Device and method for recovering sodium chloride from wastewater in preparation of bonded permanent ferrite magnetic powder

Abstract

The present invention belongs to the technical field of wastewater treatment, and particularly relates to a device and a method for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder. The device and method provided by the present invention utilize the heat generated during the preparation of bonded permanent magnet ferrite magnetic powder to crystallize and concentrate the wastewater, and can separate the salts in the wastewater to obtain utilizable sodium chloride, thereby improving the resource utilization rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a device and method for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder. Background Art

[0002] The permanent magnet ferrite pre-sintered material is a permanent magnet material mainly made of iron red (Fe2O3) / rolled steel scale (Fe3O4) and strontium carbonate (SrCO3), and adding additives such as strontium chloride (SrCl2), silicon dioxide (SiO2), and aluminum oxide (Al2O3) for pre-sintering in a rotary kiln. It can be sintered or bonded to form permanent magnet ferrite device products.

[0003] The bonded permanent magnet ferrite material is an ultra-fine magnetic powder produced from the permanent magnet ferrite pre-sintered material through complex processes such as fine grinding, pickling, water washing, and drying. This type of magnetic powder has a high added value, but a large amount of high-salt wastewater will be generated during the production process. This is because there are three sources of chloride ions in the bonded permanent magnet ferrite material: chloride ions in the raw materials iron red and strontium chloride, chloride ions introduced by using hydrochloric acid during the pickling process, and sodium hydroxide and quicklime are added for acid-base neutralization during the subsequent water washing process, and sodium chloride or calcium chloride will be generated after the reaction. Therefore, high-salt wastewater with a high concentration of sodium chloride is formed. If these wastewaters are directly evaporated and crystallized to form miscellaneous salts and discharged as waste, it will bring a great burden to the environment, and the evaporation and crystallization efficiency is very low, and the recovery rate of miscellaneous salts is also very low. Summary of the Invention

[0004] The purpose of the present invention is to provide a device and method for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder. The device provided by the present invention can realize the treatment of the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder without relying on external heat sources.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a device for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder, which is constructed based on the preparation device of bonded permanent magnet ferrite magnetic powder; according to the flow direction of the wastewater, it includes a filtration-nanofiltration system 1, a concentration system 2, and an evaporation crystallization system 3 connected in sequence;

[0007] The filtration-nanofiltration system 1 includes a first wastewater inlet 1-1, and the first wastewater inlet 1-1 is connected to the wastewater outlet of the bonded permanent magnet ferrite magnetic powder preparation device;

[0008] The filtration-nanofiltration system 1 includes a salt sludge outlet 1-2, a clear water outlet 1-3, and a high-salt wastewater outlet 1-4; the high-salt wastewater outlet 1-4 is connected to the concentration system 2;

[0009] The concentration system 2 includes a second wastewater inlet 2-1 and a heat source inlet 2-2 for concentration. The second wastewater inlet 2-1 is connected to the salt-containing wastewater outlet 1-4; the heat source inlet 2-2 for concentration is connected to the first heat source discharge outlet of the bonded permanent magnet ferrite powder preparation device;

[0010] The concentration system 2 includes a concentrated salt-containing wastewater outlet 2-3 and a concentrated condensate outlet 2-4. The concentrated salt-containing wastewater outlet 2-3 is connected to the evaporation crystallization system 3;

[0011] The evaporation crystallization system 3 includes a third wastewater inlet 3-1 and a heat source inlet 3-2 for crystallization. The third wastewater inlet 3-1 is connected to the concentrated salt-containing wastewater outlet 2-3; the heat source inlet 3-2 for crystallization is connected to the second heat source discharge outlet of the bonded permanent magnet ferrite powder preparation device;

[0012] The evaporation crystallization system 3 includes a sodium chloride outlet 3-3 and a crystallization condensate outlet 3-4.

[0013] Preferably, the preparation device of the bonded permanent magnet ferrite powder includes a rotary kiln L1, a material ball cooling cylinder L2, a ball milling system L3, a pickling system L4, a water washing system L5, a powder drying system L6, and a powder packaging system L7 that are connected in sequence.

[0014] Preferably, the material ball cooling cylinder L2 has a cooling pipeline for introducing cooling water; the water outlet of the cooling pipeline is connected to the heat source inlet 3-2 for crystallization of the evaporation crystallization system 3 for waste heat utilization.

[0015] Preferably, the powder drying system L6 has a heat channel for introducing the heat required for drying the powder; the outlet of the heat channel is connected to the heat source inlet 2-2 for concentration of the concentration system 2 for waste heat utilization.

[0016] Preferably, the first wastewater inlet 1-1 of the filtration-nanofiltration system 1 is connected to the drainage outlet of the water washing system L5.

[0017] Preferably, the clear water outlet 1-3, the concentrated condensate outlet 2-4, and the crystallization condensate outlet 3-4 are respectively connected to the pickling system L4 in the bonded permanent magnet ferrite powder preparation device for water recycling.

[0018] The present invention further provides a method for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite powder. Using the wastewater generated in the preparation of bonded permanent magnet ferrite powder as the salt source, the treatment of the wastewater includes the following steps:

[0019] (1) Filter and nanofiltrate the wastewater to obtain salt sludge, clear water, and salt-containing wastewater;

[0020] (2) Evaporate and concentrate the salt-containing wastewater obtained in step (1) to obtain concentrated salt-containing wastewater and concentrated condensed water;

[0021] (3) Evaporate and crystallize the concentrated salt-containing wastewater obtained in step (3) to obtain recoverable sodium chloride and crystallized condensed water;

[0022] The fresh water obtained in step (1), the concentrated condensed water obtained in step (2), and the crystallized condensed water obtained in step (3) are recycled to the preparation process of bonded permanent magnet ferrite magnetic powder;

[0023] The heat used for evaporation and concentration in step (2) and evaporation and crystallization in step (3) comes from the waste heat in the preparation process of bonded permanent magnet ferrite magnetic powder.

[0024] Preferably, the filtration-nanofiltration treatment includes filtration and nanofiltration carried out in sequence; the filtration includes microfiltration and / or activated carbon filtration.

[0025] Preferably, the pores of the microfiltration membrane used for microfiltration can intercept particles with a size of 0.1 to 1 μm; the particle size of the activated carbon used for activated carbon filtration is 10 ± 5 μm;

[0026] The pore size of the nanofiltration membrane used for nanofiltration is 1 to 2 nm.

[0027] Preferably, the filtration-nanofiltration treatment is carried out under pressure, and the applied pressure is 0.3 to 7 bar.

[0028] The device provided by the present invention uses the heat generated during the preparation of bonded permanent magnet ferrite magnetic powder to crystallize and concentrate the wastewater, and can separate the salt in the wastewater to obtain utilizable sodium chloride, improving the resource utilization rate.

[0029] The device provided by the present invention can also recycle the purified water generated during the wastewater treatment process, improving the utilization rate of water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of the device for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder provided by the present invention;

[0031] In the figure, 1 is a filtration - nanofiltration system, 2 is a concentration system, 3 is an evaporation crystallization system, 1 - 1 is the inlet of the first wastewater, 1 - 2 is the outlet of salt sludge, 1 - 3 is the outlet of clear water, 1 - 4 is the outlet of salt - containing wastewater, 2 - 1 is the inlet of the second wastewater, 2 - 2 is the inlet of heat source for concentration, 2 - 3 is the outlet of concentrated salt - containing wastewater, 2 - 4 is the outlet of concentrated condensate, 3 - 1 is the inlet of the third wastewater, 3 - 2 is the inlet of heat source for crystallization, 3 - 3 is the outlet of sodium chloride, 3 - 4 is the outlet of crystallization condensate, L1 is a rotary kiln, L2 is a material ball cooling cylinder, L3 is a ball - milling system, L4 is a pickling system, L5 is a water - washing system, L6 is a material powder drying system, and L7 is a powder packaging system. Detailed implementation mode

[0032] The present invention provides a device for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite magnetic powder, which is constructed relying on the preparation device of bonded permanent magnet ferrite magnetic powder; according to the flow direction of the wastewater, it includes a filtration - nanofiltration system 1, a concentration system 2, and an evaporation crystallization system 3 connected in sequence;

[0033] The filtration - nanofiltration system 1 includes the inlet of the first wastewater 1 - 1, and the inlet of the first wastewater 1 - 1 is connected to the wastewater outlet of the bonded permanent magnet ferrite magnetic powder preparation device;

[0034] The filtration - nanofiltration system 1 includes the outlet of salt sludge 1 - 2, the outlet of clear water 1 - 3, and the outlet of salt - containing wastewater 1 - 4; the outlet of salt - containing wastewater 1 - 4 is connected to the concentration system 2;

[0035] The concentration system 2 includes the inlet of the second wastewater 2 - 1 and the inlet of heat source for concentration 2 - 2, the inlet of the second wastewater 2 - 1 is connected to the outlet of salt - containing wastewater 1 - 4; the inlet of heat source for concentration 2 - 2 is connected to the first heat source discharge outlet of the bonded permanent magnet ferrite magnetic powder preparation device;

[0036] The concentration system 2 includes the outlet of concentrated salt - containing wastewater 2 - 3 and the outlet of concentrated condensate 2 - 4, the outlet of concentrated salt - containing wastewater 2 - 3 is connected to the evaporation crystallization system 3;

[0037] The evaporation crystallization system 3 includes the inlet of the third wastewater 3 - 1 and the inlet of heat source for crystallization 3 - 2, the inlet of the third wastewater 3 - 1 is connected to the outlet of concentrated salt - containing wastewater 2 - 3; the inlet of heat source for crystallization 3 - 2 is connected to the second heat source discharge outlet of the bonded permanent magnet ferrite magnetic powder preparation device;

[0038] The evaporation crystallization system 3 includes the outlet of sodium chloride 3 - 3 and the outlet of crystallization condensate 3 - 4.

[0039] The device for recovering sodium chloride from the wastewater in the preparation of bonded permanent magnet ferrite powder provided by the present invention is constructed relying on the preparation device of bonded permanent magnet ferrite powder. In the present invention, as Figure 1 shown, the preparation device of the bonded permanent magnet ferrite powder includes a rotary kiln L1, a material ball cooling cylinder L2, a ball milling system L3, a pickling system L4, a water washing system L5, a powder drying system L6, and a powder packaging system L7 that are connected in sequence.

[0040] In the present invention, the rotary kiln L1 is used to pre-burn materials including iron red / rolled steel scale, strontium carbonate, strontium chloride, silicon oxide, and aluminum oxide to obtain a permanent magnet ferrite pre-burned material;

[0041] The material ball cooling cylinder L2 is preferably provided with cooling pipes for introducing cooling water to cool the pre-burned material processed by the rotary kiln; during the cooling process, the cooling water absorbs the heat on the surface of the material ball cooling cylinder and the temperature rises, which can be used as the heat source of the evaporation crystallization system. In the present invention, the water outlet of the cooling pipe is the second heat source discharge port, which is connected to the evaporation crystallization system 3 to realize the recycling of the heat source;

[0042] The ball milling system L3 is used to refine the pre-burned material to obtain ultrafine magnetic powder;

[0043] The pickling system L4 is used to add hydrochloric acid to the ultrafine magnetic powder obtained after ball milling to remove residual substances such as iron red and strontium carbonate in the ultrafine magnetic powder;

[0044] The water washing system L5 is used to add alkaline materials to the acidified material to remove the residual hydrochloric acid and adjust the pH of the liquid to about 7; the alkaline materials include caustic soda and / or quicklime; in the water washing system, a large amount of wastewater containing chlorine salts is generated, and the chlorine salts preferably include ferrous chloride, sodium chloride, calcium chloride, and strontium chloride, etc. In the present invention, a wastewater discharge port is preferably set in the water washing system, and the wastewater discharge port is connected to the first wastewater inlet 1-1 of the filtration-nanofiltration system 1;

[0045] The powder drying system L6 is preferably provided with a heating pipe for introducing the heating medium required for drying the powder to remove the moisture in the ultrafine magnetic powder after water washing; during the drying process, heat transfer occurs between the heating medium and the ultrafine magnetic powder, and the temperature of the heating medium decreases, but still remains at a relatively high temperature, which can be used as the heat source for concentration. In the present invention, the outlet of the heating pipe in the powder drying system (i.e., the first heat source outlet) is preferably connected to the concentration system 2 to realize the utilization of waste heat;

[0046] The powder packaging system is used to package the ultrafine magnetic powder.

[0047] In the present invention, the material ball cooling cylinder L2, pickling system L4, water washing system L5, and material powder drying system L6 in the preparation device of the bonded permanent magnet ferrite magnetic powder are the construction basis of the device for recovering sodium chloride from the wastewater in the preparation of the bonded permanent magnet ferrite magnetic powder according to the present invention. The structure of the device according to the present invention will be described below from the perspective of the wastewater flow direction:

[0048] As Figure 1 shown, the device for recovering sodium chloride from the wastewater in the preparation of the bonded permanent magnet ferrite magnetic powder according to the present invention comprises a filtration - nanofiltration system 1, a concentration system 2, and an evaporation crystallization system 3 which are connected in sequence.

[0049] In the present invention, the filtration - nanofiltration system 1 preferably comprises a filtration component and a nanofiltration component connected in sequence. The filtration component preferably filters by using a microfiltration membrane and / or an activated carbon filtration layer; the pores of the microfiltration membrane preferably can intercept particles with a particle size of 0.1 - 1 μm; the particle size of the activated carbon in the activated carbon filtration layer is preferably 10 ± 5 μm. The present invention preferably removes large - particle impurities in the wastewater through a filtration device to form salt sludge; the filtered liquid material enters the subsequent nanofiltration component; the nanofiltration component preferably is provided with a nanofiltration membrane, and the pore diameter of the nanofiltration membrane is preferably 1 - 2 nm, more preferably 2 nm. The present invention preferably separates the filtered liquid through nanofiltration to obtain clear water and salt - containing wastewater. The salt - containing wastewater refers to the wastewater containing salts of monovalent ions, that is, the wastewater containing sodium chloride.

[0050] In the present invention, the filtration - nanofiltration system 1 comprises a first wastewater inlet 1 - 1, and the first wastewater inlet 1 - 1 is connected to the wastewater outlet of the bonded permanent magnet ferrite magnetic powder preparation device, specifically to the drain outlet of the water washing system L5, for introducing the wastewater into the recovery device; the filtration - nanofiltration system 1 comprises a salt sludge outlet 1 - 2, a clear water outlet 1 - 3, and a salt - containing wastewater outlet 1 - 4; the salt - containing wastewater outlet 1 - 4 is connected to the concentration system 2 for transporting the salt - containing wastewater obtained after nanofiltration; the salt sludge outlet 1 - 2 is preferably connected to a salt sludge receiving device for collecting the separated salt sludge; the clear water outlet 1 - 3 is preferably connected to the pickling system L4 to realize the recycling of the clear water obtained after nanofiltration.

[0051] In the present invention, the concentration system 2 comprises a second wastewater inlet 2 - 1 and a heat source inlet 2 - 2 for concentration. The second wastewater inlet 2 - 1 is connected to the salt - containing wastewater outlet 1 - 4; the heat source inlet 2 - 2 for concentration is connected to the first heat source discharge outlet of the bonded permanent magnet ferrite magnetic powder preparation device, and the remaining heat in the process of preparing the bonded permanent magnet ferrite magnetic powder is transferred for evaporation and concentration, so that part of the water in the salt - containing wastewater is evaporated by heating. The water condensed from the evaporated water vapor can be reused; while the remaining material after concentration is concentrated salt - containing wastewater, and the concentration of the concentrated salt - containing wastewater increases to be high - salt wastewater.

[0052] In the present invention, the heat source inlet 2-2 for concentration is connected to the first heat source outlet of the powder drying system L6, and is used for reusing the remaining heat in the process of preparing the bonded permanent magnet ferrite magnetic powder.

[0053] In the present invention, the concentration system 2 includes a concentrated saline wastewater outlet 2-3 and a concentrated condensed water outlet 2-4. The concentrated saline wastewater outlet 2-3 is connected to the evaporation and crystallization system 3, so that the concentrated saline wastewater enters the next step of evaporation and crystallization to obtain sodium chloride. In the present invention, the concentrated condensed water outlet 2-4 is preferably connected to the pickling system L4, and is used for recycling the concentrated recovered wastewater to the pickling step to realize the recycling of water.

[0054] In the present invention, the evaporation and crystallization system 3 includes a third wastewater inlet 3-1 and a heat source inlet 3-2 for crystallization. The third wastewater inlet 3-1 is connected to the concentrated saline wastewater outlet 2-3, and is used for transporting the concentrated saline wastewater into the evaporation and crystallization system 3; the heat source inlet 3-2 for crystallization is connected to the second heat source discharge outlet of the bonded permanent magnet ferrite magnetic powder preparation device, and is used for introducing the high-temperature cooling water obtained after cooling the pre-sintered material into the evaporation and crystallization system to realize the utilization of waste heat.

[0055] In the present invention, the evaporation and crystallization system 3 includes a sodium chloride outlet 3-3 and a crystallization condensed water outlet 3-4; the sodium chloride outlet 3-3 is used for discharging the sodium chloride precipitated by evaporation and crystallization, and the sodium chloride can be recycled; the crystallization condensed water outlet 3-4 is used for discharging the condensed water after evaporation and crystallization, and the crystallization condensed water outlet 3-4 is preferably connected to the pickling system L4, so that the crystallization condensed water can be recycled.

[0056] In the present invention, a crystallizer is preferably provided in the evaporation and crystallization system, and the structure of the crystallizer preferably includes an externally supplied steam type or a mechanical steam compression type; in the specific embodiment of the present invention, the crystallizer is preferably a forced circulation crystallizer or a DTB crystallizer (draft tube and baffle evaporation crystallizer).

[0057] In the present invention, the filtration-nanofiltration system 1, the concentration system 2 and the evaporation and crystallization system 3 are preferably connected by pipelines, and a pressure pump is preferably provided, so that the wastewater can flow between the various systems. The present invention has no special requirements for the installation position and installation method of the pressure pump. By using a method well-known to those skilled in the art, the normal flow of wastewater and different materials generated in each step can be ensured.

[0058] In the present invention, the connecting pipelines between the filtration - nanofiltration system 1, the concentration system 2, the evaporation crystallization system 3 and the preparation device of bonded permanent magnet ferrite powder are preferably provided with valves for realizing the flow and collection of various materials in the wastewater treatment process. The present invention has no special requirements for the installation position and the number of the valves, and those well - known to those skilled in the art can be adopted.

[0059] The present invention provides a method for recovering sodium chloride from the wastewater generated in the preparation of bonded permanent magnet ferrite powder. Using the wastewater generated in the preparation of bonded permanent magnet ferrite powder as the salt source, the wastewater is treated, and the treatment includes the following steps:

[0060] (1) Subject the wastewater to filtration - nanofiltration treatment to obtain salt sludge, clear water and salt - containing wastewater;

[0061] (2) Evaporate and concentrate the salt - containing wastewater obtained in step (1) to obtain concentrated salt - containing wastewater and concentrated condensed water;

[0062] (3) Evaporate and crystallize the concentrated salt - containing wastewater obtained in step (3) to obtain recoverable sodium chloride and crystallization condensed water;

[0063] Reuse the clear water obtained in step (1), the concentrated condensed water obtained in step (2) and the crystallization condensed water obtained in step (3) in the preparation process of bonded permanent magnet ferrite powder;

[0064] The heat used for evaporation and concentration in step (2) and evaporation and crystallization in step (3) comes from the waste heat in the preparation process of bonded permanent magnet ferrite powder.

[0065] The present invention subjects the wastewater to filtration - nanofiltration treatment to obtain salt sludge, clear water and salt - containing wastewater. In the present invention, the wastewater is the wastewater generated in the preparation of bonded permanent magnet ferrite powder, and the chemical components included in the wastewater preferably include ferrous chloride, sodium chloride, calcium chloride and strontium chloride. The present invention has no special requirements for the chemical content of each component in the wastewater, and any concentration can be used.

[0066] In the present invention, the filtration - nanofiltration treatment includes filtration and nanofiltration carried out in sequence; the filtration preferably includes microfiltration and / or activated carbon filtration. The pores of the microfiltration membrane used for microfiltration preferably can intercept particles with a size of 0.1 - 1 μm, more preferably 0.2 - 0.8 μm, to remove large - particle impurities; the particle size of the activated carbon used for activated carbon filtration is 10 ± 5 μm to fully absorb the particle impurities in the wastewater.

[0067] In the present invention, the pore size of the nanofiltration membrane for nanofiltration is preferably 1 to 2 nm. In the specific implementation process of the present invention, the nanofiltration membrane is preferably the RS8-C type of the Doulomel RS series, the Amestec HSX-NF6 or HSX-NF7XX nanofiltration unit of Emth (Wuxi) Separation Technology Co., Ltd., or the -S series -SR100 series nanofiltration membrane.

[0068] In the present invention, the filtration-nanofiltration treatment is preferably carried out under pressure, and the applied pressure is preferably 0.3 to 7 bar, more preferably 1 to 5 bar.

[0069] In the present invention, after the wastewater is subjected to filtration-nanofiltration treatment, salt sludge, clear water and salt-containing wastewater are separated and generated; the salt sludge is directly discharged; the clear water is preferably used for the pickling step in the process of preparing bonded permanent magnet ferrite magnetic powder.

[0070] After obtaining the salt-containing wastewater, the present invention evaporates and concentrates the salt-containing wastewater to obtain concentrated salt-containing wastewater and concentrated condensed water. In the present invention, the heat for the evaporation and concentration comes from the waste heat in the process of preparing bonded permanent magnet ferrite magnetic powder, specifically the remaining heat after the powder is dried in the process of preparing bonded permanent magnet ferrite magnetic powder. Through evaporation and concentration, part of the water in the salt-containing wastewater is evaporated and removed, and the evaporated water vapor is condensed to obtain concentrated condensed water, and the concentrated condensed water is preferably used for the pickling step in the process of preparing bonded permanent magnet ferrite magnetic powder; the remaining material after evaporation is concentrated salt-containing wastewater.

[0071] After obtaining the concentrated salt-containing wastewater, the present invention evaporates and crystallizes the concentrated salt-containing wastewater to obtain recoverable sodium chloride and crystalline condensed water. In the present invention, the heat for the evaporation and crystallization comes from the waste heat in the process of preparing bonded permanent magnet ferrite magnetic powder, specifically the heat of the pre-sintered material absorbed by the ball material cooling cylinder used in the process of preparing bonded permanent magnet ferrite magnetic powder (the surface temperature of the ball material cooling cylinder reaches 900 °C).

[0072] In the present invention, after the concentrated salt-containing wastewater is heated, sodium chloride solid is precipitated, and the sodium chloride can be recycled. In the present invention, after the concentrated salt-containing wastewater is heated, water vapor is also obtained, and the evaporated water vapor is condensed to obtain crystalline condensed water, and the crystalline condensed water is preferably used for the pickling step in the process of preparing bonded permanent magnet ferrite magnetic powder.

[0073] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all the embodiments. People can also obtain other embodiments without creative efforts based on this embodiment, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An apparatus for recovering sodium chloride from the wastewater in the preparation of bonded permanent ferrite magnetic powder, characterized in that, It is constructed based on the preparation device of bonded permanent magnet ferrite magnetic powder; according to the wastewater flow direction, it includes a filtration - nanofiltration system (1), a concentration system (2) and an evaporation crystallization system (3) connected in sequence; The filtration - nanofiltration system (1) includes a first wastewater inlet (1 - 1), and the first wastewater inlet (1 - 1) is connected to the wastewater outlet of the bonded permanent magnet ferrite magnetic powder preparation device; The filtration - nanofiltration system (1) includes a salt sludge outlet (1 - 2), a clear water outlet (1 - 3) and a salt - containing wastewater outlet (1 - 4); the salt - containing wastewater outlet (1 - 4) is connected to the concentration system (2); The concentration system (2) includes a second wastewater inlet (2 - 1) and a heat source inlet for concentration (2 - 2), and the second wastewater inlet (2 - 1) is connected to the salt - containing wastewater outlet (1 - 4); the heat source inlet for concentration (2 - 2) is connected to the first heat source discharge outlet of the bonded permanent magnet ferrite magnetic powder preparation device; The concentration system (2) includes a concentrated salt - containing wastewater outlet (2 - 3) and a concentrated condensate outlet (2 - 4), and the concentrated salt - containing wastewater outlet (2 - 3) is connected to the evaporation crystallization system (3); The evaporation crystallization system (3) includes a third wastewater inlet (3 - 1) and a heat source inlet for crystallization (3 - 2), and the third wastewater inlet (3 - 1) is connected to the concentrated salt - containing wastewater outlet (2 - 3); the heat source inlet for crystallization (3 - 2) is connected to the second heat source discharge outlet of the bonded permanent magnet ferrite magnetic powder preparation device; The evaporation crystallization system (3) includes a sodium chloride outlet (3 - 3) and a crystallization condensate outlet (3 - 4); The filtration - nanofiltration system (1) includes a filtration component and a nanofiltration component connected in sequence. The filtration component is filtered by a microfiltration membrane and / or an activated carbon filter layer; the pores of the microfiltration membrane can intercept particles with a particle size of 0.1 - 1μm; the particle size of the activated carbon in the activated carbon filter layer is 10 ± 5μm; a nanofiltration membrane is provided in the nanofiltration component, and the pore diameter of the nanofiltration membrane is 1 - 2nm.

2. The apparatus according to claim 1, characterized in that, The preparation device of the bonded permanent magnet ferrite magnetic powder includes a rotary kiln (L1), a material ball cooling cylinder (L2), a ball milling system (L3), a pickling system (L4), a water washing system (L5), a powder drying system (L6) and a powder packaging system (L7) connected in sequence.

3. The apparatus according to claim 2, characterized in that, The material ball cooling cylinder (L2) has a cooling pipeline for introducing cooling water; the water outlet of the cooling pipeline is connected to the heat source inlet for crystallization (3 - 2) of the evaporation crystallization system (3) for waste heat utilization.

4. The apparatus according to claim 2 or 3, characterized in that, The powder drying system (L6) has a heat channel for introducing the heat required for drying the powder; the outlet of the heat channel is connected to the heat source inlet for concentration (2 - 2) of the concentration system (2) for waste heat utilization.

5. The apparatus according to claim 2, characterized in that, The first wastewater inlet (1 - 1) of the filtration - nanofiltration system (1) is connected to the drainage outlet of the water washing system (L5).

6. The apparatus according to claim 2 or 5, characterized in that, The clear water outlet (1-3), the concentrated condensate outlet (2-4), and the crystal condensate outlet (3-4) are respectively connected to the pickling system (L4) in the bonded permanent magnet ferrite magnetic powder preparation device to realize the recycling of water.

7. A method for recovering sodium chloride from the wastewater in the preparation of bonded permanent ferrite magnetic powder, using the wastewater generated in the preparation of bonded permanent ferrite magnetic powder as the salt source, and the treatment of the wastewater includes the following steps: (1) Filter and nanofiltrate the wastewater to obtain salt sludge, clear water, and salt-containing wastewater; (2) Evaporate and concentrate the salt-containing wastewater obtained in step (1) to obtain concentrated salt-containing wastewater and concentrated condensate; (3) Evaporate and crystallize the concentrated salt-containing wastewater obtained in step (3) to obtain recoverable sodium chloride and crystal condensate; The clear water obtained in step (1), the concentrated condensate obtained in step (2), and the crystal condensate obtained in step (3) are recycled to the preparation process of bonded permanent magnet ferrite magnetic powder; The heat used for evaporation and concentration in step (2) and evaporation and crystallization in step (3) comes from the waste heat in the preparation process of bonded permanent magnet ferrite magnetic powder; The filtration-nanofiltration treatment includes filtration and nanofiltration carried out in sequence; the filtration includes microfiltration and / or activated carbon filtration; the pore size of the microfiltration membrane used for microfiltration can intercept particles of 0.1-1 μm; the particle size of the activated carbon used for activated carbon filtration is 10±5 μm; The pore size of the nanofiltration membrane used for nanofiltration is 1-2 nm.

8. The method according to claim 7, characterized in that, The filtration-nanofiltration treatment is carried out under pressure, and the applied pressure is 0.3-7 bar.

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