A method for recovering high boilers
By atomizing or vaporizing high-boiling-point substances during polysilicon production and then feeding them into a plasma reactor for pyrolysis, components such as trichlorosilane and silicon tetrachloride are separated, solving the problems of resource waste and increased costs caused by direct hydrolysis of high-boiling-point substances and achieving efficient recovery of high-boiling-point substances.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-03
- Publication Date
- 2026-03-31
AI Technical Summary
In the polysilicon industry, the direct hydrolysis of high-boiling-point substances leads to the consumption of chlorine, resulting in resource waste and increased costs.
High-boiling-point substances are atomized or vaporized and then fed into a plasma reactor. The reactor carrier gas decomposes the substances into components such as trichlorosilane and silicon tetrachloride, which are then separated by condensation and distillation, thus avoiding the direct hydrolysis and consumption of chlorine.
It improves the cracking efficiency of high-boiling-point substances, reduces resource waste, lowers production costs, and effectively utilizes silicon, chlorine, and hydrogen elements in high-boiling-point substances, thus achieving efficient recovery of high-boiling-point substances.
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Figure CN116835599B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polycrystalline silicon technology, and in particular to a method for recovering high-boiling-point substances. Background Technology
[0002] Polycrystalline silicon is a basic raw material for the photovoltaic industry. During its preparation, a portion of liquid high-boiling-point compounds with boiling points exceeding 70°C (commonly known as "high-boiling substances") are produced as byproducts, accounting for 7.0% to 8.0% of the crude monomer product. Although these high-boiling substances are 99% polychlorosilanes, their composition is very complex, and the boiling points of each component are relatively close, making it difficult to separate the components using common separation methods.
[0003] Currently, most polysilicon manufacturers still use the method of directly hydrolyzing high-boiling-point substances. That is, water reacts with high-boiling-point substances to eventually produce silicon dioxide, hydrogen, hydrogen chloride, etc. to recover the high-boiling-point substances. However, because the chlorine in the high-boiling-point substances is hydrolyzed, chlorine needs to be added to the system, which leads to increased chlorine consumption in polysilicon plants, resulting in a large amount of resource waste and increased costs. Summary of the Invention
[0004] In response to the above situation, the present invention provides a method for recovering high-boiling-point substances, aiming to solve the technical problem that most polysilicon plants currently use the method of directly hydrolyzing high-boiling-point substances, that is, reacting water with high-boiling-point substances to ultimately produce silicon dioxide, hydrogen, hydrogen chloride, etc. However, because the chlorine element in the high-boiling-point substances is hydrolyzed, chlorine element needs to be replenished to the system, which leads to increased chlorine consumption in polysilicon plants, causes a large amount of resource waste, and thus increases costs.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] This invention provides a method for recovering high-boiling-point substances, which mainly includes the following steps:
[0007] Step S1: Atomize or vaporize the high-boiling-point substance to obtain atomized or vaporized high-boiling-point substance;
[0008] Step S2: Decompose the atomized or vaporized high-boiling-point substance into a mixture including trichlorosilane, silicon tetrachloride, dichlorosilane and low-boiling-point substances;
[0009] Step S3: Condense the mixture obtained in step S2;
[0010] Step S4: Distill the mixture after condensation in step S3 to separate and recover the components of the mixture;
[0011] In step S2, when the atomized or vaporized high-boiling-point substance is cracked or vaporized, the atomized or vaporized high-boiling-point substance is fed into the plasma reactor and a reactor carrier gas is introduced into the plasma reactor.
[0012] The reactor carrier gas includes one or more of hydrogen, chlorine, and hydrogen chloride.
[0013] In some embodiments of the present invention, before step S3, the atomized high-boiling material or vaporized high-boiling material that has not been completely pyrolyzed in step S2 is returned to step S1 or step S2.
[0014] In some embodiments of the present invention, in step S3, the condensation temperature is 20–100°C.
[0015] In some embodiments of the present invention, in step S2, when the atomized high-boiling-point substance is cracked or vaporized, the atomized high-boiling-point substance or vaporized high-boiling-point substance is sent into the plasma reactor and a reactor carrier gas is introduced into the plasma reactor.
[0016] The reactor carrier gas includes one or more of hydrogen, chlorine, and hydrogen chloride.
[0017] In some embodiments of the present invention, in step S2, when the atomized high-boiling point is fed into the plasma reactor, the atomized high-boiling point is fed into the plasma reactor using atomizer carrier gas.
[0018] The carrier gas for atomizers includes one or more of hydrogen, chlorine, and hydrogen chloride.
[0019] In some embodiments of the present invention, the temperature of the plasma generated by the plasma reactor is 50 to 5000°C.
[0020] In some embodiments of the present invention, the reaction pressure of the plasma reactor is greater than 0 MPa and less than or equal to 10 MPa.
[0021] In some embodiments of the present invention, the total flow rate of gas in the plasma reactor is 0.1 to 10 m³ / min.
[0022] In some embodiments of the present invention, the plasma reactor includes:
[0023] A plasma generator includes an interconnected plasma torch inlet section and a plasma torch, the plasma torch inlet section having a carrier gas channel, and the plasma torch being used to generate plasma.
[0024] The material inlet is used to introduce atomized or vaporized high-boiling-point substances into the plasma reactor.
[0025] The plasma reaction zone, located between the material inlet and material outlet, has a carrier gas channel for introducing reactor carrier gas into the plasma torch, thereby delivering plasma into the plasma reaction zone.
[0026] The material outlet is connected in sequence to a condenser and a distillation column.
[0027] In some embodiments of the present invention, the material inlet includes a high-boiling channel and / or a high-boiling nozzle.
[0028] In some embodiments of the present invention, the material inlet includes a high-boiling channel;
[0029] The plasma torch inlet section has a sandwich structure, with the high-boiling channel and carrier gas channel located within the plasma torch inlet section and being relatively independent.
[0030] The embodiments of the present invention have at least the following advantages or beneficial effects:
[0031] 1. After atomized or vaporized high-boiling-point substances enter the plasma reaction zone, the unstable silicon-silicon bonds are broken by the high temperature. Trichlorosilane, silicon tetrachloride, and other raw materials required for polycrystalline silicon production are grafted onto the broken molecules. Trichlorosilane and silicon tetrachloride are then sent to the corresponding process sections through the corresponding pipelines to make effective use of the high-boiling-point substances in the high-boiling-point storage tank.
[0032] 2. The high-boiling-point substance recovery device does not consume chlorine from the high-boiling-point substance, so there is no need to replenish chlorine to the system, thus avoiding waste of resources and increased costs.
[0033] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0035] Figure 1 Flowchart of a high-boiling-point substance recovery method Figure 1 ;
[0036] Figure 2 Flowchart of a high-boiling-point substance recovery method Figure 2 ;
[0037] Figure 3 Flowchart of a high-boiling-point substance recovery method Figure 3 ;
[0038] Figure 4 This is a schematic diagram of the plasma reactor and atomizer provided in Example 1;
[0039] Figure 5 This is a schematic diagram of the heater provided in Example 2;
[0040] Figure 6 This is a schematic diagram showing a structure where the plasma torch inlet section and high-boiling nozzle are located at the bottom of the plasma reactor, while the material outlet is located at the top of the plasma reactor.
[0041] icon:
[0042] 1-High boiling point storage tank, 11-High boiling point storage tank outlet, 12-High boiling point storage tank reflux port, 13-Transfer pump,
[0043] 2-Atomizer, 21-Atomizer carrier gas inlet, 22-Atomizer high-boiling point inlet, 23-Atomizer high-boiling point outlet, 24-Atomizer large droplet outlet.
[0044] 3-Plasma reactor, 31-Plasma torch inlet section, 311-High-boiling channel, 312-Carrier gas channel, 32-High-boiling nozzle, 33-Plasma reaction zone, 331-Reaction tank area, 332-Bushing, 34-Material outlet.
[0045] 4-Distillation column, 41-Low boiling point outlet,
[0046] 5 - Heater, 51 - Heater high-boiling inlet, 52 - Heater high-boiling outlet. Detailed Implementation
[0047] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention.
[0048] In the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.
[0049] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0050] Example 1
[0051] Firstly, please refer to Figures 1-3 This embodiment provides a method for recovering high-boiling-point substances, which includes the following steps:
[0052] Step S1: Atomize or vaporize the high-boiling-point substance to obtain atomized or vaporized high-boiling-point substance;
[0053] In step S1, the high-boiling substances in the high-boiling storage tank are sent to an atomizer or heater for atomization or vaporization through high pressure, suction, pumping or other means to obtain atomized high-boiling substances or vaporized high-boiling substances.
[0054] Step S2: Pyrolysis of atomized high-boiling-point substances or vaporization of high-boiling-point substances;
[0055] In step S2, when pyrolyzing or vaporizing high-boiling-point substances, the atomized or vaporized high-boiling-point substances are fed into the plasma reactor, and a reactor carrier gas is introduced into the plasma reactor to pyrolyze the atomized or vaporized high-boiling-point substances into a mixture including trichlorosilane, silicon tetrachloride, dichlorosilane, and low-boiling-point substances; low-boiling-point substances and high-boiling-point substances are relative terms.
[0056] The reactor carrier gas can be one or more of hydrogen, chlorine and hydrogen chloride, and the reactor carrier gas can also include one or more of nitrogen, argon or helium.
[0057] In step S2, when the atomized high-boiling material is sent into the plasma reactor, the atomized high-boiling material is sent into the plasma reactor using atomizer carrier gas. The atomizer carrier gas can be one or more of hydrogen, chlorine and hydrogen chloride, and the atomizer carrier gas can also include one or more of nitrogen, argon or helium.
[0058] The plasma reactor is used to generate plasma with a temperature of 50–5000℃. The reaction pressure of the plasma reactor is greater than 0 MPa and less than or equal to 10 MPa. The total flow rate of the gas in the plasma reactor (i.e., the atomizer carrier gas and the reactor carrier gas) is 0.1–10 m³ / min.
[0059] Step S3: Condense the mixture obtained in step S2; the condensation temperature is 20-100℃.
[0060] Before step S3, the atomized or vaporized high-boiling-point substances that were not completely pyrolyzed in step S2 are returned to step S1 or step S2; or, during step S3, the high-boiling-point substances that were not completely pyrolyzed in step S2 are returned to step S1 or step S2.
[0061] Step S4: The mixture condensed in step S3 is distilled using a distillation column to separate and recover trichlorosilane, silicon tetrachloride, dichlorosilane and low-boiling substances.
[0062] Secondly, please refer to Figure 4This embodiment provides a high-boiling-point storage tank 1, which is used to store high-boiling-point substances produced as a byproduct in the preparation of polycrystalline silicon products; the high-boiling-point storage tank 1 has a high-boiling-point storage tank outlet 11 and a high-boiling-point storage tank reflux port 12.
[0063] Thirdly, please refer to Figure 4 This embodiment provides an atomizer 2, which is one or more of an ultrasonic atomizer 2, a compression atomizer 2, a mesh atomizer 2, etc.; the atomizer 2 has an atomizer carrier gas inlet 21, an atomizer high boiling inlet 22, an atomizer high boiling outlet 23, and an atomizer large droplet outlet 24.
[0064] The atomizer carrier gas inlet 21 is used to inject the atomizer carrier gas into the atomizer 2, and to send the atomized high-boiling material into the plasma reactor through the atomizer carrier gas; the atomizer carrier gas can be one or more of hydrogen, chlorine and hydrogen chloride; the atomizer carrier gas can also include one or more of nitrogen, argon or helium, and nitrogen, argon and helium are easy to form plasma.
[0065] The atomizer's high-boiling inlet 22 is connected to the high-boiling storage tank outlet 11 via a transfer pump 13. The atomizer's large droplet outlet 24 is connected to the high-boiling storage tank return port 12 via a pipeline.
[0066] Fourthly, please refer to Figure 4 This embodiment provides a plasma reactor, which is one or any combination of a DC plasma reactor, a microwave plasma reactor, and an inductively coupled plasma reactor; the plasma reactor 3 has a plasma generator, a high-boiling nozzle 32, a plasma reaction zone 33, and a material outlet 34.
[0067] The plasma generator includes an interconnected plasma torch inlet section 31 and a plasma torch (not shown in the figure). The plasma torch inlet section 31 is located at the top of the plasma reactor 3 and has a sandwich structure. The plasma torch inlet section 31 has a relatively independent high-boiling channel 311 and a reactor carrier gas channel 312. The high-boiling channel 311 is connected to the high-boiling outlet 23 of the atomizer. The reactor carrier gas channel 312 is used to inject the reactor carrier gas into the plasma reactor. The reactor carrier gas can be one or more of hydrogen, chlorine, and hydrogen chloride. The reactor carrier gas can also include one or more of nitrogen, argon, or helium. When the plasma reactor is a DC plasma reactor, the plasma torch has two electrodes (not shown in the figure). After discharge between the two electrodes, plasma is generated and blown into the plasma reaction region 33 by the reactor carrier gas. In order to blow the plasma into the plasma reaction region 33 by the reactor carrier gas, the amount of reactor carrier gas is relatively large.
[0068] The high-boiling channel 311 and the reactor carrier gas channel 312 are relatively independent. This facilitates the stable flow of plasma into the plasma reaction region 33 and allows for thorough mixing of the atomized high-boiling material with the plasma within the plasma reaction region 33, thereby increasing reaction efficiency. Specifically, the demand for reactor carrier gas is high in the plasma torch inlet section 31. When the reactor carrier gas volume is low, it can easily cause irreversible damage to the plasma generator. By making the high-boiling channel 311 and the reactor carrier gas channel 312 relatively independent in the plasma torch inlet section 31, it is convenient to control the amount of reactor carrier gas and the feed volume of atomized high-boiling material separately, thus facilitating a stable flow of plasma into the plasma reaction region 33 and avoiding irreversible damage to the plasma generator. At the same time, feeding both reactor carrier gas and atomized high-boiling material at the plasma torch inlet section 31 allows both the atomized high-boiling material and the plasma to enter the plasma reaction region 33 in a turbulent state, ensuring thorough mixing of the atomized high-boiling material and the plasma within the plasma reaction region 33, thereby increasing reaction efficiency.
[0069] The high-boiling nozzle 32 is connected to the high-boiling outlet 23 of the atomizer. The high-boiling nozzle 32 is located at the top of the plasma reactor 3. Multiple high-boiling nozzles 32 are arranged horizontally or obliquely downward to blow the atomized high-boiling material into the plasma reaction zone 33 to complete the reaction. A filter (not shown in the figure) is connected between the high-boiling inlet 22 of the atomizer and the outlet 11 of the high-boiling tank. The filter is used to remove precipitated impurities in the high-boiling material to reduce the pressure of the high-boiling nozzle 32.
[0070] The plasma reaction zone 33 is located between the plasma torch inlet section 31 and the material outlet 34; the plasma reaction zone 33 has a reaction tank area 331, and a bushing 332 is installed in the reaction tank area 331; the bushing 332 is made of high temperature resistant and corrosion resistant metal or non-metal materials such as graphite, stainless steel or polytetrafluoroethylene.
[0071] Material outlet 34 is located at the bottom of plasma reactor 3.
[0072] In this embodiment, the high-boiling nozzle 32 and the high-boiling channel 311 together constitute the material inlet of the plasma reactor 3.
[0073] The working principle of the above-mentioned plasma reactor is as follows:
[0074] After the high-boiling-point substances in the high-boiling-point storage tank 1 enter the atomizer 2, they are atomized into tiny liquid-like atomized high-boiling-point substances. The atomized carrier gas introduced through the atomizer carrier gas inlet 21 carries the atomized high-boiling-point substances through the high-boiling nozzle 32 and the high-boiling channel 311 into the plasma reaction zone 33. Large droplets formed due to incomplete atomization are separated from the tiny liquids by their own weight and return to the high-boiling-point storage tank 1. After the atomized high-boiling-point substances enter the plasma reaction zone 33, the unstable silicon-silicon bonds are broken by the high temperature. Trichlorosilane, silicon tetrachloride, and other raw materials required for polycrystalline silicon production are grafted onto the broken molecules. Trichlorosilane and silicon tetrachloride are then sent to the corresponding process sections through the corresponding pipelines for use, so as to effectively utilize the high-boiling-point substances in the high-boiling-point storage tank 1.
[0075] Fifthly, please refer to Figure 4 This embodiment provides a distillation column 4, the lower part of which is connected to the material outlet 34, and the upper part has a low-boiling outlet 41, which is used to discharge the low-boiling substances separated after distillation.
[0076] Compared to the direct hydrolysis of high-boiling-point substances, the high-boiling-point substance recovery method provided in this embodiment does not consume the chlorine element in the high-boiling-point substances, thus eliminating the need to replenish the system with chlorine, thereby avoiding resource waste and increased costs. At the same time, high-boiling-point substances are compounds of silicon, chlorine, and hydrogen. Direct hydrolysis would waste these elements, while the above-mentioned high-boiling-point substance recovery method can directly graft trichlorosilane, silicon tetrachloride, and other raw materials required for polycrystalline silicon production onto the broken-chain molecules. In other words, the above-mentioned high-boiling-point substance recovery method retains the silicon, chlorine, and hydrogen elements in the high-boiling-point substances and does not require an additional process to synthesize trichlorosilane and silicon tetrachloride, thereby reducing energy consumption.
[0077] In addition, this embodiment has at least the following beneficial effects:
[0078] 1. Due to the high temperature and high reactivity of plasma, the cracking efficiency of high-boiling-point substances is greatly improved, and a single-pass conversion rate of high-boiling-point substances of more than 90% can be achieved;
[0079] 2. The plasma reactor is small in size and occupies little space, and can be attached to existing production equipment as a small device to achieve online processing;
[0080] 3. The high-boiling-point recovery method has low production consumption and low cost, and does not require additional catalysts. All raw materials used in the high-boiling-point recovery method are used in large quantities on the production site.
[0081] Example 2
[0082] Please refer to Figure 4 and Figure 5 The difference between this embodiment and embodiment 1 is that in this embodiment, heater 5 is used instead of atomizer 2 in embodiment 1.
[0083] The heater 5 has a high-boiling inlet 51 and a high-boiling outlet 52. High-boiling substances in the high-boiling storage tank 1 can be sent into the heater 5 by means of high pressure, suction, pumping, etc. to vaporize the high-boiling substances and form vaporized high-boiling substances. For example, the high-boiling inlet 51 of the heater and the outlet 11 of the high-boiling storage tank are connected by a transfer pump 13.
[0084] Both the high-boiling nozzle 32 and the high-boiling channel 311 are connected to the high-boiling outlet 52 of the heater. After the high-boiling substances in the high-boiling storage tank 1 enter the heater 5, they vaporize to form vaporized high-boiling substances. The vaporized high-boiling substances are sent into the plasma reaction zone 33 through the high-boiling nozzle 32 and the high-boiling channel 311. After entering the plasma reaction zone 33, the unstable silicon-silicon bonds in the vaporized high-boiling substances are broken by the action of high temperature. Trichlorosilane, silicon tetrachloride and other raw materials required for the production of polycrystalline silicon are grafted onto the broken molecules. Trichlorosilane and silicon tetrachloride are sent to the corresponding process section through the corresponding pipelines for use, so as to effectively utilize the high-boiling substances in the high-boiling storage tank 1.
[0085] Example 3
[0086] The difference between this embodiment and Embodiment 1 or 2 is that, in this embodiment, either the high-boiling nozzle 32 or the high-boiling channel 311 used to deliver atomized or vaporized high-boiling substances to the plasma reaction zone 33 can be selected, and the two are not used simultaneously; that is, the material inlet of the plasma reactor 3 includes either the high-boiling nozzle 32 or the high-boiling channel 311.
[0087] Example 4
[0088] Please refer to Figure 6 The difference between this embodiment and embodiments 1, 2, or 3 is that, in this embodiment, the plasma torch inlet section 31 and the high-boiling nozzle 32 are located at the bottom of the plasma reactor 3, while the material outlet 34 is located at the top of the plasma reactor 3; that is, the material inlet and the carrier gas channel 312 are located at the bottom of the plasma reactor 3, while the material outlet 34 is located at the top of the plasma reactor 3.
[0089] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Without conflict, the embodiments and features described in the embodiments of this application can be arbitrarily combined with each other. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A high boiler recovery process characterized by, The method comprises the following steps: Step S1, atomizing or vaporizing the high-boiling substance to obtain atomized high-boiling substance or vaporized high-boiling substance; Step S2, cracking the atomized high-boiling substance or vaporized high-boiling substance into a mixture comprising trichlorosilane, silicon tetrachloride, dichlorosilane and low-boiling substance; Step S3, condensing the mixture obtained in step S2; Step S4, rectifying the mixture condensed in step S3 to separate and recover each component of the mixture; In step S2, when the atomized high-boiling substance or vaporized high-boiling substance is cracked, the atomized high-boiling substance or vaporized high-boiling substance is fed into a plasma reactor, and a reactor carrier gas is introduced into the plasma reactor; The reactor carrier gas comprises one of hydrogen, chlorine and hydrogen chloride gas.
2. The high boiler recovery process of claim 1, wherein, Before step S3, the atomized high-boiling substance or vaporized high-boiling substance that is not cracked in step S2 is returned to step S1 or step S2.
3. The high boiler recovery process of claim 1, wherein, In step S3, the condensation temperature is 20-100℃.
4. The high-boiling substance recovery method according to claim 1, wherein In step S2, when the atomized high-boiling substance is fed into the plasma reactor, the atomized high-boiling substance is fed into the plasma reactor by an atomizer carrier gas; The atomizer carrier gas comprises one of hydrogen, chlorine and hydrogen chloride gas.
5. The high boiler recovery process of claim 1 wherein, The temperature of the plasma generated by the plasma reactor is 50-5000℃.
6. The high boiler recovery process of claim 1 wherein, The reaction pressure of the plasma reactor is greater than 0 MPa and less than or equal to 10 MPa.
7. The high boiler recovery process of claim 1 wherein, The total flow rate of the gas in the plasma reactor is 0.1-10 m³ / min.
8. The high boiler recovery process according to any one of claims 1 to 7, characterized in that, The plasma reactor comprises: A plasma generator comprising a plasma torch gas inlet section and a plasma torch connected to each other, the plasma torch gas inlet section having a carrier gas passage, and the plasma torch being used to generate plasma; A material inlet for feeding the atomized high-boiling substance or vaporized high-boiling substance into the plasma reactor; A plasma reaction area located between the material inlet and a material outlet, the carrier gas passage being used to feed a reactor carrier gas into the plasma torch, and the plasma being fed into the plasma reaction area by the reactor carrier gas; and The material outlet is sequentially connected with a condenser and a rectifying column.
9. The high boiler recovery process of claim 8, wherein, The material inlet comprises a high-boiling passage and / or a high-boiling nozzle.
10. The high-boiling substance recovery method according to claim 9, wherein The material inlet comprises a high-boiling passage; The plasma torch gas inlet section has a sandwich structure, and the high-boiling passage and the carrier gas passage are located in the plasma torch gas inlet section and are relatively independent.
Citation Information
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