A zero-discharge treatment system and method for regenerated wastewater from a soft water station

Abstract

The present invention relates to a zero-discharge treatment system and method for regenerated wastewater from a soft water station. The system includes a regulating tank, a vortex-type hydraulic cavitation accelerated coagulation nucleation unit, an electroflocculation-microfiltration unit, and an electrodialysis-electrolysis unit. The vortex-type hydraulic cavitation accelerated coagulation nucleation unit is composed of a vortex-type hydraulic cavitation device and a scale separation device, and the scale separation device includes a magnesium scale and separation device and a calcium scale and separation device. The electroflocculation-microfiltration unit is composed of an electroflocculation tank and a microfiltration tank, and the electrodialysis-electrolysis unit is an electrodialysis-electrolysis tank. The regenerated wastewater first passes through the vortex-type hydraulic cavitation accelerated coagulation nucleation unit to degrade organic matter and remove hardness. The residual flocculants, colloids, and hardness are then deeply treated by the electroflocculation-microfiltration unit. Finally, the wastewater is concentrated by the electrodialysis-electrolysis unit. While achieving zero discharge in the process, it can also generate certain economic value. The system occupies a small area and has low investment and operation and maintenance costs.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial wastewater treatment, and in particular to a zero-discharge treatment system and method for regenerated wastewater from a soft water station in the metallurgical and petrochemical industries. Background Art

[0002] Softening hard water produces softened water with calcium and magnesium salt contents ranging from 1.0 to 50 mg / L. This softened water is suitable for use in the electronics and power industries, metallurgy, pharmaceuticals, chemicals, food and beverages, hotels, heating plants, boiler rooms, office buildings, cold storage facilities, shopping malls, and air conditioning systems. In the petrochemical industry, softened water is widely used in production cooling systems. Existing water softening equipment typically uses resin to adsorb calcium and magnesium ions. Once adsorption reaches saturation, the resin requires regeneration. Resin regeneration requires replacement with sodium chloride or hydrochloric acid, generating large amounts of highly hard and salty regeneration wastewater containing MgCl₂ and CaCl₂. This type of wastewater is characterized by low organic matter content and wide pH fluctuations. Directly mixing it into the plant's biochemical treatment system would cause irregular impacts on the wastewater treatment environment, hindering overall wastewater treatment. Currently, four main treatment methods for this type of wastewater are available: acid-base neutralization, combined precipitation, Fenton-sedimentation, and membrane processes.

[0003] In the article "Simulation Experimental Study on Reuse Treatment of Ion Exchange Resin Regeneration Wastewater" (Guo Chunmei et al., Journal of Environmental Engineering, Vol. 2, No. 1, January 2008), a staged treatment simulation experiment was conducted on regeneration wastewater. While the treatment results were good, the process was complex, with treatment costs potentially exceeding 50 yuan per ton of water, making it unsuitable for industrial adoption.

[0004] Chinese patent application publication number CN110776132A discloses a "zero-discharge process and apparatus for treating regeneration wastewater in a coal-fired power plant boiler feedwater system." This approach uses sulfuric acid instead of sodium chloride or hydrochloric acid, converting sulfate ions into gypsum to achieve zero discharge. However, during hardness regeneration and replacement, sulfate ions combine with calcium and magnesium ions, trapping and entrapping resin particles, reducing the resin's treatment effectiveness and lifespan.

[0005] Chinese invention patent CN103073143B discloses a "zero-discharge treatment process for brine in steel mills." Recycled wastewater is first heated and circulated for concentration, and then treated with a reverse osmosis membrane to produce distilled water. The concentrated water retained by the reverse osmosis process is returned to the crystallization and evaporation system, while the clean water is returned to the water replenishment system. While this process offers excellent results and achieves zero discharge, its cost is also prohibitive, and it fails to address reverse osmosis membrane clogging, making it unsuitable for industrial application.

[0006] A Chinese patent application with publication number CN101955286A discloses a "desalination process for concentrated brine," which also uses evaporation technology to concentrate and extract salt from recycled wastewater. The effluent effect is good, and the treatment cost is reduced accordingly due to the use of a heat recovery device. However, the removal effect on organic matter in the water is limited.

[0007] In summary, the current challenges with treating regenerated wastewater from softening stations are: low-cost treatment results are poor, and the cost of achieving zero softened water discharge remains high. Therefore, developing a low-cost, short-cycle, and effective treatment process for regenerated wastewater from softening stations is crucial. This would not only reduce environmental impact but also alleviate the financial burden on businesses. Summary of the Invention

[0008] The present invention provides a zero-discharge treatment system and method for regenerated wastewater from a soft water station. The regenerated wastewater first passes through a vortex-type hydraulic cavitation accelerated condensation unit to degrade organic matter and remove hardness. The residual flocculants, colloids and hardness are then deeply treated through an electric flocculation-microfiltration unit. Finally, the wastewater is concentrated through an electrodialysis-electrolysis unit. An electrolysis system is provided in a concentrated liquid tank to produce NaOH, H2, Cl2 and the like. Sodium hydroxide is added to a magnesium scaling tank. Chlorine is collected and purified and can be sold or prepared with sodium hydroxide to produce sodium hypochlorite solution. Zero discharge of the process can be achieved while generating certain economic value. The system occupies a small area and has low investment and operation and maintenance costs.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A zero-discharge treatment system for regenerated wastewater from a soft water station comprises a regulating tank, a vortex-type hydraulic cavitation accelerated coagulation nucleation unit, an electric flocculation-microfiltration unit and an electrodialysis-electrolysis unit connected in sequence; the vortex-type hydraulic cavitation accelerated coagulation nucleation unit comprises a vortex-type hydraulic cavitation device and a scaling separation device, the scaling separation device comprises a magnesium scaling and separation device, and a calcium scaling and separation device; the electric flocculation-microfiltration unit comprises an electric flocculation tank and a microfiltration tank, and the electrodialysis-electrolysis unit is an electrodialysis-electrolysis tank.

[0011] Furthermore, the vortex hydrodynamic cavitation device is composed of a liquid inlet section, an air-water mixing section and an air-water separation section arranged in sequence from top to bottom; the top of the liquid inlet section is provided with an inlet for wastewater and acid mixture, the inner cavity of the liquid inlet section is a tapered cavity narrowed downward, and the side wall of the tapered cavity is provided with hydraulic cyclone rifling; the air-water mixing section is composed of a cyclone cavity and an air-water mixing cavity, the cyclone cavity is a fan-shaped cavity narrowed downward, and the top of the fan-shaped cavity is connected to the lower opening of the tapered cavity of the liquid inlet section; an aeration disk is provided in the cyclone cavity, a plurality of aeration holes are provided on the top of the aeration disk, and the bottom of the aeration disk is connected to the external high-pressure air inlet pipe through a high-pressure air pipe; the bottom of the cyclone cavity A vortex hydraulic cavitation grinding disc is provided at the outlet, which can rotate horizontally. A plurality of corrugated bowls are provided on the top of the vortex hydraulic cavitation grinding disc. The wastewater in the vortex cavity flows from the annular gap between the vortex hydraulic cavitation grinding disc and the vortex cavity to the air-water mixing cavity. The air-water mixing cavity is a tapered cavity that narrows downward. The air-water separation section consists of a wastewater tank and a corrugated plate. A connecting pipe is provided at the lower end of the air-water mixing cavity, which extends to the bottom of the wastewater tank. An air outlet is provided on the top of the wastewater tank, and a corrugated plate is provided in the space above the wastewater liquid level in the wastewater tank. A post-cavitation wastewater outlet is provided on one side of the lower part of the wastewater tank.

[0012] Furthermore, the top surface of the aeration plate is a concave arc surface, and the aeration holes are arranged in an arc shape on the aeration plate.

[0013] Furthermore, a transmission shaft is provided in the middle of the vortex hydraulic cavitation grinding disc, and the transmission shaft is driven by a rotary drive mechanism to drive the vortex hydraulic cavitation grinding disc to rotate.

[0014] Furthermore, the scaling separation device includes a magnesium scaling and separation device, a calcium scaling and separation device and an outlet regulating box; the magnesium scaling and separation device consists of a magnesium scaling box and a magnesium scaling separation box; the magnesium scaling box is provided with a cavitation wastewater inlet pipe connected to the cavitation wastewater outlet of the wastewater tank, a stirring paddle is provided in the magnesium scaling box, and the magnesium scaling box is also provided with a sodium hydroxide solution inlet pipe and a magnesium scale mixed liquid outlet pipe; the magnesium scale separation box is provided with a magnesium scale mixed liquid inlet pipe connected to the magnesium scale mixed liquid outlet pipe, and a flocculant addition pipe is provided on the magnesium scale mixed liquid inlet pipe; the magnesium scale separation box is provided with an overflow section, an inclined pipe sedimentation section and a mud discharge section from top to bottom, the overflow section is provided with an overflow weir, and is connected to the calcium scaling box through the magnesium removal wastewater outlet pipe; the inclined pipe sedimentation section is provided with an inclined pipe, and the mud discharge section is provided with a mud discharge pipe, one end of the mud discharge pipe extends into the magnesium scale separation box and It is arranged along the water flow direction, and the sludge discharge pipe in the magnesium scale separation box is provided with multiple sludge discharge holes; the calcium scale box is provided with a stirring paddle, and the calcium scale box is also provided with a sodium carbonate inlet pipe and a calcium scale mixed liquid outlet pipe; the calcium scale separation box is provided with a calcium scale mixed liquid inlet pipe connected to the calcium scale mixed liquid outlet pipe, and a flocculant addition pipe is provided on the calcium scale mixed liquid inlet pipe; the calcium scale separation box is provided with an overflow section, an inclined pipe sedimentation section and a sludge discharge section from top to bottom, the overflow section is provided with an overflow weir, and is connected to the outlet regulating box through the decalcification wastewater inlet pipe; the inclined pipe sedimentation section is provided with an inclined pipe, and the sludge discharge section is provided with a sludge discharge pipe, one end of the sludge discharge pipe extends into the calcium scale separation box and is arranged along the water flow direction, and the sludge discharge pipe in the calcium scale separation box is provided with multiple sludge discharge holes; the outlet regulating box is provided with a hydrochloric acid addition pipe and a decalcification and magnesium wastewater outlet pipe, and the outlet regulating box is provided with a triple-blade stirring paddle.

[0015] Furthermore, the electrodialysis-electrolysis unit comprises an electrodialysis-electrolysis cell, a hydrogen collection device, and a chlorine collection device; a semipermeable membrane is provided in the electrodialysis-electrolysis cell to separate the electrodialysis-electrolysis cell into a concentrate pool and a fresh water pool; an electrolysis device is provided in the concentrate pool, and an iron rod is used as an anode and a graphite rod is used as a cathode, and the anode and cathode are connected by a DC power supply; a chlorine collection device is provided at the anode, and a hydrogen collection device is provided at the cathode.

[0016] A method for treating regenerated wastewater from a soft water station with zero discharge, comprising the following steps:

[0017] 1) The regenerated wastewater enters the regulating tank and is adjusted to a pH value of 5-11. It is then heated to 35-45°C by heat exchange with a heat source. Hypochlorous acid and hydrochloric acid are then added to the regenerated wastewater to form a mixed aqueous solution, which is then fed into a vortex hydrodynamic cavitation device.

[0018] 2) Under the action of water pressure and hydrocyclone rifling, the mixed aqueous solution enters the cyclone chamber at high speed in a swirling state. The pressure of the mixed aqueous solution entering the cyclone chamber suddenly decreases, and the flow rate increases. It quickly mixes with the high-pressure air ejected from the aeration holes on the aeration disk, and then collides with the high-speed rotating vortex hydrodynamic cavitation grinding disk, forming extreme turbulence and mechanical shear in the corrugated bowl and releasing a large amount of energy, thereby degrading organic matter in the mixed aqueous solution and achieving cavitation of the mixed aqueous solution. The cavitation water enters the wastewater tank below, and after the corrugated plate intercepts some water vapor, the remaining gas is discharged from the air outlet. The water outlet of the vortex hydrodynamic cavitation device enters the magnesium scale separation device through the post-cavitation wastewater outlet.

[0019] 3) The effluent from the vortex hydrodynamic cavitation device first enters the magnesium scaling tank, and sodium hydroxide solution produced by the electrodialysis-electrolysis cell is added at the same time to maintain the pH value of the inlet water of the magnesium scaling tank between 9 and 12. The speed of the stirring paddle in the magnesium scaling tank is 100 to 1000 r / min, and the hydraulic retention time is 10 to 30 minutes. After the flocculant is added to the effluent from the magnesium scaling tank, it enters the magnesium scale separation tank with a hydraulic retention time of 0.5 to 3 hours. The separated magnesium scale is precipitated and discharged through the mud discharge pipe. The effluent from the magnesium scale separation tank enters the calcium scaling separation device.

[0020] The effluent from the magnesium scale separation tank first enters the calcium scaling tank, where the pH value of the inlet water is adjusted to 12-14. Then, a sodium carbonate solution with a concentration of 8-10wt% is added. The speed of the stirring paddle in the calcium scaling tank is 100-1000r / min, and the hydraulic retention time is 5-20min. After flocculant is added to the effluent from the calcium scaling tank, it enters the calcium scale separation tank with a hydraulic retention time of 0.5-3h. The separated calcium scale is precipitated and discharged through the mud discharge pipe. The effluent from the calcium scale separation tank enters the effluent regulating tank.

[0021] Hydrochloric acid is added to the effluent regulating tank while stirring to adjust the pH value of the wastewater to 7±0.5. The effluent from the effluent regulating tank enters the electrocoagulation-microfiltration device;

[0022] 4) The water from the outlet regulating box first enters the electric flocculation tank, and the current density of the electric flocculation tank is 0.3~1.0A / m 2 The plate spacing is 1.0-5.0 cm, and the hydraulic retention time is 20-45 min. The effluent from the electroflocculation tank is pressurized to 150-530 kPa by a circulating pump and then enters the microfiltration tank. The water output of the microfiltration tank is 150-550 L / m 2 h, the microfiltration water with turbidity less than 3 NTU enters the electrodialysis-electrolysis device;

[0023] 5) Electrodialysis - Under the action of a 5-11 V external DC electric field, sodium ions in the water move through the semipermeable membrane to the cathode, and chloride ions move through the semipermeable membrane to the anode, forming concentrated liquid and fresh water, achieving the purpose of concentration; the fresh water is returned to the production site for use as recycled water or make-up water; the hydrogen produced at the cathode and the chlorine produced at the anode are collected, and when the hydrogen production rate is reduced to 20-25 m 3 / h, the sodium hydroxide produced by electrolysis is supplemented to the magnesium scale separation device and the calcium scale separation device, and the remaining sodium hydroxide solution is stored or sold.

[0024] Furthermore, in the step 2), the rotation speed of the vortex hydrodynamic cavitation grinding disc is 2000-6000 r / min.

[0025] Furthermore, in step 3), the concentration of the sodium hydroxide solution generated by the electrodialysis-electrolysis cell is 5 to 10 mol / L.

[0026] Furthermore, in the step 3), the flocculant is a PAM flocculant with a mass percentage concentration of 1 to 3‰.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) The process flow is rationally designed, with different treatment methods adopted for different stages. A vortex-type hydraulic cavitation accelerated condensation unit is first used to treat organic matter and hardness, and then an electrocoagulation-microfiltration unit is used to further purify the regenerated wastewater to meet the requirements of electrodialysis-electrolysis and prevent contamination of the semipermeable membrane by impurities. The electrolysis device is installed in the concentrate tank, which can produce economically valuable products while reducing investment and floor space.

[0029] 2) Using hydraulic cavitation technology, which is simple and efficient, it can change the state of calcium and magnesium crystal nuclei while degrading organic matter, accelerating precipitation formation;

[0030] 3) The vortex hydraulic cavitation accelerated condensation unit has a small footprint, is easy to operate, and can be fully automated;

[0031] 4) The system and method described in the present invention can be used to transform and upgrade the existing plant recycling wastewater treatment system. It occupies a small area, has low investment and operation and maintenance costs, is suitable for various water volume and wastewater conditions, and can truly achieve low-cost zero emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process flow chart of a zero-discharge treatment system for regenerated wastewater from a soft water station described in the present invention.

[0033] Figure 2 It is a structural schematic diagram of the vortex hydrodynamic cavitation device of the present invention.

[0034] Figure 3 It is a front view of the aeration plate of the present invention.

[0035] Figure 4 yes Figure 3 Top view of .

[0036] Figure 5 It is a front view of the hydrodynamic cavitation grinding disc of the present invention.

[0037] Figure 6 yes Figure 5 Top view of .

[0038] Figure 7 Schematic diagram of the scaling separation device of the present invention.

[0039] Figure: 1. Wastewater and acid mixture inlet 2. Hydrocyclone rifling 3. Cyclone chamber 4. Aeration holes 5. Aeration plate 6. High-pressure air pipe 7. High-pressure air inlet pipe 8. Vortex hydrodynamic cavitation grinding disc 9. Corrugated bowl 10. Air-water mixing chamber 11. Air outlet 12. Corrugated plate 13. Cavitation wastewater outlet 14. Wastewater tank 15. Wastewater level 16. Cavitation wastewater inlet pipe 17. Sodium hydroxide solution inlet pipe 18. Magnesium scale tank 19. Magnesium scale mixture outlet pipe 20. Stirring Paddle 21. Flocculant addition pipe 22. Magnesium scale mixture inlet pipe 23. Overflow weir 24. Inclined pipe 25. Magnesium scale separation tank 26. Mud discharge hole 27. Mud discharge pipe 28. Magnesium removal wastewater outlet pipe 29. Calcium scale tank 30. Sodium carbonate inlet pipe 31. Calcium scale mixture outlet pipe 32. Calcium scale separation tank 33. Calcium removal wastewater inlet pipe 34. Hydrochloric acid addition pipe 35. Triple-blade agitator 36. Calcium and magnesium removal wastewater outlet pipe 37. Calcium scale mixture inlet pipe 38. Connecting pipe 39. Drive shaft Implementation Method

[0040] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0041] like Figure 1 As shown, the zero-discharge treatment system for regenerated wastewater from a soft water station described in the present invention is mainly composed of a regulating tank, a vortex-type hydraulic cavitation accelerated condensation unit, an electric flocculation-microfiltration unit, an electrodialysis-electrolysis unit and the like.

[0042] The pH of the regenerated wastewater is first adjusted in a regulating tank. After stabilizing the pH, it enters a vortex-type hydrodynamic cavitation accelerated condensation unit for organic matter degradation and hardness removal, as well as recovery of crude calcium and magnesium salts. The regenerated wastewater then enters an electrocoagulation-microfiltration unit for advanced treatment of residual flocculants, colloids, and hardness, ensuring an effluent turbidity of less than 3 NTU. The relatively clean regenerated wastewater from the pre-treatment process enters an electrodialysis-electrolysis unit to concentrate the sodium chloride-rich solution. Fresh water from the concentrated freshwater tank is added to the reclaimed water for reuse. An electrolysis system is installed in the concentrate tank to produce economically valuable products such as NaOH, H2, and Cl2. Sodium hydroxide is added to the magnesium scale tank in the upstream stage, while chlorine is collected, purified, and sold or combined with sodium hydroxide to produce sodium hypochlorite solution. The crude calcium and magnesium salts can be sold externally, achieving zero emissions while generating significant economic value.

[0043] like Figure 2 As shown, the vortex type hydrodynamic cavitation device mainly consists of a cyclone chamber 3, an aeration plate 5 (such as Figure 3 、 Figure 4 As shown), eddy current hydrodynamic cavitation grinding disc 8 (as Figure 5 、 Figure 6 As shown), an air-water mixing chamber 10, a corrugated plate 12, a waste water tank 14, etc.

[0044] Specifically, the vortex hydrodynamic cavitation device consists of a liquid inlet section, an air-water mixing section and an air-water separation section, which are arranged in sequence from top to bottom; a wastewater and acid mixture inlet 1 is provided at the top of the liquid inlet section, the inner cavity of the liquid inlet section is a tapered cavity narrowing downward, and the side wall of the tapered cavity is provided with a hydraulic cyclone rifling 2; the air-water mixing section is composed of a cyclone chamber 3 and an air-water mixing chamber 10, the cyclone chamber 3 is a fan-shaped cavity narrowing downward, and the top of the fan-shaped cavity is connected to the lower mouth of the tapered cavity of the liquid inlet section; an aeration plate 5 is provided in the cyclone chamber 3, and a plurality of aeration holes 4 are provided on the top of the aeration plate 5, and the bottom of the aeration plate 5 is connected to an external high-pressure air inlet pipe 7 through a high-pressure air pipe 6; further, the top surface of the aeration plate 5 is a concave arc surface, and the aeration holes 4 are arranged in an arc surface on the aeration plate 5. A vortex hydraulic cavitation grinding disc 8 is provided at the bottom outlet of the vortex chamber 3, and the vortex hydraulic cavitation grinding disc 8 can rotate horizontally (a transmission shaft 39 is provided in the middle of the vortex hydraulic cavitation grinding disc 8, and the transmission shaft 39 is driven by a rotary drive mechanism and drives the vortex hydraulic cavitation grinding disc 8 to rotate). A plurality of corrugated bowl pools 9 are provided on the top of the vortex hydrodynamic cavitation grinding disc 8. The wastewater in the cyclone chamber 3 flows from the annular gap between the vortex hydrodynamic cavitation grinding disc 8 and the cyclone chamber 3 to the air-water mixing chamber 10; the air-water mixing chamber 10 is a tapered cavity that narrows downward; the air-water separation section consists of a wastewater tank 14 and a corrugated plate 12; a connecting pipe 38 is provided at the lower end of the air-water mixing chamber 10, and the connecting pipe 38 extends to the bottom of the wastewater tank 14; an air outlet 11 is provided at the top of the wastewater tank 14, and a corrugated plate 12 is provided in the space above the wastewater liquid level 15 in the wastewater tank 14; a post-cavitation wastewater outlet 13 is provided on one side of the lower portion of the wastewater tank 14.

[0045] like Figure 7 As shown, the scaling separation device includes a magnesium scaling separation device and a calcium scaling separation device.

[0046] The magnesium scale separation device consists of a magnesium scale tank 18 and a magnesium scale separation tank 25. The magnesium scale tank 18 is mainly equipped with a sodium hydroxide solution inlet pipe 17, a magnesium scale mixed liquid outlet pipe 19, a stirring paddle 20, etc. The magnesium scale separation tank 18 is mainly equipped with a flocculant addition pipe 21, a magnesium scale mixed liquid inlet pipe 22, an overflow weir 23, an inclined pipe 24, a mud discharge pipe 27, and a magnesium removal wastewater outlet pipe 28.

[0047] The calcium scale separation device consists of a calcium scale tank 29 and a calcium scale separation tank 32. The calcium scale tank 29 is mainly equipped with a sodium carbonate inlet pipe 30, a calcium scale mixed liquid outlet pipe 31 and a stirring paddle 20; the calcium scale separation tank 32 is mainly equipped with a flocculant addition pipe 21, a calcium scale mixed liquid inlet pipe 37, an overflow weir 23, an inclined pipe 24, a mud discharge pipe 27, etc.

[0048] The outlet water regulating box is mainly provided with a decalcification wastewater inlet pipe 33, a hydrochloric acid addition pipe 34, a triple-blade stirring paddle 35, a decalcification and magnesium wastewater outlet pipe 36, etc.

[0049] Specifically, the scaling and separation device includes a magnesium scaling and separation device, a calcium scaling and separation device, and a water outlet regulating box; the magnesium scaling and separation device consists of a magnesium scaling box 18 and a magnesium scaling separation box 25; the magnesium scaling box 18 is provided with a cavitation wastewater inlet pipe 16 connected to the cavitation wastewater outlet 13 of the wastewater tank 14, a stirring paddle 20 is provided in the magnesium scaling box 18, and the magnesium scaling box 18 is also provided with a sodium hydroxide solution inlet pipe 17 and a magnesium scale mixed liquid outlet pipe 19; the magnesium scaling separation box 25 is provided with a magnesium scale mixed liquid inlet pipe 22 connected to the magnesium scale mixed liquid outlet pipe 19, and a flocculant adding pipe 21 is provided on the magnesium scale mixed liquid inlet pipe 22; an overflow section, an inclined pipe sedimentation section and a mud discharge section are provided from top to bottom in the magnesium scale separation box 18, an overflow weir 23 is provided in the overflow section, and is connected to the calcium scaling box 29 through the magnesium removal wastewater outlet pipe 28; an inclined pipe 24 is provided in the inclined pipe sedimentation section, a mud discharge pipe 27 is provided in the mud discharge section, one end of the mud discharge pipe 27 extends into the magnesium scale separation box 18 and flows along the water flow. The direction is through-length, and a plurality of mud discharge holes 26 are provided on the mud discharge pipe 27 in the magnesium scale separation box 28; a stirring paddle 20 is provided in the calcium scale box 29, and the calcium scale box 29 is also provided with a sodium carbonate inlet pipe 30 and a calcium scale mixed liquid outlet pipe 31; the calcium scale separation box 32 is provided with a calcium scale mixed liquid inlet pipe 37 connected to the calcium scale mixed liquid outlet pipe 31, and a flocculant adding pipe 21 is provided on the calcium scale mixed liquid inlet pipe 37; the calcium scale separation box 32 is provided with an overflow section, an inclined pipe sedimentation section and a plurality of other sections from top to bottom. The sedimentation section and the mud discharge section are provided with an overflow weir 23 in the overflow section, and are connected to the outlet regulating tank through the decalcification wastewater inlet pipe 33; the inclined tube sedimentation section is provided with an inclined tube 24, and the mud discharge section is provided with a mud discharge pipe 27, one end of the mud discharge pipe 27 extends into the calcium-scale separation tank 32 and is arranged along the water flow direction. The mud discharge pipe 27 in the calcium-scale separation tank 32 is provided with multiple mud discharge holes 26; the outlet regulating tank is provided with a hydrochloric acid addition pipe 34 and a decalcification and magnesium wastewater outlet pipe 36, and a triple-blade stirring paddle 35 is provided in the outlet regulating tank.

[0050] The electrodialysis-electrolysis unit comprises an electrodialysis-electrolysis cell, a hydrogen collection device, and a chlorine collection device; a semipermeable membrane is provided in the electrodialysis-electrolysis cell to separate the electrodialysis-electrolysis cell into a concentrate pool and a fresh water pool; an electrolysis device is provided in the concentrate pool, and an iron rod is used as an anode and a graphite rod is used as a cathode, and the anode and cathode are connected via a DC power supply; a chlorine collection device is provided at the anode, and a hydrogen collection device is provided at the cathode.

[0051] The specific steps of the zero-discharge treatment method for regenerated wastewater from a soft water station described in the present invention are as follows:

[0052] The regenerated wastewater enters the regulating tank, where the pH is adjusted to 5-11. It then exchanges heat with the existing chimney or other heat sources in the plant area. The temperature of the regenerated wastewater after heat exchange is controlled to be 35-45°C. A small amount of hypochlorous acid (obtained by passing chlorine gas into water) and hydrochloric acid are introduced into the regenerated wastewater to form a mixed aqueous solution (the concentration of hypochlorous acid is 100-500 mg / L). The mixed aqueous solution enters the vortex hydraulic cavitation accelerated condensation unit.

[0053] The vortex hydraulic cavitation accelerated condensation unit is divided into two parts: the vortex hydraulic cavitation device and the scaling separation device. The wastewater degrades a small amount of organic matter under the action of cavitation bubble water phase combustion, free radicals and hypochlorous acid.

[0054] The rotation speed of the eddy current hydrodynamic cavitation grinding disc 8 is 2000-6000 r / min.

[0055] The regenerated wastewater after cavitation enters the magnesium scale separation device, first entering the magnesium scale tank 18, and adding a sodium hydroxide solution with a concentration of 5 to 10 mol / L produced by the electrodialysis-electrolysis cell. The pH value of the water inlet to the magnesium scale tank 18 is maintained at 9 to 12, the speed of the stirring paddle 20 is 100 to 1000 r / min, and the hydraulic retention time is 10 to 30 minutes; the effluent from the magnesium scale tank is added with a PAM flocculant with a concentration of 1 to 3‰ and then enters the magnesium scale separation tank 25. The hydraulic retention time is 0.5 to 3 hours. After the magnesium scale is precipitated, it is discharged through the mud pipe 27. The regenerated wastewater after magnesium removal (the effluent from the magnesium scale separation tank) enters the calcium scale separation device.

[0056] The effluent from the magnesium scale separation tank first enters the calcium scale separation tank 29, where the pH is adjusted to 12-14. Then, a sodium carbonate solution with a concentration of 8-10wt% is added. The speed of the stirring paddle 20 is 100-1000r / min, and the hydraulic retention time is 5-20min. Then, a PAM flocculant with a concentration of 1-3‰ is added and the effluent enters the calcium scale separation tank 32. The hydraulic retention time is 0.5-3h. After the calcium scale is precipitated, it is discharged through the sludge pipe 27. The regenerated wastewater after decalcification (the effluent from the calcium scale separation tank) enters the effluent regulating tank.

[0057] The outlet water regulating box is used to maintain the outlet water of the vortex type hydraulic cavitation accelerated condensation unit at pH=7±0.5, and the outlet water of the outlet water regulating box enters the electric flocculation-microfiltration unit.

[0058] The electrocoagulation-microfiltration unit is composed of an electrocoagulation tank and a microfiltration tank; the electrocoagulation tank maintains a current density of 0.3 to 1 A / m 2 The plate spacing is 1 to 5 cm, and the hydraulic retention time is 20 to 45 minutes. The effluent from the electroflocculation tank is pressurized to 150 to 530 kPa by a circulating pump and then enters a microfiltration tank (preferably a tubular microfiltration tank). The water output of the microfiltration tank is 150 to 550 L / (m 2 h). The water produced by the microfiltration tank enters the electrodialysis-electrolysis unit.

[0059] The electrodialysis-electrolysis unit is an electrodialysis-electrolysis cell. Under the action of an external DC electric field, sodium ions in the regenerated wastewater migrate through a semipermeable membrane toward the cathode, while chloride ions migrate through the semipermeable membrane toward the anode, forming a concentrated solution and fresh water, achieving the purpose of concentration. The fresh water is returned to production as reclaimed water or make-up water.

[0060] An electrolysis device is installed in the concentrate pool of the electrodialysis-electrolysis cell. An iron rod (anode) is inserted into one side of the concentrate pool and a graphite rod (cathode) is inserted into the other side. The voltage of the DC power supply is controlled to be 5-11 V. The hydrogen produced by the cathode and the chlorine produced by the anode are collected. When the hydrogen production rate is reduced to 20-25 m 3 / h later, the sodium hydroxide produced by electrolysis is added to the magnesium scaling tank, and the remaining sodium hydroxide solution is stored or sold.

[0061] To make the objectives, technical solutions, and technical effects of the present invention more clear, the technical solutions in the embodiments of the present invention are now clearly and completely described. However, the embodiments described below are only some of the embodiments of the present invention, not all of them. In combination with the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0062] In the following examples, all raw reagents and materials are commercially available. Experimental methods without specific conditions are conventional methods and conditions well known in the art, or are performed according to the conditions recommended by the instrument manufacturer. Example

[0063] like Figure 1-Figure 7 As shown, in this embodiment, the zero-discharge treatment process of the regenerated wastewater from the soft water station is as follows:

[0064] The regenerated wastewater from the soft water station enters the regulating tank to adjust the pH value to 7±0.5, and is heat exchanged to 40℃, and then enters the vortex hydraulic cavitation accelerated condensation unit for organic matter degradation and hardness removal.

[0065] After being thoroughly mixed with hypochlorous acid (made from water and chlorine, with a concentration of 200 mg / L) and hydrochloric acid solution, the regenerated wastewater enters the liquid inlet section. Under the influence of water pressure and the hydrocyclone rifling 2, the mixed aqueous solution enters the cyclone chamber 3 at high speed. Due to the sudden decrease in pressure at the cyclone chamber 3 entrance, the water flow rate increases again, rapidly mixing with the high-pressure air ejected from the aeration disk 5 and colliding with the vortex hydrodynamic cavitation grinding disk 8 rotating at 6000 r / min. The corrugated bowl 9 on the upper surface of the vortex hydrodynamic cavitation grinding disk 8 violently collides with the water flow, creating extreme turbulence and mechanical shear within the bowl 9, releasing a large amount of energy. This process cavitation degrades organic matter, and the cavitated water enters the wastewater tank 14. The corrugated plate 12 intercepts some water vapor, and the remaining gas is discharged through the air outlet 11. The water from the wastewater tank enters the magnesium scale separation device through the post-cavitation wastewater outlet.

[0066] The regenerated wastewater after cavitation first enters the magnesium scaling tank 18. At the same time, a sodium hydroxide solution with a concentration of 5 to 10 mol / L produced by the electrodialysis-electrolysis cell is added to the regenerated wastewater to keep the inlet pH value at 9 to 12. The rotation speed of the stirring paddle 20 in the magnesium scaling tank 18 is 100 r / min, and the hydraulic retention time is 25 minutes. After the addition of a PAM flocculant with a concentration of 1‰, the regenerated wastewater enters the magnesium scale separation tank 25. The hydraulic retention time of the regenerated wastewater in the magnesium scale separation tank 25 is 1 hour. After the magnesium scale is precipitated, it enters the mud discharge pipe 27 from the mud discharge hole 26 and is discharged outside through the mud discharge pipe 27. The regenerated wastewater after magnesium removal (the outlet water of the magnesium scale separation tank) enters the calcium scaling separation device.

[0067] After magnesium removal, the regenerated wastewater first enters the calcium scale separation tank 29 to adjust its pH to 13. An 8wt% sodium carbonate solution is then added. The stirring paddle 20 in the calcium scale separation tank 29 rotates at 500 rpm, and the hydraulic retention time is 20 minutes. A PAM flocculant at a concentration of 1‰ is then added before entering the calcium scale separation tank 32. The hydraulic retention time in the calcium scale separation tank 32 is 1.5 hours. After the calcium scale settles, it enters the mud discharge pipe 27 through the mud discharge hole 26 and is then discharged through the mud discharge pipe 27. The decalcified regenerated wastewater (the water from the calcium scale separation tank) enters the outlet water regulating tank.

[0068] The outlet water regulating tank adjusts the pH value of the regenerated wastewater to 7±0.5, and the regenerated wastewater after removing calcium and magnesium (outlet water from the outlet water regulating tank) enters the electrocoagulation-microfiltration unit.

[0069] In the electrocoagulation-microfiltration unit, the electrocoagulation cell maintains a current density of 0.8A / m 2 The plate spacing is 2cm, and the hydraulic retention time is 45min. The effluent from the electrocoagulation tank is pressurized to 530kPa by a circulating pump and then enters the microfiltration tank. The tubular microfiltration tank is used, and the water output is 500L / (m 2 h), the microfiltration water with turbidity less than 3 NTU enters the electrodialysis-electrolysis unit.

[0070] The electrodialysis-electrolysis unit uses an electrodialysis-electrolysis cell. Under the action of an external DC electric field, sodium ions in the regenerated wastewater migrate through a semipermeable membrane toward the cathode, while chloride ions migrate through the semipermeable membrane toward the anode, forming a concentrated solution and fresh water, achieving the purpose of concentration. The fresh water is returned to production as reclaimed water or make-up water.

[0071] The concentrate pool of the electrodialysis-electrolysis cell is equipped with an electrolysis device. An iron rod (anode) is inserted into one side of the concentrate pool, and a graphite rod (cathode) is inserted into the other side. The voltage of the DC power supply is controlled at 10 V. The hydrogen produced by the cathode and the chlorine produced by the anode are collected. When the hydrogen production rate is reduced to 25m 3 / h later, the sodium hydroxide produced by electrolysis is added to the magnesium scaling tank, and the remaining sodium hydroxide solution is stored or sold.

[0072] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A zero-discharge treatment system for regenerated wastewater from a soft water station, characterized in that: It includes a regulating tank, a vortex-type hydraulic cavitation accelerated coagulation unit, an electric flocculation-microfiltration unit and an electrodialysis-electrolysis unit connected in sequence; the vortex-type hydraulic cavitation accelerated coagulation unit is composed of a vortex-type hydraulic cavitation device and a scaling separation device, and the scaling separation device includes a magnesium scaling and separation device and a calcium scaling and separation device; the electric flocculation-microfiltration unit is composed of an electric flocculation tank and a microfiltration tank, and the electrodialysis-electrolysis unit is an electrodialysis-electrolysis tank; The vortex hydrodynamic cavitation device is composed of a liquid inlet section, an air-water mixing section and an air-water separation section arranged in sequence from top to bottom; the top of the liquid inlet section is provided with an inlet for wastewater and acid mixture, the inner cavity of the liquid inlet section is a tapered cavity narrowing downward, and the side wall of the tapered cavity is provided with hydrocyclone rifling; the air-water mixing section is composed of a cyclone cavity and an air-water mixing cavity, the cyclone cavity is a fan-shaped cavity narrowing downward, and the top of the fan-shaped cavity is connected to the lower opening of the tapered cavity of the liquid inlet section; an aeration disk is provided in the cyclone cavity, the top of the aeration disk is provided with multiple aeration holes, and the bottom of the aeration disk is connected to the external high-pressure air inlet pipe through a high-pressure air pipe; the bottom outlet of the cyclone cavity A vortex hydraulic cavitation grinding disc is provided, which can rotate horizontally. A plurality of corrugated bowls are provided on the top of the vortex hydraulic cavitation grinding disc. Wastewater in the vortex chamber flows from the annular gap between the vortex hydraulic cavitation grinding disc and the vortex chamber to the air-water mixing chamber. The air-water mixing chamber is a tapered cavity that narrows downward. The air-water separation section consists of a wastewater tank and a corrugated plate. A connecting pipe is provided at the lower end of the air-water mixing chamber, which extends to the bottom of the wastewater tank. An air outlet is provided at the top of the wastewater tank, and a corrugated plate is provided in the space above the wastewater liquid level in the wastewater tank. A post-cavitation wastewater outlet is provided on one side of the lower part of the wastewater tank. The electrodialysis-electrolysis unit comprises an electrodialysis-electrolysis cell, a hydrogen collection device, and a chlorine collection device; a semipermeable membrane is provided in the electrodialysis-electrolysis cell to separate the electrodialysis-electrolysis cell into a concentrate pool and a fresh water pool; an electrolysis device is provided in the concentrate pool, and an iron rod is used as an anode and a graphite rod is used as a cathode, and the anode and cathode are connected via a DC power supply; a chlorine collection device is provided at the anode, and a hydrogen collection device is provided at the cathode.

2. A zero-discharge treatment system for regenerated wastewater from a soft water station according to claim 1, characterized in that: The top surface of the aeration plate is an inwardly concave arc surface, and the aeration holes are arranged on the aeration plate in an arc shape.

3. A zero-discharge treatment system for recycled wastewater from a soft water station according to claim 1, characterized in that: A transmission shaft is arranged in the middle of the eddy current hydraulic cavitation grinding disc. The transmission shaft is driven by a rotary drive mechanism and drives the eddy current hydraulic cavitation grinding disc to rotate.

4. A zero-discharge treatment system for recycled wastewater from a soft water station according to claim 1, characterized in that: The scaling and separation device comprises a magnesium scaling and separation device, a calcium scaling and separation device and an outlet regulating box; the magnesium scaling and separation device consists of a magnesium scaling box and a magnesium scaling separation box; the magnesium scaling box is provided with a cavitation wastewater inlet pipe connected to the cavitation wastewater outlet of the wastewater box, a stirring paddle is provided in the magnesium scaling box, and the magnesium scaling box is also provided with a sodium hydroxide solution inlet pipe and a magnesium scale mixed liquid outlet pipe; the magnesium scale separation box is provided with a magnesium scale mixed liquid inlet pipe connected to the magnesium scale mixed liquid outlet pipe, and a flocculant addition pipe is provided on the magnesium scale mixed liquid inlet pipe; the magnesium scale separation box is provided with an overflow section, an inclined pipe sedimentation section and a mud discharge section from top to bottom, the overflow section is provided with an overflow weir, and is connected to the calcium scaling box through the magnesium removal wastewater outlet pipe; the inclined pipe sedimentation section is provided with an inclined pipe, and the mud discharge section is provided with a mud discharge pipe, one end of the mud discharge pipe extends into the magnesium scale separation box and flows along the water flow The direction is set in full length, and the mud discharge pipe in the magnesium scale separation box is provided with multiple mud discharge holes; the calcium scaling box is provided with a stirring paddle, and the calcium scaling box is also provided with a sodium carbonate inlet pipe and a calcium scale mixed liquid outlet pipe; the calcium scale separation box is provided with a calcium scale mixed liquid inlet pipe connected to the calcium scale mixed liquid outlet pipe, and a flocculant addition pipe is provided on the calcium scale mixed liquid inlet pipe; the calcium scale separation box is provided with an overflow section, an inclined tube sedimentation section and a mud discharge section from top to bottom, the overflow section is provided with an overflow weir, and is connected to the outlet regulating box through the decalcification wastewater inlet pipe; the inclined tube sedimentation section is provided with an inclined tube, and the mud discharge section is provided with a mud discharge pipe, one end of the mud discharge pipe extends into the calcium scale separation box and is set in full length along the water flow direction, and a plurality of mud discharge holes are provided on the mud discharge pipe in the calcium scale separation box; the outlet regulating box is provided with a hydrochloric acid addition pipe and a decalcification and magnesium wastewater outlet pipe, and the outlet regulating box is provided with a triple-blade stirring paddle.

5. A method for treating regenerated wastewater from a soft water station with zero discharge based on the system according to any one of claims 1 to 4, characterized in that: The steps include: 1) The regenerated wastewater enters the regulating tank and is adjusted to a pH value of 5-11. It is then heated to 35-45°C by heat exchange with a heat source. Hypochlorous acid and hydrochloric acid are then added to the regenerated wastewater to form a mixed aqueous solution, which is then fed into a vortex hydrodynamic cavitation device. 2) Under the action of water pressure and hydrocyclone rifling, the mixed aqueous solution enters the cyclone chamber at high speed in a swirling state. The pressure of the mixed aqueous solution entering the cyclone chamber suddenly decreases, and the flow rate increases. It quickly mixes with the high-pressure air ejected from the aeration holes on the aeration disk, and then collides with the high-speed rotating vortex hydrodynamic cavitation grinding disk, forming extreme turbulence and mechanical shear in the corrugated bowl and releasing a large amount of energy, thereby degrading organic matter in the mixed aqueous solution and achieving cavitation of the mixed aqueous solution. The cavitation water enters the wastewater tank below, and after the corrugated plate intercepts some water vapor, the remaining gas is discharged from the air outlet. The water outlet of the vortex hydrodynamic cavitation device enters the magnesium scale separation device through the post-cavitation wastewater outlet. 3) The effluent from the vortex hydrodynamic cavitation device first enters the magnesium scaling tank, and sodium hydroxide solution produced by the electrodialysis-electrolysis cell is added at the same time to maintain the pH value of the inlet water of the magnesium scaling tank between 9 and 12. The speed of the stirring paddle in the magnesium scaling tank is 100 to 1000 r / min, and the hydraulic retention time is 10 to 30 minutes. After the flocculant is added to the effluent from the magnesium scaling tank, it enters the magnesium scale separation tank with a hydraulic retention time of 0.5 to 3 hours. The separated magnesium scale is precipitated and discharged through the mud discharge pipe. The effluent from the magnesium scale separation tank enters the calcium scaling separation device. The effluent from the magnesium scale separation tank first enters the calcium scaling tank, where the pH value of the inlet water is adjusted to 12-14. Then, a sodium carbonate solution with a concentration of 8-10wt% is added. The speed of the stirring paddle in the calcium scaling tank is 100-1000r / min, and the hydraulic retention time is 5-20min. After flocculant is added to the effluent from the calcium scaling tank, it enters the calcium scale separation tank with a hydraulic retention time of 0.5-3h. The separated calcium scale is precipitated and discharged through the mud discharge pipe. The effluent from the calcium scale separation tank enters the effluent regulating tank. Hydrochloric acid is added to the effluent regulating tank while stirring to adjust the pH value of the wastewater to 7±0.

5. The effluent from the effluent regulating tank enters the electrocoagulation-microfiltration device; 4) The water from the outlet regulating box first enters the electric flocculation tank, and the current density of the electric flocculation tank is 0.3~1.0A / m 2 The plate spacing is 1.0-5.0 cm, and the hydraulic retention time is 20-45 min. The effluent from the electroflocculation tank is pressurized to 150-530 kPa by a circulating pump and then enters the microfiltration tank. The water output of the microfiltration tank is 150-550 L / m 2 h, the microfiltration water with turbidity less than 3 NTU enters the electrodialysis-electrolysis device; 5) Electrodialysis - Under the action of a 5-11 V external DC electric field, sodium ions in the water move through the semipermeable membrane to the cathode, and chloride ions move through the semipermeable membrane to the anode, forming concentrated liquid and fresh water, achieving the purpose of concentration; the fresh water is returned to the production site for use as recycled water or make-up water; the hydrogen produced at the cathode and the chlorine produced at the anode are collected, and when the hydrogen production rate is reduced to 20-25 m 3 / h, the sodium hydroxide produced by electrolysis is supplemented to the magnesium scale separation device and the calcium scale separation device, and the remaining sodium hydroxide solution is stored or sold.

6. A method for treating regenerated wastewater from a soft water station with zero discharge according to claim 5, characterized in that: In the step 2), the rotation speed of the vortex hydrodynamic cavitation grinding disc is 2000-6000 r / min.

7. A zero-discharge treatment method for regenerated wastewater from a soft water station according to claim 5, characterized in that: In step 3), the concentration of the sodium hydroxide solution generated by the electrodialysis-electrolysis cell is 5 to 10 mol / L.

8. A method for treating regenerated wastewater from a soft water station with zero discharge according to claim 5, characterized in that: In the step 3), the flocculant is a PAM flocculant with a mass percentage concentration of 1 to 3‰.

Images