A carbon-containing chlorosilane impurity removal and chlorosilane recovery system

Abstract

This utility model discloses a system for removing impurities from carbon-containing chlorosilanes and recovering chlorosilanes, comprising: a first distillation column for receiving and concentrating carbon-containing chlorosilanes; a first adsorption and reaction device connected to the first distillation column, the first adsorption and reaction device being filled with a metal adsorbent material and equipped with a silicon tetrachloride feed pipeline; a second adsorption and reaction device connected to the first adsorption and reaction device, the second adsorption and reaction device being filled with a methyldichlorosilane adsorbent material; a second distillation column connected to the second adsorption and reaction device; and a third distillation column connected to the second distillation column. This utility model can adsorb and concentrate metal impurities in carbon-containing chlorosilanes as a catalyst for the carbon removal reaction, effectively avoiding deactivation and failure caused by metal impurities encapsulating the resin catalyst, improving the conversion rate of methyldichlorosilane, and effectively avoiding the disproportionation reaction of silicon trichloride in the presence of the resin catalyst, thereby improving the carbon removal efficiency and chlorosilane recovery efficiency.

Description

Technical Field

[0001] This utility model belongs to the field of polycrystalline silicon technology, specifically relating to a system for removing impurities from carbon-containing chlorosilanes and recovering chlorosilanes. Background Technology

[0002] Metallic impurities (Fe, Cr, Ni, Cu, Zn, Na) and carbon impurities (mainly in the form of methyldichlorosilane and methyltrichlorosilane) in trichlorosilane, a raw material for polysilicon production, significantly hinder the improvement of polysilicon quality. Currently, the industry primarily employs a distillation and adsorption process to remove metallic and carbon-containing chlorosilane impurities from trichlorosilane, using resins or activated carbon as the adsorption materials.

[0003] Methyltrichlorosilane is well removed by distillation. However, since the boiling point of methyldichlorosilane is close to that of trichlorosilane and falls between that of trichlorosilane and silicon tetrachloride, the separation of dimethylchlorosilane is more difficult. If methyldichlorosilane is removed from chlorosilanes by distillation, a large reflux ratio is often required, and the amount of residue discharged from the bottom of the column is also increased in order to partially remove it from the system. This removal method not only leads to a significant increase in steam consumption during the distillation of trichlorosilane, but the increased amount of residue discharged from the bottom of the column also makes the recovery and treatment of chlorosilane feedstock more difficult, and the removal effect on methyldichlorosilane is not ideal.

[0004] Furthermore, while using resin materials as adsorbents can promote the conversion of methyldichlorosilane to methyltrichlorosilane to some extent—meaning the resin can act as a catalyst—using resin as a catalyst has at least the following drawbacks:

[0005] 1) When the content of methyldichlorosilane in trichlorosilane is low (e.g., 5-500 mg / kg), its reaction conversion rate is low, generally around 70%, which results in limited carbon removal capacity of the trichlorosilane distillation system and affects the overall quality improvement of polysilicon.

[0006] 2) A large number of metal impurities (metal chlorides) in trichlorosilane will coat the surface of the resin catalyst, which will have an adverse effect on the catalytic effect of the resin catalyst, making the resin catalyst easy to be poisoned, deactivated and ineffective, resulting in high carbon removal cost of chlorosilane.

[0007] 3) During the conversion of methyldichlorosilane to methyltrichlorosilane, trichlorosilane undergoes a disproportionation reaction. This consumes trichlorosilane and introduces new challenges to the separation and purification of downstream materials, making the process more complex. To suppress the disproportionation reaction of trichlorosilane, a certain mass of silicon tetrachloride needs to be mixed with it before it enters the decarbonization reactor, based on the mass flow rate of trichlorosilane. This results in a larger decarbonization reactor and distillation equipment, and a larger amount of catalyst is required. Utility Model Content

[0008] The technical problem to be solved by this utility model is to address the above-mentioned shortcomings of the existing technology by providing a carbon-containing chlorosilane impurity removal and chlorosilane recovery system. This system can adsorb and enrich the metal impurities in carbon-containing chlorosilanes as catalysts for the carbon removal reaction, effectively avoiding the deactivation and failure caused by metal impurities encapsulating the resin catalyst, improving the conversion rate of methyldichlorosilane, and effectively avoiding the disproportionation reaction of silicon trichloride in the presence of the resin catalyst, thereby improving the carbon removal efficiency and chlorosilane recovery efficiency.

[0009] The technical solution of this utility model to solve the above-mentioned technical problems is:

[0010] A system for removing impurities from carbon-containing chlorosilanes and recovering chlorosilanes is provided, comprising:

[0011] The first distillation column is used to receive and concentrate carbon-containing chlorosilanes. The chlorosilanes are recovered from the top of the column, and the bottom of the column yields a concentrated solution S4 containing methyl dichlorosilane and methyl trichlorosilane.

[0012] The first adsorption and reaction device is connected to the first distillation column. Its interior is filled with metal adsorption material. At the same time, the first adsorption and reaction device is equipped with a silicon tetrachloride feed pipeline for receiving concentrated liquid S4 and adsorbing metal impurities therein as a carbon removal catalyst, and for introducing silicon tetrachloride to adjust the silicon tetrachloride content in the concentrated liquid to a preset range, so as to promote the reaction of methyldichlorosilane with silicon tetrachloride to convert it into methyltrichlorosilane, and obtain material S7.

[0013] The second adsorption and reaction device is connected to the first adsorption and reaction device. Its interior is filled with methyl dichlorosilane adsorbent material to receive material S7 and to promote the continued reaction of the residual methyl dichlorosilane with silicon tetrachloride to completely convert it into methyl trichlorosilane, thereby obtaining material S8.

[0014] The second distillation column, connected to the second adsorption and reaction device, is used to receive material S8 and distill it to remove methyltrichlorosilane. The top of the column yields material containing trichlorosilane and silicon tetrachloride, and the bottom of the column yields material S11 containing methyltrichlorosilane.

[0015] The third distillation column, connected to the second distillation column, is used to receive the material containing trichlorosilane and silicon tetrachloride discharged from the top of the second distillation column and to separate its components to recover trichlorosilane and silicon tetrachloride.

[0016] Optionally, the first distillation column is provided with a first reflux line at the top of the column, and the reflux ratio is controlled at 3.8 to 5.

[0017] Optionally, the first adsorption and reaction device is directly connected to the bottom of the first distillation column via a first pipeline, and the silicon tetrachloride feed pipeline is indirectly connected to the first adsorption and reaction device via the first pipeline. The first pipeline is equipped with a component detection device, and the silicon tetrachloride feed pipeline is equipped with a first control valve. The component detection device is interlocked with the first control valve so that the silicon tetrachloride content in the concentrate discharged from the first distillation column is adjusted to a preset range before entering the first adsorption and reaction device.

[0018] Optionally, the metal adsorbent material is activated carbon, metal adsorption resin, molecular sieve, silica gel, or modified silica material, with a size of 10 to 100 mesh.

[0019] Optionally, the methyldichlorosilane adsorbent is a resin containing tertiary amine functional groups.

[0020] Optionally, the second distillation column is equipped with a second reflux line at the top, and the reflux ratio is controlled between 1 and 2.

[0021] Optionally, the first distillation column is equipped with a first reboiler, and the second reflux line is connected to the first reboiler to provide heat to the first reboiler using the overhead material S9 discharged from the second distillation column.

[0022] Optionally, the top of the third distillation column is equipped with a third reflux line, and the reflux ratio is controlled at 1 to 2.

[0023] Optionally, the bottom of the third distillation column is provided with a second pipeline, which is connected to the first pipeline, for conveying the silicon tetrachloride separated from the third distillation column to the first pipeline to adjust the silicon tetrachloride content in the concentrate.

[0024] Optionally, the system also includes a silicon tetrachloride storage tank, and a second pipeline is connected to the silicon tetrachloride storage tank for sending excess silicon tetrachloride to the silicon tetrachloride storage tank for storage.

[0025] The beneficial effects of this utility model's carbon-containing chlorosilane removal and chlorosilane recovery system include:

[0026] (1) By connecting the first adsorption and reaction device in series before the second adsorption and reaction device, the metal impurities in the carbon-containing chlorosilane can be adsorbed, enriched and concentrated, and the enriched and concentrated metal or metal chloride can be used as a catalyst for the carbon removal reaction. The catalyst itself is not an adsorption material. Compared with the prior art, the catalyst is fundamentally different. This can remove metal impurities and promote the reaction of methyldichlorosilane with silicon tetrachloride to generate methyltrichlorosilane, which plays a role in carbon removal. It can also reduce the amount of catalyst used. Moreover, compared with the prior art, it can also protect the existing carbon removal reaction catalyst resin, effectively avoid the deactivation and failure caused by metal impurities encapsulating the resin catalyst, extend its service life, and improve the conversion rate of methyldichlorosilane. At the same time, it can effectively avoid the disproportionation reaction of silicon trichloride caused by the presence of resin catalyst, reduce the ineffective consumption of raw materials in the polysilicon production process, thereby improving the carbon removal efficiency and chlorosilane recovery efficiency. The removal rate of dimethyltrichlorosilane in this system reaches more than 95%, which is much higher than the 70% of the prior art.

[0027] (2) By setting up a first distillation unit, trichlorosilane can be fully recovered by distillation technology before the decarbonization reaction, reducing the amount of chlorosilane processed by the adsorption and reaction units. This can improve the efficiency of trichlorosilane distillation in the polysilicon production process. At the same time, it can concentrate carbon-containing impurities and metal impurities in chlorosilane materials, completely eliminating the limitation of low-concentration methyldichlorosilane on the decarbonization reaction. This means that the conversion rate of methyldichlorosilane is not limited by the concentration of methyldichlorosilane, solving the problem of low conversion rate of low-concentration methyldichlorosilane reaction, which is beneficial to the subsequent decarbonization reaction.

[0028] (3) By setting up a three-stage distillation column, trichlorosilane in the material can be repeatedly recycled and reused, minimizing the waste of trichlorosilane material and reducing the consumption of silicon and chlorine elements in the polysilicon production process.

[0029] (4) By setting up the first, second and third reflux pipelines and reasonably controlling the reflux ratio and tower pressure of distillation towers T1, T2 and T3, it is possible to improve the recycling efficiency of trichlorosilane and silicon tetrachloride while ensuring the impurity removal effect, reduce the energy consumption in the recovery process of carbon-containing chlorosilanes, and improve the economy. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the carbon-containing chlorosilane removal and chlorosilane recovery system in an embodiment of this utility model.

[0031] In the diagram: T1 - First distillation column; T2 - Second distillation column; T3 - Third distillation column; R1 - First adsorption and reaction unit; R2 - Second adsorption and reaction unit; E1 - First column reboiler; E2 - First condenser; E3 - Second column reboiler; E4 - Second condenser; E5 - Third column reboiler; E6 - Third condenser; E7 - Circulating water heat exchanger; V1 - First reflux tank; V2 - Second reflux tank; V3 - Third reflux tank; P1 - First transfer pump; P2 - Second transfer pump; P3 - Third transfer pump; P4 - Fourth transfer pump; P5 - Fifth transfer pump; P6 - Sixth transfer pump. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution of this utility model, the technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0033] In the description of this utility model, it should be noted that the terms "above" and other indications of orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience and simplification of description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0034] In the description of this utility model, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] To address the problems of unsatisfactory removal efficiency of methyldichlorosilanes, easy deactivation and failure of resin catalysts, and disproportionation reactions of trichlorosilanes in existing technologies, this utility model discloses a system for removing carbon-containing chlorosilanes and recovering chlorosilanes, comprising:

[0036] The first distillation column is used to receive and concentrate chlorosilanes (e.g., all the de-removed residues from the distillation of trichlorosilane, which contains 50-100 ppm methyltrichlorosilane, 100-1000 ppm methyldichlorosilane, ≥95% trichlorosilane, and ≥4% silicon tetrachloride). The gaseous chlorosilanes produced during the concentration process are recovered from the top of the column, and the bottom of the column yields a concentrated liquid S4 containing methyldichlorosilane and methyltrichlorosilane.

[0037] The first adsorption and reaction device is connected to the bottom of the first distillation column. Its interior is filled with metal adsorption material. At the same time, the first adsorption and reaction device is equipped with silicon tetrachloride feed, which is used to receive the concentrated liquid S4 and adsorb the metal impurities therein as a carbon removal catalyst, and to introduce silicon tetrachloride to adjust the silicon tetrachloride content in the concentrated liquid, so as to promote the reaction of methyldichlorosilane with silicon tetrachloride to convert it into methyltrichlorosilane, and obtain material S7.

[0038] The second adsorption and reaction device is connected to the first adsorption and reaction device. Its interior is filled with methyl dichlorosilane adsorbent material to receive material S7 and to promote the continued reaction of the residual methyl dichlorosilane with silicon tetrachloride to completely convert it into methyl trichlorosilane, thus obtaining material S8.

[0039] The second distillation column, connected to the second adsorption and reaction unit, is used to receive material S8 and distill it to remove methyltrichlorosilane. The top of the column yields material containing trichlorosilane and silicon tetrachloride, and the bottom of the column yields material S11 containing methyltrichlorosilane.

[0040] The third distillation column, connected to the second distillation column, is used to receive the material containing trichlorosilane and silicon tetrachloride discharged from the top of the second distillation column, and to separate the trichlorosilane and silicon tetrachloride components to recover trichlorosilane and silicon tetrachloride.

[0041] This invention can adsorb, enrich, and concentrate metallic impurities in carbon-containing chlorosilanes, and use the enriched and concentrated metals or metal chlorides as catalysts for the carbon removal reaction. The catalyst itself is not an adsorbent material. Compared with existing technologies, the catalyst is fundamentally different. This can protect the existing carbon removal reaction catalyst resin, effectively avoid deactivation and failure caused by metallic impurities encapsulating the resin catalyst, extend its service life, and improve the conversion rate of methyldichlorosilane. At the same time, it effectively avoids the disproportionation reaction of silicon trichloride caused by the presence of the resin catalyst, thereby improving the carbon removal efficiency and chlorosilane recovery efficiency. This is of great significance for improving the quality and reducing consumption of the entire polysilicon industry.

[0042] Example 1

[0043] like Figure 1 As shown, this utility model discloses a carbon-containing chlorosilane impurity removal and chlorosilane recovery system, including 3 distillation columns, 2 sets of adsorption and reaction devices, as well as material conveying pumps and instruments and valves required for control.

[0044] The following is a detailed description of the system in this embodiment, using the processing of trichlorosilane S1 from the high-boiling recovery unit of the polycrystalline silicon hydrogenation distillation system as an example:

[0045] The first distillation column T1 is connected to the high-boiling recovery unit (not shown in the figure) of the polysilicon hydrogenation distillation system. It is used to receive the trichlorosilane-containing material S1 (i.e., carbochlorosilane-containing material) from the high-boiling recovery unit of the polysilicon hydrogenation distillation system and concentrate the methyldichlorosilane and methyltrichlorosilane therein. The top of the column is connected to the coarse material tank (not shown in the figure) of the polysilicon hydrogenation distillation system. The gaseous chlorosilane (mainly trichlorosilane) generated during the concentration process is collected from the top of the column and returned to the main distillation system of polysilicon production for recycling through the coarse material tank of the polysilicon hydrogenation distillation system. The bottom of the column yields a concentrated liquid S4 containing methyldichlorosilane and methyltrichlorosilane, which is discharged through the bottom residue discharge. The concentration of methyldichlorosilane and methyltrichlorosilane is 200-2000 mg / kg, and the bottom residue discharge is controlled to be 10-25% of the feed.

[0046] The first adsorption and reaction device R1 is connected to the bottom of the first distillation column T1 via the first transfer pump P1. Its interior is filled with metal adsorbent material. At the same time, the first adsorption and reaction device is equipped with a silicon tetrachloride feed line, which is used to receive the concentrate S4 and adsorb the metal impurities therein as a carbon removal catalyst, and to introduce silicon tetrachloride S5 to adjust the silicon tetrachloride content in the concentrate to a preset range (for example, adjusting the mass ratio of silicon tetrachloride and trichlorosilane to 1-4 to obtain material S6), so as to promote the reaction of methyldichlorosilane with silicon tetrachloride to convert it into methyltrichlorosilane, and obtain material S7.

[0047] The second adsorption and reaction device R2 is connected to the first adsorption and reaction device R1. It is filled with methyl dichlorosilane adsorbent material to receive material S7 and to promote the remaining low-boiling-point methyl dichlorosilane to continue to react with silicon tetrachloride to completely convert it into methyl trichlorosilane, thus obtaining material S8.

[0048] The second distillation column T2 is connected to the second adsorption and reaction device R2. It is used to receive material S8 and distill it to remove methyltrichlorosilane. The top of the column yields material containing trichlorosilane and silicon tetrachloride, and the bottom of the column yields material S11 containing methyltrichlorosilane. The bottom of the second distillation column T2 is equipped with a third transfer pump P3, which is used to transport material S11 to the downstream process for hydrolysis or external sale. The flow rate of material S11 is controlled at 150-500 kg / h to reduce the loss of chlorosilane.

[0049] The third distillation column T3 is connected to the second distillation column T2. ​​It is used to receive the material containing trichlorosilane and silicon tetrachloride discharged from the top of the second distillation column T2 and to separate its components to recover trichlorosilane and silicon tetrachloride (i.e., material S14).

[0050] In some embodiments, both the first adsorption and reaction device R1 and the second adsorption and reaction device R2 are fixed-bed reactors, and two fixed-bed reactors are used in parallel, one in operation and one on standby.

[0051] In some embodiments, the top of the first distillation column T1 is provided with a first reflux line for returning a portion of the chlorosilanes collected from the first distillation column T1 back to the first distillation column T1. The reflux ratio is controlled at 3.8 to 5, and the pressure inside the first distillation column T1 is controlled at 0.08 to 0.1 MPaG.

[0052] Specifically, such as Figure 1 As shown, the first reflux line includes a first condenser E2 and a first reflux tank V1. The first condenser E2 is connected to the top outlet of the first distillation column T1 to collect gaseous chlorosilane and cool and condense it to obtain liquid chlorosilane. The first reflux tank V1 is connected to the first condenser E2 to receive the refluxed liquid chlorosilane. At the same time, the first reflux tank V1 is also connected to the top or upper part of the first distillation column T1 and the coarse material tank (not shown in the figure) in the polycrystalline silicon hydrogenation distillation system through the second transfer pump P2, so that a portion of the liquid chlorosilane (i.e., material S3) is returned to the first distillation column T1, and another portion of the liquid chlorosilane (i.e., material S2) is returned to the main distillation system of polycrystalline silicon production (not shown in the figure) for recycling.

[0053] In some implementations, such as Figure 1 As shown, the first adsorption and reaction device R1 is directly connected to the bottom of the first distillation column T1 via a first pipeline. The first pipeline is equipped with a first delivery pump P1 and a circulating water heat exchanger E7. The silicon tetrachloride feed pipeline is indirectly connected to the first adsorption and reaction device R1 via the first pipeline, and a component detection device (not shown in the figure) is installed on the first pipeline. A first control valve (not shown in the figure) is installed on the silicon tetrachloride feed pipeline. The component detection device is interlocked with the first control valve. The device controls the opening and closing of the first control valve according to the component detection results, so that the silicon tetrachloride content in the concentrate discharged from the first distillation column T1 is adjusted to a preset range (for example, the mass ratio of silicon tetrachloride to trichlorosilane is 1 to 4) before entering the first adsorption and reaction device R1.

[0054] In some embodiments, the internal temperature of the first adsorption and reaction device R1 is controlled at 50-90°C, preferably 60-80°C, more preferably 60-70°C, and the pressure is controlled at 0.8-1.2 MPaG.

[0055] In some embodiments, the metal adsorbent can be activated carbon, commercially available metal adsorption resin (e.g., LXN-879 carbon adsorbent provided by a certain company, but not limited to this), molecular sieve, silica gel, or modified silica gel (e.g., macroporous silica gel provided by a Qingdao silica gel manufacturer, which can be customized to load metal elements on its framework for use as a catalyst and catalyst carrier) functional materials that adsorb metals, with a size of 10 to 100 mesh, preferably 30 to 40 mesh.

[0056] It should be noted that existing technologies only have a single-stage adsorption process, using a carbon removal resin as the adsorbent, which is also a catalyst to catalyze the conversion of methyldichlorosilane into methyltrichlorosilane. This carbon removal resin is susceptible to metal chlorides, causing adsorbent (catalyst) poisoning and affecting its lifespan. In contrast, the first adsorption and reaction device R1 in this system uses a metal adsorbent material to remove metal impurities beforehand, preventing them from entering the second adsorption and reaction device R2 and adversely affecting the carbon removal resin there. This solves the problem of the carbon removal resin being susceptible to metal chlorides in existing technologies.

[0057] In this embodiment, the modified silicon material can be prepared by: expanding the pores with a 5% sodium hydroxide solution or by directly loading metal elements onto the silicone.

[0058] In other embodiments, the metal adsorbent material may be replaced with a porous adsorbent material preloaded with a metal chloride or having a metal element capable of catalyzing the chlorination and dehydrogenation reaction of methyldichlorosilane. The metal chloride is one or more of FeCl3, FeCl2, AlCl3, CuCl2, and CuCl2, and the metal element is a metal element such as platinum, nickel, or palladium.

[0059] In some embodiments, the methyldichlorosilane adsorbent is a carbon removal resin, preferably a resin containing tertiary amine functional groups, such as a styrene-tertiary amine functional group resin.

[0060] In some embodiments, the internal temperature of the second adsorption and reaction device R2 is controlled at 60-80°C, preferably 60-70°C or 70-80°C, and the pressure is controlled at 0.8-1.2 MPaG. After treatment by the second adsorption and reaction device R2, the conversion rate of methylchlorosilane is ≥90%.

[0061] In some embodiments, the top of the second distillation column T2 is provided with a second reflux line, the reflux ratio is controlled at 1 to 2, and the pressure inside the second distillation column T2 is controlled at 0.3 to 0.45 MPaG.

[0062] Specifically, such as Figure 1As shown, the second reflux line includes a second condenser E4 and a second reflux tank V2. The second condenser E4 is connected to the top outlet of the second distillation column T2 to collect the material containing trichlorosilane and silicon tetrachloride and cool and condense it to obtain trichlorosilane and silicon tetrachloride condensate. The second reflux tank V2 is connected to the second condenser E4 to receive the refluxed trichlorosilane and silicon tetrachloride condensate. Simultaneously, the second reflux tank V2 is also connected to the top or upper part of the second distillation column T2 and the third distillation column T3 via a fourth transfer pump P4, so that a portion of the trichlorosilane and silicon tetrachloride condensate (i.e., material S10) returns to the second distillation column T2, while another portion of the trichlorosilane and silicon tetrachloride condensate (i.e., material S9) enters the third distillation column T3 for component separation.

[0063] In some embodiments, the reboiler of the first distillation column T1 is equipped with a first reboiler E1, and a second reflux line is connected to the first reboiler E1 to utilize the overhead material S9 discharged from the second distillation column T2 to provide heat to the first reboiler, thereby reducing the steam consumption of the first distillation column T1. The second condenser E4 is only used as a backup. The reboiler of the second distillation column T2 is equipped with a second reboiler E3.

[0064] In some implementations, the top of the third distillation column T3 is equipped with a third reflux line, and the reflux ratio is controlled at 1 to 2.

[0065] Specifically, such as Figure 1 As shown, the third reflux pipeline includes a third condenser E6 and a third reflux tank V3. The third condenser E6 is connected to the top outlet of the third distillation column T3 to collect gaseous trichlorosilane and cool and condense it to obtain trichlorosilane condensate. The third reflux tank V3 is connected to the third condenser E6 to receive the refluxed trichlorosilane condensate. Simultaneously, the third reflux tank V3 is also connected via a sixth transfer pump P6 to the top or upper part of the third distillation column T3 and the coarse feed tank in the polysilicon hydrogenation distillation system, respectively. This allows a portion of the trichlorosilane condensate (i.e., material S13) to return to the third distillation column T3, while another portion (i.e., material S12) is returned to the main distillation system for polysilicon production via the coarse feed tank in the polysilicon hydrogenation distillation system for recycling.

[0066] In some embodiments, the reboiler of the third distillation column T3 is equipped with a second pipeline, the other end of which is connected to the first pipeline. A fifth transfer pump P5 is installed on the second pipeline to transfer silicon tetrachloride (i.e., material S15) separated from the third distillation column containing a small amount of trichlorosilane to the first pipeline to adjust the silicon tetrachloride content in the concentrate, thereby reducing the amount of externally added silicon tetrachloride and lowering the power consumption of pumps due to the transport distance. The reboiler of the third distillation column T3 is equipped with a third reboiler E5.

[0067] In some embodiments, the other end of the second delivery pipeline is also connected to the cold hydrogenation coarse separation tower in the polysilicon production process, for conveying a portion of the silicon tetrachloride (i.e., material S16) separated from the third distillation tower containing a small amount of trichlorosilane to the cold hydrogenation coarse separation tower for recycling.

[0068] In some embodiments, the system also includes a silicon tetrachloride storage tank (not shown in the figure), and a second pipeline is connected to the silicon tetrachloride storage tank for sending excess silicon tetrachloride to the silicon tetrachloride storage tank for storage.

[0069] The carbon-containing chlorosilane removal and chlorosilane recovery system of this embodiment has at least the following beneficial effects:

[0070] (1) By connecting the first adsorption and reaction device in series before the second adsorption and reaction device, the metal impurities in the carbon-containing chlorosilane can be adsorbed, enriched and concentrated, and the enriched and concentrated metal or metal chloride can be used as a catalyst for the carbon removal reaction. The catalyst itself is not an adsorption material. Compared with the prior art, the catalyst is fundamentally different. This can remove metal impurities and promote the reaction of methyldichlorosilane with silicon tetrachloride to generate methyltrichlorosilane, which plays a role in carbon removal. It can also reduce the amount of catalyst used. Moreover, compared with the prior art, it can also protect the existing carbon removal reaction catalyst resin, effectively avoid the deactivation and failure caused by metal impurities encapsulating the resin catalyst, extend its service life, and improve the conversion rate of methyldichlorosilane. At the same time, it can effectively avoid the disproportionation reaction of silicon trichloride caused by the presence of resin catalyst, reduce the ineffective consumption of raw materials in the polysilicon production process, thereby improving the carbon removal efficiency and chlorosilane recovery efficiency. The removal rate of dimethyltrichlorosilane in this system reaches more than 95%, which is much higher than the 70% of the prior art.

[0071] (2) By setting up a first distillation unit, trichlorosilane can be fully recovered by distillation technology before the decarbonization reaction, reducing the amount of chlorosilane processed by the adsorption and reaction units. This can improve the efficiency of trichlorosilane distillation in the polysilicon production process. At the same time, it can concentrate carbon-containing impurities and metal impurities in chlorosilane materials, completely eliminating the limitation of low-concentration methyldichlorosilane on the decarbonization reaction. This means that the conversion rate of methyldichlorosilane is not limited by the concentration of methyldichlorosilane, solving the problem of low conversion rate of low-concentration methyldichlorosilane reaction, which is beneficial to the subsequent decarbonization reaction.

[0072] (3) By setting up a three-stage distillation column, trichlorosilane in the material can be repeatedly recycled and reused, minimizing the waste of trichlorosilane material and reducing the consumption of silicon and chlorine elements in the polysilicon production process.

[0073] (4) By setting up the first, second and third reflux pipelines and reasonably controlling the reflux ratio and tower pressure of distillation towers T1, T2 and T3, it is possible to improve the recycling efficiency of trichlorosilane and silicon tetrachloride while ensuring the impurity removal effect, reduce the energy consumption in the recovery process of carbon-containing chlorosilanes, and improve the economy.

[0074] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this utility model, and the utility model is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of this utility model, and these modifications and improvements are also considered to be within the protection scope of this utility model.

Claims

1. A system for removing impurities from carbon-containing chlorosilanes and recovering chlorosilanes, characterized in that, include: The first distillation column is used to receive and concentrate carbon-containing chlorosilanes. The chlorosilanes are recovered from the top of the column, and the bottom of the column yields a concentrated solution S4 containing methyl dichlorosilane and methyl trichlorosilane. The first adsorption and reaction device is connected to the first distillation column. Its interior is filled with metal adsorption material. At the same time, the first adsorption and reaction device is equipped with a silicon tetrachloride feed pipeline for receiving concentrated liquid S4 and adsorbing metal impurities therein as a carbon removal catalyst, and for introducing silicon tetrachloride to adjust the silicon tetrachloride content in the concentrated liquid to a preset range, so as to promote the reaction of methyldichlorosilane with silicon tetrachloride to convert it into methyltrichlorosilane, and obtain material S7. The second adsorption and reaction device is connected to the first adsorption and reaction device. Its interior is filled with methyl dichlorosilane adsorbent material to receive material S7 and to promote the continued reaction of the residual methyl dichlorosilane with silicon tetrachloride to completely convert it into methyl trichlorosilane, thereby obtaining material S8. The second distillation column, connected to the second adsorption and reaction device, is used to receive material S8 and distill it to remove methyltrichlorosilane. The top of the column yields material containing trichlorosilane and silicon tetrachloride, and the bottom of the column yields material S11 containing methyltrichlorosilane. The third distillation column, connected to the second distillation column, is used to receive the material containing trichlorosilane and silicon tetrachloride discharged from the top of the second distillation column and to separate its components to recover trichlorosilane and silicon tetrachloride.

2. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 1, characterized in that, The first distillation column is equipped with a first reflux line at the top of the column, and the reflux ratio is controlled between 3.8 and 5.

3. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 2, characterized in that, The first adsorption and reaction device is directly connected to the bottom of the first distillation column via a first pipeline. The silicon tetrachloride feed pipeline is indirectly connected to the first adsorption and reaction device via the first pipeline. A component detection device is installed on the first pipeline. A first control valve is installed on the silicon tetrachloride feed pipeline. The component detection device is interlocked with the first control valve so that the silicon tetrachloride content in the concentrate discharged from the first distillation column is adjusted to a preset range before entering the first adsorption and reaction device.

4. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 3, characterized in that, The metal adsorbent material is activated carbon, metal adsorption resin, molecular sieve, silica gel, or modified silica material, with a size of 10-100 mesh.

5. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 4, characterized in that, The methyldichlorosilane adsorbent is a resin containing tertiary amine functional groups.

6. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 5, characterized in that, The second distillation column is equipped with a second reflux line at the top, and the reflux ratio is controlled between 1 and 2.

7. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 6, characterized in that, The first distillation column is equipped with a first reboiler, and the second reflux line is connected to the first reboiler to provide heat to the first reboiler using the top material S9 discharged from the second distillation column.

8. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 7, characterized in that, The third distillation column is equipped with a third reflux line at the top, and the reflux ratio is controlled between 1 and 2.

9. The carbon-containing chlorosilane removal and chlorosilane recovery system according to any one of claims 3 to 8, characterized in that, The third distillation column is equipped with a second pipeline in its bottom, which is connected to the first pipeline. This second pipeline is used to transport the silicon tetrachloride separated from the third distillation column to the first pipeline to adjust the silicon tetrachloride content in the concentrate.

10. The carbon-containing chlorosilane removal and chlorosilane recovery system according to claim 9, characterized in that, The system also includes a silicon tetrachloride storage tank, and a second pipeline is connected to the silicon tetrachloride storage tank for sending excess silicon tetrachloride to the silicon tetrachloride storage tank for storage.

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