1. A coking wastewater advanced treatment and reclaimed water recycling method comprises the following steps:

(1) preheating and decomposing the coking wastewater, pumping the coking wastewater into an ammonia still, evaporating ammonia through steam in the ammonia still, and condensing or absorbing sulfuric acid to obtain crude concentrated ammonia water or ammonium sulfate;

(2) the wastewater enters an oil separation tank to remove heavy oil after ammonia evaporation treatment, then is subjected to pressurized air flotation treatment in an air flotation tank to remove emulsified oil and dispersed oil in water, and the effluent after oil removal enters the next procedure for biochemical treatment after oxygen removal treatment;

(3) after oil removal and oxygen removal, the effluent is treated by an A/O biochemical system to degrade phenolic compounds, nitrogen-containing heterocyclic compounds and COD in the water, and the effluent enters the next procedure;

(4) the effluent of the A/O biochemical system enters a secondary sedimentation tank for sludge-water separation, part of the activated sludge is used for sludge backflow, and the rest sludge is sent to a sludge treatment system;

(5) after biochemical reaction, the effluent enters an advanced oxidation system for advanced treatment, the wastewater is pretreated by acid adjustment and is treated by heating catalytic oxidation, and the effluent enters the next procedure after fine adjustment;

(6) the effluent of the deep oxidation system enters an electrolytic barrel of an electro-catalytic system, and a high oxygen evolution potential close to a diamond film electrode is generated by an anode, so that ammonia nitrogen and organic matters in sewage are thoroughly removed, the effluent is ensured to stably meet the direct discharge standard, and the effluent is recycled after reaction.

2. The coking wastewater advanced treatment and reclaimed water recycling process according to claim 1, characterized in that a process combining negative pressure stripping deamination and ammonia jet absorption is adopted in the step (1), a guide float valve tower is adopted as an ammonia still, the pH of inlet water of the ammonia still is 8-9, the temperature of steam at the top of the tower is 90-103 ℃, and the ammonia nitrogen removal efficiency is 95%.

3. The coking wastewater advanced treatment and reclaimed water recycling process according to claim 1, characterized in that the air flotation tank in the step (2) adopts a pressurized dissolved air flotation method, air is used as an air source, the efficiency of removing suspended matters and the efficiency of removing oil can reach 80%, and 10% -35% of COD can be removed.

4. The coking wastewater advanced treatment and reclaimed water recycling process according to claim 1, characterized in that the A/O biochemical system in the step (3) adopts the design of an anaerobic tank and an aerobic tank, and a biofilm method with a filler is adopted in the anaerobic tank; the aerobic tank is provided with a microporous aerator. Phenolic compounds and nitrogen-containing heterocyclic compounds are converted and degraded in an anaerobic section, and high-concentration COD in water is degraded in an aerobic section.

5. The coking wastewater advanced treatment and reclaimed water recycling process according to claim 1, characterized in that after the wastewater in the step (5) is adjusted in pH by the adjusting tank, an oxidant is added and enters the reaction tank to react under the conditions of 100-140 ℃ and 0.2-0.5MPa to remove high concentration COD.

6. A coking wastewater advanced treatment and reclaimed water recycling system comprises:

preheating and decomposing the coking wastewater, pumping the coking wastewater into an ammonia still, evaporating ammonia by steam in the ammonia still, and condensing or absorbing by sulfuric acid to obtain crude concentrated ammonia water or ammonium sulfate;

the oil separation tank is connected with the effluent of the ammonia still through a pump to remove a large amount of tar in the wastewater;

the air flotation tank is connected with the water outlet of the oil separation tank through a water pump, and the emulsified oil and the dispersed oil in the wastewater are removed by adopting an air flotation method;

the A/O biological reaction tank is connected with the water outlet of the air floatation tank through a pump, the wastewater is subjected to biochemical treatment by adopting an anaerobic-aerobic method, phenolic compounds and nitrogen-containing heterocyclic compounds are converted and degraded in an anaerobic section, and high-concentration COD in the water is degraded in an aerobic section;

the secondary sedimentation tank is connected with the effluent of the A/O biological reaction tank, sludge and water generated by the aerobic section are separated, part of the separated activated sludge is used for sludge backflow, and the rest sludge is sent to a sludge treatment system;

the deep oxidation system is connected with the effluent of the secondary sedimentation tank and is used for heating, oxidizing and degrading COD in the wastewater;

the electro-catalysis system is connected with the deep oxidation system, COD and ammonia nitrogen in the wastewater are thoroughly degraded by an electrochemical means, and the electrolyzed effluent is recycled.

Background

Coking wastewater is mainly derived from the production and processing processes of steel enterprises, has complex water quality and components, contains a large amount of refractory organic matters such as aromatics and heterocycles and inorganic pollutants such as ammonia nitrogen, cyanides and sulfides, and poses serious threat to water environment safety. Meanwhile, the coking wastewater has the hazards of difficult degradability, carcinogenicity and the like. In recent years, with the process reconstruction of domestic iron and steel enterprises and the enhancement of energy-saving and environment-friendly consciousness of people, a large amount of coking wastewater is generated.

In order to realize zero discharge of the coking wastewater, most enterprises select to increase advanced treatment after secondary treatment of the coking wastewater so as to meet the standard requirement for reclaimed water recycling, and common advanced treatment technologies comprise an adsorption technology, an advanced oxidation technology, a biological treatment method and the like. And some methods in practical industrial application have poor implementation effect and have certain influence on water quality. The invention aims at the advanced treatment and reclaimed water recycling of coking wastewater in the steel industry and mainly solves the problems of COD (chemical oxygen demand), total nitrogen and reclaimed water recycling which are difficult to remove in the coking wastewater.

Disclosure of Invention

The invention aims to provide a method and a system for advanced treatment and reclaimed water recycling of coking wastewater.

According to a first aspect of the invention, a coking wastewater advanced treatment and reclaimed water recycling system method is provided, which comprises the following steps:

(1) preheating and decomposing the coking wastewater, pumping the coking wastewater into an ammonia still, evaporating ammonia through steam in the ammonia still, and condensing or absorbing sulfuric acid to obtain crude concentrated ammonia water or ammonium sulfate;

(2) the wastewater enters an oil separation tank to remove heavy oil after ammonia evaporation treatment, then is subjected to pressurized air flotation treatment in an air flotation tank to remove emulsified oil and dispersed oil in water, and the effluent after oil removal enters the next procedure for biochemical treatment after oxygen removal treatment;

(3) after oil removal and oxygen removal, the effluent is treated by an A/O biochemical system to degrade phenolic compounds, nitrogen-containing heterocyclic compounds and COD in the water, and the effluent enters the next procedure;

(4) the effluent of the A/O biochemical system enters a secondary sedimentation tank for sludge-water separation, part of the activated sludge is used for sludge backflow, and the rest sludge is sent to a sludge treatment system;

(5) after biochemical reaction, the effluent enters an advanced oxidation system for advanced treatment, the wastewater is pretreated by acid adjustment and is treated by heating catalytic oxidation, and the effluent enters the next procedure after fine adjustment;

(6) the effluent of the deep oxidation system enters an electrolytic barrel of an electro-catalytic system, and a high oxygen evolution potential close to a diamond film electrode is generated by an anode, so that ammonia nitrogen and organic matters in sewage are thoroughly removed, the effluent is ensured to stably meet the direct discharge standard, and the effluent is recycled after reaction.

Preferably, the process combining negative pressure stripping deamination and ammonia gas jet absorption is adopted in the step (1), the ammonia still adopts a guide float valve tower, the pH of inlet water of the ammonia still is 8-9, the temperature of steam at the top of the ammonia still is 90-103 ℃, and the ammonia nitrogen removal efficiency can reach 95%. The conventional ammonia distillation process is to boil and remove ammonia-containing nitrogen water by using high temperature in a tower, condense ammonia vapor by using a condenser, recover dilute ammonia water, and control reflux ratio to reach the required ammonia water concentration. Therefore, the steam consumption is large (120-. The invention adopts the process of combining negative pressure stripping deamination and ammonia gas jet absorption, and has the following technical advantages: low energy consumption, high ammonia nitrogen removal rate, low purity of recovered substances, low material requirement, long service life and difficult scaling.

The steel coking sewage contains various grease components, excessive oil can influence the effect of subsequent biochemical treatment, and grease removal becomes the necessity of steel coking sewage treatment. The invention adopts the combination of the oil separation tank and the air floatation method as the best method for removing grease, and has the functions of removing oil in the grease, recycling the oil and playing a role of pre-aeration. In the step (2), the air flotation tank adopts a pressurized dissolved air flotation method, air is used as an air source, the efficiency of removing suspended matters and the efficiency of removing oil can reach 80 percent, and 10 to 35 percent of COD can be removed.

And (3) performing biochemical treatment by adopting an anaerobic-aerobic method, wherein phenolic compounds and nitrogen-containing heterocyclic compounds are subjected to conversion and degradation in an anaerobic section, and high-concentration COD in water is subjected to degradation in an aerobic section. The pretreated wastewater enters an A/O pool, firstly enters the A pool, is mixed with an internal flow mixed liquid and return sludge, and is kept in a mixed state under the action of air stirring, so that the wastewater is fully contacted with activated sludge; the effluent enters an O tank, mainly performs degradation and nitrification of organic matters, and adjusts aeration quantity according to process requirements to ensure that the mixed solution is always in an aerobic state with DO being more than 2.0 mg/L; after the aerobic nitrification of the wastewater, the mixed liquor at the end part is discharged to the tank A through the internal reflux pump, the rest mixed liquor flows into the secondary sedimentation tank, partial sludge in the secondary sedimentation tank is pumped back to the tank A through the external reflux pump, and the rest activated sludge is discharged.

Preferably, after the pH of the wastewater in the step (5) is adjusted by the adjusting tank, an oxidant is added, and the wastewater enters the reaction tank to react at the temperature of 100-140 ℃ and under the pressure of 0.2-0.5MPa, so as to remove high-concentration COD.

According to a second aspect of the present invention, there is provided a system (or apparatus) for advanced treatment and reuse of reclaimed water from coking wastewater, comprising:

preheating and decomposing the coking wastewater, pumping the coking wastewater into an ammonia still, evaporating ammonia by steam in the ammonia still, and condensing or absorbing by sulfuric acid to obtain crude concentrated ammonia water or ammonium sulfate;

the oil separation tank is connected with the effluent of the ammonia still through a pump to remove a large amount of tar in the wastewater;

the air flotation tank is connected with the water outlet of the oil separation tank through a water pump, and the emulsified oil and the dispersed oil in the wastewater are removed by adopting an air flotation method;

the A/O biological reaction tank is connected with the water outlet of the air floatation tank through a pump, the wastewater is subjected to biochemical treatment by adopting an anaerobic-aerobic method, phenolic compounds and nitrogen-containing heterocyclic compounds are converted and degraded in an anaerobic section, and high-concentration COD in the water is degraded in an aerobic section;

the secondary sedimentation tank is connected with the effluent of the A/O biological reaction tank, sludge and water generated by the aerobic section are separated, part of the separated activated sludge is used for sludge backflow, and the rest sludge is sent to a sludge treatment system;

the deep oxidation system is connected with the effluent of the secondary sedimentation tank and is used for heating, oxidizing and degrading COD in the wastewater;

the electro-catalysis system is connected with the deep oxidation system, COD and ammonia nitrogen in the wastewater are thoroughly degraded by an electrochemical means, and the electrolyzed effluent is recycled.

Preferably, the anaerobic section of the A/O biochemical pool can adopt a filler biomembrane method to mainly remove phenol and cyanogen in the wastewater, and the removal rate can reach 96.5-99.8%; the aeration of the aerobic section adopts a microporous aerator, which mainly removes high-concentration COD and ammonia nitrogen, and the removal rates can respectively reach 70-80 percent and 87.5-98 percent.

Under the specific condition, the deep oxidation system (FYSO) comprises a preheater, an adjusting tank, a reaction tank and a gas-liquid separator, waste water enters the adjusting tank to adjust the pH value and add an oxidant after being preheated by the preheater, enters the reaction tank to react under the heating condition to remove high-concentration COD, and the reaction tank can adopt a multi-tank series connection or parallel connection mode. And the effluent of the reaction tank is subjected to heat exchange with the wastewater before advanced treatment through a preheater and then enters the electro-catalytic system. The steam generated by the reaction tank is cooled by the gas-liquid separator, and then the liquid also enters the preheater. Compared with the existing electro-Fenton oxidation process, the heating deep oxidation system adopted by the invention can degrade high-concentration COD in the wastewater, and does not generate iron mud; and the waste heat of the waste water can be recycled, so that the energy consumption is reduced.

The electrocatalysis system of the invention adopts an EP-Kaisen electrochemical treatment system. The core equipment of the EP-Kaisen electrochemical treatment system is an electrolytic barrel. The electrolytic barrel mainly comprises a water inlet barrel and a reaction barrel, wherein the water inlet barrel and the reaction barrel are separated by a partition plate, a water inlet is formed in the side wall of the water inlet barrel, and a gas outlet is formed in the top of the water inlet barrel. A plurality of pairs of cathode and anode cylinders are arranged on the partition board at intervals, each cathode cylinder is sleeved on the periphery of one anode cylinder, the anode cylinders and the cathode cylinders are made of water-permeable materials, wastewater in the water inlet cylinder flows in through the side end of the anode cylinder and flows out through a water outlet arranged at the top of the reaction barrel after electrolytic reaction, and a water outlet is arranged at the bottom of the reaction barrel. The electrocatalysis system with the unique electrode combination structure is adopted, a high oxygen evolution potential close to a diamond film electrode is generated by the anode, ammonia nitrogen and organic matters in sewage are thoroughly removed, and discharged water is discharged after reaction.

The method and the system for the advanced treatment and the reclaimed water recycling of the coking wastewater can recover products such as concentrated ammonia water or ammonium sulfate and the like to supply the products for production, can efficiently remove phenol cyanogen, COD and ammonia nitrogen in the wastewater, greatly reduce the sludge yield, energy consumption and operation cost, and have no secondary pollution to the environment.

Drawings

FIG. 1 is a general process flow diagram of a coking wastewater advanced treatment and reclaimed water reuse system according to the invention.

FIG. 2 is a process flow diagram of a biochemical treatment unit according to the present invention.

Fig. 3 is a flow chart of the deep oxidation process of the present invention.

FIG. 4 is a schematic view of an electrolytic tank structure of an EP-Kaisen electrocatalytic system in the present invention.

FIG. 5 is a schematic diagram of the electrolytic tank shown in FIG. 4 in a side view.

Detailed Description

The invention is further explained below with reference to the drawings and examples.

Referring to fig. 1, the system (device) for advanced treatment of coking wastewater and reclaimed water reuse mainly comprises a pretreatment unit, a biochemical treatment unit and an advanced treatment unit. The pretreatment unit comprises an ammonia still 1, an oil separation tank 2 and an air floatation tank 3 which are connected in sequence; the biochemical treatment unit comprises an A/O biological reaction tank 4 and a secondary sedimentation tank 5; the advanced treatment unit comprises an advanced oxidation system 6 and an electrocatalytic system 7. All the devices are connected in sequence through pipelines, pumps and the like according to the pressure difference.

The coking wastewater enters an ammonia still 1 through a water pump after being preheated and decomposed, ammonia still treatment is carried out in the tower, and ammonia-containing steam is condensed or absorbed by sulfuric acid to obtain crude concentrated ammonia water and ammonium sulfate. The process adopts a process combining negative pressure stripping deamination and ammonia jet absorption, the ammonia still 1 adopts a guide float valve tower, the pH of inlet water of the ammonia still 1 is 8-9, the temperature of steam at the top of the tower is 90-103 ℃, and the ammonia nitrogen removal efficiency is 95%.

The wastewater is subjected to ammonia distillation in an ammonia distillation tower 1 and then is subjected to oil removal treatment in an oil separation tank 2 and an air flotation tank 3 to ensure the subsequent treatment effect. The oil separation tank 2 selects a horizontal flow type oil separation tank to remove tar on the upper layer of the wastewater, and the air flotation tank 3 carries out pressurized air flotation by laying jet flow air flotation equipment, so that emulsified oil and dispersed oil in the wastewater are removed. And a deoxidizing device is arranged behind the air floatation tank 3 to reduce the interference of air floatation on the anaerobic effect.

The effluent of the air flotation tank 3 enters an A/O biological reaction tank 4 after being subjected to deoxidization treatment, referring to fig. 2, the A/O biological reaction tank 4 comprises an anaerobic tank (A tank) and an aerobic tank (O tank), and a biofilm method with filler is adopted in the anaerobic tank; the aerobic tank is provided with a microporous aerator. Phenolic compounds and nitrogen-containing heterocyclic compounds in the sewage are firstly converted and degraded in the A pool of the A/O biological reaction pool 4, and then COD degradation is carried out in the O pool, so that most organic matters are removed. Under the specific condition, the pretreated wastewater enters an A/O pool, firstly enters the A pool, is mixed with an internal flow mixed liquid and return sludge, and keeps a mixed state under the action of air stirring, so that the wastewater is fully contacted with activated sludge; the effluent enters an O tank, mainly performs degradation and nitrification of organic matters, and adjusts aeration quantity according to process requirements to ensure that the mixed solution is always in an aerobic state with DO being more than 2.0 mg/L; after the aerobic nitrification of the wastewater, the mixed liquor at the end part is discharged to the tank A through the internal reflux pump, and the rest mixed liquor flows into the secondary sedimentation tank 5.

The secondary sedimentation tank 5 is a circular radial flow sedimentation tank, and water is fed from the middle and discharged from the periphery. Supernatant fluid flows to a deep oxidation system 6 through a water collecting tank, partial sludge in a secondary sedimentation tank 5 is pumped back to a tank A through an external reflux pump, and residual sludge enters a sludge treatment system 8 for dehydration and incineration treatment.

Referring to fig. 3, the deep oxidation system (FYSO) includes a preheater 61, an adjusting tank 62, a reaction tank 63, and a gas-liquid separator 64, wherein the wastewater is preheated by the preheater 61, enters the adjusting tank 62 to adjust pH, and is added with an oxidant (such as hydrogen peroxide), enters the reaction tank 63 to react at 140 ℃ and 0.3MPa, so as to remove high-concentration COD, and the reaction tank 63 may be connected in series or in parallel with multiple tanks. The effluent of the reaction tank 63 exchanges heat with the wastewater before advanced treatment through the preheater 61 and enters the electro-catalytic system 7. The steam generated from the reaction tank 63 is cooled by the gas-liquid separator 64 and the liquid is also introduced into the preheater 61. Compared with the existing electro-Fenton oxidation process, the heating deep oxidation system adopted by the invention can degrade high-concentration COD in the wastewater, and does not generate iron mud; and the waste heat of the waste water can be recycled, so that the energy consumption is reduced.

The effluent of the deep oxidation system is pumped into an electro-catalytic system 7, and the electro-catalytic system adopts an EP-Kaisen electrochemical treatment system. Referring to fig. 4-5, the core device of the EP-kesen electrochemical treatment system is an electrolytic tank. The electrolytic tank mainly comprises a water inlet tank 71 and a reaction tank 72 which are separated by a partition plate 75, a water inlet 73 is arranged on the side wall of the water inlet tank 71, and an air outlet 74 is arranged on the top of the water inlet tank. A plurality of pairs of cathode and anode cylinders are arranged on the partition plate 75 at intervals, each cathode cylinder 76 is sleeved on the periphery of one anode cylinder 77, the anode cylinders 77 and the cathode cylinders 76 are made of water-permeable materials, wastewater in the water inlet barrel 71 flows in through the side end of the anode cylinder 77 and flows out through a water outlet 79 arranged at the top of the reaction barrel 72 after electrolytic reaction, and a water outlet 78 is arranged at the bottom of the reaction barrel 72. The electrocatalysis system with the unique electrode combination structure is adopted, a high oxygen evolution potential close to a diamond film electrode is generated by the anode, ammonia nitrogen and organic matters in sewage are thoroughly removed, and discharged water is discharged after reaction.

The system is successfully used for treating the coking wastewater generated in the coking plant production of the Laiwu division of the Shangang steel, and has high COD (chemical oxygen demand), ammonia nitrogen content, high alkalinity and high tar content, so in order to reduce the medicament consumption and effectively utilize the wastewater, the treatment system for treating the coking wastewater is adopted to treat the ammonia nitrogen and the tar in the early stage and then adopt biochemical and advanced treatment technologies to ensure that the COD removal rate can reach 98 percent and the ammonia nitrogen removal rate is 100 percent, and the COD, the chromaticity and the ammonia nitrogen can reach the standard of direct discharge.