Dividing wall column for recycling silicon tetrachloride and rectification method

Abstract

The invention relates to a dividing wall column for recycling silicon tetrachloride and a rectification method, in particular to the technical field of separation and purification, the dividing wall column sequentially comprises a rectification zone, a partition plate zone and a staying zone from top to bottom; the partition plate area is axially divided into a partition plate feeding area and a partition plate discharging area in the direction perpendicular to the dividing wall column; the height of the partition plate area is greater than the height of the rectification area and greater than the height of the staying area; the volume of the partition plate feeding area is 2-2.5 times that of the partition plate discharging area. According to the dividing wall column provided by the invention, the partition in the column is optimally designed, so that a good separation effect can be realized when silicon tetrachloride is separated from a polycrystalline silicon cold hydrogenation reaction product, the recovery rate of the silicon tetrachloride is greater than or equal to 99.5%, and the purity of the silicon tetrachloride product is greater than or equal to 99.99%.

Description

Technical Field

[0001] The present invention relates to the technical field of separation and purification, in particular to a bulkhead tower and a distillation method for recovering silicon tetrachloride, and in particular to a bulkhead tower and a distillation method for recovering silicon tetrachloride from a product of a cold hydrogenation reaction of polysilicon. Background Art

[0002] The production of trichlorosilane produces a large amount of silicon tetrachloride as a byproduct. Cold hydrogenation of polysilicon involves reacting silicon tetrachloride, silicon powder, and hydrogen under certain conditions to produce trichlorosilane, thereby achieving a closed-loop system for the polysilicon production line and significantly reducing production costs. The main products of the cold hydrogenation reaction include silane, unreacted silicon tetrachloride, silicon powder, boron trichloride, and high-boiling substances.

[0003] Industrially, a three-tower separation process is used to separate silane from the cold hydrogenation reaction product for purification in the distillation section. Silicon tetrachloride is returned to the cold hydrogenation reaction unit for reuse, and high-boiling products are removed from the slurry treatment unit. The cold hydrogenation reaction product enters Tower A, where silane is separated at the top. Silicon tetrachloride and high-boiling products are obtained in the kettle of Tower A and enter Tower B for separation. Silicon tetrachloride separated at the top of Tower B is returned to the cold hydrogenation reaction unit, while high-boiling products obtained in the kettle are returned to the slurry treatment unit.

[0004] For example, CN101920964A discloses a double-effect distillation method for purifying silicon tetrachloride, which comprises the following steps:

[0005] (1) The crude silicon tetrachloride obtained in the previous process first enters the spray tower, and the gas phase extracted from the cold condenser at the top of the spray tower is non-condensable gas and the liquid phase crude silicon tetrachloride obtained by condensing in the condenser is partially refluxed and partially enters the de-light tower as the discharge material; the discharge material of the spray tower kettle partially enters the spray tower kettle reboiler and partially extracted; (2) The gas phase extracted from the top of the de-light tower is used as a heat source and enters the condenser reboiler of the de-heavy tower kettle. The heat source that becomes liquid after heat exchange is refluxed as the reflux liquid at the top of the de-light tower and partially extracted; the crude silicon tetrachloride in the de-light tower kettle partially enters the de-light tower kettle reboiler and partially enters the de-heavy tower as the discharge material; (3) The gas phase extracted from the top of the de-heavy tower enters the full condenser at the top of the de-heavy tower. The liquid phase obtained by condensing in the full condenser is partially refluxed and partially discharged as the product silicon tetrachloride.

[0006] At present, with the increasing output of polysilicon, the energy consumption of the three-tower silicon tetrachloride recovery process is getting higher and higher, and the equipment investment cost is also relatively large. Therefore, improving the silicon tetrachloride recovery process, reducing energy consumption, and saving equipment investment have become urgent issues to be solved in this industry.

[0007] Based on this, the existing technology uses a single tower such as a dividing wall tower to achieve the separation of silicon tetrachloride. However, when using the dividing wall tower for purification and separation of silicon tetrachloride, the separation effect is still poor, and the purity of the obtained silicon tetrachloride product is low, which is not conducive to subsequent use. Summary of the Invention

[0008] In view of the problems existing in the prior art, the object of the present invention is to provide a dividing wall tower for recovering silicon tetrachloride to solve the defect of low purity of the silicon tetrachloride product obtained when separating silicon tetrachloride-containing materials.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a dividing wall tower for recovering silicon tetrachloride, wherein the dividing wall tower comprises, from top to bottom, a distillation zone, a baffle zone, and a retention zone;

[0011] The partition area is divided into a partition feeding area and a partition discharging area along the vertical partition wall tower axis;

[0012] The height of the partition zone is greater than the height of the rectification zone and greater than the height of the retention zone;

[0013] The volume of the partition feed zone is 2-2.5 times the volume of the partition discharge zone.

[0014] The partition wall tower provided by the present invention optimizes the design of the internal partitions of the tower, so that a good separation effect can be achieved when separating silicon tetrachloride from the polysilicon cold hydrogenation reaction product, the recovery rate of silicon tetrachloride is ≥99.5%, and the purity of the silicon tetrachloride product is ≥99.99%.

[0015] As a preferred technical solution of the present invention, the height of the partition feed zone is the same as the height of the partition discharge zone.

[0016] As a preferred technical solution of the present invention, the height of the distillation zone is 0.6-0.7 times the height of the partition zone.

[0017] Preferably, the height of the retention zone is 0.1-0.15 times the height of the partition zone.

[0018] As a preferred technical solution of the present invention, the number of plates in the distillation zone is 35-45.

[0019] Preferably, the number of plates in the partition feed zone is 60-65.

[0020] Preferably, the number of plates in the partition discharge zone is 60-65.

[0021] Preferably, the number of trays in the retention zone is 6-10.

[0022] As a preferred technical solution of the present invention, the feed port in the baffle feed zone is located at 65-68% of the height of the baffle feed zone, with the interface between the baffle zone and the retention zone as the reference.

[0023] Preferably, the discharge port in the partition discharge area is located at 32-35% of the height of the partition discharge area, with the interface between the partition area and the retention area as a reference.

[0024] As a preferred technical solution of the present invention, the spacing between the trays in the dividing wall tower is 400-600 mm.

[0025] In a second aspect, the present invention provides a distillation method for recovering silicon tetrachloride, the distillation method comprising:

[0026] The silicon tetrachloride-containing material is fed into the dividing wall tower through the feed port of the partition feed zone for separation and recovery, and the silicon tetrachloride product is obtained at the discharge port of the partition discharge zone.

[0027] As a preferred technical solution of the present invention, the feed temperature is controlled to be 80-90°C during the separation and recovery.

[0028] Preferably, the feed pressure is controlled to be 0.2-0.3 MPaG during the separation and recovery.

[0029] Preferably, the tower top pressure is controlled at 0.1-0.2 MPaG during the separation and recovery.

[0030] Preferably, the tower top temperature is controlled at 45-55°C during the separation and recovery.

[0031] As a preferred technical solution of the present invention, the bottom temperature of the tower is controlled to be 100-110°C during the separation and recovery.

[0032] Preferably, the full-tower pressure drop is controlled to be 45-55 kPa during the separation and recovery.

[0033] As a preferred technical solution of the present invention, the reflux ratio is controlled to be 4-6 during the separation and recovery.

[0034] Preferably, the reboiler load is controlled to be 12000-26000 kW during the separation and recovery.

[0035] Compared with the existing technical solutions, the present invention has the following beneficial effects:

[0036] The bulkhead tower provided by the present invention optimizes the volume proportion of each partition in the tower and the corresponding number of plates, so that effective separation can be achieved when separating the polysilicon cold hydrogenation reaction product to obtain silicon tetrachloride. At the same time, the operating flexibility of the tower is significantly improved, with an operating flexibility of 35-120%, a recovery rate of silicon tetrachloride ≥99.5%, and a purity of the silicon tetrachloride product ≥99.99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of a bulkhead tower for recovering silicon tetrachloride provided in an embodiment of the present invention.

[0038] In the figure: 100-distillation zone, 210-partition feed zone, 220-partition discharge zone, 300-retention zone;

[0039] I-polysilicon cold hydrogenation reaction product, II-silicon tetrachloride product, III-trichlorosilane, IV-non-condensable gas, V-high boiling point product.

[0040] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0041] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0042] At present, when recovering and separating silicon tetrachloride from the product of the cold hydrogenation reaction of polysilicon, although a separation process using a separate dividing wall tower is available, there are still problems in the separation of silicon tetrachloride, such as poor separation effect, low recovery rate, and low purity of the obtained silicon tetrachloride product. Based on this, the present invention optimizes the dividing wall tower to improve the separation effect of silicon tetrachloride, as follows:

[0043] 1. This embodiment provides a bulkhead tower for recovering silicon tetrachloride, such as Figure 1 As shown, the dividing wall tower includes, from top to bottom, a distillation zone 100, a partition zone and a retention zone 300;

[0044] The partition area is divided into a partition feed area 210 and a partition discharge area 220 along the vertical partition wall tower axis;

[0045] The height of the partition zone is greater than the height of the distillation zone 100 and greater than the height of the retention zone 300;

[0046] The volume of the partition feed zone 210 is 2-2.5 times the volume of the partition discharge zone 220 .

[0047] In the present invention, the volume of the partition feed zone 210 is 2-2.5 times the volume of the partition discharge zone 220, for example, it can be 2 times, 2.05 times, 2.1 times, 2.15 times, 2.2 times, 2.25 times, 2.3 times, 2.35 times, 2.4 times, 2.45 times or 2.5 times, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0048] The height of the partition feed area 210 is the same as the height of the partition discharge area 220 .

[0049] Among them, the height of the distillation zone 100 is 0.6-0.7 times the height of the partition zone, for example, it can be 0.6 times, 0.61 times, 0.62 times, 0.63 times, 0.64 times, 0.65 times, 0.66 times, 0.67 times, 0.68 times, 0.69 times or 0.7 times, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0050] Among them, the height of the staying area 300 is 0.1-0.15 times the height of the partition area, for example, it can be 0.1 times, 0.105 times, 0.11 times, 0.115 times, 0.12 times, 0.125 times, 0.13 times, 0.135 times, 0.14 times, 0.145 times or 0.15 times, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0051] The number of plates in the distillation zone 100 is 35-45, for example, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 or 45, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0052] The number of plates in the partition feed zone 210 is 60-65, for example, 60, 61, 62, 63, 64 or 65, but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0053] The number of plates in the partition discharge zone 220 is 60-65, for example, 60, 61, 62, 63, 64 or 65, but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0054] The number of trays in the retention zone 300 is 6-10, for example, 6, 7, 8, 9 or 10, but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0055] Among them, the feed port in the partition feed area 210 is located at 65-68% of the height of the partition feed area 210, based on the boundary surface between the partition area and the retention area 300. For example, it can be 65%, 65.2%, 65.4%, 65.6%, 65.8%, 66%, 66.2%, 66.4%, 66.6%, 66.8%, 67%, 67.2%, 67.4%, 67.6%, 67.8% or 68%, etc., but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0056] Among them, the discharge port in the partition discharge area 220 is located at 32-35% of the height of the partition discharge area 220, based on the boundary surface between the partition area and the retention area 300. For example, it can be 32%, 32.2%, 32.4%, 32.6%, 32.8%, 33%, 33.2%, 33.4%, 33.6%, 33.8%, 34%, 34.2%, 34.6%, 34.8% or 35%, etc., but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0057] For example, if the interface between the partition area and the retention area 300 is taken as a reference and the height of the partition area is H, then the feed port in the partition feed area 210 is located at 65-68%×H of the partition feed area 210, and the discharge port in the partition discharge area 220 is located at 32-35%×H of the partition discharge area 220.

[0058] The spacing between the trays in the next-door tower is 400-600 mm, for example, 400 mm, 420 mm, 440 mm, 460 mm, 480 mm, 500 mm, 520 mm, 540 mm, 560 mm, 580 mm or 600 mm, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0059] For example, when the polysilicon cold hydrogenation reaction product is processed, the process is as follows: the polysilicon cold hydrogenation reaction product I is fed into the next-wall tower from the partition feed area 210 for processing, silicon tetrachloride product II is produced from the partition discharge area 220, non-condensable gas IV and trichlorosilane III are produced at the top of the tower, and a high-boiling point product V is produced at the bottom of the tower.

[0060] 2. This embodiment provides a distillation method for recovering silicon tetrachloride, the distillation method comprising:

[0061] The silicon tetrachloride-containing material is fed into the dividing wall tower through the feed port of the partition feed zone for separation and recovery, and the silicon tetrachloride product is obtained at the discharge port of the partition discharge zone.

[0062] The dividing wall tower includes, from top to bottom, a distillation zone 100, a partition zone and a retention zone 300;

[0063] The partition area is divided into a partition feed area 210 and a partition discharge area 220 along the vertical partition wall tower axis.

[0064] The height of the partition zone is greater than the height of the distillation zone 100 and greater than the height of the retention zone 300.

[0065] Among them, the volume of the partition feed zone 210 is 2-2.5 times the volume of the partition discharge zone 220, for example, it can be 2 times, 2.05 times, 2.1 times, 2.15 times, 2.2 times, 2.25 times, 2.3 times, 2.35 times, 2.4 times, 2.45 times or 2.5 times, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0066] The height of the partition feed area 210 is the same as the height of the partition discharge area 220 .

[0067] Among them, the height of the distillation zone 100 is 0.6-0.7 times the height of the partition zone, for example, it can be 0.6 times, 0.61 times, 0.62 times, 0.63 times, 0.64 times, 0.65 times, 0.66 times, 0.67 times, 0.68 times, 0.69 times or 0.7 times, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0068] Among them, the height of the staying area 300 is 0.1-0.15 times the height of the partition area, for example, it can be 0.1 times, 0.105 times, 0.11 times, 0.115 times, 0.12 times, 0.125 times, 0.13 times, 0.135 times, 0.14 times, 0.145 times or 0.15 times, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0069] The number of plates in the distillation zone 100 is 35-45, for example, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 or 45, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0070] The number of plates in the partition feed zone 210 is 60-65, for example, 60, 61, 62, 63, 64 or 65, but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0071] The number of plates in the partition discharge zone 220 is 60-65, for example, 60, 61, 62, 63, 64 or 65, but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0072] The number of trays in the retention zone 300 is 6-10, for example, 6, 7, 8, 9 or 10, but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0073] Among them, the feed port in the partition feed area 210 is located at 65-68% of the height of the partition feed area 210, based on the boundary surface between the partition area and the retention area 300. For example, it can be 65%, 65.2%, 65.4%, 65.6%, 65.8%, 66%, 66.2%, 66.4%, 66.6%, 66.8%, 67%, 67.2%, 67.4%, 67.6%, 67.8% or 68%, etc., but is not limited to the listed values. Other values ​​not listed within the range also meet the requirements.

[0074] Among them, the discharge port in the partition discharge area 220 is located at 32-35% of the height of the partition discharge area 220, based on the boundary surface between the partition area and the retention area 300. For example, it can be 32%, 32.2%, 32.4%, 32.6%, 32.8%, 33%, 33.2%, 33.4%, 33.6%, 33.8%, 34%, 34.2%, 34.6%, 34.8% or 35%, etc., but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0075] For example, if the interface between the partition area and the retention area 300 is taken as a reference and the height of the partition area is H, then the feed port in the partition feed area 210 is located at 65-68%×H of the partition feed area 210, and the discharge port in the partition discharge area 220 is located at 32-35%×H of the partition discharge area 220.

[0076] The spacing between the trays in the next-door tower is 400-600 mm, for example, 400 mm, 420 mm, 440 mm, 460 mm, 480 mm, 500 mm, 520 mm, 540 mm, 560 mm, 580 mm or 600 mm, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0077] In the separation and recovery, the feed temperature is controlled to be 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, etc., but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0078] In which, the feed pressure is controlled to be 0.2-0.3 MPaG during the separation and recovery, for example, it can be 0.2 MPaG, 0.21 MPaG, 0.22 MPaG, 0.23 MPaG, 0.24 MPaG, 0.25 MPaG, 0.26 MPaG, 0.27 MPaG, 0.28 MPaG, 0.29 MPaG or 0.3 MPaG, etc., but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0079] In the separation and recovery, the top pressure of the tower is controlled to be 0.1-0.2 MPaG, for example, it can be 0.1 MPaG, 0.11 MPaG, 0.12 MPaG, 0.13 MPaG, 0.14 MPaG, 0.15 MPaG, 0.16 MPaG, 0.17 MPaG, 0.18 MPaG, 0.19 MPaG or 0.2 MPaG, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0080] In the separation and recovery, the top temperature of the tower is controlled to be 45-55°C, for example, it can be 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0081] In the separation and recovery, the bottom temperature is controlled to be 100-110°C, for example, it can be 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C or 110°C, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0082] In the separation and recovery, the full-tower pressure drop is controlled to be 45-55 kPa, for example, it can be 45 kPa, 46 kPa, 47 kPa, 48 kPa, 49 kPa, 50 kPa, 51 kPa, 52 kPa, 53 kPa, 54 kPa or 55 kPa, etc., but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0083] The reflux ratio in the separation and recovery is controlled to be 4-6, for example, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8 or 6, but is not limited to the listed values. Other values ​​not listed within this range also meet the requirements.

[0084] Wherein, the reboiler load is controlled to be 12000-26000kW in the separation and recovery, for example, it can be 12000kW, 13000kW, 14000kW, 15000kW, 16000kW, 17000kW, 18000kW, 19000kW, 20000kW, 21000kW, 22000kW, 23000kW, 24000kW, 25000kW, 25100kW, 25200kW, 25300kW, 25400kW, 25500kW, 25600kW, 25700kW, 25800kW, 25900kW or 26000kW, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0085] 3. In order to illustrate the good separation effect that can be achieved by the bulkhead tower provided by the present invention for separating silicon tetrachloride from the product of the cold hydrogenation reaction of polycrystalline silicon, the following actual example is used for illustration, as follows:

[0086] The main mass content of the polysilicon cold hydrogenation reaction product used in the following examples is as follows:

[0087] Silicon tetrachloride 71.97%, trichlorosilane 26.90%, dichlorosilane 1.04%, phosphorus trichloride 15ppm, boron trichloride 200ppb, aluminum trichloride 0.015%, hydrogen chloride 0.0046%, hydrogen 0.013%.

[0088] Example 1

[0089] This embodiment provides a process for obtaining silicon tetrachloride by separating the polysilicon cold hydrogenation reaction product using a bulkhead tower, which is as follows:

[0090] The dividing wall tower used includes, from top to bottom, a distillation zone, a partition zone and a residence zone;

[0091] The partition area is divided into a partition feeding area and a partition discharging area along the vertical partition wall tower axis;

[0092] The height of the baffle zone is greater than the height of the distillation zone and greater than the height of the retention zone; the volume of the baffle feed zone is 2.3 times the volume of the baffle discharge zone; the height of the baffle feed zone is the same as the height of the baffle discharge zone; the height of the distillation zone is 0.68 times the height of the baffle zone; and the height of the retention zone is 0.14 times the height of the baffle zone;

[0093] The number of plates in the distillation zone is 42; the number of plates in the partition feed zone is 64; the number of plates in the partition discharge zone is 64; and the number of plates in the retention zone is 7;

[0094] The feed port in the partition feed zone is located at 67% of the height of the partition feed zone, with the interface between the partition zone and the retention zone as the reference; the discharge port in the partition discharge zone is located at 33% of the height of the partition discharge zone, with the interface between the partition zone and the retention zone as the reference;

[0095] The spacing between the trays in the adjacent tower is 450 mm.

[0096] The specific process includes: feeding the polysilicon cold hydrogenation reaction product into the bulkhead tower through the feed port of the partition feed zone for separation and recovery, and obtaining the silicon tetrachloride product at the discharge port of the partition discharge zone;

[0097] During separation and recovery, the feed temperature is controlled at 85°C, the feed pressure is 0.25MPaG, the top pressure is 0.18MPaG, the top temperature is 50°C, the bottom temperature is 100°C, the full tower pressure drop is 50kPa, the reflux ratio is 5, and the reboiler load is 25125kW.

[0098] Example 2

[0099] This embodiment provides a process for obtaining silicon tetrachloride by separating the polysilicon cold hydrogenation reaction product using a bulkhead tower, which is as follows:

[0100] The dividing wall tower used includes, from top to bottom, a distillation zone, a partition zone and a residence zone;

[0101] The partition area is divided into a partition feeding area and a partition discharging area along the vertical partition wall tower axis;

[0102] The height of the baffle zone is greater than the height of the distillation zone and greater than the height of the retention zone; the volume of the baffle feed zone is 2.2 times the volume of the baffle discharge zone; the height of the baffle feed zone is the same as the height of the baffle discharge zone; the height of the distillation zone is 0.65 times the height of the baffle zone; and the height of the retention zone is 0.12 times the height of the baffle zone;

[0103] The number of plates in the distillation zone is 40; the number of plates in the partition feed zone is 62; the number of plates in the partition discharge zone is 62; and the number of plates in the retention zone is 8;

[0104] The feed port in the partition feed zone is located at 66% of the height of the partition feed zone, with the interface between the partition zone and the retention zone as the reference; the discharge port in the partition discharge zone is located at 34% of the height of the partition discharge zone, with the interface between the partition zone and the retention zone as the reference;

[0105] The spacing between the trays in the adjacent tower is 500 mm.

[0106] The specific process includes: feeding the polysilicon cold hydrogenation reaction product into the bulkhead tower through the feed port of the partition feed zone for separation and recovery, and obtaining the silicon tetrachloride product at the discharge port of the partition discharge zone;

[0107] During separation and recovery, the feed temperature is controlled at 85°C, the feed pressure is 0.28MPaG, the top pressure is 0.15MPaG, the top temperature is 48°C, the bottom temperature is 105°C, the full tower pressure drop is 48kPa, the reflux ratio is 5.5, and the reboiler load is 25640kW.

[0108] Example 3

[0109] This embodiment provides a process for obtaining silicon tetrachloride by separating the polysilicon cold hydrogenation reaction product using a bulkhead tower, which is as follows:

[0110] The dividing wall tower used includes, from top to bottom, a distillation zone, a partition zone and a residence zone;

[0111] The partition area is divided into a partition feeding area and a partition discharging area along the vertical partition wall tower axis;

[0112] The height of the baffle zone is greater than the height of the distillation zone and greater than the height of the retention zone; the volume of the baffle feed zone is 2.5 times the volume of the baffle discharge zone; the height of the baffle feed zone is the same as the height of the baffle discharge zone; the height of the distillation zone is 0.7 times the height of the baffle zone; and the height of the retention zone is 0.15 times the height of the baffle zone;

[0113] The number of plates in the distillation zone is 45; the number of plates in the partition feed zone is 65; the number of plates in the partition discharge zone is 65; and the number of plates in the retention zone is 10.

[0114] The feed port in the partition feed zone is located at 68% of the height of the partition feed zone, with the interface between the partition zone and the retention zone as the reference; the discharge port in the partition discharge zone is located at 35% of the height of the partition discharge zone, with the interface between the partition zone and the retention zone as the reference;

[0115] The spacing between the trays in the adjacent tower is 600 mm.

[0116] The specific process includes: feeding the polysilicon cold hydrogenation reaction product into the bulkhead tower through the feed port of the partition feed zone for separation and recovery, and obtaining the silicon tetrachloride product at the discharge port of the partition discharge zone;

[0117] During separation and recovery, the feed temperature is controlled at 90°C, the feed pressure is 0.2MPaG, the top pressure is 0.2MPaG, the top temperature is 55°C, the bottom temperature is 110°C, the full tower pressure drop is 45kPa, the reflux ratio is 6, and the reboiler load is 25836kW.

[0118] Example 4

[0119] This embodiment provides a process for obtaining silicon tetrachloride by separating the polysilicon cold hydrogenation reaction product using a bulkhead tower, which is as follows:

[0120] The dividing wall tower used includes, from top to bottom, a distillation zone, a partition zone and a residence zone;

[0121] The partition area is divided into a partition feeding area and a partition discharging area along the vertical partition wall tower axis;

[0122] The height of the partition zone is greater than the height of the distillation zone and greater than the height of the retention zone; the volume of the partition feed zone is twice the volume of the partition discharge zone; the height of the partition feed zone is the same as the height of the partition discharge zone; the height of the distillation zone is 0.6 times the height of the partition zone; and the height of the retention zone is 0.1 times the height of the partition zone;

[0123] The number of plates in the distillation zone is 35; the number of plates in the partition feed zone is 60; the number of plates in the partition discharge zone is 60; and the number of plates in the retention zone is 6;

[0124] The feed port in the partition feed zone is located at 65% of the height of the partition feed zone, with the interface between the partition zone and the retention zone as the reference; the discharge port in the partition discharge zone is located at 32% of the height of the partition discharge zone, with the interface between the partition zone and the retention zone as the reference;

[0125] The spacing between the trays in the adjacent tower is 400 mm.

[0126] The specific process includes: feeding the polysilicon cold hydrogenation reaction product into the bulkhead tower through the feed port of the partition feed zone for separation and recovery, and obtaining the silicon tetrachloride product at the discharge port of the partition discharge zone;

[0127] During separation and recovery, the feed temperature is controlled at 80°C, the feed pressure is 0.3MPaG, the top pressure is 0.1MPaG, the top temperature is 45°C, the bottom temperature is 100°C, the full tower pressure drop is 55kPa, the reflux ratio is 4, and the reboiler load is 12341kW.

[0128] Comparative Example 1

[0129] The only difference from Example 1 is that the volume of the partition feed zone is 0.5 times the volume of the partition discharge zone.

[0130] Comparative Example 2

[0131] The only difference from Example 1 is that the height of the rectification zone is adjusted to be the same as that of the partition plate zone.

[0132] Comparative Example 3

[0133] The only difference from Example 1 is that the height of the stay area is adjusted to be the same as that of the partition area.

[0134] Comparative Example 4

[0135] The only difference from Example 1 is that the height of the residence zone is adjusted to be the same as that of the rectification zone.

[0136] Example 5

[0137] The only difference from Example 1 is that the height of the rectification zone is 0.5 times the height of the partition zone.

[0138] Example 6

[0139] The only difference from Example 1 is that the height of the rectification zone is 0.8 times the height of the partition zone.

[0140] Example 7

[0141] The only difference from Example 1 is that the height of the retention zone is 0.08 times the height of the partition zone.

[0142] Example 8

[0143] The only difference from Example 1 is that the height of the retention zone is 0.18 times the height of the partition zone.

[0144] Example 9

[0145] The only difference from Example 1 is that the feed port in the separator feed zone is located at 50% of the height of the separator feed zone.

[0146] Example 10

[0147] The only difference from Example 1 is that the feed port in the separator feed zone is located at 70% of the height of the separator feed zone.

[0148] Example 11

[0149] The only difference from Example 1 is that the discharge port in the separator discharge area is located at 20% of the height of the separator discharge area.

[0150] Example 12

[0151] The only difference from Example 1 is that the discharge port in the separator discharge area is located at 38% of the height of the separator discharge area.

[0152] Example 13

[0153] The only difference from Example 1 is that the reflux ratio is controlled to 3 during separation and recovery.

[0154] Example 14

[0155] The only difference from Example 1 is that the reflux ratio is controlled to 7 during separation and recovery.

[0156] The recovery rate and purity index of silicon tetrachloride obtained in the above examples and comparative examples are shown in Table 1.

[0157] Table 1

[0158]

[0159]

[0160] As can be seen from Table 1, the dividing wall tower provided by the present invention achieves a good separation effect when separating silicon tetrachloride from the polysilicon cold hydrogenation reaction product by optimizing the design of the internal partitions of the tower. The recovery rate of silicon tetrachloride is ≥99.5%, and the purity of the silicon tetrachloride product is ≥99.99%.

[0161] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0162] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0163] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A bulkhead tower for recovery of silicon tetrachloride, characterized in that, The dividing wall tower comprises, from top to bottom, a rectification zone, a partition zone and a retention zone; The partition area is divided into a partition feeding area and a partition discharging area along the vertical partition wall tower axis; The height of the partition zone is greater than the height of the rectification zone and greater than the height of the retention zone; The volume of the partition feed zone is 2-2.5 times the volume of the partition discharge zone.

2. The dividing wall tower according to claim 1, wherein The height of the separator feed zone is the same as the height of the separator discharge zone.

3. The dividing wall tower according to claim 1 or 2, wherein The height of the distillation zone is 0.6-0.7 times the height of the baffle zone; Preferably, the height of the retention zone is 0.1-0.15 times the height of the partition zone.

4. The dividing wall tower according to any one of claims 1 to 3, wherein The number of plates in the distillation zone is 35-45; Preferably, the number of plates in the partition feed zone is 60-65; Preferably, the number of plates in the partition discharge zone is 60-65; Preferably, the number of trays in the retention zone is 6-10.

5. The dividing wall tower according to any one of claims 1 to 4, wherein The feed port in the partition feed zone is located at 65-68% of the height of the partition feed zone, with the interface between the partition zone and the retention zone as the reference; Preferably, the discharge port in the partition discharge zone is located at 32-35% of the height of the partition discharge zone, with the interface between the partition zone and the retention zone as a reference.

6. The dividing wall tower according to any one of claims 1 to 5, wherein The spacing between the trays in the next-wall tower is 400-600 mm.

7. A distillation method for recovering silicon tetrachloride, characterized in that: The distillation method comprises: The silicon tetrachloride-containing material is fed into the dividing wall tower through the feed port of the partition feed zone for separation and recovery, and the silicon tetrachloride product is obtained at the discharge port of the partition discharge zone.

8. The distillation method according to claim 7, wherein The feed temperature is controlled to be 80-90°C during the separation and recovery; Preferably, the feed pressure is controlled to be 0.2-0.3 MPaG during the separation and recovery; Preferably, the pressure at the top of the tower is controlled to be 0.1-0.2 MPaG during the separation and recovery; Preferably, the tower top temperature is controlled at 45-55°C during the separation and recovery.

9. The distillation method according to claim 7 or 8, characterized in that: During the separation and recovery, the bottom temperature of the tower is controlled to be 100-110°C; Preferably, the full-tower pressure drop is controlled to be 45-55 kPa during the separation and recovery.

10. The distillation method according to any one of claims 7 to 9, characterized in that: The reflux ratio in the separation and recovery is 4-6; Preferably, the reboiler load is controlled to be 12000-26000 kW during the separation and recovery.

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