5 is connected to the inlet of the seed reactor 6.

[0041] In the cold hydrogenation unit 1, hydrogen, silicon powder, and carbon tetrachloride are used as raw materials to carry out a hydrogenation reaction to obtain trichlorosilane; the trichlorosilane composition includes dichlorosilane, trichlorosilane, and silicon tetrachloride. The first distillation unit 2 is used to purify and separate the trichlorosilane from the cold hydrogenation unit 1, separating it into a mixture of dichlorosilane and trichlorosilane and silicon tetrachloride. In the disproportionation reactor 3, the mixture of dichlorosilane and trichlorosilane from the first distillation unit 2 undergoes a disproportionation reaction, whereby the trichlorosilane reacts to produce dichlorosilane and silane, which are then separated to obtain dichlorosilane, silane, and silicon tetrachloride, respectively. The second distillation unit 4 is used to purify the silane from the disproportionation reactor 3 to obtain silane gas; the third distillation unit 5 is used to purify the dichlorosilane from the disproportionation reactor 3 to obtain dichlorosilane. In the seed reactor 6, the silane gas reacts with dichlorosilane to obtain polycrystalline silicon seeds. In the heterogeneous deposition reactor 7, silane gas reacts with hydrogen gas to generate silicon, which is deposited on seed crystals to form particulate silicon.

[0042] In some specific embodiments of the present invention, the silicon tetrachloride outlet of the first distillation unit 2 is connected to the inlet of the cold hydrogenation unit 1, so that the silicon tetrachloride separated by the first distillation unit 2 is returned to the cold hydrogenation unit 1 for recycling.

[0043] In some specific embodiments of the present invention, the silicon tetrachloride outlet of the disproportionation reactor 3 is connected to the inlet of the cold hydrogenation device 1, thereby returning the silicon tetrachloride separated from the disproportionation reactor 3 to the cold hydrogenation device 1 for recycling.

[0044] In some specific embodiments of the present invention, the particulate silicon production system further includes a first purification device 8. The gas outlet of the heterogeneous deposition reactor 7 is connected to the inlet of the first purification device 8, and the hydrogen outlet of the first purification device 8 is connected to the inlet of the heterogeneous deposition reactor 7 and the inlet of the cold hydrogenation device 1, respectively. The first purification device 8 is used to purify the hydrogen from the heterogeneous deposition reactor 7. The purified hydrogen is returned to the heterogeneous deposition reactor 7 and the cold hydrogenation device 1, realizing the recycling of hydrogen. The silicon powder obtained from the hydrogen purification forms nano-silicon products.

[0045] In some specific embodiments of the present invention, the granular silicon production system further includes a second purification device 9. The silicon particle outlet of the heterogeneous deposition reactor 7 is connected to the inlet of the second purification device 9, and the gas outlet of the second purification device 9 is connected to the inlet of the first purification device 8. The two solid outlets of the second purification device 9 are for granular silicon and nano-silicon, respectively. The second purification device 9 mainly includes heating, degassing, displacement, sieving, cleaning, and drying processes to purify the granular silicon from the heterogeneous deposition reactor 7, removing silicon powder from the surface of the silicon particles and hydrogen from the silicon particles, to obtain high-purity granular silicon and nano-silicon products. The hydrogen from the second purification device 9 is recycled after purification in the first purification device 8.

[0046] Based on the above-described particulate silicon production system, the particulate silicon production method of the present invention includes the following steps:

[0047] Using silicon powder, silicon tetrachloride and hydrogen as raw materials, a hydrogenation reaction is carried out in cold hydrogenation unit 1 to obtain trichlorosilane.

[0048] Trichlorosilane from the cold hydrogenation unit 1 is disproportionated in the disproportionation reactor 3, and the reaction products are separated to obtain dichlorosilane, silicon tetrachloride and silane, respectively.

[0049] Silane and dichlorosilane from disproportionation reactor 3 are reacted in seed reactor 6 to obtain seed crystals;

[0050] Using hydrogen, silane from disproportionation reactor 3, and seeds from seed reactor 6 as raw materials, a heterogeneous deposition reaction is carried out in heterogeneous deposition reactor 7 to obtain particulate silicon.

[0051] When the granular silicon production system includes a first distillation unit 2, a second distillation unit 4, and a third distillation unit 5, the above-mentioned granular silicon production method specifically includes the following steps:

[0052] Using silicon powder, silicon tetrachloride and hydrogen as raw materials, a hydrogenation reaction is carried out in cold hydrogenation unit 1 to obtain trichlorosilane.

[0053] The trichlorosilane from the cold hydrogenation unit 1 is purified and separated into a mixture of dichlorosilane and trichlorosilane and silicon tetrachloride by the first distillation unit 2;

[0054] The mixture of dichlorosilane and trichlorosilane from the first distillation unit 2 is subjected to a disproportionation reaction in the disproportionation reactor 3, and the reaction products are separated to obtain dichlorosilane, silicon tetrachloride and silane respectively.

[0055] The silane from the disproportionation reactor 3 is purified by the second distillation unit 4 to obtain silane gas;

[0056] Dichlorodihydrosilane from disproportionation reactor 3 is purified by third distillation unit 5 to obtain dichlorodihydrosilane;

[0057] The silane gas purified by the second distillation unit 4 and the dichlorosilane purified by the third distillation unit 5 are reacted in the seed reactor 6 to obtain seed crystals.

[0058] The silane gas purified by the second distillation unit 4 is reacted with the seed crystals and hydrogen gas from the seed reactor 6 as raw materials in the heterogeneous deposition reactor 7 to obtain particulate silicon.

[0059] In some specific embodiments of the present invention, the particulate silicon production method further includes: sending silicon tetrachloride from the first distillation unit 2 and silicon tetrachloride from the disproportionation reactor 3 back to the cold hydrogenation unit 1.

[0060] In some specific embodiments of the present invention, the particulate silicon production method further includes at least one of the following steps:

[0061] The particulate silicon from the heterogeneous deposition reactor 7 is purified and separated by the second purification device 9 to obtain particulate silicon products and nano silicon products.

[0062] The gas from the heterogeneous deposition reactor 7 is purified, separated, and pressurized by the first purification device 8 and then returned to the heterogeneous deposition reactor 7 and the cold hydrogenation device 1.

[0063] Example 1

[0064] The granular silicon production system described in this embodiment includes a cold hydrogenation unit 1, a first distillation unit 2, a disproportionation reactor 3, a second distillation unit 4, a third distillation unit 5, a seed reactor 6, a heterogeneous deposition reactor 7, a first purification unit 8, and a second purification unit 9. The inlet of the cold hydrogenation unit 1 receives hydrogen, silicon powder, and carbon tetrachloride. The outlet of the cold hydrogenation unit 1 is connected to the inlet of the first distillation unit 2. The chlorosilane outlet of the first distillation unit 2 is connected to the inlet of the disproportionation reactor 3. The silicon tetrachloride outlet of the first distillation unit 2 is connected to the inlet of the cold hydrogenation unit 1. The silane outlet of the disproportionation reactor 3 is connected to the inlet of the second distillation unit 4. The dichlorosilane outlet of the disproportionation reactor 3 is connected to the inlet of the third distillation unit 5. The silicon tetrachloride outlet of the disproportionation reactor 3 is connected to the inlet of the cold hydrogenation unit 1. The silane gas outlet of the second distillation unit 4 is connected to the inlet of the seed reactor 6 and the inlet of the heterogeneous deposition reactor 7, respectively; the dichlorosilane outlet of the third distillation unit 5 is connected to the inlet of the seed reactor 6; the seed outlet of the seed reactor 6 is connected to the inlet of the heterogeneous deposition reactor 7, which also receives hydrogen gas; the gas outlet of the heterogeneous deposition reactor 7 is connected to the inlet of the first purification unit 8, and the hydrogen outlet of the first purification unit 8 is connected to the inlet of the heterogeneous deposition reactor 7 and the inlet of the cold hydrogenation unit 1, respectively; the silicon particle outlet of the heterogeneous deposition reactor 7 is connected to the inlet of the second purification unit 9, and the gas outlet of the second purification unit 9 is connected to the inlet of the first purification unit 8; the two solid outlets of the second purification unit 9 are the outlets of granular silicon and nano-silicon, respectively.

[0065] The particulate silicon production method described in this embodiment includes the following steps:

[0066] Step 1: Using silicon powder, silicon tetrachloride and hydrogen as raw materials, a hydrogenation reaction is carried out in cold hydrogenation device 1 to obtain crude trichlorosilane; wherein, the crude trichlorosilane consists of dichlorosilane, trichlorosilane and silicon tetrachloride.

[0067] Step 2: The crude trichlorosilane is purified and separated into a mixture of dichlorosilane and trichlorosilane and silicon tetrachloride by the first distillation unit 2. The separated silicon tetrachloride is returned to the cold hydrogenation unit 1, and the mixture of dichlorosilane and trichlorosilane enters the disproportionation reactor 3. After reaction, it is separated and purified to obtain crude dichlorosilane, silicon tetrachloride and crude silane.

[0068] Step 3: The crude silane from disproportionation reactor 3 is purified and separated by the second distillation unit 4 to obtain high-purity silane gas. The crude dichlorosilane from disproportionation reactor 3 is purified and separated by the third distillation unit 5 to obtain high-purity dichlorosilane.

[0069] Step four: High-purity silane gas from the second distillation unit 4 and high-purity dichlorosilane from the third distillation unit 5 are introduced into the seed reactor 6 to react and generate polycrystalline silicon seeds.

[0070] Step 5: High-purity silane gas from the second distillation unit 4, seed crystals from the seed reactor 6, and hydrogen gas circulating from the heterogeneous deposition reactor 7 undergo a heterogeneous deposition reaction in the heterogeneous deposition reactor 7. The silicon decomposed from the silane gas is deposited on the seed crystal surface to form coarse-particle silicon products.

[0071] Step six: The equivalent diameter of the silicon particles obtained from the heterogeneous deposition reactor 7 is over 95% in the range of 150-2000 micrometers. The coarse silicon particles are then treated in the second purification unit 9 to remove silicon powder, yielding silicon particles and nano-silicon products after silicon powder removal. The second purification unit 9 removes adsorbed silicon powder from the surface of the silicon particles and removes hydrogen gas coated with silicon powder, reducing the molten hydrogen content in the silicon particles to 5-50 ppma.

[0072] Step 7: The gas from the heterogeneous deposition reactor 7 is purified and separated by the first purification device 8 and pressurized to form high-purity hydrogen, which is then returned to the heterogeneous deposition reactor 7 and the cold hydrogenation device 1 for recycling.

[0073] This invention enables continuous online production of granular silicon seed crystals, avoiding secondary contamination of the seed crystals, improving the raw material utilization rate of the silane fluidized bed device, and increasing the production efficiency of the product. The granular silicon and hydrogen are purified by a purification device to remove the hydrogen coated in the silicon particles and to obtain granular silicon products after silicon powder removal. This can effectively reduce the residual hydrogen concentration and micro silicon powder in the granular silicon, thereby further improving the product quality and stability.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A particulate silicon production system, characterized in that, The system includes a cold hydrogenation unit (1), a disproportionation reactor (3), a seed reactor (6), and a heterogeneous deposition reactor (7). The inlet of the cold hydrogenation unit (1) is used to receive hydrogen, silicon powder, and carbon tetrachloride. The outlet of the cold hydrogenation unit (1) is connected to the inlet of the disproportionation reactor (3). The silane outlet of the disproportionation reactor (3) is connected to the inlet of the seed reactor (6) and the inlet of the heterogeneous deposition reactor (7), respectively. The dichlorosilane outlet of the disproportionation reactor (3) is connected to the inlet of the seed reactor (6). The seed outlet of the seed reactor (6) is connected to the inlet of the heterogeneous deposition reactor (7). The inlet of the heterogeneous deposition reactor (7) also receives hydrogen. The granular silicon production system also includes a first distillation unit (2), a second distillation unit (4), and a third distillation unit (5); the outlet of the cold hydrogenation unit (1) is connected to the inlet of the first distillation unit (2), the chlorosilane outlet of the first distillation unit (2) is connected to the inlet of the disproportionation reactor (3), the silane outlet of the disproportionation reactor (3) is connected to the inlet of the second distillation unit (4), and the dichlorosilane outlet of the disproportionation reactor (3) is connected to the inlet of the third distillation unit (5); the silane gas outlet of the second distillation unit (4) is connected to the inlet of the seed reactor (6) and the inlet of the heterogeneous deposition reactor (7), respectively, and the dichlorosilane outlet of the third distillation unit (5) is connected to the inlet of the seed reactor (6).

2. The particulate silicon production system according to claim 1, characterized in that, The particulate silicon production system also includes a first purification device (8), the gas outlet of the heterogeneous deposition reactor (7) is connected to the inlet of the first purification device (8), and the hydrogen outlet of the first purification device (8) is connected to the inlet of the heterogeneous deposition reactor (7) and the inlet of the cold hydrogenation device (1), respectively.

3. The particulate silicon production system according to claim 2, characterized in that, The particulate silicon production system also includes a second purification device (9). The silicon particle outlet of the heterogeneous deposition reactor (7) is connected to the inlet of the second purification device (9). The gas outlet of the second purification device (9) is connected to the inlet of the first purification device (8). The two solid outlets of the second purification device (9) are the outlets of particulate silicon and nano-silicon, respectively.

4. The particulate silicon production system according to claim 1, characterized in that, The silicon tetrachloride outlet of the first distillation unit (2) is connected to the inlet of the cold hydrogenation unit (1).

5. The particulate silicon production system according to claim 1, characterized in that, The silicon tetrachloride outlet of the disproportionation reactor (3) is connected to the inlet of the cold hydrogenation unit (1).

6. A method for producing granular silicon, characterized in that, The particulate silicon production system according to any one of claims 1 to 5 includes the following steps: Using silicon powder, silicon tetrachloride and hydrogen as raw materials, a hydrogenation reaction is carried out in a cold hydrogenation device (1) to obtain trichlorosilane; The trichlorosilane from the cold hydrogenation unit (1) is purified and separated into a mixture of dichlorosilane and trichlorosilane and silicon tetrachloride by the first distillation unit (2); the mixture of dichlorosilane and trichlorosilane from the first distillation unit (2) is subjected to a disproportionation reaction in the disproportionation reactor (3), and the reaction products are separated to obtain dichlorosilane, silicon tetrachloride and silane respectively; The silane from the disproportionation reactor (3) is purified by the second distillation unit (4) to obtain silane gas; the dichlorosilane from the disproportionation reactor (3) is purified by the third distillation unit (5) to obtain dichlorosilane; the silane gas obtained by the second distillation unit (4) and the dichlorosilane obtained by the third distillation unit (5) are reacted in the seed reactor (6) to obtain seed crystals; Using hydrogen, silane gas purified from the second distillation unit (4), and seed crystals from the seed reactor (6) as raw materials, a heterogeneous deposition reaction is carried out in the heterogeneous deposition reactor (7) to obtain particulate silicon.

7. The method for producing granular silicon according to claim 6, characterized in that, The particulate silicon production method further includes the following steps: the gas from the heterogeneous deposition reactor (7) is purified and pressurized by the first purification device (8) and then returned to the heterogeneous deposition reactor (7) and the cold hydrogenation device (1).

8. The method for producing granular silicon according to claim 7, characterized in that, The method for producing particulate silicon also includes the following steps: the coarse particulate silicon from the heterogeneous deposition reactor (7) is purified and separated by a second purification device (9) to obtain particulate silicon products and nano silicon products respectively; the hydrogen gas from the second purification device (9) enters the first purification device (8) for purification.

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