Chlorosilane separation system for polysilicon production

Abstract

The utility model relates to the polycrystal silicon technical field especially is concerned on a kind of chlorosilane separation system for polycrystal silicon production, it mainly includes: washing tower, first-stage tail gas condenser, intermediate heat exchanger, second-stage tail gas condenser, condensate tank, condensate pump, slag slurry buffer tank and product collection tank and so on several parts;First, chlorosilane gas is cooled down initially by washing tower, wherein liquefied chlorosilane is transported to the slag slurry buffer tank and is temporarily stored, and then unliquefied gas is sequentially through first-stage tail gas condenser, intermediate heat exchanger and second-stage tail gas condenser and is carried out multistage depth cooling. The chlorosilane liquid obtained by each stage condensation is effectively collected to condensate tank, to realize the efficient separation and resource recovery of chlorosilane. In addition, low-temperature nitrogen gas from the outlet of second-stage tail gas condenser is used as refrigerant for intermediate heat exchanger, to realize the reuse of nitrogen gas, effectively avoid the cold energy waste and potential environmental pollution risk caused by nitrogen gas directly discharged into atmosphere.

Description

Technical Field

[0001] This utility model relates to the field of polysilicon technology, and in particular to a chlorosilane separation system for polysilicon production. Background Technology

[0002] The production of polysilicon generates a large amount of byproduct exhaust gas. This exhaust gas is rich in chlorosilanes and nitrogen. The main components of the chlorosilanes are trichlorosilane (boiling point 31.8°C), silicon tetrachloride (boiling point 57.6°C), and dichlorosilane (boiling point 8.2°C). Nitrogen has a boiling point of -196°C.

[0003] Chlorosilanes are key precursor materials in the semiconductor industry, used to manufacture high-purity silicon crystals, and are widely used in semiconductors, photovoltaic solar energy and other fields.

[0004] Currently, the most common method used in the industry to treat these chlorosilane-containing gases is alkaline scrubbing. This involves passing the exhaust gas into a scrubbing tower, where it undergoes a neutralization reaction with an alkaline solution (such as NaOH solution). The resulting solid silicates and other substances are discharged with the wastewater for further treatment; the remaining exhaust gas is then directly released into the atmosphere.

[0005] However, while this traditional treatment method is convenient and quick, it also has many drawbacks: it not only consumes a large amount of water resources, but also fails to achieve complete separation of chlorosilanes due to incomplete reactions, resulting in a waste of chlorosilane resources. At the same time, this method also imposes a heavy environmental burden—wastewater treatment is difficult, and if exhaust emissions do not meet standards, there is a risk of air pollution. Utility Model Content

[0006] The purpose of this invention is to provide a chlorosilane separation system for polysilicon production, in order to solve the problems mentioned in the background art.

[0007] The technical solution adopted in this utility model is:

[0008] A chlorosilane separation system for polysilicon production includes:

[0009] The scrubbing tower is connected to the exhaust gas equipment and is equipped with a slurry buffer tank.

[0010] A primary exhaust gas condenser is connected to the scrubbing tower;

[0011] An intermediate heat exchanger is connected to the primary exhaust gas condenser.

[0012] A secondary exhaust gas condenser is connected to the intermediate heat exchanger;

[0013] The condensate tank is connected to the first-stage tail gas condenser, the intermediate heat exchanger, and the second-stage tail gas condenser, respectively.

[0014] in,

[0015] The washing tower, the first-stage tail gas condenser, the intermediate heat exchanger and the second-stage tail gas condenser are used to achieve multi-stage liquefaction and separation of chlorosilanes.

[0016] The slurry buffer tank and condensate tank are used to collect the chlorosilane after liquefaction and separation.

[0017] Optionally, the scrubbing tower includes:

[0018] The main body of the tower is equipped with an air inlet pipe, an exhaust pipe, a high-pressure return pipe, and a slag discharge pipe.

[0019] The tower tray is disposed within the tower body;

[0020] The intake pipe is connected to the exhaust gas equipment, the exhaust pipe is connected to the first-stage exhaust gas condenser, the high-pressure return pipe is connected to the condensate tank, and the slag discharge pipe is connected to the slurry buffer tank.

[0021] Optionally, the air inlet pipe is located at one end inside the tower body, forming an air inlet elbow pipe extending towards the bottom of the tower body, and the end of the air inlet elbow pipe is provided with an annular distributor.

[0022] Optionally, a flow-through plate is also provided inside the tower body, and the flow-through plate is located below the tower tray.

[0023] Optionally, the trays are distributed in a layered structure, and each tray includes:

[0024] The main body of the tower tray has multiple through holes;

[0025] A weir plate is located at the edge of the main body of the tower tray, and multiple slots are opened through it.

[0026] Optionally, the tray may further include a downcomer plate disposed at the bottom of the weir plate.

[0027] Optionally, a PTFE membrane is provided on the through hole.

[0028] Optionally, a groove is formed on the main body of the tray.

[0029] Optionally, the refrigerant in the scrubbing tower is a chlorosilane liquid.

[0030] Optionally, the refrigerant of the intermediate heat exchanger is low-temperature nitrogen from the outlet of the secondary exhaust gas condenser.

[0031] Compared with the prior art, the beneficial effects of this utility model are:

[0032] First, the chlorosilane gas is initially cooled in a scrubbing tower. The liquefied chlorosilane is then temporarily stored in a slurry buffer tank. The unliquefied gas is then subjected to multi-stage deep cooling via a primary tail gas condenser, an intermediate heat exchanger, and a secondary tail gas condenser. The chlorosilane liquid obtained from each stage of condensation is effectively collected in a condensate tank, thus achieving efficient separation and resource recovery of chlorosilane.

[0033] In addition, the low-temperature nitrogen gas exiting the secondary exhaust gas condenser is used as a refrigerant in the intermediate heat exchanger, realizing the reuse of nitrogen gas and effectively avoiding the waste of cooling energy and potential environmental pollution risks caused by direct discharge of nitrogen gas into the atmosphere. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the overall structure of this application;

[0036] Figure 2 This is a schematic diagram of the structure of the scrubbing tower in one state as described in this application;

[0037] Figure 3 This is a structural schematic diagram of the scrubbing tower in another state in this application;

[0038] Figure 4 This is a top view of the tower structure in this application;

[0039] Figure 5 This is a schematic diagram of the side structure of the tower tray in this application.

[0040] Figure label:

[0041] 1. Scrubber; 11. Tower body; 12. Cavity; 13. Air inlet pipe; 14. Circular distributor; 15. High-pressure reflux pipe; 16. Exhaust pipe; 17. Slag discharge pipe;

[0042] 18. Tray; 181. Tray body; 1811. Through hole; 1812. Straight edge; 1813. Arc edge; 1814. Groove; 182. Weir plate; 183. Downcomer plate;

[0043] 19. Crossflow plate;

[0044] 2. Primary tail gas condenser; 3. Intermediate heat exchanger; 4. Secondary tail gas condenser; 5. Condensate tank; 6. Condensate pump; 7. Slurry buffer tank; 8. Product collection tank; 9. High-pressure liquid delivery pipe. Detailed Implementation

[0045] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this invention. Therefore, the drawings and description are considered exemplary in nature and not restrictive.

[0046] Currently, traditional treatment methods not only consume large amounts of water resources but also fail to achieve complete separation of chlorosilanes due to incomplete reactions, resulting in a waste of chlorosilane resources. Furthermore, this method imposes a heavy environmental burden—wastewater treatment is difficult, and if exhaust emissions do not meet standards, air pollution problems arise.

[0047] like Figures 1-5 As shown in the figure, this utility model embodiment provides a chlorosilane separation system for polysilicon production, which mainly includes: a washing tower 1, a primary tail gas condenser 2, an intermediate heat exchanger 3, a secondary tail gas condenser 4, a condensate tank 5, a condensate pump 6, a slurry buffer tank 7, and a product collection tank 8.

[0048] The scrubbing tower 1 is connected to the exhaust gas equipment (not shown in the figure). The exhaust gas generated by the exhaust gas equipment is transported to the scrubbing tower 1. The scrubbing tower 1 is configured to perform preliminary cooling of the exhaust gas, in which the chlorosilane gas in the exhaust gas is liquefied.

[0049] The first-stage tail gas condenser 2 is connected to the scrubbing tower 1. The tail gas flowing out of the scrubbing tower 1 is transported to the first-stage tail gas condenser 2. The first-stage tail gas condenser 2 is configured to perform a second cooling of the unliquefied chlorosilane gas in the scrubbing tower 1.

[0050] Intermediate heat exchanger 3 is connected to primary tail gas condenser 2. The tail gas flowing out of primary tail gas condenser 2 is transported to intermediate heat exchanger 3. Intermediate heat exchanger 3 is configured to perform a third cooling of the unliquefied chlorosilane gas in primary tail gas condenser 2.

[0051] The secondary tail gas condenser 4 is connected to the intermediate heat exchanger 3. The tail gas flowing out of the intermediate heat exchanger 3 is transported to the secondary tail gas condenser 4. The secondary tail gas condenser 4 is configured to perform a fourth cooling of the unliquefied chlorosilane gas in the intermediate heat exchanger 3.

[0052] The condensate tank 5 is connected to the first-stage tail gas condenser 2, the intermediate heat exchanger 3, and the second-stage tail gas condenser 4 respectively. After being cooled by the first-stage tail gas condenser 2, the intermediate heat exchanger 3, and the second-stage tail gas condenser 4, the liquefied chlorosilane liquid is transported to the condensate tank 5 under the action of gravity.

[0053] The input end of the condensate pump 6 is connected to the condensate tank 5, and its output end is equipped with a high-pressure liquid delivery pipe 9. The output port of the high-pressure liquid delivery pipe 9 has two ports: one port is connected to the scrubbing tower 1, and the other port is connected to the product collection tank 8. The chlorosilane liquid in the condensate tank 5 is transported by the condensate pump 6, one path of which is sent to the scrubbing tower 1 as a coolant to cool the exhaust gas in the tower; the other path is sent to the product collection tank 8 for centralized storage.

[0054] The slurry buffer tank 7 is connected to the washing tower 1 and is configured to collect the liquefied chlorosilane liquid and other substances generated in the washing tower 1.

[0055] Specifically, such as Figure 2 or Figure 3 As shown, the washing tower 1 mainly includes: a tower body 11 and a tower tray 18 disposed within the tower body 11.

[0056] The main body of the tower 11 is roughly cylindrical in structure, with a cavity 12 inside.

[0057] An air inlet pipe 13 is provided at the lower end of one side wall of the tower body 11. One end of the air inlet pipe 13 extends into the interior of the tower body 11, forming an air inlet elbow pipe extending towards the bottom of the tower. An annular distributor 14 is provided at the end of the air inlet elbow pipe. The annular distributor 14 is configured to distribute the exhaust gas in the air inlet elbow pipe evenly inside the tower body 11. The other end of the air inlet pipe 13 extends to the outside of the tower body 11 and connects to the exhaust gas equipment.

[0058] A reflux port is provided at the upper end of one side wall of the tower body 11. One end of the high-pressure reflux pipe 15 passes through the reflux port and is located inside the tower body 11, extending from one side of the tower body 11 to the other side adjacent to the tower body 11. Multiple nozzles (not shown in the figure) are provided on the end of the high-pressure reflux pipe 15 located inside the tower body 11; the other end of the high-pressure reflux pipe 15 is located outside the tower body 11 and is connected to the high-pressure liquid delivery pipe 9. A valve is provided on the high-pressure reflux pipe 15 located outside the tower body 11.

[0059] The top wall of the tower body 11 is provided with an exhaust pipe 16. Similarly, one end of the exhaust pipe 16 is located inside the tower body 11, and the other end is located outside the tower body 11 and connected to the first-stage tail gas condenser 2. The bottom wall of the tower body 11 is provided with a slag discharge pipe 17, which is connected to the slurry buffer tank 7. A control valve (not shown in the figure) is also provided on the slag discharge pipe 17.

[0060] The tray 18 is located above the intake pipe 13 and below the high-pressure return pipe 15, and is distributed in a layered structure, with no contact between the layers of the tray 18.

[0061] like Figure 4 and Figure 5 As shown, each tray 18 mainly includes several parts such as the tray body 181, the weir plate 182, and the downcomer plate 183.

[0062] The main body of the tower tray 181 is configured as the main location for heat exchange.

[0063] Specifically, such as Figure 4 As shown, the main body of the tray 181 is roughly plate-shaped, with multiple through holes 1811 through which exhaust gas can pass, but liquid refrigerant cannot pass.

[0064] More specifically, in this embodiment, in order to enable the through hole 1811 to allow exhaust gas to pass through while preventing liquid from passing through, a PTFE membrane is provided on the through hole 1811. The PTFE membrane enables the through hole 1811 to allow exhaust gas to pass through while preventing liquid from passing through.

[0065] The edge of the tray body 181 is mainly composed of a pair of straight edges 1812 and a pair of curved edges 1813. The two curved edges 1813 match the shape of the inner wall of the tray body 11 and are fixed to a horizontal position inside the tray body 11 by welding. A weir plate 182 is installed on each of the two straight edges 1812. The weir plate 182 is arranged at a certain angle, and its end near the tray body 181 has multiple slots (not shown in the figure) for liquid refrigerant to flow out. The weir plate 182 is used to guide the directional flow of liquid. Figure 5 As shown, the bottom of the weir plate 182 is connected to a downwardly extending downcomer plate 183, and the liquid refrigerant flowing through the slot flows to the next tray 18 through the downcomer plate 183.

[0066] Furthermore, such as Figure 4 As shown, a groove 1814 is provided in the middle of the tray body 181 along the straight edge 1812, and the groove 1814 is used to store liquid refrigerant. This structure can increase the liquid film thickness on the tray body 181, prolong the liquid residence time, and promote a more uniform distribution of liquid across the entire surface of the tray body 181.

[0067] Furthermore, such as Figure 2 or Figure 3 As shown, in order to separate particulate matter from the exhaust gas and prevent particulate matter from clogging the through holes 1811 on the main body of the tray 181, a flow-through plate 19 is provided below the tray 18.

[0068] In use, first, replenish the chlorosilane liquid to the condensate tank 5, then start the condensate pump 6. Driven by the condensate pump 6, the chlorosilane liquid in the condensate tank 5 enters the high-pressure return pipe 15. For example... Figure 3 As shown, the chlorosilane liquid in the high-pressure reflux pipe 15 is evenly sprayed onto the tray body 181 of the top tray 18 through the nozzle, and used as a coolant to cool the exhaust gas.

[0069] As the liquid level on the main body of the tray 181 gradually rises, the chlorosilane liquid overflows to the inlet and flows downwards layer by layer through the downcomer 183. The liquid eventually reaches the flow-through plate 19, washes away the particles attached to the flow-through plate 19, and then collects at the bottom of the tower. It is then discharged into the slurry buffer tank 7 through the slag discharge pipe 17 for further processing.

[0070] At the same time, such as Figure 2 As shown, the exhaust gas enters through the inlet pipe 13, is evenly distributed by the annular distributor 14, and then flows upward. The exhaust gas passes sequentially through the flow-through plate 19 and the through holes 1811 on each tray body 181, and comes into countercurrent contact with the chlorosilane liquid on the tray body 181 for heat exchange. During this process, some of the chlorosilane gas is condensed and liquefied, and flows into the bottom of the tower along with the chlorosilane liquid, where it is temporarily stored in the slurry buffer tank 7.

[0071] The unliquefied gas continues to rise and enters the first-stage tail gas condenser 2, intermediate heat exchanger 3, and second-stage tail gas condenser 4 sequentially through exhaust pipe 16 for multi-stage cooling. The chlorosilane liquid condensed from each stage is effectively collected into the condensate tank 5.

[0072] After continuous cooling by the above system, the chlorosilanes in the exhaust gas have been completely liquefied and recovered. Nitrogen, due to its extremely low boiling point (-196°C) and the fact that the refrigerant operating temperature cannot reach this condition, remains in a gaseous state. However, after cooling, the nitrogen's temperature meets the refrigeration requirements, so it is used as a refrigerant in the intermediate heat exchanger 3 to cool the exhaust gas, thus achieving nitrogen reuse. Finally, the reused nitrogen is discharged from the refrigerant outlet of the intermediate heat exchanger 3 for further processing.

[0073] Part of the chlorosilane liquid in the condensate tank 5 is sent back to the washing tower 1 by the condensate pump 6 for recycling as a coolant, while the other part is sent to the product collection tank 8 for centralized collection.

[0074] Furthermore, in this embodiment, the refrigerant temperature used in the scrubbing tower 1, the first-stage tail gas condenser 2, the intermediate heat exchanger 3, and the second-stage tail gas condenser 4 generally exhibits a step-down trend.

[0075] In a preferred embodiment, the refrigerant of the scrubbing tower 1 is a recycled chlorosilane liquid; the refrigerant of the first-stage tail gas condenser 2 is 7°C water; the refrigerant of the intermediate heat exchanger 3 is low-temperature nitrogen from the outlet of the second-stage tail gas condenser 4, which has been continuously cooled in the scrubbing tower 1, the first-stage tail gas condenser 2 and the second-stage tail gas condenser 4, and its temperature meets the requirements of the refrigerant; the refrigerant of the second-stage tail gas condenser 4 is -40°C Freon.

[0076] It should be noted that:

[0077] I. The structures of the first-stage tail gas condenser 2, intermediate heat exchanger 3 and second-stage tail gas condenser 4 in this embodiment are all existing technologies, so they will not be described in detail in this embodiment.

[0078] Second, in this embodiment, when the system is first run, there is no refrigerant in the intermediate heat exchanger 3. At this time, the exhaust gas from the first-stage exhaust gas condenser 2 will pass directly through the intermediate heat exchanger 3 without heat exchange, and then enter the second-stage exhaust gas condenser 4 for cooling.

[0079] After being cooled by the secondary tail gas condenser 4, the chlorosilanes in the tail gas have been fully liquefied and separated, and the remaining main component is low-temperature nitrogen. This portion of low-temperature nitrogen is then introduced into the intermediate heat exchanger 3 as a refrigerant to cool the tail gas entering the system from the outlet of the primary tail gas condenser 2, thereby establishing a normal operating cycle.

[0080] Since the system's cooling capacity has not been fully established during initial operation (intermediate heat exchanger 3 is not yet in operation), it is necessary to control the flow rate of the exhaust gas introduced into the scrubbing tower 1 to ensure that the chlorosilane gas in it can be fully liquefied.

[0081] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A chlorosilane separation system for polysilicon production, characterized by, include: The scrubbing tower is connected to the exhaust gas equipment and is equipped with a slurry buffer tank. A primary exhaust gas condenser is connected to the scrubbing tower; An intermediate heat exchanger is connected to the primary exhaust gas condenser. A secondary tail gas condenser is connected to the intermediate heat exchanger; a condensate tank is connected to the primary tail gas condenser, the intermediate heat exchanger, and the secondary tail gas condenser, respectively; wherein, the scrubbing tower, the primary tail gas condenser, the intermediate heat exchanger, and the secondary tail gas condenser are used to achieve multi-stage liquefaction and separation of chlorosilanes; the slurry buffer tank and the condensate tank are used to collect the liquefied and separated chlorosilanes.

2. The chlorosilane separation system for polysilicon production according to claim 1, wherein The scrubbing tower includes: a tower body on which an air inlet pipe, an exhaust pipe, a high-pressure reflux pipe and a slag discharge pipe are provided; and a tower tray disposed within the tower body; wherein, the air inlet pipe is connected to the tail gas equipment, the exhaust pipe is connected to the first-stage tail gas condenser, the high-pressure reflux pipe is connected to the condensate tank, and the slag discharge pipe is connected to the slurry buffer tank.

3. The chlorosilane separation system for polysilicon production according to claim 2, wherein The air intake pipe is located at one end inside the tower body, forming an air intake elbow extending towards the bottom of the tower body, and the end of the air intake elbow is provided with an annular distributor.

4. The chlorosilane separation system for polysilicon production according to claim 2, wherein The tower body is also equipped with a flow-through plate, which is located below the tower tray.

5. The chlorosilane separation system for polysilicon production according to claim 2, wherein The trays are distributed in a layered structure, and each tray includes: a tray body with multiple through holes; and a weir plate disposed at the edge of the tray body with multiple slots through it.

6. The chlorosilane separation system for polysilicon production according to claim 5, wherein The tray also includes a downcomer, which is disposed at the bottom of the weir plate.

7. The chlorosilane separation system for polysilicon production according to claim 5, wherein A PTFE membrane is provided on the through hole.

8. The chlorosilane separation system for polysilicon production according to claim 5, wherein A groove is formed on the main body of the tower tray.

9. The chlorosilane separation system for polysilicon production according to claim 1, wherein The refrigerant in the washing tower is a chlorosilane liquid.

10. The chlorosilane separation system for polysilicon production according to claim 1, wherein The refrigerant in the intermediate heat exchanger is low-temperature nitrogen gas from the outlet of the secondary tail gas condenser.

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