Air-floating type multi-disc direct-cleaning filter and using method thereof
Technical Field
The invention relates to the field of filtering industrial sewage, papermaking white water and the like, in particular to an air-floating type multi-disc direct-cleaning filter and a use method thereof.
Background
White water generated in the traditional papermaking process contains a large amount of fine fibers and chemical residues, enterprises spend a large amount of funds on discharging industrial sewage, and the materials and the financial resources are greatly consumed on the aspects of slurry recovery and sewage treatment. At present, most paper enterprises adopt multi-disc fiber recovery machines to recover fibers and water in white water. The multi-disc fiber recycling machine separates fibers in water from the water by a separation and filtration technology, three different liquids are produced from thin to thick by the white water treatment of the paper machine through a fiber cushion layer, namely turbid filtrate, clear filtrate and ultra-clear filtrate, and the turbid filtrate is used for pulping of the paper machine; the clear filtrate is used for ensuring sealing water of paper machine pulping; the ultra-clean filtrate can be used for normal pressure and high pressure cleaning of a paper machine; and the separated fibers are used for secondary use in papermaking. Through the process, the problems of large water consumption and high water treatment cost of the traditional papermaking are solved, and the environment-friendly clean production is achieved.
At present, a plurality of disc fiber recycling machines on the market mostly adopt polyester mesh bags woven by polyester materials, but the following defects can occur in use: the polyester mesh bag is tightly wrapped on the mesh disc through heating shrinkage, and the uneven shrinkage of polyester meshes is easily caused due to the material reason, the problem of different mesh sizes is prominent, and thus the filtering precision is poor; and the adoption of the heat tightening installation method can also cause the problems of bulging, slurry dropping, weakening of drainage performance, poor quality of filtered water and the like of the mesh bag. The polyester net is affected by the friction of slurry impurities in the long-term use process, the polyester net wires are easy to be raised and napped, the hook fibers block meshes, the drainage performance is reduced, the energy consumption is increased, the long-term use is easy to generate bulges and wrinkles, the stripping difficulty is increased, and the use efficiency can be reduced to more than half of the filtering efficiency of a new net; in order to ensure that high air permeability of meshes is ensured, manufacturers mostly adopt high-pressure water to clean, impurities deposited in polyester meshes are cleaned, the meshes are dredged, but the high-pressure water easily breaks polyester mesh bags due to overlarge pressure, so that the utilization rate of equipment is reduced.
The most basic three steps in the wastewater treatment system of the paper mill are collection, treatment and disposal, and most of the paper mills currently adopt a centralized treatment mode, so that corresponding water pipelines and pressure lifting pump rooms are required to be equipped, the treatment equipment is required to be arranged at a position with the height of 9 meters according to the requirements, wastewater is lifted into the treatment equipment, water treated by the treatment equipment flows into a water tank through the pipelines, in the process, water legs are formed in the pipelines, dehydration is carried out under the vacuum action of the water legs, slurry enters a material box to soak a filtering weir plate, and the flow direction is opposite to the direction of a filter disc, and the liquid level is controlled through the rotating speed. The fan-shaped filter plate is immersed in the slurry, the filtrate flows into the fan-shaped piece and the mandrel, and the displaced air is discharged through a pipeline communicated with the atmosphere through a valve. Pulp fiber slurry concentration and white water recovery filtration in the papermaking production process, such as pulp concentration after washing and purification in the household paper or waste paper recovery process, and fine fibers and fillers are collected during white water recovery.
However, the common problem with multi-disc fiber recyclers is: the filter screen Rong Yihuai needs to be replaced every time of shutdown, the productivity is reduced, the concentration of filtrate is too high, a large amount of slurry is lost, and the production cost is increased; the dehydration effect is poor, the slurry layer is too thin, or the slurry layer is not formed, the multi-disc plate is not cleaned cleanly, the high-pressure spray head is often blocked, and the mechanical maintenance cost is high.
In actual production, the direct-cleaning filter (patent number ZL 2018 2 0617397.2) has the whole flow from cushion pulp feeding to cushion pulp discharging. The water outlet time is 50-60% of the whole process, the water outlet time is short, and the production efficiency is low.
Through intensive research, the main reason that the water outlet time is short is that the SS content of wastewater to be treated of a production enterprise is high, too many fine fibers and SS are trapped on a filter cake during filtration, the formed filter cake is insufficient in bulk, and the filtration efficiency is affected too tightly.
Disclosure of Invention
In order to solve the problems, the invention combines the principle of air-floating type white water treatment, and provides the multi-disc direct-cleaning filter device which has the advantages of simple structure, convenient operation, long service life, capability of greatly improving the filtering efficiency and the filtering precision, capability of improving the wastewater treatment capacity and the production effect, and reduction of the production cost and the use method thereof.
The invention relates to an air-floating type multi-disc direct-cleaning filter, which comprises a shell, wherein a plurality of mutually parallel metal fiber filter discs are arranged in the shell, and a filtered clear liquid outlet is arranged at the lower part of each metal fiber filter disc and corresponds to the position of the shell;
the rear cavity is internally provided with a second baffle, the first baffle and the second baffle are vertically arranged, the plane where the second baffle is positioned is mutually perpendicular to the plane where the first baffle is positioned, and the second baffle divides the rear cavity into two parts which are respectively a mixed air floatation area and an air floatation rear clear liquid area;
the heights of the first partition plate and the second partition plate are smaller than the height of the shell, the upper areas of the first partition plate and the second partition plate in the shell are suspension gathering areas, and the front cavity and the rear cavity are communicated through the suspension gathering areas;
the lower part of the rear cavity is provided with a dissolved air water inlet pipe and a white water inlet pipe, the dissolved air water inlet pipe passes through the air flotation rear clear liquid zone and stretches into the mixed air flotation zone, dissolved air water release devices are arranged on the dissolved air water inlet pipes positioned in the air flotation rear clear liquid zone and the mixed air flotation zone, and one end of the dissolved air water inlet pipe arranged outside the shell is connected with a fiber flocculation generating device;
the white water inlet pipe passes through the air-floating clear liquid zone and extends into the mixed air-floating zone, and a plurality of white water outlet ports are arranged on the white water inlet pipe positioned in the mixed air-floating zone;
the bottom of the air-flotation clear liquid zone is provided with an air-flotation clear liquid outlet pipe, and one end of the air-flotation clear liquid outlet pipe extending out of the shell is communicated with the front cavity through a square cone.
Preferably, the fiber flocculation generating device comprises a hollow tank body, wherein the upper end of the tank body is connected with an upper cover, a water inlet and a compressed air inlet are formed in the upper cover, a filter plate is fixedly arranged in the tank body, the filter plate divides the internal area of the tank body into an upper area and a lower area, the upper area and the lower area are respectively a white water compressed air mixing area and a dissolved air ionization area, and a multi-surface hollow ball filler is filled in the white water compressed air mixing area; an external visual liquid level meter and a pressure meter are arranged on the dissolved air ionization region;
the lower end of the tank body is provided with a dissolved air water outlet which is communicated with a dissolved air water inlet pipe.
Preferably, the dissolved air water release device is a TJ-type dissolved air release device.
The disk dispersing device with the grinding thorns is arranged in the releaser, when white water dissolved with compressed air enters the releaser through the dissolved air water branch pipe, the disk with the grinding thorns in the releaser automatically rotates to disperse slightly large bubbles in the dissolved air white water, so that nano-scale micro-bubbles are formed, the dissolved air quantity is improved, the generation of slightly large bubbles is reduced, and the flocculation and suspension capacity of fine fibers and suspended matters is improved.
Preferably, the dissolved air water release devices are uniformly distributed along the axial direction of the dissolved air water inlet pipe, and the number of the dissolved air water release devices is 4-6.
Preferably, the white water outlets are all arranged towards the bottom of the mixed air floatation area.
The application method of the multi-disc direct-cleaning filter comprises the following steps:
the method comprises the following steps that firstly, an air-floating type multi-disc direct-cleaning filter is connected with a percussion front tank through a cushion pulp pipeline, a cushion pulp valve is arranged on the cushion pulp pipeline, and a pulp pump is further connected to a pipeline between the cushion pulp valve and the percussion front tank; a pulp discharging pipeline connected with the air-floating type multi-disc direct-cleaning filter is connected with a post-beating pool, a pulp discharging valve is arranged on the pulp discharging pipeline, and the pre-beating pool is connected with the post-beating pool through a double-disc mill;
the method comprises the steps of connecting a white water inlet pipe on an air-floating type multi-disc direct-cleaning filter with a white water pool through a white water pipe, wherein a white water pump is arranged on the white water pipe, a water inlet of a fiber flocculation generating device is connected with the white water pipe through a white water branch pipe, an air-floating pump is arranged on the white water branch pipe, and a pneumatic regulating valve is arranged between the white water branch pipe and the white water pump;
the filtered clear liquid outlet is connected with a pneumatic three-way valve through a filtrate pump, the pneumatic three-way valve is connected with a clear water pipe and a return pipe, the clear water pipe is communicated with a clear water tank, and the return pipe is communicated with a white water pipe between a white water branch pipe and a white water inlet pipe; connecting a stripping water pump with a clean water tank, wherein the stripping water pump is connected with a plurality of nozzles through pipelines, and the nozzles are arranged towards a metal fiber filter disc;
secondly, feeding white water into a mixed air floatation area of the air floatation type multi-disc direct-cleaning filter through a white water pipe and a white water inlet pipe, controlling the white water liquid level in the mixed air floatation area through a pneumatic regulating valve on the white water pipe, and simultaneously, starting a cushion slurry valve and a stirring device of the multi-disc direct-cleaning filter, wherein the opening time of the cushion slurry valve is controlled according to the actual demand of the cushion slurry, so that the slurry is supplied to the air floatation type multi-disc direct-cleaning filter;
thirdly, starting a dissolved air pump 1 minute after the white water pump is started, starting to inject white water into the fiber suspension generator by the dissolved air pump, opening an electromagnetic valve connected with a clean air source when the white water level reaches a set level, injecting compressed air into the fiber suspension generator, increasing the pressure in the fiber suspension generator, reducing the flow rate of the dissolved air pump, increasing the water yield, and starting to reduce the liquid level in the fiber suspension generator; when the liquid level is reduced to the set low liquid level, the electromagnetic valve is closed, the water yield is reduced, the flow of the dissolved air pump is increased, and the liquid level is increased; sequentially circulating, mixing white water and compressed air to enable fine fibers in the white water to be filled with air and the specific gravity to be reduced, suspending the fine fibers with the reduced specific gravity in a suspended matter accumulation area at the upper part of a rear cavity when the white water enters a multi-disc direct-cleaning filter, enabling clear filtrate to enter an air-floating clear liquid area from the upper part of a second partition plate, enabling the clear filtrate to flow out through an air-floating clear liquid outlet pipe connected with an air-floating clear liquid outlet, and enabling the clear filtrate to enter a front cavity of the air-floating multi-disc direct-cleaning filter through a square cone;
fourthly, after the white water in the filtrate, air-floating type multi-disc direct-cleaning filter reaches a set liquid level, controlling a stirring device to stop stirring, starting a filtrate pump, and connecting a pneumatic three-way valve on the filtrate pump;
when the thickness of a filter cake on the metal fiber filter disc is smaller than 1cm, filtrate flowing out of the filtrate pump enters a water return pipe through a pneumatic three-way valve, and enters an air-floating type multi-disc direct-cleaning filter through a white water inlet pipe connected with the water return pipe, so that the internal circulation of the system is realized;
when the thickness of a filter cake on the metal fiber filter disc is more than 1cm and less than 3cm, filtrate flowing out of the filtrate pump enters a clear water pipe through a pneumatic three-way valve and enters a clear water tank through the clear water pipe;
when the thickness of the filter cake on the metal fiber filter disc is more than 3cm, the pneumatic regulating valve on the white water pipeline is closed, the turbid white water pump is opened, and the liquid in the air-floating type multi-disc direct-cleaning filter enters the white water tower or the white water pool through the turbid white water pipe; when the liquid level in the shell is lower than a set value, the turbid white water pump stops working;
fifthly, the filter cake is stripped, the turbid white water pump stops acting, the filter liquor pump also stops acting, an air inlet valve on an inlet pipeline of the filter liquor pump is automatically opened, a filter cake stripping water pump and stirring are automatically started, the filter cake is stripped, and after the filter cake stripping is completed, the air inlet valve on the inlet pipeline of the filter liquor pump is automatically closed, and the stripping water pump stops;
step six, discharging the slurry, stopping the stripping water pump, opening a slurry discharging valve, and closing the slurry discharging valve when the liquid level in the shell is lower than a set value;
seventh, the slurry discharging valve is closed, and the pneumatic regulating valve on the white water pipeline is opened; the second to sixth steps are repeated again.
Preferably, the pressure of the compressed air entering through the air inlet on the fiber suspension generating device is 5-6 kg/cc; the flow rate is 4-5 cubic meters per hour, and the pressure in the tank body is 3-4 kilograms per cubic centimeter.
Preferably, the flow rate of the dissolved air pump is 40-50 cubic meters per hour.
The invention has simple structure and convenient operation, can greatly improve the filtering efficiency and the filtering precision, has long service life, ensures that the fine fibers and suspended matters float on the upper part of the water body after the wastewater enters the equipment and is dissolved by the fiber flocculation generator, greatly reduces the content of the fine fibers and the suspended matters in the water body, then enters the filter disc and the filter cake for filtering, and generates explosion and rupture phenomena when passing through the filter cake, so that the filter cake has a honeycomb structure, the air permeability and the water filtering capacity are increased, and the water outlet time and the water outlet rate of the equipment are greatly improved.
Drawings
FIG. 1 is a schematic diagram of an air-floating direct-cleaning filter.
Fig. 2 is a right side view of the mixed air bearing zone of fig. 1.
Fig. 3 is a schematic structural view of a fiber suspension generating device.
FIG. 4 is a schematic diagram of the connection relationship of the air-floating multi-disc direct-cleaning filter in use.
Reference numerals: the device comprises a shell, a 2-metal fiber filter disc, a 3-filtered clear liquid outlet, a 4-first partition plate, a 5-second partition plate, a 6-front cavity, a 7-rear cavity, an 8-mixed air floatation area, a 9-air floatation clear liquid area, a 10-suspended matter accumulation area, a 11-dissolved air water inlet pipe, a 12-white water inlet pipe, a 13-tank body, a 14-upper cover, a 15-compressed air inlet, a 16-water inlet, a 17-filter plate, a 18-polyhedral hollow sphere filler, a 19-external visual liquid level meter, a 20-dissolved air water outlet, a 21-dissolved air water release device and a 22-air floatation clear liquid outlet pipe.
Detailed Description
The invention relates to an air-floating type multi-disc direct-cleaning filter, which comprises a shell 1, wherein a plurality of mutually parallel metal fiber filter discs 2 are arranged in the shell 1, a filtered clear liquid outlet 3 is arranged at the lower part of each metal fiber filter disc 2 and corresponds to the position of the shell 1, a first partition board 4 is arranged in the shell 1, the inner area of the shell 1 is divided into two parts by the first partition board 4, namely a front cavity 6 and a rear cavity 7 respectively, and the metal fiber filter discs 2 are arranged in the front cavity 6;
the rear cavity 7 is internally provided with a second baffle plate 5, the first baffle plate 4 and the second baffle plate 5 are vertically arranged, the plane of the second baffle plate 5 is vertical to the plane of the first baffle plate 4, the second baffle plate 5 divides the rear cavity 7 into two parts, namely a mixed air floatation area 8 and an air floatation supernatant area 9;
the heights of the first partition plate 4 and the second partition plate 5 are smaller than the height of the shell 1, a suspended matter collecting area 10 is arranged in the upper area of the first partition plate 4 and the second partition plate 5 in the shell 1, and the front cavity 6 and the rear cavity 7 are communicated through the suspended matter collecting area 10;
the lower part of the rear cavity 7 is provided with a dissolved air water inlet pipe 11 and a white water inlet pipe 12, the dissolved air water inlet pipe 11 passes through the air flotation rear clear liquid zone 9 and extends into the mixed air flotation zone 8, dissolved air water release devices 21 are arranged on the dissolved air water inlet pipes 11 positioned in the air flotation rear clear liquid zone 9 and the mixed air flotation zone 8, and one end of the dissolved air water inlet pipe 11 arranged outside the shell 1 is connected with a fiber flocculation generation device;
the white water inlet pipe 12 passes through the air-floating clear liquid zone 9 and extends into the mixed air-floating zone 8, and a plurality of white water outlets are arranged on the white water inlet pipe 12 positioned in the mixed air-floating zone 8;
the bottom of the air-flotation clear liquid zone 9 is provided with an air-flotation clear liquid outlet pipe 22, and one end of the air-flotation clear liquid outlet pipe 22 extending out of the shell 1 is communicated with the front cavity 6 through a square cone.
The fiber flocculation generating device comprises a hollow tank body 13, wherein the upper end of the tank body 13 is connected with an upper cover 14, a water inlet 16 and a compressed air inlet 15 are arranged on the upper cover 14, a filter plate 17 is fixedly arranged in the tank body 13, the filter plate 17 divides the internal area of the tank body 13 into an upper area and a lower area, the upper area and the lower area are respectively a white water compressed air mixing area and a dissolved air ionization area, and a multi-surface hollow ball filler 18 is filled in the white water compressed air mixing area; an external visual liquid level meter 19 and a pressure meter are arranged on the dissolved air ionization region;
the lower end of the tank body 13 is provided with a dissolved air water outlet 20, and the dissolved air water outlet 20 is communicated with the dissolved air water inlet pipe 11.
The dissolved air water releasing device 21 is a TJ type dissolved air releaser.
When the white water dissolved with compressed air enters the dissolved air releaser through the dissolved air water branch pipe, the internal disc with the abrasive thorns automatically rotates to disperse slightly larger bubbles in the dissolved air white water to form nano-scale micro-bubbles, thereby improving the dissolved air quantity, reducing the generation of slightly larger bubbles and improving the flocculation suspending capacity of the fine fibers and suspended matters.
The dissolved air water release devices 21 are uniformly distributed along the axial direction of the dissolved air water inlet pipe 11, and the number of the dissolved air water release devices 21 is 4-6.
The white water outlets are all arranged towards the bottom of the mixed air floatation area 8.
The application method of the multi-disc direct-cleaning filter comprises the following steps:
the method comprises the following steps that firstly, an air-floating type multi-disc direct-cleaning filter is connected with a percussion front tank through a cushion pulp pipeline, a cushion pulp valve is arranged on the cushion pulp pipeline, and a pulp pump is further connected to a pipeline between the cushion pulp valve and the percussion front tank; a pulp discharging pipeline connected with the multi-disc direct-cleaning filter is connected with a post-beating pool, a pulp discharging valve is arranged on the pulp discharging pipeline, and the pre-beating pool is connected with the post-beating pool through a double-disc mill;
the method comprises the steps of connecting a white water inlet pipe 12 on an air-floating type multi-disc direct-cleaning filter with a white water pool through a white water pipe, wherein a white water pump is arranged on the white water pipe, a water inlet 16 of a fiber flocculation generating device is connected with the white water pipe through a white water branch pipe, an air-floating pump is arranged on the white water branch pipe, and a pneumatic regulating valve is arranged between the white water branch pipe and the white water pump;
the filtered clear liquid outlet 3 is connected with a pneumatic three-way valve through a filtrate pump, the pneumatic three-way valve is connected with a clear water pipe and a return pipe, the clear water pipe is communicated with a clear water tank, and the return pipe is communicated with a white water pipe between a white water branch pipe and a white water inlet pipe 12; connecting a stripping water pump with a clean water tank, wherein the stripping water pump is connected with a plurality of nozzles through pipelines, and the nozzles are arranged towards a metal fiber filter disc 2;
secondly, feeding white water into a mixed air floatation area 8 of the air floatation type multi-disc direct-cleaning filter through a white water pipe and a white water inlet pipe 12, controlling the white water liquid level in the mixed air floatation area 8 through a pneumatic regulating valve on the white water pipe, and simultaneously, starting a cushion slurry valve and a stirring device of the multi-disc direct-cleaning filter, wherein the opening time of the cushion slurry valve is controlled according to the actual demand of the cushion slurry, so that the slurry is supplied to the air floatation type multi-disc direct-cleaning filter;
thirdly, starting a dissolved air pump 1 minute after the white water pump is started, starting to inject white water into the fiber suspension generator by the dissolved air pump, opening an electromagnetic valve connected with a clean air source when the white water level reaches a set level, injecting compressed air into the fiber suspension generator, increasing the pressure in the fiber suspension generator, reducing the flow rate of the dissolved air pump, increasing the water yield, and starting to reduce the liquid level in the fiber suspension generator; when the liquid level is reduced to the set low liquid level, the electromagnetic valve is closed, the water yield is reduced, the flow of the dissolved air pump is increased, and the liquid level is increased; sequentially circulating, mixing white water and compressed air to enable fine fibers in the white water to be filled with air and reduce specific gravity, suspending fine fibers with light specific gravity in a suspended matter accumulation area 10 at the upper part of a rear cavity 7 when the white water enters an air-floating type multi-disc direct-cleaning filter, enabling clear filtrate to enter an air-floating clear liquid area 9 from above a second partition plate 5, enabling clear liquid to flow out through an air-floating clear liquid outlet pipe 22 connected with an air-floating clear liquid outlet, and enabling clear liquid to enter a front cavity 6 of the multi-disc direct-cleaning filter through a square cone;
fourthly, after the white water in the filtrate and multi-disc direct-cleaning filter reaches a set liquid level, controlling a stirring device to stop stirring, starting a filtrate pump, and connecting a pneumatic three-way valve on the filtrate pump;
when the thickness of a filter cake on the metal fiber filter disc 2 is smaller than 1cm, filtrate flowing out of the filtrate pump enters a water return pipe through a pneumatic three-way valve, and enters an air-floating type multi-disc direct-cleaning filter through a white water inlet pipe 12 connected with the water return pipe, so that the internal circulation of the system is realized;
when the thickness of the filter cake on the metal fiber filter disc 2 is more than 1cm and less than 3cm, the filtrate flowing out of the filtrate pump enters a clear water pipe through a pneumatic three-way valve and enters a clear water tank through the clear water pipe;
when the thickness of the filter cake on the metal fiber filter disc 2 is more than 3cm, a pneumatic regulating valve on a white water pipeline is closed, a turbid white water pump is opened, and liquid in the air-floating type multi-disc direct-cleaning filter enters a white water tower or a white water pool through a turbid white water pipe; when the liquid level in the shell 1 is lower than a set value, the turbid white water pump stops working;
fifthly, the filter cake is stripped, the turbid white water pump stops acting, the filter liquor pump also stops acting, an air inlet valve on an inlet pipeline of the filter liquor pump is automatically opened, a filter cake stripping water pump and stirring are automatically started, the filter cake is stripped, and after the filter cake stripping is completed, the air inlet valve on the inlet pipeline of the filter liquor pump is automatically closed, and the stripping water pump stops;
step six, discharging the slurry, stopping the stripping water pump, opening a slurry discharging valve, and closing the slurry discharging valve when the liquid level in the shell 1 is lower than a set value;
seventh, the slurry discharging valve is closed, and the pneumatic regulating valve on the white water pipeline is opened; the second to sixth steps are repeated again.
The pressure of compressed air entering through an air inlet on the fiber suspension generating device is 5-6 kg/cc; the flow rate is 4-5 cubic meters per hour, and the pressure in the tank 13 is 3-4 kilograms per cubic centimeter.
The flow rate of the dissolved air pump is 40-50 cubic meters per hour.
Operation of the fiber suspension generator: the saturated gas dissolving mode is adopted, the water inlet and outlet mode is adopted, and when the device is operated: when the dissolved air pump is started, white water enters the tank body 13, the liquid level in the fiber suspension generating device rises, when the dissolved air water reaches a high liquid level, the electromagnetic valve for controlling compressed air is automatically opened and is used for air intake, the pressure of the tank body 13 rises, the water yield is increased, the liquid level starts to fall, when the liquid level reaches a low liquid level, the electromagnetic valve is automatically closed, the water outlet flow is reduced, and the liquid level rises. In this way, the dissolved air quantity and the water yield are relatively stable, and the linkage and combination with an automatic control system of the air-floating direct-cleaning filter are easy to realize. The filter is combined with a direct-cleaning filter, the control of the dissolved air pump is synchronous with the water inlet pump, namely the filtrate pump is opened, and the dissolved air pump is opened; and on the contrary, the water inlet pump is closed, and the dissolved air pump is closed. After the water inlet pump is closed, the water inlet pump stops water inlet, and as the liquid level and the pressure in the tank body 13 are in high positions, the dissolved air water releasing device 21 continuously releases the dissolved air water, and after the dissolved air water is released, undissolved compressed air in the tank body 13 is emptied under pressure through the releaser, white water in the tank body 13 is dispersed and the small balls of the filter plate 17 are suddenly out of pressure and are in a boiling state for self cleaning, so that the defects of blockage and residue are effectively overcome.
After the dissolved air water entering the direct-cleaning filter from the dissolved air water inlet pipe 11 is released by the dissolved air water releasing device 21, the dissolved air water is uniformly mixed with the white water flowing out of the white water inlet pipe 12 arranged right below the dissolved air water inlet pipe 11, fine fibers, suspended matters and micro bubbles are combined in the rising process of the mixed waste water, structural cross-linking is generated between the fibers and the suspended matters and between the suspended matters and the suspended matters, the body is larger, the specific gravity becomes smaller, the suspended air water can suspend and gather on the surface of the waste water, namely enters the suspended matter gathering area 10, overflows to the upper part of the filtering area of the filtered liquid after air floatation, namely the upper part of the front cavity 6, and the clarified liquid overflows to the mixed air floatation area 8, the clarified liquid is mixed with the dissolved air water released by the dissolved air water releasing device 21 again, the mixed clarified liquid flows into the supernatant area 9 after air floatation through pressure difference and flows into the front cavity 6 through the supernatant outlet pipe 22 after air floatation and is filtered by the metal fiber filter disc 2, the clarified wastewater containing micro bubbles in the process is subjected to deep filtration through a filter cake under the pumping action of a filtrate pump, the micro bubbles in the wastewater are broken, the suspended SS in the wastewater is trapped by the filter cake or is contained in the filter cake, the formed filter cake structure is more relaxed, the air permeability is greatly improved, the filtering performance is enhanced, the wastewater passing through the filter cake becomes clear water, the suspended matters are less than 20mg/l, the COD removal rate can reach more than 80%, and the water treatment time is greatly prolonged. The filtered clear liquid can be completely used for high and low pressure spray washing of a production system and dissolution dilution of chemical industry, can completely replace fresh water to be used or discharged up to standard, after filtration, the wastewater with reduced water level is sent to a pre-filtration tank through a pipeline or a pump, and suspended matters, fine fibers and stripped filter cakes which are gathered on the shell 1 are pumped to a fiber collecting tank for recycling under the action of a stirrer below the front part of the machine case.