CN108726739B - Method for treating acrylonitrile wastewater - Google Patents

Method for treating acrylonitrile wastewater Download PDF

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CN108726739B
CN108726739B CN201810409298.XA CN201810409298A CN108726739B CN 108726739 B CN108726739 B CN 108726739B CN 201810409298 A CN201810409298 A CN 201810409298A CN 108726739 B CN108726739 B CN 108726739B
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wastewater
treatment
acrylonitrile
membrane
tank
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CN108726739A (en
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李俊虎
周珉
王乔
张利华
李译文
陈春玥
罗西子
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Shanghai Chemical Industry Park Sino French Water Development Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/24—Treatment of water, waste water, or sewage by flotation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/463—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrocoagulation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C02F2103/36—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture of organic compounds

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Abstract

The invention relates to a method for treating acrylonitrile wastewater, which comprises the following steps: the method comprises the steps of introducing acrylonitrile wastewater, uniformly mixing, and adjusting the pH value to 6.5-8.5; secondly, sending the mixture into an electric flocculation device for regulation treatment; feeding the three products into an air floatation tank for treatment; fourthly, continuing processing by using a filter; sending to an oxidation pond for oxidation treatment; sixthly, filtering by using an ultrafiltration membrane system; concentration and separation treatment of a reverse osmosis membrane system. The invention does not need to culture biological strains, has short system starting time and strong wastewater concentration fluctuation impact resistance; the electric flocculation and the ozone reaction are adopted, so that iron salt and aluminum salt are not required to be added additionally, and other ions are not introduced additionally into the wastewater; organic matters after comprehensive treatment of the electrocoagulation, the filter and the oxidation pond have small pollution blockage on an ultrafiltration membrane and a reverse osmosis membrane, a system can be stably operated for a longer time, and secondary pollutants are not generated; the treated wastewater can reach the relevant standard regulation, can support the sustainable development of acrylonitrile production, and has considerable economic benefit.

Description

Method for treating acrylonitrile wastewater
Technical Field
The invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for treating acrylonitrile wastewater.
Background
Acrylonitrile is used as an important chemical raw material and is widely applied to the fields of manufacturing acrylic fibers, nitrile rubber, ABS industrial plastics, synthetic resin and the like. At present, acrylonitrile is mostly produced by adopting a propylene ammoxidation method in China, but the produced wastewater mainly contains toxic and harmful substances such as acrylonitrile, acetonitrile, cyanide, acrolein, cyanopyridine and the like and a large amount of organic matters which are difficult to degrade, and the toxic and harmful substances and the organic matters are directly discharged into environmental water bodies to cause high toxicity and potential 'three-cause' toxicity of the water bodies. Therefore, from the viewpoint of environmental protection and the sustainable development of the process for producing acrylonitrile, it is urgent to develop a process for treating acrylonitrile waste water efficiently and economically.
Chinese patent CN201110371133.6 discloses an integrated treatment method of acrylonitrile production wastewater, which adopts the following process flows: regulating tank → A/O biochemical treatment → ultrafiltration → reverse osmosis device; the treatment method adopts an A/O biochemical treatment method to treat acrylonitrile wastewater, and has the following defects: on one hand, the proper flora is difficult to culture, on the other hand, the COD content in the wastewater after the A/O treatment is still higher, the treatment pressure on the subsequent ultrafiltration membrane and reverse osmosis membrane is higher, and the treatment device is more frequent to clean and maintain and cannot stably run for a long time.
Chinese patent CN201410313166.9 discloses a membrane technology integrated treatment method for high-concentration acrylonitrile wastewater, which adopts the following process flows: heat exchange cooling → high efficiency filter filtration → microfiltration or ultrafiltration → nanofiltration membrane → reverse osmosis membrane; the CODcr of the acrylonitrile wastewater treated by the process is 19985.3mg/L, the chroma is 4268 ℃, the turbidity is 232.0NTU, and a high-efficiency filter is used for trapping particle dust and suspended matters below 0.5um, so that a microfiltration membrane or an ultrafiltration membrane is easy to foul and block due to the fact that organic matters in the wastewater cannot be effectively removed, and a wastewater treatment device cannot normally operate; moreover, after the treatment, the CODcr of the wastewater is still about 1000mg/L and can not meet the regulation of GB31571-2015 discharge Standard of pollutants for petrochemical industry.
Chinese patent CN201210122196.2 discloses a method for efficiently denitrifying acrylonitrile production wastewater, which adopts the following process flows: the anoxic tank (A tank) + the aeration tank (O tank) + the secondary sedimentation tank + the oxidation tank + the sedimentation tank. In the process, cyanide-degrading bacteria need to be cultured and enriched, the starting time of the system is long, and chlorinated hydrocarbon in the wastewater is increased when the oxidation pond is oxidized by using sodium hypochlorite, and the chlorinated hydrocarbon is a carcinogenic, teratogenic and mutagenic substance.
Chinese patent CN201410136538.5 disclosesA sequencing batch electro-Fenton device and a sequencing batch electro-Fenton method for the advanced treatment of acrylonitrile wastewater adopt sequencing batch electro-Fenton to treat acrylonitrile wastewater, and FeSO is added before the wastewater enters an electrolytic cell4Sodium sulfate and sodium chloride are added as supporting electrolytes, so that the cost of treating the medicament is increased, and the ion concentration of the treated wastewater is increased.
The existing electric flocculation method for treating wastewater is a decontamination process which utilizes an aluminum or iron anode to dissolve out, generates a high-activity polymorphic polyaluminium or polyferric flocculant in situ, aggregates pollutant particles in a water body into clusters and settles or separates by air flotation. The electric flocculation method has the advantages of high efficiency, small mud amount, easy solid-liquid separation, no need of additional medicament, less secondary pollution, simple control and equipment maintenance, easy automatic control, small Total Dissolved Solids (TDS) in final effluent and the like. Therefore, the electroflocculation method is becoming one of the effective methods for treating inorganic and organic waste water such as heavy metals, fluoride ions and dyes.
Disclosure of Invention
The invention aims to overcome the defects and provide a method for treating acrylonitrile wastewater, which does not need to culture biological strains, has short system starting time, adopts electric flocculation and ozone reaction, does not need to add extra ferric salt and aluminum salt, does not introduce other ions into the wastewater, does not generate secondary pollutants, has the characteristics of simple treatment process, less equipment maintenance frequency, strong impact resistance and low operation cost, can ensure that the treated wastewater can reach the regulation of relevant standards, can support the sustainable development of acrylonitrile production, and has obvious economic benefit.
In order to achieve the purpose, the invention adopts the following technical scheme.
A method for treating acrylonitrile wastewater, wherein the acrylonitrile wastewater is generated in the process of producing acrylonitrile by propylene ammoxidation, and the main pollutants and the concentration range in the wastewater are as follows: COD: 1200-3000 mg/L; TKN: 200-500 mg/L; NH 3-N: 100-250 mg/L; TCN: 30-100 mg/L; the method is characterized by comprising the following steps:
(1) adjusting the pH value of acrylonitrile production wastewater to 6.5-8.5 by using sulfuric acid or sodium hydroxide, then sending the acrylonitrile production wastewater into an adjusting tank provided with a paddle stirrer or a jet flow stirrer, carrying out homogenization, uniform mixing and treatment on the wastewater, and allowing the wastewater to stay in the adjusting tank for at least 4 hours;
(2) feeding the wastewater subjected to homogenizing and uniform quantity regulation in the regulating tank into an electric flocculation device for regulation treatment; the anode of the electric flocculation device is a rod-shaped or plate-shaped material prepared from aluminum or iron, and the cathode of the electric flocculation device is a rod-shaped or plate-shaped material prepared from aluminum, iron or carbon;
(3) sending the wastewater subjected to the electrocoagulation treatment into an air floatation tank for treatment, and adding 5-20 ppm of polyacrylamide; the wastewater after entering the air floatation tank is divided into three parts: separating a part of suspended matter solution from the bottom of the air floatation tank through a sludge discharge system; the two parts of suspended matters with lower density float to the surface of the air floatation tank and are separated by a sludge discharge system; the third part is air floatation effluent containing less suspended matters;
(4) adopting a filter to continuously treat the air flotation effluent: filtering the untreated suspended substances remained in the air-floated effluent to remove part of organic matters, wherein the turbidity of the filtered effluent is less than 10 NTU;
(5) feeding the effluent treated by the filter into an oxidation tank for oxidation treatment, wherein the oxidation tank is provided with an ozone reactor, the ozone reactor adopts micropore aeration, the adding concentration of ozone is 30-200 mg/L, and the retention time of ozone is 0.5-2 h;
(6) filtering the effluent after the oxidation treatment by using an ultrafiltration membrane system, adding a sodium bisulfite solution into the filtered water of the ultrafiltration membrane system, and adjusting the ORP of the wastewater to be within +/-250 mv;
(7) and (4) sending the effluent after the filtration treatment of the ultrafiltration membrane system into a reverse osmosis membrane system for concentration and separation treatment, and discharging the water body after the acrylonitrile wastewater treatment.
Further, the concentration range of iron ions and aluminum ions generated by the electric flocculation device in the wastewater is 10-100 ppm.
Further, the polyacrylamide in the step (3) is a cation, and the molecular weight is 500-2000 ten thousand.
Further, the air floatation device adopted by the air floatation tank in the step (3) is a pressurized dissolved air floatation device, and the dissolved air pressure is 0.25-0.35 Mpa conventionally.
Further, the filter in the step (4) is a sand filter or an activated carbon filter.
Furthermore, the filter can be automatically back-washed by air and water at regular time, and the back-washing period is 0.5-3 h.
Further, adding a catalyst containing active carbon, zeolite, alumina manganese or cobalt into the oxidation pond in the step (5).
Further, the ultrafiltration membrane adopted by the ultrafiltration membrane system in the step (6) is a polyvinylidene fluoride membrane, the membrane is in a flat plate type or hollow fiber type, the filtration pore diameter of the membrane is less than 0.5um, and the running membrane flux of the ultrafiltration membrane is 20-35L/(m) m2×h)。
Further, the reverse osmosis membrane adopted by the reverse osmosis membrane system in the step (7) is a cellulose acetate membrane, an aromatic polyhydrazide membrane or an aromatic polyamide membrane, and the structural form of the membrane is a roll type or a flat plate type.
Furthermore, the desalination rate of the reverse osmosis membrane is more than 95%, the operating pressure is 0.35 Mpa-1.2 Mpa, and the membrane flux is 15-35L/(m)2X h), the recovery rate of the reverse osmosis membrane is 80-90%.
The acrylonitrile wastewater treatment method has the positive effects that:
(1) no need of culturing biological strains, short system starting time and strong wastewater concentration fluctuation impact resistance.
(2) By adopting the electric flocculation and the ozone reaction, iron salt and aluminum salt do not need to be added additionally, and other ions are not introduced additionally into the wastewater.
(3) The organic matters after the comprehensive treatment of the electric flocculation, the filter and the oxidation pond have small pollution blockage to the ultrafiltration membrane and the reverse osmosis membrane, and can stabilize the system to run for a longer time.
(4) The oxidation treatment is carried out by adopting ozone or a catalyst, and secondary pollutants are not generated.
(5) The wastewater treated by the method can reach the reuse standard specified in GB/T19923-2005 urban wastewater recycling industrial water quality, can support the sustainable development of acrylonitrile production, and can bring considerable economic benefit.
Drawings
FIG. 1 is a flow chart of a method for treating acrylonitrile wastewater according to the present invention.
Detailed Description
The following provides a specific embodiment of the method for treating acrylonitrile wastewater according to the present invention, and provides 3 examples and 1 application example. However, it should be noted that the present invention is not limited to the following embodiments.
Example 1
See fig. 1. A method for treating acrylonitrile wastewater comprises the following steps:
(1) the treated acrylonitrile wastewater is wastewater generated in the process of producing acrylonitrile by propylene ammoxidation, and the main pollutants and the concentration range in the wastewater are as follows: COD: 1200-3000 mg/L; TKN: 200-500 mg/L; NH 3-N: 100-250 mg/L; TCN: 30-100 mg/L.
Adjusting the pH value of the acrylonitrile wastewater to 6.5 by using sulfuric acid or sodium hydroxide, then sending the acrylonitrile wastewater into an adjusting tank provided with a paddle stirrer or a jet flow stirrer, carrying out homogenization, uniform mixing and treatment on the wastewater, and staying the wastewater in the adjusting tank for at least 4 hours.
(2) The wastewater after the homogeneous and uniform adjustment of the regulating reservoir is sent into an electric flocculation device for regulation treatment: the anode of the electric flocculation device is a rod-shaped material prepared from aluminum, the cathode of the electric flocculation device is a rod-shaped material prepared from aluminum, and the concentration range of aluminum ions generated by the electric flocculation device in acrylonitrile wastewater is 10-100 ppm.
(3) Sending the wastewater subjected to the electric flocculation treatment into an air floatation tank for treatment: the air floatation tank adopts a pressurized dissolved air floatation device, and the dissolved air pressure is conventional 0.35 Mpa; adding 5ppm of cationic polyacrylamide with molecular weight of 2000 ten thousand; the wastewater after entering the air floatation tank is divided into three parts:
separating a part of suspended matter solution from the bottom of the air floatation tank through a sludge discharge system;
the two parts of suspended matters with lower density float to the surface of the air floatation tank and are separated by a sludge discharge system;
the third part is air-float effluent containing less suspended matters.
(4) Adopting a sand filter to continuously treat the air flotation effluent: filtering the residual untreated suspended matters in the air-floated effluent to remove part of organic matters, wherein the turbidity of the filtered effluent is less than 10 NTU.
(5) Sending the effluent treated by the sand filter into an oxidation pond for oxidation treatment: the oxidation pond is added with an activated carbon-supported manganese catalyst and is provided with an ozone reactor, the ozone reactor adopts micropore aeration, the adding concentration of ozone is 30mg/L, and the retention time of ozone is 2 hours.
(6) And (3) filtering the effluent after the oxidation treatment by using an ultrafiltration membrane system: the ultrafiltration membrane system adopts a flat plate type membrane prepared from polyvinylidene fluoride, and the filtration pore diameter of the membrane is less than 0.5 um; adding a sodium bisulfite solution into the filtered water of the ultrafiltration membrane system, adjusting the ORP of the wastewater to be +/-250 mv, wherein the operating membrane flux of the ultrafiltration membrane is 20-35L/(m)2×h)。
(7) Sending the effluent after being filtered by the ultrafiltration membrane system into a reverse osmosis membrane system for concentration and separation treatment, wherein the reverse osmosis membrane system adopts a flat membrane prepared from cellulose acetate; the desalination rate of the reverse osmosis membrane is more than 95%, the operating pressure is 0.35 Mpa-1.2 Mpa, and the membrane flux is 15-35L/(m)2X h), the recovery rate of the reverse osmosis membrane is 80-90%; and discharging the water body after the acrylonitrile wastewater treatment.
Through detection, the acrylonitrile wastewater treated by the embodiment 1 can reach the reuse standard specified in GB/T19923-2005 urban sewage recycling industrial water quality.
Example 2
See figure 1. A method for treating acrylonitrile wastewater comprises the following steps:
(1) the treated acrylonitrile wastewater is wastewater generated in the process of producing acrylonitrile by propylene ammoxidation (the same as in example 1).
Adjusting the pH value of the acrylonitrile wastewater to 8.5 by using sulfuric acid or sodium hydroxide, then sending the acrylonitrile wastewater into an adjusting tank provided with a paddle stirrer or a jet flow stirrer, carrying out homogenization, uniform mixing and treatment on the wastewater, and staying the wastewater in the adjusting tank for at least 4 hours.
(2) The wastewater after the homogeneous and uniform adjustment of the regulating reservoir is sent into an electric flocculation device for regulation treatment: the anode of the electric flocculation device is a plate-shaped material prepared from iron, the cathode of the electric flocculation device is a plate-shaped material prepared from iron, and the concentration range of iron ions generated by the electric flocculation device in acrylonitrile wastewater is 10-100 ppm. .
(3) Sending the wastewater subjected to the electric flocculation treatment into an air floatation tank for treatment: the air floatation tank adopts a pressurized dissolved air floatation device, and the dissolved air pressure is conventional 0.25 Mpa; adding 20ppm of cationic polyacrylamide with the molecular weight of 500 ten thousand; the wastewater after entering the flotation tank is divided into three parts (the rest is the same as in example 1).
(4) And (3) continuously treating the air-floated effluent by using an activated carbon filter, filtering untreated suspended substances remained in the air-floated effluent to remove part of organic matters, wherein the turbidity of the filtered effluent is less than 10 NTU.
(5) Sending the effluent treated by the activated carbon filter into an oxidation pond for oxidation treatment: the oxidation pond is added with a zeolite catalyst and is provided with an ozone reactor, the ozone reactor adopts micropore aeration, the adding concentration of ozone is 200mg/L, and the retention time of ozone is 0.5 h.
(6) And (3) filtering the effluent after the oxidation treatment by using an ultrafiltration membrane system: the ultrafiltration membrane system used a hollow fiber membrane made of polyvinylidene fluoride (otherwise as in example 1).
(7) Sending the effluent after being filtered by the ultrafiltration membrane system into a reverse osmosis membrane system for concentration and separation treatment, wherein the reverse osmosis membrane system adopts a roll-type membrane prepared from aromatic polyhydrazide (the rest is the same as the embodiment 1); and discharging the water body after the acrylonitrile wastewater treatment.
Through detection, the acrylonitrile wastewater treated in the example 2 can reach the reuse standard specified in GB/T19923-2005 quality of water for municipal wastewater recycling industry.
Example 3
See also fig. 1. A method for treating acrylonitrile wastewater comprises the following steps:
(1) the treated acrylonitrile wastewater is wastewater generated in the process of producing acrylonitrile by propylene ammoxidation (the same as in example 1).
Adjusting the pH value of the acrylonitrile wastewater to 7.5 by using sulfuric acid or sodium hydroxide, then sending the acrylonitrile wastewater into an adjusting tank provided with a paddle stirrer or a jet flow stirrer, carrying out homogenization, uniform mixing and treatment on the wastewater, and staying the wastewater in the adjusting tank for at least 4 hours.
(2) The wastewater after the homogeneous and uniform adjustment of the regulating reservoir is sent into an electric flocculation device for regulation treatment: the anode of the electric flocculation device is a plate-shaped material prepared from aluminum, the cathode of the electric flocculation device is a rod-shaped material prepared from carbon, and the concentration range of aluminum ions generated by the electric flocculation device in acrylonitrile wastewater is 10-100 ppm.
(3) Sending the wastewater subjected to the electric flocculation treatment into an air floatation tank for treatment: the air floatation tank adopts a pressurized dissolved air floatation device, and the dissolved air pressure is 0.25-0.35 Mpa of the conventional pressure; adding 12ppm of cationic polyacrylamide with the molecular weight of 1200 ten thousand; the wastewater after entering the flotation tank is divided into three parts (the rest is the same as in example 1).
(4) And (2) continuously treating the air-flotation effluent by adopting a self-cleaning filter with a self-cleaning function, wherein the self-cleaning filter can be used for setting timed automatic air and water back flushing, the back flushing period is 0.5-3 h, untreated suspended substances remained in the air-flotation effluent are filtered to remove part of organic matters, and the turbidity of the filtered effluent is less than 10 NTU.
(5) Sending the effluent treated by the filter into an oxidation pond for oxidation treatment: the oxidation pond is added with a catalyst of manganese or cobalt-loaded alumina oxide and is provided with an ozone reactor, the ozone reactor adopts micropore aeration, the adding concentration of ozone is 120mg/L, and the retention time of ozone is 1.2 h.
(6) And (3) filtering the effluent after the oxidation treatment by using an ultrafiltration membrane system: the ultrafiltration membrane system used a flat sheet membrane made of polyvinylidene fluoride (otherwise as in example 1).
(7) Sending the effluent after being filtered by the ultrafiltration membrane system into a reverse osmosis membrane system for concentration and separation treatment, wherein the reverse osmosis membrane systemA flat membrane prepared from aromatic polyamide; the desalination rate of the reverse osmosis membrane is more than 95%, the operating pressure is 0.35 Mpa-1.2 Mpa, and the membrane flux is 15-35L/(m)2X h), the recovery rate of the reverse osmosis membrane is 80-90%; and discharging the water body after the acrylonitrile wastewater treatment.
Through detection, the acrylonitrile wastewater treated by the embodiment 3 can reach the reuse standard specified in GB/T19923-2005 urban sewage recycling industrial water quality.
Application example 1
The acrylonitrile wastewater treatment method treats acrylonitrile wastewater discharged from acrylonitrile production by propylene ammoxidation in certain petrochemical enterprises, and the main pollutants and the concentration range in the wastewater are as follows: CODcr is 1490mg/L, TKN is 258mg/L, NH3-N is 145mg/L, TCN is 30mg/L, and pH is 6.6.
(1) And introducing the acrylonitrile wastewater into an adjusting tank provided with a jet flow stirrer, homogenizing, uniformly mixing and treating the wastewater, and staying the wastewater in the adjusting tank for 4 hours.
(2) The wastewater after the homogeneous and uniform adjustment of the regulating reservoir is sent into an electric flocculation device for regulation treatment: and opening the electric flocculation reaction device, and adjusting the electric flocculation device until the content of iron ions in the wastewater is 55 ppm.
(3) Sending the wastewater subjected to the electric flocculation treatment into an air floatation tank for treatment: the air floatation tank adopts a pressurized dissolved air floatation device, and the dissolved air pressure is conventional 0.28 Mpa; adding 8ppm cationic polyacrylamide with molecular weight of 1500 ten thousand into effluent water of the electric flocculation device.
(4) Adopting a sand filter to continuously treat the air flotation effluent: filtering the untreated suspended substances remained in the air-floated effluent to remove part of organic matters, setting the automatic cleaning period of the sand filter to be 2h, and setting the turbidity of the filtered effluent to be 10 NTU.
(5) Sending the effluent treated by the sand filter into an oxidation pond for oxidation treatment: the oxidation pond is added with heterogeneous activated carbon cobalt-loaded catalyst, and is provided with an ozone reactor, wherein the ozone reactor adopts micropore aeration, the adding concentration of ozone is 100mg/L, and the retention time of ozone is 0.5 h.
(6) And (3) filtering the effluent after the oxidation treatment by using an ultrafiltration membrane system: the ultrafiltration membrane system adopts a hollow fiber flat membrane prepared from polyvinylidene fluoride, and the filtration pore diameter of the membrane is less than 0.15 um; adding sodium bisulfite solution into the filtered water of the ultrafiltration membrane system, adjusting the ORP of the wastewater to 200mv, and adjusting the operating membrane flux of the ultrafiltration membrane to 20L/(m)2×h)。
(7) Sending the effluent after being filtered by the ultrafiltration membrane system into a reverse osmosis membrane system for concentration and separation treatment, wherein the reverse osmosis membrane system is a rolled reverse osmosis membrane prepared from cellulose acetate; the reverse osmosis membrane has a desalination rate of 95%, an operating pressure of 0.4Mpa, and a membrane flux of 20L/(m)2X h), the recovery rate of the reverse osmosis membrane is 85 percent; and discharging the water body after the acrylonitrile wastewater treatment.
Through detection, the acrylonitrile wastewater treated by the application example 1 can reach the reuse standard specified in GB/T19923-2005 urban sewage recycling industrial water quality: COD is 50mg/L, ammonia nitrogen is 8mg/L, turbidity is 1NTU, sulfate radical is 10 mg/L.

Claims (10)

1. A method for treating acrylonitrile wastewater, wherein the acrylonitrile wastewater is generated in the process of producing acrylonitrile by propylene ammoxidation, and the main pollutants and the concentration range in the wastewater are as follows: COD: 1200-3000 mg/L; TKN: 200-500 mg/L; NH 3-N: 100-250 mg/L; TCN: 30-100 mg/L; the method is characterized by comprising the following steps:
(1) adjusting the pH value of acrylonitrile production wastewater to 6.5-8.5 by using sulfuric acid or sodium hydroxide, then sending the acrylonitrile production wastewater into an adjusting tank provided with a paddle stirrer or a jet flow stirrer, carrying out homogenization, uniform mixing and treatment on the wastewater, and allowing the wastewater to stay in the adjusting tank for at least 4 hours;
(2) feeding the wastewater subjected to homogenizing and uniform quantity regulation in the regulating tank into an electric flocculation device for regulation treatment; the anode of the electric flocculation device is a rod-shaped or plate-shaped material prepared from aluminum or iron, and the cathode of the electric flocculation device is a rod-shaped or plate-shaped material prepared from aluminum, iron or carbon;
(3) sending the wastewater subjected to the electrocoagulation treatment into an air floatation tank for treatment, and adding 5-20 ppm of polyacrylamide; the wastewater after entering the air floatation tank is divided into three parts: separating a part of suspended matter solution from the bottom of the air floatation tank through a sludge discharge system; the two parts of suspended matters with lower density float to the surface of the air floatation tank and are separated by a sludge discharge system; the third part is air floatation effluent containing less suspended matters;
(4) adopting a filter to continuously treat the air flotation effluent: filtering the untreated suspended substances remained in the air-floated effluent to remove part of organic matters, wherein the turbidity of the filtered effluent is less than 10 NTU;
(5) feeding the effluent treated by the filter into an oxidation tank for oxidation treatment, wherein the oxidation tank is provided with an ozone reactor, the ozone reactor adopts micropore aeration, the adding concentration of ozone is 30-200 mg/L, and the retention time of ozone is 0.5-2 h;
(6) filtering the effluent after the oxidation treatment by using an ultrafiltration membrane system, adding a sodium bisulfite solution into the filtered water of the ultrafiltration membrane system, and adjusting the ORP of the wastewater to be within +/-250 mv;
(7) and (4) sending the effluent after the filtration treatment of the ultrafiltration membrane system into a reverse osmosis membrane system for concentration and separation treatment, and discharging the water body after the acrylonitrile wastewater treatment.
2. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein the concentration of iron ions or aluminum ions generated in the wastewater by the electric flocculation device is in the range of 10-100 ppm.
3. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein the polyacrylamide in step (3) is cationic and has a molecular weight of 500 to 2000 ten thousand.
4. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein the air flotation device adopted in the air flotation tank in the step (3) is a pressurized dissolved air flotation device, and the dissolved air pressure is 0.25-0.35 MPa.
5. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein the filter in step (4) is a sand filter or an activated carbon filter.
6. The method for treating acrylonitrile wastewater as claimed in claim 5, wherein the filter can be automatically back-flushed with air and water at regular time, and the back-flushing period is 0.5-3 h.
7. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein a catalyst comprising activated carbon, zeolite, manganese oxide or cobalt oxide is added into the oxidation pond in step (5).
8. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein the ultrafiltration membrane adopted by the ultrafiltration membrane system in step (6) is a polyvinylidene fluoride membrane, the membrane is in the form of a flat plate or hollow fiber, the filtration pore diameter of the membrane is less than 0.5um, and the operating membrane flux of the ultrafiltration membrane is 20-35L/(m) m2×h)。
9. The method for treating acrylonitrile wastewater as claimed in claim 1, wherein the reverse osmosis membrane used in the reverse osmosis membrane system of step (7) is a cellulose acetate membrane, an aromatic polyhydrazide membrane or an aromatic polyamide membrane, and the membrane is in a roll or flat plate structure.
10. The method for treating acrylonitrile wastewater according to claim 1, wherein the salt rejection of the reverse osmosis membrane is more than 95%, the operating pressure is 0.35MPa to 1.2MPa, and the membrane flux is 15 to 35L/(m)2X h), the recovery rate of the reverse osmosis membrane is 80-90%.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101353215A (en) * 2008-08-29 2009-01-28 浙江大学 Dyeing waste water comprehensive processing and reclaiming process
CN102115286A (en) * 2009-12-30 2011-07-06 凯膜特种分离技术(上海)有限公司 Treatment method for recycling coking wastewater and assembled treatment system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101353215A (en) * 2008-08-29 2009-01-28 浙江大学 Dyeing waste water comprehensive processing and reclaiming process
CN102115286A (en) * 2009-12-30 2011-07-06 凯膜特种分离技术(上海)有限公司 Treatment method for recycling coking wastewater and assembled treatment system

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