Cold hydrogenation tail gas recovery system

Abstract

The utility model discloses a cold hydrogenation tail gas recovery system which comprises a silicon powder high-pressure tank, an emptying dust remover, a wet dust removal tank, a condenser and a hydrogen supplementing front buffer tank which are connected in sequence, silicon tetrachloride liquid is contained in the wet dust removal tank until the liquid level is 40-60%; a discharging pipeline of the emptying dust remover is inserted into the bottom of the wet dust removal tank, an exhaust pipe is arranged at the top of the wet dust removal tank and connected to a condenser, and gas is condensed and then collected into the buffer tank before hydrogen is supplemented for standby application. According to the system, air defense hydrogen of the silicon powder high-pressure tank can be recycled, emptying hydrogen of the silicon powder high-pressure tank is recycled after being subjected to dust removal through the wet dust removal tank, the treated hydrogen enters the cold hydrogenation system for the second time to participate in the reaction, the unit consumption of hydrogen produced by trichlorosilane is reduced, and the cost is saved.

Description

Technical Field

[0001] This utility model belongs to the field of polycrystalline silicon production, specifically relating to a cold hydrogenation tail gas recovery system. Background Technology

[0002] In the hydrogenation process of polysilicon production, a mixture of silicon tetrachloride and hydrogen is heated to a certain temperature and then enters a fluidized bed from the bottom. Industrial silicon powder, mixed with a certain proportion of catalyst, is fluidized and reacted under high temperature, high pressure, and catalytic conditions to produce trichlorosilane. The silicon powder required for the fluidized bed reactor is intermittently replenished from a high-pressure silicon powder tank. The pressure in the high-pressure silicon powder tank (approximately 3.0-3.3 MPa) is increased by hydrogen to 0.3 MPa above the fluidized bed reactor pressure. When the silicon powder in the high-pressure silicon powder tank is depleted, it needs to be depressurized to atmospheric pressure before replenishment. The hydrogen gas from the high-pressure silicon powder tank is depressurized after passing through a dust collector and then discharged directly into the atmosphere after treatment. Because the vented hydrogen gas from the high-pressure silicon powder tank contains a small amount of fine silicon powder particles, it is not currently recycled.

[0003] Because the hydrogen in the high-pressure silicon powder tank comes from the system's circulating hydrogen, which contains trace amounts of chlorosilane, the hydrogen discharged from the high-pressure silicon powder tank to the tail gas treatment device needs to undergo an acid-base neutralization reaction with lime milk before it can be discharged into the atmosphere. This not only wastes hydrogen but also increases the amount of lime milk used in the tail gas treatment device. Summary of the Invention

[0004] Purpose of this utility model: The technical problem to be solved by this utility model is to address the shortcomings of the existing technology by providing a cold hydrogenation tail gas recovery system to recover hydrogen gas from the silicon powder high-pressure tank. After processing, the hydrogen gas is reintroduced into the cold hydrogenation system to participate in the reaction, thereby reducing the hydrogen consumption per unit of trichlorosilane production and saving costs.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0006] A cold hydrogenation tail gas recovery system includes a silicon powder high-pressure tank, a venting dust collector, a wet scrubbing tank, a condenser, and a pre-hydrogen buffer tank connected in sequence. The wet scrubbing tank is filled with silicon tetrachloride liquid to a level of 40-60%. The discharge pipeline of the venting dust collector is inserted into the bottom of the wet scrubbing tank. An exhaust pipe is installed at the top of the wet scrubbing tank and connected to the condenser. The gas is condensed and collected in the pre-hydrogen buffer tank for later use.

[0007] Furthermore, the inlet of the silicon powder high-pressure tank is connected to a supplementary silicon powder feed pipe, the bottom is connected to a fluidized bed reactor, and the top discharge pipe is connected to an venting dust collector.

[0008] Furthermore, the top exhaust pipe of the venting dust collector is divided into two pipelines that can be controlled to be turned on and off separately. One pipeline is connected to the exhaust gas treatment device, and the other pipeline is inserted into the wet dust collector. The bottom dust discharge pipe of the venting dust collector is connected to the silicon powder high-pressure tank.

[0009] Furthermore, the bottom of the wet dust collector is connected to the slurry treatment device via a discharge pipe, and the top is connected to the condenser via an exhaust pipe. The wet dust collector is equipped with a level gauge for monitoring the internal liquid level.

[0010] Furthermore, the discharge pipe at the bottom of the wet dust collector is connected to a silicon tetrachloride flushing pipe, which is used to flush the discharge pipe at the bottom of the wet dust collector with clean silicon tetrachloride.

[0011] Furthermore, the condenser is a Freon condenser, with its end connected to an air release condensate collection tank via a condensate collection pipe, and connected to a replenishment hydrogen pre-buffer tank at the rear end via a gas phase pipe.

[0012] Furthermore, a post-replenishment gas pipe is also connected to the gas phase pipe at the end of the condenser, which combines the condensed gas phase from the condenser with the externally replenished hydrogen and sends it to the pre-replenishment hydrogen buffer tank.

[0013] Furthermore, a gas phase buffer tank and a hydrogen replenishment compressor are sequentially arranged between the condenser and the hydrogen replenishment pre-buffer tank. The condensed gas phase from the condenser is sent into the gas phase buffer tank, and then compressed and increased by the hydrogen replenishment compressor before being sent into the hydrogen replenishment pre-buffer tank.

[0014] Furthermore, a regulating valve is installed at the inlet of the wet dust collector to control the pressure of the dust collector; a regulating valve is installed at the outlet of the wet dust collector to adjust the gas output of the wet dust collector according to the inlet pressure of the supplementary hydrogen compressor.

[0015] Furthermore, the top of the wet dust collector is equipped with a rupture disc and a safety valve to prevent overpressure and ensure safety. Beneficial effects

[0016] (1) The present invention can recover the hydrogen gas released from the high pressure tank of silicon powder. The hydrogen gas released from the high pressure tank of silicon powder is recovered and reused after being removed by a wet dust collector. After being processed, it enters the cold hydrogenation system again to participate in the reaction, thereby reducing the hydrogen consumption per unit of trichlorosilane production and saving costs.

[0017] (2) The present invention system can reduce the workload of exhaust gas treatment device, reduce the amount of lime slurry used, and save costs. Attached Figure Description

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0019] Figure 1 This is a schematic diagram of the overall structure of the cold hydrogenation tail gas recovery system of this utility model.

[0020] The reference numerals in the attached figures represent:

[0021] 1-Silicon powder high-pressure tank; 2-Ventilation dust collector; 3-Wet dust collector; 4-Level gauge; 5-Condenser; 6-Ventilation condensate collection tank; 7-Gas phase buffer tank; 8-Supplemental hydrogen compressor; 9-Supplemental hydrogen pre-buffer tank. Detailed Implementation

[0022] The present invention can be better understood from the following embodiments.

[0023] The structures, proportions, and sizes shown in the accompanying drawings are merely for illustrative purposes and to aid those skilled in the art. They are not intended to limit the scope of this invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, terms such as "upper," "lower," "front," "rear," and "middle" used in this specification are merely for clarity and not intended to limit the scope of this invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this invention.

[0024] like Figure 1 As shown, the cold hydrogenation tail gas recovery system of this utility model includes a silicon powder high-pressure tank 1, an venting dust collector 2, a wet dust collector 3, a condenser 5, and a hydrogen replenishment buffer tank 9 connected in sequence. The wet dust collector 3 is filled with silicon tetrachloride liquid to the level indicator of 40-60%. The discharge pipeline of the venting dust collector 2 is inserted into the bottom of the wet dust collector 3. The top of the wet dust collector 3 is provided with an exhaust pipe connected to the condenser 5. After condensation, the gas is collected in the hydrogen replenishment buffer tank 9 for later use.

[0025] The silicon powder high-pressure tank 1 has its inlet connected to a supplementary silicon powder feed pipe, its bottom connected to a fluidized bed reactor, and its top discharge pipe connected to an venting dust collector 2.

[0026] In some embodiments, the top exhaust pipe of the venting dust collector 2 is divided into two pipelines that can be controlled to be turned on and off separately. One pipeline is connected to the exhaust gas treatment device, and the other pipeline is inserted into the wet dust collector 3; the bottom dust discharge pipe of the venting dust collector 2 is connected to the silicon powder high-pressure tank 1.

[0027] In some embodiments, the bottom of the wet dust collector 3 is connected to the slurry treatment device via a discharge pipe, and the top is connected to the condenser 5 via an exhaust pipe. The wet dust collector 3 is equipped with a level gauge 4 for monitoring the internal liquid level.

[0028] In some embodiments, the discharge pipe at the bottom of the wet dust collector 3 is connected to a silicon tetrachloride flushing pipe, which is used to flush the discharge pipe at the bottom of the wet dust collector 3 with clean silicon tetrachloride.

[0029] In some embodiments, the condenser 5 is a Freon condenser, with its end connected to the venting condensate collection tank 6 via a condensate collection pipe and connected to the replenishing hydrogen pre-buffer tank 9 at the rear end via a gas phase pipe.

[0030] In some embodiments, a post-replenishment gas pipe is also connected to the gas phase pipe at the end of the condenser 5, so that the condensed gas phase coming out of the condenser 5 is combined with the externally replenished hydrogen and sent to the pre-replenishment hydrogen buffer tank 9.

[0031] In some embodiments, a gas phase buffer tank 7 and a hydrogen replenishment compressor 8 are sequentially arranged between the condenser 5 and the hydrogen replenishment pre-buffer tank 9. The condensed gas phase from the condenser 5 is sent to the gas phase buffer tank 7, and then compressed and increased by the hydrogen replenishment compressor 8 before being sent to the hydrogen replenishment pre-buffer tank 9.

[0032] In some embodiments, a regulating valve is provided at the inlet of the wet dust collector 3 to control the pressure of the dust collector; a regulating valve is provided at the outlet of the wet dust collector 3 to adjust the gas output of the wet dust collector 3 according to the inlet pressure of the supplementary hydrogen compressor 8.

[0033] In some embodiments, the top of the wet dust collector 3 is provided with a rupture disc and a safety valve to prevent overpressure and ensure safety.

[0034] This invention features a wet dust collector 3 installed at the outlet of the venting dust collector 2 of the high-pressure silicon powder tank 1. This removes small amounts of fine silicon powder particles from the vented hydrogen gas from the high-pressure silicon powder tank 1. The wet dust collector 3 is equipped with a level gauge and is filled with silicon tetrachloride liquid to 50% level. The inlet pipeline of the dust collector is inserted to the bottom of the dust collector. The vented hydrogen gas from the high-pressure silicon powder tank 1 enters the bottom of the dust collector, is washed by chlorosilane, and is then released from above the chlorosilane liquid surface into the hydrogen outlet at the top of the dust collector. After being released from the top of the dust collector, the hydrogen gas passes through the Freon condenser 5 to condense the chlorosilane. The gas phase then mixes with the externally supplied hydrogen gas and enters the supplementary hydrogen compressor 8 (compressor inlet pressure approximately 0.5 MPa). After being pressurized, the hydrogen enters the cold hydrogenation reaction system.

[0035] A regulating valve is installed at the inlet of the wet dust collector 3 to control the pressure of the dust collector; a regulating valve is installed at the outlet of the wet dust collector 3 to adjust the output of the wet dust collector according to the inlet pressure of the supplementary hydrogen compressor 8.

[0036] The bottom of the wet dust collector 3 is equipped with a slag discharge pipeline to the slurry treatment device and a clean silicon tetrachloride liquid replenishment pipeline. The dust content in the silicon tetrachloride liquid inside the wet dust collector is periodically checked. When the dust content reaches a certain level, the slag discharge valve is opened to discharge slag to the slurry treatment device during the off-peak period when the silicon powder high-pressure tank is not emptied. After slag discharge, the slag discharge pipeline is flushed with clean silicon tetrachloride. After flushing, the slag discharge valve to the slurry treatment device is closed, and clean silicon tetrachloride liquid is replenished to the wet dust collector until the liquid level indicator reaches 60%.

[0037] This utility model provides a concept and method for a cold hydrogenation tail gas recovery system. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of this utility model. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model. All components not explicitly stated in this embodiment can be implemented using existing technology.

Claims

1. A cold hydrogenation tail gas recovery system characterized by, The system includes a silicon powder high-pressure tank (1), an venting dust collector (2), a wet dust collector (3), a condenser (5), and a hydrogen replenishment buffer tank (9) connected in sequence. The wet dust collector (3) is filled with silicon tetrachloride liquid to a level of 40-60%. The discharge line of the venting dust collector (2) is inserted into the bottom of the wet dust collector (3). The top of the wet dust collector (3) is equipped with an exhaust pipe connected to the condenser (5). The gas is collected in the hydrogen replenishment buffer tank (9) after condensation for later use.

2. The cold hydrogenated tail gas recovery system of claim 1, wherein, The inlet of the silicon powder high-pressure tank (1) is connected to a supplementary silicon powder feed pipe, the bottom is connected to a fluidized bed reactor, and the top discharge pipe is connected to an venting dust collector (2).

3. The cold hydrogenated tail gas recovery system of claim 1, wherein, The top exhaust pipe of the venting dust collector (2) is divided into two pipelines that can be controlled to open and close separately. One pipeline is connected to the tail gas treatment device, and the other pipeline is inserted into the wet dust collector (3). The bottom dust discharge pipe of the venting dust collector (2) is connected to the silicon powder high-pressure tank (1).

4. The cold hydrogenated tail gas recovery system of claim 1, wherein, The bottom of the wet dust collector (3) is connected to the slurry treatment device through a discharge pipe, and the top is connected to the condenser (5) through an exhaust pipe. The wet dust collector (3) is equipped with a level gauge (4) for monitoring the internal liquid level.

5. The cold hydrogenated tail gas recovery system of claim 4, wherein, The discharge pipe at the bottom of the wet dust collector (3) is connected to a silicon tetrachloride flushing pipe, which is used to flush the discharge pipe at the bottom of the wet dust collector (3) with clean silicon tetrachloride.

6. The cold hydrogenated tail gas recovery system of claim 1, wherein, The condenser (5) is a Freon condenser, and its end is connected to the venting condensate collection tank (6) through the condensate collection pipe, and connected to the replenishment hydrogen pre-buffer tank (9) at the rear end through the gas phase pipe.

7. The cold hydrogenated tail gas recovery system of claim 6, wherein, The gas phase pipe at the end of the condenser (5) is also connected to a post-supply gas pipe, which combines the condensed gas phase from the condenser (5) with the externally supplied hydrogen and sends it to the pre-supply hydrogen buffer tank (9).

8. The cold hydrogenated tail gas recovery system of claim 6, wherein, A gas phase buffer tank (7) and a hydrogen replenishment compressor (8) are sequentially arranged between the condenser (5) and the hydrogen replenishment buffer tank (9). The condensed gas phase from the condenser (5) is sent into the gas phase buffer tank (7), and then compressed and increased by the hydrogen replenishment compressor (8) before being sent into the hydrogen replenishment buffer tank (9).

9. The cold hydrogenated tail gas recovery system of claim 8, wherein, The wet dust collector (3) is equipped with a regulating valve at the inlet to control the pressure of the dust collector; the wet dust collector (3) is equipped with a regulating valve at the outlet to adjust the gas output of the wet dust collector (3) according to the gas inlet pressure of the supplementary hydrogen compressor (8).

10. The cold hydrogenated tail gas recovery system of claim 4, wherein, The wet dust collector (3) is equipped with a rupture disc and a safety valve at the top to prevent overpressure and ensure safety.

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