Strong brine treatment device for seawater desalination

Abstract

The utility model relates to the technical field of seawater desalination strong brine treatment, and discloses a seawater desalination strong brine treatment device which comprises a membrane treatment system, a distillation system, a softening and hardness removing system and an evaporative crystallization system which are communicated in sequence, and the distillation system is communicated with the evaporative crystallization system. The utility model solves the problems of high operation cost and the like in the prior art.

Description

Technical Field

[0001] The utility model relates to the technical field of seawater desalination concentrated brine treatment, in particular to a seawater desalination concentrated brine treatment device. Background Art

[0002] Freshwater shortage has become a global problem, and seawater desalination technology is an important way to alleviate the freshwater crisis. Seawater desalination can be divided into thermal desalination and membrane desalination. After decades of development, its technology has gradually matured and its economic efficiency has become more reasonable. However, while obtaining fresh water, seawater desalination technology will produce a large amount of concentrated brine. Under normal circumstances, the production of 1 ton of fresh water will produce 1 to 2 tons of concentrated brine, and its salt content is 2 to 4 times that of seawater.

[0003] At present, there are three main ways to treat brine from seawater desalination: one is direct discharge. Since the salinity, concentration and temperature of brine are different from those of natural water bodies, and there may be various artificial cleaning agents and suspended pollutants that fall off metal pipes in it, if it is discharged directly into the sea, it will inevitably pose a potential threat to the marine ecological environment; the second is discharge after intervention, such as mixing and diluting with municipal wastewater before discharge or enhancing the diffusion of brine through design to reduce the impact of high salinity at the discharge port on the ocean, but the substantive problem has not been solved; the third is resource utilization, which adopts single or combined process salt production such as pretreatment, membrane separation or electrodialysis concentration, evaporation crystallization, etc. to extract chemical resources with economic value from brine, while reducing the discharge of brine or even achieving zero discharge.

[0004] The resource utilization of brine is the general trend, but the resource utilization of brine from seawater desalination generally has a long process flow, uses many equipments, and usually has high energy consumption, resulting in high operating costs and poor overall economic efficiency. Therefore, the development of a low-cost resource treatment technology for seawater desalination brine is of great significance to fundamentally solve the problem of brine discharge. Utility Model Content

[0005] In order to overcome the deficiencies of the prior art, the utility model provides a seawater desalination concentrated brine treatment device to solve the problems of high operating cost and the like in the prior art.

[0006] The technical solution adopted by the utility model to solve the above problems is:

[0007] A device for treating concentrated brine from seawater desalination comprises a membrane treatment system, a distillation system, a softening and hardness removal system and an evaporation and crystallization system which are connected in sequence, wherein the distillation system is connected to the evaporation and crystallization system.

[0008] As a preferred technical solution, the membrane treatment system includes a reverse osmosis membrane connected to the distillation system.

[0009] As a preferred technical solution, the membrane treatment system includes a nanofiltration membrane, and the nanofiltration membrane, a reverse osmosis membrane, and a distillation system are connected in sequence.

[0010] As a preferred technical solution, the distillation system includes a multi-effect evaporator, and the effect number of the multi-effect evaporator is [2, 10].

[0011] As a preferred technical solution, the distillation system includes a distillation concentrate pump, a multi-effect evaporator, a distillation concentrate pump, and a softening and de-hardening system which are connected in sequence.

[0012] As a preferred technical solution, the softening and hardness removal system includes a coagulation sedimentation tank, and the distillation system, the coagulation sedimentation tank, and the evaporation crystallization system are connected in sequence.

[0013] As a preferred technical solution, the evaporation crystallization system includes a softened water preheater, a heater, and a separator which are connected in sequence.

[0014] As a preferred technical solution, the evaporation crystallization system includes a circulation pump, a discharge pump, a separator, a circulation pump, and a heater connected in sequence, the separator, the circulation pump, and the discharge pump connected in sequence, and the separator is connected to the distillation system.

[0015] As a preferred technical solution, it also includes a multi-heat source utilization system, which is connected to the distillation system and the evaporation crystallization system respectively.

[0016] As a preferred technical solution, the flash tank, the flue gas heat exchanger connected to the flash tank, and the flash tank are connected to the distillation system and the evaporation crystallization system respectively.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] The utility model can realize the flexible and reasonable utilization of various heat sources including waste heat resources and the efficient coupling and recycling of heat sources between the distillation system and the evaporation crystallization system, thereby reducing the operating cost and energy consumption of the evaporation system, and obtaining high-quality crystallized salt, thereby realizing the resource utilization of seawater desalination and concentrated brine and having good economic benefits; in addition, compared with the traditional treatment measure of discharging all concentrated brine into the sea, this technology has better environmental and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the utility model.

[0020] Marks and their corresponding names in the accompanying drawings: 1-membrane treatment system, 12-nanofiltration membrane, 14-reverse osmosis membrane, 2-distillation system, 21-multi-effect evaporator, 22-distillation concentrate pump, 3-softening and hardness removal system, 31-coagulation sedimentation tank, 4-evaporation crystallization system, 41-heater, 42-separator, 43-circulation pump, 44-discharge pump, 45-softened water preheater, 5-multi-heat source utilization system, 55-flue gas heat exchanger, 58-flash tank. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the embodiments and drawings, but the implementation manner of the present invention is not limited thereto.

[0022] Example 1

[0023] like Figure 1 As shown, the utility model provides a low-cost resource processing technology for producing industrial salt from seawater desalination concentrated brine, which adopts the process of "nanofiltration salt separation + reverse osmosis concentration + low-temperature multi-effect distillation + softening and hardness removal + evaporation crystallization", and can realize the flexible and reasonable utilization of various heat sources (including waste heat resources) and the efficient coupling and recovery of heat sources between the distillation system and the evaporation crystallization system, fully reduce the operating cost of the evaporation system, and realize the resource utilization of seawater desalination concentrated brine in a more economical form.

[0024] The utility model structure is as follows Figure 1 shown.

[0025] The overall process flow is that the desalinated brine is treated by nanofiltration and reverse osmosis membrane to remove divalent ions and concentrate (the amount of reverse osmosis brine is about 20% to 30% of the raw water). The concentrated and impurity-free brine is further concentrated and reduced by a low-temperature multi-effect distillation system (the amount of distilled brine is about 30% to 40% of the reverse osmosis brine). The distilled brine is softened and hardened by adding chemicals and then enters the evaporation crystallization system to obtain high-quality sodium chloride crystals (in line with industrial grade 1 standards). At the same time, multiple heat sources including waste heat resources are flexibly utilized, and the heat sources of the distillation and evaporation crystallization systems are efficiently coupled, ultimately realizing low-cost resource utilization of desalinated brine.

[0026] The specific process is as follows:

[0027] The concentrated brine from seawater desalination enters the membrane treatment system 1, and the divalent ions in the concentrated brine are first removed by the nanofiltration membrane 12. The nanofiltration concentrated water is discharged, and the produced water containing sodium chloride enters the reverse osmosis membrane 14 for concentration. The reverse osmosis produced water is reused, and the reverse osmosis concentrated water enters the distillation system 2 (in this embodiment, a low-temperature multi-effect distillation system is preferably used) for further concentration and reduction to reduce the processing volume of subsequent evaporation and crystallization.

[0028] The heat source temperature required by the distillation system 2 is low (generally below 70°C), and the secondary steam (controlled below 70°C) generated by the separator 42 in the subsequent evaporation and crystallization system 4 can be directly used, or when the heat source is insufficient, the steam generated by the flash evaporation of the condensed water generated by part of the heater 41 can be considered as the heat source, so as to realize the efficient coupling utilization of the heat source between the distillation system 2 and the evaporation and crystallization system 4. At the same time, the condensation treatment of the secondary steam can also be saved, simplifying the overall process system. At the same time, according to actual needs, the multi-heat source utilization system 5 can be used to recover waste heat resources such as hot water and high-temperature / low-temperature flue gas heat, and part of the raw steam can be supplemented when the heat source is insufficient. The reverse osmosis concentrated water enters the first-effect evaporator in the distillation system 2, and after sufficient heat exchange with the heat source steam, part of the concentrated water evaporates into secondary steam. This secondary steam is used as the heating steam for the next effect, and so on to the final effect, and the steam condensed water is the product water for reuse. The distilled concentrated water (through the distilled concentrated water pump 22) enters the softening and hardness removal system 3 and the evaporation and crystallization system 4 in turn to prepare crystalline salt. In addition, in order to maintain the vacuum degree of the distillation system 2, a vacuum system is provided to extract the non-condensable gas inside the equipment. The number of effects of the distillation system 2 is determined according to the specific water volume and water quality, and 2 to 10 effects are generally used here.

[0029] In order to ensure the quality of the crystallized salt, the distilled concentrated water enters the coagulation sedimentation tank 31 of the softening and hardness removal system 3, and sodium hydroxide, sodium carbonate, coagulant (such as polyaluminum chloride, etc.) and flocculant (such as polyacrylamide, etc.) are added in sequence to remove calcium and magnesium ions and obtain softened water.

[0030] The softened water enters the softened water preheater 45 and is preheated by the high-temperature condensed water generated by the evaporation crystallization system 4 before entering the evaporation crystallization system. After heat exchange with the heating steam in the heater 41, the temperature rises and enters the separator 42 for flash evaporation. After flash evaporation, the concentration of the concentrated brine is further increased, and crystallized salt is precipitated. After the solid content reaches the set value, it is discharged from the system, and NaCl crystallized salt is obtained after dehydration and drying in sequence. Part of the mother liquor is refluxed to the evaporation crystallization system 4. According to actual conditions, the heat source of the evaporation crystallization system 4 can utilize a multi-heat source utilization system 5, such as hot water, high-temperature / low-temperature flue gas or raw steam. When there is no waste heat resource or it is insufficient, a steam compressor can be set up or a multi-effect evaporation can be adopted to fully recover the latent heat in the secondary steam and reduce the heat source consumption. At the same time, the number of effects and sets of the evaporation crystallization system 4 are determined according to the specific water volume and water quality conditions, and generally 1 to 4 effects are used.

[0031] The utility model adopts a membrane system combined with distillation, softening and hardness removal, evaporation crystallization and multi-heat source utilization technology, which can simultaneously obtain high-quality NaCl crystal salt and product water, has good economic benefits, minimizes the discharge of concentrated brine, and realizes the resource utilization of seawater desalination concentrated brine.

[0032] The utility model can flexibly utilize multiple heat sources such as flue gas, hot water, steam, etc., reduce or eliminate the use of raw steam, reduce the operating cost and energy consumption of the evaporation system, and the rational and flexible utilization of multiple heat sources realizes the low-cost resource utilization of seawater desalination and concentrated brine.

[0033] The utility model rationally plans energy parameters and utilization methods, and innovatively makes full use of the secondary steam in the evaporation crystallization system as the heat source of the distillation system. At the same time, it can also be adjusted according to actual conditions, and the steam obtained by flash evaporation of part of the condensed water generated by the evaporation crystallization system can be used as the heat source of the distillation system, ultimately realizing the efficient coupling utilization of the heat sources between the distillation system and the evaporation crystallization system, and reducing the system energy consumption and operating costs.

[0034] The utility model aims at the problems of high cost, high energy consumption and poor economic benefits of seawater desalination concentrated brine resource treatment technology, and proposes a low-cost seawater desalination concentrated brine resource treatment technology, which can realize the flexible and reasonable utilization of multiple heat sources including waste heat resources and the efficient coupling and recycling of heat sources between the distillation system and the evaporation crystallization system, reduce the operating cost and energy consumption of the evaporation system, and obtain high-quality crystallized salt, realizing the resource utilization of seawater desalination concentrated brine while having good economic benefits. In addition, compared with the traditional treatment measures of discharging all concentrated brine into the sea, this technology has better environmental and social benefits.

[0035] Taking the 2000t / h seawater desalination brine resource utilization system as an example, the system can make full use of the high-temperature flue gas waste heat resources in the plant area, and efficiently couple the heat sources of the distillation system and the evaporation crystallization system, greatly reducing the steam consumption and reducing the operating costs by more than 20%. At the same time, the product water and crystallized salt produced can generate an annual income of 40 to 60 million yuan, which has good economic benefits.

[0036] The utility model designs a process route for the resource processing technology of seawater desalination and concentrated brine, and adopts a membrane system combined with low-temperature multi-effect distillation, evaporation crystallization and multi-heat source utilization.

[0037] The utility model designs a multi-heat source utilization system, which has the function of simultaneously utilizing multiple waste heat sources such as high-temperature flue gas, low-temperature flue gas, hot water and steam heat source. The heat sources are designed in parallel and can be used individually or simultaneously.

[0038] The utility model designs a heat source coupling process, which efficiently couples and utilizes the heat source between the distillation system and the evaporation crystallization system, and utilizes the secondary steam (below 70° C.) generated in the evaporation crystallization system as the heat source (below 70° C.) of the distillation system.

[0039] The above-mentioned heat source coupling process has a process design for supplementing the heat source of the distillation system, which can be adjusted according to actual conditions, and the steam obtained by flash evaporation of part of the condensed water produced by the evaporation crystallization system can be used as a supplementary heat source for the distillation system.

[0040] Example 2

[0041] like Figure 1 As shown, as a further optimization of Example 1, based on Example 1, this embodiment also includes the following technical features:

[0042] like Figure 1 As shown:

[0043] In this embodiment, an industrial plant equipped with seawater desalination and having flue gas waste heat is taken as an example to introduce a specific embodiment of the utility model. The seawater desalination concentrated water volume is 2000t / h, and the heat of the factory flue gas waste heat is used to process the seawater desalination concentrated brine as a resource.

[0044] (1) Membrane treatment system 1

[0045] The seawater desalination brine (2000t / h, TDS about 65000-70000mg / L) first uses the nanofiltration membrane 12 to remove the divalent ions in the brine, and the nanofiltration brine is discharged. The nanofiltration product water containing sodium chloride enters the reverse osmosis membrane 14 for concentration. The final reverse osmosis brine has a water volume of 500-510t / h and a TDS of about 84000-85000mg / L.

[0046] (2) Distillation system 2

[0047] All the reverse osmosis concentrated water is used as the material water of the distillation system 2 (in this embodiment, a low-temperature multi-effect distillation system is preferably used). According to the water volume and water quality of the reverse osmosis concentrated water, the distillation system 2 adopts a set of 6-effect evaporators + condensers. The heat source of the distillation system 2 adopts the secondary steam (65-70°C) flashed from the hot water delivered by the multi-heat source system 5 and the secondary steam (65-70°C, 29-31t / h) delivered by the evaporation crystallization system 4. After mixing, they enter the first-effect evaporator to exchange heat with the material water. Part of the material water evaporates into secondary steam, which is used as the heat source steam of the second effect, and so on to the sixth effect.

[0048] Part of the condensed water from the first-effect heat source steam returns to the flash tank, and the rest is mixed into the distillation product water system. At the same time, the condensed water produced by each effect starting from the second effect flows to the next effect step by step, and is mixed with the condensed fresh water produced by the condenser in the sixth-effect evaporator and discharged by the product water pump.

[0049] After the first-effect material seawater is evaporated, the remaining distilled concentrated water flows into the 2-6 effect flash tanks by gravity step by step, and is output by the distilled concentrated water pump in the sixth effect flash tank to the downstream softening and de-hardening system 3. The distilled concentrated water volume is 190-195 / h, and the TDS is about 230000-250000 mg / L.

[0050] In order to maintain the vacuum of distillation system 2, a vacuum system is set up to extract the non-condensable gas inside the equipment. At the same time, the system is equipped with a defoamer and antiscalant dosing system to reduce foaming and scaling.

[0051] (3) Softening and de-hardening system 3

[0052] In order to ensure the quality of the crystallized salt, the distilled concentrated water enters the coagulation sedimentation tank 31 of the softening and hardness removal system 3 for further hardness removal. Sodium hydroxide, sodium carbonate, coagulant (such as polyaluminum chloride, etc.) and flocculant (such as polyacrylamide, etc.) are added in sequence to reduce the calcium and magnesium ions to below 200 mg / L to obtain softened water.

[0053] (4) Evaporation crystallization system 4

[0054] The evaporation crystallization system 4 is provided with 5 sets of evaporators, with a total processing capacity of 200t / h, and a single set processing capacity of 40t / h, of which 4 sets are equipped with MVR steam compressors, namely 1 set of single-effect forced circulation evaporator (1# evaporation crystallizer) + 4 sets of single-effect MVR forced circulation evaporators (2#-5# evaporation crystallizers). Preferably, the evaporation crystallization system 4 also includes a circulation pump 43 and a discharge pump 44.

[0055] After being preheated by the condensate water of 2#-5# evaporation crystallizers, the softened water is used as the inlet water of evaporation crystallization system 4, and enters 5 sets of evaporation crystallizers in parallel to fully exchange heat with the heating steam and flash evaporate.

[0056] In order to make full use of the flue gas waste heat in the plant area and provide a heat source with a suitable temperature for the distillation system 2, the multi-heat source utilization system 5 first uses desalted water to exchange heat with the low-temperature flue gas (120-130°C) in the plant area in the flue gas heat exchanger 55. The hot water after heat exchange (100-105°C, 870-880t / h) enters the flash tank 58 for flash evaporation. The steam volume (85-90°C, 29-31t / h) obtained can meet the needs of the 1# evaporation crystallizer. The remaining hot water and the condensed water generated by the 1# evaporation crystallizer heater are mixed into hot water to the distillation system 2 for flash evaporation. At the same time, it is mixed with the secondary steam (65-70°C, 29-31t / h) generated by the 1# evaporation crystallizer separator as the heating steam for the distillation system 2. The 2#-5# evaporation crystallizers use MVR steam compressors to fully recover the heat in the secondary steam. The condensed water is preheated to distill the concentrated water and then cooled to merge with the distillation product water. The product water volume is 170-175t / h.

[0057] The solid-containing brine produced by the evaporation crystallization system is dehydrated and dried in turn to obtain NaCl crystallized salt (industrial first-class quality). The mother liquor is refluxed to the evaporation crystallization system 4. At the same time, in order to ensure the quality of the crystallized salt, a small amount of mother liquor is discharged. The final output of crystallized salt is 40-42 t / h.

[0058] The 1# evaporator crystallizer device operates in a negative pressure environment, and the system is equipped with a vacuum system to establish and maintain system vacuum.

[0059] The seawater desalination and concentrated brine resource processing system reduces the operating cost by more than 20% by making full use of the waste heat of the flue gas in the plant and fully recovering the energy of the evaporation crystallization system 4 as the heat source of the distillation system 2. At the same time, the product water and crystallized salt can generate an annual income of 40 to 60 million yuan, with good economic benefits. Through the flexible use of multiple heat sources, low-cost seawater desalination and concentrated brine resource processing is achieved.

[0060] As described above, the utility model can be implemented well.

[0061] The above is only a preferred embodiment of the utility model and does not limit the utility model in any form. According to the technical essence of the utility model, within the spirit and principles of the utility model, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the utility model.

Claims

1. A seawater desalination and concentrated brine treatment device, characterized in that: It comprises a membrane treatment system (1), a distillation system (2), a softening and hardness removal system (3), and an evaporation and crystallization system (4) which are connected in sequence, and the distillation system (2) is connected to the evaporation and crystallization system (4).

2. A seawater desalination and concentrated brine treatment device according to claim 1, characterized in that: The membrane treatment system (1) includes a reverse osmosis membrane (14) in communication with a distillation system (2).

3. A seawater desalination and concentrated brine treatment device according to claim 2, characterized in that: The membrane treatment system (1) comprises a nanofiltration membrane (12), and the nanofiltration membrane (12), a reverse osmosis membrane (14), and a distillation system (2) are connected in sequence.

4. The device for treating concentrated brine from seawater desalination according to claim 1, characterized in that: The distillation system (2) comprises a multiple-effect evaporator (21), and the effect number of the multiple-effect evaporator (21) is [2, 10].

5. A seawater desalination and concentrated brine treatment device according to claim 4, characterized in that: The distillation system (2) comprises a distillation concentrate pump (22), a multi-effect evaporator (21), a distillation concentrate pump (22), and a softening and de-hardening system (3) which are connected in sequence.

6. The device for treating concentrated brine from seawater desalination according to claim 1, characterized in that: The softening and hardness removal system (3) comprises a coagulation sedimentation tank (31), and the distillation system (2), the coagulation sedimentation tank (31), and the evaporation crystallization system (4) are connected in sequence.

7. The device for treating concentrated brine from seawater desalination according to claim 1, characterized in that: The evaporation crystallization system (4) comprises a softened water preheater (45), a heater (41), and a separator (42) which are connected in sequence.

8. The device for treating concentrated brine from seawater desalination according to claim 7, characterized in that: The evaporation crystallization system (4) comprises a circulation pump (43) and a discharge pump (44); a separator (42), a circulation pump (43) and a heater (41) are connected in sequence; a separator (42), a circulation pump (43) and a discharge pump (44) are connected in sequence; and a separator (42) is connected to a distillation system (2).

9. A seawater desalination and concentrated brine treatment device according to any one of claims 1 to 8, characterized in that: It also includes a multi-heat source utilization system (5), which is connected to the distillation system (2) and the evaporation crystallization system (4) respectively.

10. The device for treating concentrated brine from seawater desalination according to claim 9, characterized in that: A flash tank (58), a flue gas heat exchanger (55) connected to the flash tank (58), and the flash tank (58) are connected to the distillation system (2) and the evaporation crystallization system (4) respectively.

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