CN113526748A

CN113526748A - Method for recycling coking RO concentrated water by ion-exchange membrane electrolysis

Info

Publication number: CN113526748A
Application number: CN202010300572.7A
Authority: CN
Inventors: 朱筱滢; 潘红良; 金学文; 杨帆; 王传荟
Original assignee: SHANGHAI WUBAO ELECTROMECHANICAL TECHNOLOGY CO LTD; Baowu Carbon Material Technology Co ltd
Current assignee: SHANGHAI WUBAO ELECTROMECHANICAL TECHNOLOGY CO LTD; Baowu Carbon Material Technology Co ltd
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2021-10-22
Anticipated expiration: 2040-04-16
Also published as: CN113526748B

Abstract

The invention discloses a method for recycling coked RO concentrated water by an ion-exchange membrane electrolysis method, which comprises the steps of RO concentrated water concentration, micro-electrolysis, activated carbon adsorption, cyanogen, fluorine, sulfate radical and calcium and magnesium ion removal by a chemical method, and sodium chloride in the RO concentrated water is converted into utilizable sodium hypochlorite and sodium hydroxide solution by a diaphragm electrolysis method. The sodium hypochlorite and sodium hydroxide solution can be obtained by adopting the process of the invention, and can be used as a medicament for water treatment and can be recycled.

Description

Method for recycling coking RO concentrated water by ion-exchange membrane electrolysis

Technical Field

The invention relates to the field of wastewater treatment, in particular to a method for treating coking wastewater.

Background

Coking wastewater is generated by recycling byproducts such as tar, benzene and the like in the production process of obtaining coke and coal gas by coal pyrolysis. The coking wastewater has very complex components and high concentration, contains common organic pollutants such as quinoline, indole, pyridine, phenols, biphenyl and the like, contains inorganic pollutants such as fluoride ions, ammonia nitrogen, cyanogen and the like, and is typical toxic wastewater which is difficult to degrade and biochemically. For this reason, in 12 months in 2008, the ministry of industry and trust issued "admission conditions of coking industry (revision in 2008)" clearly stipulate that the structure of the coking industry is optimized and upgraded: the phenol-cyanogen wastewater is recycled after qualified treatment and is not discharged outside. The current "emission standard for pollutants from the coking chemical industry" (GB16171-2012) states: and beginning 1/2015, the existing enterprises will implement the water pollutant emission concentration limit of the newly-built enterprises.

In order to meet the requirement of no discharge of coking wastewater, a great deal of research work is carried out by various coal chemical enterprises, and the coking wastewater is treated based on a membrane separation technology, and the approximate process route is shown in figure 1. In the process route, after the coking wastewater is subjected to biochemical treatment, most of organic matters in the wastewater are effectively removed, the wastewater is subjected to ultrafiltration, nanofiltration and reverse osmosis treatment to obtain pure reuse water, and 90% of the coking wastewater can be reused by the process. For concentrated water generated by nanofiltration and reverse osmosis, because the concentrated water contains organic matters which are difficult to degrade and a large amount of inorganic matters, the concentrated water needs to be further treated with great difficulty and high cost. For this reason, there are two approaches to the existing treatment of this part of wastewater: the method has the disadvantages that the waste water contains a large amount of chlorides, the chlorides are decomposed due to the high temperature action in the incineration process, corrosive media are generated, the corrosion of equipment and the exhaust emission do not reach the standard, and therefore the method cannot meet the treatment requirements of the two strands of concentrated water. Secondly, the two strands of concentrated water are evaporated and concentrated, the waste water after the concentrated water is evaporated and crystallized to obtain mixed salt, but the mixed salt contains a large amount of organic substances and cyanides besides sulfate and chloride, the obtained salt is a solid hazardous substance, and the hazardous substance is not processed well.

At present, patent of application No. 200410040215.2 entitled "a coking wastewater treatment and recycling technology" discloses that a physical and chemical method is adopted to treat coking wastewater, pollutants such as ammonia nitrogen, phenol, cyanogen, suspended matters and the like in the coking wastewater are removed to reach the recycling standard, and then the treated coking wastewater is used as production water to be recycled to other internal systems such as converter dust removal, coking ammonia washing, sintering and the like. However, this method is undoubtedly "secondary utilization" of the coking wastewater. The method recycles the wastewater, and the recycled wastewater is not introduced, the generation amount of the coking wastewater is large, and the recycling demand can not necessarily reach the yield of the coking wastewater.

Under the current environment, on one hand, the state has a strict drainage limiting measure, and on the other hand, no ready-made coking wastewater zero discharge technology exists, so that the invention can meet the national policy and realize the aim of coking wastewater zero discharge, and has undoubtedly important practical significance for the development of the coking industry.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to provide a method for recycling substances in wastewater by carrying out impurity removal treatment on RO concentrated water in coking wastewater treatment and converting the wastewater into useful resources by adopting an electrolysis method.

The technical proposal of the invention is that a method for recycling coking RO concentrated water by an ion membrane electrolysis method,

a. the RO concentrated water is used for increasing the salt concentration in the wastewater to 9% -10% through a first MVR evaporator, the pH value of the concentrated salt water is adjusted to 4.0-4.5, then the concentrated salt water enters a micro-electrolysis reactor to react for 2-3 hours, and then the wastewater enters a first activated carbon adsorption tower to be adsorbed for more than 2 hours;

b. carrying out decyanation reaction on the adsorbed RO concentrated water in a decyanation reactor, then carrying out defluorination reaction in a defluorination reactor, removing sulfate radicals in a sulfate radical removal reactor, and finally carrying out Ca and Mg ion removal reaction in a Ca and Mg removal reactor;

c. adding a flocculating agent into the obtained reaction liquid, then realizing solid-liquid separation in a settling tank, discharging the precipitate, allowing the clear liquid after precipitation to pass through a sand filter and enter a second MVR evaporation concentrator to concentrate the solution into a solution containing 18-20% of sodium chloride, and respectively adsorbing residual organic matters and metal cations in the solution by a second activated carbon absorption tower and a coupling resin adsorption tower to obtain pure 18-20% saline water, wherein the saline water is stored in a saline water head tank for later use;

d. the brine in the brine head tank is heated to 80-85 ℃ by a brine heater and then enters the ion membrane electrolytic cell, the anode in the ion membrane electrolytic cell generates chlorine, the chlorine is absorbed by dilute sodium hydroxide solution in a sodium hypochlorite generating tower to generate sodium hypochlorite solution, the sodium hypochlorite solution is discharged from the bottom of the tower, the dilute sodium hydroxide solution is sprayed into the tail gas absorption tower at the top of the tail gas absorption tower to purify the tail gas, and the tail gas is discharged into the atmosphere through a tail gas fan.

In the step a, the reaction is carried out in a micro-electrolysis reactor, so as to partially remove organic matters and heavy metal ions in the micro-electrolysis reactor. And then the wastewater enters a first activated carbon adsorption tower for adsorption so as to further remove organic matters in the wastewater. From the aspect of treatment effect, the micro-electrolysis reaction time is 2-3 hours, and a better effect on the decomposition of COD is achieved. From the aspect of consumption of the micro-electrolysis filler, with the progress of micro-electrolysis, iron in the iron-carbon filler is gradually consumed, so that carbon particles are gradually loosened and finally fall off, and the consumption of the micro-electrolysis filler is large due to long-time micro-electrolysis under the same wastewater treatment capacity. The activated carbon adsorption has the effect of reducing the COD of the solution, and the COD of the solution is not obviously reduced after 2 hours of adsorption. Preferably, the wastewater enters the first activated carbon adsorption tower for adsorption for 2 to 3 hours.

No matter which process is adopted to remove impurities in RO concentrated water, the impurities cannot be completely removed, if the impurities in the original RO concentrated water are directly removed, the removed waste water still has residual impurities, the impurities are also concentrated along with the impurities in the subsequent concentration process, the impurity content in finally generated sodium hypochlorite exceeds the standard, and therefore the waste water needs to be concentrated firstly, and the impurities are concentrated and then treated. If this step concentrates the RO concentrate to a salt content below 9%, there is a risk of causing the final sodium hypochlorite to contain excessive levels of impurities, and since there is a second MVR evaporative concentrator following it, it is not necessary to concentrate the salt content to above 10%.

Step a, adjusting the pH value to 4.0-4.5, and adding acid for adjustment. The RO concentrated water is alkalescent, and the pH value of the RO concentrated water needs to be adjusted to 4.0-4.5 in order to meet the micro-electrolysis requirement. Preferably, the solution contains a large amount of chloride ions, and the pH value is adjusted to 4.0-4.5 by using a hydrochloric acid solution so as not to introduce other impurities.

In step b, after the RO concentrated water is subjected to the reaction, solid precipitates are formed by inorganic impurities in the concentrated water.

And carrying out pressure filtration on the precipitate in the settling tank through a pressure filter, wherein a solution storage tank obtained by pressure filtration is arranged in a pressure filtration water collecting tank, and the obtained mud cake is discharged as solid waste.

After high-concentration (18% -20%) saline water is electrolyzed, its concentration can be reduced, and to ensure the electrolytic efficiency, the dilute saline water in anode chamber of the described ion membrane electrolytic cell can be discharged into dilute saline water storage tank, and said dilute saline water can be pumped into second MVR evaporator to make concentration.

The conductivity of the solution is related to the salt content, the salt content is low, the conductivity of the wastewater is low, the resistance is large, the current efficiency in the electrolytic process is low, the solution temperature is quickly increased due to the large resistance of the solution, and the solution temperature is not easy to control. The salt concentration is lower than 18%, the ionic membrane is easy to foam, the service life of the membrane is shortened, the production efficiency is reduced, the salt concentration exceeds 20%, and the salt is easy to crystallize and separate out in a conveying pipeline and a heater to block the pipeline and the heater.

According to the method for resource utilization of the coking RO concentrated water by the ion membrane electrolysis method, preferably, the micro-electrolysis reactor in the step a is a cylindrical container, and spherical micro-electrolysis iron-carbon materials are filled in the container;

the spherical microelectrolytic iron-carbon material mainly comprises iron and carbon, and also contains a small amount of catalyst, activator and the like, and the shape of the spherical microelectrolytic iron-carbon material is oval.

Preferably, the activated carbon adsorption tower in the step a is a cylindrical container, the activated carbon is coal spherical activated carbon, and the specific surface area of the activated carbon is not less than 900m²/g。

Further, the volume of the micro-electrolysis reactor container is 2-3 times of the RO concentrated water treatment water amount; the volume of the activated carbon adsorption tower container is 2-3 times of the RO concentrated water treatment water amount.

According to the method for resource utilization of the coking RO concentrated water by the ion membrane electrolysis method, preferably, the cyanogen removal reactor in the step b is provided with a stirring device; the initial pH value of the solution is required to be between 5.0 and 5.5, the cyanogen removal reaction time is 60 to 120 minutes, then the pH value is adjusted to 10.0 to 10.5 by adopting alkali liquor, and the reaction time is 30 to 60 minutes; the initial pH of the solution is the initial pH of the solution as it enters the decyanation reactor.

The defluorination reactor in the step b is provided with a stirring device; calcium chloride is adopted for defluorination, and the defluorination reaction time is 40-60 minutes;

the sulfate radical removal reactor in the step b is provided with a stirring device; barium chloride is adopted to remove sulfate radicals; the sulfuric acid removal reaction time is 40-60 minutes;

the Ca removal reactor in the step b is provided with a stirring device; the reaction time for removing Ca is 30-60 minutes.

Further, the cyanogen removal in the step b adopts an iron method process, the used cyanogen removal agent is ferrous chloride, and 23.0g to 28.5g of ferrous chloride is added according to per liter of treatment water; the rotation speed of the stirring device in the decyanation reactor is 60-200rpm, and the ferrous chloride is added in a solid form.

The addition amount of the calcium chloride in the step b is 36.5 g-50 g per liter of water; the rotating speed of the stirring device of the defluorination reactor is 60-200rpm. The calcium chloride is added in solid form.

And c, adding the barium chloride in the step b in an amount which is 1.0-1.1 times of the concentration of the sulfate ions. The addition amount of the barium chloride in the step b is added according to the concentration of sulfate ions in the RO concentrated water, the addition amount of the barium chloride is added according to the amount which is 1.0-1.1 times of the concentration of the sulfate ions, and the barium chloride is added in a solid form; the rotating speed of the stirring device of the sulfate radical removal reactor is 60-200rpm.

The calcium remover used in the step b is sodium carbonate, and the addition amount of the sodium carbonate is 20-25 g per liter of water; the speed of the stirring device of the Ca removal reactor was 60-200rpm sodium carbonate was added as a solid.

According to the method for resource utilization of the coking RO concentrated water by the ion membrane electrolysis method, preferably, a flocculating agent is adopted for flocculation and sedimentation in the wastewater obtained by impurity removal reaction in the step b; the molecular weight of the flocculant is 600-2000 ten thousand.

Further, the flocculant is prepared into a 0.02-0.2 wt% solution, and the flocculant solution is added in a volume ratio of 0.05-2% of the amount of the wastewater.

The flocculant solution is added to the wastewater line. The flocculant is an anionic PAM flocculant. In the process of removing impurities in wastewater, the impurities are all formed into precipitates to be separated out, the particle size of the precipitates is very small, the precipitates are difficult to naturally settle, and the precipitates need to be flocculated into larger particles by a flocculating agent, so that the precipitates are quickly settled under the action of gravity, and the subsequent solid-liquid separation is facilitated.

According to the method for resource utilization of the coking RO concentrated water by the ion membrane electrolysis method, preferably, in the step c, the wastewater solution added with the flocculating agent enters a precipitation tank for precipitation, the wastewater enters a central downcomer of the precipitation tank, and clear water overflows from the outer circumference; and the precipitate is subjected to solid-liquid separation at the bottom of the settling tank by adopting a filter press, the separated mud cake is discharged from a mud cake discharge port as solid waste, and the pressure filtrate is stored in a pressure filtrate collecting tank.

And c, after passing through a sand filter, the clear liquid overflowing from the settling tank enters a second MVR evaporator for concentration, concentrated water is concentrated to 18-20% in the evaporator, residual organic matters in the high-concentration brine are adsorbed by a second activated carbon adsorption tower to remove organic substances in the high-concentration brine, and then the high-concentration brine enters a coupling resin adsorption tower to remove metal ions in the high-concentration brine. The purified strong brine is stored in a brine head tank.

The method comprises the following steps of heating concentrated brine to 80-85 ℃ by a heater, flowing the heated concentrated brine into an anode chamber of an electrolytic cell at a set flow rate, wherein the electrolytic cell is a diaphragm type electrolytic cell, electrolyzing the concentrated brine in the electrolytic cell to generate chlorine at an anode and hydrogen at a cathode, and using a sodium hydroxide solution as a catholyte, wherein the concentration of the sodium hydroxide can reach 10% -11%. The brine in the anode chamber is electrolyzed, the concentration of the brine is reduced, the brine with low concentration is discharged from the bottom of the electrolytic cell and enters a dilute brine collecting tank, and the dilute brine flows back to the second MVR evaporator for cyclic concentration and utilization.

And d, adsorbing chlorine generated by the anode into a sodium hypochlorite generating tower through a tail gas fan, wherein the sodium hypochlorite generating tower is a packed tower, and the chlorine is fully contacted with an absorption liquid at the outlet of the tail gas absorption tower in the tower to produce a sodium hypochlorite solution and is discharged from the bottom of the tower.

According to the method for recycling the coking RO concentrated water by the ion membrane electrolysis method, preferably, in the step c, the settled clear liquid enters a sand filter in an overflow mode. Through the overflow mode, can make sediment entering sand rate ware as little as possible. The service life of the sand rate device can be prolonged.

According to the method for resource utilization of the coking RO concentrated water by the ion membrane electrolysis method, the mass concentration of the dilute sodium hydroxide solution in the step d is preferably 7-15%; the concentration of the generated sodium hypochlorite is 6-13%.

After the coking wastewater is subjected to biochemical treatment, most organic matters in the coking wastewater are degraded, substances such as some organic matters which are difficult to degrade and cyanogen complex still exist in the wastewater, and organic and inorganic substances in the wastewater exist in concentrated water after being intercepted by a nanofiltration membrane and a reverse osmosis membrane, so that the components of the concentrated water are complex. The substance types in the overall concentrated water mainly include: organic, fluoride, cyanide (simple and complex), sulfate, NH₃-N, chloride, Ca²⁺And Mg²⁺And (3) metal ions, which are toxic and harmful substances and need to be treated by a special method.

The invention has the innovation point that the sodium chloride in the RO concentrated water is converted into sodium hypochlorite and sodium hydroxide solution by a diaphragm electrolysis method.

Aiming at the characteristics of various components in the RO concentrated water, the process flow for recycling the concentrated water comprises the following steps: the RO concentrated water is concentrated by a first MVR evaporator and then the salt concentration in the wastewater is increased to 9-10%, part of organic matters in the high-concentration salt water are degraded by a micro-electrolysis reactor and enter an active carbon adsorption tower to further remove the organic matters, then the salinity concentrated water is subjected to decyanation in a decyanation reactor, defluorination in a defluorination reactor and sulfate radical removal in a sulfate radical removal reactor, and Ca and Mg are removed in a Ca and Mg removal reactor²⁺And Mg²⁺Ions and harmful substances in the wastewater form solid precipitates after reaction, the solid precipitates are precipitated in a precipitation tank under the action of a flocculating agent, the main component in the RO concentrated water after sedimentation separation is sodium chloride, the sodium chloride solution enters a second-stage MVR for concentration after sand filtration, so that the sodium chloride solution reaches 18% -20%, and the clean high-concentration brine is stored in a head tank after the saturated sodium chloride solution is adsorbed by second-stage activated carbon and coupling resin. The method comprises the steps that high-concentration brine is heated to 80-90 ℃ through a heat exchanger at a certain flow rate and then enters an anode chamber of an ion membrane electrolytic cell, chlorine is generated in the anode chamber under the action of high current density, the chlorine is introduced into a sodium hydroxide solution and reacts to generate a high-concentration sodium hypochlorite solution (about 10%), the sodium hypochlorite can be sold or used by oneself as a commodity, hydrogen generated by a cathode is discharged outwards, and catholyte is the high-concentration sodium hydroxide solution. A typical process flow is shown in figure 2.

Has the advantages that:

the invention aims at the current coking wastewater treatment technology and the composition of the coking wastewater, and on the basis of the current coking wastewater treatment technology, the invention provides a method for removing impurities from RO concentrated water in the coking wastewater treatment, and the method converts the wastewater into useful resources by using the main component sodium chloride in the wastewater and adopting an electrolysis method, thereby realizing the recycling of substances in the wastewater and solving the last one kilometer in the coking wastewater treatment.

The RO concentrated water can be subjected to impurity removal, concentration and electrolysis to generate a sodium hypochlorite solution and a sodium hydroxide solution which can be used as reagents for water treatment, most of the RO concentrated water in the prior art is subjected to impurity removal and then is subjected to evaporation crystallization to generate an industrial sodium chloride product with lower price, and the sodium hypochlorite and the sodium hydroxide solution generated by the method are common reagents in the aspect of wastewater treatment.

Drawings

FIG. 1 is a flow chart of the process for recycling coking wastewater.

FIG. 2 is a process flow diagram for resource utilization of RO concentrated water in the invention.

In the figure, 1. a first MVR evaporator; 2. a micro-electrolysis reactor; 3. a first activated carbon adsorption tower; 4. a decyanation reactor; 5. a defluorination reactor; 6. a sulfate radical removal reactor; 7. a reactor for removing Ca and Mg; 8. a flocculant addition port; 9. a settling tank; 10. a sand filter; 11. a second MVR evaporator; 12. a second activated carbon adsorption tower; 13. coupling a resin adsorption tower; 14. a brine head tank; 15. a brine heater; 16. an ionic membrane electrolytic cell; 17. a hydrogen gas discharge port; 18. a sodium hypochlorite generation tower; 19. a tail gas adsorption tower; 20. sodium hydroxide adsorption solution; 21. a tail gas fan; 22. a sodium hypochlorite discharge outlet; 23. a sodium hydroxide air outlet; 24. a dilute brine storage tank; 25. a filter press; 26. pressing a filtrate collecting tank; 27. a mud cake discharge port.

Detailed Description

Example 1

The RO concentrated water is lifted to the salt concentration of 9 percent in the wastewater by a first MVR evaporator 1, the concentrated salt water is adjusted to the pH value of 4 by hydrochloric acid solution (the hydrochloric acid is mixed with the water in a volume ratio of 1: 1), and then enters a cylindrical micro-electrolysis reactor 2 filled with spherical micro-electrolysis iron-carbon materials, the volume of the container is 2 times of the RO concentrated water treatment water volume, and the reaction is carried out for 2 hours; after micro-electrolysis, the solution enters a cylindrical adsorption tower 3 filled with coal spherical active carbon, and the specific surface area of the active carbon is not less than 900m²The volume of the container is 2 times of the treatment water quantity of the RO concentrated water, and the adsorption reaction is carried out for 2 hours; after the adsorption reaction, the solution is passed through hydrochloric acid solution (hydrochloric acid and water)1:1 volume ratio) until the pH value is 5.0, adding the mixture into a decyanation reactor 4 with a stirring device, wherein the rotating speed of the stirrer is 60rpm, adding a decyanation agent (ferrous chloride), the adding amount of the ferrous chloride is 23.0g per liter of treated water, reacting for 30min, adjusting the pH value with a sodium hydroxide solution until the end-point pH value is 10.0, and reacting for 30 min; after the cyanogen removal reaction is finished, the solution enters a defluorination reactor 5 with a stirring device, the rotating speed of the stirrer is 60rpm, calcium chloride is adopted for defluorination, the adding amount of the calcium chloride is 36.5g per liter of water, the calcium chloride is added in a solid form, and the defluorination reaction time is 40 min; after the defluorination reaction is finished, the solution enters a sulfate radical removal reactor 6 with a stirring device, the rotating speed of the stirrer is 60rpm, barium chloride is adopted to remove sulfate radicals, the adding amount of the barium chloride is 25g per liter of water, the barium chloride is added in a solid form, and the reaction is carried out for 40 min; after the sulfate radical removal reaction is finished, the solution enters a Ca removal reactor 7 with a stirring device, the rotating speed of the stirrer is 60rpm, the used calcium removal agent is sodium carbonate, the adding amount of the sodium carbonate is 20g per liter of water, the sodium carbonate is added in a solid form, and the reaction is carried out for 30 min; after the impurity removal reaction is finished, the solution enters a sedimentation reaction tank 9, an anionic PAM flocculant is adopted for flocculation sedimentation, the flocculant is added from a flocculant adding port 8, the molecular weight of the flocculant is 600-2000 ten thousand, the flocculant is prepared into 0.1% solution, and a flocculant solution is added according to 1% of the amount of wastewater; the waste water solution added with the flocculating agent enters a precipitation tank for precipitation, the waste water enters a central descending pipe of the precipitation tank, clear water overflows from the outer circumference, the precipitate is subjected to solid-liquid separation at the bottom of the tank by adopting a filter press 25, the mud cake obtained by separation is discharged as solid waste from a mud cake discharge port 27, and the press filtrate is stored in a press filtrate collecting tank 26; clear liquid overflowing from the settling tank enters a second MVR evaporator 11 for concentration after passing through a sand filter 10, concentrated water is concentrated to 18% in the evaporator, residual organic matters in high-concentration brine are adsorbed by a second activated carbon adsorption tower 12 to remove organic matters in the high-concentration brine, then the high-concentration brine enters a coupling resin adsorption tower 13 to remove metal ions in the high-concentration brine, and purified strong brine is stored in a brine head tank; the strong brine flowing out of the head tank is heated to 80-85 ℃ by a heat exchanger and then flows into the anode of the electrolytic tank 16 at a set flow rateThe electrolytic cell is a diaphragm type electrolytic cell, strong brine is electrolyzed in the electrolytic cell, chlorine is generated at the anode, hydrogen is generated at the cathode, the catholyte is sodium hydroxide solution, and the concentration of the sodium hydroxide can reach 10%. The concentration of the brine in the anode chamber is reduced after electrolysis, the low-concentration brine is discharged from the bottom of the electrolytic cell and enters a dilute brine collecting tank, and the dilute brine flows back to the second MVR evaporator for cyclic concentration and utilization; chlorine that the positive pole produced passes through the tail gas fan and adsorbs entering into sodium hypochlorite and take place tower 18, and sodium hypochlorite takes place the tower and is the packed tower, and chlorine is in this tower fully contact with the absorption liquid of 19 exports of tail gas absorption tower, produces sodium hypochlorite solution, and the bottom 21 of tower discharges.

Coking wastewater with COD of 1100mg/L, T-N concentration of 246mg/L, fluoride ion concentration of 275mg/L and total cyanide of 5.23mg/L is pretreated by the method and electrolyzed by an ion membrane to obtain absorption liquid (sodium hypochlorite solution) with effective chlorine content of 6%, total cyanide of 0.05mg/L, COD of 67mg/L, T-N concentration of 10.57mg/L and fluoride ion concentration of 9.5 mg/L; the concentration of alkali produced by the cathode is 10%, the resource utilization of RO concentrated water is realized, and the last one kilometer problem in the zero discharge of the coking wastewater is solved.

Example 2

The RO concentrated water is lifted to the salt concentration of 10% in the wastewater through a first MVR evaporator 1, the concentrated saline water is adjusted to the pH value of 4.5 through a hydrochloric acid solution, and then enters a cylindrical micro-electrolysis reactor 2 filled with spherical micro-electrolysis iron-carbon materials, the volume of the container is 2 times of the RO concentrated water treatment water volume, and the reaction lasts for 2 hours; after micro-electrolysis, the solution enters a cylindrical adsorption tower 3 filled with coal spherical active carbon, and the specific surface area of the active carbon is not less than 900m²The volume of the container is 2 times of the treatment water quantity of the RO concentrated water, and the adsorption reaction is carried out for 2 hours; after adsorption reaction, adjusting the pH value of the solution to 5.5 by using a hydrochloric acid solution, feeding the solution into a cyanogen removal reactor 4 with a stirring device, wherein the rotating speed of the stirrer is 60rpm, adding a cyanogen removal agent (ferrous chloride), adding 28.5g of ferrous chloride according to the treated water per liter, reacting for 30min, adjusting the pH value by using a sodium hydroxide solution until the end-point pH value is 10.5, and reacting for 30 min; after the cyanogen removal reaction is finished, the solution enters a defluorination reactor 5 with a stirring device,the rotating speed of the stirrer is 60rpm, calcium chloride is adopted for defluorination, the addition amount of the calcium chloride is 50g per liter of water, the calcium chloride is added in a solid form, and the defluorination reaction time is 40 min; after the defluorination reaction is finished, the solution enters a sulfate radical removal reactor 6 with a stirring device, the rotating speed of the stirrer is 60rpm, barium chloride is adopted to remove sulfate radicals, the adding amount of the barium chloride is 30g per liter of water, the barium chloride is added in a solid form, and the reaction is carried out for 40 min; after the sulfate radical removal reaction is finished, the solution enters a Ca removal reactor 7 with a stirring device, the rotating speed of the stirrer is 60rpm, the used calcium removal agent is sodium carbonate, the adding amount of the sodium carbonate is 25g per liter of water, the sodium carbonate is added in a solid form, and the reaction is carried out for 30 min; after the impurity removal reaction is finished, the solution enters a sedimentation reaction tank 9, a flocculating agent is added from a flocculating agent adding port 8, an anionic PAM flocculating agent is adopted for flocculation sedimentation, the molecular weight of the flocculating agent is 600-2000 ten thousand, the flocculating agent is prepared into 0.1% solution, and a flocculating agent solution is added according to 1% of the amount of wastewater; the wastewater solution added with the flocculating agent enters a precipitation tank for precipitation, the wastewater enters a central downcomer of the precipitation tank, clear water overflows from the outer circumference, the precipitate is subjected to solid-liquid separation at the bottom of the tank by adopting a filter press 25, a mud cake obtained by separation is discharged as solid waste, and a press filtrate is stored in a press filtrate collecting tank 26; clear liquid overflowing from the settling tank enters a second MVR evaporator 11 for concentration after passing through a sand filter 10, concentrated water is concentrated to 20% in the evaporator, residual organic matters in high-concentration brine are adsorbed by a second activated carbon adsorption tower 12 to remove organic matters in the high-concentration brine, then the high-concentration brine enters a coupling resin adsorption tower 13 to remove metal ions in the high-concentration brine, and purified strong brine is stored in a brine head tank; the concentrated brine flowing out of the head tank is heated to 80-85 ℃ by a heat exchanger and then flows into an anode chamber of an electrolytic tank 16 at a set flow rate, the electrolytic tank is a diaphragm type electrolytic tank, the concentrated brine is electrolyzed in the electrolytic tank, chlorine is generated at an anode, hydrogen is generated at a cathode, the catholyte is a sodium hydroxide solution, and the concentration of the sodium hydroxide can reach 10%. The concentration of the brine in the anode chamber is reduced after electrolysis, the low-concentration brine is discharged from the bottom of the electrolytic cell and enters a dilute brine collecting tank, and the dilute brine flows back to the second MVR evaporator for cyclic concentration and utilization; anodeThe chlorine that produces passes through the tail gas fan and adsorbs and enter into sodium hypochlorite and take place tower 18, and sodium hypochlorite takes place the tower and be the packed tower, and chlorine is in this tower and the absorption liquid of 19 exports of tail gas absorption tower fully contacts, produces sodium hypochlorite solution, and the bottom 21 of tower discharges.

Coking wastewater with COD of 1100mg/L, T-N concentration of 246mg/L, fluoride ion concentration of 275mg/L and total cyanide of 5.23mg/L is pretreated by the method and electrolyzed by an ion membrane to obtain absorption liquid (sodium hypochlorite solution) with effective chlorine content of 7.5%, total cyanide of 0.03mg/L, COD of 63mg/L, T-N concentration of 10.17mg/L and fluoride ion concentration of 9.2 mg/L; the concentration of alkali produced by the cathode is 11%, the resource utilization of RO concentrated water is realized, and the last one kilometer problem in the zero discharge of the coking wastewater is solved.

Claims

1. A method for resource utilization of coking RO concentrated water by an ion membrane electrolysis method is characterized by comprising the following steps:

a. the RO concentrated water is used for increasing the salt concentration in the wastewater to 9% -10% through a first MVR evaporator (1), the pH value of the concentrated salt water is adjusted to 4.0-4.5, then the concentrated salt water enters a micro-electrolysis reactor (2) to react for 2-3 hours, and then the wastewater enters a first activated carbon adsorption tower (3) to be adsorbed for more than 2 hours;

b. the adsorbed RO concentrated water is firstly subjected to decyanation reaction in a decyanation reactor (4), then subjected to defluorination reaction in a defluorination reactor (5), subjected to sulfate radical removal reaction in a sulfate radical removal reactor (6), and finally subjected to Ca and Mg ion removal reaction in a Ca and Mg removal reactor (7);

c. adding a flocculating agent into the obtained reaction liquid, then realizing solid-liquid separation in a settling tank (9), discharging precipitates, allowing the precipitated clear liquid to pass through a sand filter (10) and then enter a second MVR evaporation concentrator (11) to concentrate the solution into a solution containing 18-20% of sodium chloride, adsorbing residual organic matters and metal cations in the solution by a second activated carbon absorption tower (12) and a coupling resin adsorption tower (13) respectively to obtain pure 18-20% saline water, and storing the saline water in a saline water head tank (14) for later use;

d. brine in the brine head tank is heated to 80-85 ℃ through a brine heater (15) and then enters an ion membrane electrolytic cell (16), an anode in the ion membrane electrolytic cell generates chlorine, the chlorine is absorbed by a dilute sodium hydroxide solution in a sodium hypochlorite generating tower (18), the generated sodium hypochlorite solution is discharged from the bottom (22) of the tower, the dilute sodium hydroxide solution is sprayed into a tail gas absorption tower at the top (20) of the tail gas absorption tower (19) and is used for purifying tail gas, and the tail gas is discharged into the atmosphere through a tail gas fan (21).

2. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 1, which is characterized in that: the micro-electrolysis reactor (2) is a cylindrical container, and spherical micro-electrolysis iron-carbon materials are filled in the container;

the activated carbon adsorption tower (3) in the step a is a cylindrical container, the activated carbon is coal spherical activated carbon, and the specific surface area of the activated carbon is not less than 900m²/g。

3. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 2, which is characterized in that: the volume of the container of the micro-electrolysis reactor (2) is 2-3 times of the RO concentrated water treatment water amount; the volume of the container of the activated carbon adsorption tower (3) is 2-3 times of the RO concentrated water treatment water volume.

4. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 1, which is characterized in that:

the decyanation reactor (4) in the step b is provided with a stirring device; the initial pH value of the solution is required to be between 5.0 and 5.5, the cyanogen removal reaction time is 60 to 120 minutes, then the pH value is adjusted to 10.0 to 10.5 by adopting alkali liquor, and the reaction time is 30 to 60 minutes;

the defluorination reactor (5) in the step b is provided with a stirring device; calcium chloride is adopted for defluorination, and the defluorination reaction time is 40-60 minutes;

the sulfate radical removal reactor (6) in the step b is provided with a stirring device; barium chloride is adopted to remove sulfate radicals; the sulfuric acid removal reaction time is 40-60 minutes;

the Ca removing reactor (7) in the step b is provided with a stirring device; the reaction time for removing Ca is 30-60 minutes.

5. The method for recycling coking RO concentrated water by the ion membrane electrolysis method according to claim 4, which is characterized in that:

the cyanogen removal in the step b adopts an iron method process, the cyanogen removal agent is ferrous chloride, and 23.0 g-28.5 g of ferrous chloride is added according to per liter of treatment water; the rotating speed of a stirring device in the decyanation reactor (4) is 60-200 rpm;

the addition amount of the calcium chloride in the step b is 36.5 g-50 g per liter of water; the rotating speed of a stirring device of the defluorination reactor (5) is 60-200 rpm;

the addition amount of the barium chloride in the step b is 1.0-1.1 times of the concentration of the sulfate ions;

the calcium remover used in the step b is sodium carbonate, and the addition amount of the sodium carbonate is 20-25 g per liter of water; the rotating speed of the stirring device of the Ca removing reactor (7) is 60-200rpm.

6. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 1, which is characterized in that:

b, flocculating and settling the wastewater obtained by impurity removal reaction by using a flocculating agent; the molecular weight of the flocculant is 600-2000 ten thousand.

7. The method for recycling coking RO concentrated water by the ion membrane electrolysis method according to claim 6, which is characterized in that:

the flocculant is prepared into 0.02-0.2 wt% solution, and the flocculant solution is added according to the volume ratio of 0.05-2% of the waste water amount.

8. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 1, which is characterized in that:

in the step c, the wastewater solution added with the flocculating agent enters a precipitation tank for precipitation, the wastewater enters a central downcomer of the precipitation tank, and clear water overflows from the outer circumference; the sediment is subjected to solid-liquid separation at the bottom of the settling tank by a filter press (25), mud cakes obtained by separation are discharged as solid waste, and filter pressing liquid is stored in a filter pressing liquid collecting tank (26).

9. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 1, which is characterized in that: in step c, the clear liquid after precipitation enters a sand filter (10) in an overflow mode.

10. The method for recycling the coking RO concentrated water by the ion membrane electrolysis method according to claim 1, which is characterized in that: d, the mass concentration of the dilute sodium hydroxide solution is 7-15%; the concentration of the generated sodium hypochlorite is 6-13%.