CN112499831B - Method for treating phosphorus-containing wastewater in caprolactam production - Google Patents
Method for treating phosphorus-containing wastewater in caprolactam production Download PDFInfo
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Abstract
The invention discloses a method for treating phosphorus-containing wastewater in caprolactam production, which comprises the following steps: step one, mixing: obtaining a mixed solution; step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 2-4m/s for 5-10min to fully react the materials, then reducing the stirring speed to 0.5-2m/s, slowly adding a flocculating agent, stirring for 5-10min, and fully dissolving to obtain a reaction mixed solution; step three, precipitation separation: separating solid and liquid, pumping the sludge into a filter press by a pump for filter pressing treatment, further separating the solid and the phosphorus removal liquid, transferring the phosphorus removal liquid into a wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge. The phosphorus removal method of the invention effectively treats the phosphorus-containing wastewater and has great promotion effect on the production and development of caprolactam industry.
Description
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a method for treating phosphorus-containing wastewater in caprolactam production.
Background
In the ammoximation process of caprolactam production flow, phosphorus-containing sewage with pH of 7-9 and phosphorus content of 20-150mg/m can be produced 3 And the direct discharge of phosphorus-containing sewage can cause eutrophication of water body and serious environmental pollution. In order to ensure sustainable development, the phosphorus-containing wastewater is treated, and the higher-level aims of saving energy, reducing consumption, reducing treatment cost, avoiding secondary pollution and the like are also achieved. Therefore, the development of a high-efficiency phosphorus-containing wastewater treatment method is of great significance.
CN201310418193.8 discloses a treatment method of phosphorus-containing waste liquid, which comprises the following steps: reacting the phosphorus-containing waste liquid with phosphorus pentachloride to obtain phosphorus oxychloride; the phosphorus-containing waste liquid contains ions shown in the formula (I), and the method realizes the resource utilization of the waste liquid generated by synthesizing the 4, 6-dichloropyrimidine by reacting the phosphorus-containing waste liquid with the phosphorus pentachloride, so that the phosphorus oxychloride is recycled, and the waste of resources and the pollution of the phosphorus-containing waste liquid to the environment are avoided.
CN201821050119.X discloses a device for treating phosphorus-containing waste liquid, which comprises a tower body, a circulating pump and a static mixer, wherein one side of the lower part of the tower body is provided with a closed reaction box, the upper part of the reaction box is communicated with the lower part of the tower body, the lower end of the tower body and the lower end of the reaction box are connected with an air stirring device, the middle part of the tower body is provided with a spraying device, chlorine generated in the reaction process enters the spraying device in the middle part of the tower body through the stirring and blowing of the air stirring device and the communication position between the upper part of the reaction box and the lower part of the tower body, the circulating pump extracts waste liquid in a mixing tank at the lower part of the tower body to be spraying water, the spraying device absorbs chlorine in tail gas, the absorbed tail gas is subjected to tissue discharge through a chimney after liquid entrainment of a demisting packing layer, and the device can effectively utilize the chlorine as a side reaction product in the process of treating the phosphorus-containing waste water and effectively avoid secondary pollution.
CN201410673626.9 discloses a comprehensive utilization method of wastewater containing phosphorus and fluorine, by carrying out neutralization twice on the wastewater containing phosphorus and fluorine and controlling the pH value of the end point after each neutralization, further separating calcium fluoride in the wastewater according to the solubility product of the calcium fluoride and the calcium phosphate salt so that the main components in the wastewater are the calcium phosphate salt and silica gel, and after the silica gel is separated out by centrifugal separation, the phosphorus-containing waste liquid is obtained and then is neutralized for the second time, further leading the PH value to be 4-7, further generating calcium hydrophosphate, then cooling and crystallizing, separating calcium hydrophosphate to obtain clear liquid, further achieving the treatment of wastewater containing phosphorus and fluorine, the method not only recycles the phosphorus and fluorine resources to the maximum extent, but also generates a byproduct of silica gel, improves the added value of products, and reduces the cost of treating the phosphorus and fluorine-containing wastewater.
Several treatment methods of phosphorus-containing waste liquid in the prior art have respective advantages and disadvantages, and the principle of the chemical precipitation phosphorus removal method is to remove phosphorus in the waste water by using a method of generating insoluble phosphate precipitation by reacting iron salt, aluminum salt or lime and the like with phosphate radical. The method has more problems: (1) the lime method for removing phosphorus has large sludge amount, difficult solid waste treatment and high cost; (2) the phosphorus removal cost of the iron salt and the aluminum salt is high, strong corrosion is generated on equipment, and the requirement on the material of the equipment is high; (3) the dephosphorization process has the advantages of complex route, long flow, more equipment, high construction cost, high equipment failure rate, complex operation and the like; (4) the phosphorus removal effect is not ideal, the phosphorus removal efficiency of iron salt and aluminum salt is 70-80%, and the phosphorus removal efficiency of lime is about 90%. The biological phosphorus removal method mainly comprises an A/O process, an A2/O process, an SBR process and the like. The biological phosphorus removal has the advantages of energy conservation and low operating cost, and has the defects of large occupied area, high initial investment and poor impact resistance. The biological phosphorus removal method not only considers the influence of the process parameters of biodegradation organic content, total phosphorus concentration, ammonia nitrogen and the like on the inlet water, but also considers the influence of factors such as the size of a structure and the like. Therefore, the biological phosphorus removal is unstable, and the method cannot adapt to the treatment of high-phosphorus wastewater. The electrodialysis method is a membrane separation technology, which utilizes the voltage applied between the cathode and anode membrane pairs to remove the solid in the water solution, can generate high and low two streams of phosphorus-containing sewage, then uses metal salt to precipitate the high phosphorus-containing sewage, and is also a chemical phosphorus removal process which cannot be separated, and has high treatment cost and complex operation and maintenance. The ion exchange dephosphorization method has high cost, overcomes the competition of other anions, has short service life of the resin and is difficult to be industrially popularized at present.
Phosphorus-containing wastewater in caprolactam production is mainly brought by hydrogen peroxide, and the residual hydrogen peroxide has a strong sterilization effect and cannot directly enter a biochemical device for treatment. The phosphorus removal by adopting the traditional chemical method also has the problems of large early-stage investment, high operation cost, unsatisfactory treatment effect, harsh operating environment of workers and the like. Therefore, it becomes an urgent need to find a phosphorus removal method with low investment, impact resistance and simple operation for phosphorus-containing wastewater in caprolactam production.
Disclosure of Invention
The phosphorus removal method has the advantages of simple process, low investment, low operation cost, good treatment effect and low failure rate, effectively treats the phosphorus-containing wastewater, and has a great promotion effect on the production and development of caprolactam industry.
A method for treating phosphorus-containing wastewater in caprolactam production is characterized by comprising the following steps:
step one, mixing: the phosphorus content is 50-100mg/m 3 The phosphorus-containing wastewater has a particle size of 20-25m 3 The flow of the phosphorus removal agent/h transversely enters the flow stabilizing barrel through the upper inlet and the middle inlet of the radial flow type flow stabilizing barrel, and meanwhile, the phosphorus removal agent vertically enters the flow stabilizing barrel from the upper inlet of the flow stabilizing barrel at the flow of 10-20L/h to obtain mixed liquid;
step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 2-4m/s for 5-10min to enable the materials to fully react, then reducing the stirring speed to 0.5-2m/s, slowly adding a flocculating agent, stirring for 5-10min, and fully dissolving to obtain a reaction mixed solution;
step three, precipitation separation: opening a valve at the bottom of the steady flow barrel, enabling the reaction mixed liquid to flow into a radial flow type sedimentation tank, staying for 3-5 hours, enabling solid and liquid to be separated, enabling the liquid to enter a wastewater collection tank through a cofferdam above the sedimentation tank, enabling solid precipitates to enter a sludge area of the radial flow type sedimentation tank, pumping sludge into a filter press by a pump for filter pressing treatment, further separating the solid and phosphorus removal liquid, transferring the phosphorus removal liquid into the wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge.
Preferably, the preparation method of the phosphorus removal agent in the first step comprises the following steps:
adding 80-120 parts by mass of the steel pickling waste liquid into a reaction kettle, adding 1-2 parts by mass of a mixed heavy metal trapping agent HMC-M1, stirring for 30-60min at 200r/min, standing for 4-8h, and separating liquid and precipitate; transferring the liquid into a vacuum flash tank, and controlling the temperature to be 50-60 DEG C o C, the vacuum degree is-0.08 to-0.09, the hydrogen chloride obtained by separation is introduced into a reaction kettle filled with pure water, hydrochloric acid is obtained for recovery, the ferrous chloride solution obtained by separation is reserved, and the precipitate is treated as sludge; and then adding 10-20 parts of calcium chloride into the ferric chloride solution, and dissolving to obtain the calcium-iron composite dephosphorizing agent.
Preferably, the preparation method of the flocculant in the step two comprises the following steps:
according to the mass portion, 40-60 portions of acrylamide, 30-50 portions of acryloyloxyethyl trimethyl ammonium chloride, 30-50 portions of dimethylaminoethyl methacrylate, 5-8 portions of methyl vinyl cyclosiloxane, 0.005-0.028 portion of 1-vinyl-3-butyl imidazole tetrafluoroborate and 300 portions of deionized water are added into a reaction kettle, stirred for 30-60min at the speed of 100-200r/min, fully dissolved, the PH of the solution is adjusted to be 2.5-3.5, then 0.05-0.15 portion of oxidant, 0.05-0.15 portion of reducing agent and 0.05-0.15 portion of initiator are added while stirring, nitrogen is introduced to remove air in the reaction kettle, and then the solution in the reaction kettle is heated to 25-45 portions o And C, reacting for 4-8h, centrifuging, drying and crushing the polymer obtained by the reaction to obtain the flocculant.
Preferably, the oxidant is one or a combination of sodium persulfate, potassium persulfate and ammonium persulfate.
Preferably, the reducing agent is one or a combination of more of sodium formaldehyde sulfoxylate, sodium sulfite and sodium thiosulfate.
Preferably, the initiator is one or a combination of more of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, 2-azo [2- (2-imidazoline-2-yl) propane ] dihydrochloride and 2, 2-azo (2-amidinopropane) dihydrochloride.
Preferably, the filter press in the third step is one of a plate and frame filter press, a belt filter press, a box filter press and a vertical press.
Part of reaction mechanism in the preparation process of the flocculant is shown as follows:
compared with the prior art, the invention has the beneficial effects that:
1. the PH value of the phosphorus-containing wastewater generated in the ammoximation process in caprolactam production is about 11, and the PH value of the wastewater does not need to be additionally adjusted in the treatment process.
2. Short process flow, small occupied area, low investment, simple operation and low failure rate.
3. The processing capacity is large, the effect is stable, the load fluctuation resistance is strong, the impact resistance is high, and the industrial popularization value is realized.
4. The phosphorus removal agent is prepared by using the steel pickling waste liquid as a raw material, so that the phosphorus-containing waste water is treated, the steel pickling waste liquid is recycled, two purposes are achieved, and the effects of low operation cost and low investment are achieved.
5. By adding a self-made flocculating agent and introducing functional groups such as cyclosiloxane, imidazole tetrafluoroborate and the like, the flocculating density is increased, the speed is increased, the solid-liquid separation efficiency is improved, and the contents of heavy metal ions and phosphorus in the obtained waste liquid are greatly reduced.
Drawings
FIG. 1 is a Fourier Infrared Spectroscopy of the flocculant obtained in example 1:
at 2938cm -1 The expansion absorption peak of carbon-hydrogen bond is at 1721cm -1 The telescopic absorption peak of carbonyl of amide exists nearby and is 1276cm -1 The absorption peak of expansion and contraction of the carbon-nitrogen single bond of the amide is found at 3412cm -1 The expansion absorption peak of the nitrogen-hydrogen bond exists nearby, which indicates that acrylamide participates in the reaction; at 1104cm -1 A symmetric telescopic absorption peak of ester carbon-oxygen single bond is present nearby and is 960cm -1 An absorption peak of a carbon-nitrogen single bond exists nearby, so that the acryloyloxyethyl trimethyl ammonium chloride and the dimethylaminoethyl methacrylate participate in the reaction; at 652cm -1 A stretching absorption peak of silicon-carbon bond exists nearby, so that the methylvinylcyclosiloxane participates in the reaction; at 1054cm -1 A stretching shock absorption peak of B-F exists nearby, and the 1-vinyl-3-butylimidazole tetrafluoroborate participates in the reaction; no obvious absorption peak is formed near 1600cm-1, which indicates that the carbon-carbon double bond has fully polymerized.
Detailed Description
The starting materials used in the following examples are all commercially available products and the examples are intended to further illustrate the invention and not to limit the scope of the invention.
The performance test methods are as follows:
1. the phosphorus content test method adopts an ammonium molybdate spectrophotometry and tests according to the GB 4482-2006 standard.
2. A heavy metal content testing method, according to the water quality monitoring standards GBT 7475-87 and GBT 11912-
89. HJ 757-2015, and calculating the total content of Pb, Zn, Ni and Cr in water by flame atomic absorption spectrophotometry.
3. The COD test method adopts a dichromate method and tests according to the standard of HJ 828-.
Example 1, step one, mixing: the phosphorus content is 50mg/m 3 The phosphorus-containing wastewater has a particle size of 25m 3 Enabling the flow of per hour to transversely discharge into the flow stabilizing barrel through the upper inlet and the middle inlet of the radial flow type flow stabilizing barrel, and meanwhile, vertically discharging a phosphorus removing agent into the flow stabilizing barrel from the upper inlet of the flow stabilizing barrel at the flow of 10L per hour to obtain a mixed solution;
step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 2m/s for 10min to fully react the materials, then reducing the stirring speed to 0.5m/s, slowly adding a flocculating agent, stirring for 10min, and fully dissolving to obtain a reaction mixed solution;
step three, precipitation separation: opening a valve at the bottom of the steady flow barrel, enabling the reaction mixed liquid to flow into a radial flow type sedimentation tank, staying for 3 hours, separating solid from liquid, enabling the liquid to enter a wastewater collection tank through a cofferdam above the sedimentation tank, enabling solid precipitates to enter a sludge area of the radial flow type sedimentation tank, pumping the sludge into a plate and frame type filter press by a pump for medium pressure filtration treatment, further separating the solid and the phosphorus removal liquid, transferring the phosphorus removal liquid into the wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge.
The preparation method of the phosphorus removing agent in the first step comprises the following steps:
adding 80kg of steel pickling waste liquor into a reaction kettle, adding 1kg of mixed heavy metal trapping agent HMC-M1, and stirring at 100r/minStirring for 60min, standing for 4h, and separating liquid and precipitate; the liquid was then transferred to a vacuum flash tank, with a temperature control of 50 deg.f o C, the vacuum degree is-0.08, the hydrogen chloride obtained by separation is introduced into a reaction kettle filled with pure water, hydrochloric acid is obtained for recovery, the ferrous chloride solution obtained by separation is reserved, and the precipitate is used as sludge for treatment; then 10kg of calcium chloride is added into the ferric chloride solution and dissolved to obtain the calcium-iron composite dephosphorizing agent.
The preparation method of the flocculant in the step two comprises the following steps:
adding 40kg of acrylamide, 30kg of acryloyloxyethyl trimethyl ammonium chloride, 30kg of dimethylaminoethyl methacrylate, 5kg of methyl vinyl cyclosiloxane, 0.005 kg of 1-vinyl-3-butylimidazole tetrafluoroborate (CAS: 1033461-44-7) and 300kg of deionized water into a reaction kettle, stirring at 100r/min for 60min to fully dissolve the acrylamide, adjusting the pH of the solution to 2.5, then adding 0.05kg of sodium persulfate, 0.05kg of sodium formaldehyde sulfoxylate and 0.05kg of azodiisobutyl amidine hydrochloride while stirring, introducing nitrogen to remove air in the reaction kettle, heating the solution in the reaction kettle to 25% o And C, reacting for 8 hours, centrifuging, drying and crushing the polymer obtained by the reaction to obtain the flocculant.
The phosphorus concentration in the obtained wastewater is 1.6mg/m 3 The heavy metal content is 0.5mg/L, and the COD is 50 mg/L. Example 2, step one, mixing: the phosphorus content is 70mg/m 3 The phosphorus-containing wastewater has a particle size of 24m 3 Enabling flow of per hour to transversely discharge into the flow stabilizing barrel through the upper inlet and the middle inlet of the radial flow type flow stabilizing barrel, and meanwhile, vertically discharging a phosphorus removing agent into the flow stabilizing barrel from the upper inlet of the flow stabilizing barrel at the flow of 13L per hour to obtain mixed liquid;
step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 2m/s for 8min to fully react the materials, then reducing the stirring speed to 1m/s, slowly adding a flocculating agent, stirring for 8min, and fully dissolving to obtain a reaction mixed solution;
step three, precipitation separation: opening a valve at the bottom of the steady flow barrel, enabling the reaction mixed liquid to flow into a radial flow type sedimentation tank, staying for 3 hours, separating solid from liquid, enabling the liquid to enter a wastewater collection tank through a cofferdam above the sedimentation tank, enabling solid precipitates to enter a sludge area of the radial flow type sedimentation tank, pumping the sludge into a belt type filter press for medium pressure filtration treatment by using a pump, further separating the solid from the phosphorus removal liquid, transferring the phosphorus removal liquid into the wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge.
The preparation method of the phosphorus removing agent in the first step comprises the following steps:
adding 90kg of steel pickling waste liquid into a reaction kettle, adding 1kg of mixed heavy metal trapping agent HMC-M1, stirring for 50min at a speed of 120r/min, standing for 4h, and separating liquid and precipitate; then transferring the liquid into a vacuum flash tank, controlling the temperature to be 53 ℃ and the vacuum degree to be-0.08, introducing the hydrogen chloride obtained by separation into a reaction kettle filled with pure water to obtain hydrochloric acid for recycling, and separating to obtain a ferrous chloride solution for later use, wherein the precipitate is treated as sludge; and then adding 14kg of calcium chloride into the ferric chloride solution, and dissolving to obtain the calcium-iron composite dephosphorizing agent.
The preparation method of the flocculant in the step two comprises the following steps:
adding 45kg of acrylamide, 34kg of acryloyloxyethyl trimethyl ammonium chloride, 37kg of dimethylaminoethyl methacrylate, 6kg of methyl vinyl cyclosiloxane, 0.007 kg of 1-vinyl-3-butylimidazolium tetrafluoroborate (CAS: 1033461-44-7) and 323kg of deionized water into a reaction kettle, stirring at 126r/min for 49min to fully dissolve the acrylamide, adjusting the pH of the solution to 2.7, adding 0.07kg of potassium persulfate, 0.08kg of sodium sulfite and 0.08kg of azobisisobutylimidazoline hydrochloride while stirring, introducing nitrogen to remove air in the reaction kettle, heating the solution in the reaction kettle to 32 ℃ for 6h of reaction, centrifuging, drying and crushing a polymer obtained by the reaction to obtain the flocculant.
The phosphorus concentration in the obtained wastewater is 1mg/m3, the heavy metal content is 0.3mg/L, and the COD is 44 mg/L. Example 3, step one, mixing: transversely discharging phosphorus-containing wastewater with the phosphorus content of 83mg/m3 into a flow stabilization barrel through upper and middle inlets of a radial flow type flow stabilization barrel at the flow rate of 21m3/h, and vertically discharging a phosphorus removing agent into the flow stabilization barrel from an upper inlet of the flow stabilization barrel at the flow rate of 17L/h to obtain a mixed solution;
step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 2m/s for 5min to fully react the materials, then reducing the stirring speed to 1.4m/s, slowly adding a flocculating agent, stirring for 6min, and fully dissolving to obtain a reaction mixed solution;
step three, precipitation separation: opening a valve at the bottom of the steady flow barrel, enabling the reaction mixed liquid to flow into a radial flow type sedimentation tank, staying for 3 hours, separating solid from liquid, enabling the liquid to enter a wastewater collection tank through a cofferdam above the sedimentation tank, enabling solid precipitates to enter a sludge area of the radial flow type sedimentation tank, pumping the sludge into a box type filter press by a pump for medium pressure filtration treatment, further separating the solid and the phosphorus removal liquid, transferring the phosphorus removal liquid into the wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge.
The preparation method of the phosphorus removing agent in the first step comprises the following steps:
adding 98kg of steel pickling waste liquid into a reaction kettle, adding 1kg of mixed heavy metal trapping agent HMC-M1, stirring for 44min at 153r/min, standing for 5h, and separating liquid and precipitate; then transferring the liquid into a vacuum flash tank, controlling the temperature to be 55 ℃ and the vacuum degree to be-0.08, introducing the hydrogen chloride obtained by separation into a reaction kettle filled with pure water to obtain hydrochloric acid for recycling, and separating to obtain a ferrous chloride solution for later use, wherein the precipitate is treated as sludge; and then adding 17kg of calcium chloride into the ferric chloride solution, and dissolving to obtain the calcium-iron composite dephosphorizing agent.
The preparation method of the flocculant in the step two comprises the following steps:
51kg of acrylamide, 40kg of acryloyloxyethyl trimethyl ammonium chloride, 43kg of dimethylaminoethyl methacrylate, 7kg of methyl vinyl cyclosiloxane, 0.011 kg of 1-vinyl-3-butylimidazolium tetrafluoroborate, namely CAS, 1033461-44-7 and 331kg of deionized water are added into a reaction kettle, stirred at 159r/min for 35min to be fully dissolved, the pH of the solution is adjusted to be 3.1, then 0.1kg of ammonium persulfate, 0.1kg of sodium thiosulfate and 0.1kg of 2, 2-azo [2- (2-imidazoline-2-yl) propane ] dihydrochloride are added while stirring, nitrogen is introduced to remove air in the reaction kettle, the solution in the reaction kettle is heated to 40 ℃ and reacted for 4h, and the polymer obtained by reaction is centrifuged, dried and crushed to obtain the flocculant.
The phosphorus concentration in the obtained wastewater is 0.7mg/m3, the heavy metal content is 0.1mg/L, and the COD is 37 mg/L. Example 4 step one, mixing: transversely discharging phosphorus-containing wastewater with the phosphorus content of 100mg/m3 into a flow stabilization barrel through upper and middle inlets of a radial flow type flow stabilization barrel at the flow rate of 20m3/h, and vertically discharging a phosphorus removing agent into the flow stabilization barrel from an upper inlet of the flow stabilization barrel at the flow rate of 20L/h to obtain a mixed solution;
step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 4m/s for 5min to fully react the materials, then reducing the stirring speed to 2m/s, slowly adding a flocculating agent, stirring for 5min, and fully dissolving to obtain a reaction mixed solution;
step three, precipitation separation: opening a valve at the bottom of the steady flow barrel, enabling the reaction mixed liquid to flow into a radial flow type sedimentation tank, staying for 5 hours, separating solid from liquid, enabling the liquid to enter a wastewater collection tank through a cofferdam above the sedimentation tank, enabling solid precipitates to enter a sludge area of the radial flow type sedimentation tank, pumping the sludge into a vertical press by a pump for medium pressure filtration treatment, further separating the solid from the phosphorus removal liquid, transferring the phosphorus removal liquid into the wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge.
The preparation method of the phosphorus removing agent in the first step comprises the following steps:
adding 120kg of steel pickling waste liquid into a reaction kettle, adding 2kg of mixed heavy metal trapping agent HMC-M1, stirring for 30min at 200r/min, standing for 8h, and separating liquid and precipitate; then transferring the liquid into a vacuum flash tank, controlling the temperature at 60 ℃ and the vacuum degree at-0.09, introducing the hydrogen chloride obtained by separation into a reaction kettle filled with pure water to obtain hydrochloric acid for recycling, and separating to obtain a ferrous chloride solution for later use, wherein the precipitate is treated as sludge; and then adding 20kg of calcium chloride into the ferric chloride solution, and dissolving to obtain the calcium-iron composite dephosphorizing agent.
The preparation method of the flocculant in the step two comprises the following steps:
adding 60kg of acrylamide, 50kg of acryloyloxyethyl trimethyl ammonium chloride, 50kg of dimethylaminoethyl methacrylate, 8kg of methyl vinyl cyclosiloxane, 0.028 kg of 1-vinyl-3-butyl imidazole tetrafluoroborate, namely CAS:1033461-44-7 and 350kg of deionized water into a reaction kettle, stirring at 200r/min for 30min to fully dissolve the acrylamide, adjusting the pH of the solution to 3.5, then adding 0.15kg of potassium persulfate, 0.15kg of sodium sulfite and 0.15kg of 2, 2-azo (2-amidinopropane) dihydrochloride while stirring, introducing nitrogen to remove air in the reaction kettle, heating the solution in the reaction kettle to 45 ℃, reacting for 4h, centrifuging, drying and crushing a polymer obtained by reaction to obtain the flocculant.
The phosphorus concentration in the obtained wastewater is 0.4mg/m3, the heavy metal content is 0.2mg/L, and the COD is 30 mg/L.
Comparative example 1
Relative to example 1, the amount of flocculant added was 0kg, and the balance was the same as example 1, and the phosphorus concentration in the obtained wastewater was 10mg/m3, the heavy metal content was 0.8mg/L, and the COD was 66 mg/L. Comparative example 2
Compared with the example 1, the flocculant is polyacrylamide, the rest is consistent with the example 1, and the phosphorus concentration in the obtained wastewater is 4.6mg/m 3 The heavy metal content was 0.9mg/L and the COD was 61 mg/L. Comparative example 3
Relative to example 1, the amount of the added phosphorus removal agent is 0kg, the rest is consistent with example 1, and the phosphorus concentration in the obtained wastewater is 48mg/m 3 The heavy metal content was 3.8mg/L and the COD was 71 mg/L.
Claims (6)
1. A method for treating phosphorus-containing wastewater in caprolactam production is characterized by comprising the following steps:
step one, mixing: the phosphorus content is 50-100mg/m 3 The phosphorus-containing wastewater has a particle size of 20-25m 3 The flow of the phosphorus removal agent/h transversely enters the flow stabilizing barrel through the upper inlet and the middle inlet of the radial flow type flow stabilizing barrel, and meanwhile, the phosphorus removal agent vertically enters the flow stabilizing barrel from the upper inlet of the flow stabilizing barrel at the flow of 10-20L/h to obtain mixed liquid;
step two, reaction: starting a steady flow barrel for stirring, stirring the mixed solution at the speed of 2-4m/s for 5-10min to enable the materials to fully react, then reducing the stirring speed to 0.5-2m/s, slowly adding a flocculating agent, stirring for 5-10min, and fully dissolving to obtain a reaction mixed solution;
step three, precipitation separation: opening a valve at the bottom of the steady flow barrel, enabling the reaction mixed liquid to flow into a radial flow type sedimentation tank, staying for 3-5 hours, separating solid from liquid, enabling the liquid to enter a wastewater collection tank through a cofferdam above the sedimentation tank, enabling solid precipitates to enter a sludge area of the radial flow type sedimentation tank, pumping sludge into a filter press by using a pump for filter pressing treatment, further separating the solid and phosphorus removal liquid, transferring the phosphorus removal liquid into the wastewater collection tank, and finally separating to obtain phosphorus removal wastewater and sludge;
the preparation method of the flocculant in the step two comprises the following steps: according to the mass portions, 40 to 60 portions of acrylamide, 30 to 50 portions of acryloyloxyethyl trimethyl ammonium chloride, 30 to 50 portions of dimethylaminoethyl methacrylate, 5 to 8 portions of methyl vinyl cyclosiloxane, 0.005 to 0.028 portion of 1-vinyl-3-butyl imidazole tetrafluoroborate and 300 portions of deionized water are added into a flocculant reaction kettle, stirred for 30 to 60 minutes at a speed of 100 and 200r/min, fully dissolved, the pH value of the solution is adjusted to be 2.5 to 3.5, then 0.05 to 0.15 portion of oxidant, 0.05 to 0.15 portion of reducing agent and 0.05 to 0.15 portion of initiator are added while stirring, nitrogen is introduced to remove air in the flocculant reaction kettle, then the solution in the flocculant reaction kettle is heated to 25 to 45 ℃ for reaction for 4 to 8 hours, the polymer obtained by reaction is centrifuged, drying and crushing to obtain the flocculant.
2. The method of claim 1, wherein the phosphorous removal agent of step one is prepared by: adding 80-120 parts by mass of the steel pickling waste liquid into a dephosphorizing agent reaction kettle, adding 1-2 parts by mass of a mixed heavy metal trapping agent HMC-M1, stirring for 30-60min at 200r/min, standing for 4-8h, and separating liquid and precipitate; then transferring the liquid into a vacuum flash tank, controlling the temperature at 50-60 ℃ and the vacuum degree at-0.08 to-0.09, introducing the hydrogen chloride obtained by separation into a reaction kettle filled with pure water to obtain hydrochloric acid for recycling, and separating to obtain a ferrous chloride solution for later use, wherein the precipitate is treated as sludge; and then adding 10-20 parts of calcium chloride into the ferrous chloride solution, and dissolving to obtain the calcium-iron composite dephosphorizing agent.
3. The method of claim 1, wherein the oxidizing agent is one or more of sodium persulfate, potassium persulfate, and ammonium persulfate.
4. The method of claim 1, wherein the reducing agent is one or more of sodium formaldehyde sulfoxylate, sodium sulfite, and sodium thiosulfate.
5. The method of claim 1, wherein the initiator is one or more selected from the group consisting of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, 2-azo [2- (2-imidazolin-2-yl) propane ] dihydrochloride, and 2, 2-azo (2-amidinopropane) dihydrochloride.
6. The method according to claim 1, wherein the filter press in step three is one of a plate and frame filter press, a belt filter press, a box filter press and a vertical press.
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