Cooperative treatment system for drainage of two demineralized water production lines

Abstract

The invention belongs to the field of water treatment, particularly relates to a drainage cooperative treatment system for two desalted water production lines, and provides a drainage cooperative recycling system and a recycling method for the working condition that an ion exchange process desalted water production line and a reverse osmosis membrane process desalted water production line run in parallel. Most of positive and negative washing drainage water in the two production lines is subjected to microfiltration treatment and then is used as raw water of the reverse osmosis membrane process desalted water production line, so that high-efficiency reuse of the sewage water is realized, the consumption of the raw water, namely fresh water, of the two desalted water production lines is greatly reduced, the sewage yield is also reduced, and the yield of the desalted water is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of water treatment, and particularly relates to a collaborative treatment system for drainage of two desalted water production lines. BACKGROUND

[0002] As a process industry with high energy consumption and high resource consumption, the stable and efficient operation of copper smelting highly depends on a large amount of high-quality industrial water. Desalted water (demineralized water) is widely used in many key links of smelting, such as waste heat boiler make-up water, important equipment cooling water, process water, etc., because of its extremely low salt content and impurity content. In a word, desalted water is an indispensable medium for ensuring equipment safety, improving thermal efficiency and guaranteeing product quality.

[0003] The ion exchange method and the reverse osmosis method (membrane exchange method) are commonly used in the prior art and have high cost performance and stability. The ion exchange method is mainly a process of a multi-medium filter + a positive bed + a negative bed + a mixed bed, which gradually removes the dissolved ions in water to finally obtain desalted water meeting the standards. The general process of the reverse osmosis method is a multi-medium filter + ultrafiltration + reverse osmosis + a mixed bed, which realizes the physical separation of water molecules and dissolved salts by using the selective permeability of the membrane.

[0004] However, a certain amount of concentrated water or positive and reverse washing drainage is generated in the production of desalted water by the ion exchange process and the reverse osmosis process. Therefore, the actual water production rate of desalted water by the two processes is generally 50-70%, and it will gradually decrease with the aging of the resin and the membrane, that is, 30%-50% or even more concentrated water or positive and reverse washing drainage will be actually generated. These waters have high turbidity, high conductivity and high hardness, and are difficult to recycle without treatment.

[0005] Therefore, how to treat and recycle the concentrated water and the positive and reverse washing drainage of the desalted water production line is an important subject for technical personnel to continue to study. SUMMARY

[0006] The purpose of the present application is to provide a collaborative treatment system for drainage of two desalted water production lines, which recycles the concentrated water and the positive and reverse washing drainage generated in the two desalted water production lines into the system to improve the desalted water production rate.

[0007] To achieve the above purpose, the technical solution adopted by the present application is as follows: a collaborative treatment system for drainage of two desalted water production lines, comprising a first desalted water production line formed by a first raw water tank, a first multi-medium filter, a positive bed, a negative bed, a first mixed bed and a first desalted water tank connected in series, and a second desalted water production line formed by a second raw water tank, a second multi-medium filter, an ultrafiltration device, a reverse osmosis device, a second mixed bed and a second desalted water tank connected in series.

[0008] During the regeneration process of the equipment in the first demineralized water production line, the backwash drainage from the first multi-media filter, the backwash drainage from the cation exchange bed, the backwash drainage from the anion exchange bed, and the forward wash drainage from the first mixed bed are treated by the microfiltration device and then enter the second raw water tank. During the regeneration process of the equipment in the second demineralized water production line, the backwash drainage from the second multi-media filter, the backwash drainage from the ultrafiltration device, and the forward wash drainage from the second mixed bed are treated by the microfiltration device and then enter the second raw water tank.

[0009] The technical solution of this invention provides a wastewater co-recycling system and recycling method for the parallel operation of ion exchange demineralized water production lines and reverse osmosis membrane demineralized water production lines. Most of the forward and reverse washing wastewater from the two production lines is treated by microfiltration and used as raw water for the reverse osmosis membrane demineralized water production line, realizing efficient reuse of wastewater. This greatly reduces the amount of raw water (i.e., fresh water) used by the two demineralized water production lines, reduces wastewater production, and increases the yield of demineralized water.

[0010] After a period of operation, multi-media filters accumulate a large amount of suspended solids, colloids, organic matter, and other impurities in their filter media, leading to: 1. Increased head loss, greater flow resistance, and higher inlet and outlet pressure differential; 2. Decreased filtration efficiency: impurities may penetrate the filter media, affecting the quality of the effluent (e.g., increased SDI value); 3. Reduced water production: under constant inlet pressure, the effluent flow rate decreases. To restore the filter media's ability to trap contaminants, regular backwashing and forward washing are necessary to flush out the trapped contaminants.

[0011] Backwashing is the most crucial step in the cleaning process. Water enters from the bottom of the filter, flows upward through the filter media layer, and finally exits from the top. The purpose of backwashing is to break up and loosen the compacted filter media layer that has been compressed during operation. Using the shear force of the water flow and the friction between the filter media particles, contaminants adhering to the surface of the filter media are peeled off. After backwashing, filter media with higher density and larger particle size (such as anthracite) settle quickly and remain on the upper layer; filter media with lower density and smaller particle size (such as quartz sand) settle slowly and remain on the lower layer. This restores the ideal "coarse on top, fine on bottom" filtration structure, forming an effective "filter cake" filtration effect.

[0012] After backwashing, the filter bed is completely loose, and the water contains a large amount of dirt that has just been washed off the filter media. If it is put into operation directly, the effluent quality will be extremely poor. Therefore, forward washing is required, with the water flow direction from top to bottom, the same as the normal operating direction. The purpose is to recompact the loose filter media after backwashing, forming a stable filter bed, and to flush away the wastewater remaining in the filter space and between the filter media after backwashing, so that the effluent quality is restored to a qualified standard, preparing for the next step of normal operation.

[0013] The forward and backwashing of cation exchange beds are explained in detail. These are two crucial maintenance steps in the operation cycle of a cation exchange bed, directly affecting its exchange capacity and effluent quality. A complete working cycle of a cation exchange bed is: Operation → Failure → Backwashing → Regeneration → Forward Washing → Operation. Backwashing is performed when the cation exchange bed fails (effluent Na+). + After the content exceeds the standard or the acidity at the outlet decreases, before regeneration (acid injection), the resin layer of the cation bed is pressed very tightly by the water flow during operation. Backwashing can loosen and expand it, creating good conditions for subsequent regeneration, ensuring that the regenerated acid can be evenly distributed and fully contact all resins, and can remove suspended solids, resin debris and other contaminants trapped above the resin layer during operation. If not removed, these impurities will form "channels" and affect the regeneration and operation effect.

[0014] After the cation exchange bed regeneration is completed (after acid replacement), the resin bed and container space are filled with residual dilute acid and regeneration products (such as CaCl2 and MgCl2 solutions). This must be thoroughly rinsed out; otherwise, the effluent will be acidic and contain high levels of salt, making it unqualified. Therefore, a forward wash (with water flowing in the same direction as during operation) is required to recompact the loose resin layer after backwashing and regeneration, forming a stable exchange layer. This will restore the pH and conductivity of the effluent to an acceptable range, preparing for a smooth start-up.

[0015] The effects of washing both forwards and backwards in genital and mixed-bed beds are the same as those in genital beds. Attached Figure Description

[0016] Figure 1 This invention relates to a coordinated treatment system for wastewater from two demineralized water production lines. The thick solid arrows indicate the direction of the two demineralized water production lines; the dashed arrows indicate the direction of forward washing wastewater; the double arrows indicate the direction of backwash water or wastewater; and the single arrows indicate the direction of intermediate wastewater circulation. The forward and backwash water (not shown) is water from the first or second raw water tank; the forward and backwash wastewater (not shown) is not treated in this application's treatment system. Detailed Implementation

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] A collaborative treatment system for wastewater from two demineralized water production lines is characterized by comprising a first demineralized water production line consisting of a first raw water tank 101, a first multi-media filter 102, a cation exchange bed 103, an anion exchange bed 104, a first mixed bed 105, and a first demineralized water tank 106 connected in series, and a second demineralized water production line consisting of a second raw water tank 201, a second multi-media filter 202, an ultrafiltration device 203, a reverse osmosis device 205, a second mixed bed 206, and a second demineralized water tank 208 connected in series.

[0019] During the regeneration process of the equipment in the first demineralized water production line, the forward and backwash drainage of the first multi-media filter 102, the backwash drainage of the cation exchange bed 103, the backwash drainage of the anion exchange bed 104, and the forward wash drainage of the first mixed bed 105 are treated by the microfiltration device 302 and then enter the second raw water tank 201; during the regeneration process of the equipment in the second demineralized water production line, the forward and backwash drainage of the second multi-media filter 202, the backwash drainage of the ultrafiltration device 203, and the forward wash drainage of the second mixed bed 206 are treated by the microfiltration device 302 and then enter the second raw water tank 201.

[0020] Since the second demineralized water production line is a reverse osmosis membrane demineralized water production line, its requirements for raw water are relatively lower than those of the first demineralized water production line (ion exchange demineralized water production line). Most of the forward and reverse wash water in the two production lines is treated by microfiltration to remove suspended solids, particulate matter, colloids and other impurities. The quality of the effluent can meet the influent requirements of the second demineralized water production line, which greatly alleviates the problem of large fresh water consumption and greatly improves the yield of demineralized water.

[0021] The concentrated effluent from reverse osmosis unit 205 is used as backwash water for the first and second multi-media filters 102 and 202. The concentrated effluent from the second production line is used as backwash water for two multi-media filters with lower water quality requirements, further reducing wastewater discharge and finding a new use for the concentrated effluent.

[0022] The concentrate produced by the reverse osmosis unit 205 is treated by the high-pressure reverse osmosis unit 401 and then used as flushing water for the microfiltration unit 302 or recycled back into the reverse osmosis unit 205. The concentrate produced by the reverse osmosis unit 205 can be led out to two downstream pipelines: it preferentially enters the first pipeline, which serves as backwash water for the two multi-media filters; if there is any concentrate remaining, it enters the second pipeline, the high-pressure reverse osmosis unit 401, where the treated water is used as flushing water for the microfiltration unit 302 or recycled back into the reverse osmosis unit 205.

[0023] A heat exchanger 502 is installed between the second raw water tank 201 and the downstream second multi-media filter 202 to exchange heat between the water outlet of the second raw water tank 201 and at least one of the following: boiler wastewater, cooling condensate from the power generation unit, steam condensate return water from the pipeline network, and steam condensate from the dryer.

[0024] Since the second demineralized water production line already has a device for heating the raw water—specifically, a raw water heating device 210 is installed between the second raw water tank 201 and the second multi-media filter 202—and the aforementioned heat exchanger 502 is located between the second raw water tank 201 and the raw water heating device 210, the high-temperature wastewater within the plant area is used to heat the raw water for demineralization, thereby accelerating the operation of the entire production line, improving the demineralized water production efficiency, and reducing the steam consumption of the raw water heating device 210.

[0025] Furthermore, this system can also reuse the above-mentioned wastewater from the plant area, namely, at least one of the boiler wastewater, power generation unit cooling condensate, pipeline steam condensate return water, and dryer steam condensate from the plant area. After heat exchange in the heat exchange device 502 from the recycled water pool 501, it is treated by the microfiltration device 302 and then enters the second raw water tank 201.

[0026] The wastewater temperature in the aforementioned plant area can reach 70℃. The heat exchange and microfiltration processes described above enable the recovery and reuse of heat and wastewater. Specifically, the wastewater in the plant area can be heated to approximately 25℃ by the heat exchange device 502, which heats the water entering the second multi-media filter 201 from the second raw water tank 201 to meet the inlet water temperature requirements. The recycled water in the recycled water tank 501 and the production water in the raw water tank 201 are sent to the heat exchanger 502 for heat exchange, increasing the production water temperature, thereby reducing steam consumption and lowering costs. At the same time, the temperature of the recycled water is lowered to prevent damage to the equipment due to excessive temperature. Regarding wastewater recycling, the wastewater is treated and reused through the second demineralized water production line. Boiler wastewater, condensate, and equipment condensate enter the reuse water tank 501 to dilute each other and reduce the concentration of impurities. Then, it is pumped from the reuse water tank 501 to the wastewater collection tank 301. After being treated by the microfiltration device 302, the water quality meets the inlet water requirements of the ultrafiltration-reverse osmosis demineralized water production unit 2. It then enters the raw water tank 201 for further dilution and is finally treated and reused through the ultrafiltration device 203 and the concentrated water reverse osmosis device 205.

[0027] An ultrafiltration water tank 204 is installed between the ultrafiltration unit 203 and the reverse osmosis unit 205. A reverse osmosis permeate water tank 207 is located between the reverse osmosis unit 205 and the second mixed bed 206. The concentrate produced by the reverse osmosis unit 205 enters a reverse osmosis concentrate tank 209. Water treated by the ultrafiltration unit 203 enters the ultrafiltration water tank 204 and then flows into the downstream reverse osmosis unit 205. Similarly, water treated by the reverse osmosis unit 205 enters the reverse osmosis permeate water tank 207 and then flows into the downstream second mixed bed 206. The concentrate produced by the reverse osmosis unit 205 first enters the reverse osmosis concentrate tank 209 before proceeding downstream.

[0028] The influent to the microfiltration device 302 first enters the wastewater collection tank 301, and the effluent from the microfiltration device 302 is returned to the wastewater collection tank 301 for recycling before entering the raw water tank 201. This recycling process improves the microfiltration effect, ensuring that the water entering the raw water tank 201 meets the influent requirements of the second demineralized water production line. The concentrated wastewater discharged from the microfiltration device 302 is returned to the wastewater collection tank 301 via a pipeline, with the return flow rate being 5 / 6 of the total concentrated wastewater. This secondary filtration further enhances the concentrated wastewater recovery rate.

[0029] The concentrate / permeable water tank 402 has an overflow port at its top, positioned higher than the ultrafiltration water tank 204. Permeable water flows naturally into the ultrafiltration water tank 204, saving energy and reducing consumption. Furthermore, by increasing the overflow pipe diameter, it ensures timely and effective transfer of permeable water, thereby reducing the tank's design volume and eliminating the need for a new water pump, thus lowering the space requirements for new equipment. Two pipelines extend from the bottom of the concentrate / permeable water tank 402 to the microfiltration unit 302 and the high-pressure reverse osmosis unit 401 for cleaning both units, improving the permeable water production efficiency of the microfiltration unit 302.

[0030] By adopting the technical solution of this invention, based on the effluent quality of different processes in the two demineralized water production lines, a portion of the concentrated water can be directly utilized across systems, improving the equipment's water production efficiency. The effluent concentrated water discharged from the reverse osmosis unit 205 meets the backwashing requirements of the first multi-media filter 102. The concentrated water is pumped across systems from the concentrated water tank 209 into the first multi-media filter 102, replacing the raw water as backwash water. With the total influent volume remaining unchanged, this reduces the equipment's own raw water consumption, improving the equipment's water production efficiency. The backwashed water is then treated by the wastewater collection tank 301 and the microfiltration device 302 before replenishing the raw water tank 201, achieving water resource recycling; and realizing the coordinated recovery of concentrated water from the demineralized water production unit and a portion of the plant's effluent. The heat from the high-temperature plant wastewater itself is used to replace steam heating of the influent to the second demineralized water production line, saving energy and reducing consumption.

[0031] Effects of the invention:

[0032] 1. Achieve coordinated classification and recycling of wastewater from two demineralized water production units, increasing the system's water production rate from 55% to approximately 78%, reducing the amount of production water purchased, lowering production costs, and reducing wastewater discharge. Furthermore, fully utilize existing equipment and water tanks, reducing the design volume of water tanks and the need for additional water pumps, thereby reducing the required on-site space for equipment.

[0033] 2. Enable the direct utilization of some concentrated water across systems, thereby improving the system water production efficiency of the demineralized water production unit 1 and the microfiltration water treatment system 3.

[0034] 3. Achieve coordinated recovery of concentrated water from the demineralized water production unit and some wastewater discharged from the plant area.

Claims

1. A system for the co-treatment of effluents from two desalinated water production lines, characterized in that it comprises: The first desalted water production line comprises a first raw water tank (101), a first multi-medium filter (102), a positive bed (103), a negative bed (104), a first mixed bed (105), and a first desalted water tank (106) connected in series, and the second desalted water production line comprises a second raw water tank (201), a second multi-medium filter (202), an ultrafiltration device (203), a reverse osmosis device (205), a second mixed bed (206), and a second desalted water tank (208) connected in series. During the regeneration of the equipment in the first desalted water production line, the forward and reverse washing drainage of the first multi-medium filter (102), the reverse washing drainage of the positive bed (103), the reverse washing drainage of the negative bed (104), and the forward washing drainage of the first mixed bed (105) are treated by the microfiltration device (302) and then enter the second raw water tank (201); during the regeneration of the equipment in the second desalted water production line, the forward and reverse washing drainage of the second multi-medium filter (202), the reverse washing drainage of the ultrafiltration device (203), and the forward washing drainage of the second mixed bed (206) are treated by the microfiltration device (302) and then enter the second raw water tank (201).

2. The co-treatment system of two desalinated water production line effluents according to claim 1, characterized in that: The concentrated water produced by the reverse osmosis device (205) is used as the reverse washing water for the first and second multi-medium filters (102, 202).

3. The co-treatment system of two desalinated water production line effluents according to claim 1 or 2, characterized in that: The concentrated water produced by the reverse osmosis device (205) is treated by the high-pressure reverse osmosis device (401) and then used as the flushing water for the microfiltration device (302) or enters the reverse osmosis device (205) for recycling.

4. The co-treatment system of two desalinated water production line effluents according to claim 1, characterized in that: A heat exchanger (502) is arranged between the second raw water tank (201) and the downstream second multi-medium filter (202), and at least one of the boiler blowdown water, the power generation device cooling drainage, the pipe network steam condensate return water, and the dryer steam condensate water in the plant is used for heat exchange with the outlet water of the second raw water tank (201).

5. The co-treatment system of two desalinated water production line effluents according to claim 4, characterized in that: At least one of the boiler blowdown water, the power generation device cooling drainage, the pipe network steam condensate return water, and the dryer steam condensate water in the plant is used for heat exchange with the outlet water of the second raw water tank (201) in the heat exchange device (502), and then treated by the microfiltration device (302) and enters the second raw water tank (201).

6. The co-treatment system of two desalinated water production line effluents according to claim 1, characterized in that: An ultrafiltration water tank (204) is arranged between the ultrafiltration device (203) and the reverse osmosis device (205), a reverse osmosis produced water tank (207) is arranged between the reverse osmosis device (205) and the second mixed bed (206), and the concentrated water produced by the reverse osmosis device (205) enters a reverse osmosis concentrated water tank (209).

7. The co-treatment system of two desalinated water production line effluents according to claim 1, characterized in that: The inlet water of the microfiltration device (302) first enters a sewage collection tank (301), and the outlet water of the microfiltration device (302) returns to the sewage collection tank (301) for recycling and then enters the raw water tank (201).

8. The co-treatment system of two desalinated water production line effluents according to claim 4, characterized in that: A raw water heating device (210) is arranged between the second raw water tank (201) and the second multi-medium filter (202) in the second desalted water production line, and the heat exchanger (502) is arranged between the second raw water tank (201) and the raw water heating device (210).

Images