A vapor phase impurity removal system of a polysilicon slurry dryer

Abstract

This invention discloses a vapor phase impurity removal system for a polycrystalline silicon slurry dryer, comprising a dryer, a purification tower, and a multi-stage condensation mechanism. The dryer contains a solid material containing chlorosilanes and heats the solid material with hot water or steam to obtain vapor phase chlorosilanes. The inlet of the purification tower is connected to the top outlet of the dryer. The multi-stage condensation mechanism receives the vapor phase chlorosilanes output from the purification tower and condenses them to obtain liquid chlorosilanes. This invention, by incorporating a purification tower, removes impurities from the vapor phase chlorosilanes, thereby directly reducing the impact of impurities on subsequent equipment. Both the multi-stage condensation mechanism and the purification tower can cool and condense the vapor phase chlorosilanes, allowing the pipe length between the dryer and the purification tower to be designed to be as short as possible while still meeting requirements, thus reducing impurity deposition in the pipe due to the cooling of the vapor phase chlorosilanes.

Description

Technical Field

[0001] This utility model relates to a vapor phase impurity removal system for a polycrystalline silicon slag slurry dryer, belonging to the field of polycrystalline silicon slag slurry treatment technology. Background Technology

[0002] Please see Figure 1 The existing process flow of polycrystalline silicon slurry dryer is as follows: In dryer 1, steam enters dryer 1 through pipe 12, and the exhaust steam and a small amount of steam condensate after steam heating are discharged through pipe 13. The solid waste residue after the slurry is filtered by the drum or filter is dried in dryer 1. After being heated by steam, the chlorosilane in the solid waste residue is vaporized, and the gaseous chlorosilane formed is condensed into liquid by the gas phase condenser 8 through pipe 14.

[0003] However, because some of the metal chlorides in the solid waste are vaporized during the drying process, a small amount of vaporized metal chlorides are present in the gaseous chlorosilane. Simultaneously, some fine silica powder is carried out of the dryer 1 by the vaporized chlorosilane gas. These metal chlorides precipitate after cooling through pipe 14 and condenser 8, depositing inside pipe 14 and the gaseous condenser 8. These deposited metal chlorides and the silica powder carried by the gaseous chlorosilane mix and form scale on the inner walls of pipe 14 and the gaseous condenser 8, clogging the gaseous pipe 14 and the gaseous condenser 8. In some specific operating environments, the vapor phase outlet pipe needs to be shut down for cleaning if it operates for no more than one month and the vapor phase condenser tube bundle is blocked if it operates for no more than three months. This necessitates frequent disassembly and cleaning of the vapor phase outlet pipe and vapor phase condenser, reducing the system's operating cycle and increasing maintenance frequency and costs. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a vapor phase impurity removal system for a polycrystalline silicon slurry dryer, which aims to reduce blockage caused by impurities by removing impurities from the vapor phase chlorosilane and cooling it in multiple stages.

[0005] To achieve the above objectives, this utility model employs the following technical solution: This utility model provides a vapor phase impurity removal system for a polycrystalline silicon slag dryer, comprising: A dryer is used to contain solids containing chlorosilanes and to obtain gaseous chlorosilanes by heating the solids with steam. The purification tower has its inlet connected to the top outlet of the dryer; the purification tower is used to remove impurities from gaseous chlorosilane by spraying, to obtain purified gaseous chlorosilane and liquid containing impurities. A multi-stage condensation mechanism is provided, with its inlet connected to the top outlet of the purification tower. The multi-stage condensation mechanism is used to receive the gaseous chlorosilane output from the purification tower and condense the gaseous chlorosilane to obtain liquid chlorosilane.

[0006] Furthermore, the multi-stage condensation mechanism includes: A primary cooler, the inlet of which is connected to the top outlet of the purification tower; A secondary condenser, the inlet of which is connected to the gas outlet of the primary cooler; The primary cooler and secondary condenser are used to sequentially condense gaseous chlorosilane to obtain liquid chlorosilane.

[0007] Furthermore, it also includes condensate tanks; The bottom outlet of the purification tower, the liquid outlet of the primary cooler, and the liquid outlet of the secondary condenser are all connected to the inlet of the condensate tank; the condensate tank is used to collect the liquid in the purification tower and the liquid chlorosilane obtained by condensation from the primary cooler and the secondary condenser.

[0008] Furthermore, the gas outlet of the secondary condenser is connected to the cryogenic unit via a tail gas pipe.

[0009] Furthermore, the liquid outlet of the condensate tank is connected to one end of the first delivery pipe; The other end of the first conveying pipe is connected to the slurry tank and is used to convey a portion of the liquid in the condensate tank to the slurry tank.

[0010] Furthermore, the liquid outlet of the condensate tank is also connected to one end of a second conveying pipe, and the other end of the second conveying pipe is connected to a spray cooler; and is used to convey a portion of the liquid in the condensate tank to the spray cooler; the spray cooler is used to cool the liquid conveyed from the second conveying pipe and convey it to the purification tower as spray liquid.

[0011] Furthermore, the liquid outlet of the condensate tank is connected to the inlet of the residual liquid pump, and the outlet of the residual liquid pump is connected to one end of the first delivery pipe and one end of the second delivery pipe.

[0012] Furthermore, the inlet of the dryer is connected to an input pipe for inputting the heating medium.

[0013] Furthermore, the heating medium is hot water or superheated water, with a temperature of 90-180℃.

[0014] Furthermore, the heating medium is saturated steam or superheated steam, and the temperature of the saturated steam or superheated steam is 100-180℃. Compared with the prior art, the beneficial effects achieved by this utility model are as follows: This utility model provides a vapor phase impurity removal system for a polycrystalline silicon slurry dryer. By setting up a purification tower, the inlet of which is connected to the top outlet of the dryer, the purification tower is used to remove impurities from the vapor phase chlorosilane by spraying, thereby obtaining the purified vapor phase chlorosilane and the liquid containing impurities. The purification tower can remove impurities from the vapor phase chlorosilane, thereby directly reducing the impact of impurities on subsequent equipment.

[0015] This invention also incorporates a multi-stage condensation mechanism after the purification tower, which, along with the purification tower, can cool and condense the gaseous chlorosilanes. This allows the pipeline length between the dryer and the purification tower to be designed to be as short as possible while still meeting requirements, and also reduces the deposition of impurities in the pipeline caused by the cooling of the gaseous chlorosilanes. Therefore, this invention can significantly reduce the maintenance frequency of the dryer's vapor phase outlet pipeline. Due to the impurity removal operation of the purification tower, the multi-stage condensation mechanism does not require shutdown for maintenance and scale cleaning, resulting in higher overall operating efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the vapor phase impurity removal system in a polycrystalline silicon slag dryer in the prior art; Figure 2 This is a schematic diagram of the vapor phase impurity removal system for a polycrystalline silicon slag slurry dryer provided in this embodiment of the present invention; In the diagram: 1. Dryer; 11. First pipe; 12. Input pipe; 13. Discharge pipe; 14. Cooling pipe; 2. Purification tower; 21. Liquid delivery pipe; 22. Second pipe; 3. Condensate tank; 31. Residual liquid delivery pipe; 32. Return gas pipe; 4. Residual liquid pump; 41. First delivery pipe; 42. Second delivery pipe; 5. Spray cooler; 51. Return liquid pipe; 6. Primary cooler; 61. Third pipe; 62. Fourth pipe; 7. Secondary condenser; 71. Fifth pipe; 72. Tail gas pipe; 8. Vapor phase condenser; 81. Condenser drain pipe; 82. Condenser exhaust pipe. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0018] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. Example

[0020] Please see Figure 2 This embodiment introduces a vapor phase impurity removal system for a polycrystalline silicon slurry dryer, including a dryer 1, a purification tower 2, and a multi-stage condensation mechanism.

[0021] The solid waste residue of polycrystalline silicon slurry, after being filtered by a rotary drum or filter, is dried in dryer 1. After being heated with steam, the chlorosilanes in the solid waste residue vaporize, forming gaseous chlorosilanes. Because some of the metal chlorides contained in the solid waste residue are vaporized during the drying process, the gaseous chlorosilanes contain a small amount of vaporized metal chlorides. At the same time, some fine silicon powder is carried out of dryer 1 by the vaporized chlorosilane gas. The inlet of purification tower 2 is connected to the top outlet of dryer 1 through a first pipe 11. Purification tower 2 is used to remove impurities from the gaseous chlorosilanes by spraying, obtaining purified gaseous chlorosilanes and liquid containing impurities. Since the purification tower can cool and condense the gaseous chlorosilanes, the length of the first pipe 11 between dryer 1 and purification tower 2 can be designed to be the shortest possible while meeting the necessary requirements. This reduces the deposition of impurities caused by the cooling of gaseous chlorosilanes in the first pipe 11 due to its long pipe length. The inlet of the multi-stage condensation mechanism is connected to the top outlet of the purification tower 2; the multi-stage condensation mechanism is used to receive the gaseous chlorosilane output from the purification tower 2 and condense the gaseous chlorosilane to obtain liquid chlorosilane.

[0022] Specifically, in this embodiment, the multi-stage condensation mechanism includes a primary cooler 6 and a secondary condenser 7. The inlet of the primary cooler is connected to the top outlet of the purification tower 2 via a second pipe 22. The inlet of the secondary condenser 7 is connected to the gas outlet of the primary cooler 6 via a fourth pipe 62. The primary cooler 6 and the secondary condenser 7 are used to sequentially condense gaseous chlorosilane to obtain liquid chlorosilane.

[0023] In addition, to collect liquid chlorosilane, this embodiment includes a condensate tank 3. The bottom outlet of the purification tower 2 is connected to the inlet of the condensate tank 3 via a liquid delivery pipe 21. The liquid outlet of the primary cooler 6 is connected to the inlet of the condensate tank 3 via a second pipe 61. The liquid outlet of the secondary condenser 7 is connected to the inlet of the condensate tank 3 via a fifth pipe 71. The condensate tank 3 is used to collect the liquid in the purification tower 2 and the liquid chlorosilane obtained by condensation from the primary cooler 6 and the secondary condenser 7.

[0024] Furthermore, the liquid outlet of the condensate tank 3 is connected to one end of the first conveying pipe 41; the other end of the first conveying pipe 41 is connected to a slurry tank (not shown), and is used to convey a portion of the liquid in the condensate tank 3 to the slurry tank. The liquid outlet of the condensate tank 3 is also connected to one end of the second conveying pipe 42, and the other end of the second conveying pipe 42 is connected to the spray cooler 5; and is used to convey another portion of the liquid in the condensate tank 3 to the spray cooler 5; the spray cooler 5 is used to cool the liquid conveyed from the second conveying pipe 42 and continues to convey it to the purification tower 2 through the return pipe 51 for use as spray liquid. The liquid chlorosilane used for spraying is cooled by the spray cooler 5, and the temperature of the sprayed chlorosilane is -25-30°C. Preferably, the temperature of the sprayed chlorosilane can be -20~15°C. The gas outlet of the condensate tank 3 is connected to the fourth pipe 62 through the return gas pipe 32, thereby returning the generated gas to the secondary condenser 7 for condensation.

[0025] Please refer to [link / reference needed] for further information. Figure 2 In order to improve the output efficiency of liquid in condensate tank 3, in this embodiment, the liquid outlet of condensate tank 3 is connected to the inlet of residual liquid pump 4 through residual liquid conveying pipe 31, and the outlet of residual liquid pump 4 is connected to one end of the first conveying pipe 41 and one end of the second conveying pipe 42.

[0026] It should be noted that the drying temperature of the dryer is 90-180℃, and the inlet of the dryer 1 is connected to an inlet pipe 12 for inputting the heating medium. In this embodiment, the heating medium input through the inlet pipe 12 is steam, which is either saturated steam or superheated steam, and the temperature of the saturated steam or superheated steam is 100-180℃. The bottom outlet of the dryer 1 is connected to a outlet pipe 13 for outputting the exhaust steam and steam condensate generated after the steam has been heated inside the dryer 1.

[0027] In other embodiments, steam can be replaced with hot water, specifically hot water at a temperature of 90-100°C or superheated water at a temperature of 100-160°C. After being heated within the dryer 1, the hot water can be discharged through the discharge pipe 13.

[0028] Preferably, superheated water at 130℃-155℃ is used as cooling water for cooling to higher temperatures after heating the dryer 1, or as supplementary water for the flash tank where superheated water flash evaporation generates steam.

[0029] It should be noted that, in specific implementation, this utility model greatly reduces the maintenance frequency of the first pipeline 11 at the vapor phase outlet of the dryer 1. The cleaning cycle of the first pipeline 11 is reduced from less than one month to a regular cleaning once a year. The primary cooler 6 and the secondary condenser 7 no longer need to be shut down for maintenance and cleaning of scale, which greatly improves production efficiency. Example

[0030] This embodiment provides a vapor phase impurity removal system for a polycrystalline silicon slag slurry dryer. The difference from Embodiment 1 is that in this embodiment, the gas outlet of the secondary condenser 7 is connected to the cryogenic unit through a tail gas pipe 72, so that the tail gas that has not been condensed in the secondary condenser 7 is transported to the cryogenic unit for further condensation through the tail gas pipe 72.

[0031] In addition, the cryogenic unit can be replaced with an exhaust gas treatment unit for further treatment of the exhaust gas.

[0032] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A vapor phase impurity removal system for a polycrystalline silicon slurry dryer, characterized in that, include: A dryer is used to contain solids containing chlorosilanes and to heat the solids with steam to obtain gaseous chlorosilanes; The purification tower has its inlet connected to the top outlet of the dryer; the purification tower is used to remove impurities from gaseous chlorosilane by spraying, to obtain purified gaseous chlorosilane and liquid containing impurities. A multi-stage condensation mechanism is provided, with its inlet connected to the top outlet of the purification tower. The multi-stage condensation mechanism is used to receive the gaseous chlorosilane output from the purification tower and condense the gaseous chlorosilane to obtain liquid chlorosilane.

2. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 1, characterized in that, The multi-stage condensation mechanism includes: A primary cooler, the inlet of which is connected to the top outlet of the purification tower; A secondary condenser, the inlet of which is connected to the gas outlet of the primary cooler; The primary cooler and secondary condenser are used to sequentially condense gaseous chlorosilane to obtain liquid chlorosilane.

3. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 2, characterized in that, It also includes condensate tanks; The bottom outlet of the purification tower, the liquid outlet of the primary cooler, and the liquid outlet of the secondary condenser are all connected to the inlet of the condensate tank; the condensate tank is used to collect the liquid in the purification tower and the liquid chlorosilane obtained by condensation from the primary cooler and the secondary condenser.

4. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 2, characterized in that, The gas outlet of the secondary condenser is connected to the cryogenic unit via a tail gas pipe.

5. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 3, characterized in that, The liquid outlet of the condensate tank is connected to one end of the first delivery pipe; The other end of the first conveying pipe is connected to the slurry tank and is used to convey a portion of the liquid in the condensate tank to the slurry tank.

6. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 5, characterized in that, The liquid outlet of the condensate tank is also connected to one end of a second conveying pipe, and the other end of the second conveying pipe is connected to a spray cooler; and is used to convey a portion of the liquid in the condensate tank to the spray cooler; the spray cooler is used to cool the liquid conveyed from the second conveying pipe and convey it to the purification tower as spray liquid.

7. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 6, characterized in that, The liquid outlet of the condensate tank is connected to the inlet of the residual liquid pump, and the outlet of the residual liquid pump is connected to one end of the first delivery pipe and one end of the second delivery pipe.

8. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 1, characterized in that, The dryer has an inlet pipe for feeding in the heating medium.

9. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 8, characterized in that, The heating medium is hot water or superheated water, and the temperature of the hot water or superheated water is 90-180℃.

10. The vapor phase impurity removal system for a polycrystalline silicon slurry dryer according to claim 8, characterized in that, The heating medium is saturated steam or superheated steam, and the temperature of the saturated steam or superheated steam is 100-180℃.

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