1. A method for purifying and separating silicon tetrachloride in polysilicon synthesis comprises the following steps:

s1, separating the chlorosilane mixture containing silicon tetrachloride in a first separation tower to obtain crude silicon tetrachloride;

and S2, separating and purifying the crude silicon tetrachloride in a second separation tower, extracting the purified silicon tetrachloride from a side extraction outlet of a tower kettle of the second separation tower, recycling, and discharging impurities from an outlet at the bottom of the tower kettle of the second separation tower.

2. The method for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to claim 1, further comprising the following steps: s3, further separating and purifying the overhead product of the second separation tower in a third separation tower.

3. A method for purifying and separating silicon tetrachloride in polysilicon synthesis as claimed in claim 2, wherein the operating pressure of the third separation tower is 0.3-0.5MPa, the temperature at the top of the tower is 60-65 ℃, and the temperature at the bottom of the tower is 85-90 ℃.

4. The method for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to claim 2, wherein the step S3 further comprises: and (4) adsorbing the tower kettle extract of the third separation tower and recycling.

5. A method for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to claim 4, wherein the adsorption treatment adopts activated carbon as an adsorbent.

6. A method for purifying and separating silicon tetrachloride in polysilicon synthesis as claimed in any one of claims 1 to 5, wherein the operating pressure of the first separation tower is 0.4 to 0.45MPa, the tower top temperature is 88 to 92 ℃, and the tower bottom temperature is 118-122 ℃.

7. A method for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to any one of claims 1 to 5, wherein the components of the crude silicon tetrachloride comprise: trichlorosilane is more than or equal to 3 percent, and silicon tetrachloride is less than or equal to 97 percent.

8. A method for purifying and separating silicon tetrachloride in polysilicon synthesis as claimed in any one of claims 1 to 5, wherein the operating pressure of the second separation tower is 0.2 to 0.4MPa, the tower top temperature is 88 to 92 ℃, and the tower bottom temperature is 115-120 ℃.

9. A silicon tetrachloride purification and separation device in polysilicon synthesis is characterized by comprising:

the first separation tower is used for separating crude silicon tetrachloride from the introduced chlorosilane mixture containing silicon tetrachloride;

and the second separation tower is connected with the first separation tower and is used for separating and purifying crude silicon tetrachloride, and a tower kettle of the second separation tower is provided with a side extraction port so as to extract purified silicon tetrachloride.

10. The device for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to claim 9, further comprising:

and the third separation tower is connected with the second separation tower and is used for further separating and purifying the tower top produced substance of the second separation tower.

11. The device for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to claim 10, further comprising:

and the absorber is connected with the third separation tower and is used for absorbing and removing impurities from the tower kettle produced material of the third separation tower.

12. A device for purifying and separating silicon tetrachloride in the synthesis of polysilicon according to claim 11, wherein the adsorber adopts an activated carbon adsorption column.

Background

In the polysilicon synthesis process, externally purchased silicon powder, silicon tetrachloride and hydrogen are generally adopted to synthesize trichlorosilane under the action of a catalyst, and the synthesized trichlorosilane is separated by a rough separation tower, wherein: the trichlorosilane obtained at the tower top is purified and separated from impurities in a three-stage light and two-stage heavy removal and reactive distillation mode, and the components with high impurity concentration are treated in different adsorption processes and then introduced into the next procedure for circulation; and returning the silicon tetrachloride obtained from the tower bottom to the system to be continuously used as a raw material for recycling.

At present, a rough separation tower in a polycrystalline silicon synthesis process is not provided with an impurity and high-boiling-point substance discharge port, so that impurities and high polymers cannot be discharged, impurities of a chlorosilane mixture are brought to the tower top and tower kettle materials along with light weight components, so that the impurity content in silicon tetrachloride in the tower kettle is enriched, and impurities and high polymers are extracted from the bottom of the rough separation tower along with the silicon tetrachloride, namely, in the process, the trichlorosilane obtained after synthesis can only realize the separation effect of trichlorosilane and the chlorosilane mixture containing silicon tetrachloride through the rough separation tower, but boron, phosphorus compounds, metal impurities and the like contained in the chlorosilane mixture containing silicon tetrachloride cannot be removed to obtain high-purity silicon tetrachloride. The impurities and the high polymer contained in the polycrystalline silicon are continuously returned to the system together with the circulating silicon tetrachloride for direct use, so that the impurities and the high polymer are continuously enriched in the polycrystalline silicon synthesis system, and the quality of the polycrystalline silicon is influenced.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art, and provides a method and a device for purifying and separating silicon tetrachloride in polysilicon synthesis, which can reduce or remove impurities and high polymers in the silicon tetrachloride and solve the problem that the quality of polysilicon is influenced by the enrichment of the impurities and the high polymers caused by the circulation of the silicon tetrachloride.

The invention discloses a method for purifying and separating silicon tetrachloride in polysilicon synthesis, which is used for solving the technical problems and adopts the following technical scheme:

a method for purifying and separating silicon tetrachloride in polysilicon synthesis, which comprises the following steps,

s1, separating the chlorosilane mixture containing silicon tetrachloride in a first separation tower to obtain crude silicon tetrachloride;

and S2, separating and purifying the crude silicon tetrachloride in a second separation tower, extracting the purified silicon tetrachloride from a side extraction outlet of a tower kettle of the second separation tower, recycling, and discharging impurities from an outlet at the bottom of the tower kettle of the second separation tower.

Preferably, the method further comprises the following steps: s3, further separating and purifying the overhead product of the second separation tower in a third separation tower.

Preferably, the operating pressure of the third separation tower is 0.3-0.5MPa, the tower top temperature is 60-65 ℃, and the tower kettle temperature is 85-90 ℃.

Preferably, the step S3 further includes: and (4) adsorbing the tower kettle extract of the third separation tower and recycling.

Preferably, the adsorption treatment uses activated carbon as an adsorbent.

Preferably, the operating pressure of the first separation tower is 0.4-0.45MPa, the tower top temperature is 88-92 ℃, and the tower kettle temperature is 118-122 ℃.

Preferably, the crude silicon tetrachloride comprises the following components: trichlorosilane is more than or equal to 3 percent, and silicon tetrachloride is less than or equal to 97 percent.

Preferably, the operating pressure of the second separation tower is 0.2-0.4MPa, the tower top temperature is 88-92 ℃, and the tower kettle temperature is 115-120 ℃.

The invention aims to solve the technical problems and adopts a device for purifying and separating silicon tetrachloride in polysilicon synthesis, which has the technical scheme that:

a silicon tetrachloride purification and separation device in polysilicon synthesis is characterized by comprising:

the first separation tower is used for separating crude silicon tetrachloride from the introduced chlorosilane mixture containing silicon tetrachloride;

and the second separation tower is connected with the first separation tower and is used for separating and purifying crude silicon tetrachloride, and a tower kettle of the second separation tower is provided with a side extraction port so as to extract purified silicon tetrachloride. Specifically, the feed inlet of the second separation tower is connected with the discharge outlet of the tower kettle of the first separation tower.

Preferably, the method further comprises the following steps:

the third separation tower is connected with the second separation tower and is used for further separating and purifying the tower top produced substance of the second separation tower;

preferably, the method further comprises the following steps:

and the absorber is connected with the third separation tower and is used for absorbing and removing impurities from the tower kettle produced material of the third separation tower.

Preferably, the adsorber adopts an activated carbon adsorption column.

According to the method and the device for purifying and separating the silicon tetrachloride in the polysilicon synthesis, disclosed by the invention, the silicon tetrachloride for circulation is further separated and purified, boron and phosphorus compounds and metal impurities are discharged from the bottom of the tower kettle, and the purified silicon tetrachloride is recovered and utilized from the lateral line to form an impurity-removing open circulation, so that the content of the boron and phosphorus compounds and the metal impurities in the circulating silicon tetrachloride introduced into a cold hydrogenation process can be greatly reduced, and the quality of a polysilicon product is favorably improved. Meanwhile, the light component trichlorosilane discharged from the tower top is recovered after being subjected to separation, purification, adsorption and other treatments, the quality of trichlorosilane can be improved, the utilization rate of trichlorosilane can be improved (trichlorosilane which enters a cold hydrogenation process along with silicon tetrachloride to be circulated is further separated and directly used for a downstream process of trichlorosilane), the running cost of the downstream process in a polycrystalline silicon synthesis process is effectively reduced, an activated carbon adsorption column is used on a residual adsorption process of a tower kettle, and the cost of adsorption equipment and adsorbent which are invested and used is greatly reduced compared with that of the traditional tower entering process, so that the production cost is reduced.

Drawings

Fig. 1 is a schematic structural diagram of a silicon tetrachloride purification and separation device in polysilicon synthesis in an embodiment of the invention.

In the figure: 1-a feed line; 2-a first separation column; 3-the top outlet of the first separation column; 4-a tower kettle outlet of the first separation tower; 5-a second separation column; 6-the top outlet of the second separation column; 7-side extraction outlet; 8-a tower bottom outlet of the second separation tower; 9-a third separation column; 10-the top outlet of the third separation column; 11-a tower kettle outlet of the third separation tower;

12-an adsorber; 13-a first pump; 14-a second pump; 15-a third pump; 16-valve.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention will be further clearly and completely described below with reference to the accompanying drawings and specific examples of the present invention.

In the prior art, the polysilicon synthesis process only simply separates trichlorosilane from silicon tetrachloride, impurities such as boron and phosphorus compounds contained in the silicon tetrachloride cannot be removed, and the problem that the quality of polysilicon is affected by continuous enrichment of impurities exists when the silicon tetrachloride containing the impurities is recycled. Therefore, the invention provides a method for purifying and separating silicon tetrachloride in polysilicon synthesis, which comprises the following steps:

s1, separating the chlorosilane mixture containing silicon tetrachloride in a first separation tower to obtain crude silicon tetrachloride;

and S2, separating and purifying the crude silicon tetrachloride in a second separation tower, recycling the purified silicon tetrachloride extracted from the tower kettle side of the second separation tower, and discharging impurities from the outlet at the bottom of the tower kettle of the second separation tower.

Correspondingly, the invention also provides a device for purifying and separating silicon tetrachloride in polysilicon synthesis, which comprises:

the first separation tower is used for separating crude silicon tetrachloride from the introduced chlorosilane mixture containing silicon tetrachloride;

and the second separation tower is connected with the first separation tower and is used for separating and purifying crude silicon tetrachloride, and a tower kettle of the second separation tower is provided with a side extraction port so as to extract purified silicon tetrachloride.

Example 1

The embodiment discloses a method for purifying and separating silicon tetrachloride in polysilicon synthesis, which comprises the following steps:

s1, separating the chlorosilane mixture containing silicon tetrachloride in a first separation tower 2 to obtain crude silicon tetrachloride;

wherein the operating pressure of the first separation tower 2 is 0.4-0.45MPa, the tower top temperature is 88-92 ℃, and the tower kettle temperature is 118-122 ℃. Crude silicon tetrachloride is extracted from a tower kettle of the first separation tower 2, and the components of the crude silicon tetrachloride mainly comprise a large amount of silicon tetrachloride, a small amount of trichlorosilane, boron-containing compounds, phosphorus compounds, metal impurities and the like. The tower top produced substance of the first separation tower 2 is mainly trichlorosilane.

In practical operation, a small amount of trichlorosilane (for example, trichlorosilane is more than or equal to 3%, and silicon tetrachloride is less than or equal to 97%) is retained in crude silicon tetrachloride of a tower bottom produced substance of the first separation tower 2 by adjusting the pressure and temperature of the first separation tower 2, that is, the pressure and temperature conditions in the first separation tower 2 are controlled not to be enough to evaporate all trichlorosilane from the tower top, so that the trichlorosilane evaporated from the tower top is reduced or prevented from carrying other substances (for example, dichlorosilane, boron-containing compounds and phosphorus-containing compounds with similar boiling points to trichlorosilane) and being discharged together, and the purity of trichlorosilane in the tower top produced substance of the first separation tower 2 is improved.

S2, crude silicon tetrachloride is separated and purified in the second separation tower 5, the purified silicon tetrachloride extracted from the tower bottom side of the second separation tower 5 is recycled, impurities are discharged from the bottom of the tower bottom of the second separation tower 5, and light components such as trichlorosilane, B, P-containing metal impurities (such as B, P-containing compounds with a boiling point close to that of trichlorosilane and metal impurities) are discharged from the tower top outlet 6 of the second separation tower. The principle is mainly as follows: the temperature in the second separation tower is controlled by utilizing the different boiling points of the components in the crude silicon tetrachloride, for example, the tower top temperature is 88-92 ℃, the tower bottom temperature is 115-120 ℃, the operation pressure is preferably 0.2-0.4MPa, so that the silicon tetrachloride and heavy components containing B, P and metal impurities (such as B, P-containing compound and metal impurities with the boiling point close to that of the silicon tetrachloride) are accumulated in the tower bottom section, and the heavier the boiling point is, the heavy components are accumulated towards the bottom of the tower bottom. The silicon tetrachloride is gathered on the upper layer of the tower kettle by controlling the temperature of the tower kettle, and then is extracted from a side extraction outlet of the tower kettle, so that the purification is realized.

S3, the top product of the second separation tower 5 is further separated and purified in a third separation tower 9.

Wherein the operating pressure of the third separation tower 9 is 0.3-0.5MPa, the tower top temperature is 60-65 ℃, and the tower kettle temperature is 85-90 ℃ so as to ensure the purity of trichlorosilane in the tower top produced substance of the third separation tower 9.

Further, step S3 further includes: and (4) adsorbing the tower kettle extract of the third separation tower 9 and recycling the adsorbed product.

Wherein, the adsorption treatment preferably adopts active carbon as an adsorbent. Of course, the adsorbent can also be any other adsorbent capable of adsorbing impurities such as boron and phosphorus compounds, such as molecular sieve, silica gel, resin, and the like, and is not limited to activated carbon.

As shown in fig. 1, this embodiment also discloses a device for the method for purifying and separating silicon tetrachloride in the synthesis of polysilicon, which includes:

and the first separation tower 2 is used for separating crude silicon tetrachloride from the introduced chlorosilane mixture. In this embodiment, a feeding port of the first separation tower 2 is preferably used for being connected with a crude separation pipeline output by a cold hydrogenation process in a polysilicon production process, a tower kettle outlet 4 of the first separation tower is used for extracting crude silicon tetrachloride, a tower top outlet 3 of the first separation tower is used for extracting purified trichlorosilane, and the purified trichlorosilane is introduced into a raw material workshop crude distillation system for use. The first separation column 2 is preferably a rectifying column.

And the second separation tower 5 is connected with the first separation tower 2 and used for separating and purifying crude silicon tetrachloride, and a tower kettle of the second separation tower 5 is provided with a side extraction outlet 7 so as to extract purified silicon tetrachloride. Specifically, the inlet of the second separation column 5 is preferably provided at the middle part of the second separation column 5 and connected to the tank outlet 4 of the first separation column. The second separation tower 5 preferably adopts a rectifying tower, the side extraction outlet 7 is arranged at the middle lower part of the rectifying tower, for example, when the number of the fillers in the rectifying tower is five, the side extraction outlet 7 can be arranged at the position of the second section of fillers from bottom to top so as to obtain purified silicon tetrachloride with higher purity. The side extraction outlet 7 is used for connecting a cold hydrogenation process, and the side extraction outlet 7 is connected with a first pump 13 and used for outputting purified silicon tetrachloride to realize the cyclic utilization of the silicon tetrachloride. The bottom outlet 8 of the second separation tower is used for connecting a slurry treatment process, such as a hydrolysis treatment device, and a second pump 14 is preferably arranged between the bottom outlet and the hydrolysis treatment device so as to discharge impurities outwards. This embodiment is through retrieving silicon tetrachloride purification cyclic utilization, arranges impurity outward for through the impurity greatly reduced that the silicon tetrachloride of circulation introduces.

In actual operation, considering the condition that the treatment capacity of the slag slurry treatment process is limited, a valve 16 can be arranged between the bottom outlet 8 of the tower kettle of the second separation tower and the side outlet 7 of the tower kettle of the second separation tower, so that when the treatment capacity of the slag slurry treatment process is excessive, the tower kettle produced matter is temporarily sent to the cold hydrogenation process, and impurities are gradually discharged in the subsequent silicon tetrachloride circulation process.

The apparatus of this embodiment, further comprising:

the third separation tower 9 is connected with the second separation tower 5 and is used for further separating and purifying the tower top produced substance of the second separation tower 5;

and the absorber 12 is connected with the third separation tower 9 and is used for absorbing and removing impurities from tower kettle produced materials of the third separation tower 9.

Specifically, a feeding port of the third separation tower 9 is connected with an outlet 6 at the top of the second separation tower, the top of the second separation tower 5 is mainly trichlorosilane, and the third separation tower 9 is used for purifying trichlorosilane. And an outlet 10 at the top of the third separation tower is used for extracting purified trichlorosilane, and the purified trichlorosilane is introduced into a raw material workshop rough distillation system for use. The tower bottom extracted substance of the third separation tower 9 is mainly trichlorosilane and boron and phosphorus compounds and other impurities with the boiling point similar to that of the trichlorosilane. The inlet of the adsorber 12 is connected with the tower bottom outlet 11 of the third separation tower, a third pump 15 is preferably arranged between the inlet and the tower bottom outlet, the adsorber 12 preferably adopts an activated carbon adsorption column so as to adsorb impurities containing boron, phosphorus compounds and the like in the tower bottom produced material of the third separation tower 9, and the trichlorosilane after adsorption treatment is introduced into a downstream process of trichlorosilane, such as an organosilicon device for use. The third separation column 9 is preferably a rectifying column.

According to the method and the device for purifying and separating silicon tetrachloride in the polysilicon synthesis, silicon tetrachloride for circulation is further separated and purified, boron and phosphorus compounds and metal impurities are discharged from the bottom of the tower kettle, and the purified silicon tetrachloride is recovered and utilized from the lateral line to form an impurity-removing open circulation, so that the content of the boron and phosphorus compounds and the metal impurities in the circulating silicon tetrachloride introduced into a cold hydrogenation process can be greatly reduced, and the quality of a polysilicon product is improved. Meanwhile, the light component trichlorosilane discharged from the tower top is recovered after being subjected to separation, purification, adsorption and other treatments, the quality of trichlorosilane can be improved, the utilization rate of trichlorosilane can be improved (trichlorosilane which enters a cold hydrogenation process along with silicon tetrachloride to be circulated is further separated and directly used for a downstream process of trichlorosilane), the running cost of the downstream process in a polycrystalline silicon synthesis process is effectively reduced, an activated carbon adsorption column is used on a residual adsorption process of a tower kettle, and the cost of adsorption equipment and adsorbent which are invested and used is greatly reduced compared with that of the traditional tower entering process, so that the production cost is reduced.

Example 2

The embodiment discloses a method for purifying and separating silicon tetrachloride in polycrystalline silicon synthesis by using the device in embodiment 1, which specifically comprises the following steps:

s1, introducing a crude material (containing dichlorosilane 0.5%, trichlorosilane 15-20%, silicon tetrachloride 75-80%) from a cold hydrogenation process into a first separation tower 2 at a speed of 140-: extracting light component trichlorosilane (more than or equal to 98 percent) from the top of the tower and introducing the light component trichlorosilane into a raw material workshop rough distillation system in the polycrystalline silicon synthesis process for use; heavy components (namely crude silicon tetrachloride, the content of silicon trichloride is more than or equal to 3 percent) are extracted from the tower bottom and are introduced into a second separation tower 5. In the embodiment, the operating pressure and temperature conditions of the first separation tower 2 are controlled to enable the crude silicon tetrachloride component to contain more than or equal to 3% (such as 3.1%) of trichlorosilane, so that the impurity content in the tower top produced material of the first separation tower 2 can be effectively controlled, and the purity of the purified trichlorosilane is improved.

S2, controlling the pressure of the second separation tower 5 to be 0.3MPa, the temperature of the top of the tower to be 90 ℃ and the temperature of the bottom of the tower to be 115 ℃, separating and purifying the crude silicon tetrachloride to enrich heavy components such as silicon tetrachloride in the crude silicon tetrachloride, and continuously extracting the crude silicon tetrachloride from the side extraction port 7 of the bottom of the second separation tower 5, namely purified silicon tetrachloride (through detection, the content of impurities in the crude silicon tetrachloride extracted from the side extraction port 7 is obviously reduced compared with the content of impurities in the crude silicon tetrachloride extracted from the bottom extraction port of the bottom of the tower), and conveying the purified silicon tetrachloride to a cold hydrogenation chemical process for recycling through an output pump. And (3) delivering a material (namely silicon tetrachloride containing high-concentration impurities) extracted from the bottom of the tower kettle of the second separation tower 5 to a slag slurry treatment process at the speed of 0.2t/h through a delivery pump for hydrolysis treatment. When the treatment capacity of the slurry treatment process is limited, the valve 16 can be opened on the premise of not influencing the quality of the tower top extract of the second separation tower 5, and the tower bottom outlet extract of the second separation tower 5 is sent to the cold hydrogenation process. The overhead output of the second separation column is passed to a third separation column 9.

S3, the tower top product of the second separation tower 5 mainly contains trichlorosilane and impurities such as boron and phosphorus compounds with the boiling point similar to that of trichlorosilane. Controlling the pressure of the third separation tower 9 to be 0.4MPa, the temperature of the tower top to be 60 ℃ and the temperature of the tower kettle to be 85 ℃, and purifying trichlorosilane extracted from the tower top of the second separation tower 5, wherein: extracting the purified trichlorosilane from the top of the third separation tower 9, and introducing the trichlorosilane into a raw material workshop rough distillation system in the polycrystalline silicon synthesis process for use; and extracting the trichlorosilane containing impurities from a tower kettle outlet 11 of the third separation tower, conveying the trichlorosilane into an activated carbon adsorption column adsorber through a third pump 15 for adsorption treatment to remove impurities containing boron, phosphorus compounds and the like, and introducing the trichlorosilane subjected to adsorption treatment into a downstream process for use.

Example 3

The embodiment discloses a method for purifying and separating silicon tetrachloride in polycrystalline silicon synthesis by using the device in the embodiment 1, which specifically comprises the following steps:

s1, introducing the crude material (containing dichlorosilane 0.5%, trichlorosilane 15-20%, silicon tetrachloride 75-80%) from the cold hydrogenation process into a first separation tower at the speed of 140-: extracting light component trichlorosilane (more than or equal to 98 percent) from the top of the tower and introducing the light component trichlorosilane into a raw material workshop rough distillation system in the polycrystalline silicon synthesis process for use; heavy components (namely crude silicon tetrachloride, the content of silicon trichloride is more than or equal to 3 percent) are extracted from the tower bottom and are introduced into a second separation tower 5. In the embodiment, the operating pressure and temperature conditions of the first separation tower 2 are controlled to enable the crude silicon tetrachloride component to contain more than or equal to 3% of trichlorosilane, so that the impurity content in the tower top produced material of the first separation tower 2 can be effectively controlled, and the purity of the purified trichlorosilane is improved.

S2, controlling the pressure of the second separation tower 5 to be 0.2MPa, the temperature of the top of the tower to be 88 ℃ and the temperature of the bottom of the tower to be 120 ℃, separating and purifying the crude silicon tetrachloride to enrich heavy components such as silicon tetrachloride in the crude silicon tetrachloride in the tower, continuously extracting the components in the tower from a side extraction port 7 of the tower of the second separation tower, namely purified silicon tetrachloride (through detection, the content of impurities in the components in the tower extracted from the side extraction port 7 is obviously reduced compared with the content of impurities in the components in the tower extracted from the bottom of the tower), and conveying the purified silicon tetrachloride to a cold hydrogen chemical process for recycling through an output pump 13. And (3) delivering a material (namely silicon tetrachloride containing high-concentration impurities) extracted from the bottom of the tower kettle of the second separation tower 5 to a slag slurry treatment process at the speed of 0.2t/h through a delivery pump 14 for hydrolysis treatment. When the treatment capacity of the slurry treatment process is limited, the valve 16 can be opened on the premise of not influencing the quality of the tower top extract of the second separation tower 5, and the tower bottom outlet extract of the second separation tower 5 is sent to the cold hydrogenation process. The overhead output of the second separation column 5 is sent to a third separation column 9.

S3, the tower top product of the second separation tower 5 mainly contains trichlorosilane and impurities such as boron and phosphorus compounds with the boiling point similar to that of trichlorosilane. Controlling the pressure of the third separation tower 9 to be 0.3MPa, the temperature of the tower top to be 65 ℃ and the temperature of the tower kettle to be 90 ℃, and purifying trichlorosilane extracted from the tower top of the second separation tower 5, wherein: extracting the purified trichlorosilane from the top of the third separation tower, and introducing the trichlorosilane into a raw material workshop rough distillation system in the polycrystalline silicon synthesis process for use; and (3) extracting the trichlorosilane containing impurities from a tower kettle outlet 11 of the third separation tower, conveying the trichlorosilane to an activated carbon adsorption column adsorber through a conveying pump for adsorption treatment to remove impurities containing boron, phosphorus compounds and the like, and introducing the trichlorosilane subjected to adsorption treatment into a downstream process for use.

Example 4

The embodiment discloses a method for purifying and separating silicon tetrachloride in polycrystalline silicon synthesis by using the device in the embodiment 1, which specifically comprises the following steps:

s1, introducing the crude material (dichlorosilane: 0.5%, trichlorosilane: 15-20%, silicon tetrachloride: 75-80%) from the cold hydrogenation process into the first separation tower 2 through the feeding pipeline 1 at the speed of 140-: extracting light component trichlorosilane (more than or equal to 98 percent) from the top of the tower and introducing the light component trichlorosilane into a raw material workshop rough distillation system in the polycrystalline silicon synthesis process for use; heavy components (namely crude silicon tetrachloride, the content of silicon trichloride is more than or equal to 3 percent) are extracted from the tower bottom and are introduced into a second separation tower 5. In the embodiment, the operating pressure and temperature conditions of the first separation tower 2 are controlled to enable the crude silicon tetrachloride component to contain more than or equal to 3% of trichlorosilane, so that the impurity content in the tower top produced material of the first separation tower 2 can be effectively controlled, and the purity of the purified trichlorosilane is improved.

S2, controlling the pressure of the second separation tower 5 to be 0.4MPa, the temperature of the top of the tower to be 92 ℃ and the temperature of the bottom of the tower to be 120 ℃, separating and purifying crude silicon tetrachloride to enrich heavy components such as silicon tetrachloride in the tower kettle, continuously extracting the tower kettle components from a side extraction outlet 7 of the tower kettle of the second separation tower, namely purified silicon tetrachloride (through detection, the impurity content in the tower kettle components extracted from the side extraction outlet is obviously reduced compared with the impurity content in the tower kettle components extracted from the bottom of the tower kettle), and conveying the purified silicon tetrachloride to a cold hydrogenation chemical process for recycling through an output pump. And (3) delivering a material (namely silicon tetrachloride containing high-concentration impurities) extracted from the bottom of the tower kettle of the second separation tower 5 to a slag slurry treatment process at the speed of 0.2t/h through a delivery pump for hydrolysis treatment. When the treatment capacity of the slurry treatment process is limited, the valve can be opened on the premise of not influencing the quality of the produced material at the top of the second separation tower 5, and the produced material at the bottom of the tower kettle of the second separation tower 5 is sent to the cold hydrogenation process. The overhead output of the second separation column 5 is sent to a third separation column 9.

S3, the tower top product of the second separation tower mainly contains trichlorosilane and boron and phosphorus compounds and other impurities with the boiling point similar to that of trichlorosilane. Controlling the pressure of the third separation tower 9 to be 0.5MPa, the temperature of the tower top to be 63 ℃ and the temperature of the tower kettle to be 88 ℃, and purifying trichlorosilane extracted from the tower top outlet 6 of the second separation tower, wherein: extracting the purified trichlorosilane from an outlet 10 at the top of the third separation tower, and introducing the trichlorosilane into a raw material workshop rough distillation system in the polycrystalline silicon synthesis process for use; and (3) extracting the trichlorosilane containing impurities from a tower kettle outlet 11 of the third separation tower, conveying the trichlorosilane to an activated carbon adsorption column adsorber through a conveying pump for adsorption treatment to remove impurities containing boron, phosphorus compounds and the like, and introducing the trichlorosilane subjected to adsorption treatment into a downstream process for use.

It will be understood that the foregoing is only a preferred embodiment of the invention, and that the invention is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention, and these changes and modifications are to be considered as within the scope of the invention.