A compression condensation recovery system for polysilicon off-gas

Abstract

The utility model discloses a kind of compressed condensation recovery systems for polysilicon waste gas, it is related to polysilicon venting waste gas recycling technical field, including exhaust gas compressor, waste gas cooler and adsorption column connected in order, the exhaust gas inlet of exhaust gas compressor connects exhaust gas pipeline, the exhaust gas outlet of adsorption column connects waste gas shower tower, the liquid outlet of waste gas cooler connects rectification process, the exhaust gas inlet of exhaust gas compressor is provided with machine front filter, the exhaust gas outlet of exhaust gas compressor is provided with machine rear filter, the exhaust gas inlet of adsorption column is provided with column front filter.Aiming at the characteristics of polysilicon waste gas complex component, filter is set to intercept and filter automatic deslagging system, realize waste gas recovery device long-period operation, reduce personnel operation intensity and operation risk, save manpower, while greatly reduce equipment inspection and maintenance cost.

Description

Technical Field

[0001] This utility model relates to the field of polycrystalline silicon vent gas recovery and utilization technology, and in particular to a polycrystalline silicon vent gas compression and condensation recovery system. Background Technology

[0002] Currently, polysilicon waste gas recovery mainly uses a compressor to pressurize the gas and then uses cryogenic cooling to condense and recover chlorosilanes in the waste gas. The condensed waste gas is then discharged after being adsorbed by activated carbon. The compressor is equipped with an inlet pipe filter to intercept solid impurities in the waste gas. Since the waste gas may contain acidic solid impurities such as silicon powder and silica, the compressor inlet filter is prone to clogging. To ensure continuous production, two filters are set up in parallel, with one in operation and one on standby under normal conditions. However, the conventional compressor inlet filter is a pipe filter, and cleaning it after clogging requires an open-loop operation. Cleaning the filter containing acidic solid impurities such as silicon powder and silica is difficult and risky. Furthermore, this type of filter cannot completely filter impurities, which also poses a risk of clogging to the compressor and the downstream pipes and equipment. The continuous operation cycle of the equipment is relatively short, and the maintenance frequency is high. Utility Model Content

[0003] This utility model aims to provide a compression condensation recovery system for polycrystalline silicon waste gas. Targeting the complex composition of polycrystalline silicon waste gas, it incorporates a filter for interception and filtration, along with an automatic slag discharge system. This enables long-term operation of the waste gas recovery device, reduces the intensity and risk of manual operation, saves manpower, and significantly reduces equipment maintenance costs.

[0004] To achieve the above-mentioned objectives, the technical solution of this utility model is as follows: A polycrystalline silicon waste gas compression and condensation recovery system includes a waste gas compressor, a waste gas cooler, and an adsorption column connected sequentially. The waste gas inlet of the waste gas compressor is connected to a waste gas pipeline, the waste gas outlet of the adsorption column is connected to a waste gas scrubbing tower, and the liquid outlet of the waste gas cooler is connected to a distillation process. An organic pre-filter is installed at the waste gas inlet of the waste gas compressor, an organic post-filter is installed at the waste gas outlet of the waste gas compressor, and a column pre-filter is installed at the waste gas inlet of the adsorption column.

[0005] Two pre-filters are connected in parallel.

[0006] Both the pre-machine filter and the post-machine filter are bag filters.

[0007] The column pre-filter is a ceramic membrane cartridge filter.

[0008] The pre-machine filter, post-machine filter, and pre-column filter are each equipped with a backflush outlet. The filter element outlets of the pre-machine filter, post-machine filter, and pre-column filter are each connected to a compressed nitrogen pipeline. The filter element outlets of the pre-machine filter, post-machine filter, and pre-column filter are each equipped with a solenoid valve.

[0009] The backflush outlets of the pre-machine filter and the post-machine filter are respectively connected to silicon powder collection tanks.

[0010] The outlet of the silicon powder collection tank is connected to the second waste gas scrubbing tower. The collected acidic solid waste medium is discharged to the second waste gas scrubbing tower through a pipeline, realizing the closed-loop neutralization and hydrolysis of the collected acidic solid waste medium.

[0011] The exhaust gas outlet of the pre-filter is equipped with a buffer tank one, the exhaust gas outlet of the post-filter is equipped with a buffer tank two, and the exhaust gas outlet of the adsorption column is equipped with a buffer tank three.

[0012] The beneficial effects of this utility model are: 1. In this utility model, the compressor inlet serves as the starting point of the entire waste gas recovery device. Waste gas from each device enters the device and first reaches this point; therefore, a first interception is set here to intercept the silicon powder and silica entrained in the waste gas, preventing internal blockage of the compressor. Furthermore, long-term operational observation revealed that during the operation of the waste gas recovery system, the waste gas not only contains solid silicon powder and silica but also trace amounts of oxygen. During compression by the compressor, the temperature and pressure of the waste gas increase. During this process, the organosilicon gas in the waste gas reacts chemically with the trace oxygen, generating silica after the compressor, which then blocks the compressor outlet. The equipment and pipelines at the outlet of the compressor require a filter to be added. The exhaust gas adsorption column uses activated carbon for physical adsorption. To prevent the micropores of the activated carbon from clogging and affecting its adsorption capacity, a Johnson filter is installed at the inlet of the adsorption column for interception. However, in actual operation, the Johnson filter has a small filtration area and is prone to clogging. The adsorption column only operates for about one week and is difficult to clean. The adsorption column must be shut down and completely replaced before cleaning can be carried out. The replacement of activated carbon in the adsorption column is also difficult and time-consuming. Therefore, a separate filtration device is installed at the inlet of the adsorption column to ensure continuous operation of the adsorption column.

[0013] 2. In this invention, the material intercepted at both the compressor inlet and outlet contains silica and is not dry enough. When intercepted by the filter, silica powder and silica easily adhere to the surface of the filter element, resulting in poor automatic backflushing effect. Therefore, both the compressor inlet and outlet filters adopt filter bag filters. By utilizing the characteristic of the filter bag filter to deform during backflushing, the silica powder and silica are allowed to fall off the surface of the filter bag, thus solving the problem that the filter cannot operate for a long time due to the adhesion of silica powder and silica.

[0014] 3. In this utility model, after filtration at the compressor inlet and outlet, the amount of impurities at the adsorption column inlet is actually very small, and the adhesion of impurities at this point is low. The main reason why the Johnson filter at the adsorption column inlet is prone to clogging is that its filtration area is too small. When selecting the adsorption column inlet filter, the main considerations are: a. High filtration accuracy to prevent fine solid impurities from penetrating and clogging the activated carbon micropores; b. The filter element material is not easily damaged to ensure the filter's operating cycle. Therefore, when selecting the adsorption column inlet filter, a ceramic membrane filter element with a filtration accuracy of 1 micron is selected. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the polycrystalline silicon waste gas compression condensation and recovery system of this utility model.

[0016] Among them, 1. Exhaust gas compressor; 2. Exhaust gas cooler; 3. Adsorption column; 4. Exhaust gas pipeline; 5a. Exhaust gas scrubbing tower one; 5b. Exhaust gas scrubbing tower two; 6. Distillation process; 7. Pre-machine filter; 8. Post-machine filter; 9. Pre-column filter; 10. Silica powder collection tank; 11a. Buffer tank one; 11b. Buffer tank two; 11c. Buffer tank three. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0018] Example 1 This embodiment provides a polycrystalline silicon waste gas compression and condensation recovery system, including a waste gas compressor 1, a waste gas cooler 2, and an adsorption column 3 connected sequentially. The waste gas inlet of the waste gas compressor 1 is connected to a waste gas pipeline 4, the waste gas outlet of the adsorption column 3 is connected to a waste gas scrubbing tower 5a, the liquid outlet of the waste gas cooler 2 is connected to a distillation process 6, an organic pre-filter 7 is installed at the waste gas inlet of the waste gas compressor 1, an organic post-filter 8 is installed at the waste gas outlet of the waste gas compressor 1, and a column pre-filter 9 is installed at the waste gas inlet of the adsorption column 3.

[0019] In this embodiment, the polysilicon waste gas consists of waste gas from the furnace shutdown and replacement process of the reduction process, non-condensable gas from the distillation process 6, waste gas from the synthesis unit, and waste gas from the recovery unit. The polysilicon waste gas enters the pre-machine filter 7 via waste gas pipeline 4, where it intercepts impurities such as silicon powder and silicon dioxide. It then enters the waste gas compressor 1 for pressurization. The pressurized waste gas is filtered again by the post-machine filter 8 to remove the silicon dioxide generated during compression. It then enters the waste gas cooler 2, where the condensed chlorosilane liquid is sent to the distillation process 6 for recovery. The remaining waste gas enters the pre-column filter 9 for fine filtration, and then undergoes adsorption treatment by the adsorption column 3. Finally, the tail gas is purified by the waste gas scrubbing tower 5a before being discharged.

[0020] This invention employs a three-stage filtration system to precisely intercept impurities at different stages. The pre-filter 7 and post-filter 8 prevent clogging of the compressor and pipelines. The pre-column filter 9 prevents clogging of the Johnson filter at the adsorption column inlet and prevents minute impurities from entering the micropores of the activated carbon in the adsorption column, ensuring long-term stable operation of the adsorption column. Chlorosilane condensation and recovery enable resource reuse, and the combination of adsorption and scrubbing ensures that the exhaust gas meets standards. Overall, this design improves the continuous operating cycle of the equipment, reduces maintenance frequency, saves manpower and operating costs, and balances environmental protection with production efficiency.

[0021] Example 2 The difference between this embodiment and Embodiment 1 is that two pre-filters 7 are connected in parallel. The rest of the structure is the same as in Embodiment 1.

[0022] In this embodiment, two pre-filters (7) are connected in parallel, allowing for online backflushing and silicon powder discharge. When a filter becomes clogged due to impurity accumulation or requires backflushing, the system can be quickly switched to the other filter, ensuring a continuous flow of exhaust gas into the compressor and preventing system downtime. This solves the problem of having to shut down the system for cleaning a single filter, ensuring production continuity. It also provides ample time for online backflushing or offline maintenance, reducing the risk of open-loop operations, minimizing production losses due to downtime, and significantly improving the stability and reliability of the system.

[0023] Example 3 The difference between this embodiment and Embodiment 1 is that in this embodiment, both the pre-machine filter 7 and the post-machine filter 8 are bag filters. The pre-column filter 9 is a ceramic membrane cartridge filter. The rest of the structure is the same as in Embodiment 1.

[0024] In this embodiment, the pre-filter 7 and post-filter 8 adopt a filter bag design. Utilizing the elastic deformation characteristics of the filter bag, the attached silica powder and silica can be effectively detached during automatic backflushing, solving the problem of moisture-laden impurities sticking to the filter element, preventing blockage at the compressor inlet and outlet, and ensuring stable operation of the compression system. The pre-column filter 9 uses a ceramic membrane filter element with a filtration accuracy of 1 micron. With its micron-level high-precision filtration capability, it intercepts fine impurities, prevents blockage of activated carbon micropores, and the filter element material is wear-resistant, significantly extending the operating cycle of the adsorption column 3. The amount of impurities at the inlet of the adsorption column 3 is actually very small, so the solid waste filtered by the pre-column filter 9 can be directly backflushed and discharged. The three filters are designed to adapt to different impurity characteristics, synergistically improving the system's filtration efficiency, reducing equipment maintenance, and lowering operational risks.

[0025] Example 4 The difference between this embodiment and Embodiment 3 is that, in this embodiment, the outlets of the pre-machine filter 7, post-machine filter 8, and pre-column filter 9 are respectively connected to compressed nitrogen pipelines, and the outlets of the filter elements of the pre-machine filter 7, post-machine filter 8, and pre-column filter 9 are respectively equipped with solenoid valves. The backflush outlets of the pre-machine filter 7, post-machine filter 8, and pre-column filter 9 are respectively connected to silicon powder collection tanks 10. The remaining structure is the same as in Embodiment 3.

[0026] In this embodiment, it is common knowledge in the art to install a compressed nitrogen pipeline at the filter element outlet and to install a solenoid valve on the compressed nitrogen pipeline. Even without the accompanying drawings, those skilled in the art can obtain this information through conventional technical means. The filter element outlets of the pre-filter 7, post-filter 8, and pre-column filter 9 are all equipped with solenoid valves, which can control the opening and closing of each passage to achieve automated filter switching. The filter element outlets of the three filters are respectively connected to compressed nitrogen pipelines to provide a high-pressure air source for backflushing. The bottom outlets of the filters are each connected to a silicon powder collection tank 10. The automated switching between filtration and backflushing states is achieved through the solenoid valves: during normal filtration, the filter element outlet solenoid valves of the pre-filter 7, post-filter 8, and pre-column filter 9 are closed; when cleaning is required, the filter element outlet solenoid valves are opened, and compressed nitrogen is backflushed into the filter through the end of the filter element outlet pipeline (nozzle), blowing the silicon powder, silica, and other impurities trapped on the filter element surface into the silicon powder collection tank 10 through the backflushing outlet. To ensure the high efficiency of backflushing cleaning, achieve centralized collection of solid waste, reduce manual operation, avoid leakage and pollution of impurities, and at the same time ensure continuous operation of the system and improve equipment stability.

[0027] Example 5 The difference between this embodiment and embodiment 4 is that, in this embodiment, the outlet of the silicon powder collection tank 10 is connected to the exhaust gas scrubbing tower 5b. The exhaust gas outlet of the pre-filter 7 is equipped with a buffer tank 11a, the exhaust gas outlet of the post-filter 8 is equipped with a buffer tank 11b, and the exhaust gas outlet of the adsorption column 3 is equipped with a buffer tank 11c. The remaining structures are the same as in embodiment 4.

[0028] In this embodiment, the collected acidic solid waste medium is discharged to the waste gas scrubbing tower 25b through a pipeline, realizing the closed-loop neutralization and hydrolysis of the collected acidic solid waste medium.

[0029] Buffer tank 11a and buffer tank 21b are both for stabilizing the process pressure during the backflushing process of the filter at the corresponding position. Buffer tank 31c at the exhaust gas outlet of adsorption column 3 is for stabilizing exhaust gas emissions during the switching of adsorption column 3 and reducing the load impact on the scrubbing tower. It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A compression condensation and recovery system for polycrystalline silicon waste gas, characterized in that: The system includes a waste gas compressor (1), a waste gas cooler (2), and an adsorption column (3) connected in sequence. The waste gas inlet of the waste gas compressor (1) is connected to a waste gas pipeline (4), the waste gas outlet of the adsorption column (3) is connected to a waste gas scrubbing tower (5a), the liquid outlet of the waste gas cooler (2) is connected to a distillation process (6), the waste gas inlet of the waste gas compressor (1) is equipped with an organic pre-filter (7), the waste gas outlet of the waste gas compressor (1) is equipped with an organic post-filter (8), and the waste gas inlet of the adsorption column (3) is equipped with a column pre-filter (9).

2. The polycrystalline silicon waste gas compression condensation and recovery system according to claim 1, characterized in that: Two pre-filters (7) are connected in parallel.

3. The polycrystalline silicon waste gas compression condensation and recovery system according to claim 1, characterized in that: Both the pre-machine filter (7) and the post-machine filter (8) are bag filters.

4. The polycrystalline silicon waste gas compression condensation and recovery system according to claim 1, characterized in that: The column pre-filter (9) is a ceramic membrane filter cartridge.

5. The polycrystalline silicon waste gas compression condensation and recovery system according to any one of claims 3 or 4, characterized in that: The outlets of the filter elements of the pre-machine filter (7), post-machine filter (8) and column filter (9) are respectively connected to compressed nitrogen pipelines, and the outlets of the filter elements of the pre-machine filter (7), post-machine filter (8) and column filter (9) are respectively equipped with solenoid valves.

6. The polycrystalline silicon waste gas compression condensation and recovery system according to claim 5, characterized in that: The bottom outlets of the pre-machine filter (7) and the post-machine filter (8) are respectively connected to silicon powder collection tanks (10).

7. The polycrystalline silicon waste gas compression condensation and recovery system according to claim 6, characterized in that: The outlet of the silicon powder collection tank (10) is connected to the second waste gas scrubbing tower (5b).

8. The polycrystalline silicon waste gas compression condensation and recovery system according to claim 1, characterized in that: The exhaust outlet of the pre-filter (7) is provided with a buffer tank one (11a), the exhaust outlet of the post-filter (8) is provided with a buffer tank two (11b), and the exhaust outlet of the adsorption column (3) is provided with a buffer tank three (11c).

Images