CN218280887U - Combined filtering system applied to polycrystalline silicon slag slurry - Google Patents

Abstract

The utility model discloses a be applied to combination filtration system of polycrystalline silicon sediment thick liquid relates to polycrystalline silicon sediment thick liquid and filters technical field, include: a storage tank for storing slurry material; the first filtering mechanism is connected with an outlet of the storage tank and is used for filtering the slag slurry material for the first time; the second filtering mechanism is connected with the outlet of the first filtering mechanism and is used for carrying out secondary filtering on the slurry materials; and the back washing pipeline is connected with the first filtering mechanism and the second filtering mechanism and is used for introducing high-pressure clean fluid with the same medium to back wash the first filtering mechanism and the second filtering mechanism. Adopt first filtering mechanism and second filtering mechanism two-stage filtering mechanism, filter the sediment thick liquid material, for the one-level filtration that adopts among the prior art, its filter effect is better. Through being provided with back flush pipeline, let in with medium high pressure clean fluid in it, carry out the back flush to first filter equipment and second filter equipment, need not artifical dismantlement and wash, labour saving and time saving.

Description

Combined filtering system applied to polycrystalline silicon slag slurry

Technical Field

The utility model relates to a polycrystalline silicon sediment thick liquid filters technical field, more specifically says and relates to a be applied to polycrystalline silicon sediment thick liquid's combination filtration system.

Background

Silicon tetrachloride is a main byproduct in the production of polysilicon and is also one of main sources of raw materials for producing the polysilicon. With the research and development and popularization of the cold hydrogenation technology, most of the byproduct silicon tetrachloride generated in the production process of the polysilicon is converted into the trichlorosilane raw material. During the conversion process, the silicon tetrachloride reacts with the industrial silicon powder, and the industrial silicon powder contains a certain amount of iron, aluminum and calcium impurities. During the reaction, high-impurity polychlorosilanes, i.e. slurries, are formed. The residue slurry is not considered to have recycling value due to the reasons of high impurity content, high solid content, more high boiling point substances and the like, and is usually subjected to hydrolysis treatment.

In the process of treating the slag slurry, the first step is the filtration of the slag slurry, and how to effectively filter impurities such as silicon powder, precipitated chloride and the like in the slag slurry is important to obtain a clear liquid.

In the prior art, patent publication No. CN210620635U discloses a harmless treatment system for polysilicon slurry, which comprises: the filtering device, the storage device and the mixing device are sequentially communicated through pipelines; the filtering device is used for filtering the slag slurry containing the silicon powder generated in the production process of the polycrystalline silicon to generate filter residues; the storage device is used for collecting filter residues generated by the filtering device and acquiring the mass of the filter residues through the weighing module; and the mixing device is used for processing the filter residue to generate a brick making raw material when the mass of the filter residue in the storage device is greater than or equal to a preset mass threshold value. By adopting the system, the polycrystalline silicon slag slurry can be subjected to harmless treatment, and compared with the existing polycrystalline silicon slag slurry treatment system, the system is more environment-friendly and reduces energy consumption.

In the innocent treatment system disclosed in the above patent, the filtration device is used for filtering impurities such as silicon powder and precipitated chloride in the slurry, and the filtration device is generally a filter. It adopts conventional one-level filtration mode to filter, and the filter effect is not good. When the filter is clogged, the operation is switched to the standby filter operation. And after the blocked filter is qualified by replacement, detaching the flange blind plate at the upper part, manually detaching the filter screen, removing impurities, cleaning the filter screen, and returning the filter screen for equipment. However, manual disassembly is time consuming and labor intensive to remove the impurities.

SUMMERY OF THE UTILITY MODEL

In order to overcome the defect that exists among the above-mentioned prior art, the utility model aims at providing a be applied to combination filtration system of polycrystalline silicon sediment thick liquid to the one-level filtering mode filter effect of solving above-mentioned conventionality is not good, and the manual work is dismantled and is clear away impurity scheduling problem that wastes time and energy.

In order to realize the above purpose, the utility model discloses a technical scheme:

a combination filtration system for use with polysilicon slurry, comprising:

a storage tank for storing slurry material;

the first filtering mechanism is connected with an outlet of the storage tank and is used for filtering the slag slurry material for the first time;

the second filtering mechanism is connected with the outlet of the first filtering mechanism and is used for carrying out secondary filtering on the slurry materials;

and the backwashing pipeline is connected with the first filtering mechanism and the second filtering mechanism and is used for introducing high-pressure clean fluid with the same medium to backwash the first filtering mechanism and the second filtering mechanism.

Furthermore, the first filtering mechanism comprises a first unpicking and washing-free basket filter and a second unpicking and washing-free basket filter which are arranged in parallel, the inlet ends of the first unpicking and washing-free basket filter and the second unpicking and washing-free basket filter are connected with the storage tank through pipelines, and the outlet ends of the first unpicking and washing-free basket filter and the second unpicking and washing-free basket filter are connected with the second filtering mechanism through pipelines.

Furthermore, the second filtering mechanism comprises a first precision filter and a second precision filter which are arranged in parallel, the inlet ends of the first precision filter and the second precision filter are connected with the outlet of the first filtering mechanism through pipelines, and the outlet ends of the first precision filter and the second precision filter are connected to a target clean fluid pipeline through pipelines.

Furthermore, the first non-dismantling and washing basket filter, the second non-dismantling and washing basket filter, the first precision filter and the second precision filter are all connected to an impurity discharge pipeline through pipelines.

Furthermore, the non-dismantling and washing basket filter comprises a shell, a basket filter screen, an upper cover and a back flushing pipe;

the water inlet and the water outlet are respectively arranged at the left end and the right end of the upper part of the shell, the drain outlet is arranged at the bottom end of the shell, the basket type filter screen is arranged in the shell, the top end of the shell is provided with an opening, and the upper cover is covered at the opening at the top end;

the back flushing pipe is installed on the upper cover, the top end of the back flushing pipe extends out of the upper cover, the back flushing pipe is vertically inserted into the basket type filter net downwards, and a plurality of flushing holes are formed in the side wall of the inserted part of the back flushing pipe along the circumferential direction and the axial direction of the inserted part of the back flushing pipe.

Further, the back flushing pipe comprises an upper connecting pipe, a middle first connecting piece and a lower flushing pipe;

the connecting pipe is welded on the upper cover, and the top end of the connecting pipe extends out of the upper cover and is provided with a second connecting piece; the first connecting piece is positioned between the connecting pipe and the flushing pipe; the flushing pipe is positioned in the basket type filter screen, and a plurality of flushing holes are formed in the side wall of the flushing pipe along the circumferential direction and the axial direction of the flushing pipe.

Further, the first connecting piece is a connecting flange, and the flushing pipe is fixedly installed on the connecting flange.

Further, the first connecting piece is a sealing bearing inside the bottom end of the connecting pipe, and the flushing pipe is installed in the sealing bearing.

Further, the flushing hole is a straight inclined hole or a conical round hole.

Further, the precision filter comprises a pressure container shell and a high-precision filter element;

the high-precision filter element is installed in the pressure vessel shell, an inlet pipe is arranged on the side wall of the lower portion of the pressure vessel shell, a drain pipe is arranged at the bottom end of the pressure vessel shell, and an outlet pipe is arranged at the top end of the pressure vessel shell.

The utility model has the advantages that:

the utility model provides a combination filtration system adopts first filtering mechanism and second filtering mechanism two-stage filtering mechanism, filters the sediment thick liquid material, and for the one-level filtration of adopting among the prior art, its filter effect is better.

The utility model provides a combination filtration system, through being provided with the back flush pipeline, let in it with medium high pressure clean fluid, carry out the back flush to first filter mechanism and second filter mechanism, need not artifical the dismantlement and washs labour saving and time saving.

The utility model provides a combined filtering system, the first filtering mechanism and the second filtering mechanism are both provided with two filters, the two filters can carry out filtering work independently or simultaneously, and can be switched at any time and flexibly applied; when one of the filters is blocked, the back washing pipeline is adopted to wash the filter, and the other filter is utilized to filter the slurry materials, so that the operation is simple, the shutdown operation is not needed, and the time and the labor are saved.

The utility model provides a combination filtration system, in exempting from to unpick and wash basket filter, the backwash pipe is installed and is covered at the upper cover, the upper cover is stretched out on its top, the downward vertical basket filter screen that inserts of backwash pipe, and all seted up a plurality of flushing ports on its circumference and axial on the lateral wall of backwash pipe inserted part, utilize a plurality of flushing ports to wash the basket filter screen of jam, can wash each region of lateral wall to the basket filter screen, it is regional all-round to wash, wash effectually, the effective washing of the impurity on the filter screen has been realized.

Drawings

FIG. 1 is a schematic view of the combined filtration system of the present invention;

FIG. 2 is a schematic view of the basket filter of the present invention;

FIG. 3 is a top view of the non-dismantling basket filter of the present invention;

FIG. 4 is an enlarged view of the portion A in FIG. 2 when the flushing hole of the present invention is a straight inclined hole;

FIG. 5 is an enlarged view of the portion A in FIG. 2 when the flushing hole of the present invention is a conical circular hole;

FIG. 6 is a schematic view of a precision filter according to the present invention;

reference numerals are as follows:

100. a storage tank; 200. a first filter mechanism; 201. a first unpicking and washing-free basket filter; 202. a second non-dismantling basket filter; 300. a second filtering mechanism; 301. a first precision filter; 302. a second precision filter; 303. a pressure vessel shell; 304. a high-precision filter element; 305. an inlet pipe; 306. a blow-off pipe; 307. an outlet pipe; 400. back flushing the pipeline; 500. a target clean fluid conduit; 600. an impurity discharge pipe;

1. a housing; 2. basket type filtering net; 3. an upper cover; 4. a backwash pipe; 41. a connecting pipe; 42. a first connecting member; 43. a flush tube; 44. a second connecting member; 5. a water inlet; 6. a water outlet; 7. a sewage draining outlet; 8. and (6) flushing the hole.

Detailed Description

The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below with reference to the embodiments and the accompanying drawings, so as to fully understand the objects, the features, and the effects of the present invention.

Example 1

A combined filtration system for polysilicon residue slurry, as shown in fig. 1, comprising:

a storage tank 100 for storing slurry material;

the first filtering mechanism 200 is connected with an outlet of the storage tank 101 and is used for filtering the slag slurry material for the first time;

the second filtering mechanism 300 is connected with the outlet of the first filtering mechanism 200 and is used for carrying out secondary filtering on the slurry materials;

and a back washing pipeline 400 connected with the first filtering mechanism 200 and the second filtering mechanism 300 and used for introducing high-pressure clean fluid with the same medium to back wash the first filtering mechanism 200 and the second filtering mechanism 300.

In this embodiment, the storage tank 100 is used for storing slag slurry materials to be filtered in polysilicon production, the first filtering mechanism 200 is used for performing primary filtering on the slag slurry materials, the second filtering mechanism 300 is used for performing secondary filtering on the slag slurry materials, and the backwash pipeline 400 is used for introducing a high-pressure clean fluid of the same medium to backwash the first filtering mechanism 200 and the second filtering mechanism 300.

This embodiment adopts first filtering mechanism 200 and 300 two-stage filtering mechanism of second filtering mechanism, filters the sediment thick liquid material, and for the one-level filtration that adopts among the prior art, its filter effect is better. Through the arrangement of the back washing pipeline 400, the same-medium high-pressure clean fluid is introduced into the back washing pipeline to back wash the first filtering mechanism 200 and the second filtering mechanism 300, manual disassembly is not needed for cleaning, and time and labor are saved.

Example 2

In this embodiment, as further explained based on embodiment 1, as shown in fig. 1, the first filtering mechanism 200 includes a first non-dismantling and washing basket filter 201 and a second non-dismantling and washing basket filter 202 which are arranged in parallel, inlet ends of the first non-dismantling and washing basket filter 201 and the second non-dismantling and washing basket filter 202 are both connected to the storage tank 100 through a pipeline, and outlet ends of the first non-dismantling and washing basket filter 201 and the second non-dismantling and washing basket filter 202 are both connected to the second filtering mechanism 300 through a pipeline.

The second filtering mechanism 300 includes a first precision filter 301 and a second precision filter 302 which are arranged in parallel, the inlet ends of the first precision filter 301 and the second precision filter 302 are connected with the outlet of the first filtering mechanism 200 through pipelines, the outlet ends of the first precision filter 301 and the second precision filter 302 are connected to a target clean fluid pipeline 500 through pipelines, and the filtered clean fluids are collected together and are conveyed to the subsequent processes through the target clean fluid pipeline 500.

The first and second non-dismantling and washing basket filters 201 and 202, the first and second fine filters 301 and 302 are connected to an impurity discharge pipe 600 through pipes, collect impurities of the respective filters together, and discharge the collected impurities through the impurity discharge pipe 600.

In this embodiment, the first filtering mechanism 200 is provided with two first unpicking and washing-free basket filters 201 and two second unpicking and washing-free basket filters 202 which are connected in parallel, and the second filtering mechanism 300 is provided with two first precise filters 301 and two second precise filters 302 which are connected in parallel, that is, the first filtering mechanism 200 and the second filtering mechanism 300 are both provided with two filters with the same type, and the two filters can be used for filtering independently or simultaneously; when one of the filters is blocked, the backwashing pipeline 400 is adopted to flush the filter, and the other filter is utilized to filter the slurry materials, so that the operation is simple, the shutdown operation is not needed, and the time and the labor are saved.

The mesh number of the filter screen of the non-unpicking and washing basket filter is set to be 60-80 meshes, and the non-unpicking and washing basket filter mainly comprises a conventional basket filter and a backwashing component. The precise filter is a metal sintered filter or a ceramic filter, the filtering precision is 5-1 mu m, the purpose of fine filtering of the slag liquid is achieved, and the precise filter mainly comprises a pressure container shell and a high-precision filter element.

Example 3

This embodiment is further illustrated on the basis of example 2. As shown in fig. 2-5, the non-dismantling and washing basket filter comprises a housing 1, a basket filter net 2, an upper cover 3 and a back-flushing pipe 4.

The left end and the right end of the upper part of the shell 1 are respectively provided with a water inlet 5 and a water outlet 6, the bottom end of the shell 1 is provided with a sewage outlet 7, the basket type filter screen 2 is arranged inside the shell 1, the top end of the shell 1 is provided with an opening, and the upper cover 3 is covered at the opening at the top end;

the back flushing pipe 4 is arranged on the upper cover 3, the top end of the back flushing pipe extends out of the upper cover 3, the back flushing pipe 4 is vertically inserted into the basket type filter screen 2 downwards, and a plurality of flushing holes 8 are formed in the side wall of the inserted part of the back flushing pipe 4 along the circumferential direction and the axial direction of the side wall.

In this embodiment, the water inlet 5 is used for entering the slurry to be filtered, the slurry to be filtered enters the basket filter and is then filtered by the basket filter screen 2, the filtered liquid is discharged through the water outlet 6, and the sewage outlet 7 is used for discharging sewage. Through being provided with backwash pipe 4, when basket filter screen 2 in the filter blockked up, utilize backwash pipe 4 to wash it, need not artifical the dismantlement and wash labour saving and time saving.

During back flushing, flushing liquid enters the back flushing pipe 4 through the inlet end of the back flushing pipe 4, is sprayed out through the plurality of flushing holes 8, and flushes the basket type filter screen 2 which is blocked, and because the plurality of flushing holes 8 are formed in the side wall of the back flushing pipe 4 along the circumferential direction and the axial direction of the side wall, all areas of the side wall of the basket type filter screen can be flushed, the flushing areas are all-directional, the flushing effect is good, and effective flushing of impurities on the filter screen is realized. After the washing liquid is washed, the mixed liquid mixed with the washing liquid and the washing slag flows upwards in the basket filter screen 2 and is discharged out of the basket filter from the water inlet 5. When the back washing process is blocked, the sewage draining outlet 7 is opened, sewage is drained from the sewage draining outlet 7, and then the basket type filter screen 2 is detached for cleaning.

In the implementation, the upper cover 3 is a blind flange cover, a hole is formed in the upper surface of the blind flange cover, a backwash pipe is connected, and the two upper surfaces of the pipeline, which are in contact with the blind flange cover, are all fully welded to form a circular fillet weld. The tubing extends 100mm above the upper surface of the blind flange cover (DN 25 tubing) and extends higher if it is a larger diameter tubing. And a flange matched with the pipeline is welded at the upper end of the pipeline. The height of the pipeline extending out of the upper surface of the blind flange cover is determined by the size of the mounting bolt of the flange matched with the pipeline.

Example 4

This embodiment is further illustrated on the basis of embodiment 3, as shown in fig. 2 and 3, the backwash pipe 4 comprises an upper connecting pipe 41, a middle first connecting member 42 and a lower flushing pipe 43; the connecting pipe 41 is welded on the upper cover 3, the top end of the connecting pipe extends out of the upper cover 3 and is provided with a second connecting piece 44; the first connector 42 is located between the connection pipe 41 and the flushing pipe 43; the flushing pipe 43 is positioned in the basket type filter screen 2, and a plurality of flushing holes 8 are formed in the side wall of the flushing pipe 43 along the circumferential direction and the axial direction of the flushing pipe.

The first connecting piece 42 is a connecting flange on which the flushing pipe 43 is fixedly mounted. The first connecting piece 42 may also be a sealed bearing inside the bottom end of the connecting tube 41, in which the flushing tube 43 is mounted.

In this embodiment, the lower end of the backwash pipe 4 has two connection modes. One mode is that a flange matched with the pipeline is welded at the lower end of the pipeline, and a clear liquid washing part matched with the flange is arranged at the lower end of the flange. The other mode is that a sealing bearing is arranged at the inner end of the pipeline, a clear liquid leaching component is connected below the bearing, the rotary leaching component is made, and the washing effect of the filter screen is better.

As shown in fig. 4 or 5, the flushing hole 8 is a straight inclined hole or a tapered circular hole. When the filter screen is a straight inclined hole, fluid is sprayed out of the straight inclined hole to form an inclined fan shape, the filter screen is washed more widely and more comprehensively, and the filter screen is more suitable for impurities which are easy to wash; when the filter screen is a conical round hole, after fluid is sprayed out of the conical round hole, the fluid is sprayed on the filter screen obliquely upwards, the washing strength is more concentrated, and the filter screen is more suitable for impurities which are not easy to wash away.

Example 5

This embodiment is further explained on the basis of embodiment 4, and as shown in fig. 6, the precision filter includes a pressure vessel housing 303 and a high-precision filter element 304; the high-precision filter element 304 is arranged in a pressure container shell 303, an inlet pipe 305 is arranged on the side wall of the lower part of the pressure container shell 303, a sewage discharge pipe 306 is arranged at the bottom end, and an outlet pipe 307 is arranged at the top end.

In this embodiment, the slurry to be filtered enters from the inlet pipe 305, is filtered by the high-precision filter element 304, and is discharged through the outlet pipe 307, and meanwhile, the impurities are discharged through the sewage discharge pipe 306.

In this embodiment, each pipeline is provided with a valve to control the on-off of each pipeline.

For better understanding, the utility model discloses, following do a complete description to the theory of operation of the utility model:

in use, as shown in figure 1, slurry material from the tank 100, which contains a quantity of impurities, first enters the first filter mechanism 200.

In the first filtering mechanism 200, the material enters the first non-dismantling and washing basket filter 201 or the second non-dismantling and washing basket filter 202 through the 3# valve or the 8# valve, and after the non-dismantling and washing basket filter filters some coarse particle impurities, the material enters the second filtering mechanism 300 through the 4# valve or the 9# valve.

In the second filtering mechanism 300, the material enters the first precision filter 301 or the second precision filter 302 through the 13# valve or the 17# valve, the precision filter filters out the remaining fine particle impurities, and then the material is sent to the target clean fluid pipeline 500 through the 14# valve or the 18# valve, and the clean fluid is sent to the next process through the target clean fluid pipeline 500.

When the first non-dismantling and washing basket filter 201 is blocked, the second non-dismantling and washing basket filter 202 is operated to filter slurry materials, and the first non-dismantling and washing basket filter 201 is backwashed. Specifically, the same-medium high-pressure cleaning fluid is introduced, passes through the 11# valve and then enters the first non-dismantling and washing basket filter 201 through the 1# valve, and impurities on the filter screen are backwashed through the backwashing component. Impurities after back flushing pass through a No. 2 valve together with the fluid, enter the impurity discharge pipeline 600 and are discharged out of the system. After a period of back flushing, sampling is confirmed, and after the product is qualified, the back flushing is finished, and valves 1#, 2# and 11# are closed. The first non-dismantling basket filter 201 is ready for use.

When the second non-dismantling basket filter 202 is clogged, the back-washing principle is similar to that of the first non-dismantling basket filter 201, and will not be described again.

When the first precision filter 301 is clogged, the second precision filter 302 is operated to filter the slurry material while the first precision filter 301 is backwashed. Specifically, the same-medium high-pressure cleaning fluid is introduced, and the same-medium high-pressure cleaning fluid enters the first precision filter 301 through the # 12 valve and then through the # 15 valve, and is back-flushed from the inside of the filter element to the outside of the filter element. Impurities after back flushing pass through a No. 16 valve along with the fluid, enter an impurity discharge pipeline 600 and are discharged out of the system. After a period of back flushing, sampling is confirmed, and after the product is qualified, the back flushing is finished, and valves 12#, 15# and 16# are closed. The first fine filter 301 is ready for use.

The backwash principle is similar to that of the first fine filter 301 when the second fine filter 302 is clogged, and will not be described again.

During operation, the first non-dismantling basket filter 201 and the second non-dismantling basket filter 202 can be mutually standby and switched. The first fine filter 301 and the second fine filter 302 can be switched to each other as well as to be used as backup. The first non-dismantling and washing basket filter 201, the second non-dismantling and washing basket filter 202, the first precision filter 301 and the second precision filter 302 can be combined at will, and the production and operation flexibility is better.

After the combined filtering system of the embodiment is implemented on a certain polycrystalline silicon production line, 99% of solid impurities in a slurry system can be filtered, and the overhauling frequency is low.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and the equivalents or substitutions are included in the scope of the present invention defined by the claims.

Claims (10)

1. A combined filter system applied to polysilicon slag slurry is characterized by comprising:

a storage tank (100) for storing slurry material;

the first filtering mechanism (200) is connected with an outlet of the storage tank (100) and is used for filtering the slag slurry material for the first time;

the second filtering mechanism (300) is connected with the outlet of the first filtering mechanism (200) and is used for carrying out secondary filtering on the slurry materials;

and the back washing pipeline (400) is connected with the first filtering mechanism (200) and the second filtering mechanism (300) and is used for introducing high-pressure clean fluid with the same medium to back wash the first filtering mechanism (200) and the second filtering mechanism (300).

2. The combination filtration system of claim 1, wherein the first filtration mechanism (200) comprises a first non-dismantling basket filter (201) and a second non-dismantling basket filter (202) arranged in parallel, wherein the inlet ends of the first non-dismantling basket filter (201) and the second non-dismantling basket filter (202) are connected with the storage tank (100) through pipelines, and the outlet ends of the first non-dismantling basket filter and the second non-dismantling basket filter are connected with the second filtration mechanism (300) through pipelines.

3. The combined filtration system of claim 2, wherein the second filtration mechanism (300) comprises a first precision filter (301) and a second precision filter (302) arranged in parallel, wherein the inlet ends of the first precision filter (301) and the second precision filter (302) are connected with the outlet end of the first filtration mechanism (200) through a pipeline, and the outlet ends of the first precision filter and the second precision filter are connected with the target clean fluid pipeline (500) through a pipeline.

4. A combined filtration system according to claim 3, wherein the first non-dismantling basket filter (201), the second non-dismantling basket filter (202), the first fine filter (301) and the second fine filter (302) are connected to the impurity discharge pipe (600) by pipes.

5. A combined filter system according to claim 2, characterised in that the non-dismantling basket filter comprises a housing (1), a basket filter (2), an upper cover (3) and a backwash pipe (4);

the water inlet (5) and the water outlet (6) are respectively arranged at the left end and the right end of the upper part of the shell (1), the sewage discharge outlet (7) is arranged at the bottom end of the shell (1), the basket type filter screen (2) is installed inside the shell (1), the top end of the shell (1) is provided with an opening, and the upper cover (3) is covered at the opening at the top end;

the backwashing pipe (4) is installed on the upper cover (3), the top end of the backwashing pipe extends out of the upper cover (3), the backwashing pipe (4) is vertically inserted into the basket type filter screen (2) downwards, and a plurality of flushing holes (8) are formed in the side wall of the inserting part of the backwashing pipe (4) along the circumferential direction and the axial direction of the side wall.

6. Combined filter system according to claim 5, characterised in that the backwash pipe (4) comprises an upper connection pipe (41), a middle first connection piece (42) and a lower flushing pipe (43);

the connecting pipe (41) is welded on the upper cover (3), and the top end of the connecting pipe extends out of the upper cover (3) and is provided with a second connecting piece (44); the first connection piece (42) is located between the connection pipe (41) and the flushing pipe (43); the flushing pipe (43) is positioned in the basket type filter screen (2), and a plurality of flushing holes (8) are formed in the side wall of the flushing pipe (43) along the circumferential direction and the axial direction of the flushing pipe.

7. Combined filter system according to claim 6, characterised in that the first connecting piece (42) is a connecting flange on which the flushing pipe (43) is fixedly mounted.

8. Combined filter system according to claim 6, where the first connection piece (42) is a sealed bearing inside the bottom end of the connection tube (41), and where the flushing tube (43) is mounted.

9. Combined filter system according to claim 5, characterised in that the flushing holes (8) are straight inclined holes or conical circular holes.

10. A combined filter system according to claim 3, characterised in that the precision filter comprises a pressure vessel housing (303) and a high precision filter cartridge (304);

the high-precision filter element (304) is arranged in the pressure container shell (303), an inlet pipe (305) is arranged on the side wall of the lower part of the pressure container shell (303), a sewage discharge pipe (306) is arranged at the bottom end of the pressure container shell, and an outlet pipe (307) is arranged at the top end of the pressure container shell.

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