CN109942148B - Coal chemical industry sewage zero-discharge treatment and salt separation crystallization system and method with electrolytic oxidation - Google Patents
Coal chemical industry sewage zero-discharge treatment and salt separation crystallization system and method with electrolytic oxidation Download PDFInfo
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- Separation Using Semi-Permeable Membranes (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Abstract
The invention provides a coal chemical industry sewage zero-discharge treatment and salt separation crystallization system with electrolytic oxidation and a method thereof, wherein the system comprises a recycling unit and a membrane concentration unit which are connected in sequence; the membrane concentration unit comprises a pre-concentration device, an electrolytic oxidation device, a nanofiltration device and a nanofiltration water production reverse osmosis device which are connected in sequence; the electrolytic oxidation device comprises an electrode with the working voltage of 4.3V. On one hand, the electrolytic oxidation device is arranged in the middle of the membrane concentration unit, the concentrated water entering the nanofiltration device of the salt separation crystallization unit is subjected to electrolytic oxidation, and the electrolytic oxidation produced water for salt separation is obtained by adjusting proper electrolytic oxidation working parameters, so that a water quality foundation is provided for subsequent salt separation. On the other hand, the invention provides a whole set of coal chemical industry sewage zero discharge system, aiming at the coal chemical industry sewage with poorer water quality condition, all units in the existing sewage treatment system are adjusted from the whole flow angle, and various pollution influence factors are properly treated, so that the connection between the upstream unit and the downstream unit is more compact.
Description
Technical Field
The invention belongs to the field of sewage treatment, relates to a zero-discharge salt separation treatment system and method for sewage, and particularly relates to a zero-discharge treatment and salt separation crystallization system and method for coal chemical industry sewage with electrolytic oxidation.
Background
In the modern coal gasification process, coal gasification wastewater is one of the wastewater with the largest treatment difficulty, and the wastewater still has the characteristics of oil content, high ammonia nitrogen, high phenol, high COD, complex pollution components, poor biodegradability, high biological toxicity and the like after phenol-ammonia recovery.
CN103382072A provides a coal gasification wastewater treatment method, which comprises the steps of sequentially carrying out pretreatment and biochemical treatment on coal gasification wastewater to be treated, wherein the treatment method further comprises the step of carrying out advanced treatment on the coal gasification wastewater after the biochemical treatment, the advanced treatment method comprises the steps of firstly contacting the coal gasification wastewater after the biochemical treatment with ozone, and further carrying out aerobic biological treatment on the contacted wastewater.
CN101503267B provides a coal chemical industry wastewater treatment method, and relates to a chemical industry wastewater treatment method. Aiming at the problems of poor quality of effluent and high operation cost in the existing coal chemical wastewater treatment process. The method comprises the steps of pretreating coal chemical wastewater to be treated, and then performing hydrolytic acidification treatment, external circulation anaerobic treatment, anaerobic sedimentation treatment, hydrolysis acidification regulation treatment, contact oxidation treatment, sedimentation treatment, A/O treatment, sedimentation treatment, deamination treatment, coagulating sedimentation treatment and biological aerated filter treatment.
In the engineering practice of coal gasification wastewater zero-discharge treatment which is put into operation, the biochemical treatment, recycling treatment and membrane concentration processes of the coal gasification wastewater are mature and stable, but the evaporation crystallization product at the tail end can only be mixed salt basically, industrial-grade crystallization salt separation is difficult to obtain, and more problems exist in the operation process. Therefore, there is a need for improvement of the existing sewage treatment system to solve the above technical problems.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a coal chemical industry sewage zero-discharge treatment and salt separation crystallization system and method with electrolytic oxidation.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a zero-emission salt separation treatment system for coal chemical industry sewage, which comprises a recycling unit and a membrane concentration unit which are connected in sequence.
The membrane concentration unit comprises a pre-concentration device, an electrolytic oxidation device, a nanofiltration device and a nanofiltration water production reverse osmosis device which are connected in sequence.
The electrolytic oxidation device comprises an electrode with the working voltage of 4.3V.
On one hand, the electrolytic oxidation device is arranged in the middle of the membrane concentration unit working section to perform electrolytic oxidation on the reverse osmosis concentrated water entering the salt separation crystallization unit, and the electrolytic oxidation produced water suitable for salt separation crystallization is obtained by adjusting the working parameters of the electrolytic oxidation device, so that a water quality foundation is provided for subsequent salt separation crystallization. On the other hand, the invention provides a full-flow coal chemical industry sewage zero-emission salt separation system, aiming at the coal chemical industry sewage with poor water quality condition, all units in the existing sewage treatment system are adjusted from the full-flow angle, and various pollution influence factors are properly treated, so that the connection between the upstream unit and the downstream unit is tighter.
As the preferable technical scheme of the invention, the recycling unit is used for recycling fresh water in the coal chemical industry sewage.
Preferably, the recycling unit comprises a biochemical regulation water tank, a recycling section clarification tank, a recycling section multi-medium filtering device, a recycling section ultrafiltration device and a recycling section reverse osmosis device which are connected in sequence.
As a preferable technical scheme of the invention, the membrane concentration unit is used for carrying out membrane concentration treatment on the concentrated water generated by the recovery unit to obtain the recycled fresh water and the concentrated water which can be used for salt separation crystallization.
Preferably, the membrane concentration unit further comprises a chromaticity detection device for detecting the chromaticity of the effluent of the electrolytic oxidation device.
Preferably, the membrane concentration unit further comprises a control device electrically connected with the chromaticity detection device, and the control device is used for receiving feedback data of the chromaticity detection device and adjusting working parameters of the electrolytic oxidation device.
The invention adds a chroma detection device and a control device in the concentration unit, establishes a corresponding relation between chroma and the quality index of the water produced by electrolytic oxidation, and measures COD in the water produced by electrolytic oxidation by detecting the chroma of the water produced by electrolytic oxidation and comparing the chroma with the preset chromaCrContent and NH3The content of N is regulated by the control device, and the working parameters of the electrolytic oxidation device are regulated, so that the manual detection link is omitted. However, it is understood by those skilled in the art that the color and COD areCrThe invention only compares the actually measured chroma with the water quality chroma when the water quality chroma reaches the standard, if the actually measured chroma does not reach the standard chroma, the control device controls the technological parameters of the electrolytic oxidation device, such as prolonging the electrolytic time or adding large current, and the like, and if the actually measured chroma reaches the standard chroma, the electrolytic produced water is discharged to the next-stage technology for salt separation and crystallization treatment.
The specific structure and model parameters of the chroma detection device are not particularly limited, and real-time detection devices which are not disclosed in the prior art and can be used for detecting the chroma of the sewage can be used in the application, for example, a commercially available ET7240 chroma determinator or SDY-1Z sewage chroma meter and the like can be adopted in the application, and the true chroma value can be displayed in a digital manner in real time.
Preferably, the pre-concentration device comprises a concentrated water regulating water tank, a concentration section clarification tank, a concentration section multi-medium filtering device, a sodium bed, a weak acid cation bed, a decarburization device, a concentration section ultrafiltration device and a seawater reverse osmosis device which are connected in sequence.
Specifically, the invention provides an exemplary membrane concentration unit treatment process, concentrated water generated by a recycling unit sequentially passes through the following process routes in the membrane concentration unit provided by the invention:
(1) the effluent of the concentrated water regulating water tank enters a concentration section clarification tank, sodium hydroxide, magnesium oxide, polyferric chloride and polyacrylamide are sequentially added, the precipitate is clarified, and the supernatant is neutralized by hydrochloric acid and then is sent to a clear water tank;
(2) the sewage treated by the clarification tank of the concentration section enters a multi-medium filtering device of the concentration section filled with quartz sand and charcoal for preliminary filtering, the filtered sewage sequentially enters a sodium bed, a weak acid cation bed and a decarbonization device to further reduce suspended matters and hardness, and the treated fresh water side produced water enters an intermediate water tank;
(3) pumping the water in the middle water tank into a concentration section ultrafiltration device by using a pump for deep filtration;
(4) the ultrafiltration produced water is pumped into a security filter, is pressurized by a high-pressure pump and then enters a seawater reverse osmosis device for desalination treatment, the seawater reverse osmosis adopts high-flow circulation of concentrated water, the recovery rate of the reverse osmosis is ensured to be 66%, the discharged concentrated water is collected by an electrolytic oxidation device, and the electrolytic oxidation device can further reduce the COD of the seawater reverse osmosis concentrated water;
(5) the sewage after electrolytic oxidation enters a nanofiltration device through a pump, the nanofiltration device adopts concentrated water circulation to ensure that the recovery rate of nanofiltration is more than 80 percent, nanofiltration separation is carried out to obtain nanofiltration concentrated water and nanofiltration produced water, wherein the nanofiltration concentrated water enters a sodium sulfate crystallization device;
(6) and (2) conveying nanofiltration product water obtained by nanofiltration separation into a security filter through a lifting pump, pressurizing the nanofiltration product water by a high-pressure pump, then conveying the nanofiltration product water into a nanofiltration product water reverse osmosis device for further desalting, wherein the reverse osmosis adopts concentrated water circulation, the recovery rate reaches 75%, separating the nanofiltration product water after reverse osmosis desalting to obtain reverse osmosis concentrated water and reverse osmosis product water, and conveying the reverse osmosis product water into a sodium chloride crystallization device for evaporation crystallization to obtain sodium chloride crystals.
As a preferable technical scheme, the system also comprises a biochemical treatment unit connected with the inlet of the recycling unit, and the biochemical treatment unit is used for performing biochemical treatment on the coal chemical industry sewage to remove organic matters, COD (chemical oxygen demand) and ammonia nitrogen in the coal chemical industry sewage.
Preferably, the biochemical treatment unit comprises a regulating tank, a nitrogen air flotation tank, a hydrolysis acidification tank, a primary A/O biochemical tank, a secondary A/O biochemical tank, an air flotation tank, an ozone contact tower, an aeration biological filter and an activated carbon filter device which are connected in sequence.
As a preferable technical scheme of the invention, the system further comprises a salt separation crystallization unit connected with an outlet of the membrane concentration unit, wherein the salt separation crystallization unit is used for carrying out salt separation crystallization on the concentrated water containing sodium sulfate and sodium chloride produced by the membrane concentration unit to obtain sodium sulfate crystals and sodium chloride crystals.
Preferably, the salt separation crystallization unit comprises a sodium sulfate crystallization device and a sodium chloride crystallization device, the sodium sulfate crystallization device is connected with a concentrated water outlet of the nanofiltration device, and the sodium chloride crystallization device is connected with a concentrated water outlet of the nanofiltration water production reverse osmosis device.
As a preferable technical scheme of the invention, the sodium sulfate crystallization device comprises a thermal crystallizer and a freezing crystallizer which are connected in sequence. The water produced by electrolytic oxidation is heated and evaporated to concentrate the mother liquor to a certain concentration, then partial mother liquor is sent to a refrigerating device, sodium sulfate decahydrate (mirabilite) is separated out because the temperature is reduced to about minus 5 ℃, and the mother liquor with separated crystal is sent to a centrifuge for separation to obtain the mirabilite.
The thermal crystallizer is provided with a feed inlet, a solid discharge port, a liquid discharge port and a feed back port.
The freezing crystallizer is provided with a feed inlet, a mother liquid discharge port and a solid discharge port.
The feed inlet of the thermal crystallizer is connected with the concentrated water outlet of the nanofiltration device, the liquid discharge port of the thermal crystallizer is connected with the feed inlet of the freezing crystallizer, and the solid discharge port of the freezing crystallizer is connected with the feed back port of the thermal crystallizer.
As a preferable technical scheme of the invention, the sodium chloride crystallization device comprises a forced circulation evaporative crystallizer.
The forced circulation evaporation crystallizer is provided with a discharge port and a liquid feed port, and the liquid feed port is connected with a concentrated water outlet of the nanofiltration water production reverse osmosis device.
Preferably, the forced circulation evaporative crystallizer is further provided with a mother liquor feeding port, and the mother liquor feeding port is connected with a mother liquor discharging port of the freezing crystallizer.
In a second aspect, the present invention provides a zero emission treatment method for coal chemical industry wastewater, the method being performed in the system of the first aspect, the method comprising:
sequentially passing coal chemical industry sewage through a recycling unit and a pre-concentration device to obtain reverse osmosis concentrated water;
(II) oxidizing the reverse osmosis concentrated water by an electrolytic oxidation device to obtain electrolytic oxidation water;
and (III) discharging the electrolyzed oxidation produced water, and sequentially passing through a nanofiltration device and a nanofiltration produced water reverse osmosis device to obtain concentrated water for salt separation crystallization.
As a preferred technical scheme of the invention, COD in the reverse osmosis concentrated water in the step (I)CrThe content is 500-700 mg/L, for example, 500mg/L, 520mg/L, 540mg/L, 560mg/L, 580mg/L, 600mg/L, 620mg/L, 640mg/L, 680mg/L or 700 mg/L.
Preferably, the electrolysis time of the electrolytic oxidation device in the step (II) is less than or equal to 6h, and can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6 h.
Preferably, the electrolytic current of the electrolytic oxidation device is 500-800A, for example, 500A, 520A, 540A, 560A, 580A, 600A, 620A, 640A, 680A, 700A, 720A, 740A, 760A, 780A or 800A.
Preferably, COD in the electrolyzed oxidizing water is generatedCrIs 300-340 mg/L, for example, 300mg/L, 305mg/L, 310mg/L, 315mg/L, 320mg/L, 325mg/L, 330mg/L, 335mg/L or 340 mg/L.
And (III) carrying out nanofiltration on the electrolyzed oxidation water product to obtain nanofiltration concentrated water and nanofiltration water product, and carrying out thermal freezing crystallization on the nanofiltration concentrated water to separate out sodium sulfate crystals.
Preferably, the nanofiltration water product is subjected to nanofiltration water product reverse osmosis to obtain reverse osmosis concentrated water and reverse osmosis water product.
Preferably, the reverse osmosis concentrated water is evaporated to crystallize sodium chloride crystals.
Preferably, the reverse osmosis produced water is collected and recycled.
As the preferable technical scheme of the invention, the content of sodium sulfate in the sodium sulfate crystal is more than or equal to 97.0 percent, the content of water is less than or equal to 1.0 percent, the content of chloride is less than or equal to 0.9 percent, and the content of calcium and magnesium ions is less than or equal to 0.4 percent.
Preferably, the content of sodium chloride in the sodium chloride crystal is more than or equal to 92 percent, the content of water is less than or equal to 6.0 percent, the content of sulfate ions is less than or equal to 1.0 percent, and the content of calcium and magnesium ions is less than or equal to 0.6 percent.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
1. the electrolytic oxidation device is arranged at the tail end of the working section of the membrane concentration unit, the reverse osmosis concentrated water entering the salt separation crystallization unit is subjected to electrolytic oxidation, and the electrolytic oxidation produced water suitable for salt separation crystallization is obtained by adjusting the working parameters of the electrolytic oxidation device, so that a water quality foundation is provided for subsequent salt separation crystallization.
2. The invention provides a set of full-flow coal chemical industry sewage zero discharge system, aiming at coal chemical industry sewage with poor water quality condition, all units in the existing sewage treatment system are adjusted from the full-flow angle, and various pollution influence factors are properly treated, so that the connection between an upstream unit and a downstream unit is more compact.
3. The invention adds a chroma detection device and a control device in the concentration unit, establishes a corresponding relation between chroma and the water quality index of the water produced by electrolytic oxidation, detects the chroma of the water produced by electrolytic oxidation and compares the chroma with the water quality chroma when reaching the standard for useMeasurement of COD in water produced by electrolytic oxidationCrContent and NH3And the content of N is reduced, and the working parameters of the electrolytic oxidation device are adjusted through the control device, so that the manual detection link is omitted.
Drawings
FIG. 1 is a process flow diagram of a coal chemical industry wastewater zero-emission treatment and salt separation crystallization system with electrolytic oxidation according to an embodiment of the present invention;
FIG. 2 is a process flow diagram of a full-process coal chemical wastewater zero-discharge treatment and salt separation crystallization system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a thermal freezing crystallization process according to an embodiment of the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
In a specific embodiment, the invention provides a coal chemical industry sewage zero-emission treatment and salt separation crystallization system with electrolytic oxidation, which comprises units and devices shown in a process flow diagram of fig. 1, and specifically comprises a reuse unit and a membrane concentration unit which are connected in sequence, wherein the membrane concentration unit comprises a pre-concentration device, an electrolytic oxidation device, a nanofiltration device and a nanofiltration water production reverse osmosis device which are connected in sequence; the electrolytic oxidation device comprises an electrode with the working voltage of 4.3 v.
In another embodiment, the invention provides a zero-emission and salt separation treatment system for full-flow coal chemical wastewater, which comprises units and devices shown in the process flow diagram of fig. 2, and specifically comprises a biochemical treatment unit, a recycling unit, a membrane concentration unit and a salt separation crystallization unit which are connected in sequence.
The biochemical treatment unit comprises a regulating tank, a nitrogen air flotation tank, a hydrolysis acidification tank, a primary A/O biochemical tank, a secondary A/O biochemical tank, an air flotation tank, an ozone contact tower, an aeration biological filter and an active carbon filter device which are connected in sequence.
The recycling unit comprises a biochemical regulating water tank, a recycling section clarification tank, a recycling section multi-medium filtering device, a recycling section ultrafiltration device and a recycling section reverse osmosis device which are connected in sequence.
The membrane concentration unit comprises a pre-concentration device, an electrolytic oxidation device, a nanofiltration device and a nanofiltration water production reverse osmosis device which are connected in sequence. The pre-concentration device comprises a concentrated water regulating water tank, a concentration section clarification tank, a recycling section multi-medium filtering device, a sodium bed, a weak acid cation bed, a decarburization device, a concentration section ultrafiltration device and a seawater reverse osmosis device which are connected in sequence. The membrane concentration unit also comprises a chromaticity detection device for detecting the chromaticity of the effluent of the electrolytic oxidation device; the membrane concentration unit further comprises a control device electrically connected with the chromaticity detection device, and the control device is used for receiving feedback data of the chromaticity detection device and adjusting working parameters of the electrolytic oxidation device.
The salt separation crystallization unit comprises a sodium sulfate crystallization device and a sodium chloride crystallization device, the sodium sulfate crystallization device is connected with a concentrated water outlet of the nanofiltration device, and the sodium chloride crystallization device is connected with a concentrated water outlet of the nanofiltration water production reverse osmosis device. Fresh water produced by the sodium sulfate crystallization device and the sodium chloride crystallization device enters a reuse water pool.
The sodium sulfate crystallization device comprises devices shown in a heat method freezing crystallization process route diagram of figure 3, and specifically comprises a heat method crystallizer and a freezing crystallizer which are connected in sequence; wherein, the thermal crystallizer is provided with a feed inlet, a solid discharge port, a liquid discharge port and a feed back port; the freezing crystallizer is provided with a feed inlet, a mother liquid discharge port and a solid discharge port. The feed inlet of the thermal crystallizer is connected with the concentrated water outlet of the nanofiltration device, the liquid discharge port of the thermal crystallizer is connected with the feed inlet of the freezing crystallizer, and the solid discharge port of the freezing crystallizer is connected with the feed back port of the thermal crystallizer.
The sodium chloride crystallization device comprises a forced circulation evaporation crystallizer; the forced circulation evaporation crystallizer is provided with a discharge port and a liquid feed port, and the liquid feed port is connected with a concentrated water outlet of the nanofiltration water production reverse osmosis device; the forced circulation evaporation crystallizer is also provided with a mother liquor feeding port, and the mother liquor feeding port is connected with a mother liquor discharging port of the freezing crystallizer.
Example 1
The treatment system provided by the specific embodiment is adopted to carry out zero emission treatment on the coal chemical industry sewage, and the method comprises the following steps:
sequentially passing coal chemical industry sewage through a recycling unit and a pre-concentration device to obtain reverse osmosis concentrated water;
(II) oxidizing the reverse osmosis concentrated water by an electrolytic oxidation device to obtain electrolytic oxidation water;
and (III) discharging the electrolyzed oxidation produced water, and sequentially passing through a nanofiltration device and a nanofiltration produced water reverse osmosis device to obtain concentrated water for salt separation crystallization. Wherein, the water produced by electrolytic oxidation is nanofiltered to obtain nanofiltration concentrated water and nanofiltration water, the nanofiltration concentrated water is frozen and crystallized by a thermal method to separate out sodium sulfate crystals, the nanofiltration water is subjected to nanofiltration water production and reverse osmosis to obtain reverse osmosis concentrated water and reverse osmosis water, and the reverse osmosis concentrated water is evaporated and crystallized to separate out sodium chloride crystals; and collecting reverse osmosis produced water for reuse.
And (II) the electrolysis time of the electrolytic oxidation device in the step (II) is 2h, and the electrolysis current is 600A.
Measuring COD in the water produced by electrolytic oxidationCrContent and NH3the-N content is shown in Table 1.
Example 2
The difference between this example and example 1 is that the electrolytic oxidation apparatus described in step (II) has an electrolysis time of 2 hours and an electrolysis current of 703A, and the rest of the procedure is the same as example 1.
Measuring COD in the water produced by electrolytic oxidationCrContent and NH3the-N content is shown in Table 1.
Example 3
The difference between this example and example 1 is that the electrolytic oxidation apparatus described in step (II) has an electrolysis time of 4 hours and an electrolysis current of 600A, and the rest of the steps are the same as those of example 1.
Measuring COD in the water produced by electrolytic oxidationCrContent and NH3the-N content is shown in Table 1.
Example 4
The difference between this example and example 1 is that the electrolytic oxidation apparatus described in step (II) has an electrolysis time of 4 hours and an electrolysis current of 703A, and the rest of the procedure is the same as example 1.
Measuring COD in the water produced by electrolytic oxidationCrContent and NH3the-N content is shown in Table 1.
Example 5
The difference between the present example and example 1 is that the electrolytic oxidation apparatus described in step (II) has an electrolysis time of 6 hours and an electrolysis current of 600A, and the rest of the steps are the same as those of example 1.
Measuring COD in the water produced by electrolytic oxidationCrContent and NH3the-N content is shown in Table 1.
Example 6
The difference between this example and example 1 is that the electrolytic oxidation apparatus described in step (II) has an electrolysis time of 6 hours and an electrolysis current of 703A, and the rest of the procedure is the same as example 1.
Measuring COD in the water produced by electrolytic oxidationCrContent and NH3the-N content is shown in Table 1.
And (3) carrying out salt separation crystallization on the water produced by electrolytic oxidation to obtain sodium chloride crystals and sodium sulfate crystals, wherein the content of each component in the sodium chloride crystals is shown in table 2, and the content of each component in the sodium sulfate crystals is shown in table 3. The total recovery of crystalline salt was calculated to be 89%. Wherein, the calculation formula of the total recovery rate of the crystallized salt is as follows: (total weight of sodium sulfate crystalline salts + total weight of sodium chloride crystalline salts)/(total feed of sodium sulfate stock solution XTDS + total feed of sodium chloride stock solution XTDS)
Comparative example 1
The difference between the comparative example and the coal chemical industry sewage zero discharge system provided by the invention is that an electrolytic oxidation device is omitted. The coal chemical industry sewage sequentially passes through a recycling unit and a pre-concentration device to obtain reverse osmosis concentrated water; after being discharged, the reverse osmosis concentrated water is subjected to salt separation and crystallization sequentially by a nanofiltration device and a nanofiltration water production reverse osmosis device.
Measuring COD in the reverse osmosis concentrated waterCrContent and NH3the-N content is shown in Table 1.
And carrying out salt separation crystallization on the reverse osmosis concentrated water to obtain sodium chloride crystals and sodium sulfate crystals, wherein the total recovery rate of the crystallized salts is 80%.
TABLE 1
| Electrolysis time [ h] | CODCr[mg/L] | NH3-N[mg/L] |
| Example 1 | 482 | 0.47 |
| Example 2 | 527 | Not detected out |
| Example 3 | 421 | 0.42 |
| Example 4 | 427 | Not detected out |
| Example 5 | 301 | 0.52 |
| Example 6 | 339 | Not testedGo out |
| Comparative example 1 | 632 | 2.31 |
TABLE 2
TABLE 3
| Basic control items | Unit of | Expected value | Guaranteed value |
| Sodium sulfate (Na)2SO4) | ％ | ≥97.0 | ≥97.0 |
| Moisture content | ％ | ≤1.0 | ≤1.0 |
| Water insoluble substance | ％ | ≤0.2 | ≤0.2 |
| Calcium and magnesium (in terms of magnesium) | ％ | ≤0.4 | ≤0.4 |
| Chloride (in terms of Cl) | ％ | ≤0.9 | ≤0.9 |
| Iron (Fe) | ％ | ≤0.040 | ≤0.040 |
As can be seen from Table 1, when the same electrolysis time was controlled (examples 1 and 2, examples 3 and 4, examples 5 and 6), COD was increased with the increase of the electrolysis currentCrContent and NH3-N content is reduced; when the same electrolysis current was controlled (example 1, example 3 and example 5 or example 2, example 4 and example 6), COD was observed as the electrolysis time was extendedCrThe content is obviously reduced, but the content of NH3-N is reduced first and then increased. Therefore, after the electrolytic oxidation device is additionally arranged, the water inlet of the salt separation crystallization unit is ensured to meet the water quality requirement of concentrated water for salt separation crystallization, and a good water quality foundation is laid for subsequent salt separation crystallization.
As a result of comprehensive analysis of the total recovery rates of the crystalline salts obtained in example 6 and comparative example 1, it was found that the electrolytic oxidation apparatus was not provided, and sodium chloride and sulfuric acid were addedCOD in sodium stock solution or concentrated waterCrThe quality of the salt separation product can be ensured by increasing the discharge amount of the mother liquor of the evaporative crystallization device, namely COD in the sodium chloride stock solution and the sodium sulfate stock solutionCrThe increase of the amount of the mother liquor discharged from the evaporation crystallization device or the yield of the miscellaneous salt is increased, so that the yield of the crystallization salt is reduced, and therefore, the content of each component of the salt separation crystal obtained in the comparative example 1 can also meet the index requirements of tables 2 and 3, but the amount of the mother liquor discharged from the evaporation crystallization device needs to be increased, and finally, the yield of the crystallization salt is reduced.
Application examples
The application embodiment provides a group of pilot plant process indexes for the coal chemical industry sewage zero discharge system, and the pilot plant process indexes are as follows:
first, flow control
(1) 3 +/-0.2 m of inlet water of the biochemical treatment unit3/h。
(2) The inlet water of the recycling unit is 6 +/-0.2 m3H, wherein biochemical effluent is 3 +/-0.1 m3H, 3 plus or minus 0.1m of mixed salt water3/h。
(3) 3 +/-0.2 m of inlet water of the membrane concentration unit3/h。
(4) The sodium chloride crystallizing device and the sodium sulfate crystallizing device respectively feed water of 0.3 +/-0.1 m3/h。
Liquid level control
(1) The liquid level of the biochemical regulating tank is controlled between 1/2 and 2/3.
(2) The liquid levels of the nitrogen air flotation tank and the air flotation tank are controlled to keep the micro overflow at the slag overflow port.
(3) The liquid level of each device runs according to the self-overflow design liquid level.
(4) The low limit of each dosing box is controlled according to an alarm, and the high limit is not higher than 2/3.
(5) The liquid level (salt-blending water tank) of the concentrated brine tank of the desalter station during salt blending is at the lower edge of the overflow pipe, so that overflow is avoided (10 cubes of water are added after the liquid level of the water tank is empty every time, and sodium chloride and sodium sulfate are added according to the regulations).
(6) The liquid level of the water production tank of each device is controlled between 1/2 and 2/3 in principle.
(7) The wastewater pond is maintained at a low level.
(8) The reuse water pool keeps low liquid level, and the reuse water flows back to the system (the drainage of the biochemical treatment unit is required not to enter a reuse concentration recovery water pool).
Third, control of reflux quantity
(1) A hydrolysis acidification pool: controlling the reflux quantity of the mixed solution to control the total phenol of the inlet water to be less than 500 mg/L; the sludge reflux amount is 1Q;
(2) a first-stage A/O biochemical pool: controlling the reflux quantity of the mixed liquid to be 2-3Q; the sludge reflux amount is 1Q;
(3) a second-level A/O biochemical pool: controlling the reflux quantity of the mixed liquid to be 2-3Q; the sludge reflux amount is 1Q;
(4) a nitrogen air flotation tank and an air flotation tank: the internal reflux ratio (the flow of the dissolved gas water pump is 30-50% of the water inflow);
(5) high density: the sludge reflux amount is about 5 percent of the water inflow amount.
Fourth, membrane treatment recovery rate control
(1) Reverse osmosis at a recycling section: 50 percent;
(2) reverse osmosis of seawater: 50 percent;
(3) and (4) nanofiltration: 60% (performance assessment period 80%);
(4) reverse osmosis of nanofiltration produced water: 80 percent.
Fifth, technological parameters
1. Air floatation
(1) Gas-water ratio: the general gas flow is 10 percent of water inflow;
(2) yielding water SS: the removal rate is 50-80%.
2. First and second grade A/O
(1) pH value: 6.5-8.5;
(2) temperature: 10-40 ℃, and the optimal temperature is 20-30 ℃;
(3) primary a/O MLSS: 3000-6000mg/L, SV 30: 15-30%;
(4) secondary A/O MLSS: 2000-3000mg/L, SV 30: 15-30%;
(5) and (3) discharging water from the secondary sedimentation tank: alkalinity: about 70mg/L, total phosphorus: about 0.5 mg/L;
(6) sodium acetate is added to ensure that the C/N of the secondary A/O inlet water is as follows: 4 to 8.
3. Ozone oxidation:
(1) air flow rate of the ozone generator: 20m3/h；
(2) Concentration of the ozone on-line analyzer: 15 mg/L;
(3) when the water outlet of the ozone contact tower becomes worse or the resistance is increased, the corresponding tower needs to be backwashed in time.
4. The COD of the effluent of the activated carbon filtering device is lower than the content of the inlet; otherwise, backwashing is carried out.
5. High density
(1) Effluent turbidity: less than 5;
(2) the hardness of the effluent of the concentration section is as follows: less than 200 mg/L.
6. The turbidity of the effluent of the multi-medium filtering device is less than or equal to 25NTU, otherwise, the effluent is scrubbed.
7. Ultrafiltration
(1) The highest operating pressure: 0.25 MPa;
(2) pH of washing water: 1.0 to 12.0;
(3) ultrafiltration inlet pressure: 1 bar;
(4) the SDI of the effluent is less than 3, or the turbidity is less than 1 NTU.
8. And the differential pressure of the cartridge filter is 0.07-0.1 Mpa, otherwise, the cartridge filter is replaced.
9. When the pressure difference of each membrane is increased by 15% from the initial value, or when the water yield is decreased by 15% from the initial value, chemical cleaning is required.
10. The hardness of the effluent of the sodium bed is less than or equal to 10-20 mg/L (calculated by calcium carbonate), otherwise, the effluent is regenerated.
11. The hardness of the effluent of the weak acid cation bed is less than or equal to 5-10 mg/L (calculated by calcium carbonate), otherwise, the effluent is regenerated.
The operation parameters and the effluent quality requirements of the devices are not specific limitations on the protection scope of the invention, and are only used as an optional technical scheme for ensuring the integrity of the whole process of the zero-emission treatment process, so that technical personnel in the field need to reasonably adjust the operation parameters according to the field conditions and the quality of the treated coal chemical industry wastewater, but the operation parameters adopted by the technical personnel in the field and the zero-emission treatment system provided by the invention are matched to use, and the operation parameters and the quality of the treated coal chemical industry wastewater are also within the disclosure scope and the protection scope of the invention.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (18)
1. The coal chemical industry sewage zero-emission treatment and salt separation crystallization system with electrolytic oxidation is characterized by comprising a reuse unit and a membrane concentration unit which are connected in sequence;
the membrane concentration unit comprises a pre-concentration device, an electrolytic oxidation device, a nanofiltration device and a nanofiltration water production reverse osmosis device which are connected in sequence;
the electrolytic oxidation device comprises an electrode with the working voltage of 4.3V;
the membrane concentration unit also comprises a chromaticity detection device for detecting the chromaticity of the effluent of the electrolytic oxidation device;
the membrane concentration unit also comprises a control device electrically connected with the chromaticity detection device, and the control device is used for receiving feedback data of the chromaticity detection device and adjusting working parameters of the electrolytic oxidation device;
the pre-concentration device comprises a concentrated water regulating water tank, a concentration section clarification tank, a concentration section multi-medium filtering device, a sodium bed, a weak acid cation bed, a decarburization device, a concentration section ultrafiltration device and a seawater reverse osmosis device which are connected in sequence;
the system also comprises a biochemical treatment unit connected with the inlet of the recycling unit, wherein the biochemical treatment unit is used for performing biochemical treatment on the coal chemical industry sewage to remove COD and ammonia nitrogen;
the biochemical treatment unit comprises an adjusting tank, a nitrogen air flotation tank, a hydrolysis acidification tank, a primary A/O biochemical tank, a secondary A/O biochemical tank, an air flotation tank, an ozone contact tower, an aeration biological filter and an active carbon filter device which are connected in sequence.
2. The system of claim 1, wherein the recycling unit is configured to recover fresh water from the coal chemical wastewater treated by the biochemical treatment unit.
3. The system of claim 2, wherein the recycling unit comprises a biochemical regulating water tank, a recycling section clarification tank, a recycling section multi-medium filtering device, a recycling section ultrafiltration device and a recycling section reverse osmosis device which are connected in sequence.
4. The system of claim 1, wherein the membrane concentration unit is used for carrying out membrane concentration treatment on the concentrated water produced by the recovery unit and obtaining recycled fresh water and concentrated water which can be used for salt separation crystallization.
5. The system according to claim 1, further comprising a salt separation crystallization unit connected with the outlet of the membrane concentration unit, wherein the salt separation crystallization unit is used for carrying out salt separation crystallization on the concentrated water containing sodium sulfate and sodium chloride and produced by the membrane concentration unit to obtain sodium sulfate crystals and sodium chloride crystals.
6. The system of claim 5, wherein the salt separation crystallization unit comprises a sodium sulfate crystallization device and a sodium chloride crystallization device, the sodium sulfate crystallization device is connected with the concentrated water outlet of the nanofiltration device, and the sodium chloride crystallization device is connected with the concentrated water outlet of the nanofiltration water production reverse osmosis device;
the sodium sulfate crystallization device comprises a thermal crystallizer and a freezing crystallizer which are connected in sequence;
the thermal crystallizer is provided with a feed inlet, a solid discharge port, a liquid discharge port and a feed back port;
the freezing crystallizer is provided with a feed inlet, a mother liquid discharge port and a solid discharge port;
the feed inlet of the thermal crystallizer is connected with the concentrated water outlet of the nanofiltration device, the liquid discharge port of the thermal crystallizer is connected with the feed inlet of the freezing crystallizer, and the solid discharge port of the freezing crystallizer is connected with the feed back port of the thermal crystallizer.
7. The system of claim 6, wherein said sodium chloride crystallization unit comprises a forced circulation evaporative crystallizer;
the forced circulation evaporation crystallizer is provided with a discharge port and a liquid feed port, and the liquid feed port is connected with a concentrated water outlet of the nanofiltration water production reverse osmosis device.
8. The system of claim 7, wherein the forced circulation evaporative crystallizer is further provided with a mother liquor feeding port, and the mother liquor feeding port is connected with a mother liquor discharging port of the freezing crystallizer.
9. The coal chemical industry sewage zero emission treatment and salt separation crystallization method with electrolytic oxidation is characterized in that the method is carried out in the system of any one of claims 1 to 8, and the method comprises the following steps:
sequentially passing coal chemical industry sewage through a recycling unit and a pre-concentration device to obtain reverse osmosis concentrated water;
(II) oxidizing the reverse osmosis concentrated water by an electrolytic oxidation device to obtain electrolytic oxidation water;
and (III) discharging the electrolyzed oxidation produced water, and sequentially passing through a nanofiltration device and a nanofiltration produced water reverse osmosis device to obtain concentrated water for salt separation crystallization.
10. The method of claim 9 wherein the COD in the reverse osmosis concentrate of step (I) isCrThe content is 500-700 mg/L.
11. The method as claimed in claim 9, wherein the electrolysis time of the electrolytic oxidation device in the step (II) is less than or equal to 6 h.
12. The method according to claim 9, wherein the electrolytic current of the electrolytic oxidation apparatus is 500 to 800A.
13. The method of claim 9, wherein the electrolytic oxidation produces COD in the waterCr300-340 mg/L;
and (III) carrying out nanofiltration on the electrolyzed oxidation water product to obtain nanofiltration concentrated water and nanofiltration water product, and carrying out thermal freezing crystallization on the nanofiltration concentrated water to separate out sodium sulfate crystals.
14. The method of claim 13, wherein the nanofiltration product water is subjected to nanofiltration product water reverse osmosis to obtain reverse osmosis concentrate water and reverse osmosis product water.
15. The method of claim 14 wherein the reverse osmosis concentrate is crystallized by evaporation to precipitate sodium chloride crystals.
16. The method of claim 14 wherein the reverse osmosis produced water is collected for reuse.
17. The method as claimed in claim 13, wherein the sodium sulfate crystal has a sodium sulfate content of 97.0% or more, a water content of 1.0% or less, a chloride content of 0.9% or less, and a calcium-magnesium ion content of 0.4% or less.
18. The method as claimed in claim 15, wherein the sodium chloride crystal has a sodium chloride content of not less than 92%, a moisture content of not more than 6.0%, a sulfate ion content of not more than 1.0%, and a calcium and magnesium ion content of not more than 0.6%.
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| CN203568944U (en) * | 2013-11-18 | 2014-04-30 | 苏州膜华材料科技有限公司 | Coking wastewater reuse treatment system |
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