CN106746137A - Magnetic separation method and device for treating oil-containing graphite wastewater - Google Patents

Abstract

The invention relates to a magnetic separation method for treating oily graphite wastewater, which adopts a combined process of air flotation and magnetic separation to treat oil and suspended matter in the oily graphite wastewater. A. First, add the wastewater to the air flotation tank to float part of the suspended matter such as oil and graphite in the wastewater out of the water surface, and scrape it into the slag tank by the slag scraper. The air flotation adopts the internal circulation jet pressurized dissolved air flotation method , the dissolved air pressure is 0.25~0.4MPa, the reflux ratio is 10%~15%, the separation load is 10~13m ³ /m ² ·h, and the residence time is 20~30min; B. Send the air flotation water to the magnetic separation The device enters the pre-magnetic processor in the magnetic separation device for pre-magnetization, and then the sewage enters the inclined tube sedimentation tank. The flow rate of the inclined tube sedimentation tank is controlled at 20-35mm/s, and then the disk separator absorbs the remaining flocs and suspended solids in the water On the disk, the waste water flowing through a single disk separator is controlled at 200-400m ³ /h, the scraper scrapes the sludge into the sludge discharge device, and the treated clean water is discharged from the water outlet. No water treatment chemicals are added, and it is suitable for treating oily and graphite-containing sewage that is not easy to settle naturally.

Description

A magnetic separation method and device for treating oily graphite wastewater

technical field

The invention relates to the technical field of water treatment, in particular to a magnetic separation method and device for treating oil-containing graphite wastewater.

Background technique

In the production process of hot-rolled seamless steel pipes in seamless plants, it is necessary to add high-temperature water-based mandrel lubricants to lubricate the seamless pipes. The main component of graphite milk is mixed with spray water during the cooling of the rolling mill and enters the circulating water system. , causing the content of suspended solids in circulating water to exceed the standard; during the rolling cooling process, the cooling water will also bring a certain amount of lubricating oil and hydraulic oil. In the high-temperature water-based mandrel lubricant, sodium tripolyphosphate and sodium lignosulfonate , dispersant, anti-sedimentation agent, etc., to form relatively stable oil-containing graphite wastewater, which is difficult to remove using ordinary advection sedimentation tanks; at the same time, iron oxide scale, dust and other substances washed down during the rolling process will be removed during the operation of the system , will form sludge in the water. If the circulating water containing graphite and oil is not effectively treated, the sludge will block the cooling spray head and form sludge on the water pipe wall, which will seriously reduce the cooling effect and affect the normal use of the cooling system. normal production. Therefore, for the treatment of oil-containing graphite steel rolling wastewater, the separation of graphite, grease and metal oxides is the key to the treatment process.

Because oily wastewater is harmful to the environment, people have developed many treatment methods over the years. However, due to the variety of oil pollution, the complex nature of pollution sources, large discharge volume, and high treatment requirements, it has brought great difficulties and pressures to the treatment of oily wastewater. . The commonly used treatment methods are divided into physical method, chemical method and biological method. Physical method is to use physical action to treat oil, such as precipitation method, air flotation method, filtration method, membrane method, magnetic separation, etc.; chemical method treats emulsified oil in wastewater through demulsification, such as coagulation precipitation method, acidification method Etc.; Biological method is the use of microorganisms to remove colloidal oil droplets and dissolved oil in wastewater, such as activated sludge method, biofilm method, anaerobic biological treatment, etc.

For the wastewater containing magnetic substances such as iron oxide scale in the suspension, it can be removed by magnetization because of the ferromagnetic substances. For oil and other non-magnetic substances in wastewater, pre-magnetic technology can be used to combine them with magnetic substances and be removed by magnetic adsorption. For general wastewater, magnetic materials can be added to treat sewage. According to this principle, people have developed some separation methods and equipment one after another.

For example, the patent CN 103183442 A discloses a "oil sludge magnetic separation water treatment technology". This method is based on the ordinary coagulation and sedimentation sewage treatment process, and iron ore powder is added to achieve the purpose of optimizing the treatment effect. However, this method requires the addition of chemical On the basis of reagents, iron ore powder is added, and at the same time, the waste water in the treatment project of this method has not been pre-magnetized, which reduces the effect of magnetic separation.

Patent CN 1074198 A discloses a "permanent magnetic separation device for treating wastewater from iron and steel plants" and CN 201442879 U discloses a "dual magnetic separation purification equipment for wastewater". Although these devices have high magnetic strength, large gradient and large processing capacity , high separation effect, etc., but there are also some problems. For example, if the above-mentioned magnetic purification treatment equipment is used, due to the short retention time of sewage in the magnetic separator, small particles of ferromagnetic substances are difficult to be adsorbed, resulting in low purification efficiency and insufficient water output. Meet the production requirements, and the effect on oil precipitation and adsorption is also limited. Therefore, these methods and devices are not suitable for the actual situation that the oily graphite waste water of seamless factory contains oil and the concentration of graphite is relatively large.

Patent CN 201485341 discloses "a permanent magnet magnetic separation sewage treatment device". This patent adds chemical flocculant and magnetized magnetic powder to wastewater to treat wastewater, which is especially suitable for large-scale wastewater treatment, and can directly treat high-temperature sewage , High magnetic separation efficiency. However, this method needs to add PAC and magnetic powder, and needs to continuously inject medicaments during the use process, and the cost is relatively high.

Patent CN 101301637 A discloses a "magnetic separation, filtration and purification device", which invents a purification device for purifying sewage involving magnetic separation. This invention mainly uses permanent magnets to adsorb magnetic flocs in the sewage before and after the filter unit, which greatly reduces the processing load of the filter unit and is conducive to the long-term work of the filter unit, but this method needs to add chemical flocculants and filter membranes, and the cost is relatively high. High, suitable for sewage treatment with small flow.

Patent CN 103265044 A discloses "Flocculation-magnetic separation method for removing impurities in water glass solution", which discloses a method for removing impurities in water glass solution by flocculation-magnetic separation, including stirring and mixing, flocculation, magnetic Separation, neutralization, secondary magnetic separation and other steps. This method needs to add modified nano-ferric oxide, and add aluminum-iron coagulant and polyacrylamide flocculant when removing impurities, and the subsequent investment is large.

Patent CN 101913685 A discloses "a new type of magnetic separation sewage treatment device", which invents a new type of magnetic separation sewage treatment device. The device is mainly a tank, and the tank is subdivided into a regulating stirring tank, a clapboard flocculation tank, a magnetic separation sedimentation tank and an advection sedimentation tank. By adding a magnetic seed with a large specificity into the sewage entering the tank, it can be combined with small floc particles to increase the specific gravity and accelerate the sedimentation under the action of the magnetic field, shortening the sedimentation time. However, the treatment effect of this method is limited and needs to be used in conjunction with other methods.

Patent CN 102060350 A discloses "A Process Method for Advanced Treatment of Oily Wastewater", which consists of two systems of adsorption and regeneration: the adsorption system is composed of a series of multi-column series adsorption towers that realize parallel operation, alternately performing traditional processes The low concentration of 30-50mg/L oil-containing effluent is used for advanced treatment, and the adsorbent is modified fly ash, activated carbon, expanded graphite and other adsorption materials; when the adsorption of this group of adsorption towers is saturated, switch this group of adsorption towers to the biological regeneration system Perform in situ regeneration. The adsorption effect of this method is stable and the treatment effect is good, but the microbial activity in the regeneration process is unstable and the adsorption time is long.

Patent CN 202729850 U discloses "a device for absorbing oily wastewater with coal slag", and this patent has invented a device for absorbing oily wastewater with coal slag. Use the driving device to spread the cinder into a cinder layer, so that the oily wastewater flows into the cinder layer from the bottom to the top from the cinder adsorption pool, so that the oil pollutants in the oily wastewater are effectively absorbed by the cinder, and the cinder can automatically fall to the slag discharge vehicle through the slag discharge mechanism It is sent to the boiler for combustion; the supernatant water of the oily wastewater adsorbed by the cinder layer flows into the overflow tank, and then is discharged through sedimentation. This method has simple structure, convenient operation and low operating cost, but the adsorption effect is not ideal, and subsequent advanced treatment is required.

"Industrial Water and Wastewater" discloses "Design of a Combined Degreasing Equipment", author: Zou Zhifang, Luo Kuiyuan, Nie Yanqiu, 2005,36(2):69-71. This article uses the integrated method to design a combined oil removal equipment, which combines the characteristics of the vertical partition oil separation method, the honeycomb inclined tube oil separation method, and the magnetic particle adsorption and filtration method, and combines the waste oil recycling treatment. The operation results show that the oil content in the effluent is lower than 1mg/L, and the treatment effect is good. However, this method occupies a large area, is complicated to operate, and has high operating costs.

"China Water Supply and Drainage" published "Application of Supermagnetic Separation Water Purification Technology in Beixiaohe Sewage Treatment Plant", authors: Zhou Jianzhong, Jin Yunhui, Luo Benfu, Zhou Wenbin, Zhou Shengqiao, 2012,28(6):78-81. This article introduces the second-stage primary treatment project of Beixiaohe Sewage Treatment Plant, which adopts supermagnetic separation water purification technology, and analyzes the working principle and technical characteristics of supermagnetic separation water purification treatment technology. This application requires the addition of magnetic seeds and has no degreasing capability.

"Journal of Shanghai Jiaotong University" published "High Gradient Magnetic Separation Method for Oily Wastewater Treatment", Yao Yedong, Qian Xueling, Li Daotang, Lin Weiping, 2003, 37(11): 1791-1794. This article studies the principle and process conditions of using high gradient magnetic separation method to treat oily wastewater, discusses the influence of factors such as the amount of magnetic powder added, magnetic induction intensity, stirring time, adding flocculants, and adjusting pH value on the oil removal effect, and recommends process parameters. However, the article only discusses the treatment of oils, and does not involve the removal of suspended solids.

Contents of the invention

The technical problem to be solved by the present invention is to provide a magnetic separation method and device for treating oily graphite wastewater. This process can effectively remove oil and suspended solids in oily graphite wastewater without adding any chemicals and reduce system operating costs. To achieve the purpose of recycling. The content of oil and suspended solids in the treated wastewater complies with the discharge requirements for suspended solids and petroleum in the "GB50050-2007 Industrial Circulating Cooling Water Treatment Design Code" and "GB13456-2012 Iron and Steel Industry Water Pollutant Discharge Standard".

To achieve the above object, the present invention adopts the following technical solutions:

A magnetic separation method for treating oily graphite wastewater, which uses a combined process of air flotation and magnetic separation to treat oil and suspended matter in oily graphite wastewater, specifically comprising the following steps:

A) Firstly, the wastewater is added to the air flotation tank, and part of the suspended matter such as oil and graphite in the wastewater is floated out of the water surface through the air flotation device, and scraped into the slag tank by the slag scraper. The air flotation is added by an internal circulation jet Pressure dissolved air flotation method, the dissolved air pressure is 0.25~0.4MPa, the reflux ratio is 10%~15%, the separation load is 10~13m ³ /m ² ·h, and the residence time is 20~30min;

B) Send the air flotation water into the magnetic separation device, enter the pre-magnetic processor in the magnetic separation device for pre-magnetization, the waste water enters from the pre-magnetic processor in the middle below the water inlet tank, and the waste water is pre-magnetized when flowing through the pre-magnetic processor The permanent magnetic block in the magnetic processor is pre-magnetized, and the magnetic substances such as tiny iron and metal particles in the sewage are magnetized and flocculated, and at the same time bond graphite particles and tiny oil particles to form flocs, and then the sewage enters the inclined tube sedimentation tank for sedimentation Part of the floc, the flow rate of the inclined tube sedimentation tank is controlled at 20-35mm/s, and the settled sludge is discharged from the sludge discharge pipe through the sludge discharge port in the sludge hopper; the effluent of the inclined tube sedimentation tank enters the disk tank with a semicircular section, The disk separator is placed along the water tank, and the disk separator is driven by the motor to continuously rotate the disk separator shaft. The disk in the disk separator relies on the high-intensity magnetic field and high magnetic field gradient to absorb the remaining flocs and suspended matter in the water on the disk, and the flow The waste water through a single disk separator is controlled at 200-400m ³ /h, and both sides of the mud scraper strips on the mud scraper are close to the disk of the disk separator to scrape the sludge into the sludge discharge device and discharge it through the slag discharge port for treatment. The final clean water is discharged from the water outlet, and this process is repeated with the continuous circulation of the circulating water, and finally reaches the discharge standard.

A magnetic separation device for treating oil-containing graphite wastewater, including a main body bracket, a water inlet tank is arranged on the main body bracket, the water inlet tank is connected to a purification water tank, the purification water tank is connected to two parallel semicircular disk water tanks, the disk water tank is connected to a water outlet, and the middle of the water inlet tank The bottom is equipped with a pre-magnetic processor that discharges water downwards, and the lower port of the pre-magnetic processor is connected to a purification tank, which is equipped with an inclined tube sedimentation tank, and a sludge bucket is installed at the bottom of the purification tank, and a sludge discharge pipe is installed in the sludge bucket , There is a disk separator in the disk water tank, the disk separator is driven by a motor to rotate, and the disk separator is equipped with a mud scraping device and a mud discharge device.

The pre-magnetic processor is a hollow rectangular cylinder wall structure. There are 3 to 6 strip-shaped magnetic boxes arranged vertically inside the stainless steel tube wall to divide the pre-magnetic separator into several rectangular channels. The magnetic boxes are supported by the magnetic box support frame. Rectangular nano-scale NdFeB permanent magnet blocks are evenly distributed inside each magnetic box, and the outside of the magnetic block is wrapped with a stainless steel shell, and the poles of the magnetic blocks in the magnetic box are set in opposite directions.

The disks on the disk separator are connected end-to-end along the axial direction to form a whole, arranged in a spiral shape, with gaps between the spiral disks, and the magnetic blocks on the disk are arranged in a magnetic accumulation mode, and the magnetic accumulation blocks are arranged repeatedly in NN or SS, and along the The spiral disk surface is arranged repeatedly in sequence, and the disk is composed of a nano-scale NdFeB permanent magnet block in the middle and a stainless steel shell wrapped outside.

The mud scraping device includes a sprocket, a chain, and a mud scraper. The chain is connected to the sprockets fixed at both ends, and the mud scraper is fixed on the chain to form a ring-shaped mud scraper. The scraper on one side of the ring-shaped mud scraper The strip extends into the gap of the spiral disk of the disk separator and is close to the disk. With the rotation of the disk separator, the scraper moves horizontally under the push of the spiral disk, thereby driving the sprocket to rotate, that is, the ring scraper moves along with the disk. The separator rotates while rolling.

Compared with prior art, the beneficial effect of the present invention is:

The oil removal rate of the air flotation tank of the present invention is generally above 40% without adding flocculant. In the disk water tank, because the wastewater flows along the axial direction of the disk separator, the contact time between the wastewater and the disk is greatly increased compared with other devices that flow through the disk separator along the radial direction, which is conducive to the adsorption of fine particle suspension.

The invention provides a method and a device for treating oil-containing graphite wastewater by a combined process of air flotation and magnetic separation. After the oil-containing graphite wastewater of the seamless factory is treated by the present invention, the water quality meets the discharge requirements for suspended solids and petroleum in the "GB50050-2007 Industrial Circulating Cooling Water Treatment Design Specification" and "GB13456-2012 Iron and Steel Industry Water Pollutant Discharge Standard" . The method does not add water treatment chemicals, is suitable for treating oily and graphite-containing sewage that is not easy to naturally settle, and the investment and operating costs are more suitable for practical engineering applications, which is beneficial to energy conservation and emission reduction of enterprises.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

FIG. 2 is a top view of FIG. 1 .

Fig. 3 is a side view of the disk separator and the disk water tank.

Figure 4 is a schematic structural view of the mud scraping device.

Figure 5 is a schematic structural view of the scraper.

In the figure: 1-Water inlet tank 2-Magnet box 3-Incline tube sedimentation tank 4-Motor 5-Disk separator shaft 6-Disk separator 7-Disk 8-Mud scraping device 9-Mud discharge device 10-Water outlet 11- Pre-magnetic processor 12-purification water tank 13-mud discharge pipe 14-main frame 15-mud discharge port 16-disk water tank 17-slag discharge port 18-sludge bucket 19-sprocket 20-chain 21-mud scraper 22 - Scraper slats

detailed description

The specific embodiment of the present invention is further described below in conjunction with accompanying drawing:

As shown in Figure 1-3, a magnetic separation device for treating oil-containing graphite wastewater includes a main body bracket 14, on which a water inlet tank 1 is arranged, and the water inlet tank 1 is connected to a purified water tank 12, and the purified water tank 12 is connected to two parallel semi- Circular disk water tank 16, the disk water tank 16 is connected to the water outlet 10, the bottom of the middle of the water inlet tank 1 is provided with a pre-magnetic processor 11 for water outlet downwards, the lower mouth of the pre-magnetic processor 11 is connected to the purification water tank 12, and the purification water tank 12 is provided with a slope Pipe sedimentation tank 3, sludge hopper 18 is arranged at the bottom of purified water tank 12, sludge discharge pipe 13 is arranged in sludge hopper 18, disk separator 6 is arranged in disk water tank 16, disk separator 6 is driven by motor 4 to rotate, disk The separator 6 is provided with a mud scraping device 8 and a mud discharge device 9 .

The pre-magnetic processor 11 is a hollow rectangular cylinder wall structure, 3 to 6 strip magnetic boxes 2 are arranged vertically inside the stainless steel cylinder wall, and the pre-magnetic separator is divided into several rectangular channels, and the magnetic boxes 2 are supported by the magnetic boxes Supported by a frame, rectangular nano-scale NdFeB permanent magnet blocks are evenly distributed inside each magnetic box 2, and the outside of the magnetic block is wrapped with a stainless steel shell, and the poles of the magnetic blocks in the magnetic box 2 are oppositely arranged.

The disks 7 on the disk separator 6 are connected end-to-end in the axial direction to form a whole, arranged in a spiral shape, with gaps between the spiral disks, and the magnetic blocks on the disk 7 are arranged in a magnetic accumulation mode, and the magnetic accumulation blocks are arranged in NN or SS repetitions , and repeatedly arranged along the spiral disk surface, the disk 7 is composed of a nano-scale NdFeB permanent magnet block in the middle and a stainless steel shell wrapped outside.

As shown in Figure 4-5, the scraper device includes a sprocket 19, a chain 20, and a scraper 21. The chain 20 is connected to the sprocket 19 fixed at both ends, and the scraper 21 is fixed on the chain 20 to form a ring. The mud scraper 21, the scraper strip 22 on one side of the ring-shaped mud scraper 21 extends into the gap of the spiral disk of the disk separator 6 and is close to the disk 7. With the rotation of the disk separator 6, the mud scraper 21 Driven by the helical disk, it moves horizontally, thereby driving the sprocket 19 to rotate, that is, the annular mud scraper 21 rolls along with the rotation of the disk separator 6 .

The treatment process of oily graphite wastewater: send the wastewater into the pressurized dissolved air flotation tank, after the air flotation treatment, the air flotation water is sent to the water inlet tank 1 in the magnetic separation device, and passes through the pre-magnetic processor 11 in the middle of the water inlet tank 1 Enter the purified water tank 12, under the action of the magnetic box 2 in the pre-magnetic processor 11, the wastewater is pre-magnetized, and with the agitation of the water flow, the magnetic substances such as iron and metal particles in the sewage are magnetized and flocculated, and at the same time bonded Graphite particles and tiny oil particles form flocs. Then the sewage enters the inclined tube sedimentation tank 3 to settle part of the flocs, and the settled sludge is discharged in the sludge hopper 18 by the sludge discharge pipe 13 through the sludge discharge port 15 . The water outlet of the inclined tube sedimentation tank 3 enters the water tank 16 whose section is semicircular, and the disk separator 6 is arranged along the water tank 16, and the disk separator 6 is driven by the motor 4 to continuously rotate the disk separator shaft 5. The disk 7 made of nano-scale NdFeB permanent magnet material in the disk separator 6 will absorb the remaining flocs and suspended matter in the water on the disk 7 by means of a high-intensity magnetic field and a high magnetic field gradient, and the sawtooth on the mud scraper 21 Both sides of the shaped mud scraper strip 22 are close to the disk 7 of the disk separator 6 to scrape the sludge into the sludge discharge device 9, and discharge through the slag discharge port 17, and the treated clear water is discharged from the water outlet 10. This process is repeated with the continuous circulation of circulating water, and finally reaches the discharge standard.

Example 1

A magnetic separation method for processing oily graphite wastewater is as follows:

Send the oil-containing graphite wastewater with an oil content of 49.7mg/L and a total suspended solids of 196.3mg/L into the pressurized dissolved air flotation tank, the dissolved air pressure is 0.30MPa, the reflux ratio is 15%, and the separation load is 13m ³ /m ² h, the hydraulic retention time is 30min, and about 40% of oil is removed; after the air flotation treatment, the air flotation water is sent to the water inlet tank 1 in the magnetic separation device, and passes through the pre-magnetic processor in the middle of the water inlet tank 1 11 enters the purified water tank 12, the pre-magnetized wastewater is flocculated in the purified water tank 12, and then part of the flocs are deposited in the inclined tube sedimentation tank 3. Under the action of the magnetic field of the device 6, the remaining flocs and suspended matter in the water are adsorbed on the disk 7. The processing capacity of a single disk separation device is 400m ³ /h, and the treated clean water is discharged from the water outlet 10 and sent to the circulating water for recycling. , after several consecutive operations, the circulating water quality gradually stabilized and reached the discharge standard.

Example 2

A magnetic separation method for processing oily graphite wastewater is as follows:

Send the oil-containing graphite wastewater with an oil content of 49.7mg/L and a total suspended solids of 196.3mg/L into the pressurized dissolved air flotation tank, the dissolved air pressure is 0.25MPa, the reflux ratio is 10%, and the separation load is 10m ³ /m ² h, the hydraulic retention time is 20min, and about 40% of the oil is removed; after the air flotation treatment, the air flotation water is sent to the water inlet tank 1 in the magnetic separation device, and passes through the pre-magnetic processor in the middle of the water inlet tank 1 11 enters the purified water tank 12, the pre-magnetized waste water is flocculated in the purified water tank 12, and then part of the flocs are precipitated in the inclined tube sedimentation tank 3. Under the action of the magnetic field of the device 6, the remaining flocs and suspended matter in the water are adsorbed on the disk 7. The processing capacity of a single disk separation device is 300m ³ /h, and the treated clean water is discharged from the water outlet 10 and sent to the circulating water for recycling. , after several consecutive operations, the circulating water quality gradually stabilized and reached the discharge standard.

Example 3

A magnetic separation method for processing oily graphite wastewater is as follows:

Send the oil-containing graphite wastewater with an oil content of 49.7mg/L and a total suspended solids of 196.3mg/L into the pressurized dissolved air flotation tank, the dissolved air pressure is 0.35MPa, the reflux ratio is 12%, and the separation load is 11m ³ /m ² h, the hydraulic retention time is 25min, and about 40% of oil is removed; after the air flotation treatment, the air flotation water is sent to the water inlet tank 1 in the magnetic separation device, and passes through the pre-magnetic processor in the middle of the water inlet tank 1 11 enters the purified water tank 12, the pre-magnetized waste water is flocculated in the purified water tank 12, and then part of the flocs are precipitated in the inclined tube sedimentation tank 3. Under the action of the magnetic field of the device 6, the remaining flocs and suspended matter in the water are adsorbed on the disk 7. The processing capacity of a single disk separation device is 250m ³ /h, and the treated clean water is discharged from the water outlet 10 and sent to the circulating water for recycling. , after several consecutive operations, the circulating water quality gradually stabilized and reached the discharge standard.

In the above examples, the water quality measurement results of the treated circulating water are shown in Table 1, and the results show that the method can effectively remove oil and suspended solids in the wastewater, reaching the "GB50050-2007 Design Specification for Industrial Circulating Cooling Water Treatment" and Discharge requirements of "GB13456-2012 Discharge Standard of Water Pollutants for Iron and Steel Industry".

Each embodiment of table 1 is to the removal effect of oils and suspended solids

The above is only the basic principle of the present invention, and does not limit the present invention in any way. All equivalent changes and modifications according to the present invention are within the scope of the technical protection scheme of this patent.

Claims (5)

1. a magnetic separation method for processing oily graphite waste water, is characterized in that, adopts air flotation and magnetic separation combined process to process oil, suspended matter in oily graphite waste water, specifically comprises the following steps: A) Firstly, the wastewater is added to the air flotation tank, and part of the suspended matter such as oil and graphite in the wastewater is floated out of the water surface through the air flotation device, and scraped into the slag tank by the slag scraper. The air flotation is added by an internal circulation jet Pressure dissolved air flotation method, the dissolved air pressure is 0.25~0.4MPa, the reflux ratio is 10%~15%, the separation load is 10~13m ³ /m ² ·h, and the residence time is 20~30min; B) Send the air flotation water into the magnetic separation device, enter the pre-magnetic processor in the magnetic separation device for pre-magnetization, the waste water enters from the pre-magnetic processor in the middle below the water inlet tank, and the waste water is pre-magnetized when flowing through the pre-magnetic processor The permanent magnetic block in the magnetic processor is pre-magnetized, and the magnetic substances such as tiny iron and metal particles in the sewage are magnetized and flocculated, and at the same time bond graphite particles and tiny oil particles to form flocs, and then the sewage enters the inclined tube sedimentation tank for sedimentation Part of the floc, the flow rate of the inclined tube sedimentation tank is controlled at 20-35mm/s, and the settled sludge is discharged from the sludge discharge pipe through the sludge discharge port in the sludge hopper; the effluent of the inclined tube sedimentation tank enters the disk tank with a semicircular section, The disk separator is placed along the water tank, and the disk separator is driven by the motor to continuously rotate the disk separator shaft. The disk in the disk separator relies on the high-intensity magnetic field and high magnetic field gradient to absorb the remaining flocs and suspended matter in the water on the disk, and the flow The waste water through a single disk separator is controlled at 200-400m ³ /h, and both sides of the mud scraper strips on the mud scraper are close to the disk of the disk separator to scrape the sludge into the sludge discharge device and discharge it through the slag discharge port for treatment. The final clean water is discharged from the water outlet, and this process is repeated with the continuous circulation of the circulating water, and finally reaches the discharge standard. 2. A magnetic separation device for treating oily graphite wastewater, characterized in that it comprises a main body bracket, a water inlet tank is arranged on the main body bracket, the water inlet tank is connected to a purified water tank, and the purified water tank is connected to two parallel semicircular disk water tanks, and the magnetic disk water tank is connected At the water outlet, there is a pre-magnetic processor with downward water outlet at the bottom of the middle of the water inlet. The lower port of the pre-magnetic processor is connected to the purification tank. There is an inclined tube sedimentation tank in the purification tank. There is a sludge bucket at the bottom of the purification tank. There is a mud discharge pipe inside, a disk separator is installed in the disk water tank, and the disk separator is driven by a motor to rotate, and a mud scraping device and a mud discharge device are installed outside the disk separator. 3. A magnetic separation device for treating oil-containing graphite wastewater according to claim 2, wherein the pre-magnetic processor is a hollow rectangular cylinder wall structure, and 3 to 6 The strip-shaped magnetic box divides the pre-magnetic separator into several rectangular channels. The magnetic box is supported by the magnetic box support frame. The rectangular nano-scale NdFeB permanent magnet blocks are evenly distributed inside each magnetic box, and the magnetic blocks are wrapped with Stainless steel shell, the poles of the magnetic blocks in the magnetic box are set oppositely. 4. A magnetic separation device for treating oily graphite waste water according to claim 2, characterized in that, the disks above the disk separator are connected end to end in the axial direction to form a whole, arranged in a spiral shape, and between the spiral disks There are gaps, and the magnetic blocks on the disk are arranged in a magnetic accumulation mode. The magnetic accumulation blocks are arranged repeatedly in NN or SS, and are arranged repeatedly along the spiral disk surface. The magnetic disk is wrapped by the nano-sized NdFeB permanent magnet block in the middle and Composed of stainless steel casing. 5. A kind of magnetic separation device for treating oily graphite waste water according to claim 2, characterized in that, said scraper comprises a sprocket, a chain, and a scraper, and the chain is connected to the fixed sprockets at both ends , the mud scraper is fixed on the chain to form an annular mud scraper, one side of the annular mud scraper extends into the gap of the spiral disk of the disk separator and clings to the disk, with the rotation of the disk separator , the scraper moves horizontally under the push of the spiral disk, thereby driving the sprocket to rotate, that is, the annular scraper rolls with the rotation of the disk separator.