CN112794500B - Coking wastewater strong brine near-zero emission treatment system and treatment method thereof - Google Patents

Coking wastewater strong brine near-zero emission treatment system and treatment method thereof Download PDF

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CN112794500B
CN112794500B CN202011593692.7A CN202011593692A CN112794500B CN 112794500 B CN112794500 B CN 112794500B CN 202011593692 A CN202011593692 A CN 202011593692A CN 112794500 B CN112794500 B CN 112794500B
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reverse osmosis
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CN112794500A (en
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张传兵
张丁丁
赵曙光
李鑫
陈珊珊
侯亚平
徐漫漫
边卫云
张高洁
廖庆花
万家虎
李瑞明
陈俊文
朱胜利
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Beijing Branch Of Huaxia Bishui Environmental Protection Technology Co ltd
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Abstract

A coking wastewater strong brine near-zero emission treatment system and a treatment method thereof are disclosed, wherein the treatment system comprises a regulating reservoir, a first-stage efficient sedimentation tank, a second-stage efficient sedimentation tank, a first-stage multi-medium filter, an ozone oxidation contact tank, a second-stage multi-medium filter, an ultrafiltration device, a weak acid cation exchange unit, a nanofiltration unit, a concentrated water nanofiltration unit, a reverse osmosis unit and a concentrated water reverse osmosis unit which are sequentially connected; the wastewater passes through the nanofiltration unit, the produced water enters the reverse osmosis unit, the concentrated water enters the concentrated water nanofiltration unit, the produced water of the nanofiltration unit and the concentrated water nanofiltration unit enters the reverse osmosis unit, the concentrated water produced by the reverse osmosis unit enters the concentrated water reverse osmosis unit, and the produced water of the reverse osmosis unit and the concentrated water reverse osmosis unit is combined for recycling; FeCl is added before the effluent of the weak acid cation exchange unit is subjected to nanofiltration3And SnCl4Co-modified molecular sieves. The treatment system provided by the invention is used for treating the coking wastewater strong brine, the water yield reaches more than 80%, and the membrane system is stable after long-time operation.

Description

Coking wastewater strong brine near-zero emission treatment system and treatment method thereof
Technical Field
The invention relates to the field of wastewater treatment, in particular to a coking wastewater strong brine near-zero emission treatment system and a treatment method thereof.
Background
The coking industry belongs to the industries with high energy consumption, high pollution and resource, and a large amount of wastewater is generated in the coking and gas purification processes, contains various pollutants such as volatile phenol, cyanide, ammonia nitrogen, sulfide and the like, and has high treatment difficulty. At present, the coking wastewater is recycled after being treated by strong brine, and is mainly considered to be absorbed in blast furnace granulated slag. Along with the continuous increase of production load, the contradiction between the generation amount and the consumption amount of the coking wastewater strong brine is gradually exposed, and the coking wastewater strong brine consumed by the blast furnace slag only accounts for one tenth of the generation amount of the coking wastewater strong brine. The coking wastewater strong brine can not be recycled by about 4000 tons of coking wastewater every day, the problems of slag bubbles and the like of the blast furnace slag in the process of dissolving the coking wastewater strong brine are seriously restricted from using the coking wastewater strong brine, and the problem of going out of the coking wastewater strong brine is urgently solved under the condition that the environmental protection requirement is increasingly strict. According to the existing 'emission standard of pollutants for coking chemical industry' (GB16171-2012), the existing enterprises execute the limit of the water pollutant emission concentration of newly built enterprises, and in order to meet the requirement of the coking wastewater and effluent quality composite reclaimed water quality, on one hand, the load of a membrane system is large, the frequency of cleaning or replacing membranes is increased, and the cost is increased; on the other hand, the high standard requirement on the quality of the discharged water also brings low water yield of the reverse osmosis unit.
However, the prior coking wastewater strong brine near-zero emission combined process has the following problems:
(1) at present, the existing coking wastewater strong brine near-zero discharge process mostly adopts a single-stage efficient sedimentation tank, namely hardness and fluoride ions are removed under the same pH condition, and the fluoride ion removal effect is poor, so that the risk of calcium fluoride scaling of a membrane system is large, and cleaning and recovery after scaling are difficult;
(2) the coking wastewater strong brine has high organic matter concentration, complex COD component and great removal difficulty, so that the original elements of the subsequent ultrafiltration, nanofiltration and reverse osmosis membrane are easily polluted by organic matters and microorganisms;
(3) the hardness of the wastewater is high, and the existing coking wastewater strong brine near-zero discharge process lacks a deep softening process link, so that the subsequent reverse osmosis recovery rate is limited, the scaling risk of a membrane system is increased, and the membrane system is cleaned frequently;
(4) the water yield of the present coking wastewater in a Reverse Osmosis (RO) unit is about 70 percent, and the water yield is lower.
CN110734178A discloses a membrane concentration zero-discharge treatment system and method for coking wastewater, which adopts pretreatment, membrane salt separation concentration treatment, electrodialysis concentration, evaporation and crystallization. The method has good treatment effect on the coking wastewater and good quality of effluent, but also needs electrodialysis treatment with higher cost and large energy consumption, and the electrodialysis can generate new pollution.
CN101786767A discloses a coking wastewater advanced treatment process, which adopts MBR, ozone contact oxidation treatment, activated carbon adsorption treatment and reverse osmosis treatment. The method does not aim at removing fluoride ions in the wastewater, so that the scaling phenomenon of the reverse osmosis membrane is serious, the membrane needs to be cleaned or replaced frequently, the cost is increased, and the operation of the process is improved. CN111039477A discloses a coking wastewater treatment process, which also uses an electrodialysis technology, has no advantages in energy conservation and environmental protection, and the water yield is limited to the range of 70%.
CN105502782A discloses a coking wastewater treatment process, in order to eliminate the pressure of fluorinion on a subsequent membrane system, firstly, wastewater defluorination chemical treatment is carried out, the common methods of calcium chloride and lime are adopted to reduce the concentration of fluorinion to be below 0.5mg/L, but the particle size of the generated calcium fluoride is small and difficult to filter, and macromolecule such as polyacrylamide flocculant is usually added to form floccule for precipitation. The addition of an acrylamide flocculant is reported by documents to aggravate the pollution of a subsequent membrane system, and the traditional coagulant cannot effectively remove fluoride formed in the treatment process; on the other hand, the demand for lime and calcium salt is large, the cost of the medicament is increased, and the added calcium salt and the like can increase the hardness of water and have adverse effect on the subsequent water treatment.
CN108585157A discloses a method for removing fluoride in coal conversion wastewater, which is to add crystalline aluminum chloride into the wastewater and remove fluoride ions by a coagulation sedimentation method, but the addition amount of the crystalline aluminum chloride is too large and reaches 0.3-0.5g/L, the dosage is too high, and the introduction of too much aluminum ions also increases the treatment burden and is not convenient for industrial wastewater treatment.
Therefore, in the present coking wastewater strong brine treatment process, how to alleviate the influence of fluoride ion, hardness, basicity, organic pollutant to follow-up membrane system, place membrane system structure, block up, improve the water yield of wastewater treatment system, is the problem that needs improvement to solve at present.
Disclosure of Invention
The embodiment of the invention provides a coking wastewater strong brine near-zero emission treatment system and a treatment method thereof, aiming at coking wastewater strong brine with high fluoride ions, high hardness and high alkalinity, a two-stage efficient sedimentation tank process, a two-stage multi-medium filter process and a combined process of nanofiltration and reverse osmosis matched with concentrated water nanofiltration and concentrated water reverse osmosis are respectively adopted, so that an excellent treatment effect is achieved, the water production rate is greatly improved, the discharge amount of the coking wastewater strong brine is greatly reduced, meanwhile, the pressure on a membrane system is small, and the membrane system can be used for a long time without replacement or cleaning.
The purpose of the invention is realized by the following technical scheme:
a coking wastewater strong brine near-zero emission treatment system comprises a regulating reservoir, a first-stage high-efficiency sedimentation tank, a second-stage high-efficiency sedimentation tank, a first-stage multi-medium filter, an ozone oxidation contact tank, a second-stage multi-medium filter, an ultrafiltration device, a weakly acidic cation exchange unit, a nanofiltration unit, a concentrated water nanofiltration unit, a reverse osmosis unit and a concentrated water reverse osmosis unit which are connected in sequence; the wastewater passes through the nanofiltration unit, the produced water enters the reverse osmosis unit, the concentrated water enters the concentrated water nanofiltration unit, the produced water of the nanofiltration unit and the concentrated water nanofiltration unit enters the reverse osmosis unit, the concentrated water produced by the reverse osmosis unit enters the concentrated water reverse osmosis unit, and the produced water of the reverse osmosis unit and the concentrated water reverse osmosis unit is combined for recycling; FeCl is added before the effluent of the weak acid cation exchange unit is subjected to nanofiltration3And SnCl4Co-modified molecular sieves.
The input amount of the modified molecular sieve is 0.05-0.1kg of the modified molecular sieve per ton of wastewater. After the molecular sieve is added, the mixture is maintained for 1-2 hours under the stirring condition, a small amount of residual fluorine ions in the wastewater can be further removed, the scaling or pollution of a membrane system is avoided, and the times of cleaning or replacing the membrane are reduced. Has great industrial advantages in the treatment of the coking wastewater and strong brine.
Preferably, the FeCl3And SnCl4The co-modified molecular sieve is prepared by a preparation method comprising the following steps: putting a molecular sieve into a quaternary ammonium salt surfactant solution, soaking at 50-60 ℃ under an ultrasonic condition, drying, and then putting into FeCl-containing solution3And SnCl4Soaking in the solution, taking out, washing and drying to obtain the product.
The quaternary ammonium salt surfactant is in a long-chain alkyl ammonium salt type or an alkyl benzyl ammonium type; for example, the long chain alkyl group has 12 to 20 carbon atoms, such as tetradecyltrimethylammonium bromide, hexadecyltriethylammonium chloride; the alkyl benzyl ammonium type is selected from dodecyl dimethyl benzyl ammonium chloride and triethyl benzyl ammonium chloride.
The molecular sieve, quaternary ammonium salt surfactant solution and the catalyst containing FeCl3And SnCl4The mass ratio of the solution (1): 5-10: 5-10. Wherein the concentration of quaternary ammonium salt surfactant is 50-100mM, FeCl3In a concentration of 0.5-1M, SnCl4The concentration of (A) is 0.01-0.0.02M. Soaking the molecular sieve in quaternary ammonium salt surfactant solution for 0.5-2h, and adding FeCl3And SnCl4The soaking time in the solution is 0.5-2 h.
The silicon-aluminum ratio of the molecular sieve is 2.5-3, such as 10X molecular sieve and 13X molecular sieve.
The first-level efficient sedimentation tank and the second-level efficient sedimentation tank are matched with a reaction tank stirrer, a flocculation area central cylinder, a flocculation area stirrer, a sedimentation area mud scraper, an inclined tube sedimentation device, a water collecting channel and the like.
Before the treatment of a membrane system (nanofiltration and reverse osmosis), the modified molecular sieve is added into the wastewater, so that the fluorine ions in the water can be adsorbed. The inventors have also unexpectedly found that in the modification of molecular sieves, in addition to the conventional iron salt modification, the present invention also adds an amount of SnCl4And the fluorine ions in water can be more effectively adsorbed by matching with a molecular sieve with a specific silicon-aluminum ratio. The pressure of scaling and pollution of a subsequent membrane system is reduced, the use instruction of the membrane is prolonged, and the times of cleaning and replacing the membrane are reduced. Greatly improving the production efficiency and reducing the cost.
Further, a defluorination agent, a coagulant and a coagulant aid are added into the first-stage efficient sedimentation tank, wherein the defluorination agent is CaCl2And Ca (OH)2And LiCl at a mass ratio of 3-5: 1-2:1-2, the coagulant is at least one of iron salt selected from ferric sulfate and ferric chloride, aluminum salt selected from aluminum chloride and aluminum sulfate, and polymer thereof selected from polymeric ferric sulfate, polymeric ferric chloride, polymeric aluminum chloride and polymeric aluminum sulfate; the coagulant aid is polyacrylamide. The mass ratio of the defluorination agent, the coagulant and the coagulant aid is 2-4:3-5: 1-2.
Further, the agent added into the secondary high-efficiency sedimentation tank is a mixture of an agent for removing total hardness and a coagulant according to the mass ratio of 1-2:1, and the agent for removing total hardness is Ca (OH)2,Na2CO3And NaOH according to the mass ratio of 5-7: 1-2: 0.2-0.5, wherein the coagulant is polyaluminium chloride and polyaluminium polyphosphate chloride according to the mass ratio of 1-2: 1-2.
Further, in the ozone contact oxidation tank, the organic matter is directly degraded into the final product CO by adopting the decomposition reaction of the synergistic oxidation action of ozone and hydrogen peroxide2And H2And O, achieving the effect of removing COD. The dosage of the ozone is 200-400g per ton of wastewater, and the dosage of the hydrogen peroxide is 50-100g per ton of wastewater.
Furthermore, the primary multi-media filter and the secondary multi-media filter are made of carbon steel lining rubber, anthracite filter material d10=1.2-1.5mm, quartz sand filter material d10=0.5-0.8mm, and cobblestone d10=2.0-4.0 mm; anthracite filter material d10=0.6-1.0mm, quartz sand filter material d10=0.2-0.4mm, and cobblestone d10=1.0-1.5mm in the second-stage multi-medium filter.
Further, the weak acid cation exchange unit adopts weak acid cation exchange resin with the model of D151, XAD-7, DK110 or 724. The weakly acidic cation exchange resin can make various high-valence metal ions (Fe) in water3+、Ca2+、Mg2 +Etc.) are adsorbed onto the ion exchange resin to soften the water to prevent fouling of subsequent membranes.
The membrane of the nanofiltration unit is polyamide, the nanofiltration unit can further remove macromolecular organic pollutants, and meanwhile, the part which cannot be removed is intercepted to the concentrated water side through the nanofiltration device, so that the water inlet quality of the subsequent reverse osmosis membrane device is obviously improved, and the scaling risk of a membrane system is reduced. The concentrated water of the nanofiltration unit passes through the concentrated water nanofiltration unit, the water produced by the concentrated water nanofiltration unit and the water produced by the nanofiltration unit are combined under high pressure and enter the reverse osmosis unit together.
And further, the reverse osmosis unit further concentrates and desalts the produced water, so that the monovalent salt wastewater enters the concentrated water reverse osmosis unit after being concentrated and reduced, and is concentrated again, and the produced water of the concentrated water reverse osmosis unit and the produced water of the reverse osmosis unit are combined for recycling.
Through the modes of nanofiltration-concentrated water nanofiltration and reverse osmosis and concentrated water reverse osmosis, the concentration multiple of the wastewater is more than 8 times, the water yield of the concentrated brine treatment system can reach more than 80%, and compared with the coking wastewater concentrated brine in the prior art, the concentrated brine treatment system only has the water yield of 70%, and has the advantage of saving water resources. However, when the water yield is increased, a great load pressure is applied to the membrane system, especially the fluorine ion concentration is increased by several times, the concentrated water is easy to combine with calcium and magnesium ions remained in the waste water to form insoluble precipitate, and after the operation time of the membrane system is slightly prolonged, the phenomena of scaling, pollution and the like of the membrane are generated by dissolution. Therefore, the modified molecular sieve is added before nanofiltration, and the fluorine ions participating in the wastewater are fully further treated, wherein quaternary ammonium salt is used for treating the molecular sieve, and the quaternary ammonium salt surfactant not only changes the internal property of the molecular sieve, but also has a certain bacteriostatic action and also has a function of inhibiting the pollution of the membrane caused by the bacterial growth in later reverse osmosis.
The invention also provides a method for treating wastewater by using the coking wastewater strong brine near-zero emission treatment system, which comprises the following steps:
(1) wastewater firstly converges into a regulating tank for regulating water quality, water quantity and water temperature;
(2) the effluent of the regulating reservoir enters a first-stage high-efficiency sedimentation tank, and a fluorine removal agent, a coagulant and a coagulant aid are added;
(3) the supernatant of the first-stage high-efficiency sedimentation tank flows into a second-stage high-efficiency sedimentation tank, and the total hard medicament and coagulant are added and removed,
(4) pumping the supernatant of the secondary efficient sedimentation tank to a primary multi-media filter; the filtered produced water flows into an ozone contact oxidation pond, and the produced water is lifted to a second-stage multi-medium filter through a pump;
(5) the water produced by the secondary multi-medium filter enters an ultrafiltration unit;
(6) the effluent of the ultrafiltration unit flows into a weakly acidic cation exchange unit, is treated by a modified molecular sieve in an intermediate tank and is lifted to a nanofiltration unit by a pump;
(7) the concentrated water of the nanofiltration unit flows into a concentrated water nanofiltration unit for secondary nanofiltration, and the produced water of the nanofiltration unit and the produced water of the concentrated water nanofiltration unit flow into a reverse osmosis unit;
(8) the concentrated water generated by the reverse osmosis unit flows into the concentrated water reverse osmosis unit, and the produced water of the reverse osmosis unit and the concentrated water reverse osmosis unit is combined for recycling.
The modified molecular sieve is FeCl3And SnCl4Co-modified molecular sieves. The input amount of the modified molecular sieve is 0.05-0.1kg of the modified molecular sieve per ton of wastewater. After the molecular sieve is added, the mixture is maintained for 1-2 hours under the stirring condition, a small amount of residual fluorine ions in the wastewater can be further removed, the scaling or pollution of a membrane system is avoided, and the times of cleaning or replacing the membrane are reduced.
Preferably, the pH value of the first-stage efficient sedimentation tank in the step (2) is 9-10, the mass ratio of the fluorine removing agent, the coagulant and the coagulant aid is 2-4:3-5:1-2, and the total dosage of the added agents is 1-3kg per ton of wastewater.
Preferably, the pH value of the secondary efficient sedimentation tank in the step (3) is 11-12, the mass ratio of the added agents for removing the total hardness to the coagulant is 1-2:1-2, and the total amount of the added agents is 0.5-2kg per ton of wastewater.
Preferably, the operating pressure of the ultrafiltration unit in step (5) is 0.3-0.6 MPa.
Preferably, the operating pressure of the nanofiltration unit in the step (7) is 0.6-0.8MPa, and the operating pressure of the nanofiltration of the concentrated water is 5-6 MPa.
Preferably, the reverse osmosis unit concentration multiple in the step (8) is 4-6 times, the concentrated water reverse osmosis unit concentration multiple is 1.5-2 times, and the final total wastewater concentration multiple is 8-10 times.
In the wastewater treatment method, wastewater firstly converges into the regulating tank to regulate the water quality, the water quantity and the water temperature; then the sewage enters a first-stage efficient sedimentation tank, the functions of coagulation, flocculation, sedimentation and sludge concentration are integrated in the first-stage efficient sedimentation tank, and pollutants such as colloid, suspended matters, fluoride and the like are removed by adding agents such as a defluorinating agent, a coagulant aid and the like; the supernatant fluid flows into a secondary high-efficiency sedimentation tank and is added with Ca (OH)2、Na2CO3And NaOH to remove total hardness; the supernatant is pumped to a multi-media filter 1, and the turbidity and suspended matters of the inlet water are reduced by filtration; the filtered produced water flows intoThe ozone contacts with the oxidation tank, and organic matter is directly degraded into a final product CO through the decomposition reaction of the synergistic oxidation of ozone and hydrogen peroxide2And H2O, so as to achieve the effect of removing COD; the produced water after the ozone contact oxidation reaction is lifted to a multi-media filter 2 by a pump, and impurities and suspended matters in the produced water are filtered; the water produced by the secondary multi-medium filter enters an ultrafiltration system to remove colloids, microorganisms, bacteria and the like in the wastewater; the water produced by ultrafiltration flows into a weak acid cation bed, and weak acid cation exchange resin is filled in the bed; can make various ions (Fe) in water3+、Ca2+、Mg2+Etc.) are adsorbed on the ion exchange resin to soften the water; the softened water is put into a modified molecular sieve to further adsorb residual fluorine ions in the water, and the modified molecular sieve has a certain bacteriostatic function, after the modified molecular sieve is treated, the wastewater is lifted to a nanofiltration device through a pump, the nanofiltration device can further remove macromolecular organic pollutants, and meanwhile, the part which cannot be removed is intercepted to a concentrated water side through the nanofiltration device, so that the water quality of the water fed by a subsequent reverse osmosis membrane device is obviously improved, and the scaling risk of a membrane system is reduced; concentrated water enters a concentrated water nanofiltration device, so that the concentrated water amount of the nanofiltration device can be further reduced, the reuse water amount is increased, the produced water is delivered to the reverse osmosis device, and the concentrated water is delivered to a third party for treatment outside a concentrated water tank; the nanofiltration produced water is delivered to a reverse osmosis device and is mainly used for further concentration and desalination, the produced water is delivered to a reuse water point outside a water production tank, and the monovalent salt wastewater enters into the concentrated water for reverse osmosis after concentration and reduction; the concentrated water reverse osmosis device is mainly used for further concentrating and desalting reverse osmosis concentrated water, so that the waste water is concentrated and reduced and then is sent for utilization.
The process adopts a two-stage high-efficiency sedimentation tank, the pH is adjusted to 9-10 in one stage, and calcium fluoride sediment is generated by adding a defluorination agent, a coagulant and a coagulant aid, so that fluoride ions are removed; the reaction tank of the second-level efficient sedimentation tank is added with Ca (OH)2、Na2CO3NaOH is added to adjust the pH value to 11, and calcium and magnesium precipitates are generated under the action of a coagulant and a coagulant aid, so that the hardness of the wastewater is removed; matched with a reaction tank stirrer, a flocculation area central cylinder, a flocculation area stirrer, a sedimentation area mud scraper, an inclined tube sedimentation device and a collection deviceCanals, and the like.
The process adopts the technology of 'ozone contact oxidation and nanofiltration', and the ozone and hydrogen peroxide are used for the synergistic oxidation decomposition reaction, so that the organic matter is directly degraded into the final product CO2And H2O, so as to achieve the effect of removing COD; meanwhile, the part which cannot be removed is intercepted to the concentrated water side through nanofiltration; by the pretreatment, the quality of inlet water of the membrane system can be obviously improved, and the scaling risk of the membrane system is reduced; ozone contact oxidation is matched with an ozone generator system and a hydrogen peroxide adding system; the nanofiltration device adopts a rolled nanofiltration membrane, and the system comprises a water supply pump, a dosing pump, a flushing pump, a chemical washing pump, a water inlet tank, a water production tank, a concentrated water tank, a valve group and an instrument group.
The process adopts the technology of ultrafiltration, weak acid cation bed, nanofiltration and reverse osmosis, the hardness of inlet water of the membrane unit is reduced to the minimum through the softening action of weak acid cation exchange resin of the weak acid cation bed, macromolecular organic pollutants can be further removed through nanofiltration, the risks of calcium and magnesium scaling, calcium fluoride scaling, biological pollution and organic pollutant blockage of a membrane system can be obviously reduced, the operation stability of the system is improved, and the water yield of the system is increased; the ultrafiltration system comprises an ultrafiltration water supply pump, a backwashing water pump, a dosing pump, a membrane frame, an ultrafiltration membrane, a water inlet tank, a water production tank, a chemical washing water tank, a valve group and an instrument group; the weak acid cation bed adopts macroporous weak acid cation exchange resin, and is matched with a flushing system and a regeneration system, wherein the system comprises a water supply pump, a regeneration water pump, a dosing pump, a water inlet tank, a water production tank, a valve group and an instrument group; the nanofiltration device adopts a rolled nanofiltration membrane and comprises a water supply pump, a dosing pump, a flushing pump, a chemical washing pump, a water inlet tank, a water production tank, a concentrated water tank, a valve group and an instrument group; the reverse osmosis device adopts a roll type reverse osmosis membrane and comprises a water supply pump, a dosing pump, a flushing pump, a chemical washing pump, a water inlet tank, a water production tank, a concentrated water tank, a valve group and an instrument group.
Through the combined process, the coking wastewater strong brine can be concentrated by more than 8 times, the water yield can be improved by more than 80%, and the discharge amount of the coking wastewater strong brine is greatly reduced. And through the treatment of the modified molecular sieve, the membrane system can not generate the phenomena of scaling, pollution and the like after long-term operation and can stably operate for a long time.
Compared with the prior art, the invention has the beneficial effects that:
the invention has high automation degree and can stably run. The technology of a two-stage high-efficiency sedimentation tank is adopted, so that hardness, fluorine ions, silicon dioxide and most suspended matters in the sewage can be effectively removed. By adopting the technology of ozone contact oxidation and nanofiltration interception, enough COD can be effectively removed, and meanwhile, the part which cannot be removed is intercepted to the concentrated water side through nanofiltration; through the pretreatment, the quality of inlet water of the membrane system can be obviously improved, and the scaling risk of the membrane system is reduced. The method adopts the technology of ultrafiltration, weak acid cation bed resin softening, nanofiltration and reverse osmosis, reduces the hardness of inlet water of the membrane unit through resin softening, further adsorbs fluoride ions through adding a modified molecular sieve, has partial antibacterial action, can obviously reduce the risk of calcium and magnesium scaling, calcium fluoride scaling, biological pollution and organic matter pollution blockage of a membrane system, improves the running stability of the system and increases the water yield of the system.
Drawings
FIG. 1 is a flow chart of the coking wastewater concentrated brine near zero discharge combined process of the invention.
Detailed Description
The invention is further illustrated by the following examples.
Preparation examplePreparation of modified molecular sieves
Preparation example 1
Adding 5kg of molecular sieve 10X into 25kg of 50mM dodecyl dimethyl benzyl ammonium chloride, soaking for 1h at 50-60 ℃ under the ultrasonic condition, taking out, drying, adding 25kg of FeCl containing 0.6M3,0.02M SnCl4Soaking the water solution in the solvent for 1h under stirring, taking out, washing with water to neutrality, and oven drying.
Preparation example 2
5kg of molecular sieve 10X was charged into 25kg of a catalyst containing 0.6M FeCl3,0.02M SnCl4Soaking the water solution in the solvent for 1h under stirring, taking out, washing with water to neutrality, and oven drying. Namely, the pretreatment step of the quaternary ammonium salt surfactant in preparation example 1 was omitted.
Preparation example 3
Adding 5kg of molecular sieve 10X into 25kg of 50mM dodecyl dimethyl benzyl ammonium chloride, soaking for 1h at 50-60 ℃ under the ultrasonic condition, taking out, drying, adding 25kg of FeCl containing 0.6M3Soaking the water solution in the solvent for 1h under stirring, taking out, washing with water to neutrality, and oven drying. I.e. aqueous solution not containing SnCl4
Example 1
160m of strong brine from coking wastewater of a certain company3The water quality of inlet water is as follows: CODcr =250mg/L, F-= 210mg/L, TDS =11500 mg/L, hardness = 550mg/L, alkalinity = 500 mg/L.
The combined process of the primary efficient sedimentation tank, the secondary efficient sedimentation tank, the multi-media filter 1, the ozone contact oxidation, the multi-media filter 2, the ultrafiltration device, the weak acid cation bed, the modified molecular sieve treatment, the nanofiltration device, the concentrated water nanofiltration device, the reverse osmosis device and the concentrated water reverse osmosis device is adopted as shown in figure 1.
Step (1), adjusting the tank to a volume of 1400m38.8h of residence time, steel concrete, regulating reservoir lift pump Q =176m3H, H =15m, N =11 KW; the waste water is firstly converged into a regulating tank for regulating the water quality and the water quantity.
Step (2), a first-stage efficient sedimentation tank with the total volume of 350m3Steel concrete, surface load 10 m/h; sludge reflux pump Q =110m3H, H =30m, N =3 KW; sludge discharge pump Q =10m3H, H =30m, N =3 KW; 2kg of medicament is added into each ton of wastewater: the agent is a defluorination agent, and the coagulant aid are mixed according to the mass ratio of 2:3:1, wherein the defluorination agent is CaCl2And Ca (OH)2And LiCl at a mass ratio of 3-5: 1-2:1-2, the coagulant is a mixture of polyaluminium chloride and polyferric chloride according to the mass ratio of 1:1, and the coagulant aid is polyacrylamide with the molecular weight of 800 ten thousand. After flocculation and precipitation in a first-stage efficient sedimentation tank, F-It was reduced to 32 mg/l.
Step (3), the supernatant of the first-stage efficient sedimentation tank enters a second-stage efficient sedimentation tank, and the total volume is 252m3Steel concrete, surface load 9.5 m/h. Adding 1kg of medicament into each ton of wastewater, wherein the medicament is the medicament for removing total hardness and the coagulant according to the massAnd 2:1, the total hardness-removing agent is Ca (OH)2,Na2CO3And NaOH in a mass ratio of 3: 1: 0.2, and the coagulant is compounded by polyaluminium chloride and polyaluminium polyphosphate in a mass ratio of 1: 1. After flocculation and precipitation in a secondary efficient sedimentation tank, the pH value of effluent is adjusted to be neutral by sulfuric acid, the hardness of the effluent is reduced to 81mg/l, and the alkalinity is reduced to 65 mg/l.
Step (4), enabling the supernatant of the secondary efficient sedimentation tank to flow to a multi-media filter 1, lining rubber with carbon steel, wherein D =2.8m, and the flow speed is 8.2 m/h; anthracite filter material d10=1.2 mm; the quartz sand filter material d10=0.6mm and the cobblestone d10=2.5 mm; water supply pump Q =176m3H, H =15m, N =11 KW; backwash water pump Q =266m3H, H =25m, N =30 KW; roots blower Q =5.54m3Min, H =6m, N =11 KW; the multi-medium filter 1 filters the produced water of the secondary efficient sedimentation tank, and reduces the influence of effluent turbidity and SS on subsequent ozone contact oxidation; the multi-medium filter 1 enters an ozone contact oxidation pond, and the gas production rate is 80 kg/h; circulating pump Q =280m3H, H =18m, N =22 KW; 200g of ozone and 50g of hydrogen peroxide are added into each ton of wastewater, and the ozone and the hydrogen peroxide are subjected to synergistic oxidation decomposition reaction to directly degrade organic matters into a final product CO2And H2O, the effect of removing COD is achieved, and the COD is stabilized below 120 mg/l. The effluent of the ozone oxidation contact tank enters a secondary multi-media filter, carbon steel is lined with rubber, D =2.8m, and the flow velocity is 8 m/h; anthracite filter material d10=0.8mm, quartz sand filter material d10=0.4mm, cobblestone d10=1.5 mm; water supply pump Q =200m3H, H =35m, N =30 KW; backwash water pump Q =135m3H =25m, N =18.5 KW; the second-stage multi-media filter filters water produced by ozone contact oxidation, and intercepts COD, SS and other substances degraded by the reaction of ozone and hydrogen peroxide.
Step (5), the effluent of the secondary multi-medium filter enters an ultrafiltration unit, a Dow ultrafiltration membrane SFP2880 is adopted, and the total treatment capacity of the ultrafiltration unit is 180m3The flux is 30LMH, and the operating pressure is 0.3 MPa; and (3) removing colloids, microorganisms, bacteria and the like in the wastewater by ultrafiltration, and reducing the pollution and pollution blockage of a subsequent weak acid cation bed, nanofiltration and reverse osmosis so as to prolong the service life of the subsequent membrane.
Step (6) ultraThe water produced by the filtering unit flows into a weak acid cation exchange unit, the weak acid cation exchange resin is D151, and the designed flow rate is 82 m3The designed flow rate is 17m/h, the total exchange capacity is 10.8mmol/g, the volume exchange capacity is 4.3 mmol/g, and the hardness of the effluent is reduced to 32mg/L by passing through a weak acid cation exchange unit. And (3) feeding the effluent of the weak acid cation exchange unit into an intermediate tank, adding 0.05kg of the modified molecular sieve prepared in the preparation example 1 into each ton of wastewater, treating for 1 hour under the stirring condition, and lifting to a nanofiltration unit through a pump.
Step (7), a nanofiltration unit, each set of 84+42+24 three sections are combined, the flux is 16LMH, and the membrane area is 34m2The membrane material is polyamide, the recovery rate is 84 percent, the model is NF90-2540, and the nanofiltration water supply pump Q =33m3H, outlet pressure 0.8 MPa; each set of 35 membranes of the concentrated water nanofiltration unit has the flux of 12LMH and the membrane area of 34m2The membrane is made of polyamide, the recovery rate is 53 percent, the model is FORTILIFE XC NHP, and the high-pressure pump Q =26m3H, the outlet pressure is 6 MPa; the concentrated water generated by the nanofiltration unit continuously passes through the concentrated water nanofiltration unit to further reduce the concentrated water amount of the nanofiltration device and increase the reuse water amount.
Step (8), combining the produced water of the nanofiltration unit and the produced water of the concentrated water nanofiltration unit, and then feeding the combined water into a reverse osmosis unit, wherein each set of the reverse osmosis unit comprises 63+35 membranes, the flux is 16LMH, and the membrane area is 37m2The membrane material is polyamide, the recovery rate is 75 percent, and the model is FORTILIFE CR 100; 150 m of inlet water3H, water production 112.5 m3H, concentrated water 37.5m3H, concentrating the wastewater by 4 times; the reverse osmosis device is mainly used for further concentrating and desalting nanofiltration produced water and concentrated water, so that monovalent salt wastewater is concentrated and reduced and then enters a concentrated water reverse osmosis unit, each set of 42 membranes has a flux of 14LMH and a membrane area of 34.4m2Polyamide, recovery 52%, model FORTILIFE XC 70; concentrated water reverse osmosis water supply pump Q =37m3H =30m, N =4.5 kw; concentrated water reverse osmosis high-pressure pump Q =42m3H, 37.5m of inlet water3H, 19.5 m of produced water3H, 18m of concentrated water3H, concentrating the wastewater by 2 times again; the concentrated water reverse osmosis device is mainly used for further concentrating and desalting reverse osmosis concentrated water, so that the waste water is concentrated and reduced and then is sent for utilization.
The above steps can realize full-automatic operationAnd finally, the reverse osmosis concentrated water and the nanofiltration concentrated water are delivered out for boiler ash flushing water, so that the near zero discharge of the coking wastewater concentrated brine is realized. The effluent quality reaches CODcr =30mg/L, F-= 4mg/L, TDS =200 mg/L, hardness =22 mg/L, alkalinity =30 mg/L.
The stability of the coking wastewater strong brine treatment system is tested, and during the operation period of 360h, the membrane pressure difference of the reverse osmosis unit is basically kept stable, and the membrane pressure difference is increased within 3%.
Example 2
The other conditions and operations were the same as in example 1 except that in the step (6), the modified molecular sieve was replaced with the modified molecular sieve obtained in preparation example 2 of the same mass.
The effluent quality of the embodiment reaches CODcr =30mg/L, F-= 8mg/L, TDS =220mg/L, hardness =28 mg/L, alkalinity = 40 mg/L.
The coking wastewater strong brine treatment system stability of the embodiment is tested, and the membrane pressure difference of the reverse osmosis unit is increased by 6% in the operation period of 360 h.
Example 3
The other conditions and operations were the same as in example 1 except that in the step (6), the modified molecular sieve was replaced with the modified molecular sieve obtained in preparation example 3 of the same mass.
The effluent quality of the embodiment reaches CODcr =30mg/L, F-= 9mg/L, TDS =260mg/L, hardness = 27mg/L, alkalinity =30 mg/L.
The coking wastewater strong brine treatment system stability of the embodiment is tested, and the membrane pressure difference of the reverse osmosis unit is increased by 10% in the operation period of 360 h.
Comparative example
The other conditions and operation were the same as in example 1 except that in step (6), the modified molecular sieve was not treated.
The effluent quality of the embodiment reaches CODcr =30mg/L, F-= 14mg/L, TDS =280mg/L, hardness =28 mg/L, alkalinity =30 mg/L.
The coking wastewater concentrated brine treatment system stability of the embodiment is tested, and the membrane pressure difference of the reverse osmosis unit rises by 18% in the operation period of 360 h. The reverse osmosis membrane needs to be replaced or cleaned to continue operation.
Example 4
Coking wastewater modification engineering of a certain company, wherein the water quality of inlet water: CODcr =510mg/L, F- = 160mg/L, TDS =9320 mg/L, hardness = 670mg/L, alkalinity = 350 mg/L.
The original process comprises the following steps: efficient sedimentation tank, multi-medium filter, ultrafiltration, nanofiltration, reverse osmosis and concentrated water reverse osmosis
The operation has problems: the nanofiltration membrane is easy to have the phenomenon of scaling on the surface of the membrane, and the main components of the nanofiltration membrane are calcium fluoride and calcium sulfate through analysis and analysis, and the nanofiltration membrane is very difficult to clean and recover; the surface of the reverse osmosis membrane and the interior of the water production tank are polluted and blocked by microorganisms; and the effluent quality is unstable, and the chemical cleaning is frequent.
The improved process comprises the following steps: the method comprises the steps of a first-stage efficient sedimentation tank, a second-stage efficient sedimentation tank, a multi-medium filter 1, ozone catalytic oxidation, a multi-medium filter 2, ultrafiltration, a weak acid cation bed, nanofiltration, concentrated water nanofiltration, reverse osmosis and concentrated water reverse osmosis
After transformation, hardness and fluorine ions are respectively treated in a first-stage efficient sedimentation tank and a second-stage efficient sedimentation tank, pH is adjusted to 11 and 9 in a reaction tank, so that calcium carbonate, magnesium hydroxide sediment and calcium fluoride sediment are respectively generated, fluorine ions in effluent are less than 15mg/l, and hardness is stabilized below 150 mg/l. The 'ozone contact oxidation' process is added, and is combined with the 'nanofiltration' technology, the COD is stably controlled below 135mg/l, meanwhile, the part which can not be removed is intercepted to the concentrated water side through nanofiltration, and the COD of the concentrated water side reaches 1200 mg/l. Adding a 'weak acid cation bed' process to form an 'ultrafiltration + weak acid cation bed + nanofiltration + reverse osmosis' technology, and reducing the hardness of inlet water of a membrane unit to the minimum by softening weak acid cation bed resin, wherein the COD of the final outlet water reaches 35mg/l, F-= 5mg/L, TDS =230mg/L, hardness =35 mg/L, alkalinity = 24mg/L, significantly reducing membrane system calcium magnesium scaling, calcium fluoride scaling, bio-fouling and organic fouling risks. The chemical cleaning frequency of the membrane system is greatly lengthened.
And (4) performing stability test, wherein the membrane pressure difference of the reverse osmosis unit is increased within 3% in the operation period of 360h, so that the long-time stable operation can be maintained.

Claims (6)

1. A coking wastewater strong brine near-zero emission treatment system comprises a regulating reservoir, a first-stage high-efficiency sedimentation tank, a second-stage high-efficiency sedimentation tank, a first-stage multi-medium filter, an ozone oxidation contact tank, a second-stage multi-medium filter, an ultrafiltration device, a weakly acidic cation exchange unit, a nanofiltration unit, a concentrated water nanofiltration unit, a reverse osmosis unit and a concentrated water reverse osmosis unit which are connected in sequence; the wastewater passes through the nanofiltration unit, the produced water enters the reverse osmosis unit, the concentrated water enters the concentrated water nanofiltration unit, the produced water of the nanofiltration unit and the concentrated water nanofiltration unit enters the reverse osmosis unit, the concentrated water produced by the reverse osmosis unit enters the concentrated water reverse osmosis unit, and the produced water of the reverse osmosis unit and the concentrated water reverse osmosis unit is combined for recycling; FeCl is added before the effluent of the weak acid cation exchange unit is subjected to nanofiltration3And SnCl4A co-modified molecular sieve;
the FeCl3And SnCl4The co-modified molecular sieve is prepared by a preparation method comprising the following steps: putting a molecular sieve into a quaternary ammonium salt surfactant solution, soaking at 50-60 ℃ under an ultrasonic condition, drying, and then putting into FeCl-containing solution3And SnCl4Soaking in the solution, taking out, washing and drying to obtain the product;
the quaternary ammonium salt surfactant is in a long-chain alkyl ammonium salt type or an alkyl benzyl ammonium type;
the molecular sieve, quaternary ammonium salt surfactant solution and the catalyst containing FeCl3And SnCl4The mass ratio of the solution (1): 5-10: 5-10; wherein the concentration of quaternary ammonium salt surfactant is 50-100mM, FeCl3In a concentration of 0.5-1M, SnCl4The concentration of (A) is 0.01-0.0.02M; soaking the molecular sieve in quaternary ammonium salt surfactant solution for 0.5-2h, and adding FeCl3And SnCl4The soaking time in the solution is 0.5-2 h;
the silicon-aluminum ratio of the molecular sieve is 2.5-3.
2. The coking wastewater concentrated brine near zero emission of claim 1The treatment system is characterized in that a defluorinating agent, a coagulant and a coagulant aid are added into the primary high-efficiency sedimentation tank, wherein the defluorinating agent is CaCl2And Ca (OH)2And LiCl at a mass ratio of 3-5: 1-2:1-2, the coagulant is selected from at least one of iron salt selected from ferric sulfate and ferric chloride, aluminum salt selected from aluminum chloride and aluminum sulfate, and polymer thereof selected from polymeric ferric sulfate, polymeric ferric chloride, polymeric aluminum chloride and polymeric aluminum sulfate; the coagulant aid is polyacrylamide, and the mass ratio of the defluorinating agent to the coagulant aid is 2-4:3-5: 1-2;
the agent added into the secondary high-efficiency sedimentation tank is a mixture of an agent for removing total hardness and a coagulant according to the mass ratio of 1-2:1, and the agent for removing total hardness is Ca (OH)2,Na2CO3And NaOH according to a mass ratio of 5-7: 1-2: 0.2-0.5, wherein the coagulant is polyaluminium chloride and polyaluminium polyphosphate chloride according to the mass ratio of 1-2: 1-2.
3. The coking wastewater concentrated brine near-zero emission treatment system of claim 1, wherein the primary multi-media filter and the secondary multi-media filter are carbon steel lining glue, anthracite filter material d10=1.2-1.5mm, quartz sand filter material d10=0.5-0.8mm, and cobblestone d10=2.0-4.0 mm; anthracite filter material d10=0.6-1.0mm, quartz sand filter material d10=0.2-0.4mm, and cobblestone d10=1.0-1.5mm in the second-stage multi-medium filter.
4. A method for treating coking wastewater concentrated brine by using the coking wastewater concentrated brine near-zero emission treatment system of any one of claims 1 to 3, comprising the following steps of:
(1) wastewater firstly converges into a regulating tank for regulating water quality, water quantity and water temperature;
(2) the effluent of the regulating reservoir enters a first-stage high-efficiency sedimentation tank, and a fluorine removal agent, a coagulant and a coagulant aid are added;
(3) enabling the supernatant of the first-stage high-efficiency sedimentation tank to flow into a second-stage high-efficiency sedimentation tank, and adding a medicament and a coagulant for removing the total hardness;
(4) pumping the supernatant of the secondary efficient sedimentation tank to a primary multi-media filter; the filtered produced water flows into an ozone contact oxidation pond, and the produced water is lifted to a second-stage multi-medium filter through a pump;
(5) the water produced by the secondary multi-medium filter enters an ultrafiltration unit;
(6) the effluent of the ultrafiltration unit flows into a weakly acidic cation exchange unit, is treated by a modified molecular sieve in an intermediate tank and is lifted to a nanofiltration unit by a pump;
(7) the concentrated water of the nanofiltration unit flows into a concentrated water nanofiltration unit for secondary nanofiltration, and the produced water of the nanofiltration unit and the produced water of the concentrated water nanofiltration unit flow into a reverse osmosis unit;
(8) the concentrated water generated by the reverse osmosis unit flows into the concentrated water reverse osmosis unit, and the produced water of the reverse osmosis unit and the concentrated water reverse osmosis unit is combined for recycling.
5. The method of claim 4, wherein the modified molecular sieve is added in an amount of 0.05 to 0.1kg per ton of wastewater;
the pH value of the first-stage efficient sedimentation tank in the step (2) is 9-10, the mass ratio of the defluorinating agent to the coagulant aid is 2-4:3-5:1-2, and the total dosage of the added defluorinating agent is 1-3kg per ton of wastewater;
in the step (3), the pH value of the secondary efficient sedimentation tank is 11-12, the mass ratio of the added agents for removing total hardness to the coagulant is 1-2:1-2, and the total amount of the added agents is 0.5-2kg per ton of wastewater.
6. The method of claim 5, wherein the ultrafiltration unit operating pressure in step (5) is from 0.3 to 0.6 MPa;
the operating pressure of the nanofiltration unit in the step (7) is 0.6-0.8MPa, and the operating pressure of the nanofiltration of the concentrated water is 5-6 MPa;
and (8) the concentration multiple of the reverse osmosis unit is 4-6 times, the concentration multiple of the concentrated water reverse osmosis unit is 1.5-2 times, and the final total wastewater concentration multiple is 8-10 times.
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