Rectification system for removing impurities in grading manner

Abstract

The utility model discloses a rectification system for removing impurities in a grading manner, which belongs to the technical field of polycrystalline silicon production, and is characterized in that impurities extracted from all towers in a hydrogenation liquid / synthetic liquid rectification process sequentially pass through a first rectification tower, a second rectification tower, a third rectification tower, a fourth rectification tower, a fifth rectification tower and a trichlorosilane extraction pipe to obtain a trichlorosilane product; the first tower kettle extraction pipe is connected with a silicon tetrachloride extraction main pipe through a first adsorption tower, and the side extraction pipe is connected with the silicon tetrachloride extraction main pipe; and a silicon tetrachloride product is obtained from the silicon tetrachloride extraction header pipe. According to the utility model, high-impurity chlorosilane extracted from each tower in a hydrogenation liquid / synthetic liquid rectification process can be effectively recovered.

Description

Technical Field

[0001] The utility model belongs to the technical field of polysilicon production, and in particular relates to a rectification system for removing impurities in stages. Background Art

[0002] During the production of high-purity silicon, varying levels of impurities such as carbon, metals, boron, and phosphorus in the raw materials significantly impact production and quality. Consequently, high-purity silicon companies are seeking new technologies to remove some of these impurities through pre-treatment and post-processing, thereby improving and stabilizing raw material quality and ensuring the quality of their high-purity silicon products.

[0003] Polysilicon synthesis liquid: comes from the trichlorosilane synthesis unit, and is produced from raw materials provided by the trichlorosilane synthesis process, with trichlorosilane and silicon tetrachloride as the main components, as well as a small amount of dichlorosilane. If high-impurity silicon powder is used, the average boron content in the synthesis liquid is about 5000-10000ppbw. The ultra-high B is introduced into the original synthesis distillation treatment. Due to the limited purification capacity, the high boron content in the refined trichlorosilane liquid is affected, which ultimately affects the quality of high-purity silicon products.

[0004] Hydrogenated liquid: Hydrogenated liquid (synthetic distillation raw material) comes from the cold hydrogenation device. It contains many impurities and is usually directly fed into the synthetic distillation tower at this stage, resulting in a large feed load and impurity removal load for the synthetic distillation tower, which is not conducive to subsequent capacity planning.

[0005] At present, synthetic liquid and hydrogenated liquid are usually directly fed into the raw material distillation system. The B / P impurity content is too high and the content of various material components is different, resulting in poor component stability in the raw material, directly increasing the workload of the raw material distillation to remove boron / phosphorus and the difficulty of stable distillation control; resulting in an increase in the boron / phosphorus content in the subsequent distillation tower, there is a risk of exceeding the boron / phosphorus content in the refined trichlorosilane; at the same time, cryogenic liquid and synthetic liquid are directly fed into the original distillation system, and the raw material distillation tower is used for separation and purification, which increases the workload of the raw material distillation tower and is not conducive to subsequent capacity expansion plans. Utility Model Content

[0006] To address the above technical problems, the present invention provides a distillation system for graded impurity removal. Impurities extracted from each tower in the hydrogenated liquid / synthetic liquid distillation process are sequentially passed through the first, second, third, fourth, and fifth distillation towers, with trichlorosilane product obtained from the trichlorosilane extraction pipe. The first tower reactor extraction pipe is connected to the silicon tetrachloride extraction main pipe via the first adsorption tower, and the side extraction pipe is connected to the silicon tetrachloride extraction main pipe; the silicon tetrachloride product is obtained from the silicon tetrachloride extraction main pipe. The present invention effectively recovers high-impurity chlorosilanes extracted from each tower in the hydrogenated liquid / synthetic liquid distillation process.

[0007] The purpose of this utility model is achieved through the following technical solutions:

[0008] A distillation system for removing impurities in stages comprises a first distillation tower, a second distillation tower, a third distillation tower, a fourth distillation tower and a fifth distillation tower, wherein the first distillation tower is provided with a feed pipe, a side extraction pipe, a first tower bottom extraction pipe and a first tower top extraction pipe, the first tower bottom extraction pipe being connected to a silicon tetrachloride extraction main pipe via a first adsorption tower, and the side extraction pipe being connected to the silicon tetrachloride extraction main pipe; the first tower top extraction pipe is connected to the second distillation tower, the second distillation tower is provided with a second tower bottom extraction pipe and a second tower top extraction pipe, the second tower bottom extraction pipe is connected to the third distillation tower, the third distillation tower is provided with a third tower bottom extraction pipe and a third tower top extraction pipe, the third tower top extraction pipe is connected to the fourth distillation tower, the fourth distillation tower is provided with a fourth tower bottom extraction pipe and a fourth tower top extraction pipe, the fourth tower bottom extraction pipe is connected to the fifth distillation tower, and the fifth distillation tower is provided with a fifth tower bottom extraction pipe and a trichlorosilane extraction pipe.

[0009] Preferably, a second adsorption tower and an anti-disproportionation tower are sequentially arranged on the second tower top extraction pipe, and the anti-disproportionation tower is connected to the first connecting pipe.

[0010] Preferably, the third tower bottom extraction pipe is connected to the fifth tower bottom extraction pipe and then connected to the sixth distillation tower.

[0011] Preferably, the sixth distillation tower is provided with a sixth tower bottom extraction pipe and a sixth tower top extraction pipe, the sixth tower top extraction pipe is connected to the second tower bottom extraction pipe, and the sixth tower bottom extraction pipe is connected to the second connecting pipe through the third adsorption tower.

[0012] Preferably, the first connecting pipe is connected to the fourth tower top extraction pipe and then connected to the seventh distillation tower.

[0013] Preferably, the seventh distillation tower is provided with a seventh bottom extraction pipe and a seventh top extraction pipe, and the seventh top extraction pipe is connected to the fourth adsorption tower.

[0014] Preferably, the fourth adsorption tower is provided with a first discharge pipe and a second discharge pipe, and the second discharge pipe is connected to the second connecting pipe and then connected to the feed pipe.

[0015] Preferably, the first discharge pipe is connected to the second distillation tower.

[0016] Preferably, a silicon tetrachloride inlet pipe is provided on the deproportionation tower.

[0017] The beneficial effects of this technical solution are as follows:

[0018] 1. The present invention provides a distillation system for removing impurities in stages. Impurities extracted from each tower in the hydrogenation liquid / synthesis liquid distillation process enter the first distillation tower through the feed pipe. Cleaner STC flows out of the side extraction pipe and is used as a raw material for cold hydrogenation (discharged through the silicon tetrachloride extraction main pipe). The first tower bottom extraction pipe extracts STC containing more impurities. Subsequently, the impurities are adsorbed by an adsorbent in the first adsorption tower and used as a raw material for cold hydrogenation (discharged through the silicon tetrachloride extraction main pipe). The TCS / DCS extracted from the first tower top extraction pipe enters the second distillation tower. A certain amount of TCS and impurities are removed from the tower, and the output from the second tower bottom output pipe enters the third distillation tower; the third distillation tower separates the heavier impurities in TCS (in the intermediate transition zone between TCS and STC), and the output from the third tower top output pipe enters the fourth distillation tower; the fourth distillation tower removes impurities lighter than TCS (in the intermediate transition zone between TCS and DCS), and the output from the fourth tower bottom output pipe enters the fifth distillation tower; the fifth distillation tower further processes the impurities in the intermediate transition zone between TCS and STC, and the trichlorosilane product is obtained from the trichlorosilane output pipe.

[0019] 2. The utility model provides a distillation system for graded impurity removal. The second tower top extraction pipe extracts a certain amount of TCS in excess. The impurities in the transition zone between DCS and TCS enter the second adsorption tower and are adsorbed by the adsorbent. Then, they enter the anti-disproportionation tower for anti-disproportionation reaction and are used as raw materials. This part of the raw materials is extracted together with the light components extracted from the fourth tower top extraction pipe and sent to the seventh distillation tower. The seventh distillation tower separates the light component impurities and then enters the fourth adsorption tower for adsorption removal. Subsequently, the extraction from the first discharge pipe enters the feed of the second distillation tower; the extraction from the second discharge pipe returns to the feed pipe together with the extraction from the second connecting pipe.

[0020] 3. The utility model provides a distillation system for graded removal of impurities. The output from the third tower bottom output pipe and the output from the fifth tower bottom output pipe enter the sixth distillation tower together for separation. The output from the sixth tower bottom output pipe enters the third adsorption tower for adsorption and then returns to the feed pipe. The output from the sixth tower top output pipe and the output from the second tower bottom output pipe enter the third distillation tower together for distillation and separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural diagram of the utility model;

[0022] 10. First distillation tower; 11. Feed pipe; 12. Side extraction pipe; 13. First tower bottom extraction pipe; 14. First tower top extraction pipe; 15. Silicon tetrachloride extraction main pipe; 20. Second distillation tower; 21. Second tower bottom extraction pipe; 22. Second tower top extraction pipe; 30. Third distillation tower; 31. Third tower bottom extraction pipe; 32. Third tower top extraction pipe; 40. Fourth distillation tower; 41. Fourth tower bottom extraction pipe; 42. Fourth tower top extraction pipe; 50. Fifth distillation tower; 51. Fifth tower bottom extraction pipe pipe; 52, trichlorosilane production pipe; 60, sixth distillation tower; 61, sixth tower bottom production pipe; 62, sixth tower top production pipe; 70, seventh distillation tower; 71, seventh tower bottom production pipe; 72, seventh tower top production pipe; 80, first adsorption tower; 90, second adsorption tower; 100, anti-disproportionation tower; 110, third adsorption tower; 140, fourth adsorption tower; 141, first discharge pipe; 142, second discharge pipe; 150, first connecting pipe; 160, second connecting pipe; 170, silicon tetrachloride inlet pipe. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0024] Example 1

[0025] like Figure 1 As shown, a distillation system for removing impurities in stages includes a first distillation tower 10, a second distillation tower 20, a third distillation tower 30, a fourth distillation tower 40 and a fifth distillation tower 50. The first distillation tower 10 is provided with a feed pipe 11, a side extraction pipe 12, a first tower bottom extraction pipe 13 and a first tower top extraction pipe 14. The first tower bottom extraction pipe 13 is connected to the silicon tetrachloride extraction main pipe 15 through the first adsorption tower 80, and the side extraction pipe 12 is connected to the silicon tetrachloride extraction main pipe 15; the first tower top extraction pipe 14 is connected to the second distillation tower 20, and the second distillation tower A second tower bottom extraction pipe 21 and a second tower top extraction pipe 22 are provided on 20, and the second tower bottom extraction pipe 21 is connected to the third distillation tower 30. The third distillation tower 30 is provided with a third tower bottom extraction pipe 31 and a third tower top extraction pipe 32. The third tower top extraction pipe 32 is connected to the fourth distillation tower 40. The fourth distillation tower 40 is provided with a fourth tower bottom extraction pipe 41 and a fourth tower top extraction pipe 42. The fourth tower bottom extraction pipe 41 is connected to the fifth distillation tower 50. The fifth distillation tower 50 is provided with a fifth tower bottom extraction pipe 51 and a trichlorosilane extraction pipe 52.

[0026] Example 2

[0027] The difference between this embodiment and embodiment 1 is that a second adsorption tower 90 and an anti-disproportionation tower 100 are sequentially provided on the second tower top extraction pipe 22 , and the anti-disproportionation tower 100 is connected to the first connecting pipe 150 .

[0028] The third tower bottom extraction pipe 31 is connected to the fifth tower bottom extraction pipe 51 and then connected to the sixth distillation tower 60 .

[0029] The sixth distillation tower 60 is provided with a sixth bottom extraction pipe 61 and a sixth top extraction pipe 62 . The sixth top extraction pipe 62 is connected to the second bottom extraction pipe 21 . The sixth bottom extraction pipe 61 is connected to the second connecting pipe 160 through the third adsorption tower 110 .

[0030] The first connecting pipe 150 is connected to the fourth tower top extraction pipe 42 and then connected to the seventh distillation tower 70 .

[0031] The seventh distillation tower 70 is provided with a seventh bottom extraction pipe 71 and a seventh top extraction pipe 72, and the seventh top extraction pipe 72 is connected to the fourth adsorption tower 140. The seventh bottom extraction pipe 71 separates the silicon tetrachloride after the reaction in the deproportionation tower.

[0032] The fourth adsorption tower 140 is provided with a first discharge pipe 141 and a second discharge pipe 142. The second discharge pipe 142 is connected to the second connecting pipe 160 and then connected to the feed pipe 11. The first discharge pipe 141 and the second discharge pipe 142 can be provided separately, or the first discharge pipe 141 and the second discharge pipe 142 can be provided separately.

[0033] The first discharge pipe 141 is connected to the second distillation tower 20 .

[0034] Wherein, the deproportionation tower 100 is provided with a silicon tetrachloride inlet pipe 170 .

[0035] The beneficial effects of this technical solution are as follows:

[0036] 1. The present invention provides a distillation system for removing impurities in stages. Impurities extracted from each tower in the hydrogenated liquid / synthetic liquid distillation process enter the first distillation tower 10 through the feed pipe 11. Cleaner STC flows out of the side extraction pipe 12 and is used as a raw material for cold hydrogenation (discharged through the silicon tetrachloride extraction main pipe 15). The first tower bottom extraction pipe 13 extracts STC containing more impurities. Subsequently, the impurities are adsorbed by an adsorbent in the first adsorption tower 80 and used as a raw material for cold hydrogenation (discharged through the silicon tetrachloride extraction main pipe 15). The TCS / DCS extracted from the first tower top extraction pipe 14 enters the second distillation tower 20. The second distillation tower A certain amount of TCS and impurities are removed from the second tower bottom take-off pipe 20, and the take-off from the second tower bottom take-off pipe 21 enters the third distillation tower 30; the third distillation tower separates the heavier impurities in TCS (in the intermediate transition zone between TCS and STC), and the take-off from the third tower top take-off pipe 32 enters the fourth distillation tower 40; the fourth distillation tower 40 removes impurities lighter than TCS (in the intermediate transition zone between TCS and DCS), and the take-off from the fourth tower bottom take-off pipe 41 enters the fifth distillation tower 50; the fifth distillation tower 50 further processes the impurities in the intermediate transition zone between TCS and STC, and the trichlorosilane product is obtained from the trichlorosilane take-off pipe 52.

[0037] 2. The present invention provides a distillation system for removing impurities in stages. The second tower top extraction pipe 22 extracts a certain amount of TCS in excess. The impurities in the transition zone between DCS and TCS enter the second adsorption tower 90 and are adsorbed by the adsorbent. Then, they enter the anti-disproportionation tower 100 for anti-disproportionation reaction and serve as raw materials. This part of the raw materials is extracted together with the light components extracted from the fourth tower top extraction pipe 42 and sent to the seventh distillation tower 70. The seventh distillation tower 70 separates the light component impurities and enters the fourth adsorption tower 140 for adsorption removal. Subsequently, the extraction from the first discharge pipe 141 enters the feed of the second distillation tower 20; the extraction from the second discharge pipe 142 and the extraction from the second connecting pipe 160 are returned to the feed pipe 11.

[0038] 3. The utility model provides a distillation system for graded removal of impurities. The output from the third tower bottom output pipe 31 and the output from the fifth tower bottom output pipe 51 enter the sixth distillation tower 60 together for separation. The output from the sixth tower bottom output pipe 61 enters the third adsorption tower 110 for adsorption and then returns to the feed pipe 11. The output from the sixth tower top output pipe 62 and the output from the second tower bottom output pipe 21 enter the third distillation tower 30 together for distillation and separation.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention falls within the scope of protection of the present invention.

Claims

1. A distillation system for removing impurities in a graded manner, characterized by: The invention comprises a first distillation tower (10), a second distillation tower (20), a third distillation tower (30), a fourth distillation tower (40) and a fifth distillation tower (50), wherein the first distillation tower (10) is provided with a feed pipe (11), a side extraction pipe (12), a first tower bottom extraction pipe (13) and a first tower top extraction pipe (14), wherein the first tower bottom extraction pipe (13) is connected to a silicon tetrachloride extraction main pipe (15) through a first adsorption tower (80), and the side extraction pipe (12) is connected to the silicon tetrachloride extraction main pipe (15); the first tower top extraction pipe (14) is connected to the second distillation tower (20), and the second distillation tower (20) is provided with a second A tower bottom extraction pipe (21) and a second tower top extraction pipe (22), wherein the second tower bottom extraction pipe (21) is connected to a third distillation tower (30), the third distillation tower (30) is provided with a third tower bottom extraction pipe (31) and a third tower top extraction pipe (32), the third tower top extraction pipe (32) is connected to a fourth distillation tower (40), the fourth distillation tower (40) is provided with a fourth tower bottom extraction pipe (41) and a fourth tower top extraction pipe (42), the fourth tower bottom extraction pipe (41) is connected to a fifth distillation tower (50), the fifth distillation tower (50) is provided with a fifth tower bottom extraction pipe (51) and a trichlorosilane extraction pipe (52).

2. A distillation system for graded impurity removal according to claim 1, characterized in that: A second adsorption tower (90) and an anti-disproportionation tower (100) are sequentially arranged on the second tower top extraction pipe (22), and the anti-disproportionation tower (100) is connected to the first connecting pipe (150).

3. A distillation system for removing impurities in stages according to claim 2, characterized in that: The third tower bottom extraction pipe (31) is connected to the fifth tower bottom extraction pipe (51) and then connected to the sixth distillation tower (60).

4. A distillation system for graded impurity removal according to claim 3, characterized in that: The sixth distillation tower (60) is provided with a sixth tower bottom extraction pipe (61) and a sixth tower top extraction pipe (62), the sixth tower top extraction pipe (62) is connected to the second tower bottom extraction pipe (21), and the sixth tower bottom extraction pipe (61) is connected to the second connecting pipe (160) through the third adsorption tower (110).

5. A distillation system for graded impurity removal according to claim 4, characterized in that: The first connecting pipe (150) is connected to the fourth tower top extraction pipe (42) and then connected to the seventh distillation tower (70).

6. A distillation system for graded impurity removal according to claim 5, characterized in that: The seventh distillation tower (70) is provided with a seventh tower bottom extraction pipe (71) and a seventh tower top extraction pipe (72), and the seventh tower top extraction pipe (72) is connected to the fourth adsorption tower (140).

7. A distillation system for graded impurity removal according to claim 6, characterized in that: The fourth adsorption tower (140) is provided with a first discharge pipe (141) and a second discharge pipe (142), and the second discharge pipe (142) is connected to the second connecting pipe (160) and then connected to the feed pipe (11).

8. A distillation system for graded impurity removal according to claim 7, characterized in that: The first discharge pipe (141) is connected to the second distillation tower (20).

9. A distillation system for graded impurity removal according to claim 8, characterized in that: The deproportionation tower (100) is provided with a silicon tetrachloride inlet pipe (170).

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