Integrated pretreatment system for caprolactam production wastewater by ammoximation method

Abstract

The utility model provides an integrated pretreatment system for caprolactam production wastewater through an ammoximation method, which comprises a tank body, and a nicotinic acid reaction chamber, a Fenton reaction chamber, a coagulation reaction chamber and a pre-precipitation reaction chamber which are communicated in sequence are arranged in the tank body along the wastewater input direction; a water inlet area, a clear water area and a precipitation inclined pipe are arranged in the pre-precipitation reaction chamber, the water inlet area is communicated with the coagulation reaction chamber and is positioned below the precipitation inclined pipe, a sludge hopper is arranged at the bottom of the water inlet area, the clear water area is positioned above the precipitation inclined pipe, and a clear water channel is arranged at the top of the clear water area. According to the integrated pretreatment system for caprolactam production wastewater through the ammoximation method, an integrated combined structure is adopted, the occupied area of the system is reduced, and wastewater treatment is more economical, efficient and stable.

Description

Technical Field

[0001] This utility model belongs to the technical field of industrial wastewater and domestic sewage treatment, and relates to an integrated pretreatment system for caprolactam production wastewater produced by the ammonoxime process. Background Technology

[0002] Polyamide (nylon) synthesis is achieved through a series of reactions involving caprolactam, including ring-opening, addition polymerization, condensation polymerization, exchange, and end-capping. Adipamide production, on the other hand, uses benzene and ammonia as raw materials and is typically achieved using methods such as the caprolactam oxime process. The caprolactam oxime process first involves the condensation reaction of cyclohexanone with hydroxylamine sulfate at 80-110°C to generate cyclohexanone oxime. The separated cyclohexanone oxime is then subjected to Beckmann rearrangement at 80-110°C using fuming sulfuric acid as a catalyst to yield crude caprolactam. The crude caprolactam is then processed through extraction, distillation, and crystallization to obtain high-purity caprolactam. The cyclohexanone used in the caprolactam oxime process can be obtained by hydrogenating phenol to cyclohexanol, followed by dehydrogenation; or by oxidizing cyclohexane in air to generate cyclohexanol and cyclohexanone, with the separated cyclohexanol then undergoing catalytic dehydrogenation to also produce cyclohexanone. Hydroxylamine sulfate is typically obtained through a reaction of sodium nitrite, ammonium nitrite, or ammonium bisulfite; this process is known as the Raschig process. However, the caprolactam oxime process is more complex, produces more byproducts such as ammonium sulfate, and has higher costs for product purification and wastewater treatment.

[0003] Therefore, many caprolactam producers have adopted the ammoniation reaction of cyclohexanone with ammonia and hydrogen peroxide under the catalysis of titanium silicate molecular sieves to directly and selectively prepare cyclohexanone oxime in one step. The reaction has higher conversion rate and selectivity. This process can greatly simplify the production process, significantly reduce equipment investment, and lower production costs, with obvious economic and social benefits. It has gradually become one of the main methods for the synthesis of cyclohexanone oxime.

[0004] Ammonium oxime wastewater mainly originates from the separation of cyclohexanone oxime, the main product of the ammonium oxime reaction, as well as wastewater introduced during the preparation of raw materials hydrogen peroxide and cyclohexanone, and demineralized water produced at the top of the tail gas absorption tower to absorb ammonia and tert-butanol from the tail gas. This wastewater typically enters a wastewater stripping tower to recover most of the toluene and tert-butanol, then enters a wastewater pretreatment unit to reduce COD and increase the B / C ratio, before finally being sent to a wastewater biological treatment unit and advanced treatment unit for centralized processing.

[0005] The main recalcitrant byproducts in the ammonia oxime treatment unit are cyclohexylamine peroxide, cyclohexyl azo dyes, various catalytically generated polymers, and cyclohexyl-N-nitrosamines, which can account for about 5% of the organic matter in the wastewater. Toluene, cyclohexanone oxime, cyclohexanone, and tert-butanol account for about 40-45% of the organic matter in the wastewater. Cyclohexyl azo dyes and cyclohexyl-N-nitrosamines are the main sources of color, while toluene and cyclohexyl-N-nitrosamines are highly toxic to microorganisms. In addition, the ammonia oxime treatment wastewater contains a certain concentration of residual hydrogen peroxide, which needs to be removed before entering the subsequent wastewater biological treatment system.

[0006] However, current treatment processes for caprolactam wastewater from the ammonium oxime process generally employ oxidation to pretreat the cyclohexanone ammonium oxime wastewater, removing components that are toxic and harmful to microorganisms and difficult to biodegrade. This increases the B / C ratio before mixing with other wastewater and then treating it using biological methods (commonly the AO method) or physicochemical methods, as well as advanced treatment, to achieve discharge standards. Pretreatment methods often involve nicotinic acid oxidation or Fenton's reagent oxidation alone, adjusting the pH to 1-5. Nicotinic acid is typically prepared using 10-15% fuming sulfuric acid (the molar ratio of sulfuric acid to sulfur trioxide is generally 0.15-0.2). The advantage of this method is that nicotinic acid is a catalyst used in the subsequent Beckmann rearrangement, and many affiliated phosphate fertilizer plants produce it, thus reducing costs. However, the sulfuric acid oxidation method requires a low pH value and is carried out in a special reaction vessel, which results in high equipment costs. On the other hand, the Fenton reagent method alone requires the addition of H2O2 and ferrous sulfate to the wastewater. Although the Fenton reagent has a high reducing power, the addition of ferrous sulfate increases the salinity of the water, which increases the desalination burden of deep treatments such as zero discharge.

[0007] Therefore, it is necessary to improve the existing wastewater treatment system for caprolactam production via the ammonoxime process. Utility Model Content

[0008] In view of the shortcomings of the prior art described above, the purpose of this utility model is to provide an integrated pretreatment system for caprolactam production wastewater produced by the ammonoxime process. The system has an integrated structure and is more economical, efficient and stable in treatment.

[0009] To achieve the above and other related objectives, this utility model provides an integrated pretreatment system for caprolactam production wastewater produced via the ammonoxime process. The system includes a tank containing a nicotinic acid reaction chamber, a Fenton reaction chamber, a coagulation reaction chamber, and a pre-precipitation reaction chamber, arranged sequentially along the wastewater input direction. The pre-precipitation reaction chamber includes an inlet zone, a clear water zone, and a sedimentation inclined tube. The inlet zone is connected to the coagulation reaction chamber and located below the sedimentation inclined tube. A sludge hopper is located at the bottom of the inlet zone, and the clear water zone is located above the sedimentation inclined tube. A clear water channel is located at the top of the clear water zone.

[0010] Preferably, the nicotinic acid reaction chamber is connected to a water inlet pipe and a nicotinic acid addition pipe, which are respectively connected to the water inlet of the nicotinic acid reaction chamber.

[0011] Preferably, the nicotinic acid reaction chamber is equipped with a first stirrer.

[0012] Preferably, a first pH probe is provided in the nicotinic acid reaction chamber.

[0013] Preferably, the nicotinic acid reaction chamber and the Fenton reaction chamber are separated by a first partition wall, and the first partition wall is provided with a first connecting hole, and the nicotinic acid reaction chamber and the Fenton reaction chamber are connected through the first connecting hole.

[0014] More preferably, the first connecting hole is located at the bottom of the first partition wall.

[0015] Preferably, the Fenton reaction chamber is connected to a ferrous sulfate addition pipe and a hydrogen peroxide addition pipe, which are respectively connected to the water inlet of the Fenton reaction chamber.

[0016] Preferably, the Fenton reaction chamber is equipped with a second stirrer.

[0017] Preferably, a second pH probe is provided in the Fenton reaction chamber.

[0018] Preferably, the Fenton reaction chamber and the coagulation reaction chamber are separated by a second partition wall, and the second partition wall is provided with a second connecting hole, and the Fenton reaction chamber and the coagulation reaction chamber are connected through the second connecting hole.

[0019] More preferably, the second connecting hole is located at the top of the second partition wall.

[0020] Preferably, the coagulation reaction chamber is connected to an alkali addition pipe, a coagulant addition pipe, and a flocculant addition pipe, which are respectively connected to the water inlet of the coagulation reaction chamber.

[0021] Preferably, a third stirrer is provided in the coagulation reaction chamber.

[0022] Preferably, a third pH probe is provided in the coagulation reaction chamber.

[0023] Preferably, the coagulation reaction chamber and the pre-sedimentation reaction chamber are connected by a connecting area. The connecting area is provided with a third partition wall, a first connecting section, a fourth partition wall, a second connecting section, and a fifth partition wall in sequence along the water inlet direction. The third partition wall is provided with a first connecting port. The coagulation reaction chamber is connected to the first connecting section through the first connecting port. The fourth partition wall is provided with a second connecting port. The first connecting section is connected to the second connecting section through the second connecting port. The second connecting section is also connected to the pre-sedimentation reaction chamber.

[0024] More preferably, the coagulation reaction chamber is connected to the inlet end of the first connecting section via a first connecting port, the outlet end of the first connecting section is connected to the inlet end of the second connecting section via a second connecting port, and the outlet end of the second connecting section is connected to the inlet area of ​​the pre-sedimentation reaction chamber.

[0025] Preferably, the sludge hopper is located at the center of the bottom of the water inlet zone, and the diameter of the sludge hopper gradually decreases from top to bottom.

[0026] Preferably, a sludge pump is provided outside the pool body, and the sludge pump is connected to the sludge hopper.

[0027] More preferably, a sludge scraper is provided at the bottom of the water inlet area.

[0028] More preferably, the sludge hopper is provided with a sludge discharge port on its side wall, and the sludge discharge port is connected to the sludge pump via a sludge inlet pipe.

[0029] More preferably, the sludge pump is also connected to a sludge pipe.

[0030] Preferably, the clear water area is connected to a water outlet pipe, which is connected to the water outlet end of the clear water area.

[0031] As described above, this utility model provides an integrated pretreatment system for caprolactam production wastewater produced by the ammonium oxime process. The system mixes the ammonium oxime wastewater and hydrogen peroxide refining wastewater generated during the caprolactam production process and pretreats them. The integrated pretreatment system performs two oxidation steps: nicotinic acid reaction and Fenton's reagent reaction, followed by coagulation and sedimentation to obtain a clarified liquid. It has the following beneficial effects:

[0032] (1) The present invention provides an integrated pretreatment system for caprolactam production wastewater produced by ammoniation oxime process. It can use nicotinic acid and Fenton's reagent as oxidants to oxidize and transform a large amount of recalcitrant organic matter contained in cyclohexanone ammoniation wastewater and hydrogen peroxide refining wastewater. Nicotinic acid can be used as a catalyst for cyclohexanone oxime to convert it into more biodegradable caprolactam. It can also be used as an oxidant to oxidize other organic wastewater. Moreover, nicotinic acid is relatively inexpensive as an oxidant. In addition, nicotinic acid can also be used as an acidity regulator to adjust the pH to a suitable acidity. The Fenton reagent oxidation process utilizes residual hydrogen peroxide in cyclohexanone ammonia oxime wastewater and hydrogen peroxide refining wastewater, while also leveraging the pH conditions required for nicotinic acid oxidation, eliminating the need for additional acid and thus preventing an increase in salt concentration in the wastewater. Fenton's reagent generates a large number of hydroxyl radicals, exhibiting a stronger oxidizing effect on many organic compounds than nicotinic acid. Therefore, using two oxidants to treat cyclohexanone ammonia oxime wastewater and hydrogen peroxide refining wastewater allows for more thorough oxidation of recalcitrant components and more effectively improves the B / C (BOD / COD) ratio, resulting in better COD removal and ensuring the effectiveness of subsequent biological treatment stages. Compared to oxidation processes using a single oxidant, the use of inexpensive nicotinic acid and the utilization of residual hydrogen peroxide in the wastewater significantly reduces the cost of oxidant reagents.

[0033] (2) The present invention provides an integrated pretreatment system for caprolactam production wastewater produced by the ammonoxime process. The integrated combined structure can minimize the system's footprint and save construction costs.

[0034] (3) The integrated pretreatment system for caprolactam production wastewater produced by the ammonoxime process provided by this utility model is more economical, efficient, and stable in wastewater treatment. It has an ingenious structural design and is easy to use, making it very worthy of promotion and application in practice. Attached Figure Description

[0035] Figure 1 The diagram shown is a structural diagram of an integrated pretreatment system for caprolactam production wastewater produced by the ammoniation process according to this utility model.

[0036] Figure Labels

[0037] 1. Nicotinic acid reaction chamber

[0038] 2 Fenton reaction chamber

[0039] 3. Coagulation reaction chamber

[0040] 4. Pre-precipitation reaction chamber

[0041] 51 First mixer

[0042] 52 Second mixer

[0043] 53 Third mixer

[0044] 6. Precipitation Inclined Tube

[0045] 7. Water Inlet Area

[0046] 8. Qingshui District

[0047] 9. Clear Water Canal

[0048] 10 Sludge scrapers

[0049] 11. Water inlet pipe

[0050] 12 First connecting hole

[0051] 13 Second connecting hole

[0052] 14 Connected regions

[0053] 141 Third partition wall

[0054] 142 First Connected Segment

[0055] 143 The fourth partition wall

[0056] 144 Second Connecting Segment

[0057] 145 The Fifth Partition Wall

[0058] 146 First Connecting Port

[0059] 147 Second Connecting Port

[0060] 15 Water outlet pipe

[0061] 16. Mud discharge outlet

[0062] 17 Sludge Pump

[0063] 18 Mud Inlet Pipe

[0064] 19 Sludge Pipe

[0065] 20 Niacin Addition Tubes

[0066] 21 Ferrous sulfate addition tube

[0067] 22 Hydrogen peroxide inlet tube

[0068] 23. Alkali addition tube

[0069] 24 Coagulant Addition Tube

[0070] 25 Flocculant Addition Tube

[0071] 26 First pH probe

[0072] 27 Second pH probe

[0073] 28 Third pH probe

[0074] 29 Sludge bucket

[0075] 30 First partition wall

[0076] 31 Second partition wall Detailed Implementation

[0077] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0078] Please see Figure 1 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of this invention, should still fall within the scope of the disclosed technical content. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of this invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this invention.

[0079] This invention provides an integrated pretreatment system for caprolactam production wastewater produced via the ammoniation process, such as... Figure 1 As shown, the system includes a tank body. Within the tank body, along the wastewater input direction, there are sequentially connected nicotinic acid reaction chamber 1, Fenton reaction chamber 2, coagulation reaction chamber 3, and pre-sedimentation reaction chamber 4. The pre-sedimentation reaction chamber 4 is provided with an inlet zone 7, a clear water zone 8, and a sedimentation inclined tube 6. The inlet zone 7 is connected to the coagulation reaction chamber 3 and is located below the sedimentation inclined tube 6. The bottom of the inlet zone 7 is provided with a sludge hopper 29. The clear water zone 8 is located above the sedimentation inclined tube 6, and the top of the clear water zone 8 is provided with a clear water channel 9.

[0080] In the above system, such as Figure 1 As shown, the nicotinic acid reaction chamber 1 is a nicotinic acid reaction tank.

[0081] In the above system, such as Figure 1 As shown, the nicotinic acid reaction chamber 1 is connected to a water inlet pipe 11 and a nicotinic acid addition pipe 20, which are respectively connected to the water inlet of the nicotinic acid reaction chamber 1. The water inlet pipe 11 is used to input the wastewater to be treated, and the nicotinic acid addition pipe 20 is used to add nicotinic acid to carry out the nicotinic acid reaction.

[0082] The nicotinic acid used is conventionally fuming sulfuric acid. Specifically, the nicotinic acid used in the nicotinic acid reaction is an aqueous solution of fuming sulfuric acid with a mass percentage concentration of 10-15%.

[0083] In one specific implementation, such as Figure 1 As shown, the water inlet pipe 11 and the nicotinic acid addition pipe 20 are respectively connected to the top of the water inlet end of the nicotinic acid reaction chamber 1.

[0084] In the above system, such as Figure 1 As shown, the nicotinic acid reaction chamber 1 is equipped with a first stirrer 51, which is used for stirring during the nicotinic acid reaction.

[0085] In the above system, such as Figure 1 As shown, a first pH probe 26 is installed in the nicotinic acid reaction chamber 1. This probe is used to measure the pH value within the nicotinic acid reaction chamber 1.

[0086] In one specific implementation, such as Figure 1 As shown, the first pH probe 26 is located at the upper part of the water outlet end inside the nicotinic acid reaction chamber 1.

[0087] In the above system, such as Figure 1 As shown, the nicotinic acid reaction chamber 1 and the Fenton reaction chamber 2 are separated by a first partition wall 30. The first partition wall 30 is provided with a first connecting hole 12, and the nicotinic acid reaction chamber 1 and the Fenton reaction chamber 2 are connected through the first connecting hole 12.

[0088] In one specific implementation, such as Figure 1 As shown, the first connecting hole 12 is located at the bottom of the first partition wall 30.

[0089] In the above system, such as Figure 1 As shown, the Fenton reaction chamber 2 is a Fenton reaction cell.

[0090] In the above system, such as Figure 1 As shown, the Fenton reaction chamber 2 is connected to a ferrous sulfate addition pipe 21 and a hydrogen peroxide addition pipe 22, which are respectively connected to the water inlet of the Fenton reaction chamber 2. The ferrous sulfate addition pipe 21 and the hydrogen peroxide addition pipe 22 are used to add ferrous sulfate and hydrogen peroxide, respectively, to carry out the Fenton reaction.

[0091] In one specific implementation, such as Figure 1 As shown, the ferrous sulfate addition tube 21 and the hydrogen peroxide addition tube 22 are respectively connected to the top of the water inlet of the Fenton reaction chamber 2.

[0092] In the above system, such as Figure 1As shown, a second stirrer is provided inside the Fenton reaction chamber 2. This stirrer is used to stir the mixture during the Fenton reaction.

[0093] In the above system, such as Figure 1 As shown, a second pH probe 52 is installed in the Fenton reaction chamber. It is used to measure the pH value inside the Fenton reaction chamber 2.

[0094] In one specific implementation, such as Figure 1 As shown, the second pH probe 52 is located at the upper part of the water outlet end inside the Fenton reaction chamber 2.

[0095] In the above system, such as Figure 1 As shown, the Fenton reaction chamber 2 and the coagulation reaction chamber 3 are separated by a second partition wall 31. The second partition wall 31 is provided with a second connecting hole 13, and the Fenton reaction chamber 2 and the coagulation reaction chamber 3 are connected through the second connecting hole 13.

[0096] In one specific implementation, such as Figure 1 As shown, the second connecting hole 13 is located at the top of the second partition wall 31.

[0097] In the above system, such as Figure 1 As shown, the coagulation reaction chamber 3 is a coagulation reaction tank.

[0098] In the above system, such as Figure 1 As shown, the coagulation reaction chamber 3 is connected to an alkali addition pipe 23, a coagulant addition pipe 24, and a flocculant addition pipe 25, which are respectively connected to the water inlet of the coagulation reaction chamber 3. The alkali addition pipe 23, coagulant addition pipe 24, and flocculant addition pipe 25 are used to add alkali, coagulant, and flocculant, respectively, to carry out the coagulation reaction.

[0099] The alkali mentioned is a alkali commonly used in coagulation reactions, such as sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2), which can be added in solid form or liquid form as an aqueous solution of the alkali.

[0100] The coagulant and flocculant mentioned are those commonly used in coagulation reactions. The coagulant is an aluminum-based or iron-based coagulant, which can be added in solid form or as a liquid aqueous solution. The flocculant is an aluminum-based or iron-based flocculant, which can be added in solid form or as a liquid aqueous solution.

[0101] In one specific implementation, such as Figure 1 As shown, the alkali addition pipe 23, coagulant addition pipe 24, and flocculant addition pipe 25 are respectively connected to the top of the water inlet of the coagulation reaction chamber 3.

[0102] In the above system, such as Figure 1 As shown, a third stirrer 53 is provided in the coagulation reaction chamber 3. It is used to stir during the coagulation reaction.

[0103] In the above system, such as Figure 1 As shown, a third pH probe 28 is installed in the coagulation reaction chamber 3. It is used to measure the pH value inside the coagulation reaction chamber 3.

[0104] In one specific implementation, such as Figure 1 As shown, the third pH probe 28 is located at the upper part of the water outlet end inside the coagulation reaction chamber 3.

[0105] In the above system, such as Figure 1 As shown, the pre-precipitation reaction chamber 4 is a pre-precipitation reaction tank.

[0106] In the above system, such as Figure 1 As shown, the coagulation reaction chamber 3 and the pre-sedimentation reaction chamber 4 are connected by a connecting area 14. The connecting area 14 is provided with a third partition wall 141, a first connecting section 142, a fourth partition wall 143, a second connecting section 144, and a fifth partition wall 145 in sequence along the water inlet direction. The third partition wall 141 is provided with a first connecting port 146. The coagulation reaction chamber 3 is connected to the first connecting section 142 through the first connecting port 146. The fourth partition wall 143 is provided with a second connecting port 147. The first connecting section 142 is connected to the second connecting section 144 through the second connecting port 147. The second connecting section 144 is also connected to the pre-sedimentation reaction chamber 4.

[0107] In one specific implementation, such as Figure 1 As shown, the coagulation reaction chamber 3 is connected to the inlet end of the first connecting section 142 via the first connecting port 146, the outlet end of the first connecting section 142 is connected to the inlet end of the second connecting section 144 via the second connecting port 147, and the outlet end of the second connecting section 144 is connected to the inlet area 7 of the pre-sedimentation reaction chamber 4.

[0108] By setting up the connecting zone 14, the reaction liquid after the coagulation reaction can flow from the coagulation reaction chamber 3 into the water inlet zone 7 of the pre-sedimentation reaction chamber 4, and be evenly distributed laterally on the water inlet section of the pre-sedimentation reaction chamber 3.

[0109] In one specific implementation, such as Figure 1 As shown, the first connecting port 146 is located at the bottom of the third partition wall 141, and the second connecting port 147 is located at the top of the fourth partition wall 143.

[0110] In the above system, such as Figure 1As shown, the sludge hopper 29 is located at the center of the bottom of the water inlet zone 7, and the diameter of the sludge hopper 29 gradually decreases from top to bottom. The sludge hopper 29 is a conventionally used sludge hopper for storing sludge.

[0111] In the above system, such as Figure 1 As shown, a sludge pump 17 is provided outside the tank body, and the sludge pump 17 is connected to the sludge hopper 29. It is used to discharge the sludge accumulated in the sludge hopper 29.

[0112] In one specific implementation, such as Figure 1 As shown, a sludge scraper 10 is provided at the bottom of the water inlet zone 7. The sludge scraper 10 is a conventionally used sludge scraper, used to collect sludge into the sludge hopper 29.

[0113] In one specific implementation, such as Figure 1 As shown, a sludge discharge port 16 is provided on the side wall of the sludge hopper 29, and the sludge discharge port 16 is connected to the sludge pump 17 via a sludge inlet pipe 18. This is used to discharge the pre-treated sludge from the sludge hopper 29 through the sludge inlet pipe 18 under the action of the sludge pump 17.

[0114] In one specific implementation, such as Figure 1 As shown, the sludge pump 17 is also connected to a sludge pipe 19. The sludge pump 17 outputs pretreated sludge through the sludge pipe 19 for sludge dewatering.

[0115] In the above system, such as Figure 1 As shown, the clear water zone 8 is connected to the clear water channel 9.

[0116] In the above system, such as Figure 1 As shown, the clear water zone 8 is connected to a water outlet pipe 15, which is connected to the water outlet end of the clear water zone 8.

[0117] The following is combined Figure 1 This invention describes the specific usage process of an integrated pretreatment system for caprolactam production wastewater produced via the ammonoxime process.

[0118] Operator obtains such Figure 1The integrated pretreatment system for caprolactam production wastewater produced by the ammonium oxime process, as shown, mixes the ammonium oxime wastewater and hydrogen peroxide refining wastewater (containing residual hydrogen peroxide, 2-ethylanthraquinone, heavy aromatics, and trioctyl phosphate, etc.) generated during the ammonium oxime production process. The mixture then enters the nicotinic acid reaction chamber 1 of the integrated pretreatment system through the inlet pipe 11. Nicotinic acid is added through the nicotinic acid addition pipe 20 to initiate the nicotinization reaction. Under acidic conditions, recalcitrant components in the wastewater, such as toluene, tert-butanol, cyclohexanone oxime, cyclohexanone, cyclohexylamine peroxide, cyclohexyl azo, and various polymers produced by catalysis, are first oxidized by nicotinic acid and converted into easily biodegradable organic matter. Furthermore, residual cyclohexanone oxime in the wastewater can be converted into more readily biodegradable caprolactam under the catalytic action of nicotinic acid. The system is stirred by a first stirrer 51, and the pH in the nicotinic acid reaction chamber 1 is measured to be 3-4 by a first pH probe 26.

[0119] Wastewater is introduced into the Fenton reaction chamber 2 through the first connecting hole 12. Ferrous sulfate and hydrogen peroxide are added through the ferrous sulfate addition pipe 21 and the hydrogen peroxide addition pipe 22. In the Fenton reaction chamber 2, the residual hydrogen peroxide in the wastewater and the newly added hydrogen peroxide are converted into hydroxyl radicals under the catalysis of ferrous ions, further oxidizing and decomposing the residual recalcitrant organic components in the wastewater, transforming them into small, easily biodegradable organic pollutants. The B / C ratio of the wastewater is further increased, and the concentration of organic matter is further reduced. The wastewater is stirred by the second stirrer 52, and the pH in the Fenton reaction chamber 2 is measured to be 3-4 by the second pH probe 27.

[0120] Wastewater is introduced into the coagulation reaction chamber 3 through the second connecting hole 13. Alkali, coagulant, and flocculant are added through the alkali addition pipe 23, coagulant addition pipe 24, and flocculant addition pipe 25, respectively, to initiate the coagulation reaction. The added alkali adjusts the pH, and under the action of the added aluminum-based or iron-based coagulant and flocculant, the particulate solids and colloidal substances in the wastewater undergo coagulation to form flocs. The wastewater is stirred by the third stirrer 53, and the pH in the coagulation reaction chamber 3 is measured to be 6-9 by the third pH probe 28.

[0121] The wastewater sequentially enters the inlet zone 7 of the pre-sedimentation reaction chamber 4 through the first connecting port 146, the first connecting section 142, the second connecting port 147, and the second connecting section 144 of the connecting zone 14. Under the action of the sludge scraper 10, the flocs in the wastewater undergo solid-liquid separation in the sedimentation inclined tube 6, and the sludge settles and accumulates in the sludge hopper 29 at the center of the bottom of the inlet zone 7. The clear liquid sequentially passes through the clear water zone 8 and is then output through the outlet pipe 15. Under the action of the sludge pump 17, the pretreated sludge in the sludge hopper 29 is discharged through the sludge discharge port 16 via the sludge inlet pipe 18 and the sludge pipe 19 for sludge dewatering.

[0122] In summary, the integrated pretreatment system for caprolactam production wastewater via the ammonoxime process provided by this utility model adopts an integrated combined structure, reducing the system's footprint and making wastewater treatment more economical, efficient, and stable. The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit it. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. An integrated pretreatment system for caprolactam production wastewater via the ammonoxime process, characterized in that, The system includes a tank body, in which a nicotinic acid reaction chamber (1), a Fenton reaction chamber (2), a coagulation reaction chamber (3), and a pre-sedimentation reaction chamber (4) are arranged sequentially along the wastewater input direction. The pre-sedimentation reaction chamber (4) is provided with an inlet zone (7), a clear water zone (8), and a sedimentation inclined tube (6). The inlet zone (7) is connected to the coagulation reaction chamber (3) and is located below the sedimentation inclined tube (6). The bottom of the inlet zone (7) is provided with a sludge hopper (29). The clear water zone (8) is located above the sedimentation inclined tube (6). The top of the clear water zone (8) is provided with a clear water channel (9).

2. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The nicotinic acid reaction chamber (1) is connected to a water inlet pipe (11) and a nicotinic acid addition pipe (20), which are respectively connected to the water inlet of the nicotinic acid reaction chamber (1); the Fenton reaction chamber (2) is connected to a ferrous sulfate addition pipe (21) and a hydrogen peroxide addition pipe (22), which are respectively connected to the water inlet of the Fenton reaction chamber (2); the coagulation reaction chamber (3) is connected to an alkali addition pipe (23), a coagulant addition pipe (24), and a flocculant addition pipe (25), which are respectively connected to the water inlet of the coagulation reaction chamber (3).

3. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The nicotinic acid reaction chamber (1) and the Fenton reaction chamber (2) are separated by a first partition wall (30), and the first partition wall (30) is provided with a first connecting hole (12), and the nicotinic acid reaction chamber (1) and the Fenton reaction chamber (2) are connected by the first connecting hole (12).

4. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The Fenton reaction chamber (2) and the coagulation reaction chamber (3) are separated by a second partition wall (31), and the second partition wall (31) is provided with a second connecting hole (13). The Fenton reaction chamber (2) and the coagulation reaction chamber (3) are connected by the second connecting hole (13).

5. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The nicotinic acid reaction chamber (1) is equipped with a first stirrer (51); the nicotinic acid reaction chamber (1) is equipped with a first pH probe (26); the Fenton reaction chamber (2) is equipped with a second stirrer (52); the Fenton reaction chamber (2) is equipped with a second pH probe (27); the coagulation reaction chamber (3) is equipped with a third stirrer (53); the coagulation reaction chamber (3) is equipped with a third pH probe (28).

6. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The coagulation reaction chamber (3) and the pre-sedimentation reaction chamber (4) are connected by a connecting area (14). The connecting area (14) is provided with a third partition wall (141), a first connecting section (142), a fourth partition wall (143), a second connecting section (144), and a fifth partition wall (145) in sequence along the water inlet direction. The third partition wall (141) is provided with a first connecting port (146). The coagulation reaction chamber (3) is connected to the first connecting section (142) through the first connecting port (146). The fourth partition wall (143) is provided with a second connecting port (147). The first connecting section (142) is connected to the second connecting section (144) through the second connecting port (147). The second connecting section (144) is also connected to the pre-sedimentation reaction chamber (4).

7. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 6, characterized in that, The coagulation reaction chamber (3) is connected to the inlet end of the first connecting section (142) via the first connecting port (146), the outlet end of the first connecting section (142) is connected to the inlet end of the second connecting section (144) via the second connecting port (147), and the outlet end of the second connecting section (144) is connected to the inlet area (7) of the pre-sedimentation reaction chamber (4).

8. The integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The sludge hopper (29) is located at the center of the bottom of the water inlet area (7), and the diameter of the sludge hopper (29) gradually decreases from top to bottom; a sludge pump (17) is provided outside the pool body, and the sludge pump (17) is connected to the sludge hopper (29).

9. An integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 8, characterized in that, The bottom of the water inlet area (7) is equipped with a sludge scraper (10); the side wall of the sludge hopper (29) is provided with a sludge discharge port (16), which is connected to the sludge pump (17) via a sludge inlet pipe (18); the sludge pump (17) is also connected to a sludge pipe (19).

10. An integrated pretreatment system for caprolactam production wastewater via ammonoxime process according to claim 1, characterized in that, The clear water zone (8) is connected to a water outlet pipe (15), which is connected to the water outlet end of the clear water zone (8).

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