Deslagging system of cold hydrogenation washing tower

Abstract

The utility model discloses a slag discharge system of a cold hydrogenation washing tower, which comprises a cryogenic stirring tank and a filter, the cryogenic stirring tank is connected with a slag outlet at the bottom of the cold hydrogenation washing tower through a pipeline, the filter comprises a filter cylinder and a trough which are arranged up and down, and a filter element is sleeved in the filter cylinder. A feed port communicated with the inner cavity of the filter element and a filtrate outlet communicated with the outer cavity of the filter element are respectively formed in the filter cylinder, the feed port is connected with a cryogenic stirring tank, the filtrate outlet is connected with a slag slurry treatment device, the top of the trough is communicated with the inner cavity of the filter element, and a slag discharge port is formed in the bottom of the trough. According to the utility model, the filter with a specific structure is matched with the cryogenic stirring tank, so that metal chloride solids separated out from slag slurry materials can be filtered and quickly discharged, and meanwhile, the blockage of the pipeline caused by the metal chloride separated out and attached to the pipeline when the air temperature is reduced in winter can be avoided.

Description

Technical Field

[0001] This utility model belongs to the field of polycrystalline silicon production technology, specifically, it is a cold hydrogenation washing tower slag discharge system. Background Technology

[0002] In the polysilicon production process, the cold hydrogenation scrubbing tower cools the high-temperature, high-pressure process gas containing hydrogen, chlorosilanes, metal chlorides, and a small amount of silicon powder, while simultaneously washing away the carried silicon powder and the metal chlorides precipitated due to the cooling process. See also Figure 1 As shown, the high-temperature and high-pressure process gas containing hydrogen, chlorosilane, metal chlorides, and a small amount of silicon powder, after being filtered by the filter, enters the cold hydrogenation scrubbing tower for wet dust removal. The clean saturated process gas exiting from the top of the tower is condensed through multiple stages to obtain the product liquid. The concentrated metal chlorides and other impurities accumulate at the bottom of the scrubbing tower and are discharged from the bottom of the scrubbing tower to the slag buffer tank through intermittent slag discharge. The slag buffer tank is equipped with jacketed cooling water, and the slurry is initially cooled before being sent to the subsequent slurry treatment system.

[0003] Currently, the temperature at the bottom of the washing tower is typically between 140 and 165°C. Metal chlorides have high solubility in chlorosilanes, dissolving almost entirely with a small portion remaining in a free solid state. The slag discharged from the bottom of the washing tower into the slurry buffer tank requires initial cooling via circulating water. However, this cooling process causes the dissolved metal chlorides in the slurry to gradually precipitate. These precipitated chlorides easily adhere to the walls and pipe openings of the slurry buffer tank, gradually accumulating until the bottom pipe opening is blocked. This prevents the slag from being discharged into the slurry treatment system, affecting the stable operation of the cold hydrogenation unit. Especially in colder weather, such as winter, the precipitated metal chlorides can also adhere to the pipes, causing blockages in the slag discharge pipes of the slurry buffer tank, making it difficult to discharge slag into the slurry treatment system normally.

[0004] In the prior art, Chinese patent CN218572852U reports a cold hydrogenation slurry treatment system. This slurry treatment system includes at least two treatment units. The first-stage treatment unit includes a stirred cooling tank, a low-temperature buffer tank, and a filter connected in sequence to the feed port of a washing tower. During production, the slurry liquid containing chlorosilane polymers, partial chlorosilanes, and metal chlorides, generated from the washing of the slurry stream in the washing tower by chlorosilane cleaning liquid, enters the first-stage treatment unit from the feed port. It is then processed sequentially through the stirred cooling tank, the low-temperature buffer tank, and the filter (a sintered metal filter with a filtration accuracy of 10-100 μm). Finally, the gas phase obtained after filtration is directly sent to a distillation tower for distillation. The material retained by the filter is sent to an evaporator for evaporation.

[0005] Since the filters used in this slurry treatment system are precision filters, a coarse filter is usually installed upstream of the precision filter to extend its service life and achieve better filtration results. Meanwhile, in the polysilicon production process, basket filters are typically used. However, when using basket filters, removing the material trapped by the filter element requires manually opening the filter top cover, removing the filter element, and then taking out the trapped material for the next process. This not only increases labor intensity but also poses risks associated with manual operation. Utility Model Content

[0006] The purpose of this invention is to provide a cold hydrogenation washing tower slag discharge system. By using a filter with a specific structure in conjunction with a cryogenic mixing tank, it can filter and quickly discharge the metal chloride solids precipitated in the slurry material. At the same time, it can avoid the blockage caused by metal chlorides adhering to the pipeline due to the low temperature in winter.

[0007] This utility model is achieved through the following technical solution: a slag discharge system for a cold hydrogenation washing tower, comprising a cryogenic stirring tank and a filter. The cryogenic stirring tank is connected to the slag outlet at the bottom of the cold hydrogenation washing tower via a pipeline. The filter comprises a filter cylinder and a material trough arranged vertically. A filter element is fitted inside the filter cylinder. The filter cylinder is provided with an inlet communicating with the inner chamber of the filter element and a filtrate outlet communicating with the outer chamber of the filter element. The inlet is connected to the cryogenic stirring tank, and the filtrate outlet is connected to a slurry treatment device. The top of the material trough is connected to the inner chamber of the filter element, and the bottom of the material trough is provided with a slag discharge port.

[0008] The filter cylinder is provided with a nitrogen inlet that connects to the inner chamber of the filter element. The filter cylinder is vertically arranged, and both the feed inlet and the nitrogen inlet are located at the top of the filter cylinder.

[0009] The filter cylinder is provided with a replacement gas outlet that connects to the outer chamber of the filter element.

[0010] The number of filters is at least two sets, and each set of filters is connected in parallel.

[0011] A circulating water cooling tank is provided between the cold hydrogenation washing tower and the cryogenic stirring tank, and the cryogenic stirring tank is connected to the slag outlet at the bottom of the cold hydrogenation washing tower via the circulating water cooling tank.

[0012] The cooling medium of the cryogenic mixing tank is Freon.

[0013] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0014] (1) The use of a cryogenic mixing tank in this utility model can make the metal chlorides in the slurry material precipitate out as much as possible and suspend them in the material under stirring, avoiding them from adhering to the inner wall of the tank or the pipe opening, etc. At the same time, it can also avoid the blockage of the slag discharge pipe caused by the continued precipitation of solid metal chlorides in the subsequent pipeline due to the low temperature of the outside.

[0015] (2) This utility model uses a filter to filter and separate the metal chloride solids precipitated from the slurry material. The filter consists of a filter cylinder and a material tank. The slurry material is filtered under negative pressure by the filter element in the filter cylinder. The metal chloride solids obtained by filtration fall into the material tank below. After filtration, the valve of the slag discharge port can be opened to discharge the metal chloride solids. In actual production, multiple sets of filters can be set up in parallel for backup, so as to realize the continuous treatment of the slurry material at the bottom of the cold hydrogenation washing tower and send it to the slurry treatment device, improve the equipment operating efficiency, and reduce the intensity of manual operation.

[0016] (3) When cooling the slurry material (temperature about 140 to 160°C) at the bottom of the cold hydrogenation washing tower, the present invention first uses circulating water as the cooling medium to stir and cool to 15 to 30°C, and then uses Freon as the cooling medium to stir and cool to -30 to -5°C. This can reduce the temperature difference change of the slurry material during the cooling process, reduce the design requirements of the cooling equipment, and achieve control of equipment costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the slag discharge process of an existing cold hydrogenation scrubbing tower.

[0018] Figure 2 This is a schematic diagram of the structure of this utility model.

[0019] Among them, 1—cryogenic mixing tank, 2—slag outlet, 3—filter cylinder, 4—material trough, 5—filter element, 6—feed inlet, 7—filtrate outlet, 8—slag discharge outlet, 9—nitrogen inlet, 10—displacement gas outlet, 11—circulating water cooling tank. Detailed Implementation

[0020] 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.

[0021] Example 1:

[0022] This embodiment aims to address the problem that during the cooling and subsequent delivery of slurry from a cold hydrogenation washing tower to a slurry treatment unit, precipitated metal chloride solids tend to accumulate in the pipes, causing blockages and preventing the discharge of slag concentrate to the slurry treatment unit, thus affecting the stable operation of the cold hydrogenation unit. To address this, this embodiment provides a slag discharge system for a cold hydrogenation washing tower. This system comprises a cryogenic stirring tank 1 and a specially structured filter. Firstly, the cryogenic stirring tank 1 allows for the maximum precipitation of metal chlorides from the slurry, suspending them in the material under stirring conditions. This prevents further precipitation of metal chloride solids in subsequent pipes due to low ambient temperatures, thus avoiding blockages in the slag discharge pipes. Secondly, the specially structured filter separates and discharges the metal chloride solids from the slurry, eliminating the need for manual disassembly of the filter top cover and removal of the filter element before discarding the trapped slag (metal chloride solids) using existing basket filters. This simplifies the filter operation and reduces manual labor intensity.

[0023] The equipment structure and layout in this embodiment are as follows: Figure 2 As shown, the slag outlet 2 at the bottom of the cold hydrogenation washing tower is connected to the circulating water cooling tank 11 and the cryogenic stirring tank 1 in sequence through pipelines, so as to realize the two-stage stirring and cooling of the slurry material discharged from the bottom of the cold hydrogenation washing tower, so that the metal chlorides in it precipitate out, and then the cryogenic slurry material is sent to the filter through pipelines.

[0024] The filter consists of a vertically arranged filter cylinder 3 and a material tank 4. The filter cylinder 3 is vertically positioned, and a filter element 5 is installed inside it, dividing the filter cylinder 3 into two inner and outer chambers. The filter cylinder 3 is equipped with a feed inlet 6 and a nitrogen inlet 9 located at the top, and a filtrate outlet 7 and a displacement gas outlet 10 located on the side wall of the filter cylinder 3. Figure 2 As shown, electric valves are installed on the connecting pipelines of feed inlet 6, nitrogen inlet 9, filtrate outlet 7, and displacement gas outlet 10, respectively. Feed inlet 6 and nitrogen inlet 9 are connected to the inner chamber of filter element 5, and filtrate outlet 7 and displacement gas outlet 10 are connected to the outer chamber of filter element 5, respectively. The top of the material tank 4 is connected to the inner chamber of filter element 5, and the bottom of the material tank 4 is provided with a slag discharge port 8.

[0025] In one possible embodiment, a valve can be directly connected to the bottom of the filter cylinder 3. One end of the valve communicates with the inner chamber of the filter element 5 to form a material trough 4 for collecting slag. The slag discharge port 8 is correspondingly located at the other end of the valve. Figure 2The valve section shown. In use, the slurry material is fed into the filter through the feed inlet 6 to remove and separate the precipitated metal chloride solids. The separated liquid is sent to the slurry treatment device through the filtrate outlet 7. The intercepted impurities (metal chloride solids, i.e., slag) are collected in the feed tank 4 and the filter element 5 above the feed tank 4. When the filter element 5 is full, the electric valve of the feed inlet 6 is closed. After nitrogen purging is qualified (during nitrogen purging, the electric valve of the feed inlet 6 is closed, and the electric valves of the purging gas outlet 10 and the nitrogen inlet 9 are opened in sequence. After nitrogen purging is completed, the electric valves of the nitrogen inlet 9 and the purging gas outlet 10 are closed in sequence), the valve is opened directly to discharge the metal chloride solids from the bottom slag outlet 8 and bag them for treatment. Alternatively, the bottom valve (or slag outlet 8) can be directly connected to the hydrolysis tank, and the metal chloride solids can be sent directly to the hydrolysis tank for hydrolysis treatment by opening the bottom valve. Alternatively, nitrogen purging can be skipped, and the metal chloride solids can be directly sent to the hydrolysis tank for hydrolysis treatment by opening the bottom valve. It effectively avoids the labor and operational risks of manual open-loop operations, and realizes closed-loop, online slag discharge operation.

[0026] In one possible embodiment, at least two sets of filters can be set in the system, with each set of filters connected in parallel. By controlling and switching electric valves, one set of filters can discharge slag while the other set of filters simultaneously performs filtration, thus realizing continuous operation and control of slurry treatment in the cold hydrogenation system.

[0027] In one possible embodiment, a precision filter can be added to the system. The filter in this embodiment can perform coarse filtration of the slurry material. The filter element 5 is 100-200μm. The filtered slurry material is then sent to the precision filter (0.3-1μm) to improve the filtration accuracy and efficiency of solid impurities (metal chloride solids) in the slurry material.

[0028] The detailed process flow of this embodiment is as follows:

[0029] In the cold hydrogenation system, the filtered high-temperature, high-pressure process gas containing hydrogen, chlorosilanes, metal chlorides, and a small amount of silicon powder enters the cold hydrogenation scrubbing tower (wet dust removal scrubbing tower). The concentrated metal chlorides and other impurities accumulate at the bottom of the cold hydrogenation scrubbing tower. The impurities at the bottom of the scrubbing tower are discharged intermittently into the circulating water cooling tank 11. The circulating water cooling tank 11 is equipped with a jacketed cooling water system and a stirrer. The temperature at the bottom of the cold hydrogenation scrubbing tower is controlled between 140 and 165°C. At this temperature, the metal chlorides in the slurry have a high solubility in chlorosilanes and are mostly dissolved, with a small portion remaining in a free solid state. The slurry discharged into the circulating water cooling tank 11 is cooled by circulating water (approximately 30-40°C), causing the dissolved metal chlorides to gradually precipitate. Because the circulating water cooling tank 11 is equipped with a stirrer, the metal chlorides cannot accumulate on the buffer tank wall during precipitation and remain in a free solid state in the chlorosilane solution, greatly reducing the risk of clogging in the circulating water cooling tank 11. Simultaneously, a cryogenic mixing tank 1 is installed. After initial cooling by the front-end circulating water, the water is sent to the next stage cryogenic mixing tank 1. The temperature of the second-stage cryogenic tank must be lower than the lowest annual temperature in the region (approximately -5 to 0℃). If Freon is used as the cooling medium, the temperature of the cryogenic mixing tank 1 can be controlled at -30 to -5℃. This ensures that the chlorosilane liquid containing metal chlorides sent from the cryogenic mixing tank 1 will not precipitate further metal chlorides due to the temperature drop, thus preventing blockage of the pipeline to the slurry treatment device (at the same time, attention should be paid to the insulation of the pipeline from the second-stage cryogenic tank to the slurry system). A filter is installed at the bottom of the cryogenic mixing tank 1 on the pipeline to the slurry treatment device to intercept all precipitated solid free metal chlorides, preventing them from affecting the slurry treatment system. The filter uses bottomless filter cartridges 5, with multiple filters used in parallel. Once one filter is full, the flow switches to other filters. After the full filter is purged with nitrogen and deemed qualified, the metal chlorides inside can be discharged from the bottom of the filter and bagged for disposal.

[0030] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A cold hydrogenation wash column de-sludging system characterized by: The filter comprises a filter cylinder (3) and a tank (4) arranged in sequence, the filter cylinder (3) is sleeved with a filter core (5), the filter cylinder (3) is respectively provided with a feed inlet (6) and a filtrate outlet (7), the feed inlet (6) is connected with the deep cold stirring tank (1), the filtrate outlet (7) is connected with a slurry treatment device, the tank (4) is communicated with the inner side chamber of the filter core (5), and the tank (4) is provided with a slag discharge port (8) at the bottom.

2. The cold hydrogenation scrubber discharge system of claim 1, wherein: The filter cylinder (3) is vertically arranged, and the feed inlet (6) and the nitrogen inlet (9) are arranged on the top of the filter cylinder (3).

3. The cold hydrogenation scrubber discharge system of claim 2, wherein: The filter cylinder (3) is provided with a displacement gas outlet (10) communicated with the outer side chamber of the filter core (5).

4. The cold hydrogenation scrubber discharge system according to any one of claims 1 to 3, characterized in that: The number of the filters is at least two groups, and each group of filters is arranged in parallel.

5. The cold hydrogenation wash column discharge system of claim 1, wherein: A circulating water cooling tank (11) is arranged between the cold hydrogenation washing tower and the deep cold stirring tank (1), and the deep cold stirring tank (1) is connected with the slag discharge port (2) at the bottom of the cold hydrogenation washing tower through the circulating water cooling tank (11).

6. The cold hydrogenation wash column decanter system of claim 1, wherein: The cooling medium of the deep cold stirring tank (1) is freon.

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