High-boiling cracking circulating hydrogen chloride recycling system

Abstract

The utility model discloses a high-boiling cracking circulating hydrogen chloride recycling system which comprises a reaction kettle, a primary hydrogen chloride compression module, a rectifying tower, a tower top reflux tank, a secondary hydrogen chloride compression module and a fluidized bed, the primary hydrogen chloride compression module is connected with the feeding end of the reaction kettle; the rectifying tower is connected with the discharge end of the reaction kettle; the tower top reflux tank is connected to the rectifying tower through an extraction pipe; and the secondary hydrogen chloride compression module is connected between the tower top reflux tank and the fluidized bed. According to the system, circulating hydrogen chloride is recycled, and the circulating hydrogen chloride is not emptied to the tail gas treatment device, so that the tail gas treatment load and cost are reduced, tail gas emptying is reduced, and meanwhile, the sewage treatment load and cost are also reduced. Circulating hydrogen chloride is fed into a hydrogenation system through a compressor and reacts with silicon powder through a cold hydrogenation fluidized bed to prepare trichlorosilane, and hydrogen and chlorine are supplemented for a polycrystalline silicon production system.

Description

Technical Field

[0001] The utility model belongs to the field of polysilicon production, and particularly relates to a high-boiling cracking circulating hydrogen chloride recovery and reuse system. Background Technique

[0002] In polysilicon production, fresh hydrogen chloride is desorbed from hydrochloric acid and sent to a reaction kettle through a compressor. Excess hydrogen chloride undergoes a cracking reaction with 30% high-boiling substances under the action of a re-extraction agent to generate trichlorosilane and tetrachlorosilane. The jacket steam of the high-boiling reaction kettle heats the gas-phase chlorosilane and hydrogen chloride and enters a distillation column for separation. The recovered chlorosilane at the top of the column is sent to a hydrogenation system, and the non-condensable gas phase is sent to a buffer tank in front of the compressor of the hydrochloric acid desorption device. Part of the hydrogen chloride is recycled and sent back to the reaction kettle, and part of the hydrogen chloride is discharged to the main exhaust pipe and sent to a tail gas treatment device.

[0003] About 90 - 150 Nm³ / h of the partially discharged hydrogen chloride is sent to a tail gas treatment device and needs to be neutralized with lime milk. The neutralized sewage is sent to a sewage treatment device, and the qualified tail gas is discharged to the air. However, part of the circulating hydrogen chloride separated at the top of the high-boiling distillation column is recycled and used in the reaction kettle, and part is discharged to the tail gas treatment device, resulting in an increase in the production load and cost of downstream tail gas treatment. The hydrogen chloride introduced into the high-boiling reaction kettle is a mixture of pure hydrogen chloride and circulating hydrogen chloride. After long-term operation, problems such as poor cracking effect occur. Summary of the Invention

[0004] Purpose of the utility model: The technical problem to be solved by the utility model is to provide a high-boiling cracking circulating hydrogen chloride recovery and reuse system in view of the deficiencies of the prior art, realizing the recovery and reuse of circulating hydrogen chloride, no longer discharging circulating hydrogen chloride to the tail gas treatment device, reducing the tail gas treatment load and cost, reducing tail gas discharge, and at the same time reducing the sewage treatment load and cost.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] A high-boiling cracking circulating hydrogen chloride recovery and reuse system includes a reaction kettle, a first-stage hydrogen chloride compression module, a distillation column, a top reflux tank, a second-stage hydrogen chloride compression module, and a fluidized bed; the first-stage hydrogen chloride compression module is connected to the feed end of the reaction kettle; the distillation column is connected to the discharge end of the reaction kettle; the top reflux tank is connected to the distillation column through a draw-off pipe; the second-stage hydrogen chloride compression module is connected between the top reflux tank and the fluidized bed.

[0007] Specifically, the reaction kettle imports high-boiling materials through a high-boiling material pipe; the reaction kettle is connected to the first-stage hydrogen chloride compression module through a hydrogen chloride feed pipe; the reaction kettle imports an extraction agent through an extraction agent delivery pipe.

[0008] Specifically, the primary hydrogen chloride compression module includes a hydrochloric acid stripping system, a primary pre-buffer tank, a primary compressor, and a primary post-buffer tank, which are connected in sequence through pipelines.

[0009] Specifically, the side of the rectifying column is connected to the reaction kettle through a rectifying column feed pipe; a reboiler is arranged on the side of the rectifying column; a bottom discharge pipeline is provided at the bottom of the rectifying column; the bottom discharge pipeline is connected to a slurry tank through a bottom external discharge pipe and is connected to the lower side of the rectifying column through a bottom reflux pipe; the top of the rectifying column is connected to the overhead reflux tank through a top product extraction pipe.

[0010] Further, a circulating water cooler is arranged on the product extraction pipe connecting the overhead reflux tank and the rectifying column; the overhead reflux tank is connected to the secondary hydrogen chloride compression module through a top gas pipe, and an ethylene glycol cooler is also arranged on the top gas pipe.

[0011] Specifically, a bottom discharge pipeline is provided at the bottom of the overhead reflux tank; the bottom discharge pipeline is connected to a rough separation column through a bottom external discharge pipe and is connected to the upper side of the rectifying column through a bottom reflux pipe.

[0012] Further, a bottom circulation pump is arranged on the bottom discharge pipeline; a bottom circulation pump is arranged on the bottom discharge pipeline of the tank bottom.

[0013] Specifically, the secondary hydrogen chloride compression module includes a secondary pre-buffer tank, a secondary compressor, and a secondary post-buffer tank, which are connected in sequence through pipelines.

[0014] Further, the rear end of the secondary hydrogen chloride compression module is connected to a tertiary hydrogen chloride compression module through a secondary hydrogen chloride transfer pipe, and the tertiary hydrogen chloride compression module is connected to the fluidized bed through a tertiary hydrogen chloride transfer pipe; the tertiary hydrogen chloride compression module includes a tertiary pre-buffer tank, a tertiary compressor, and a tertiary post-buffer tank, which are connected in sequence through pipelines.

[0015] Specifically, a hydrogen gas inlet pipe is connected to the side of the fluidized bed, a silicon powder feed pipe is connected to the bottom, a silicon tetrachloride feed pipe is connected to the bottom, and a trichlorosilane product extraction pipe is connected to the top. Beneficial effects

[0016] (1) In this system, by recycling and reusing the circulating hydrogen chloride, the circulating hydrogen chloride is no longer discharged to the tail gas treatment device, reducing the tail gas treatment load and cost, reducing tail gas emissions, and at the same time reducing the sewage treatment load and cost. The high-boiling reaction kettle no longer uses circulating hydrogen chloride, that is, all pure hydrogen chloride is introduced, which is beneficial to the cracking reaction and improves the conversion rate of high-boiling substances. The circulating hydrogen chloride is sent into the hydrogenation system through a compressor, and trichlorosilane is prepared by reacting with silicon powder in a cold hydrogenation fluidized bed, supplementing hydrogen and chlorine elements to the polysilicon production system.

[0017] (2) Through this system, part of the recycled hydrogen chloride is vented to the tail gas treatment device at about 90 - 150 Nm³ / h, consuming 1 - 3 t / h of lime powder. It is recycled and sent to the cold hydro - chlorination system, reducing the consumption of lime powder and the discharged sewage. The conversion rate of high - boilers is increased. The content of trichlorosilane rises from 20 - 25% to 30 - 35%, the content of silicon tetrachloride drops from 70 - 80% to 60 - 70%, the content of dichlorosilane drops to 1%, and the content of polysilane in chlorosilanes drops to 1%. The operation time of high - boiling cracking is extended, and the consumption of extractant is reduced. Description of the Drawings

[0018] The following further specifically describes the present utility model in conjunction with the drawings and specific embodiments, and the above - mentioned and / or other advantages of the present utility model will become clearer.

[0019] Figure 1 It is a schematic diagram of the overall structure of the system.

[0020] Among them, each reference numeral represents respectively:

[0021] 10 - Reactor; 101 - High - boiling material pipe; 102 - Hydrogen chloride feed pipe; 103 - Extractant delivery pipe; 20 - First - stage hydrogen chloride compression module; 201 - Hydrochloric acid analysis and separation system; 202 - First - stage pre - buffer tank; 203 - First - stage compressor; 204 - First - stage post - buffer tank; 30 - Distillation column; 301 - Distillation column feed pipe; 302 - Reboiler; 303 - Bottom discharge pipeline; 304 - Bottom external discharge pipe; 305 - Bottom reflux pipe; 306 - Top product pipe; 307 - Bottom circulation pump; 40 - Circulating water cooler; 50 - Top reflux tank; 501 - Tank bottom discharge pipeline; 502 - Tank bottom external discharge pipe; 503 - Tank bottom reflux pipe; 504 - Top gas pipe; 505 - Tank bottom circulation pump; 60 - Ethylene glycol cooler; 70 - Second - stage hydrogen chloride compression module; 701 - Second - stage pre - buffer tank; 702 - Second - stage compressor; 703 - Second - stage post - buffer tank; 704 - Second - stage hydrogen chloride delivery pipe; 80 - Third - stage hydrogen chloride compression module; 801 - Third - stage pre - buffer tank; 802 - Third - stage compressor; 803 - Third - stage post - buffer tank; 804 - Third - stage hydrogen chloride delivery pipe; 90 - Fluidized bed; 901 - Hydrogen inlet pipe; 902 - Silicon powder feed pipe; 903 - Silicon tetrachloride feed pipe; 904 - Trichlorosilane product pipe. Specific Embodiments

[0022] The present utility model can be better understood according to the following embodiments.

[0023] The structures, proportions, sizes, etc. shown in the accompanying drawings of the specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the conditions for the implementation of the present utility model. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the efficacy that the present utility model can produce and the purpose that can be achieved, should still fall within the scope covered by the technical content disclosed in the present utility model. At the same time, terms such as "upper", "lower", "front", "rear", "middle", etc. cited in this specification are only for the convenience of clear narration and are not used to limit the scope for the implementation of the present utility model. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope for the implementation of the present utility model.

[0024] Combined with Figure 1 As shown, the high-boiling cracking cyclic hydrogen chloride recovery and reuse system of the present utility model includes a reaction kettle 10, a first-stage hydrogen chloride compression module 20, a rectifying column 30, a top reflux tank 50, a second-stage hydrogen chloride compression module 70, and a fluidized bed 90; the first-stage hydrogen chloride compression module 20 is connected to the feed end of the reaction kettle 10; the rectifying column 30 is connected to the discharge end of the reaction kettle 10; the top reflux tank 50 is connected to the rectifying column 30 through a withdrawal pipe; the second-stage hydrogen chloride compression module 70 is connected between the top reflux tank 50 and the fluidized bed 90.

[0025] Among them, the reaction kettle 10 introduces high-boiling materials through a high-boiling material pipe 101; the reaction kettle 10 is connected to the first-stage hydrogen chloride compression module 20 through a hydrogen chloride feed pipe 102; the reaction kettle 10 introduces an extractant through an extractant delivery pipe 103.

[0026] In some embodiments, the first-stage hydrogen chloride compression module 20 includes a hydrochloric acid analysis system 201, a first-stage pre-buffer tank 202, a first-stage compressor 203, and a first-stage post-buffer tank 204 that are connected in sequence through pipes.

[0027] In some embodiments, the rectifying column 30 is connected to the reaction kettle 10 through a rectifying column feed pipe 301 on the side; a reboiler 302 is provided on the side of the rectifying column 30; a bottom discharge pipeline 303 is provided at the bottom of the rectifying column 30; the bottom discharge pipeline 303 is connected to a slurry tank through a bottom external discharge pipe 304 and is connected to the lower side of the rectifying column 30 through a bottom reflux pipe 305; the top of the rectifying column 30 is connected to the top reflux tank 50 through a top withdrawal pipe 306.

[0028] In some embodiments, a circulating water cooler 40 is provided on the extraction pipe connecting the top reflux drum 50 and the distillation column 30; the top reflux drum 50 is connected to the secondary hydrogen chloride compression module 70 through a top gas phase pipe 504, and an ethylene glycol cooler 60 is also provided on the top gas phase pipe 504.

[0029] In some embodiments, a bottom discharge pipeline 501 is provided at the bottom of the top reflux drum 50; the bottom discharge pipeline 501 is connected to the rough separation column through a bottom external discharge pipe 502 and is connected to the upper side of the distillation column 30 through a bottom reflux pipe 503.

[0030] In some embodiments, a bottom circulation pump 307 is provided on the bottom discharge pipeline 303; a bottom circulation pump 505 is provided on the bottom discharge pipeline 501.

[0031] In some embodiments, the secondary hydrogen chloride compression module 70 includes a secondary pre-buffer tank 701, a secondary compressor 702, and a secondary post-buffer tank 703 connected in sequence through pipelines.

[0032] In some embodiments, the rear end of the secondary hydrogen chloride compression module 70 is connected to a tertiary hydrogen chloride compression module 80 through a secondary hydrogen chloride delivery pipe 704, and the tertiary hydrogen chloride compression module 80 is connected to the fluidized bed 90 through a tertiary hydrogen chloride delivery pipe 804; the tertiary hydrogen chloride compression module 80 includes a tertiary pre-buffer tank 801, a tertiary compressor 802, and a tertiary post-buffer tank 803 connected in sequence through pipelines.

[0033] In some embodiments, a hydrogen gas inlet pipe 901 is connected to the side of the fluidized bed 90, a silicon powder feed pipe 902 is connected to the bottom, a silicon tetrachloride feed pipe 904 is connected to the bottom, and a trichlorosilane extraction pipe 904 is connected to the top.

[0034] The process principle used is as follows:

[0035] The high-boiling substances are transported to the reaction kettle 10 by the reaction kettle feed pump for reaction. The molecular formula of the high-boiling substances is Si 2 Cl 6 For simulation, the reaction equation is as follows: Si 2 Cl 6 + HCl → SiHCl 3 + SiCl 4 .

[0036] The high-boiling substances in the reaction kettle feed buffer tank and the HCL gas from hydrochloric acid analysis enter the high-boiling reaction kettle and react under the action of the extractant to generate SiHCl 3 and SiCl 4。The high-boiling reaction kettle jacket is heated by passing steam. The gaseous chlorosilane and hydrogen chloride enter the distillation column for separation. The recovered chlorosilane at the top of the column is sent to the hydrogenation unit, and the non-condensable gas phase is sent to the hydrochloric acid analysis unit for HCl recycling. Part of the recycled hydrogen chloride is vented to the tail gas treatment unit for neutralization treatment.

[0037] When the reaction kettle operates at full load, about 300 Nm³ / h of the vented hydrogen chloride with a pressure of 0.15 - 0.18 Mpa is compressed to 0.55 - 0.68 Mpa by a compressor and sent to the pre-buffer tank of high-pressure hydrogen chloride for hydrogenation, and then compressed to 3.0 - 3.3 Mpa by the high-pressure hydrogen chloride compressor for hydrogenation and sent to the cold hydrogenation system to participate in the reaction.

[0038] Analysis results of the recycled hydrogen chloride gas: Samples of the recycled hydrogen chloride were taken and analyzed multiple times at the drain of the gas phase pipeline of the distillation column. The content of each component in the recycled hydrogen chloride gas is as follows: HCL: 20 - 30%, dichlorosilane: 0 - 10%, trichlorosilane: 5 - 20%, silicon tetrachloride: 10 - 20%, nitrogen: 10 - 15%, hydrogen: 30 - 40%, oxygen: less than 1%. The oxygen in the recycled hydrogen chloride is due to the use of a sampling bag for sampling, and the oxygen in the bag was not completely replaced.

[0039] Analysis results of the recycled hydrogen for hydrogenation: Samples of the recycled hydrogen were taken and analyzed using a sampler at the drain of the main vent pipe of the hydrogenation system. The content of each component is as follows: hydrogen chloride is less than 1%, dichlorosilane: 5%, trichlorosilane: 3%, silicon tetrachloride: less than 1%, nitrogen: 5 - 10%, oxygen: less than 1%, hydrogen: more than 90%.

[0040] Compared with the recycled hydrogen, the content of dichlorosilane and nitrogen in the recycled hydrogen chloride gas is relatively high. The nitrogen in the recycled hydrogen chloride is caused by using nitrogen gas to press the materials when adding agents to the reaction kettle. In the later stage, the control can be optimized to reduce the nitrogen content. The recycled hydrogen chloride is beneficial to the hydrogenation system and increases the chlorine and hydrogen elements in the system.

[0041] The present utility model provides an idea and method for the recycling and reuse system of high-boiling cracking recycled hydrogen chloride. There are many methods and ways to specifically implement this technical solution. The above description is only the preferred embodiment of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present utility model, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present utility model. Each component not clearly defined in this embodiment can be implemented by existing technologies.

Claims

1. A high boiling cracking cycle hydrogen chloride recovery and reuse system, characterized in that: The invention comprises a reactor (10), a primary hydrogen chloride compression module (20), a distillation tower (30), a tower top reflux tank (50), a secondary hydrogen chloride compression module (70) and a fluidized bed (90); the primary hydrogen chloride compression module (20) is connected to the feed end of the reactor (10); the distillation tower (30) is connected to the discharge end of the reactor (10); the tower top reflux tank (50) is connected to the distillation tower (30) via a production pipe; and the secondary hydrogen chloride compression module (70) is connected between the tower top reflux tank (50) and the fluidized bed (90).

2. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1 is characterized in that: The reactor (10) is introduced with high boiling material via a high boiling material pipe (101); the reactor (10) is connected to the primary hydrogen chloride compression module (20) via a hydrogen chloride feed pipe (102); and the reactor (10) is introduced with an extractant via an extractant delivery pipe (103).

3. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1 is characterized in that: The first-stage hydrogen chloride compression module (20) comprises a hydrochloric acid analysis system (201), a first-stage front buffer tank (202), a first-stage compressor (203) and a first-stage rear buffer tank (204) which are sequentially connected via pipelines.

4. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1, characterized in that: The side of the distillation tower (30) is connected to the reactor (10) via a distillation tower feed pipe (301); a reboiler (302) is arranged on the side of the distillation tower (30); a bottom discharge pipeline (303) is arranged at the bottom of the distillation tower (30); the bottom discharge pipeline (303) is connected to a slurry tank via a bottom discharge pipe (304), and is connected to the lower side of the distillation tower (30) via a bottom reflux pipe (305); the top of the distillation tower (30) is connected to the tower top reflux tank (50) via a top extraction pipe (306).

5. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1, characterized in that: A circulating water cooler (40) is provided on the extraction pipe connected between the tower top reflux tank (50) and the distillation tower (30); the tower top reflux tank (50) is connected to the secondary hydrogen chloride compression module (70) via a top gas phase pipe (504), and an ethylene glycol cooler (60) is also provided on the top gas phase pipe (504).

6. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 4, characterized in that: A tank bottom discharge pipeline (501) is provided at the bottom of the tower top reflux tank (50); the tank bottom discharge pipeline (501) is connected to the coarse fraction tower via a tank bottom external discharge pipe (502), and is connected to the upper side of the distillation tower (30) via a tank bottom reflux pipe (503).

7. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 6, characterized in that: The kettle bottom discharge pipeline (303) is provided with a kettle bottom circulation pump (307); and the tank bottom discharge pipeline (501) is provided with a tank bottom circulation pump (505).

8. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1, characterized in that: The two-stage hydrogen chloride compression module (70) comprises a two-stage front buffer tank (701), a two-stage compressor (702) and a two-stage rear buffer tank (703) which are sequentially connected via pipelines.

9. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1, characterized in that: The rear end of the secondary hydrogen chloride compression module (70) is connected to the tertiary hydrogen chloride compression module (80) via a secondary hydrogen chloride delivery pipe (704); the tertiary hydrogen chloride compression module (80) is connected to the fluidized bed (90) via a tertiary hydrogen chloride delivery pipe (804); the tertiary hydrogen chloride compression module (80) comprises a tertiary front buffer tank (801), a tertiary compressor (802), and a tertiary rear buffer tank (803) which are sequentially connected via pipelines.

10. The high boiling cracking cycle hydrogen chloride recovery and reuse system according to claim 1, characterized in that: The fluidized bed (90) is connected to a hydrogen inlet pipe (901) and a silicon powder feed pipe (902) on its side, to a silicon tetrachloride feed pipe (903) on its bottom, and to a trichlorosilane extraction pipe (904) on its top.

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