Caprolactam industrial wastewater treatment method and system

Abstract

The present invention relates to the technical field of industrial wastewater treatment, and specifically provides a method and system for treating caprolactam industrial wastewater. The method includes "pretreatment + wet catalytic oxidation (CWO) + reaction tank treatment + inclined tube sedimentation / ultrafiltration + targeted adsorption + stripping tower treatment + continuous flow membrane bioreactor (CFBR)", and is provided with a catalyst recovery system. The method not only treats the wastewater generated in the caprolactam production process, but also recycles the catalyst of the wet catalytic oxidation and the heat of the system, and the entire process is simple, stable in operation, and highly automated.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and specifically provides a method and system for treating caprolactam industrial wastewater. Background Art

[0002] Caprolactam is an important organic chemical raw material and a raw material product in the nylon industry chain. It has a melting point of about 70°C and is mainly transparent in liquid form with the smell of mint and acetone. The main use of caprolactam liquid is to generate PA6 chips through polymerization, accounting for 93% of downstream applications, and a small amount is used to manufacture pharmaceutical intermediates.

[0003] The industrial production of caprolactam in my country began in the late 1950s, and two sets of caprolactam production technologies from DSM of the Netherlands were introduced in the early 1990s. Later, with the research and development optimization of domestic caprolactam production technology and the growth of national economic construction and demand, the production of caprolactam in my country has developed rapidly. After 2010, benefiting from the continuous development of my country's economy and the domestic textile industry, the demand for domestic nylon industry has increased, which has promoted the continuous expansion of the caprolactam industry. The production scale of the industry has continued to grow, and the production capacity has increased rapidly, from 490,000 tons in 2010 to 5.69 million tons in 2022. At present, China has become the world's largest producer of caprolactam, and by 2022, China's caprolactam production capacity will account for 63.22% of the world's total.

[0004] The production of 1 ton of caprolactam will generate 4 to 7 tons of wastewater, whose COD (chemical oxygen demand) is usually more than 10,000, and contains high concentrations of sodium sulfate and ammonium sulfate, as well as a small amount of catalyst. Due to the long production process of caprolactam, there are many production stages and many by-products. In the rearrangement stage, the waste liquid produced contains pollutants such as caprolactam and ammonium sulfate; in the refining stage, benzene extraction and alkali washing are used, and the waste liquid produced contains water, caprolactam, sodium salt, etc. These two waste liquids have complex components, high toxicity, and belong to high-salt organic wastewater. They are production waste liquids that are difficult to treat in the current petrochemical industry.

[0005] Due to the presence of various wastes in caprolactam wastewater, including high concentrations of sodium sulfate and a small amount of catalysts, it is difficult for microorganisms to survive when using traditional biochemical methods for treatment, and the efficiency of biological treatment is low. Although Fenton oxidation, ozone oxidation, salting out, and high-temperature incineration methods have achieved a certain degree of treatment effect, they have the problems of high energy consumption and high cost, and even secondary pollution that is more difficult to treat.

[0006] Therefore, it is urgent to develop technologies with low treatment costs and good treatment effects to achieve effective treatment of caprolactam wastewater and the recycling of resources and energy, so as to make the treatment process more reasonable, more environmentally friendly, and more effective, thereby safeguarding the large-scale development of caprolactam.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The first object of the present invention is to provide a method for treating caprolactam industrial wastewater.

[0009] The second object of the present invention is to provide a system for treating caprolactam industrial wastewater.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] The present invention provides a method for treating caprolactam industrial wastewater, which comprises the following steps:

[0012] S1 pretreatment: After the wastewater enters the pretreatment system, SS is first removed, and then the pH of the wastewater is adjusted to 2-4;

[0013] S2 wet catalytic oxidation: a homogeneous catalyst system is used, the catalyst is Cu-Fe-Mn-X composite salt, COD and ammonia nitrogen are removed from the wastewater through wet catalytic oxidation reaction, and the effluent enters the reaction tank treatment system;

[0014] S3 reaction tank treatment: adjust the pH of the effluent from the wet catalytic oxidation system to 8-10, convert the Cu-Fe-Mn-X composite salt into Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 Sedimentation and stirring are performed, and the effluent enters the inclined tube sedimentation or ultrafiltration system;

[0015] S4 inclined tube sedimentation or ultrafiltration: After sufficient sedimentation in the inclined tube, the bottom sediment enters the catalyst recovery system, and the supernatant enters the targeted adsorption system; or

[0016] After being intercepted by the ultrafiltration membrane, the concentrated water enters the catalyst recovery system, and the produced water enters the targeted adsorption system;

[0017] S5 targeted adsorption: After the supernatant of the inclined tube sedimentation system or the produced water of the ultrafiltration system is subjected to targeted adsorption, the residual catalyst remains on the adsorption column, and the column liquid enters the stripping tower treatment system;

[0018] S6 stripping tower treatment: using the steam generated by the waste heat of the wet catalytic oxidation system as a heat source, the wastewater is heated to 90-100°C, the pH of the wastewater is adjusted to 10-12, ammonia in the wastewater is removed, and the ammonia is absorbed by clean water to produce fertilizers. The effluent from the stripping tower treatment enters the CFBR system;

[0019] S7 CFBR: By inoculating and domesticating salt-tolerant microorganisms and setting up fixed-bed fillers in the biochemical pool that are conducive to the growth and reproduction of microorganisms, organic matter and ammonia nitrogen are removed in a high-salt environment, and the effluent from the CFBR is discharged into the park sewage treatment plant.

[0020] The present invention also provides a treatment system for caprolactam industrial wastewater, which comprises a pretreatment system, a wet catalytic oxidation system, a reaction tank treatment system, an inclined tube sedimentation or ultrafiltration system, a targeted adsorption system, a stripping tower treatment system and a CFBR system; the water outlet side of the pretreatment system is connected to the wet catalytic oxidation system, the water outlet side of the wet catalytic oxidation system is connected to the reaction tank treatment system after passing through a gas-liquid separator, the wet catalytic oxidation system heats water to provide steam for the stripping tower treatment system, the water outlet side of the reaction tank treatment system is connected to the inclined tube sedimentation or ultrafiltration system, the first water outlet side of the inclined tube sedimentation or ultrafiltration system is connected to the targeted adsorption system, the second water outlet side is connected to the catalyst recovery system, the water outlet side of the targeted adsorption system is connected to the stripping tower treatment system, the water outlet side of the stripping tower treatment system is connected to the CFBR system, and the gas outlet side of the stripping tower treatment system is connected to an ammonia absorption tower;

[0021] The device of the wet catalytic oxidation system is provided with a fixed bed, which is filled with a metal oxidant filler of φ4 to 10 mm as an enhanced disperser, and the filling density is 1.0 to 1.5 g / mL;

[0022] The diameter of the inclined tube in the inclined tube sedimentation or ultrafiltration system is 50mm-100mm, the thickness is not less than 1mm, the inclination angle is 45°-60°, and the material of the inclined tube is PP material; the ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5-8mm, the length of the membrane tube is 3-4m, the membrane pore size is 20-50nm, and the membrane material is PVDF;

[0023] The adsorbent model filled in the targeted adsorption system is CH-90Na;

[0024] The gap between the plates in the stripper treatment system is about 500 mm, and the contact material of the stripper treatment is duplex stainless steel;

[0025] In the CFBR system, a fixed bed filler is set in the biochemical pool to facilitate the growth and reproduction of microorganisms. The fixed bed filler is made of fiber textiles and is cloth-like in shape. The specific surface area of ​​the filler is 4000-5000m 2 / m 3 , the biochemical pool has a multi-stage structure.

[0026] Compared with the prior art, the technical effects of the present invention are:

[0027] The caprolactam wastewater treatment method of the present invention can treat organic matter in caprolactam wastewater under a high-salt environment, and the treatment methods are mainly wet catalytic oxidation (CWO) and CFBR processes. A fixed bed is provided in the wet catalytic oxidation process, and at the same time, under the conditions of high temperature, high pressure, catalyst, and oxidant, it is ensured that the wet catalytic oxidation can efficiently remove organic matter, especially difficult-to-degrade organic matter, and the COD removal rate can reach more than 50%, and the macromolecular organic matter is oxidized into small molecular organic matter, which is beneficial to the subsequent oxidative decomposition of the CFBR process. Due to the long hydraulic retention time, the CFBR process is provided with a fixed bed fiber filler, and salt-tolerant microorganisms are domesticated and inoculated, which can oxidize and decompose organic matter in a high-salt environment, and the COD removal rate can reach more than 80%, ensuring that the effluent COD meets the standard.

[0028] At the same time, the stripping process separates the ammonia nitrogen in the wastewater in the form of ammonia gas and absorbs it into ammonium ions with water. Due to the high purity and concentration of ammonium ions, it can be used as a raw material for producing fertilizers. It not only treats the ammonia nitrogen in the wastewater, but also turns waste into treasure and realizes resource utilization.

[0029] In addition, the catalyst recovery adopts the "candle filtration + acid dissolution" process to achieve the recovery of wet catalytic oxidation catalyst. First, the bottom precipitate after precipitation or the concentrated water intercepted by the ultrafiltration membrane is separated by candle filtration to obtain the filtrate and Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 Solid, then to Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 Add acid such as sulfuric acid to the solid to form CuSO 4 、FeSO 4 、MnSO 4 The solution is returned to the front-end CWO system as its catalyst. The entire process of candle filtration, drying, filter cake shedding, backwashing, etc. is fully automatic, the filter cake thickness is adjustable, the catalyst recovery process is short, simple, easy, stable and reliable, the catalyst recovery cost is low, and the recovery rate is as high as 99%, which can effectively avoid catalyst poisoning and waste of subsequent treatment processes and resources.

[0030] In addition, the processing system that implements the processing method of the present invention is suitable for multiple energy recovery and utilization systems, and can achieve the recovery and utilization of more than 90% of waste heat, which can not only reduce the processing cost, but also avoid problems such as thermal pollution. It mainly includes the following nodes: (1) The heat of the steam and high-temperature liquid from CWO is recovered by boiler water. The boiler water is vaporized into steam after heat exchange and used for heating, power generation and use in the plant area by the stripping tower; (2) The steam and high-temperature liquid from CWO are used to preheat the inlet water of CWO after heat exchange with boiler water, and the inlet water is preheated from room temperature to above 200°C; (3) The steam and high-temperature liquid from CWO are further heat exchanged with cold water and cooling water in the plant area after heat exchange with the inlet water of CWO. After heat exchange, the cold water becomes hot water. It can be used as hot water supply within the plant; (4) The steam and high-temperature liquid from the CWO are heat exchanged with cold water and cooling water, and then separated into separation gas and separation liquid through a separator. The separation gas is discharged after energy recovery, and the recovered energy can be used to generate power for the air compressor supporting the CWO, thereby reducing operating costs. The separation liquid is treated by "reaction tank treatment + inclined tube sedimentation or ultrafiltration + targeted adsorption" and then enters the stripping tower for treatment; (5) The water discharged from the stripping tower is cooled by cooling water and then enters the CFBR process to ensure the optimal reaction temperature of the CFBR process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The various technical features of the present invention and the relationship between them are further explained below with reference to the accompanying drawings. The accompanying drawings are exemplary, and some technical features are not shown in actual proportion. In addition, some drawings may omit technical features that are commonly used in the technical field to which the present invention belongs and are not essential for understanding and implementing the present invention, or additionally show technical features that are not essential for understanding and implementing the present invention. In other words, the combination of the various technical features shown in the accompanying drawings is not used to limit the present invention. In addition, in the full text of the present invention, the same figure numerals refer to the same content. The specific description of the drawings is as follows:

[0032] Figure 1 A schematic diagram of the candle filter of the present invention is shown;

[0033] Figure 2The process flow chart of the treatment and resource utilization of caprolactam wastewater of the present invention is shown; wherein, (1) water inlet; (2) pretreatment system; (3) gas-liquid mixer; (4) wet catalytic oxidation; (5) air compressor; (6) gas tank; (7) heat exchanger; (8) boiler water; (9) steam; (10) cold water; (11) hot water; (12) cooling water supply water; (13) cooling water return water; (14) gas-liquid separator; (15) energy recovery device; (16) waste gas; (17) reaction tank treatment; (18) inclined tube sedimentation / ultrafiltration; (19) candle filter; (20) dissolution tank; (21) targeted adsorption; (22) stripping tower treatment; (23) boiler feed water; (24) ammonia absorption tower; (25) fertilizer production; (26) cooling water supply water; (27) cooling water return water; (28) CFBR system; (29) nanotube discharge. DETAILED DESCRIPTION

[0034] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0035] Suspended solids (SS) refers to solid matter suspended in water, including organic and inorganic particles, such as inorganic and organic matter that is difficult to dissolve in water, mud, clay, microorganisms, etc. The content of suspended solids in water is one of the indicators to measure the degree of water pollution.

[0036] Catalytic Wet Oxidation Process (CWO) is a deep treatment technology for wastewater. Under certain temperature and pressure conditions, in a reactor filled with a special fixed catalyst, the wastewater is kept in a liquid state. Under the action of oxygen (air), the principle of catalytic oxidation is used to perform deep treatment (contact time 10min-2.0h) on COD, TOC (total organic carbon), ammonia, cyanide and other pollutants in high-concentration industrial organic wastewater at one time, converting them into CO 2 、N 2 and water and other harmless components, and at the same time deodorize, decolorize and sterilize, so as to achieve the purpose of purifying wastewater.

[0037] Continuous Filter BioReactor (CFBR): A continuous flow membrane bioreactor system is formed by setting a fixed bed filler that is conducive to the growth and reproduction of microorganisms in the biochemical pool, dividing the biochemical pool into several to more than ten sections.

[0038] Cu-Fe-Mn-X composite salt refers to a mixture obtained by mixing industrial-grade copper salt, ferrous salt and manganese salt in a certain proportion, such as copper sulfate, ferrous sulfate and manganese sulfate, copper nitrate, ferrous nitrate and manganese nitrate, or copper chloride, ferrous chloride and manganese chloride.

[0039] The present invention discloses a method for treating and recycling caprolactam wastewater, the main process or procedure of which includes "pretreatment + wet catalytic oxidation (CWO) + reaction tank treatment + inclined tube sedimentation or ultrafiltration + targeted adsorption + stripping tower treatment + continuous flow membrane bioreactor (CFBR)", and a catalyst recovery system is provided. The method not only treats the wastewater generated in the caprolactam production process, but also recycles the catalyst of the wet catalytic oxidation and the heat of the system, and the whole process is simple, stable in operation, and highly automated.

[0040] The treatment method and system provided by the present invention are suitable for treating high-salt and high-organic wastewater generated by various caprolactam production processes, such as ammoximation technology, hydroxylamine technology, etc.

[0041] For the pretreatment system, the suspended solids (SS) in the wastewater are first removed by using a bag filter, and then an acid (such as H 2 SO 4 , HNO 3 or HCl) to adjust the pH of the wastewater to 2-4. The filtration accuracy of the bag filter is preferably 1-5 μm, and the mass percentage concentration of the acid is 10%-50%. The pretreated wastewater enters the wet catalytic oxidation system.

[0042] It should be noted that each step in the treatment method of the present invention (for example, acid adjustment of wastewater pH in S1, dissolution of Cu(OH) in the catalyst recovery step in S4) 2 、Fe(OH) 2 、Mn(OH) 2 The selection of acid in the wet catalytic oxidation system is related to the type of catalyst composite salt used in the wet catalytic oxidation system. For example, if a catalyst in the form of sulfate is used, sulfuric acid is used as the acid; if a catalyst in the form of nitrate is used, nitric acid is used as the acid.

[0043] For the wet catalytic oxidation system, a homogeneous catalyst system is used, and the catalyst is a Cu-Fe-Mn-X composite salt system. Through the wet catalytic oxidation reaction, COD and ammonia nitrogen in the wastewater are removed, and the effluent enters the reaction tank for treatment. In order to achieve this purpose, specifically, the pretreated wastewater and the oxidant (air or oxygen, the oxygen concentration under oxygen-enriched conditions can reach 40% to 90%) are mixed through a gas-liquid mixer and enter the wet catalytic oxidation system. The reaction temperature of the wet catalytic oxidation reaction is 200°C to 300°C, preferably 250°C to 300°C, the reaction pressure is 3 to 10MPa, preferably 5 to 10MPa, and the dosage is 1% to 5%. The catalyst can be obtained by dissolving industrial-grade copper sulfate, ferrous sulfate, and manganese sulfate in a certain proportion, and the content of each catalyst component is regularly detected during the reaction. The mass concentration ratio of Cu-Fe-Mn in the Cu-Fe-Mn-X composite salt is preferably 1:0.2:0.01 to 1:0.85:0.05, the catalytic oxidation time is preferably 2 to 4 hours, and the liquid contact material of the device is preferably duplex stainless steel. Furthermore, a fixed bed is provided in the wet catalytic oxidation device, and a metal oxidant filler of φ4 to 10 mm is filled as a reinforcing disperser with a filling density of 1.0 to 1.5 g / mL to increase the contact area between air or oxygen and water, and at the same time play a catalytic role, and the metal oxidant is preferably Ti8 alloy.

[0044] For the reaction tank treatment system, add alkali (such as NaOH) to adjust the pH of the effluent from the wet catalytic oxidation to 8-10, and convert the Cu-Fe-Mn-X composite salt into Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 After precipitation and stirring, the mixture enters the inclined tube precipitation or ultrafiltration system. The mass percentage concentration of the alkali solution is 5% to 50%, the speed of the reaction stirring in the reaction tank is 40 to 50 rpm, and the reaction time is 20 to 30 minutes.

[0045] For the inclined tube sedimentation or ultrafiltration system, this can be an inclined tube sedimentation system or an ultrafiltration system. After sufficient sedimentation in the inclined tube sedimentation system, the bottom sediment enters the catalyst recovery system, and the supernatant enters the targeted adsorption system. After being intercepted by the ultrafiltration membrane of the ultrafiltration system, the concentrated water reaches a certain concentration and enters the catalyst recovery system, and the produced water enters the targeted adsorption system.

[0046] When an inclined tube sedimentation tank is used, the diameter of the inclined tube is 50 mm to 100 mm, the thickness is not less than 1 mm, the inclination angle is 45 to 60°, the material is PP material, and the sedimentation time is 0.5 to 1.5 hours, preferably 1 hour.

[0047] When an ultrafiltration system is used, tubular ultrafiltration is used, the inner diameter of the membrane tube is 5-8mm, preferably 8mm, the length of the membrane tube is 3-4m, the membrane pore size is 20-50nm, the membrane material is PVDF, and when the SS of the concentrated water reaches 40g / L, it is discharged into the catalyst recovery system.

[0048] For the targeted adsorption system, after the supernatant of the inclined tube sedimentation or the produced water of the ultrafiltration is subjected to targeted adsorption, the residual catalyst remains on the adsorption column, and the column liquid enters the stripping tower treatment system. After adsorption saturation, the adsorption column is regenerated, and the regenerated liquid returns to the front-end reaction tank for treatment. Specifically, 5% to 10% H 2 SO 4 or HNO 3 Adjust the pH of the supernatant of the inclined tube sedimentation or the ultrafiltration water to 3-5. The adsorbent model for targeted adsorption filling is CH-90Na, the working flow rate is 10BV / H, and the saturated adsorption capacity is about 50-100g / L. When the adsorption is saturated, first use 5%-10% H 2 SO 4 , HNO 3 Or HCl analysis, flow rate is 4-5BV / H, time is 30-45min, dosage is 2.5-4BV. Then use pure water or soft water for backwashing, backwashing flow rate is 5-10BV / H, backwashing time is 30-45min. Finally, use 2-3BV (bed volume) of 5%-10% NaOH solution for transformation, transformation flow rate is 4-5BV / H, time is 30-45min. Acid and alkali are recycled, when the acid concentration of the analytical solution is less than 1%, it is discharged to the reaction tank for treatment and recovery of the catalyst. When the NaOH concentration is lower than 1%, add NaOH and continue to use.

[0049] For the stripping tower treatment system, the steam generated by recovering the waste heat of the CWO system is used as a heat source to heat the column liquid wastewater after targeted adsorption to 90-100°C, and alkali (such as NaOH) is added to adjust the pH of the wastewater to 10-12, and the ammonia in the wastewater is removed. After being absorbed by clean water, it is used to produce fertilizers, and the water treated by the stripping tower enters the CFBR system. Furthermore, the gap between the stripping tower treatment plates is about 500mm, and the liquid contact material is duplex stainless steel. The temperature of the steam is 200°C to 220°C, and the pressure is 1-1.5MPa. The concentration of the alkali (such as NaOH) is 5% to 10%, and the ammonium ion concentration after the clean water absorbs ammonia is 300-500kg / m 3 .

[0050] The above-mentioned method of recovering ammonia is mature and reliable, with low recovery cost and high purity. It can not only save resources, create higher profits, realize resource utilization, but also avoid environmental pollution and other problems.

[0051] For the continuous flow membrane bioreactor (CFBR) system: conventional biochemical pool treatment in the art can be used, for example, by inoculating and taming salt-tolerant microorganisms (such as halophilic actinomycetes), and setting up fixed bed fillers in the biochemical pool that are conducive to the growth and reproduction of microorganisms, so as to achieve the purpose of removing organic matter and ammonia nitrogen in a high-salt environment, and the CFBR effluent is discharged into the park sewage treatment plant. Furthermore, the hydraulic retention time of CFBR is 36 to 54 hours, the dissolved oxygen is 0.5 to 3 ppm, preferably 1.5 to 2.5 ppm, and the temperature is 25 to 35 ° C. The fixed bed filler is made of fiber textiles and has a cloth-like shape. The specific surface area of ​​the filler is 4000 to 5000m 2 / m 3 , 2 to 4 times the microorganisms can be attached to the filler per unit weight, and there is no need to set up sludge return. The filler sets the biochemical pool into a multi-stage structure, and reduces the amount of excess sludge produced according to the food chain effect and autotrophic action, and the excess sludge reduction is more than 70%. Salt-tolerant microorganisms are formed through natural domestication or inoculation.

[0052] For the catalyst recovery system, the "candle filtration + acid dissolution" process can be used to separate the filtrate and Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 Solid, Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 Solid acid addition (eg H 2 SO 4 , HNO 3 Or HCl) is dissolved to form a Cu-Fe-Mn-X composite salt solution, which is returned to the front-end CWO system as its catalyst, and the filtrate is returned to the reaction tank for treatment. The catalyst recovery rate is above 99%.

[0053] Candle filtration includes a central tube (clear liquid collection tube), a filter tube (as a support for the filter medium), a filter medium, and a collection chamber. Each group of central tubes is composed of 7 thin tubes (1 central tube and 6 ring central tubes). The outer ring of the central tube surrounds 6 filter tubes, and the outer layer of the 6 filter tubes is wrapped with a layer of filter medium. The diameter of the central tube and the filter tube is 10 to 25 mm, and the length is 500 mm to 3000 mm, preferably 630 mm to 2500 mm. Holes with a diameter of 1 to 2 mm are arranged at intervals on each central tube and filter tube. The filter medium uses radially woven felt cloth or a membrane with a micropore diameter of less than 1 μm. The seamless radially woven filter medium is tightly clamped at both ends of the filter unit to withstand the axial recoil pressure. The collection chamber is at the port of the filter tube and is used to connect the central tube and the filter tube.

[0054] Furthermore, the working pressure of candle filtration is 0.1-0.5MPa, preferably 0.3-0.5MPa, the liquid-solid content after filtration is ≤5ppm, the filter cake thickness can reach 3-50mm, the dryness of the filter cake is adjustable, and it can be dried to a residual moisture content of less than 50% by hot or cold air or steam. The entire filtering, drying, filter cake shedding, backwashing and other processes are carried out automatically.

[0055] For acid dissolution processes, the acid (e.g. H 2 SO 4 , HNO 3 or HCl) with a mass percentage concentration of 10% to 50%, fully stir during the dissolution process, control the pH below 2, and ensure that Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 The precipitate dissolved completely.

[0056] The catalyst recovery method has a short process, strong practicability and high recovery rate (>99%), and the recovered catalyst can be used for front-end wet catalytic oxidation, thereby avoiding the catalyst from entering the environment to cause catalyst pollution and waste of resources.

[0057] The present invention provides a caprolactam industrial wastewater treatment system, comprising a pretreatment system, a wet catalytic oxidation system, a reaction tank treatment system, an inclined tube sedimentation or ultrafiltration system, a targeted adsorption system, a stripping tower treatment system and a CFBR system. Specifically, Figure 2As shown, the outlet side of the pretreatment system (2) is connected to the wet catalytic oxidation system (4), and the pretreated wastewater and the oxidant in the gas tank (6) are treated by the gas-liquid mixer (3) and enter the wet catalytic oxidation system (4) together. The device of the wet catalytic oxidation system (4) is provided with a fixed bed, which is filled with a metal oxidant filler of φ4 to 10 mm as a reinforced disperser, and the filling density is 1.0 to 1.5 g / mL. The outlet side of the wet catalytic oxidation system (4) is connected to the reaction tank treatment system (17) after passing through the gas-liquid separator (14), and the wastewater enters the reaction tank treatment system (17). At the same time, the wet catalytic oxidation system (4) heats water (8) to provide steam (9) for the stripping tower treatment system (22). The gas in the gas-liquid separator (14) passes through the energy recovery device (15) and then discharges the waste gas (16). The outlet side of the reaction tank treatment system (17) is connected to the inclined tube sedimentation or ultrafiltration system (18). The first outlet side of the inclined tube sedimentation or ultrafiltration system (18) is connected to the targeted adsorption system (21), and the second outlet side is connected to the catalyst recovery system (candle filter 19 and dissolution tank 20). The solution in the candle filter (19) enters the reaction tank treatment system (17) again through the first outlet side, and the precipitate in the candle filter (19) enters the dissolution tank (20) through the second outlet side to be dissolved, and the solution obtained by the dissolution tank (20) enters the wet catalytic oxidation system (4) as a regenerated catalyst. The outlet side of the targeted adsorption system (21) is connected to the stripping tower treatment system (22), the outlet side of the stripping tower treatment system (22) is connected to the CFBR system (28), and the outlet side of the stripping tower treatment system (22) is connected to the ammonia absorption tower (24).

[0058] The diameter of the inclined tube in the inclined tube sedimentation or ultrafiltration system is 50mm~100mm, the thickness is not less than 1mm, the inclination angle is 45°~60°, and the material of the inclined tube is PP material; the ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5~8mm, the length of the membrane tube is 3~4m, the membrane pore size is 20~50nm, and the membrane material is PVDF.

[0059] The adsorbent model filled in the targeted adsorption system is CH-90Na;

[0060] The gap between the plates in the stripping tower treatment system is about 500 mm, and the contact material of the stripping tower treatment is duplex stainless steel.

[0061] In the CFBR system, a fixed bed filler is set in the biochemical pool to facilitate the growth and reproduction of microorganisms. The fixed bed filler is made of fiber textiles and is cloth-like in shape. The specific surface area of ​​the filler is 4000-5000m 2 / m 3 , the biochemical pool has a multi-stage structure.

[0062] The schematic diagram of the candle filter is as follows Figure 1As shown, the diameter of each capillary is 10-25 mm, the length is 500 mm-3000 mm, preferably 630 mm-2500 mm, each capillary is spaced with holes of 1-2 mm in diameter, and the filter medium uses radially woven felt cloth or a membrane with a micropore diameter of less than 1 μm. The candle filtration working pressure is 0.1-0.5 MPa, preferably 0.3-0.5 MPa, the liquid-solid content after filtration is ≤5 ppm, the filter cake thickness can reach 3-50 mm, the dryness of the filter cake is adjustable, and it can be dried to a residual moisture content of less than 50% by cold or hot air or steam, and the entire filtering, drying, filter cake shedding, backwashing and other processes are fully automatic.

[0063] In a preferred embodiment, the connections are all made by pipes or a combination of a pump and a pipe.

[0064] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0065] Example 1

[0066] The wastewater produced by a caprolactam industry has a water volume of 33t / h, a measured pH of 4-5, COD of 18000mg / L, ammonia nitrogen of 6000mg / L, and Na 2 SO 4 The content is 10% to 12%, (NH 4 ) 2 SO 4 The content is between 0.4% and 1%.

[0067] Pretreatment: First filter through a 5μm filter bag to remove SS in the wastewater, and then use 10% dilute sulfuric acid to adjust the pH of the wastewater to 2-4.

[0068] Wet catalytic oxidation: The temperature of wet catalytic oxidation was controlled at 270°C, the pressure was 9MPa, the catalyst concentration was 20g / L, the mass concentration ratio of Cu-Fe-Mn was 1:0.3:0.01-1:0.6:0.05, and the filling density of Ti8 alloy was 1.5g / mL. Air was continuously introduced and catalytic oxidation was performed for 2h. After wet catalytic oxidation, the pH of the wastewater was about 6, COD was about 10000mg / L, ammonia nitrogen was about 1200mg / L, and Na + The concentration is about 33.6g / L, SO 4 2- The concentration is about 106.8g / L, NH 4 + The concentration is about 1.2g / L.

[0069] Reaction tank treatment: Add 3m 3 / h or so 30% NaOH solution is added to the reaction tank for treatment, the pH of the wet catalytic oxidation effluent is adjusted to about 8, and the precipitation is fully stirred.

[0070] Ultrafiltration: The diameter of the ultrafiltration membrane tube is 8mm, and the water output of ultrafiltration is about 39.4m 3 / h. Except for the catalyst, the other water quality parameters are basically the same as those of CWO effluent. The ultrafiltration concentrate volume is about 29.86m 3 / h, when the SS of ultrafiltration concentrated water is lower than 40g / L, the concentrated water is returned to the reaction tank for treatment. When the SS of concentrated water is close to 40g / L, it enters the candle filtration.

[0071] Candle filtration: Cu(OH) with a water content of 50% is filtered out 2 、Fe(OH) 2 、Mn(OH) 2 Solid is about 2.39t / h, add 10% dilute H 2 SO 4 After being fully dissolved, it is returned to the wet catalytic oxidation system as a catalyst. The filtrate produced is about 27.47t / h and returned to the front-end reaction tank for treatment.

[0072] Targeted adsorption: Two tanks are used, each with an inner diameter of 1.8m and a height of 3m. The liquid contact part is made of duplex stainless steel. 2 SO 4 Adjust the pH of the ultrafiltration water to 3-5, and the column liquid Cu 2+ , Fe 2+ , Mn 2+ Not detected, COD about 10000mg / L, ammonia nitrogen about 1200mg / L. Targeted adsorption adsorption of 80BV of wastewater to reach saturation, analysis requires 4BV of dilute H 2 SO 4 , to obtain Cu 2+ , Fe 2+ , Mn 2+ The solution, the regenerated liquid of targeted adsorption is returned to the front-end reaction tank for treatment.

[0073] Stripping tower treatment: The stripping tower is equipped with 20 trays, the gap between the trays is 500mm, and the liquid contact part is made of duplex stainless steel. The amount of steam supplied to the stripping tower is about 4200kg / h, the temperature of the steam is 200-220℃, the pressure is 1-1.5MPa, and the wastewater is heated to 95℃. Add 0.85m 3 / h10% NaOH solution, adjust the pH of the wastewater to 10-12, remove the ammonia in the wastewater, and the volume of the ammonia gas is about 100m 3 / h, after absorbing with clean water, 0.21m3 / h NH 4 + The solution is used to produce fertilizers, and the effluent from the stripping tower enters the CFBR system.

[0074] CFBR: The CFBR biochemical pool is divided into 8 sections, each section is equipped with a fixed bed fiber filler. The CFBR effluent pH is 6-8, COD < 500 mg / L, ammonia nitrogen < 5 mg / L, Na + About 49.5g / L, SO 4 2- About 97.4g / L, the effluent is discharged into the park sewage treatment plant. The catalyst recovery efficiency is over 99%.

[0075] Example 2

[0076] The caprolactam production wastewater of a petrochemical industry has a water volume of 23t / h, with a pH value of more than 12, COD of about 4000mg / L, ammonia nitrogen of about 1500mg / L, NaOH content of 8% to 10%, and NH 4 NO 3 The content is between 0.5% and 1.5%.

[0077] Pretreatment: First filter through a 5μm filter bag to remove SS in the wastewater, then use 50% HNO 3 solution to adjust the pH of the wastewater to 2-4.

[0078] Wet catalytic oxidation: The temperature of wet catalytic oxidation was controlled at 270°C, the pressure was 8MPa, the catalyst concentration was 10g / L, the mass concentration ratio of Cu-Fe-Mn was 1:0.2:0.01~1:0.85:0.05, and the filling density of Ti8 alloy was 1.5g / mL. Air was continuously introduced and catalytic oxidation was performed for 2h. After wet catalytic oxidation, the COD of the wastewater was about 2000mg / L, the ammonia nitrogen was about 750mg / L, and the Na + The concentration is about 37.1g / L, NO 3 - The concentration is about 221.6g / L, NH 4 + The concentration is about 1.6g / L.

[0079] Reaction tank treatment: Add 4.73m 3 / h or so 10% NaOH solution is added to the reaction tank for treatment, the pH of the wet catalytic oxidation effluent is adjusted to about 8, and the precipitation is fully stirred.

[0080] Inclined tube sedimentation: The reaction sedimentation system produces about 24.86t / h of sludge, SS is 20g / L, and produces about 39.83t / h of supernatant, and the catalyst concentration is 110mg / L.

[0081] Candle filtration: Cu(OH) with a water content of 50% is filtered out 2 、Fe(OH) 2 、Mn(OH) 2 Solid about 1t / h, add 10% dilute HNO 3 After being fully dissolved, it is returned to the wet catalytic oxidation system as a catalyst. The filtrate produced is about 23.86t / h and returned to the front-end reaction tank for treatment.

[0082] Targeted adsorption: Two tanks are used, each with an inner diameter of 1.6m and a height of 2.6m. The liquid contact part is made of duplex stainless steel. 3 Adjust the pH of the supernatant in the inclined tube to 3-5, and the column liquid Cu 2+ , Fe 2+ , Mn 2+ Not detected, COD about 1600mg / L, ammonia nitrogen about 600mg / L. Targeted adsorption adsorption of 80BV of wastewater to reach saturation, analysis requires 5BV of dilute HNO 3 , to obtain Cu 2+ , Fe 2+ , Mn 2+ The solution, the regenerated liquid of targeted adsorption is returned to the front-end reaction tank for treatment.

[0083] Stripping tower treatment: The stripping tower is equipped with 20 trays, the gap between the trays is 500mm, and the liquid contact part is made of duplex stainless steel. The amount of steam supplied to the stripping tower for treatment is about 3000kg / h, the temperature of the steam is 200-220℃, the pressure is 1-1.5MPa, and the wastewater is heated to 95℃. Add about 1m 3 / h10% NaOH solution, adjust the pH of the wastewater to 10-12, remove the ammonia in the wastewater, and the volume of the ammonia gas is about 93m 3 / h, after absorbing with clean water, 0.19m 3 / h NH 4 + The solution is used to produce fertilizers, and the effluent from the stripping tower enters the CFBR system.

[0084] CFBR: The CFBR biochemical pool is divided into 6 sections, each section is equipped with a fixed bed fiber filler. The CFBR effluent pH is 6-8, COD < 500 mg / L, ammonia nitrogen < 10 mg / L, Na + About 39.1g / L, NO 3 - About 183.4g / L, the effluent is discharged into the park sewage treatment plant. The catalyst recovery efficiency is above 99%.

[0085] Example 3

[0086] In a cyclohexanone-oxime process for producing caprolactam, the water volume was 200 t / h, the pH was 4-5, the COD was 6000 mg / L, the ammonia nitrogen was 700 mg / L, (NH 4 ) 2 The S content is 0.14% and the acetic acid content is 0.56%.

[0087] Pretreatment: First filter through a 5μm filter bag to remove SS in the wastewater, and then use 10% sulfuric acid solution to adjust the pH of the wastewater to 2-4.

[0088] Wet catalytic oxidation: The temperature of wet catalytic oxidation was controlled at 280°C, the pressure was 9MPa, the catalyst concentration was 10g / L, the mass concentration ratio of Cu-Fe-Mn was 1:0.2:0.01-1:0.85:0.05, and the filling density of Ti8 alloy was 1.5g / mL. Air was continuously introduced and catalytic oxidation was performed for 2h. After wet catalytic oxidation, the pH of the wastewater was 6, COD was about 3000mg / L, ammonia nitrogen was about 500mg / L, SO 4 2- The concentration is about 15.1g / L, NH 4 + Concentration is about 522.8mg / L, CH 3 COO - The concentration is approximately 2310 mg / L.

[0089] Reaction tank treatment: Add 5.11m 3 / h 50% NaOH solution is added to the reaction tank for treatment, the pH of the wet catalytic oxidation effluent is adjusted to about 8, and the precipitation is fully stirred.

[0090] Ultrafiltration: The diameter of the ultrafiltration membrane tube is 8mm, and the water output of ultrafiltration is about 213m 3 / h, concentrated water volume is about 79.8m 3 / h, when the SS of ultrafiltration concentrated water is lower than 40g / L, the concentrated water is returned to the reaction tank for treatment. When the SS of concentrated water is close to 40g / L, it enters the candle filtration.

[0091] Candle filtration: Cu(OH) with a water content of 50% is filtered out 2 、Fe(OH) 2 、Mn(OH) 2 The solid is about 6.4t / h, which is fully dissolved by adding 10% dilute sulfuric acid and then returned to the wet catalytic oxidation system as a catalyst. The filtrate produced is 73.4t / h, which is returned to the front-end reaction tank for treatment.

[0092] Targeted adsorption: 12 tanks are used, each with an inner diameter of 1.8m and a height of 3m. The liquid contact part is made of duplex stainless steel. 5% sulfuric acid solution is used to adjust the pH of the ultrafiltration water to 3-5. The column liquid Cu 2+ , Fe 2+, Mn 2+ Not detected, COD about 2900mg / L, ammonia nitrogen about 500mg / L. Targeted adsorption adsorption of 80BV of wastewater to reach saturation, analysis requires 5BV of acetic acid solution, and Cu 2+ , Fe 2+ , Mn 2+ The solution, the regenerated liquid of targeted adsorption is returned to the front-end reaction tank for treatment.

[0093] Stripping tower treatment: Two stripping towers are used, each with 24 trays, the tray gap is 500mm, and the liquid contact part is made of duplex stainless steel. The amount of steam supplied to the stripping tower is about 25,000 kg / h, the steam temperature is 200-220°C, the pressure is 1-1.5 MPa, and the wastewater is heated to 95°C. Add 2.15m 3 / h10% NaOH solution, adjust the pH of the wastewater to 10-12, remove the ammonia in the wastewater, and the volume of the ammonia gas is about 260m 3 / h, after absorbing with clean water, 0.52m 3 / h NH 4 + The solution is used to produce fertilizers, and the effluent from the stripping tower enters the CFBR system.

[0094] CFBR: Two CFBR biochemical pools are used, each of which is divided into 16 sections, and each section is equipped with a fixed bed fiber filler. The CFBR effluent pH is 6-8, COD < 500 mg / L, ammonia nitrogen < 5 mg / L, SO 4 2- About 15.3g / L, Na + About 13.8g / L, the effluent is discharged into the park sewage treatment plant. The catalyst recovery efficiency is over 99%.

[0095] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the technical concept of the present invention, all of which belong to the protection scope of the present invention.

Claims

1. A method for treating caprolactam industrial wastewater, It is characterized in that The method comprises the following steps: S1 pretreatment: After the wastewater enters the pretreatment system, SS is first removed, and then the pH of the wastewater is adjusted to 2-4; S2 wet catalytic oxidation: a homogeneous catalyst system is used, the catalyst is Cu-Fe-Mn-X composite salt, COD and ammonia nitrogen are removed from the wastewater through wet catalytic oxidation reaction, and the effluent enters the reaction tank treatment system; S3 reaction tank treatment: adjust the pH of the effluent from the wet catalytic oxidation system to 8-10, convert the Cu-Fe-Mn-X composite salt into Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 Sedimentation and stirring are performed, and the effluent enters the inclined tube sedimentation or ultrafiltration system; S4 inclined tube sedimentation or ultrafiltration: After sufficient sedimentation in the inclined tube, the bottom sediment enters the catalyst recovery system, and the supernatant enters the targeted adsorption system; or After being intercepted by the ultrafiltration membrane, the concentrated water enters the catalyst recovery system, and the produced water enters the targeted adsorption system; S5 targeted adsorption: After the supernatant of the inclined tube sedimentation system or the produced water of the ultrafiltration system is subjected to targeted adsorption, the residual catalyst remains on the adsorption column, and the column liquid enters the stripping tower treatment system; S6 stripping tower treatment: using the steam generated by the waste heat of the wet catalytic oxidation system as a heat source, the wastewater is heated to 90-100°C, the pH of the wastewater is adjusted to 10-12, ammonia in the wastewater is removed, and the ammonia is absorbed by clean water to produce fertilizers. The effluent from the stripping tower treatment enters the CFBR system; S7 CFBR: By inoculating and domesticating salt-tolerant microorganisms and setting up fixed-bed fillers in the biochemical pool that are conducive to the growth and reproduction of microorganisms, organic matter and ammonia nitrogen are removed in a high-salt environment, and the effluent from the CFBR is discharged into the park sewage treatment plant.

2. The method according to claim 1, It is characterized in that The catalyst recovery step in S4 is: firstly, the filtrate and Cu(OH) are separated by candle filtration. 2 、Fe(OH) 2 、Mn(OH) 2 Solid, then Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 The solid is dissolved with acid to form a Cu-Fe-Mn-X composite salt solution, which is returned to the front-end wet catalytic oxidation system as a catalyst, and the filtrate is returned to the reaction tank for treatment.

3. The method according to claim 2, It is characterized in that The candle filter comprises a central tube, a filter tube, a filter medium and a collection chamber.

4. The method according to claim 3, It is characterized in that The outer circle of the central tube surrounds 6 filter tubes, and the outer layer of the 6 filter tubes is wrapped with a layer of filter medium. The diameter of the central tube and the filter tube is 10-25mm, and the length is 500mm-3000mm. Each central tube and filter tube is spaced with holes with a diameter of 1-2mm.

5. The method according to claim 3, It is characterized in that The filter medium is a radially woven felt cloth or a membrane with a micropore diameter less than 1 μm.

6. The method according to claim 3, It is characterized in that The collecting chamber is at the port of the filter tube and is used to connect the central tube and the filter tube.

7. The method according to claim 2, It is characterized in that The working pressure of the candle filtration is 0.1-0.5 MPa, the liquid-solid content after filtration is ≤5 ppm, and the filter cake thickness is 3-50 mm.

8. The method according to claim 2, It is characterized in that The mass percentage concentration of H2O2 is 10% to 50%. 2 SO 4 , HNO 3 or HCl dissolves Cu(OH) 2 、Fe(OH) 2 、Mn(OH) 2 , control the pH below 2.

9. The method according to any one of claims 1 to 8, It is characterized in that In S1, a bag filter is used to remove SS, and the filtration accuracy of the bag filter is 1-5μm.

10. The method according to any one of claims 1 to 8, It is characterized in that S1 uses H with a mass percentage concentration of 10% to 50%. 2 SO 4 , HNO 3 Or HCl to adjust the pH of the wastewater.

11. The method according to any one of claims 1 to 8, It is characterized in that The oxidant in S2 is air or oxygen, the reaction temperature of wet catalytic oxidation is 200°C to 300°C, the reaction pressure is 3 to 10 MPa, the catalyst dosage is 1% to 5%, and the catalytic oxidation time is 2 to 4 hours.

12. The method according to any one of claims 1 to 8, It is characterized in that The mass concentration ratio of Cu-Fe-Mn in the Cu-Fe-Mn-X composite salt in S2 is 1:0.2:0.01 to 1:0.85:0.

05.

13. The method according to any one of claims 1 to 8, It is characterized in that The wet catalytic oxidation device in S2 is provided with a fixed bed filled with a metal oxidant filler of φ4 to 10 mm as an enhanced disperser with a filling density of 1.0 to 1.5 g / mL.

14. The method according to claim 13, It is characterized in that The metal oxidant is Ti8 alloy.

15. The method according to any one of claims 1 to 8, It is characterized in that The liquid contact material of the wet catalytic oxidation device in S2 is duplex stainless steel.

16. The method according to any one of claims 1 to 8, It is characterized in that In S3, NaOH with a mass percentage concentration of 5% to 50% is used to adjust the pH of the effluent.

17. The method according to any one of claims 1 to 8, It is characterized in that The stirring speed in S3 is 40-50 rpm, and the stirring time is 20-30 min.

18. The method according to any one of claims 1 to 8, It is characterized in that The diameter of the inclined tube in S4 is 50mm~100mm, the thickness is not less than 1mm, and the inclination angle is 45°~60°.

19. The method according to any one of claims 1 to 8, It is characterized in that The precipitation time in S4 is 0.5 to 1.5 h.

20. The method according to any one of claims 1 to 8, It is characterized in that The material of the inclined tube in S4 is PP.

21. The method according to any one of claims 1 to 8, It is characterized in that S4 uses tubular ultrafiltration, with an inner diameter of 5 to 8 mm, a length of 3 to 4 m, a pore size of 20 to 50 nm, and a membrane material of PVDF. When the SS of concentrated water reaches 40 g / L, it is discharged into the catalyst recovery system.

22. The method according to any one of claims 1 to 8, It is characterized in that Before adsorption, S5 was treated with 5% to 10% H 2 SO 4 , HNO 3 Or HCl to adjust the pH of the inclined tube sedimentation supernatant or ultrafiltration water to 3-5.

23. The method according to any one of claims 1 to 8, It is characterized in that The adsorbent model for targeted adsorption filling in S5 is CH-90Na, the working flow rate is 10BV / H, and the saturated adsorption capacity is 50-100g / L.

24. The method according to any one of claims 1 to 8, It is characterized in that After adsorption saturation in S5, the adsorption column is regenerated, and the regenerated liquid returns to the front-end reaction tank for treatment.

25. The method according to claim 24, It is characterized in that Regeneration of the adsorption column includes: after adsorption saturation, first use H2O with a mass percentage concentration of 5% to 10% 2 SO 4 , HNO 3 Or HCl analysis, the flow rate is 4-5BV / H, the time is 30-45min, and the dosage is 2.5-4BV; then use pure water or soft water for backwashing, the backwashing flow rate is 5-10BV / H, and the backwashing time is 30-45min; then use 2-3BV of NaOH solution with a mass percentage concentration of 5%-10%, the transformation flow rate is 4-5BV / H, and the time is 30-45min.

26. The method according to any one of claims 1 to 8, It is characterized in that The gap between the treatment plates of the stripping tower in S6 is 500 mm, the temperature of the steam is 200° C. to 220° C., and the pressure of the steam is 1 to 1.5 MPa.

27. The method according to any one of claims 1 to 8, It is characterized in that In S6, NaOH with a mass percentage concentration of 5% to 10% is used to adjust the pH of the wastewater.

28. The method according to any one of claims 1 to 8, It is characterized in that After the clean water in S6 absorbs ammonia, the ammonium ion concentration is 300-500 kg / m 3 .

29. The method according to any one of claims 1 to 8, It is characterized in that The contact material of the stripping tower in S6 is duplex stainless steel.

30. The method according to any one of claims 1 to 8, It is characterized in that The hydraulic retention time of CFBR in S7 is 36-54h, the dissolved oxygen is 0.5-3ppm, and the temperature is 25-35℃.

31. The method according to any one of claims 1 to 8, It is characterized in that The material of the fixed bed packing in S7 is textile fiber, and its shape is cloth-like, and the specific surface area of ​​the packing is 4000-5000m 2 / m 3 , 2 to 4 times the amount of microorganisms are attached to each unit weight of filler, and there is no need to set up sludge return.

32. The method according to any one of claims 1 to 8, It is characterized in that The filler in S7 sets the biochemical pool into a multi-stage structure, reducing the amount of residual sludge generated based on the food chain effect and autotrophic action, with the reduction of residual sludge exceeding 70%.

33. The method according to any one of claims 1 to 8, It is characterized in that The salt-tolerant microorganisms described in S7 are formed by natural acclimation or inoculation.

34. A caprolactam industrial wastewater treatment system, It is characterized in that The treatment system comprises a pretreatment system, a wet catalytic oxidation system, a reaction tank treatment system, an inclined tube sedimentation or ultrafiltration system, a targeted adsorption system, a stripping tower treatment system and a CFBR system; the water outlet side of the pretreatment system is connected to the wet catalytic oxidation system, the water outlet side of the wet catalytic oxidation system is connected to the reaction tank treatment system after passing through a gas-liquid separator, the wet catalytic oxidation system uses waste heat to heat water to provide steam for the stripping tower treatment system, the water outlet side of the reaction tank treatment system is connected to the inclined tube sedimentation or ultrafiltration system, the first water outlet side of the inclined tube sedimentation or ultrafiltration system is connected to the targeted adsorption system, the second water outlet side is connected to the catalyst recovery system, the water outlet side of the targeted adsorption system is connected to the stripping tower treatment system, the water outlet side of the stripping tower treatment system is connected to the CFBR system, and the gas outlet side of the stripping tower treatment system is connected to an ammonia absorption tower; The device of the wet catalytic oxidation system is provided with a fixed bed, which is filled with a metal oxidant filler of φ4 to 10 mm as an enhanced disperser, and the filling density is 1.0 to 1.5 g / mL; The diameter of the inclined tube in the inclined tube sedimentation or ultrafiltration system is 50mm-100mm, the thickness is not less than 1mm, the inclination angle is 45°-60°, and the material of the inclined tube is PP material; the ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5-8mm, the length of the membrane tube is 3-4m, the membrane pore size is 20-50nm, and the membrane material is PVDF; The adsorbent model filled in the targeted adsorption system is CH-90Na; The gap between the plates in the stripper treatment system is 500 mm, and the contact material of the stripper treatment is duplex stainless steel; In the CFBR system, a fixed bed filler is set in the biochemical pool to facilitate the growth and reproduction of microorganisms. The fixed bed filler is made of fiber textiles and is cloth-like in shape. The specific surface area of ​​the filler is 4000-5000m 2 / m 3 , the biochemical pool has a multi-stage structure.

35. The processing system according to claim 34, It is characterized in that The catalyst recovery system includes a candle filter and a dissolving tank, the first water outlet side of the candle filter is connected to the reaction tank treatment system, the second water outlet side of the candle filter is connected to the dissolving tank, and the water outlet side of the dissolving tank is connected to the wet catalytic oxidation system.

36. A processing system according to claim 34 or 35, It is characterized in that The connections are made by pipes or a combination of pumps and pipes.

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