Rare earth wastewater desalination device

Abstract

The utility model discloses a kind of rare earth wastewater desalination equipment, it is related to wastewater desalination technical field, including concentration unit, multiple-effect evaporation unit is connected with concentration unit, salt crystal separation unit is connected with the effluent port of multiple-effect evaporation unit;Multiple-effect evaporation unit includes primary evaporator, the liquid inlet of primary evaporator is connected with concentration unit, the liquid inlet of secondary evaporator is connected with the effluent port of primary evaporator, the steam inlet of secondary evaporator is connected with the steam outlet of primary evaporator, the liquid inlet of tertiary evaporator is connected with the effluent port of secondary evaporator, the steam inlet of tertiary evaporator is connected with the steam outlet of secondary evaporator, the effluent port of tertiary evaporator is connected with salt crystal separation unit;This kind of rare earth wastewater desalination equipment multistage unit synergistic effect, realize the efficient desalination and resource recovery of rare earth wastewater, with the advantages of low energy consumption, desalination efficiency is high, salt crystal purity is high, water resource reuse rate is high.

Description

Technical Field

[0001] This utility model relates to the field of wastewater desalination technology, specifically a rare earth wastewater desalination device. Background Technology

[0002] Rare earth smelting and processing generate a large amount of high-salt wastewater. This type of wastewater contains various salts such as sodium chloride and sodium sulfate, and has a high salt concentration and complex composition. Direct discharge of such wastewater will cause serious environmental problems such as soil salinization and water pollution, while also wasting water and salt resources.

[0003] Currently, traditional desalination processes for rare earth wastewater mainly include single processes such as evaporation crystallization and reverse osmosis. However, while traditional single-effect evaporation has good desalination effect, it has high energy consumption and low steam utilization rate, which does not meet the requirements of energy conservation and environmental protection. Although reverse osmosis has relatively low energy consumption, it has strict requirements on the quality of the influent water, and the salt rejection rate of a single reverse osmosis membrane is limited, making it difficult to treat the complex salt components in rare earth wastewater. The desalinated wastewater cannot directly meet the requirements for reuse in production.

[0004] Therefore, this application is hereby submitted. Utility Model Content

[0005] The purpose of this invention is to provide a rare earth wastewater desalination device. This device features multi-stage unit synergy to achieve efficient desalination and resource recovery of rare earth wastewater, and has the advantages of low energy consumption, high desalination efficiency, high salt crystal purity, and high water resource reuse rate.

[0006] The above-mentioned optimized structure of this utility model is achieved through the following technical solution: a rare earth wastewater desalination device, including a concentration unit and a multi-effect evaporation unit, wherein the multi-effect evaporation unit is connected to the concentration unit; A salt crystal separation unit is connected to the liquid outlet of the multi-effect evaporation unit; The multi-effect evaporation unit includes a primary evaporator, and the liquid inlet of the primary evaporator is connected to the concentration unit. A secondary evaporator, wherein the liquid inlet of the secondary evaporator is connected to the liquid outlet of the primary evaporator, and the steam inlet of the secondary evaporator is connected to the steam outlet of the primary evaporator; The three-stage evaporator has its inlet connected to the outlet of the two-stage evaporator, its steam inlet connected to the steam outlet of the two-stage evaporator, and its outlet connected to the salt crystal separation unit.

[0007] Preferably, the multi-effect evaporation unit further includes a vacuum pump, which is connected to the first-stage evaporator, the second-stage evaporator, and the third-stage evaporator. A pressure control component, which is electrically connected to the vacuum pump, is used to control the pressure in the first-stage evaporator, the second-stage evaporator, and the third-stage evaporator.

[0008] Preferably, the pressure control assembly includes multiple regulating valves, which are respectively located between the vacuum pump and the first-stage evaporator, the second-stage evaporator, and the third-stage evaporator; Multiple throttling valves are provided, wherein the throttling valves are located between the steam inlet of the secondary evaporator and the steam outlet of the primary evaporator or between the steam inlet of the tertiary evaporator and the steam outlet of the secondary evaporator; Multiple pressure sensors are respectively installed in the first-stage evaporator, the second-stage evaporator, and the third-stage evaporator, and are electrically connected to the regulating valve and the throttling valve.

[0009] Preferably, the pressure in the primary evaporator, the secondary evaporator, and the tertiary evaporator decreases sequentially.

[0010] Preferably, the concentration unit includes an ultrafiltration component; A nanofiltration unit is disposed between the ultrafiltration unit and the liquid inlet of the first-stage evaporator.

[0011] Preferably, the salt crystal separation unit includes a centrifugal separator, which is connected to the liquid outlet of the three-stage evaporator; A dryer, which is connected to the centrifugal separator.

[0012] Preferably, it further includes a reuse unit, the reuse unit including an ion exchange column connected to the centrifuge; A filter, which is connected to the ion exchange column; A disinfection component, which is connected to the filter.

[0013] Preferably, it further includes a pretreatment unit, which includes a bar screen filter, an equalization tank, and a flocculation sedimentation tank connected in sequence.

[0014] In summary, this utility model has the following beneficial effects: (1) This utility model forms a complete rare earth wastewater treatment process through a pretreatment unit, a concentration unit, a multi-effect evaporation unit, a salt crystal separation unit and a reuse unit, realizing the integrated treatment of wastewater desalination, salt resource recovery and water resource reuse, and solving the problems of poor desalination effect and low resource utilization rate of traditional equipment.

[0015] (2) The multi-effect evaporation unit of this utility model adopts multiple evaporators connected in series and combined with a vacuum pump and pressure control components, which can realize the cascade utilization of steam, improve the utilization rate of thermal energy, and reduce energy consumption. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model.

[0017] In the diagram: 1. Concentration unit; 11. Ultrafiltration module; 12. Nanofiltration module; 2. Multi-effect evaporation unit; 21. Primary evaporator; 22. Secondary evaporator; 23. Tertiary evaporator; 24. Vacuum pump; 25. Control valve; 26. Throttling valve; 3. Salt crystal separation unit; 31. Centrifuge; 32. Dryer; 4. Reuse unit; 41. Ion exchange column; 42. Filter; 43. Sterilization unit; 5. Pretreatment unit; 51. Bar screen filter; 52. Equalization tank; 53. Flocculation sedimentation tank. Detailed Implementation

[0018] The technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0019] refer to Figure 1 A rare earth wastewater desalination device includes a concentration unit 1, a multi-effect evaporation unit 2, and a salt crystal separation unit 3. The units are connected by sealed pipes to ensure no wastewater leakage or steam loss during operation. This is existing technology and will not be described in detail here. The concentration unit 1 can concentrate the wastewater to increase its salt concentration. The multi-effect evaporation unit 2 is connected to the concentration unit 1 and can receive the concentrated wastewater output from the concentration unit 1 and evaporate and crystallize it to obtain a salt crystal mixture. The salt crystal separation unit 3 is connected to the outlet of the multi-effect evaporation unit 2 and can separate the salt crystals produced by the multi-effect evaporation unit 2 from the wastewater to obtain pure salt crystals.

[0020] The multi-effect evaporation unit 2 includes a first-stage evaporator 21, a second-stage evaporator 22, and a third-stage evaporator 23 connected in sequence, adopting a series-type stepped evaporation structure. The first-stage evaporator 21, the second-stage evaporator 22, and the third-stage evaporator 23 can all be falling film evaporators. The liquid inlet of the first-stage evaporator 21 is connected to the liquid outlet of the concentration unit 1, and can receive concentrated wastewater and generate secondary steam through external steam heating. The steam inlet of the first-stage evaporator 21 is sealed to the external steam equipment. The condensate outlet of the first-stage evaporator 21 can be discharged through a pipeline or recycled to the boiler feedwater system. The liquid inlet of the second-stage evaporator 22 is connected to the liquid outlet of the first-stage evaporator 21, and can receive the concentrated wastewater after partial evaporation in the first-stage evaporator 21. At the same time, the steam inlet of the second-stage evaporator 22 is sealed to the steam outlet of the first-stage evaporator 21, using the secondary steam generated by the first-stage evaporator 21 as a heating source to achieve stepped steam utilization. The condensate outlets of the second-stage evaporator 22 and the third-stage evaporator 23 are discharged through independent pipelines to avoid heat loss caused by mixing condensate at different temperatures. The inlet of the tertiary evaporator 23 is connected to the outlet of the secondary evaporator 22, and can receive the wastewater further concentrated by the secondary evaporator 22. The steam inlet of the tertiary evaporator 23 is connected to the steam outlet of the secondary evaporator 22, and uses the secondary steam generated by the secondary evaporator 22 as a heating source. The outlet of the tertiary evaporator 23 is sealed to the salt crystal separation unit 3, and outputs the salt crystal mixture.

[0021] Preferably, the multi-effect evaporation unit 2 further includes a vacuum pump 24 and a pressure control component; the vacuum pump 24 is connected to the first-stage evaporator 21, the second-stage evaporator 22, and the third-stage evaporator 23 through pipelines, and can extract non-condensable gases in the first-stage evaporator 21, the second-stage evaporator 22, and the third-stage evaporator 23; the pressure control component is electrically connected to the vacuum pump 24, and can adjust the pressure in the first-stage evaporator 21, the second-stage evaporator 22, and the third-stage evaporator in real time to ensure that the boiling point in each evaporator decreases sequentially, thus ensuring evaporation efficiency.

[0022] Preferably, the pressure control assembly includes multiple regulating valves 25, multiple throttling valves 26, and multiple pressure sensors (not shown in the figure): the multiple regulating valves 25 are respectively located on the pipelines between the vacuum pump 24 and the first-stage evaporator 21, the second-stage evaporator 22, and the third-stage evaporator 23, and can adjust the gas flow rate between the first-stage evaporator 21, the second-stage evaporator 22, the third-stage evaporator 23 and the vacuum pump 24, thereby independently adjusting the vacuum level of each evaporator; the multiple throttling valves 26 are respectively located on the steam connection pipelines between the second-stage evaporator 22 and the first-stage evaporator 21, and on the steam connection pipelines between the third-stage evaporator 23 and the second-stage evaporator 22, and can adjust the secondary steam delivery flow rate; the multiple pressure sensors are respectively embedded in the inner walls of the first-stage evaporator 21, the second-stage evaporator 22, and the third-stage evaporator 23, and the pressure sensors can be PT100. The pressure transmitter includes pressure sensors that are electrically connected to regulating valves 25 and throttle valves 26 via wires. The pressure control assembly also includes a PLC controller (programmable logic controller). The PLC controller can be connected to multiple regulating valves 25, multiple throttle valves 26, and multiple pressure sensors via wires. The pressure sensors can convert the real-time detected pressure signals into electrical signals and transmit them to the PLC controller. After comparing and analyzing preset pressure thresholds, the PLC controller sends adjustment commands to the regulating valves 25 and throttle valves 26: when the pressure in a certain evaporator is higher than the preset value, the opening of the corresponding regulating valve 25 is increased and the flow area of ​​the upstream throttle valve 26 is appropriately increased; when the pressure is lower than the preset value, the opening of the corresponding regulating valve 25 is decreased and the flow area of ​​the upstream throttle valve 26 is appropriately decreased to ensure that the pressure in each evaporator is stable within the preset range.

[0023] Preferably, the pressures within the primary evaporator 21, secondary evaporator 22, and tertiary evaporator 23 decrease sequentially. For example, the absolute pressure in the primary evaporator 21 is 0.08 MPa, corresponding to a boiling point of approximately 95°C; the absolute pressure in the secondary evaporator 22 is 0.05 MPa, corresponding to a boiling point of approximately 80°C; and the absolute pressure in the tertiary evaporator 23 is 0.02 MPa, corresponding to a boiling point of approximately 60°C. This pressure gradient design ensures that the boiling point of the wastewater in the primary evaporator 21, secondary evaporator 22, and tertiary evaporator 23 decreases sequentially, guaranteeing that the temperature of the secondary steam generated in the previous evaporator is higher than the boiling point of the subsequent evaporator. This provides a sufficient heat source for the subsequent evaporator, achieving cascaded utilization of steam energy, improving steam energy utilization efficiency, and reducing unit desalination energy consumption.

[0024] Preferably, the concentration unit 1 includes an ultrafiltration module 11 and a nanofiltration module 12, adopting a staged treatment structure of coarse filtration followed by fine filtration and then concentration. The nanofiltration module 12 is located between the ultrafiltration module 11 and the inlet of the first-stage evaporator 21. The ultrafiltration module 11 can be a hollow fiber ultrafiltration membrane with a molecular weight cutoff of 5000-10000 Da and an operating pressure of 0.1-0.3 MPa. It preferentially removes suspended solids, colloids, and large molecular organic matter from the wastewater, which are prone to causing fouling of the subsequent nanofiltration membrane or scaling of the evaporator, thus avoiding scaling of the subsequent membrane module and evaporator and ensuring stable operation of the nanofiltration module. The nanofiltration module 12 can be a spiral wound nanofiltration membrane with a molecular weight cutoff of 100-500 Da and an operating pressure of 0.4-0.8 MPa. It can retain some salts and small molecular organic matter in the wastewater, concentrating the wastewater to a preset salt concentration before it is transported to the first-stage evaporator 21, thereby reducing the evaporation load and energy consumption of the subsequent multi-effect evaporation unit 2.

[0025] Preferably, the salt crystal separation unit 3 includes a centrifugal separator 31 and a dryer 32; the inlet of the centrifugal separator 31 is sealed to the outlet of the three-stage evaporator 23, and the wet salt crystals in the salt crystal mixture can be separated from the wastewater by centrifugal force; the inlet of the dryer 32 is connected to the solid outlet of the centrifugal separator 31, and the wet salt crystals can be dried to a preset moisture content by hot air drying to obtain a pure salt crystal product.

[0026] Preferably, the system also includes a reuse unit 4, which is connected to the salt crystal separation unit 3. This unit can perform advanced treatment on the wastewater after salt crystal separation for reuse. The reuse unit 4 includes an ion exchange column 41, a filter 42, and a disinfection component 43. The inlet of the ion exchange column 41 is connected to the liquid outlet of the centrifuge 31. The column can be filled with 001×7 type cation exchange resin and 201×7 type anion exchange resin to remove trace amounts of residual Na in the wastewater. + Cl - SO4 2- The filter 42 is connected to the outlet of the ion exchange column 41 by isocyanate ions to reduce the conductivity of the wastewater. A 5μm precision filter membrane can be used to intercept resin debris and fine impurities that fall off in the ion exchange column, so as to avoid contaminating the subsequent disinfection equipment. The inlet of the disinfection component 43 is sealed to the outlet of the filter 42. An ultraviolet sterilizer or an ozone generator can be used to kill bacteria, viruses and other microorganisms in the wastewater, so as to ensure that the quality of the recycled water meets the "Design Code for Industrial Circulating Cooling Water Treatment" (GB / T50050-2017) or the standard for domestic miscellaneous water.

[0027] Preferably, the system further includes a pretreatment unit 5, which is connected to the concentration unit 1. This pretreatment unit 5 can pretreat the rare earth wastewater to remove suspended impurities and some pollutants. The pretreatment unit 5 includes a bar screen filter 51, an equalization tank 52, and a flocculation sedimentation tank 53 connected in sequence. The outlet of the bar screen filter 51 is connected to the inlet of the equalization tank 52. The bar screen filter 51 can be made of stainless steel mesh with a pore size of 5-10mm to remove large particulate suspended impurities such as rare earth slag and crushed residue from the wastewater, preventing blockage of subsequent pipelines and equipment. The outlet of the equalization tank 52 is connected to the inlet of the flocculation sedimentation tank 53, and it is equipped with a pH sensor and a low-speed stirrer to adjust the pH of the wastewater. The H value is adjusted to 6.5-8.5 to suit the flocculation reaction, while balancing the wastewater volume and quality to avoid a decrease in treatment efficiency in the subsequent flocculation sedimentation tank 53 due to water quality fluctuations. A stirring device can be installed in the flocculation sedimentation tank 53 to uniformly mix the flocculant with the wastewater. A sludge discharge port is provided at the bottom of the flocculation sedimentation tank 53, through which the settled flocs are periodically discharged. They can be dewatered and transported for disposal or rare earth recovery. A reagent dosing port can be provided at the top of the flocculation sedimentation tank 53, through which polyaluminum chloride and polyacrylamide are added sequentially. Under the action of the stirring device, the fine suspended impurities and colloidal substances in the wastewater form dense flocs and settle to the bottom of the tank. The supernatant is transported to the concentration unit 1.

[0028] The specific working principle is as follows: Rare earth wastewater first enters the bar screen filter 51 to remove large particulate suspended impurities such as rare earth slag and crushed residue, preventing blockage of subsequent pipelines and equipment. Then, the wastewater flows into the equalization tank 52 to adjust the pH value of the wastewater to a suitable range for flocculation reaction. The adjusted wastewater enters the flocculation sedimentation tank 53, where polyaluminum chloride and polyacrylamide are added sequentially through the top reagent dosing port. Under the action of the stirring device, the fine suspended impurities and colloidal substances in the wastewater form dense flocs and settle to the bottom of the tank. The flocs are periodically discharged through the bottom sludge discharge port, and the supernatant is transported to the concentration unit 1.

[0029] The pretreated supernatant enters the ultrafiltration module 11 to remove residual suspended solids, colloids, macromolecular organic matter and other impurities in the water. The wastewater after ultrafiltration enters the nanofiltration module 12, which retains most of the divalent salts, some of the monovalent salts and small molecule organic matter, and only allows water molecules and a small amount of small molecules to pass through, thereby concentrating the wastewater to obtain concentrated wastewater with a high salt concentration.

[0030] The concentrated high-salt wastewater first enters the primary evaporator 21. External steam equipment introduces heating steam (approximately 120°C) through the steam inlet of the primary evaporator 21, heating the wastewater to 95°C (corresponding to an absolute pressure of 0.08 MPa). Partial evaporation of the wastewater generates secondary steam (approximately 95°C). The concentrated wastewater, with further increased salt content, flows into the secondary evaporator 22 through the liquid outlet. The condensate in the primary evaporator 21 is discharged and recycled through the condensate outlet. The absolute pressure within the secondary evaporator 22 is adjusted to 0.05 MPa by the pressure control component. The boiling point should be 80℃. Its steam inlet receives secondary steam (95℃>80℃) generated by the first-stage evaporator 21. The heat of the secondary steam is used to heat and evaporate the internal wastewater, generating secondary steam again (temperature about 80℃). The wastewater continues to be concentrated and flows into the third-stage evaporator 23. The absolute pressure inside the third-stage evaporator 23 is adjusted to 0.02MPa (corresponding to a boiling point of 60℃). It receives secondary steam (80℃>60℃) from the second-stage evaporator 22 as a heating source, causing the wastewater to evaporate and crystallize to form a salt crystal mixture. Finally, it is transported to the salt crystal separation unit 3 through the liquid outlet.

[0031] During this process, the PT100 pressure sensor in each evaporator detects the pressure in real time and converts the signal into an electrical signal, which is then transmitted to the PLC controller. According to the preset pressure range, the PLC controller sends instructions to the regulating valve 25 and the throttle valve 26: when the pressure is too high, the opening of the corresponding regulating valve 25 is increased to enhance the vacuum pump 24's vacuuming effect, and the flow area of ​​the upstream throttle valve 26 is increased to increase the steam delivery volume; when the pressure is too low, the reverse adjustment is performed to ensure the pressure of each evaporator is stable and to ensure the efficiency of steam cascade utilization.

[0032] The salt crystal mixture enters the centrifugal separator 31, where the centrifugal force generated by high-speed rotation separates the wet salt crystals from the wastewater. The separated wastewater is transported to the recycling unit 4 through the liquid outlet, while the wet salt crystals enter the dryer 32 through the solid outlet to obtain pure salt crystal products, thus realizing the recovery of salt resources.

[0033] After salt crystal separation, the wastewater enters ion exchange column 41 to adsorb residual Na in the wastewater. + Cl - SO4 2- The wastewater is then filtered by a process called "salt ion removal" and then flows into filter 42 to trap resin debris and small impurities, preventing contamination of the disinfection equipment. Finally, the wastewater enters disinfection unit 43 to kill bacteria, viruses, and other microorganisms in the water, resulting in water that meets reuse standards and enabling water resource recycling.

[0034] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A rare earth wastewater desalination device, comprising a concentration unit (1), characterized in that: It also includes a multi-effect evaporation unit (2), which is connected to the concentration unit (1); Salt crystal separation unit (3), which is connected to the liquid outlet of the multi-effect evaporation unit (2); The multi-effect evaporation unit (2) includes a primary evaporator (21), the liquid inlet of which is connected to the concentration unit (1); A secondary evaporator (22) is provided, wherein the liquid inlet of the secondary evaporator (22) is connected to the liquid outlet of the primary evaporator (21), and the steam inlet of the secondary evaporator (22) is connected to the steam outlet of the primary evaporator (21). The three-stage evaporator (23) has its inlet connected to the outlet of the two-stage evaporator (22), its steam inlet connected to the steam outlet of the two-stage evaporator (22), and its outlet connected to the salt crystal separation unit (3).

2. The rare earth wastewater desalination equipment according to claim 1, characterized in that: The multi-effect evaporation unit (2) also includes a vacuum pump (24), which is connected to the first-stage evaporator (21), the second-stage evaporator (22), and the third-stage evaporator (23); The pressure control component is electrically connected to the vacuum pump (24) and can control the pressure in the first-stage evaporator (21), the second-stage evaporator (22), and the third-stage evaporator (23).

3. The rare earth wastewater desalination equipment according to claim 2, characterized in that: The pressure control assembly includes multiple regulating valves (25), which are respectively located between the vacuum pump (24) and the first-stage evaporator (21), the second-stage evaporator (22), and the third-stage evaporator (23); Multiple throttling valves (26) are provided between the steam inlet of the secondary evaporator (22) and the steam outlet of the primary evaporator (21) or between the steam inlet of the tertiary evaporator (23) and the steam outlet of the secondary evaporator (22). Multiple pressure sensors are respectively installed in the first-stage evaporator (21), the second-stage evaporator (22), and the third-stage evaporator (23), and are electrically connected to the regulating valve (25) and the throttling valve (26).

4. The rare earth wastewater desalination equipment according to claim 1, characterized in that: The pressure in the primary evaporator (21), the secondary evaporator (22), and the tertiary evaporator (23) decreases sequentially.

5. The rare earth wastewater desalination equipment according to claim 1, characterized in that: The concentration unit (1) includes an ultrafiltration component (11). Nanofiltration assembly (12) is located between the ultrafiltration assembly (11) and the liquid inlet of the first-stage evaporator (21).

6. The rare earth wastewater desalination equipment according to claim 1, characterized in that: The salt crystal separation unit (3) includes a centrifugal separator (31), which is connected to the liquid outlet of the three-stage evaporator (23). Dryer (32), which is connected to centrifugal separator (31).

7. A rare earth wastewater desalination device according to claim 6, characterized in that: It also includes a reuse unit (4), which includes an ion exchange column (41) connected to the centrifuge (31); A filter (42) is connected to the ion exchange column (41); Disinfection component (43) is connected to the filter (42).

8. The rare earth wastewater desalination equipment according to claim 1, characterized in that: It also includes a pretreatment unit (5), which includes a grid filter (51), an equalization tank (52) and a flocculation sedimentation tank (53) connected in sequence.

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