Separator coupling process for separation and purification of reduced and recovered chlorosilane

Abstract

The invention discloses a separation and purification partition plate coupling process for reducing and recovering chlorosilane. Two partition plate rectifying towers, a heat exchanger and accessory equipment are included. According to the invention, through the two serially-connected and coupled partition rectifying towers, not only is efficient separation of reduced and recovered chlorosilane components realized, but also the product is purified, the production requirements of a large reduction furnace and electronic-grade polycrystalline silicon are met, and compared with the prior art, the separation efficiency is remarkably improved, the impurity purity is reduced, the energy consumption of a separation system is greatly reduced, and the production cost is reduced. The method has excellent industrial application advantages.

Description

Technical Field

[0001] The invention belongs to the technical field of chlorosilane separation, and in particular relates to a partition coupling process for reducing, recovering, separating and purifying chlorosilane. Background Art

[0002] Polysilicon is the basic raw material for the photovoltaic industry and the semiconductor industry. At present, the main production process of polysilicon is the modified Siemens process. First, metallurgical silicon is reacted with hydrogen chloride to synthesize crude trichlorosilane, and then the crude trichlorosilane is distilled and purified to obtain high-purity trichlorosilane. Then, the high-purity trichlorosilane is converted into high-purity polysilicon through reduction reaction and chemical vapor deposition (CVD). The tail gas generated after reduction is dry-recovered, and the recovered hydrogen is returned to the reduction process. The recovered liquid chlorosilane is sent to the distillation device for component separation of chlorosilane. The separated high-purity trichlorosilane is returned to the reduction process, and silicon tetrachloride is sent to the cold hydrogenation process to prepare trichlorosilane. Dichlorodihydrosilane reacts with silicon tetrachloride to produce trichlorosilane and is also sent to the distillation process. The modified Siemens process realizes the closed-loop recycling of hydrogen and chlorosilane, and has the advantages of maturity, good safety performance, and easy expansion.

[0003] During the hydrogen reduction of trichlorosilane, the conversion rate of trichlorosilane is only about 10%, resulting in a large amount of unreacted trichlorosilane in the reduction tail gas, and the recovery process is bound to require a lot of energy consumption. At the same time, in addition to the by-products of silicon tetrachloride and dichlorosilane, the reduction reaction process will also produce polychlorosilanes such as hexachlorodisilane with a higher boiling point than silicon tetrachloride, as well as light impurities with a lower boiling point than dichlorosilane and heavy impurities with a boiling point between trichlorosilane and silicon tetrachloride. Therefore, the separation and purification process of the reduction recovery of chlorosilane is very important and is related to the quality of polysilicon products.

[0004] Patent CN105366681B discloses a method and device for treating chlorosilane recovered from the reduction production of polysilicon, and a method and system for treating chlorosilane in the production of polysilicon, which includes three distillation towers and ancillary equipment connected together. The device can only perform simple component separation and does not refine the product, resulting in a very low purity product that cannot meet the market's increasingly high quality requirements for polysilicon.

[0005] Patent CN209411790U discloses a distillation energy-saving device for purifying reduced chlorosilane, which adopts a distillation process consisting of three distillation towers, two of which are in a series structure. However, the process is very complicated, and the separated silicon tetrachloride does not remove high boiling substances, and the trichlorosilane product does not remove light and heavy impurities, resulting in low purity of the separated and recovered products, and has no application value. Summary of the invention

[0006] To solve the above problems, the present invention proposes a baffle coupling process for separation and purification of reduced and recovered chlorosilane. With reduced and recovered chlorosilane as raw material, two baffle distillation towers connected in series and coupled are used to not only realize efficient separation of reduced and recovered chlorosilane components, but also purify the products, thereby meeting the production requirements of large-scale reduction furnaces and electronic-grade polysilicon. Compared with the existing process, the separation efficiency is significantly improved, the impurity purity is reduced, and the energy consumption of the separation system is greatly reduced, thereby having excellent industrial application advantages.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A partition coupling process for separation and purification of chlorosilane for reduction recovery, using a separation and purification process integrating partition distillation and thermal coupling technology to separate and purify components of chlorosilane for reduction recovery, comprising the following steps:

[0009] Step 1: Reduction and recovery of chlorosilane enters from the middle and upper part of the feed side of the partition of the partition distillation tower. The rising gas phase on both sides of the partition of the partition distillation tower converges in the common distillation section above the partition, and the descending liquid phase on both sides of the partition converges in the common stripping section at the bottom of the partition. The liquid phase at the bottom of the common distillation section is distributed to both sides of the partition according to product demand at a mass ratio of 0.3:1 to 1.2:1; trichlorosilane and dichlorodihydrosilane with a silicon tetrachloride content of less than 50ppm are obtained from the top of the partition distillation tower, and silicon tetrachloride with a trichlorosilane content of less than 50ppm and a high boiling point (Si2Cl6) content of less than 0.1ppm is obtained from the middle and lower part of the partition extraction side of the partition distillation tower, and high boiling points with a boiling point higher than silicon tetrachloride are discharged from the tower kettle of the partition distillation tower.

[0010] Step 2: trichlorosilane and dichlorosilane obtained from the top of the partition distillation tower 1 enter from the middle and upper part of the partition feed side of the partition distillation tower 2, the gas phase rising on both sides of the partition of the partition distillation tower 2 converges at the common distillation section above the partition, the liquid phase descending on both sides of the partition converges at the common distillation section at the bottom of the partition, and the liquid phase at the bottom of the common distillation section is distributed to both sides of the partition according to product requirements at a mass ratio of 0.1:1 to 1:1; light impurities are discharged from the top of the partition distillation tower 2, dichlorosilane with a light impurity content of less than 15 ppm is obtained from the common distillation section side of the partition distillation tower 2, high-purity trichlorosilane with a heavy impurity content of less than 1.0 ppm is obtained from the middle and lower part of the partition extraction side of the partition distillation tower 2, and the heavy impurities are discharged from the kettle of the partition distillation tower 2.

[0011] The present invention also provides a baffle coupling system for reducing, recovering, separating and purifying chlorosilane, comprising: a baffle distillation tower 1, a baffle distillation tower 2, a baffle distillation tower 1 reboiler, a baffle distillation tower 1 condenser, a baffle distillation tower 2 reboiler and a baffle distillation tower 2 condenser.

[0012] A vertical partition is arranged in the partition plate distillation tower to divide the partition plate distillation tower into a common distillation section, a partition plate feed side, a partition plate extraction side and a common stripping section.

[0013] A vertical partition is arranged in the partition plate distillation tower, which divides the partition plate distillation tower into a common distillation section, a partition plate feed side, a partition plate extraction side and a common stripping section.

[0014] The tower top gas phase outlet of the partition distillation tower one is respectively connected to the shell side gas phase inlet of the partition distillation tower one condenser and the shell side gas phase inlet of the partition distillation tower two reboiler; the shell side liquid phase outlet of the partition distillation tower one condenser and the shell side liquid phase outlet of the partition distillation tower two reboiler are combined and respectively connected to the tower top reflux port of the partition distillation tower one and the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride.

[0015] A feed port is arranged at the middle and upper part of the partition feed side of the partition distillation tower, which is connected to the reduction and recovery pipeline of chlorosilane; a silicon tetrachloride production port is arranged at the middle and lower part of the partition production side, which is connected to the silicon tetrachloride discharge pipeline for removing trichlorosilane and high boiling products.

[0016] The liquid phase inlet of the reboiler of the partition plate distillation tower is connected to the tower kettle, the gas phase outlet of the reboiler is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the high-boiling material discharge pipeline.

[0017] The top gas phase outlet of the partition plate distillation tower is connected to the shell side gas phase inlet of the partition plate distillation tower condenser, and the shell side liquid phase outlet of the partition plate distillation tower condenser is respectively connected to the top reflux port of the partition plate distillation tower and the light impurity discharge pipeline.

[0018] A feed port is provided at the middle and upper part of the partition feed side of the partition distillation tower 2, which is connected to the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride; a liquid dichlorosilane extraction port is provided at the middle part of the common distillation section, which is connected to the dichlorosilane discharge pipeline; a high-purity trichlorosilane extraction port is provided at the middle and lower part of the partition extraction side, which is connected to the high-purity trichlorosilane discharge pipeline.

[0019] The liquid phase inlet of the partition plate distillation second tower reboiler is connected to the tower kettle, the gas phase outlet of the reboiler is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the heavy impurity discharge pipeline.

[0020] Preferably, the theoretical plate number of the common distillation section of the partition distillation tower is 35-55, the theoretical plate number of the partition feed side is 60-80, the theoretical plate number of the partition extraction side is 60-80 and the theoretical plate number of the common stripping section is 10-30.

[0021] Preferably, the number of theoretical plates of the common distillation section of the two partition distillation towers is 35-55, the number of theoretical plates on the partition feed side is 50-70, the number of theoretical plates on the partition extraction side is 50-70 and the number of theoretical plates of the common stripping section is 10-30.

[0022] Preferably, the top pressure of the partition plate distillation tower is 0.6-0.8 MPaG, the top temperature is 90-110° C., and the reflux ratio is 1.5:1-3:1.

[0023] Preferably, the top pressure of the partition plate distillation tower 2 is 0.2-0.4 MPaG, the top temperature is 40-60° C., and the reflux ratio is 250:1-350:1.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] The present invention provides a partition coupling process for separation and purification of chlorosilane for reduction recovery. The separation and purification process using partition distillation and thermal coupling technology can not only achieve efficient separation of chlorosilane for reduction recovery, but also purify the product to meet the production requirements of large-scale reduction furnaces and electronic-grade polysilicon. Compared with the existing process, the separation efficiency is significantly improved, the impurity purity is reduced, and the impurity content of a single chlorosilane product is reduced by more than 80%, and the energy consumption of the device is also reduced by more than 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 The present invention discloses an equipment structure and a flow chart of a baffle coupling system for reducing, recovering, separating and purifying chlorosilane, wherein: T1, baffle distillation tower 1, T2, baffle distillation tower 2, E1, baffle distillation tower 1 reboiler, E2, baffle distillation tower 1 condenser, E3, baffle distillation tower 2 reboiler, E4, baffle distillation tower 2 condenser; T1-1, baffle distillation tower 1 common distillation section, T1-2, baffle distillation tower 1 baffle feed side, T1-3, baffle distillation tower 1 baffle extraction side, T1-4, baffle distillation tower 1 common stripping section, T2-1, baffle distillation tower 2 common distillation section, T2-2, baffle distillation tower 2 baffle feed side, T2-3, baffle distillation tower 2 extraction side, T2-4, baffle distillation tower 2 common stripping section.

[0028] Figure 2It is a process flow chart in Comparative Example 1, wherein: T3, reduction distillation tower one, T4, reduction distillation tower two, E5, reboiler of reduction distillation tower one, E6, condenser of reduction distillation tower one, E7, reboiler of reduction distillation tower two, E8, condenser of reduction distillation tower two; T3-1, distillation section of reduction distillation tower one, T3-2, stripping section of reduction distillation tower one, T4-1, distillation section of reduction distillation tower two, T4-2, stripping section of reduction distillation tower two. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] The terms "first", "second", "T1", "T2", "E1", "E2", "T1-1", "T1-2", "T1-3", "T1-4", etc. are only used to distinguish descriptions and are not to be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. The term "vertical" in the present invention is vertical relative to the ground.

[0035] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] All raw materials used in the embodiments of the present invention are commercially available.

[0037] The present invention provides a partition coupling process for reducing, recovering, separating and purifying chlorosilane, the process flow chart is as follows: Figure 1 The partition coupling system includes a partition distillation tower T1, a partition distillation tower T2, a partition distillation tower reboiler E1, a partition distillation tower condenser E2, a partition distillation tower reboiler E3 and a partition distillation tower condenser E4.

[0038] A vertical partition is arranged inside the partition plate distillation tower T1, which divides the partition plate distillation tower T1 into a common distillation section T1-1, a partition plate feed side T1-2, a partition plate extraction side T1-3 and a common stripping section T1-4.

[0039] The tower top gas phase outlet of the partition distillation tower T1 is respectively connected to the shell side gas phase inlet of the partition distillation tower T1 condenser E2 and the shell side gas phase inlet of the partition distillation tower T2 reboiler E3; the shell side liquid phase outlet of the partition distillation tower T1 condenser E2 and the shell side liquid phase outlet of the partition distillation tower T2 reboiler E3 are combined and respectively connected to the tower top reflux port of the partition distillation tower T1 and the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride.

[0040] A feed port is provided at the upper middle part of the partition feed side T1-2 of the partition distillation tower T1, which is connected to the reduction recovery chlorosilane pipeline; a silicon tetrachloride production port is provided at the lower middle part of the partition production side T1-3, which is connected to the silicon tetrachloride discharge pipeline for removing trichlorosilane and high boiling products.

[0041] The liquid phase inlet of the reboiler E1 of the partition distillation tower T1 is connected to the tower kettle, the gas phase outlet of the reboiler E1 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the high-boiling material discharge pipeline.

[0042] A liquid collecting and redistributing device is provided at the bottom of the common distillation section T1-1 of the partition distillation tower T1, and the liquid is distributed to both sides of the partition at a mass ratio of 0.3:1 to 1.2:1 according to product requirements.

[0043] A vertical partition is arranged inside the partition plate distillation tower T2 to divide the partition plate distillation tower T2 into a common distillation section T2-1, a partition plate feed side T2-2, a partition plate extraction side T2-3 and a common stripping section T2-4.

[0044] The top gas phase outlet of the partition distillation tower T2 is connected to the shell side gas phase inlet of the partition distillation tower T2 condenser E4, and the shell side liquid phase outlet of the partition distillation tower T2 condenser E4 is respectively connected to the top reflux port of the partition distillation tower T2 and the light impurity discharge pipeline.

[0045] A feed port is provided at the middle and upper part of the partition feed side T2-2 of the partition distillation second tower T2, which is connected to the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride; a dichlorosilane production port is provided at the middle part of the common distillation section T2-1, which is connected to the dichlorosilane discharge pipeline; a high-purity trichlorosilane production port is provided at the middle and lower part of the partition production side T2-3, which is connected to the high-purity trichlorosilane discharge pipeline.

[0046] The liquid phase inlet of the reboiler E3 of the partition plate distillation second tower T2 is connected to the tower kettle, the gas phase outlet of the reboiler E3 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the heavy impurity discharge pipeline.

[0047] A liquid collecting and redistributing device is provided at the bottom of the common distillation section T2-1 of the partition distillation second tower T2, and the liquid is distributed to both sides of the partition at a mass ratio of 0.1:1 to 1:1 according to product requirements.

[0048] In some embodiments of the present invention, the theoretical plate number of the public distillation section T1-1 of the partition distillation tower T1 is 35 to 55, the theoretical plate number of the partition feed side T1-2 is 60 to 80, the theoretical plate number of the partition extraction side T1-3 is 60 to 80, and the theoretical plate number of the public stripping section T1-4 is 10 to 30. The partitions inside the partition distillation tower T1 can be centrally arranged or eccentrically arranged, which is determined by calculation based on the raw material composition and separation index.

[0049] In some embodiments of the present invention, the theoretical plate number of the public distillation section T2-1 of the partition distillation second tower T2 is 35 to 55, the theoretical plate number of the partition feed side T2-2 is 50 to 70, the theoretical plate number of the partition extraction side T2-3 is 50 to 70, and the theoretical plate number of the public stripping section T2-4 is 10 to 30. The partitions inside the partition distillation second tower T2 can be centrally arranged or eccentrically arranged, which is calculated and determined according to the raw material composition and separation index.

[0050] In some embodiments of the present invention, the top pressure of the partition plate distillation tower (T1) is 0.6-0.8 MPaG, the top temperature is 90-110° C., and the reflux ratio is 1.5:1-3:1.

[0051] In some embodiments of the present invention, the top pressure of the partition plate distillation tower (T2) is 0.2-0.4 MPaG, the top temperature is 40-60° C., and the reflux ratio is 250:1-350:1.

[0052] The technical solution of the present invention is further illustrated by the following embodiments.

[0053] Example 1

[0054] This example uses the reduction and recovery of chlorosilane processing capacity of 410892 kg / h for calculation and explanation.

[0055] according to Figure 1 The process flow is used to separate and purify chlorosilane for reduction recovery. The baffle coupling system for separation and purification of chlorosilane for reduction recovery includes baffle distillation tower T1, baffle distillation tower T2, baffle distillation tower reboiler E1 (a thermosyphon reboiler using 0.5MPaG saturated steam as a heat source), baffle distillation tower condenser E2 (a condenser using circulating water as a condensing medium), baffle distillation tower reboiler E3 and baffle distillation tower condenser E4 (a The condenser uses circulating water as the condensing medium); the top pressure of the baffle distillation tower T1 is 0.63MPaG, the top temperature is 101.2℃, the top reflux ratio is 2.2:1, and the material temperature controlled by the condenser E2 of the baffle distillation tower is 90℃; the top pressure of the baffle distillation tower T2 is 0.35MPaG, the top temperature is 55.9℃, the top reflux ratio is 299:1, and the material temperature controlled by the condenser E4 of the baffle distillation tower is 46℃.

[0056] A vertical partition is arranged in the middle of the partition distillation tower T1, dividing the partition distillation tower T1 into a common distillation section T1-1, a partition feed side T1-2, a partition withdrawal side T1-3 and a common stripping section T1-4; the common distillation section T1-1, the partition feed side T1-2, the partition withdrawal side T1-3 and the common stripping section T1-4 are filled with separation elements of a structured packing-tower tray composite, the theoretical plate number of the common distillation section T1-1 is 45, the theoretical plate number of the partition feed side T1-2 is 75, the theoretical plate number of the partition withdrawal side T1-3 is 75, and the theoretical plate number of the common stripping section T1-4 is 15.

[0057] The tower top gas phase outlet of the partition distillation tower T1 is respectively connected to the shell side gas phase inlet of the partition distillation tower T1 condenser E2 and the shell side gas phase inlet of the partition distillation tower T2 reboiler E3; the shell side liquid phase outlet of the partition distillation tower T1 condenser E2 and the shell side liquid phase outlet of the partition distillation tower T2 reboiler E3 are combined and respectively connected to the tower top reflux port of the partition distillation tower T1 and the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride.

[0058] The partition feed side T1-2 of the partition distillation tower T1 has a theoretical plate number of 6 and is provided with a feed port, which is connected to the reduction and recovery chlorosilane pipeline; the partition output side T1-3 has a theoretical plate number of 61 and is provided with a silicon tetrachloride output port, which is connected to the silicon tetrachloride discharge pipeline for removing trichlorosilane and high boiling points.

[0059] The liquid phase inlet of the reboiler E1 of the partition distillation tower T1 is connected to the tower kettle, the gas phase outlet of the reboiler E1 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the high-boiling material discharge pipeline.

[0060] A liquid collecting and redistributing device is provided at the bottom of the common distillation section T1-1 of the partition distillation tower T1, and the liquid is distributed to the partition feed side and the partition output side at a mass ratio of 0.53:1 according to product demand.

[0061] A vertical partition is arranged in the partition plate distillation tower T2, dividing the partition plate distillation tower T2 into a common distillation section T2-1, a partition plate feed side T2-2, a partition plate extraction side T2-3 and a common stripping section T2-4; the common distillation section T2-1, the partition plate feed side T2-2, the partition plate extraction side T2-3 and the common stripping section T2-4 are filled with separation elements of a structured packing-tower tray composite, the theoretical plate number of the common distillation section T2-1 is 45, the theoretical plate number of the partition plate feed side T2-2 is 60, the theoretical plate number of the partition plate extraction side T2-3 is 60, and the theoretical plate number of the common stripping section T2-4 is 15.

[0062] The top gas phase outlet of the partition distillation tower T2 is connected to the shell side gas phase inlet of the partition distillation tower T2 condenser E4, and the shell side liquid phase outlet of the partition distillation tower T2 condenser E4 is respectively connected to the top reflux port of the partition distillation tower T2 and the light impurity discharge pipeline.

[0063] The theoretical plate number of the partition feed side T2-2 of the partition distillation second tower T2 is 31, and a feed port is provided, which is connected to the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride; the theoretical plate number of the common distillation section T2-1 is 16, and a dichlorosilane production port is provided, which is connected to the dichlorosilane discharge pipeline; the theoretical plate number of the partition production side T2-3 is 46, and a high-purity trichlorosilane production port is provided, which is connected to the high-purity trichlorosilane discharge pipeline.

[0064] The liquid phase inlet of the reboiler E3 of the partition plate distillation second tower T2 is connected to the tower kettle, the gas phase outlet of the reboiler E3 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the heavy impurity discharge pipeline.

[0065] A liquid collecting and redistributing device is provided at the bottom of the common distillation section T2-1 of the partition distillation second tower T2, and the liquid is distributed to the partition feed side and the partition withdrawal side at a mass ratio of 0.137:1 according to product demand.

[0066] The reduced chlorosilane with a pressure of 0.9 MPaG and a temperature of 80°C is fed from the feed port of the baffle feed side T1-2 of the baffle distillation tower T1. According to the above-mentioned appropriate tower structure and optimized operating conditions, the calculation results are as follows:

[0067] The heating capacity of the reboiler E1 of the baffle distillation tower T1 is 39124kw;

[0068] The energy consumption of condenser E2 of baffle distillation tower T1 is -17291kw, the energy consumption of condenser E4 of baffle distillation tower T2 is -19266kw, and the total cooling load is -36557kw.

[0069] The material balance table of the embodiment is shown in Table 1.

[0070]

[0071] Comparative Example 1

[0072] according to Figure 2The process flow is to carry out conventional reduction recovery and separation and purification of chlorosilane, and the conventional reduction recovery and separation and purification device includes a reduction distillation tower T3, a reduction distillation tower T4, a reboiler E5 of the reduction distillation tower (a thermosyphon reboiler using 0.5MPaG saturated steam as a heat source), a condenser E6 of the reduction distillation tower (a condenser using circulating water as a condensing medium), a reboiler E7 of the reduction distillation tower (a thermosyphon reboiler using 0.2MPaG saturated steam as a heat source), The condenser E8 of the reduction distillation tower 2 (which is a condenser using circulating water as the condensing medium); the top pressure of the reduction distillation tower T3 is 0.63 MPaG, the top temperature is 101.2°C, the top reflux ratio is 2.2:1, and the material temperature controlled by the condenser E6 of the reduction distillation tower 1 is 90°C; the top pressure of the reduction distillation tower T4 is 0.35 MPaG, the top temperature is 55.9°C, the top reflux ratio is 299:1, and the material temperature controlled by the condenser E8 of the reduction distillation tower 2 is 46°C.

[0073] The reducing distillation tower T3 is divided into a reducing distillation tower distillation section T3-1 and a reducing distillation tower stripping section T3-2. The distillation section T3-1 and the stripping section T3-2 are filled with separation elements of a structured packing-tower tray composite. The theoretical number of plates of the distillation section T3-1 is 60, and the theoretical number of plates of the stripping section T3-2 is 75.

[0074] The top gas phase outlet of the reducing distillation tower T3 is connected to the shell side gas phase inlet of the condenser E6 of the reducing distillation tower T3, and the shell side liquid phase outlet of the condenser E6 of the reducing distillation tower T3 is respectively connected to the top reflux port of the reducing distillation tower T3, and the trichlorosilane and dichlorosilane discharge pipelines for removing silicon tetrachloride.

[0075] The theoretical plate number of the stripping section T3-2 of the reducing distillation tower T3 is 46, and a silicon tetrachloride production outlet is provided, which is connected to the silicon tetrachloride discharge pipeline for removing trichlorosilane and high boiling substances.

[0076] The liquid phase inlet of the reboiler E5 of the reduction distillation tower T3 is connected to the tower kettle, the gas phase outlet of the reboiler E5 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the high-boiling material discharge pipeline;

[0077] The liquid phase inlet of the reboiler E1 of the partition distillation tower T1 is connected to the tower kettle, the gas phase outlet of the reboiler E1 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the high-boiling material discharge pipeline.

[0078] The reducing distillation tower T4 is divided into a reducing distillation tower rectifying section T4-1 and a reducing distillation tower stripping section T4-2. The rectifying section T3-1 and the stripping section T3-2 are filled with structured packing-tower tray composite separation elements. The theoretical plate number of the rectifying section T4-1 is 60, and the theoretical plate number of the stripping section T4-2 is 60.

[0079] The top gas phase outlet of the reducing distillation tower T4 is connected to the shell side gas phase inlet of the condenser E8 of the reducing distillation tower T4, and the shell side liquid phase outlet of the condenser E8 of the reducing distillation tower T4 is respectively connected to the top reflux port of the reducing distillation tower T4 and the dichlorosilane discharge pipeline.

[0080] The theoretical plate number of the stripping section T4-2 of the second reduction and rectification tower T4 is 46, and a high-purity trichlorosilane production outlet is provided, which is connected to the high-purity trichlorosilane discharge pipeline.

[0081] The liquid phase inlet of the reboiler E7 of the second reduction distillation tower T4 is connected to the tower kettle, the gas phase outlet of the reboiler E7 is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the heavy impurity discharge pipeline.

[0082] The reduction recovery chlorosilane with a pressure of 0.9 MPaG and a temperature of 80°C is fed from the feed port T3-1 at the bottom of the distillation section of the reduction distillation tower T3. According to the above-mentioned suitable tower structure and the same operating conditions as in Example 1, the calculation results are as follows:

[0083] The heating capacity of the reboiler E5 of the reduction distillation tower T3 is 39122kw, the heating capacity of the reboiler E7 of the reduction distillation tower T4 is 18661kw, and the total heat load is 57783kw;

[0084] The energy consumption of condenser E6 of reduction distillation tower T3 is -35957kw, the energy consumption of condenser E8 of reduction distillation tower T4 is -19266kw, and the total cooling load is -55223kw.

[0085] The material balance table of the embodiment is shown in Table 1.

[0086]

[0087] The comparison between Example 1 and Comparative Example 1 is shown in Tables 3-4:

[0088] Table 3 Comparison of products of Example 1 and Comparative Example 1

[0089] Comparison Items Example 1 Comparative Example 1 Impurity content reduction ratio <![CDATA[ppm of Si2Cl6 content in silicon tetrachloride]]> ＜0.1 56.8 99.0％ Light impurity content in dichlorosilane ppm 10.3 163 93.7％ Heavy impurity content in trichlorosilane ppm 0.8 6.0 86.7％

[0090] Table 4 Comparison of energy consumption of Example 1 and Comparative Example 1

[0091] Comparison Items Example 1 Comparative Example 1 Energy saving ratio Heat load kw 39124 57783 32.3％ Cooling load kw 36557 55223 33.8％

[0092] By comparing Table 3 and Table 4, it can be found that, thanks to the separation and purification process integrated with the baffle distillation and thermal coupling technology, not only the efficient separation of the reduction recovery of chlorosilane is achieved, but also the product is purified to meet the production requirements of large-scale reduction furnaces and electronic-grade polysilicon. The baffle reaction distillation process coupled with the reaction distillation and baffle distillation technology, the process presented by the present invention, compared with the two-tower process using conventional distillation, has higher separation efficiency, less product impurity content, and lower energy consumption.

[0093] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A partition coupling process for reduction recovery, separation and purification of chlorosilane, characterized in that: The following steps are involved: Step 1: reducing chlorosilane enters from the middle and upper part of the partition feed side (T1-2) of the partition distillation tower (T1), the gas phase rising on both sides of the partition of the partition distillation tower (T1) converges in the common distillation section (T1-1) above the partition, the liquid phase descending on both sides of the partition converges in the common stripping section (T1-4) at the bottom of the partition, and the liquid phase at the bottom of the common distillation section (T1-1) is distributed to both sides of the partition; trichlorosilane and dichlorodihydrosilane from which silicon tetrachloride is removed are obtained from the top of the partition distillation tower (T1), silicon tetrachloride from which trichlorosilane and high boiling substances are removed is obtained from the middle and lower part of the partition extraction side (T1-3) of the partition distillation tower (T1), and high boiling substances with a boiling point higher than silicon tetrachloride are discharged from the tower kettle of the partition distillation tower (T1). Step 2: trichlorosilane and dichlorosilane obtained from the top of the partition distillation tower (T1) enter from the middle and upper part of the partition feed side (T2-2) of the partition distillation tower (T2) of the partition distillation tower (T2); the gas phase rising on both sides of the partition of the partition distillation tower (T2) converges in the common distillation section (T2-1) above the partition; the liquid phase descending on both sides of the partition converges in the common distillation section (T2-4) at the bottom of the partition; the liquid phase at the bottom of the common distillation section (T2-1) is distributed to both sides of the partition; light impurities are discharged from the top of the partition distillation tower (T2); dichlorosilane is obtained from the side of the common distillation section (T2-1) of the partition distillation tower (T2); high-purity trichlorosilane is obtained from the middle and lower part of the partition extraction side (T2-3) of the partition distillation tower (T2); and heavy impurities are discharged from the bottom of the partition distillation tower (T2).

2. A partition coupling process for reduction recovery and separation and purification of chlorosilane according to claim 1, characterized in that: A vertical partition is arranged in the partition plate distillation tower (T1) to divide the partition plate distillation tower into a common distillation section (T1-1), a partition plate feed side (T1-2), a partition plate extraction side (T1-3) and a common stripping section (T1-4). The number of theoretical plates of the common distillation section (T1-1) of the partition distillation tower (T1) is 35 to 55, the number of theoretical plates of the partition feed side (T1-2) is 60 to 80, the number of theoretical plates of the partition extraction side (T1-3) is 60 to 80, and the number of theoretical plates of the common stripping section (T1-4) is 10 to 30.

3. A partition coupling process for reduction recovery and separation and purification of chlorosilane according to claim 1, characterized in that: A vertical partition is arranged in the partition plate distillation tower (T2) to divide the partition plate distillation tower into a common distillation section (T2-1), a partition plate feed side (T2-2), a partition plate extraction side (T2-3) and a common stripping section (T2-4). The number of theoretical plates of the common distillation section (T2-1) of the partition distillation tower (T2) is 35 to 55, the number of theoretical plates of the partition feed side (T2-2) is 50 to 70, the number of theoretical plates of the partition extraction side (T2-3) is 50 to 70, and the number of theoretical plates of the common stripping section (T2-4) is 10 to 30.

4. A partition coupling process for reduction recovery, separation and purification of chlorosilane according to claim 1, characterized in that: The tower top gas phase outlet of the partition distillation tower (T1) is respectively connected to the shell side gas phase inlet of the condenser (E2) of the partition distillation tower (T1) and the shell side gas phase inlet of the reboiler (E3) of the partition distillation tower (T2); the shell side liquid phase outlet of the condenser (E2) of the partition distillation tower (T1) and the shell side liquid phase outlet of the reboiler (E3) of the partition distillation tower (T2) are combined and respectively connected to the tower top reflux port of the partition distillation tower (T1) and the trichlorosilane and dichlorosilane discharge pipelines (S2) for removing silicon tetrachloride. The liquid phase inlet of the reboiler (E1) of the partition distillation tower (T1) is connected to the tower kettle, the gas phase outlet of the reboiler (E1) is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the high-boiling material discharge pipeline (S4).

5. A partition coupling process for reduction recovery, separation and purification of chlorosilane according to claim 1, characterized in that: The tower top gas phase outlet of the partition plate distillation tower (T2) is connected to the shell side gas phase inlet of the condenser (E4) of the partition plate distillation tower (T2), and the shell side liquid phase outlet of the condenser (E4) of the partition plate distillation tower (T2) is respectively connected to the tower top reflux port of the partition plate distillation tower (T2) and the light impurity discharge pipeline (S5). A liquid phase side extraction port is arranged in the middle of the common distillation section (T2-1) of the partition plate distillation tower (T2) and is connected to the dichlorosilane extraction pipeline (S6). The liquid phase inlet of the reboiler (E3) of the partition plate distillation second tower (T2) is connected to the tower kettle, the gas phase outlet of the reboiler (E3) is connected to the gas phase inlet of the tower kettle, and the liquid phase outlet of the tower kettle is connected to the heavy impurity discharge pipeline (S8).

6. A partition coupling process for reduction recovery, separation and purification of chlorosilane according to claim 1, characterized in that: The top pressure of the partition plate distillation tower (T1) is 0.6-0.8 MPaG, the top temperature is 90-110° C., and the reflux ratio is 1.5:1-3:

1.

7. A partition coupling process for reduction recovery, separation and purification of chlorosilane according to claim 1, characterized in that: The top pressure of the partition plate distillation tower (T2) is 0.2-0.4 MPaG, the top temperature is 40-60°C, and the reflux ratio is 250:1-350:1.

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