An industrial water saving and emission reduction treatment method

Abstract

The application provides a boiler make-up water treatment and reverse osmosis discharge concentrated water treatment and reuse water-saving and emission reduction treatment method, which comprises the following steps: firstly, removing scale substances by adopting countercurrent regeneration mode in a fixed double-layer cation exchange softening device, then performing twice regeneration and layering by using regeneration liquid, then adding an alloy catalyst to remove scale, and then adding a scale inhibitor for scale prevention treatment; the treated water is used to cool the steam side water vapor of a membrane distillation hydrophobic membrane, and a heat pump technology is used to heat the water side inlet water of the membrane distillation; finally, the treated concentrated water enters a membrane distillation device, and the fresh water generated by the membrane distillation device is treated and enters a mixed bed or an electric desalting device to be used as boiler make-up water or circulating water supplement water. The water treatment method of the application uses membrane distillation and scale prevention technology, and has the advantages of good water quality, low salt content of the produced water, saved electric energy, recovered continuous discharge water, combined application of ion exchange softening, alloy catalyst scale prevention and high-efficiency scale inhibitor, greatly improved scale removal and scale prevention effect, and significantly improved concentration ratio and water utilization rate.

Description

Technical Field

[0001] This invention relates to an industrial water treatment method, and more particularly to a method for treating boiler feedwater and treating and reusing concentrated water from reverse osmosis for water conservation and emission reduction. Background Technology

[0002] Current industrial water treatment mainly employs reverse osmosis membrane technology, or even a full membrane process, namely pretreatment + ultrafiltration + reverse osmosis + electro-deionization (EDI). The main problem with this approach is its very low water utilization rate, typically only around 40%, less than half that of ion exchange methods, resulting in significant water waste. This is primarily due to the limitations of existing scale prevention methods. Current scale prevention methods are similar to those used in circulating water stabilization, involving the addition of scale inhibitors, and sometimes industrial hydrochloric acid (for circulating water, industrial sulfuric acid is commonly used). The concentration ratio of the concentrate is typically only 3-5 times, meaning about 25% of the water is wasted. Adding to this the wastewater from raw water pretreatment sludge discharge, filter backwashing, frequent acid and alkali washing during ultrafiltration, and other acid and alkaline wastewater discharge, the overall water utilization rate remains low, further contributing to water waste and higher water treatment costs.

[0003] Currently, the cost of municipal tap water is around 3 yuan per cubic meter. Adding to this the environmental protection requirements for discharge (typically, total dissolved solids in wastewater should be controlled at around 2000 mg / L), the sewage discharge fee for each cubic meter of wastewater exceeding these standards can reach as high as 2 yuan. Clearly, in many places, the existing reverse osmosis treatment method is no longer the most economical and effective. Therefore, seeking more energy-efficient, water-saving, and wastewater-reducing treatment technologies, as well as anti-scaling technologies, has become an urgent priority.

[0004] The existing scale inhibitor method for boiler feedwater film treatment has limitations in scale inhibition, which leads to the waste of precious freshwater resources and the risk of industrial wastewater discharge failing to meet standards. Summary of the Invention

[0005] To address the limitations of existing technologies, the present invention aims to provide a membrane distillation water treatment process and an industrial water saving and emission reduction method that combines double-layer ion exchange softening, forced-air decarbonization, alloy catalyst scale inhibition, and high-efficiency scale inhibitor.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for saving and reducing industrial water emissions includes the following steps:

[0008] Step 1: In a fixed double-layer cation exchange softening device, countercurrent regeneration is used to remove scale. Strong acid cation resin is filled in the lower part of the water chamber and weak acid cation resin is filled in the upper part of the water chamber, with no separation in between. During operation, the influent enters from the top of the softening device and the product water is discharged from the bottom of the softening device. The operating flow rate is 5-50 m / h.

[0009] Step 2: Remove carbon dioxide through a decarbonizer. After the resin becomes ineffective, use hydrochloric acid or sulfuric acid regeneration solution with a mass concentration of 0.01-5% at a flow rate of 5-30 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. Discharge the waste regeneration solution from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 1-60 minutes.

[0010] Step 3: Use hydrochloric acid, sulfuric acid or NaCl regeneration solution with a mass concentration of 0.1-10% to enter from the bottom of the softening device at a flow rate of 1-10 m / h. Slowly pass through the strong acid cation resin for regeneration. The waste regeneration solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device. Stop entering the regeneration solution when the mass concentration of the discharged acid or salt reaches 0.01-1%. Then rinse with water until the calcium hardness of the discharged water no longer decreases significantly or is close to that of the influent water. Stop water intake.

[0011] Step 4: The softened water obtained in Step 3 is first descaled by an alloy catalyst, and then a scale inhibitor is added for scale prevention treatment. The alloy catalyst scale prevention will further increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 0.1 to 50 times.

[0012] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to a surface temperature of 45-80°C using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 50-100°C, raising the water temperature by 5-50°C.

[0013] Step 6: The concentrated water after step 5 enters the membrane distillation unit. The desalinated water produced by the membrane distillation unit enters the mixed bed or electro-desalination treatment as boiler feedwater or circulating water supplement water.

[0014] Preferably, in step one, the height of both the strong acid cation exchange resin layer and the weak acid cation exchange resin layer in the double-layer cation exchange softening device is 100-5000 mm, and the volume ratio (height ratio) of the strong acid cation exchange resin to the weak acid cation exchange resin is 1:50-50:1.

[0015] Preferably, in step one, the calcium hardness of the produced water is controlled at 0.1–1000 μmol / L at the end of the failure period of the cation double-layer ion exchange softening device, and the treated water volume accounts for 1–100% of the total water entering the membrane distillation in step six.

[0016] Preferably, the decarbonizer in step two uses a blower to decarbonize, and the carbon dioxide content after decarbonization is less than 10 mg / L.

[0017] Preferably, the scale inhibitor in step four is an organophosphorus composite scale inhibitor.

[0018] Preferably, the membrane used in step six is ​​a hydrophobic membrane made of polytetrafluoroethylene.

[0019] Preferably, the membrane flux of the membrane distillation apparatus in step six is ​​0.1–100 L / m³. 2 h, water side temperature 10~200℃.

[0020] Preferably, in step six, the membrane distillation apparatus has an inlet water pressure of 0.01–1 MPa, a pH value of 0–14, a concentration ratio of 2–200, a dissolved solids content in the discharged concentrate of no more than 300,000 mg / L, a steam side temperature of 5–180°C, and a pressure of 0.001–0.5 MPa.

[0021] Preferably, the water entering the membrane distillation unit in step six can also be recycled from existing reverse osmosis concentrate. First, an antiscalant is added, and then it is treated with an alloy catalyst and a double-layer ion exchange softening device. The order of the antiscaling methods can be arbitrarily combined, and the pH value of the blower decarbonization is less than 8.5.

[0022] This invention also provides an industrial water-saving and emission-reduction treatment method for application in various water treatment processes, including boiler and circulating water makeup water, seawater desalination, circulating cooling water discharge, reverse osmosis concentrated water, and desulfurization high-salt wastewater.

[0023] The present invention has the following beneficial effects:

[0024] (1) The membrane distillation and scale prevention technology of the present invention replaces the existing water treatment method mainly based on reverse osmosis. The water produced is of good quality, and the salt content (usually measured by conductivity) is less than 1% of that of reverse osmosis. The water utilization rate is high, usually increasing by about 50%. It saves about 90% of electricity and reduces wastewater discharge by about 80%.

[0025] (2) This invention replaces conventional reverse osmosis with membrane distillation technology, which can utilize low-grade industrial waste heat such as boiler continuous drainage and heat pump technology, saving electricity and recovering continuous drainage; through the combined application of ion exchange softening, alloy catalyst scale prevention and high-efficiency scale inhibitor, the scale removal and scale inhibition effect can be greatly improved, and the concentration ratio and water utilization rate can be significantly improved.

[0026] (3) This invention can significantly improve the quality of produced water, concentration ratio, and freshwater yield, reduce water production costs and energy consumption, reduce wastewater discharge, and achieve the goals of energy saving, water saving, emission reduction and water treatment cost reduction. It can even extract beneficial substances from wastewater as industrial raw materials, turning waste into treasure, and has a very broad market prospect. Detailed implementation method:

[0027] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0028] Example 1

[0029] A method for saving and reducing industrial water emissions includes the following steps:

[0030] Step 1 involves removing scale buildup in a fixed double-layer cation exchange softening unit using countercurrent regeneration. Strong acid cation exchange resin is packed in the lower part of the water chamber, and weak acid cation exchange resin is packed in the upper part, with no separation in between. During operation, influent enters from the top of the softening unit, and permeate exits from the bottom, with an operating flow rate of 5 m / h. The strong acid cation exchange resin layer is 100 mm high, and the weak acid cation exchange resin layer is 5000 mm high, with a volume ratio (height ratio) of 1:50. The endpoint control for the double-layer cation exchange softening unit is a calcium hardness of 0.1–1 μmol / L in the permeate, and the treated water volume accounts for 1% of the total water entering the membrane distillation process in Step 6.

[0031] Step 2: Remove carbon dioxide by blowing air through the decarbonizer. After decarbonization, the carbon dioxide content is less than 10 mg / L. After the resin is exhausted, use 0.05% hydrochloric acid regeneration solution at a flow rate of 5 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. The waste regeneration solution is discharged from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 3 minutes.

[0032] Step 3: Use a 0.1% mass concentration regenerated solution to enter from the bottom of the softening device at a flow rate of 1 m / h and slowly pass through the strong acid cation resin for regeneration. The waste regenerated solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device. Stop entering the regenerated solution when the mass concentration of the effluent acid reaches 0.02%. Then rinse with water until the calcium hardness of the effluent no longer decreases significantly or is close to that of the influent. Stop water intake.

[0033] Step four involves first passing the softened water obtained in step three through alloy catalyst descaling, and then adding an organophosphorus composite scale inhibitor for scale prevention treatment. The alloy catalyst scale prevention will further increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 0.3 times.

[0034] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to 45°C by surface heating using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 50°C, raising the water temperature by 5-10°C.

[0035] Step Six: The concentrated water from Step Five enters the membrane distillation unit. The membrane used is a hydrophobic membrane made of polytetrafluoroethylene, with a membrane flux of 0.2 L / m³. 2 The water side temperature is 10-20℃, the inlet pressure is 0.02MPa, the pH value is 0.6, the concentration ratio is 2, the dissolved solids in the discharged concentrate are no more than 300,000mg / L, the steam side temperature is 5℃, and the pressure is 0.003Mpa. The fresh water produced by the membrane distillation unit enters the mixed bed or electrostatic desalination treatment as boiler feedwater or circulating water supplement water. The water entering the membrane distillation unit can also recover the existing reverse osmosis concentrate. First, an antiscalant is added, and then an alloy catalyst and a double-layer ion exchange softening device are used for treatment. The order of the antiscaling methods can be arbitrarily combined. The pH value of the blower decarbonization is less than 8.5.

[0036] Example 2

[0037] A method for saving and reducing industrial water emissions includes the following steps:

[0038] Step 1 involves removing scale buildup using a counter-current regeneration method within a fixed double-layer cation exchange softening unit. Strong acid cation exchange resin is packed in the lower part of the water chamber, and weak acid cation exchange resin is packed in the upper part, with no separation in between. During operation, influent enters from the top of the softening unit, and permeate exits from the bottom, with an operating flow rate of 10 m / h. The strong acid cation exchange resin layer is 500 mm high, and the weak acid cation exchange resin layer is 2500 mm high, with a volume ratio (height ratio) of 1:5. The failure endpoint of the double-layer cation exchange softening unit is controlled to produce permeate with a calcium hardness of 1–10 μmol / L, and the treated water volume accounts for 5% of the total water entering the membrane distillation process in Step 6.

[0039] Step 2: Remove carbon dioxide by blowing air through the decarbonizer. After decarbonization, the carbon dioxide content is less than 10 mg / L. After the resin is exhausted, use 0.1% sulfuric acid regeneration solution at a flow rate of 10 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. The waste regeneration solution is discharged from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 10 minutes.

[0040] Step 3: Use 1% sulfuric acid regeneration solution at a flow rate of 2 m / h to enter from the bottom of the softening device and slowly pass through the strong acid cation resin for regeneration. The waste regeneration solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device. Stop entering the regeneration solution when the mass concentration of the effluent acid reaches 0.1%. Then rinse with water until the calcium hardness of the effluent no longer decreases significantly or is close to that of the influent. Stop water intake.

[0041] Step four involves first passing the softened water obtained in step three through alloy catalyst descaling, and then adding an organophosphorus composite scale inhibitor for scale prevention treatment. The alloy catalyst scale prevention will further increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 2 times.

[0042] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to 50°C by surface heating using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 60°C, raising the water temperature by 10-15°C.

[0043] Step Six: The concentrated water from Step Five enters the membrane distillation unit. The membrane used is a hydrophobic membrane made of polytetrafluoroethylene, with a membrane flux of 3 L / m³. 2 The system operates as follows: water-side temperature 30℃, inlet pressure 0.1MPa, pH 1.8, concentration ratio 10, dissolved solids in the discharged concentrate not exceeding 300,000 mg / L, steam-side temperature 20℃, pressure 0.07 MPa; the freshwater produced by the membrane distillation unit enters the mixed bed or electrostatic desalination treatment as boiler feedwater or circulating water supplement water; the water entering the membrane distillation unit can also recover existing reverse osmosis concentrate, first adding scale inhibitor, then using alloy catalyst and cation double-layer ion exchange softening device, the scale inhibition method and its sequence can be arbitrarily combined, and the pH value of the blower decarbonization is less than 8.5.

[0044] Example 3

[0045] A method for saving and reducing industrial water emissions includes the following steps:

[0046] Step 1 involves removing scale buildup using a counter-current regeneration method within a fixed double-layer cation exchange softening device. Strong acid cation exchange resin is packed in the lower part of the water chamber, and weak acid cation exchange resin is packed in the upper part, with no separation in between. During operation, influent enters from the top of the softening device, and permeate exits from the bottom, with an operating flow rate of 20 m / h. The height of both the strong acid and weak acid cation exchange resin layers is 1000 mm, and the volume ratio (height ratio) of both is 1:1. The endpoint for the double-layer cation exchange softening device's failure is controlled to produce water with a calcium hardness of 10–100 μmol / L, and the treated water volume accounts for 10% of the total water entering the membrane distillation process in Step 6.

[0047] Step 2: Remove carbon dioxide by blowing air through the decarbonizer. After decarbonization, the carbon dioxide content is less than 10 mg / L. After the resin is exhausted, use 1.2% hydrochloric acid regeneration solution at a flow rate of 15 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. The waste regeneration solution is discharged from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 20 minutes.

[0048] Step 3: Use 3% NaCl regeneration solution at a flow rate of 4 m / h to enter from the bottom of the softening device and slowly pass through the strong acid cation resin for regeneration. The waste regeneration solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device. Stop entering the regeneration solution when the mass concentration of the effluent salt reaches 0.3%. Then rinse with water until the calcium hardness of the effluent no longer decreases significantly or is close to that of the influent. Stop water intake.

[0049] Step 4: The softened water obtained in Step 3 is first descaled by alloy catalyst, and then an organic phosphorus composite scale inhibitor is added for scale prevention treatment. The alloy catalyst scale prevention will increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 10 times.

[0050] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to 60°C by surface heating using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 70°C, raising the water temperature by 15-20°C.

[0051] Step Six: The concentrated water from Step Five enters the membrane distillation unit. The membrane used is a hydrophobic membrane made of polytetrafluoroethylene, with a membrane flux of 10 L / m³. 2The system operates as follows: water side temperature 70℃, inlet pressure 0.3MPa, pH 3.6, concentration ratio 40, dissolved solids in the discharged concentrate not exceeding 300,000 mg / L, steam side temperature 50℃, pressure 0.15MPa; the freshwater produced by the membrane distillation unit enters the mixed bed or electrostatic desalination treatment as boiler feedwater or circulating water supplement water; the water entering the membrane distillation unit can also recover existing reverse osmosis concentrate, first adding scale inhibitor, then using alloy catalyst and cation double-layer ion exchange softening device, the scale inhibition method and its sequence can be arbitrarily combined, and the pH value of the blower decarbonization is less than 8.5.

[0052] Example 4

[0053] A method for saving and reducing industrial water emissions includes the following steps:

[0054] Step 1 involves removing scale buildup in a fixed double-layer cation exchange softening unit using countercurrent regeneration. Strong acid cation exchange resin is packed in the lower part of the water chamber, and weak acid cation exchange resin is packed in the upper part, with no separation in between. During operation, influent enters from the top of the softening unit, and permeate exits from the bottom, with an operating flow rate of 30 m / h. The strong acid cation exchange resin layer is 3000 mm high, and the weak acid cation exchange resin layer is 600 mm high, with a volume ratio (height ratio) of 5:1. The endpoint for the double-layer cation exchange softening unit's failure is controlled to produce permeate with a calcium hardness of 100–300 μmol / L, and the treated water volume accounts for 30% of the total water entering the membrane distillation process in Step 6.

[0055] Step 2: Remove carbon dioxide by blowing air through the decarbonizer. After decarbonization, the carbon dioxide content is less than 10 mg / L. After the resin is exhausted, use 2.5% sulfuric acid regeneration solution at a flow rate of 20 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. The waste regeneration solution is discharged from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 35 minutes.

[0056] Step 3: Use 5% hydrochloric acid regeneration solution at a flow rate of 6 m / h to enter from the bottom of the softening device and slowly pass through the strong acid cation resin for regeneration. The waste regeneration solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device. Stop entering the regeneration solution when the mass concentration of the effluent acid reaches 0.5%. Then rinse with water until the calcium hardness of the effluent no longer decreases significantly or is close to that of the influent. Stop water intake.

[0057] Step four involves first passing the softened water obtained in step three through alloy catalyst descaling, and then adding an organophosphorus composite scale inhibitor for scale prevention treatment. The alloy catalyst scale prevention will further increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 25 times.

[0058] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to 70°C by surface heating using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 85°C, raising the water temperature by 20-30°C.

[0059] Step Six: The concentrated water from Step Five enters the membrane distillation unit. The membrane used is a hydrophobic membrane made of polytetrafluoroethylene, with a membrane flux of 30 L / m³. 2 The system operates as follows: water-side temperature 120℃, inlet pressure 0.6MPa, pH 6.9, concentration ratio 100, dissolved solids in the discharged concentrate not exceeding 300,000 mg / L, steam-side temperature 90℃, pressure 0.25 MPa. The freshwater produced by the membrane distillation unit is treated in a mixed bed or electrostatic desalination system as boiler feedwater or circulating water. The water entering the membrane distillation unit can also be recycled from existing reverse osmosis concentrate. A scale inhibitor is first added, followed by treatment with an alloy catalyst and a double-layer ion exchange softening device. The order of scale inhibition methods can be arbitrarily combined. The pH value of the blower decarbonization is less than 8.5.

[0060] Example 5

[0061] A method for saving and reducing industrial water emissions includes the following steps:

[0062] Step 1 involves removing scale buildup using a counter-current regeneration method within a fixed double-layer cation exchange softening unit. Strong acid cation exchange resin is packed in the lower part of the water chamber, and weak acid cation exchange resin is packed in the upper part, with no separation in between. During operation, influent enters from the top of the softening unit, and permeate exits from the bottom, with an operating flow rate of 40 m / h. The height of both the strong acid and weak acid cation exchange resin layers is 2000 mm, and the volume ratio (height ratio) of both is 1:1. The endpoint for the double-layer cation exchange softening unit's failure is controlled to produce water with a calcium hardness of 300–600 μmol / L, and the treated water volume accounts for 70% of the total water entering the membrane distillation process in Step 6.

[0063] Step 2: Remove carbon dioxide by blowing air through the decarbonizer. After decarbonization, the carbon dioxide content is less than 10 mg / L. After the resin is exhausted, use 3.7% hydrochloric acid regeneration solution at a flow rate of 25 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. The waste regeneration solution is discharged from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 50 minutes.

[0064] Step 3: Use 7.4% sulfuric acid regeneration solution to enter from the bottom of the softening unit at a flow rate of 8 m / h. Slowly pass through the strong acid cation resin for regeneration. The waste regeneration solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening unit. Stop entering the regeneration solution when the mass concentration of the effluent acid reaches 0.7%. Then rinse with water until the calcium hardness of the effluent no longer decreases significantly or is close to that of the influent. Stop water intake.

[0065] Step 4: The softened water obtained in Step 3 is first descaled by alloy catalyst, and then an organic phosphorus composite scale inhibitor is added for scale prevention treatment. The alloy catalyst scale prevention will increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 40 times.

[0066] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to 75°C by surface heating using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 90°C, raising the water temperature by 30-40°C.

[0067] Step Six: The concentrated water from Step Five enters the membrane distillation unit. The membrane used is a hydrophobic membrane made of polytetrafluoroethylene, with a membrane flux of 60 L / m³. 2 The system operates as follows: water side temperature 150℃, inlet pressure 0.8MPa, pH 10.6, concentration ratio 150, dissolved solids in the discharged concentrate not exceeding 300,000 mg / L, steam side temperature 150℃, pressure 0.35 MPa; the freshwater produced by the membrane distillation unit enters the mixed bed or electrostatic desalination treatment as boiler feedwater or circulating water supplement water; the water entering the membrane distillation unit can also recover existing reverse osmosis concentrate, first adding scale inhibitor, then using alloy catalyst and cation double-layer ion exchange softening device, the scale inhibition method and its sequence can be arbitrarily combined, and the pH value of the blower decarbonization is less than 8.5.

[0068] Example 6

[0069] A method for saving and reducing industrial water emissions includes the following steps:

[0070] Step 1 involves removing scale buildup in a fixed double-layer cation exchange softening unit using countercurrent regeneration. Strong acid cation exchange resin is packed in the lower part of the water chamber, and weak acid cation exchange resin is packed in the upper part, with no separation in between. During operation, influent enters from the top of the softening unit, and permeate exits from the bottom, with an operating flow rate of 50 m / h. The strong acid cation exchange resin layer is 4000 mm high, and the weak acid cation exchange resin layer is 200 mm high, with a volume ratio (height ratio) of 20:1. The failure endpoint of the double-layer cation exchange softening unit is controlled to produce permeate with a calcium hardness of 300–1000 μmol / L, and the treated water volume accounts for 90% of the total water entering the membrane distillation process in Step 6.

[0071] Step 2: Remove carbon dioxide by blowing air through a decarbonizer. After decarbonization, the carbon dioxide content is less than 10 mg / L. After the resin becomes ineffective, use 5% sulfuric acid regeneration solution at a flow rate of 30 m / h to enter from the bottom of the softening device or the interface between the two resins. Pre-regenerate and stratify the entire resin layer or the weak acid cation resin layer. The waste regeneration solution is discharged from the top of the softening device. After the methyl orange acidity appears in the drainage, let it stand for 60 minutes.

[0072] Step 3: Use 10% NaCl regeneration solution at a flow rate of 10 m / h to enter from the bottom of the softening device and slowly pass through the strong acid cation resin for regeneration. The waste regeneration solution is discharged from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device. Stop entering the regeneration solution when the mass concentration of the effluent salt reaches 1%. Then rinse with water until the calcium hardness of the effluent no longer decreases significantly or is close to that of the influent. Stop water intake.

[0073] Step four involves first passing the softened water obtained in step three through alloy catalyst descaling, and then adding an organophosphorus composite scale inhibitor for scale prevention treatment. The alloy catalyst scale prevention will further increase the concentration ratio of the water that has been concentrated to saturation after scale inhibitor or softening treatment by 50 times.

[0074] Step 5: The water treated in Step 4 is first used to cool the steam on the steam side of the membrane distillation hydrophobic membrane. Then, the water is indirectly heated to 80°C by surface heating using boiler drain, flue gas, steam, or electricity. The cooled drain, flue gas, or steam hydrophobic water enters the electrostatic desalination or mixed bed deep desalination system as boiler feedwater or directly enters the circulating water system as supplementary water. Then, heat pump technology is used to heat the water on the membrane distillation water side to 100°C, raising the water temperature by 40-50°C.

[0075] Step Six: The concentrated water from Step Five enters the membrane distillation unit. The membrane used is a hydrophobic membrane made of polytetrafluoroethylene, with a membrane flux of 100 L / m³. 2The system operates as follows: water side temperature 200℃, inlet pressure 1MPa, pH 13.4, concentration ratio 200, dissolved solids in the discharged concentrate not exceeding 300,000 mg / L, steam side temperature 180℃, pressure 0.5 MPa; the freshwater produced by the membrane distillation unit enters the mixed bed or electrostatic desalination treatment as boiler feedwater or circulating water supplement water; the water entering the membrane distillation unit can also recover existing reverse osmosis concentrate, first adding scale inhibitor, then using alloy catalyst and cation double-layer ion exchange softening device, the scale inhibition method and its sequence can be arbitrarily combined, and the pH value of the blower decarbonization is less than 8.5.

[0076] Application Case 1:

[0077] The boiler feedwater source for a thermal power plant in Zhejiang Province is municipal tap water, with a water fee of 2.80 yuan / m³. 3 The water treatment process adopts a full membrane method, namely ultrafiltration + primary RO + secondary RO + EDI. In order to save water and reduce water treatment costs and water bills, it was decided to treat and reuse the concentrated water discharged from the primary RO stage.

[0078] The specific implementation method is as follows: First, the primary RO wastewater undergoes 100% softening treatment with weak acid resin, with a designed operating flow rate of 15 m / h. The calcium hardness of the product water is controlled at 5 μmol / L. After resin failure, a one-step counter-current regeneration and backwashing method is used to complete the process. The softened water then undergoes decarbonization via a blower, resulting in a carbon dioxide content below 5 mg / L. Finally, the water treated with an alloy catalyst is heated to 60°C using boiler wastewater, and then further heated to 95°C using heat pump technology before entering the membrane distillation unit. The membrane distillation process handles 20 m³ of water. 3 / h, concentration ratio 20, water recovery rate 95%, freshwater flow rate 19m 3 / h, concentrated wastewater discharge rate 1m 3 The per-hour water conductivity is 6.5 μS / cm. After cooling, the continuous wastewater and membrane distillation desalination water are treated by EDI and used as boiler makeup water. It is estimated that the entire investment cost can be recovered in three years.

[0079] Application Case 2:

[0080] A large power plant in Shandong charges 7 yuan / m³ for water. 3 The dissolved solids in the concentrated wastewater exceeded the standard, and the sewage discharge fee was 2 yuan / m³. 3 The boiler feedwater treatment system is designed using a full membrane method, with a designed output of 100m³. 3 / h×2, with a first-stage RO concentration ratio of 4. Membrane distillation and anti-scaling technology are used to recover the first-stage RO concentrate, with a designed treatment capacity of 50m³ / h. 3 / h, concentration ratio 10, freshwater production 45m³ 3 / h, concentrated wastewater discharge reduced to 5m 3The per-hour water production has a conductivity of 4.5 μS / cm. After EDI treatment, the produced water is recycled as boiler makeup water. According to calculations, the cost of the modification can be recovered within one year.

[0081] The above embodiments and application examples further illustrate the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., that can be made without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An industrial water saving and emission reduction treatment method, characterized in that, It comprises the following steps: Step one: remove the scale-forming substances in the fixed double-layer cation exchange softening device by countercurrent regeneration, the strong acid cation resin is filled in the lower part of the water chamber and the weak acid cation resin is filled in the upper part of the water chamber, there is no isolation in the middle, the water enters from the top of the softening device during operation, and the produced water is discharged from the bottom of the softening device, the running speed is 5-50 m / h; Step two: remove the carbon dioxide in the produced water of step one by a decarbonator, when the resin is invalid, use 0.01%-5% hydrochloric acid or sulfuric acid regeneration solution to enter from the bottom of the softening device or the interface between the two kinds of resins at a flow rate of 5-30 m / h, and carry out pre-regeneration and layering by passing through the entire resin layer or the weak acid cation resin layer, the waste regeneration solution is discharged from the top of the softening device, and after the water discharge appears methyl orange acidity, it is soaked for 1-60 minutes; Step three: use 0.1%-10% hydrochloric acid, sulfuric acid or NaCl regeneration solution to enter from the bottom of the softening device at a flow rate of 1-10 m / h, slowly pass through the strong acid cation resin for regeneration, and discharge the waste regeneration solution from the interface between the weak acid cation resin and the strong acid cation resin in the middle of the softening device, stop entering the regeneration solution when the mass concentration of acid or salt in the water discharge reaches 0.01%-1%, and then wash with water until the calcium hardness of the water discharge is no longer obviously reduced or is close to the calcium hardness of the water inlet; Step four: the softened water obtained in step two is first subjected to alloy catalyst descaling, and then a scale inhibitor is added for scale prevention treatment, the alloy catalyst scale prevention is used to increase the concentration ratio of the water after softening treatment by 0.1-50 times to reach the saturation state; Step five: the water treated in step four is first used to cool the water vapor on the steam side of the hydrophobic membrane of the membrane distillation, and then the water is indirectly heated to a water temperature of 45-80℃ by a boiler connected with water, flue gas, steam or electricity, the cooled water, flue gas or steam hydrophobic enters the electrodeionization or mixed bed deep desalination as boiler makeup water or directly enters the circulating water system as makeup water, and the heat pump technology is used to heat the water inlet of the water side of the membrane distillation to 50-100℃, so that the water temperature is increased by 5-50℃; Step six: the concentrated water treated in step five enters the membrane distillation device, and the produced fresh water enters the mixed bed or electrodeionization treatment as boiler makeup water or circulating water makeup water.

2. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, In step one, the height of the strong acid cation resin layer and the height of the weak acid cation resin layer in the double-layer cation exchange softening device are both 100-5000 mm, and the volume ratio of the strong acid cation resin to the weak acid cation resin, i.e. the height ratio, is 1:50-50:

1.

3. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, In step one, the calcium hardness of the produced water is controlled to be 0.1-1000 μmol / L at the end of the operation of the double-layer cation exchange softening device, and the amount of the treated water accounts for 1-100% of the total water amount entering the membrane distillation in step six.

4. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, The decarbonator in step two uses air blowing to remove carbon dioxide, and the carbon dioxide content after decarbonization is less than 10 mg / L.

5. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, The scale inhibitor in step four is an organic phosphorus-based composite scale inhibitor.

6. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, The membrane used in the membrane distillation device in step six is a hydrophobic membrane made of polytetrafluoroethylene.

7. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, The membrane flux of the step six membrane distillation device is 0.1-100 L / m 2 h, water side temperature 10-200°C.

8. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, The water pressure of the step six membrane distillation device is 0.01-1 MPa, the pH value is 0-14, the concentration ratio is 2-200, the dissolved solid of the discharged concentrated water is not more than 300000 mg / L, the vapor side temperature is 5-180 ℃, and the pressure is 0.001-0.5 MPa.

9. The industrial water saving and emission reduction treatment method according to claim 1, characterized in that, The water entering the membrane distillation device in the step six can also be the existing reverse osmosis concentrated water, a scale inhibitor is added first, and then an alloy catalyst and a double-layer cation exchange softening device are used for treatment, and the scale inhibition mode can be arbitrarily combined, and the air decarburization pH value is less than 8.

5.

10. The method according to any one of claims 1-9 is applied in various water treatments of boiler and circulating water make-up water, seawater desalination, circulating cooling water blowdown water, reverse osmosis discharge concentrated water and desulfurization high-salt wastewater.