A method and system for treating acrylonitrile ammonium sulfate wastewater

Abstract

The application provides a treatment method and system for acrylonitrile ammonium sulfate wastewater, and the treatment method comprises the following steps: step 1, evaporative crystallization is performed on the acrylonitrile ammonium sulfate wastewater to obtain evaporative condensate, crystallized solid and evaporative concentrated solution; step 2, the evaporative concentrated solution is mixed with a reverse demulsifier; step 3, the mixed solution obtained in step 2 is subjected to first oil-water separation under the action of gravity to obtain an oil phase and a water phase; and step 4, the water phase is subjected to second oil-water separation, and the second oil-water separation is performed by evaporation, and the remaining mixed solution after evaporation is mixed with the acrylonitrile ammonium sulfate wastewater and then recycled for the evaporative crystallization. The evaporative second oil-water separator and the first oil-water separator are connected in series to perform deep oil-water separation, and the residual micro-particle-size emulsified oil and dissolved oil in the water phase are deeply removed, so that the color problem of the ammonium sulfate product is fundamentally solved.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a method and system for treating acrylonitrile ammonium sulfate wastewater. Background Technology

[0002] Currently, domestic refineries all use the propylene ammoxidation process to produce acrylonitrile. During the production process, unreacted ammonia gas discharged from the reactor enters a quench tower for neutralization with sulfuric acid, thus generating a large amount of dilute ammonium sulfate solution. Production enterprises often use evaporation crystallization to treat the dilute ammonium sulfate solution, producing crystalline solids, evaporation condensate, and evaporation concentrate during the evaporation crystallization process. The crystalline solid ammonium sulfate can be used as fertilizer; the evaporation condensate has relatively low organic matter and ammonia nitrogen content, and can be reused or discharged after treatment; the evaporation concentrate is of the O / W type, in which high concentrations of polyacrylonitrile, aromatic compounds, carbonyl compounds, and other complex components are dissolved in the aqueous phase in the form of emulsified oil and dissolved oil. The droplet size of emulsified oil and dissolved oil is generally less than 2μm, with the dissolved oil droplet size reaching less than 0.1μm, or even nanometer scale, making it difficult to achieve oil-water separation using conventional wastewater treatment methods.

[0003] Currently, most refineries use gravity settling (vertical oil removal tank) to treat evaporation concentrate (oil-water separation), with the oil phase treated by incineration and the water phase recycled back to the evaporator. However, due to the poor separation effect of gravity settling, the ammonium sulfate content in the oil phase is high. Taking a certain refinery as an example, the ammonium sulfate concentration in the concentrate at the outlet of its evaporator crystallizer is as high as about 20%, causing problems such as increased pressure differential of the bag filter in the wastewater incineration unit, crystallization blockage, and frequent tripping of the incinerator. At the same time, there are also problems such as high oil content in the circulating water phase and discoloration of the crystallized ammonium sulfate product.

[0004] The acrylonitrile-supporting ammonium sulfate unit of Daqing Petrochemical uses a polymer separator to separate the oil and water of the ammonium sulfate concentrate fed into the evaporator crystallizer. The separator is a specially designed and modified gravity settling tank with inclined baffles and separation baffles inside. The inclined baffles increase the separation power, and the separation baffles serve as the separation zones (feed zone and settling zone). During separation, the heavy component ammonium sulfate solution enters the settling chamber and is pumped to the evaporator crystallizer through the bottom outlet of the settling chamber to recover the ammonium sulfate crystals. The light component polymer overflows from the overflow port at the highest point of the separator, is diluted by water injection through the upper spray pipe of the polymer separator, and then enters the polymer mixer. A certain amount of dilution water is added in the mixer, and finally it is sent to the acrylonitrile unit incinerator for incineration (Yang Daming. Research on new equipment to solve polymer blockage in ammonium sulfate unit [J]. Refining and Chemical Industry, 2007(04):30-32+58.). This method features a special design in the internal structure of the oil-water separator, achieving a certain oil-water separation effect. However, it still suffers from severe phase entrainment, making it difficult to fundamentally solve the problem of incomplete oil-water separation.

[0005] In addition to gravity sedimentation technology, various enterprises and research institutions have also developed technologies such as extraction crystallization, extraction oil removal, wet catalytic oxidation, membrane separation, and bioelectrochemical technology for treating acrylonitrile ammonium sulfate wastewater.

[0006] CN110330035A discloses a method for recovering ammonium sulfate from the evaporation concentrate of acrylonitrile ammonium sulfate solution using a multi-stage extraction crystallization technique. The extractant is one or a mixture of monohydric alcohols and dihydric alcohols with ≤4 carbon atoms. Mixing the extractant with the concentrate reduces the polarity of the solution, thereby reducing the solubility of ammonium sulfate in the solution and promoting its crystallization. Simultaneously, it significantly enhances the solution system's ability to dissolve polymers and reduces the adsorption of polymers by the crystals during the ammonium sulfate crystallization process. After the ammonium sulfate crystals are separated, the extractant washes the surface of the crystals to remove any adsorbed polymers, achieving efficient separation of ammonium sulfate from the polymers. This method addresses the issues of incineration unit blockage and discoloration of the ammonium sulfate product from the perspective of extraction crystallization. However, the subsequent separation of the extractant requires an additional distillation section, significantly increasing equipment investment and energy consumption.

[0007] CN111423433A discloses a method for preparing an extractant and its application in treating ammonium sulfate wastewater. The extractant includes aliphatic amines and aromatic amines, and the aliphatic amines have the following structure: The structure of aromatic amines is This mixed extractant has good selective solubility for heavy component polymers in ammonium sulfate solution, which can extract the heavy component polymers from ammonium sulfate solution into the organic phase, achieving efficient separation of ammonium sulfate solution and heavy component sludge oil, and significantly improving the quality of ammonium sulfate product. However, this method also has the problem of extractant distillation separation, which greatly increases the process cost and has poor economic efficiency.

[0008] CN104108779A discloses a wet catalytic oxidation technology for treating ammonium sulfate wastewater. Using ammonium sulfate wastewater generated during acrylonitrile production as raw material, it employs a multiphase catalyst and a fixed-bed reactor. The wastewater, carrier gas, and catalyst are fully contacted and reacted in the reactor at a reaction temperature of 200-300℃, a reaction pressure of 5-10 MPa, and a residence time of 10-120 min. The catalyst uses zirconium oxide or alumina ceramic foam board supported on a precious metal catalyst. After treatment, the COD of the wastewater is reduced by 90.8%. Wet catalytic oxidant technology has advantages such as high treatment efficiency and low secondary pollution, but it requires high temperature and pressure conditions, resulting in high energy consumption. It also produces organic acid intermediates that corrode equipment. Furthermore, it suffers from high catalyst preparation and regeneration costs and heavy metal ion pollution from the catalyst.

[0009] CN105366754A discloses a technology for treating ammonium sulfate wastewater using a multi-stage membrane contactor. The membrane material is hydrophobic polypropylene, polyvinylidene fluoride, or polytetrafluoroethylene, and the form is a hollow fiber membrane or a flat sheet membrane. After treatment, the ammonia nitrogen removal rate of the wastewater reaches 98.7%, and a high-concentration ammonium sulfate solution is obtained. The solution is further evaporated, concentrated, and crystallized to obtain industrial-grade ammonium sulfate product.

[0010] Membrane filtration technology is mainly used to remove free ammonia and floating oil. However, when treating acrylonitrile ammonium sulfate wastewater rich in high-viscosity polymer sludge, it will quickly clog the membrane pores and force the equipment to shut down. Therefore, this technology is limited to treating low-viscosity dilute solutions.

[0011] CN105645586A discloses a continuous flow three-stage biological electrostatic desalination technology for treating ammonium sulfate refining wastewater. The biostatic desalination device consists of an anode chamber, a cathode chamber, a cation exchange membrane, an anion exchange membrane, an aeration device, and a facultative chamber. After a cultivation stage, an acclimatization stage, and continuous operation, the aeration device is activated. The ammonium sulfate wastewater is treated sequentially through the anode chamber, facultative chamber, cathode chamber, and desalination chamber. The treatment process achieves a stable current output, with an ammonium sulfate removal rate of over 80%, realizing the three functions of pollutant degradation, electricity generation, and desalination. This method utilizes microorganisms to degrade organic matter, converting chemical energy into electrical energy, realizing the resource reuse of organic waste, and providing a new approach and development direction for chemical wastewater treatment. However, the cultivation of biological microbial communities is difficult and costly, and it is difficult to achieve efficient degradation of complex polymers in acrylonitrile ammonium sulfate wastewater.

[0012] CN104986889A discloses a combined process for treating fracturing drilling wastewater, specifically separation-filtration-aeration-coagulation sedimentation-adsorption filtration. In the first separation step, gravity sedimentation is used to separate the oil and water phases, and it is mentioned that the oil-water separation effect can be enhanced by adding a reverse demulsifier. This separation process only serves as pretreatment; an oil content of ≤580 mg / L in the water is sufficient to meet the standard, with subsequent processes mainly responsible for wastewater purification. This technology uses numerous reagents and has a complex process flow, making it unsuitable for treating acrylonitrile ammonium sulfate wastewater.

[0013] Therefore, further research is needed in this field on the treatment of acrylonitrile ammonium sulfate wastewater. Summary of the Invention

[0014] The main objective of this invention is to provide a method and system for treating acrylonitrile ammonium sulfate wastewater, so as to solve the problem of difficult oil-water separation in acrylonitrile ammonium sulfate wastewater.

[0015] To achieve the above objectives, the present invention provides a method for treating acrylonitrile ammonium sulfate wastewater, comprising the following steps:

[0016] Step 1: Evaporate and crystallize the acrylonitrile ammonium sulfate wastewater to obtain evaporation condensate, crystalline solid and evaporation concentrate;

[0017] Step 2: The evaporated concentrate is mixed with a reverse demulsifier;

[0018] Step 3: The mixture obtained in Step 2 is subjected to the first oil-water separation under gravity sedimentation to obtain an oil phase and an aqueous phase;

[0019] Step 4: The aqueous phase undergoes a second oil-water separation, which is carried out by evaporation. After evaporation, the remaining mixture is mixed with the acrylonitrile ammonium sulfate wastewater and then recycled for further evaporation and crystallization.

[0020] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the ratio of the flow rate of the evaporation condensate to the flow rate of the acrylonitrile ammonium sulfate wastewater is 1:(1-5); and the ratio of the flow rate of the evaporation concentrate to the flow rate of the acrylonitrile ammonium sulfate wastewater is 1:(1-3).

[0021] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the first oil-water separation is carried out in a horizontal separation tank, and the ratio of the height to the length of the horizontal separation tank is 1:(2-10).

[0022] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the ratio of the flow rate of the acrylonitrile ammonium sulfate wastewater to the flow rate of the oil phase is (1-5):1; and the ratio of the flow rate of the aqueous phase to the flow rate of the oil phase is (1-5):1.

[0023] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention includes evaporation to obtain an oil-containing aqueous phase and a residual mixture, wherein the oil-containing aqueous phase is mixed with the evaporation concentrate and a reverse demulsifier, and the ratio of the flow rate of the oil-containing aqueous phase to the flow rate of the aqueous phase is 1:(3-10).

[0024] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the preparation method of the reverse demulsifier includes:

[0025] Step a involves reacting azodicarbonyl with propylene oxide via a ring-opening polymerization reaction to obtain azopolyether oil head;

[0026] Step b involves copolymerizing the azo polyether oil head, ethylene oxide, and propylene oxide to obtain a block azo polyether.

[0027] Step c involves subjecting the block azo polyether to a crosslinking reaction under the action of a crosslinking agent to obtain a crosslinked polyether.

[0028] Step d involves reacting the crosslinked polyether and the quaternary ammonium salt under heating to obtain an oil-soluble reverse demulsifier.

[0029] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention includes azodiazepine, which is one of azobisisobutyronitrile, azobisisovalerate, and azobisisoheptanenitrile; the reaction of the azodiazepine with propylene oxide is carried out in the presence of a ring-opening polymerization catalyst and an oil-soluble solvent, wherein the ring-opening polymerization catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide; and the oil-soluble solvent is one of acetone, methyl ethyl ketone, methyl isobutyl ketone, and tetrahydrofuranone.

[0030] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the mass ratio of azodiazepine to propylene oxide is 2:1-8:1, the amount of the ring-opening polymerization catalyst is 0.05-0.3% of the total mass of azodiazepine and propylene oxide, and the reaction temperature of azodiazepine and propylene oxide is 100-120℃, and the reaction time is 1-3h.

[0031] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the reaction of the azo polyether oil head, ethylene oxide and propylene oxide is carried out under the action of a ring-opening polymerization catalyst, wherein the ring-opening polymerization catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide, and the amount of the ring-opening polymerization catalyst is 0.05-0.3% of the total mass of the azo polyether oil head, ethylene oxide and propylene oxide.

[0032] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the reaction temperature of the azo polyether oil head, ethylene oxide and propylene oxide is 110-120℃, the mass ratio of the azo polyether oil head to ethylene oxide is 1:2-1:5, and the mass ratio of the azo polyether oil head to propylene oxide is 1:8-1:12.

[0033] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the crosslinking agent is epichlorohydrin, and the mass ratio of the block azo polyether to the crosslinking agent is 500:1-600:1.

[0034] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the crosslinking reaction is carried out at a temperature of 60-80℃ for a time of 1-3 hours.

[0035] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention, wherein the quaternary ammonium salt is one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride, and the amount of the quaternary ammonium salt used is 20-30% of the mass of the crosslinked polyether.

[0036] The method for treating acrylonitrile ammonium sulfate wastewater according to the present invention includes a heating temperature of 80-95℃ and a reaction time of 3-5h in step d; the reaction mixture of the crosslinked polyether and the quaternary ammonium salt is subjected to oil-water separation, and the resulting oil phase is distilled to obtain an oil-soluble reverse demulsifier.

[0037] To achieve the above objectives, the present invention also provides a treatment system for acrylonitrile ammonium sulfate wastewater, comprising:

[0038] An evaporator crystallizer is used for the evaporation and crystallization of acrylonitrile ammonium sulfate wastewater to obtain evaporated condensate, crystalline solids, and evaporated concentrate.

[0039] A static mixer, connected to the evaporator crystallizer, is used to mix the evaporation concentrate with the reverse demulsifier;

[0040] The first oil-water separator is connected to the static mixer and is used to perform the first oil-water separation of the mixture in the static mixer under the action of gravity sedimentation to obtain an oil phase and a water phase.

[0041] The second oil-water separator is an evaporator, which is connected to the first oil-water separator and the evaporator crystallizer respectively. It is used to evaporate the aqueous phase, and the remaining mixture after evaporation is recycled back to the evaporator crystallizer for further evaporation and crystallization.

[0042] The acrylonitrile ammonium sulfate wastewater treatment system of the present invention, wherein the reverse demulsifier is prepared by the following steps:

[0043] Step a involves reacting azodicarbonyl with propylene oxide via a ring-opening polymerization reaction to obtain azopolyether oil head;

[0044] Step b involves copolymerizing the azo polyether oil head, ethylene oxide, and propylene oxide to obtain a block azo polyether.

[0045] Step c involves subjecting the block azo polyether to a crosslinking reaction under the action of a crosslinking agent to obtain a crosslinked polyether.

[0046] Step d involves reacting the crosslinked polyether and the quaternary ammonium salt under heating to obtain an oil-soluble reverse demulsifier.

[0047] The beneficial effects of this invention are:

[0048] This invention employs an evaporative second oil-water separator connected in series with a first oil-water separator for deep oil-water separation, effectively removing residual micro-particles of emulsified oil and dissolved oil from the aqueous phase, thus fundamentally solving the problem of discoloration in ammonium sulfate products.

[0049] The oil-soluble reverse demulsifier provided by this invention combines the advantages of good oil-water separation effect of nonionic polyether with fast oil removal rate of polyquaternary ammonium salt. It can quickly break the double electric layer balance at the oil-water interface, promote the coalescence of oil droplets, achieve efficient and deep demulsification, and significantly improve the oil-water separation effect.

[0050] The reverse demulsifier provided by this invention has good oil solubility, and its solubility in the upper oil phase of acrylonitrile ammonium sulfate wastewater is even better. When used to treat ammonium sulfate wastewater, it dissolves in the oil phase and enters the incinerator with the oil phase, without causing pollution to the aqueous phase. It ensures the quality of ammonium sulfate products while achieving efficient demulsification and oil removal. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of an acrylonitrile ammonium sulfate wastewater treatment system according to one embodiment of the present invention.

[0052] Figure 2 This is a schematic diagram of an acrylonitrile ammonium sulfate wastewater treatment system for comparison.

[0053] In the attached figures, the following labels are used:

[0054] 1. Evaporator Crystallizer

[0055] 2 Static Mixer

[0056] 3,3a First oil-water separator

[0057] 4 Second oil-water separator

[0058] 5 thickener

[0059] 6. Solid-liquid centrifuge

[0060] 7. Oil-water mixer Detailed Implementation

[0061] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0062] Refineries typically use the propylene ammoxidation process to produce acrylonitrile. During this process, unreacted ammonia gas discharged from the reactor enters a quench tower where it is neutralized with sulfuric acid, thus generating a large amount of dilute ammonium sulfate solution. The acrylonitrile ammonium sulfate wastewater of this invention is this dilute ammonium sulfate solution. This invention provides a method for treating this acrylonitrile ammonium sulfate wastewater, comprising the following steps:

[0063] Step 1: Evaporate and crystallize the acrylonitrile ammonium sulfate wastewater to obtain evaporation condensate, crystalline solid and evaporation concentrate;

[0064] Step 2: The evaporated concentrate is mixed with a reverse demulsifier;

[0065] Step 3: The mixture obtained in Step 2 is subjected to the first oil-water separation under gravity sedimentation to obtain an oil phase and an aqueous phase;

[0066] Step 4: The aqueous phase undergoes a second oil-water separation, which is carried out by evaporation. After evaporation, the remaining mixture is mixed with the acrylonitrile ammonium sulfate wastewater and then recycled for further evaporation and crystallization.

[0067] The present invention also provides a treatment system for acrylonitrile ammonium sulfate wastewater, which can be used in the above-mentioned treatment method for acrylonitrile ammonium sulfate wastewater, comprising:

[0068] An evaporator crystallizer is used for the evaporation and crystallization of acrylonitrile ammonium sulfate wastewater to obtain evaporated condensate, crystalline solids, and evaporated concentrate.

[0069] A static mixer, connected to the evaporator crystallizer, is used to mix the evaporation concentrate with the reverse demulsifier;

[0070] The first oil-water separator is connected to the static mixer and is used to perform the first oil-water separation of the mixture in the static mixer under the action of gravity sedimentation to obtain an oil phase and a water phase.

[0071] The second oil-water separator is an evaporator, which is connected to the first oil-water separator and the evaporator crystallizer respectively. It is used to evaporate the aqueous phase, and the remaining mixture after evaporation is recycled back to the evaporator crystallizer for further evaporation and crystallization.

[0072] This invention introduces a reverse demulsifier into the evaporation concentrate and combines it with secondary oil-water separation technology to achieve deep separation of the oil and water phases in the ammonium sulfate evaporation concentrate, extend the operating cycle of the equipment, reduce ammonium sulfate loss, and improve the quality of ammonium sulfate products.

[0073] Please see Figure 1 In this invention, acrylonitrile ammonium sulfate wastewater is first evaporated and crystallized to obtain evaporated condensate, crystalline solid and evaporated concentrate.

[0074] In one embodiment, the acrylonitrile ammonium sulfate wastewater is fed to an evaporator crystallizer 1 for evaporation and crystallization. As described above, the acrylonitrile ammonium sulfate wastewater is generated by neutralizing unreacted ammonia in the acrylonitrile-to-acrylonitrile process using sulfuric acid in a quench tower, and the ammonium sulfate mass concentration is, for example, 15-25%. The present invention does not particularly limit the conditions for evaporation and crystallization. In one embodiment, the ratio of the flow rate of the evaporation condensate to the flow rate of the acrylonitrile ammonium sulfate wastewater is 1:(1-5), preferably 1:(1.3-2); the ratio of the flow rate of the evaporation concentrate to the flow rate of the acrylonitrile ammonium sulfate wastewater is 1:(1-3), preferably 1:(1.5-2.5).

[0075] In one embodiment, the thickener 5 is connected to the evaporator crystallizer 1. The evaporated condensate is directly discharged or recycled. The crystalline solid ammonium sulfate, carrying a certain amount of solution, is pumped into the thickener 5, where the crystals settle. The thickener 5 can also be connected to a solid-liquid centrifuge 6. The material discharged from the bottom of the thickener 5 enters the solid-liquid centrifuge 6, where it is centrifuged to remove water and obtain the ammonium sulfate product. The overflow circulating liquid from the top of the thickener 5 returns to the evaporator crystallizer 1 for further crystallization. In another embodiment, the flow ratio of the ammonium sulfate solution flowing into the thickener 5 to the acrylonitrile ammonium sulfate wastewater is 1:(0.1-1), preferably 1:(0.3-0.5).

[0076] In this invention, the static mixer 2 is connected to the evaporator crystallizer 1. The evaporation concentrate is fed to the static mixer 2, and the reverse demulsifier solution is also fed to the static mixer 2 to mix with the evaporation concentrate. In one embodiment, the amount of reverse demulsifier added per unit time is 1-50 ppm of the evaporation concentrate flow rate, preferably 5-20 ppm. In another embodiment, the solvent in the reverse demulsifier solution is one of methyl ethyl ketone and methyl isobutyl ketone, and the mass ratio of reverse demulsifier to solvent is 1:(10-100), preferably 1:(30-90). In yet another embodiment, the residence time of the evaporation concentrate in the static distributor 2 is 0.2-1 h, preferably 0.2-0.5 h.

[0077] In this invention, the first oil-water separator 3 is connected to the static mixer 2. The evaporated concentrate and the reverse demulsifier are mixed and then fed to the first oil-water separator 3. The evaporated concentrate undergoes oil-water separation due to gravity sedimentation, yielding an oil phase and a water phase. In one embodiment, the first oil-water separator 3 is also connected to an oil-water mixer 7. The oil phase is fed to the oil-water mixer 7 through the oil phase outlet at the top of the first oil-water separator 3. A certain amount of acrylonitrile ammonium sulfate wastewater is fed to the oil-water mixer 7 to mix and dilute with the oil phase. The mixture is then fed to the incineration unit for incineration. The flow ratio of the acrylonitrile ammonium sulfate wastewater to the oil phase fed to the oil-water mixer 7 is 1:(3-10), preferably 1:(3-5). In another embodiment, the residence time of the mixture in the oil-water mixer 7 is 0.1-2 hours, or 0.2-1 hour.

[0078] In one embodiment, the first oil-water separator 3 of the present invention is a horizontal separator, which has a better oil-water separation effect compared with the traditional vertical separator, and does not require the installation of baffles or other structures. Its structure is simple, its manufacturing cost is low, and it is easy to maintain and repair later.

[0079] In detail, the horizontal separator extends the wastewater flow distance, allowing oil and water droplets to float and sink fully under gravity, further improving the oil-water separation effect. Furthermore, with the continuous directional flow of wastewater, the impact of material vibration at the inlet is reduced, the oil-water interface tends to be stable, and the phenomenon of mutual entrainment is avoided.

[0080] In another embodiment, the height to length ratio of the first oil-water separator 3 of the present invention is 1:(2-10), preferably 1:(3-8), and the residence time of the mixture of the evaporation concentrate and the reverse demulsifier in the first oil-water separator 3 is 1-6h, preferably 1-3h.

[0081] In another embodiment, the flow ratio of acrylonitrile ammonium sulfate wastewater to oil phase is (1-5):1, preferably (1-3):1, and the flow ratio of water phase to oil phase is (1-5):1, preferably (1-3):1.

[0082] The second oil-water separator 4 of this invention is connected to the first oil-water separator 3 and the evaporator crystallizer 2, respectively. The second oil-water separator 4 is an evaporator. The aqueous phase is transported to the second oil-water separator 4 for evaporation treatment, resulting in an oil-containing aqueous phase and a residual mixture after evaporation. In one embodiment, water is also added to the second oil-water separator 4, firstly to dilute the ammonium sulfate concentrate discharged from the bottom of the second oil-water separator 4 to prevent blockage of the transfer pump, and secondly to maintain a constant liquid level in the evaporator crystallizer 1. The flow ratio of evaporation rate to influent water rate is 1:(3-10), preferably 1:(3-5), that is, the flow ratio of the oil-containing aqueous phase to the total amount of aqueous phase and added water is 1:(3-10). In another embodiment, the amount of added water is the same as the evaporation rate.

[0083] In this invention, the second oil-water separator 4 is connected to the evaporator-crystallizer 2. After evaporation, the remaining mixture is circulated back to the evaporator-crystallizer 2, where it is mixed with acrylonitrile ammonium sulfate wastewater and then evaporated and crystallized again. In one embodiment, the oil-water phase is returned to the static mixer 2.

[0084] This invention, based on the introduction of chemical demulsification technology, designs and develops a secondary deep separation process formed by connecting a horizontal oil-water separator and an evaporator in series, fundamentally solving the problem of mutual entrainment between the oil and water phases in the acrylonitrile ammonium sulfate evaporation concentrate.

[0085] In detail, this invention removes a certain amount of water through evaporation in a second oil-water separator (evaporator), causing residual emulsified oil and dissolved oil to precipitate and float on the water surface. The upper thin oil layer carries some aqueous solution back to the static mixer for secondary demulsification, while the lower layer returns to the evaporator crystallizer. The oil content (concentration and total amount) in the water-containing ammonium sulfate is reduced, thus reducing the oil content in the evaporator crystallizer. This treatment technology solves the problem of discoloration in ammonium sulfate products by reducing the content (concentration and total amount) of emulsified oil and dissolved oil.

[0086] The reverse demulsifier of this invention can be any demulsifier disclosed in the prior art. However, to improve the oil-water separation effect, this invention provides an azo crosslinked polyether-quaternary ammonium salt demulsifier. Through the electrostatic attraction of the highly electrostatically charged azo nanotube to the cationic quaternary ammonium salt, the nonionic polyether and the cationic polyquaternary ammonium salt are miscible to form a uniform and stable demulsifier system. This demulsifier system combines the advantages of good oil-water separation of polyether with the rapid oil removal rate of polyquaternary ammonium salt. It can quickly break the double-layer equilibrium at the oil-water interface, promote oil droplet aggregation, achieve efficient and deep demulsification, and significantly improve the oil-water separation effect. The azo structure in the reverse demulsifier of this invention endows it with good oil solubility. After oil-water separation, it enters the incineration unit with the oil phase, ensuring the quality of ammonium sulfate products while achieving efficient oil-water separation.

[0087] This invention provides a method for preparing an oil-soluble reverse demulsifier. An azo initiator is used to initiate the copolymerization of epoxides to generate polyethers. Then, under the action of the crosslinking agent epichlorohydrin, a high molecular weight crosslinked polyether is obtained. This high molecular weight crosslinked polyether has good oleophilic and hydrophobic properties and high solubility in common organic solvents. The high molecular weight crosslinked polyether is dissolved in an oil-soluble solvent, and a cationic quaternary ammonium salt is added to the solution. The strong electrostatic attraction of the azo initiator to the cationic quaternary ammonium salt results in an azo crosslinked polyether-quaternary ammonium salt reverse demulsifier. This demulsifier forms a stable and homogeneous composite reverse demulsifier system in the solvent, combining the advantages of both polyether-type and cationic reverse demulsifiers. It can rapidly sweep away oil droplets, accelerate oil-water separation, and achieve efficient demulsification. Furthermore, this reverse demulsifier has extremely low water solubility and will not return to the evaporator crystallizer with the aqueous phase, thus not affecting the quality of the ammonium sulfate product.

[0088] Specifically, the preparation method of the oil-soluble reverse demulsifier of the present invention includes the following steps:

[0089] Step 1: Azobisonitrile undergoes a ring-opening polymerization reaction with propylene oxide to obtain azopolyether oil head;

[0090] Step 2: Copolymerize the azo polyether oil head, ethylene oxide and propylene oxide to obtain block azo polyether;

[0091] Step 3: The block azo polyether undergoes a crosslinking reaction under the action of a crosslinking agent to obtain a crosslinked polyether;

[0092] Step 4: The cross-linked polyether and the quaternary ammonium salt are reacted under heating to obtain an oil-soluble reverse demulsifier.

[0093] In step 1, azodiacetonitrile is used as the initiator and propylene oxide is used as the monomer. In one embodiment, the azodiacetonitrile is one of azobisisobutyronitrile, azobisisovalerate, and azobisisoheptanenitrile, preferably azobisisoheptanenitrile. The reaction between azodiacetonitrile and propylene oxide is carried out in the presence of a ring-opening polymerization catalyst and an oil-soluble solvent. The ring-opening polymerization catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide, preferably sodium hydroxide and potassium hydroxide. The oil-soluble solvent is, for example, an oil-soluble ketone, more preferably one of acetone, methyl ethyl ketone, methyl isobutyl ketone, and tetrahydrofuranone, preferably one of methyl ethyl ketone and methyl isobutyl ketone.

[0094] In another embodiment, the mass ratio of azodiacetonitrile to propylene oxide is 2:1-8:1, preferably 3:1-5:1, and the amount of ring-opening polymerization catalyst is 0.05-0.3% of the total mass of azodiacetonitrile and propylene oxide, preferably 0.1-0.2%; the reaction temperature of azodiacetonitrile and propylene oxide is 100-120°C, and the reaction time is 1-3 hours.

[0095] In another embodiment, step 1, the ring-opening polymerization reaction, is carried out in a reactor. Azodiazepine and an oil-soluble solvent are added to the reactor and stirred at 40-60°C for 10 minutes to mix thoroughly. The amount of initiator is 20-60% of the solvent mass, preferably 30-50%. Then, a ring-opening polymerization catalyst is added, and vacuum dehydration is performed at 90-100°C for, for example, 20-40 minutes. Next, propylene oxide is added, and the polymerization reaction is carried out at 100-120°C, with the pressure controlled at 0-0.4 MPa. The reaction time is 0.5-3 hours, preferably 1-3 hours. After the reaction, the filter residue is removed to obtain an azo polyether oil-based solution.

[0096] The reactor is a stainless steel reactor with a working pressure of 2-5 MPa.

[0097] The azo polyether oil nozzle obtained by this invention has, for example, the structure of Formula 1:

[0098]

[0099] R is selected from methylene, ethylene, and isobutylene.

[0100] Step 2 involves the preparation of block polyethers, specifically using azo polyether oil, ethylene oxide, and propylene oxide as raw materials, and copolymerizing the three components to form a block polyether structure. The copolymerization reaction is carried out in a reactor. First, the azo polyether oil and ring-opening polymerization catalyst are added to the reactor, and vacuum dehydration is performed at 90-100℃ for 30 minutes. Then, the temperature is raised to 110-120℃ and the first copolymer component, ethylene oxide, is introduced, with the pressure controlled at 0-0.4 MPa. The reaction is carried out for 0.5-3 hours. Then, the second copolymer component, propylene oxide, is introduced, with the pressure controlled at 0-0.4 MPa, and the temperature is maintained for another 0.5-3 hours. The resulting block azo polyether is obtained after filtration.

[0101] In one embodiment, the ring-opening polymerization catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide, preferably one of sodium hydroxide and potassium hydroxide. The amount of the ring-opening polymerization catalyst is 0.05-0.3% of the total mass of azo polyether oil, ethylene oxide, and propylene oxide, preferably 0.1-0.2%.

[0102] In another embodiment, the reaction temperature of the azo polyether oil head, ethylene oxide and propylene oxide is 110-120°C, the mass ratio of the azo polyether oil head to ethylene oxide is 1:2-1:5, preferably 1:2-1:3, and the mass ratio of the azo polyether oil head to propylene oxide is 1:8-1:12.

[0103] Step 3 is the preparation of cross-linked polyether. Specifically, block azo polyether is used as monomer and epichlorohydrin is used as cross-linking agent. The reaction is carried out at 60-80℃ for 1-3 hours. Then, the oil-soluble solvent used in the synthesis of azo polyether oil head is added for dilution to obtain cross-linked polyether solution.

[0104] In one embodiment, the block azo polyether is first heated to 60-80°C, and then a crosslinking agent is added to carry out the reaction.

[0105] In another embodiment, the mass ratio of block azo polyether to the crosslinking agent is 500:1-600:1. In the resulting crosslinked polyether solution, the solvent mass is 200-400% of the total mass of the block azo polyether and epichlorohydrin.

[0106] Step 4 is the preparation of the oil-soluble reverse demulsifier. Specifically, a quaternary ammonium salt aqueous solution is added dropwise to the cross-linked polyether solution over a period of 0.5-3 hours, with stirring maintained during the addition. After the addition is complete, the reaction system is heated to 80-95°C and stirred for 3-5 hours. The mixture is then removed, allowed to stand for 3-5 hours, and the upper oil phase is separated. The solvent is removed by vacuum distillation to obtain the azo cross-linked polyether-quaternary ammonium salt reverse demulsifier.

[0107] The quaternary ammonium salt is a long-chain quaternary ammonium salt, for example, having 10-20 carbon atoms, and is selected from dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride, preferably dodecyltrimethylammonium chloride or tetradecyltrimethylammonium bromide. The amount of quaternary ammonium salt used is 20-30% of the mass of the crosslinked polyether. In the aqueous solution of the quaternary ammonium salt, the concentration of the quaternary ammonium salt is 20-40 wt%.

[0108] The reverse demulsifier obtained by the above method of the present invention is, for example, azobisisoheptanenitrile-dodecyltrimethylammonium chloride or azobisisoheptanenitrile-tetradecyltrimethylammonium bromide.

[0109] The reverse demulsifier of the present invention comprises azo polyether and cationic quaternary ammonium salt. The high nitrogen content in the azo polyether gives it a strong electrostatic attraction, which forms a strong electrostatic attraction to the highly cationic quaternary ammonium salt, enabling the nonionic polyether and the cationic polyquaternary ammonium salt to form a stable composite system in the solution, thus fully demonstrating the advantages of nonionic polyether and cationic reverse demulsifier.

[0110] Furthermore, the oil-soluble azobisonitrile structure, long-chain block polyether structure, and long-chain quaternary ammonium salt structure in the reverse demulsifier provided by this invention increase the nonpolarity of the system, giving the reverse demulsifier good oleophilic and hydrophobic properties. Especially for acrylonitrile ammonium sulfate wastewater, the oil phase of this wastewater is mainly polyacrylonitrile, while the azobisonitrile in the reverse demulsifier structure of this invention contains a certain amount of nitrile groups. According to the principle of like dissolves like, the demulsifier has excellent solubility in the oil phase of acrylonitrile wastewater.

[0111] The technical solution of the present invention will be further described in detail below through specific embodiments. Examples 1-4 are for the preparation of reverse-phase demulsifiers, Examples 5-8 are for the demulsification performance evaluation of commercially available reverse-phase demulsifier SP169, and Examples 9-20 are for the demulsification performance evaluation of the reverse-phase demulsifier of the present invention. Unless otherwise specified, "%" refers to mass percentage. The oil content of the aqueous phase of the examples and comparative examples was determined according to "HJ637-2018 Determination of Water Quality, Petroleum Products and Animal Oils by Infrared Spectrophotometry", the concentration of ammonium sulfate was determined by liquid chromatography, and the color of the ammonium sulfate product was visually determined.

[0112] The raw materials and equipment specifications used in the synthesis of the reverse demulsifier of this invention are shown in Table 1.

[0113] Table 1. Raw Material / Equipment Specifications and Sources

[0114]

[0115]

[0116] Example 1

[0117] (1) Add 50 ml of methyl isobutyl ketone and 20 g of azobisisobutyronitrile to the reaction vessel, heat to 50 °C and stir for 10 min to completely dissolve the initiator, then add 25 mg of KOH, heat to 90 °C and dehydrate under vacuum for 30 min, then add 5 g of propylene oxide, heat to 100-120 °C and react while controlling the pressure at 0.2 MPa. After the reaction is completed for 1 h, filter to remove the filter residue to obtain an oil head solution containing azo polyether.

[0118] (2) Add the azo polyether oil head solution prepared in the above steps and 0.3g KOH to the reaction vessel, dehydrate under vacuum at 90℃ for 30min, raise the temperature to 110℃ and introduce 75g ethylene oxide, control the pressure to be less than 0.4Mpa, maintain the temperature and react for 0.5-3h, then add 270g propylene oxide and control the pressure to be 0.2Mpa, maintain the temperature and react for 12h, and then filter to obtain the block azo polyether solution.

[0119] (3) Add the block azo polyether solution prepared in the above steps to a batch reactor, heat to 80°C, then add 0.68g of crosslinking agent epichlorohydrin, maintain the temperature for 1h, and after the reaction is completed, add 30ml of methyl isobutyl ketone for dilution to obtain crosslinked polyether solution.

[0120] (4) Add 30 ml of dodecyltrimethylammonium chloride aqueous solution (40 wt%) to the cross-linked polyether solution obtained in the above steps. The addition time is 2 h. Keep stirring during the addition. After the addition is completed, heat the above reaction system to 95 °C and stir the reaction for 3 h. Take out the mixture and let it stand for 5 h. Separate the upper oil phase and remove the solvent by vacuum distillation to obtain the nonionic-cationic composite reverse demulsifier, which is numbered demulsifier 1.

[0121] Example 2

[0122] The difference between this embodiment and embodiment 1 is that 20g of azobisisobutyronitrile in step (1) is changed to 24g of azobisisovalerate, and finally demulsifier 2 is obtained.

[0123] Example 3

[0124] The difference between this embodiment and embodiment 1 is that 20g of azobisisobutyronitrile in step (1) is changed to 30g of azobisisoheptanenitrile, and finally demulsifier 3 is obtained.

[0125] Example 4

[0126] The difference between this embodiment and embodiment 1 is that dodecyltrimethylammonium chloride in step (4) is replaced with hexadecyltrimethylammonium chloride, and demulsifier 4 is finally obtained.

[0127] Comparative Example 1

[0128] The process flow of the equipment is as follows Figure 2 As shown in Table 2 (the same reference numerals are used for devices identical to those in this invention), the evaporation rate / flow rate of each device is as follows. First, the dilute ammonium sulfate solution from the quench tower is introduced into the evaporator crystallizer 1. After evaporation and concentration, evaporation condensate, crystalline solids, and evaporation concentrate are produced. The evaporation condensate is directly discharged. The crystalline ammonium sulfate solids, carrying a certain amount of solution, are pumped into the thickener 5. The material discharged from the bottom of the thickener 5 is centrifuged by the solid-liquid centrifuge 6 to remove water and obtain the ammonium sulfate product. The overflow circulating liquid at the top of the thickener 5 is returned to the evaporator crystallizer 1. The evaporation concentrate from the evaporator crystallizer 1 enters the vertical first oil-water separator 3a. The concentrate is separated into oil and water by gravity settling inside the separator. Acrylonitrile wastewater is introduced into the oil phase outlet at the top of the separator to dilute the upper oil phase. The acrylonitrile wastewater and the oil phase enter the oil-water mixer 7 for stirring and dilution before entering the incineration unit. The aqueous phase is returned to the evaporator crystallizer 1 from the bottom outlet of the separator. The oil content of the aqueous phase at the bottom of the first oil-water separator was 158 mg / L, and the ammonium sulfate content of the oil phase at the top of the first oil-water separator was 19 wt%. The ammonium sulfate product had a reddish-brown appearance.

[0129] Table 2 Evaporation / Flow Rate at Various Locations

[0130]

[0131]

[0132] Comparative Example 2

[0133] in accordance with Figure 1 The process flow does not add a reverse demulsifier, does not use a second oil-water separator, and the concentrated liquid from the evaporator crystallizer directly enters the first oil-water separator. The first oil-water separator is the first oil-water separator-1 (250ml, length / height ratio of 3:1) shown in Table 1. The residence time of the concentrated liquid in the first oil-water separator is 1 hour. The evaporation rate / flow rate of each part is shown in Table 3. The oil content of the influent water (i.e. acrylonitrile sulfuric acid wastewater) of the evaporator crystallizer is 245mg / L. After the device has been running continuously for 8 hours, the oil content of the aqueous phase at the bottom of the first oil-water separator is 120mg / L. The ammonium sulfate content of the oil phase at the top of the first oil-water separator is 8wt%. The ammonium sulfate product has a dark yellow appearance.

[0134] Table 3 Evaporation / Flow Rate at Various Locations

[0135]

[0136] Comparative Example 3

[0137] The difference between the wastewater treatment method in this comparative example and that in Comparative Example 2 is that the first oil-water separator is replaced with the first oil-water separator-2 (450ml, length / height ratio of 5:1) in Table 1. The residence time of the concentrate in the first oil-water separator is 2 hours. After the device has been running continuously for 8 hours, the oil content of the aqueous phase at the bottom of the first oil-water separator is 97mg / L, and the ammonium sulfate content of the oil phase at the top of the first oil-water separator is 5wt%. The ammonium sulfate product has a dark yellow appearance.

[0138] Comparative Example 4

[0139] The difference between the wastewater treatment method in this comparative example and that in Comparative Example 2 is that the first oil-water separator is replaced with the first oil-water separator-3 (600ml, length / height ratio of 7:1) in Table 1. The residence time of the concentrate in the first oil-water separator is 3h. After the device has been running continuously for 8h, the oil content of the aqueous phase at the bottom of the first oil-water separator is 95mg / L, and the ammonium sulfate content of the oil phase at the top of the first oil-water separator is 5wt%. The ammonium sulfate product is dark yellow in appearance.

[0140] Example 5

[0141] The difference between this embodiment and Comparative Example 2 is that a reverse demulsifier SP169 solution (diisopentyl ether as solvent) with a concentration of 0.2 wt% and a flow rate of 0.375 ml / h is introduced into the static mixer. The amount of reverse demulsifier added per unit time is 5 ppm of the flow rate of the evaporation concentrate. The residence time of the reverse demulsifier and the concentrate in the static mixer is 20 min. After the device has been running continuously for 8 h, the oil content of the bottom aqueous phase of the first oil-water separator is analyzed and found to be 95 mg / L. The ammonium sulfate content of the top oil phase of the first oil-water separator is analyzed and found to be 6 wt%. The ammonium sulfate product is dark yellow in appearance.

[0142] Example 6

[0143] The difference between this embodiment and Comparative Example 2 is that a reverse demulsifier SP169 solution (diisopentyl ether as solvent) with a concentration of 0.8 wt% and a flow rate of 0.375 ml / h is introduced into the static mixer. The amount of reverse demulsifier added per unit time is 20 ppm of the flow rate of the evaporation concentrate. The residence time of the reverse demulsifier and the concentrate in the static mixer is 20 min. After the device has been running continuously for 8 h, the oil content of the bottom aqueous phase of the first oil-water separator is analyzed and found to be 90 mg / L. The ammonium sulfate content of the top oil phase of the first oil-water separator is analyzed and found to be 6 wt%. The ammonium sulfate product has a dark yellow appearance.

[0144] Example 7

[0145] The wastewater treatment method in this embodiment differs from that in Embodiment 6 in that a secondary oil-water separator is started to investigate the effect of evaporation and oil removal on the oil content in the aqueous phase and the color of the product. In this embodiment, the evaporation rate of the second oil-water separator is set to 24 ml / h, and the amount of water added is the same as the evaporation rate. After the device runs continuously for 8 hours, the oil content (before adding water) of the aqueous phase at the bottom of the second oil-water separator is analyzed and found to be 75 mg / L. The ammonium sulfate product has a light yellow appearance.

[0146] Example 8

[0147] The wastewater treatment method in this embodiment differs from that in Embodiment 6 in that a secondary oil-water separator is started to investigate the effect of evaporation and oil removal on the oil content in the aqueous phase and the color of the product. In this embodiment, the evaporation rate of the second oil-water separator is set to 40 ml / h, and the amount of water added is the same as the evaporation rate. After the device runs continuously for 8 hours, the oil content (before adding water) of the aqueous phase at the bottom of the second oil-water separator is analyzed and found to be 55 mg / L. The ammonium sulfate product has a light yellow appearance.

[0148] Example 9

[0149] The difference between this embodiment and Comparative Example 2 is that a demulsifier 1 solution with a concentration of 0.2 wt% and a flow rate of 0.375 ml / h is introduced into the static mixer, wherein the amount of reverse demulsifier added per unit time is 5 ppm of the flow rate of the evaporation concentrate. The residence time of the reverse demulsifier and the concentrate in the static mixer is 20 min. After the device has been running continuously for 8 h, the oil content of the aqueous phase at the bottom of the first oil-water separator is analyzed and found to be 15 mg / L. The ammonium sulfate content of the oil phase at the top of the first oil-water separator is analyzed and found to be 3 wt%. The ammonium sulfate product has a light yellow appearance.

[0150] Example 10

[0151] The difference between this embodiment and embodiment 9 is that the concentration of demulsifier 1 solution is 0.4wt%, wherein the amount of reverse demulsifier added per unit time is 10ppm of the flow rate of the evaporation concentrate, and after the device runs continuously for 8 hours, the oil content of the bottom aqueous phase of the first oil-water separator is 12mg / L, and the ammonium sulfate content of the top oil phase of the first oil-water separator is 2wt%. The ammonium sulfate product has a light yellow appearance.

[0152] Example 11

[0153] The difference between this embodiment and embodiment 9 is that the concentration of demulsifier 1 solution is 0.8wt%, wherein the amount of reverse demulsifier added per unit time is 20ppm of the flow rate of the evaporation concentrate, and after the device runs continuously for 8 hours, the oil content of the aqueous phase at the bottom of the first oil-water separator is 10mg / L, and the ammonium sulfate content of the oil phase at the top of the first oil-water separator is 2wt%, and the ammonium sulfate product has a light yellow appearance.

[0154] Example 12

[0155] The difference between this embodiment and embodiment 11 is that the demulsifier is replaced with demulsifier 2, and the ammonium sulfate content in the top oil phase of the first oil-water separator is 1 wt% and the ammonium sulfate product has a light yellow appearance.

[0156] Example 13

[0157] The difference between this embodiment and embodiment 11 is that the demulsifier is replaced with demulsifier 3, and the ammonium sulfate content in the top oil phase of the first oil-water separator is 1 wt% and the ammonium sulfate product is light yellow in appearance.

[0158] Example 14

[0159] The difference between this embodiment and embodiment 11 is that the demulsifier is replaced with demulsifier 4, and the ammonium sulfate content in the top oil phase of the first oil-water separator is 2wt% and the ammonium sulfate product is light yellow in appearance.

[0160] Example 15

[0161] The wastewater treatment method in this embodiment differs from that in Embodiment 11 in that a secondary oil-water separator is started to investigate the effect of evaporation and oil removal on the oil content in the aqueous phase and the color of the product. In this embodiment, the evaporation rate of the second oil-water separator is set to 24 ml / h, and the amount of water added is the same as the evaporation rate. After the device runs continuously for 8 hours, the oil content (before adding water) of the aqueous phase at the bottom of the second oil-water separator is analyzed and found to be 6 mg / L. The ammonium sulfate product is white in appearance.

[0162] Example 16

[0163] The difference between the wastewater treatment method in this embodiment and that in embodiment 15 is that the evaporation rate in this embodiment is set to 30 ml / h, the amount of water added is the same as the evaporation rate, and after the device runs continuously for 8 hours, the oil content (before adding water) of the bottom water phase of the second oil-water separator is analyzed and found to be 5 mg / L. The ammonium sulfate product is white in appearance.

[0164] Example 17

[0165] The difference between the wastewater treatment method in this embodiment and that in embodiment 15 is that the evaporation rate in this embodiment is set to 40 ml / h, the amount of water added is the same as the evaporation rate, and after the device runs continuously for 8 hours, the oil content of the water phase in the bottom discharge liquid of the second oil-water separator (before adding water) is 2 mg / L, and the ammonium sulfate product is white in appearance.

[0166] Example 18

[0167] The difference between the wastewater treatment method in this embodiment and that in embodiment 17 is that the demulsifier is replaced with demulsifier 2. After the device has been running continuously for 8 hours, the oil content of the water phase in the bottom discharge liquid of the second oil-water separator (before adding water) is 5 mg / L, and the ammonium sulfate product is white in appearance.

[0168] Example 19

[0169] The difference between the wastewater treatment method in this embodiment and that in embodiment 17 is that the demulsifier is replaced with demulsifier 3. After the device has been running continuously for 8 hours, the oil content of the water phase in the bottom discharge liquid of the second oil-water separator (before adding water) is 3 mg / L, and the ammonium sulfate product is white in appearance.

[0170] Example 20

[0171] The difference between the wastewater treatment method in this embodiment and that in embodiment 17 is that the demulsifier is replaced with demulsifier 4. After the device has been running continuously for 8 hours, the oil content of the water phase in the bottom discharge liquid of the second oil-water separator (before water is added) is 6 mg / L, and the ammonium sulfate product is white in appearance.

[0172] As can be seen from Comparative Examples 1-4, the horizontal oil-water separator in the device provided by the present invention has a better oil-water separation effect than the existing vertical oil-water separator. As can be seen from Examples 5-8, the use of existing reverse demulsifiers can improve the oil-water separation problem to a certain extent. As can be seen from Examples 9-20, the addition of the reverse demulsifier of the present invention significantly reduces the oil content in the aqueous phase and the ammonium sulfate content in the oil phase. Combined with the second oil-water separator in the device provided by the present invention, it can achieve deep removal of residual emulsified oil and dissolved oil in the aqueous phase, further improving the oil-water separation effect and making the ammonium sulfate product white in color.

[0173] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for treating acrylonitrile ammonium sulfate wastewater, characterized in that, Includes the following steps: Step 1: Evaporate and crystallize the acrylonitrile ammonium sulfate wastewater to obtain evaporation condensate, crystalline solid and evaporation concentrate; Step 2: The evaporated concentrate is mixed with a reverse demulsifier; Step 3: The mixture obtained in Step 2 is subjected to the first oil-water separation under gravity sedimentation to obtain an oil phase and an aqueous phase; Step 4: The aqueous phase undergoes a second oil-water separation, which is carried out by evaporation. After evaporation, the remaining mixture is mixed with the acrylonitrile ammonium sulfate wastewater and then recycled for further evaporation and crystallization. The preparation method of the reverse demulsifier includes: Step a involves reacting azodicarbonyl with propylene oxide via a ring-opening polymerization reaction to obtain azopolyether oil head; Step b involves copolymerizing the azo polyether oil head, ethylene oxide, and propylene oxide to obtain a block azo polyether. Step c involves subjecting the block azo polyether to a crosslinking reaction under the action of a crosslinking agent to obtain a crosslinked polyether. Step d: The cross-linked polyether and the quaternary ammonium salt are reacted under heating to obtain an oil-soluble reverse demulsifier; In step a, the mass ratio of the azodicarbonamide to propylene oxide is 2:1 to 8:

1.

2. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The ratio of the flow rate of the evaporating condensate to the flow rate of the acrylonitrile ammonium sulfate wastewater is 1:(1-5); the ratio of the flow rate of the evaporating concentrate to the flow rate of the acrylonitrile ammonium sulfate wastewater is 1:(1-3).

3. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The first oil-water separation is carried out in a horizontal separation tank, the ratio of the height to the length of the horizontal separation tank being 1:(2-10).

4. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The ratio of the flow rate of the acrylonitrile ammonium sulfate wastewater to the flow rate of the oil phase in step 3 is (1-5):1; in step 3, the ratio of the flow rate of the aqueous phase to the flow rate of the oil phase is (1-5):

1.

5. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The evaporation yields an oil-containing aqueous phase and a remaining mixture. The oil-containing aqueous phase is mixed with the evaporation concentrate and a reverse demulsifier. The flow rate ratio of the oil-containing aqueous phase to the flow rate of the aqueous phase is 1:(3-10).

6. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The azodiacetonitrile is one of azobisisobutyronitrile, azobisisovalerate, and azobisisoheptanenitrile; the reaction of the azodiacetonitrile with propylene oxide is carried out in the presence of a ring-opening polymerization catalyst and an oil-soluble solvent, wherein the ring-opening polymerization catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide; and the oil-soluble solvent is one of acetone, methyl ethyl ketone, methyl isobutyl ketone, and tetrahydrofuranone.

7. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 6, characterized in that, In step a, the amount of the ring-opening polymerization catalyst is 0.05-0.3% of the total mass of azodiazepine and propylene oxide; the reaction temperature of the azodiazepine and propylene oxide is 100-120℃, and the reaction time is 1-3h.

8. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, In step b, the reaction of the azo polyether oil head, ethylene oxide and propylene oxide is carried out under the action of a ring-opening polymerization catalyst, which is one of sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide, and the amount of the ring-opening polymerization catalyst is 0.05-0.3% of the total mass of the azo polyether oil head, ethylene oxide and propylene oxide.

9. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The reaction temperature of the azo polyether oil head, ethylene oxide and propylene oxide is 110-120℃, the mass ratio of the azo polyether oil head to ethylene oxide is 1:2-1:5, and the mass ratio of the azo polyether oil head to propylene oxide is 1:8-1:

12.

10. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The crosslinking agent is epichlorohydrin, and the mass ratio of the block azo polyether to the crosslinking agent is 500:1-600:

1.

11. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The cross-linking reaction is carried out at a temperature of 60-80℃ for 1-3 hours.

12. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The quaternary ammonium salt is one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride, and the amount of the quaternary ammonium salt used is 20-30% of the mass of the crosslinked polyether.

13. The method for treating acrylonitrile ammonium sulfate wastewater according to claim 1, characterized in that, The heating temperature in step d is 80-95℃, and the reaction time is 3-5h. The reaction mixture of the crosslinked polyether and the quaternary ammonium salt is subjected to oil-water separation, and the resulting oil phase is distilled to obtain an oil-soluble reverse demulsifier.

14. The method for treating acrylonitrile ammonium sulfate wastewater according to any one of claims 1-13, characterized in that, This treatment method utilizes a treatment system for acrylonitrile ammonium sulfate wastewater, which includes: An evaporator crystallizer is used for the evaporation and crystallization of acrylonitrile ammonium sulfate wastewater to obtain evaporated condensate, crystalline solids, and evaporated concentrate. A static mixer, connected to the evaporator crystallizer, is used to mix the evaporation concentrate with the reverse demulsifier; The first oil-water separator is connected to the static mixer and is used to perform the first oil-water separation of the mixture in the static mixer under the action of gravity sedimentation to obtain an oil phase and a water phase. The second oil-water separator is an evaporator, which is connected to the first oil-water separator and the evaporator crystallizer respectively. It is used to evaporate the aqueous phase, and the remaining mixture after evaporation is recycled back to the evaporator crystallizer for further evaporation and crystallization.

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