A leachate salt separation and crystallization device

Abstract

The utility model belongs to wastewater treatment technical field, concretely provides a kind of garbage leachate salt crystallization equipment, including nanofiltration device, concentration device, first crystallization device, oxidation device and second crystallization device;The water inlet of the concentration device is connected with the clean water outlet of the nanofiltration device;The water inlet of the first crystallization device is connected with the concentrated liquid outlet of the concentration device;The water inlet of the oxidation device is connected with the thick water outlet of the nanofiltration device;The water inlet of the second crystallization device is connected with the water outlet of the oxidation device.By nanofiltration device, salt is separated from source, realizes salt resource, avoids the generation of miscellaneous salt dangerous waste, and reduces evaporation crystallization difficulty, improves equipment utilization and operating stability, can significantly reduce the full life cycle cost of garbage leachate treatment.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment technology, specifically relating to a landfill leachate desalination and crystallization device. Background Technology

[0002] Landfill leachate has a complex composition, containing high concentrations of organic matter, ammonia nitrogen, and various salts (such as Cl). - SO4 2- Na + Ca 2+ (etc.). Currently, the industry commonly uses the "biological treatment + membrane deep treatment (NF / RO / DTRO)" process. Although it can produce qualified clean water, it generates a concentrate that accounts for 15%-30% of the influent volume. This concentrate has extremely high salt content (conductivity often >50mS / cm) and contains humic acid and other recalcitrant organic matter, making it extremely difficult to treat.

[0003] The current mainstream treatment methods are evaporation crystallization or advanced oxidation, but they have obvious drawbacks: (1) Scaling problem: Scaling salts such as CaSO4 in the concentrate are very easy to scale in the evaporator, which leads to a decrease in heat transfer efficiency and requires frequent shutdown for cleaning. (2) Mixed salt problem: Mixed salts formed by the co-crystallization of multiple salts are identified as hazardous waste (HW49), and the subsequent disposal costs are high, which brings a heavy economic burden to enterprises. (3) High operating cost: The energy consumption for treating the concentrate is high, and the disposal costs of mixed salts are added up, which makes the overall leachate treatment cost high. Utility Model Content

[0004] The purpose of this invention is to provide a device that can separate salt from its source, realize salt resource utilization, and reduce the difficulty of evaporation and crystallization, thereby meeting market demand.

[0005] Therefore, this utility model provides a landfill leachate desalination and crystallization device, including a nanofiltration device, a concentration device, a first crystallization device, an oxidation device, and a second crystallization device; the inlet of the concentration device is connected to the clean water outlet of the nanofiltration device; the inlet of the first crystallization device is connected to the concentrated liquid outlet of the concentration device; the inlet of the oxidation device is connected to the concentrated water outlet of the nanofiltration device; and the inlet of the second crystallization device is connected to the outlet of the oxidation device.

[0006] Specifically, the above-mentioned landfill leachate desalination and crystallization equipment also includes an ultrafiltration device; the outlet of the ultrafiltration device is connected to the inlet of the nanofiltration device.

[0007] Specifically, the above-mentioned landfill leachate desalination and crystallization equipment also includes a multi-media filter; the outlet of the multi-media filter is connected to the inlet of the ultrafiltration device.

[0008] Specifically, the first crystallization device includes a first evaporator, a first crystallizer, and a first centrifuge connected in sequence; the inlet of the first evaporator is connected to the outlet of the concentrate of the concentration device.

[0009] Specifically, the second crystallization device includes a second evaporator, a second crystallizer, and a second centrifuge connected in sequence; the inlet of the second evaporator is connected to the outlet of the oxidation device.

[0010] Specifically, the nanofiltration device is equipped with a first pH adjustment device at its inlet.

[0011] Specifically, a second pH adjustment device is installed at the inlet of the aforementioned oxidation device.

[0012] Specifically, a third pH adjustment device is provided at the inlet of the first crystallization device.

[0013] Specifically, a fourth pH adjustment device is provided at the inlet of the aforementioned second crystallization device.

[0014] Specifically, the aforementioned oxidation device includes one of an electro-Fenton device, an ozone catalytic oxidation device, or a persulfate advanced oxidation device.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] This utility model provides a landfill leachate salt separation and crystallization device that, through the key salt separation function of a nanofiltration unit, initially separates the salts in the leachate into a monovalent salt stream mainly composed of NaCl and a divalent salt stream mainly composed of CaSO4. This source separation lays the foundation for subsequent fractional crystallization and the preparation of by-products with potential industrial value, realizing salt resource utilization and avoiding the generation of hazardous waste containing mixed salts. The early separation and crystallization of easily scaling CaSO4 in a separate subsystem protects the NaCl evaporator, enabling stable and efficient operation, reducing system downtime for cleaning, and improving equipment utilization. The oxidation device specifically treats the nanofiltration concentrate rich in recalcitrant organic matter, effectively eliminating interference from organic matter on subsequent CaSO4 crystallization, ensuring the purity of the crystallized salt and the stable operation of the system. This equipment significantly reduces the total life-cycle cost of landfill leachate treatment by saving substantial costs on hazardous waste disposal, reducing maintenance costs, improving system operating efficiency, and generating potential salt product revenue.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the landfill leachate desalination and crystallization equipment provided by this utility model.

[0019] Explanation of reference numerals in the attached drawings: 1. Multi-media filter; 2. Ultrafiltration device; 3. Nanofiltration device; 4. Concentration device; 5. First crystallization device; 6. Oxidation device; 7. Second crystallization device. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0021] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0022] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0023] Reference Figure 1 This utility model provides a landfill leachate desalination and crystallization device, including a nanofiltration unit 3, a concentration unit 4, a first crystallization unit 5, an oxidation unit 6, and a second crystallization unit 7. The inlet of the concentration unit 4 is connected to the clean water outlet of the nanofiltration unit 3; the inlet of the first crystallization unit 5 is connected to the concentrated liquid outlet of the concentration unit 4; the inlet of the oxidation unit 6 is connected to the concentrated water outlet of the nanofiltration unit 3; and the inlet of the second crystallization unit 7 is connected to the outlet of the oxidation unit 6. The various devices are connected to each other via pipes and pumps, depending on the specific circumstances.

[0024] Nanofiltration unit 3 is used to receive raw leachate or pretreated leachate. The nanofiltration membrane unit preferably uses antifouling spiral wound membrane elements or ceramic membrane elements, and is designed to retain molecular weight of 100-200 Da. It separates the influent into nanofiltration permeate rich in monovalent salts and nanofiltration concentrate rich in divalent salts and macromolecular organic matter.

[0025] The concentration unit 4 is used to receive the nanofiltration permeate produced by the nanofiltration unit 3. It can select a disc tube reverse osmosis unit or a high-pressure reverse osmosis unit according to actual needs to further concentrate the nanofiltration permeate to obtain a concentrated solution mainly containing sodium chloride and qualified permeate that can be discharged or reused.

[0026] The first crystallization device 5 is used to receive the concentrated liquid produced by the concentration device 4, and to evaporate and crystallize the concentrated liquid to obtain sodium chloride crystals;

[0027] The oxidation device 6 is used to receive the nanofiltration concentrate produced by the nanofiltration device 3 and to degrade the recalcitrant organic matter in the nanofiltration concentrate. The oxidation device 6 preferably includes one of an electro-Fenton device, an ozone catalytic oxidation device 6, or a persulfate advanced oxidation device 6.

[0028] The second crystallization device 7 is used to receive the nanofiltration concentrate after treatment by the oxidation device 6 and to evaporate and crystallize it to obtain calcium sulfate crystals.

[0029] To reduce the adverse effects of colloids, suspended solids, macromolecular organic matter, microorganisms, etc. in landfill leachate on subsequent equipment, the landfill leachate desalination and crystallization equipment also includes an ultrafiltration device 2; the outlet of the ultrafiltration device 2 is connected to the inlet of the nanofiltration device 3.

[0030] Furthermore, the landfill leachate desalination and crystallization equipment also includes a multi-media filter 1; the outlet of the multi-media filter 1 is connected to the inlet of the ultrafiltration device 2.

[0031] In a detailed embodiment, the first crystallization apparatus 5 includes a first evaporator, a first crystallizer, and a first centrifuge connected in sequence; the inlet of the first evaporator is connected to the outlet of the concentrate of the concentration apparatus 4. After evaporation, crystallization, and centrifugation, the concentrate yields white sodium chloride solid, which can be further purified for use as industrial salt.

[0032] The second crystallization device 7 includes a second evaporator, a second crystallizer, and a second centrifuge connected in sequence; the inlet of the second evaporator is connected to the outlet of the oxidation device 6. After evaporation, crystallization, and centrifugation, the oxidized effluent yields high-purity calcium sulfate dihydrate (gypsum) solid, which can be used as an additive in building materials, etc.

[0033] The nanofiltration device 3, multi-media filter 1, ultrafiltration device 2, anti-fouling spiral wound membrane element, ceramic membrane element, disc tube reverse osmosis device, high pressure reverse osmosis device, electro-Fenton device, ozone catalytic oxidation device 6, persulfate advanced oxidation device 6, evaporator, crystallizer, and centrifuge mentioned above can be selected according to actual conditions to meet the corresponding functions, which will not be elaborated further.

[0034] In a preferred embodiment, the nanofiltration unit 3 is equipped with a first pH adjustment device at its inlet; the oxidation unit 6 is equipped with a second pH adjustment device at its inlet; the first crystallization unit 5 is equipped with a third pH adjustment device at its inlet; and the second crystallization unit 7 is equipped with a fourth pH adjustment device. The pH adjustment devices can be selected as needed. Each pH adjustment device is used to add a pH adjuster to its corresponding unit, and the adjuster is selected based on actual conditions. Throughout the process, the pH of the influent to each unit is controlled within the optimal range by the pH adjustment devices, thereby improving the treatment effect.

[0035] Example 1:

[0036] This embodiment provides a landfill leachate desalination and crystallization device, including a multi-media filter 1, an ultrafiltration device 2, a nanofiltration device 3, a concentration device 4, a first crystallization device 5, an oxidation device 6, and a second crystallization device 7. The devices are connected to each other through pipelines and pumps according to the actual situation, and the specific connections are as follows.

[0037] The outlet of the multi-media filter 1 is connected to the inlet of the ultrafiltration device 2; the outlet of the ultrafiltration device 2 is connected to the inlet of the nanofiltration device 3; the clean water outlet of the nanofiltration device 3 is connected to the inlet of the concentration device 4, and the concentrated water outlet of the nanofiltration device 3 is connected to the inlet of the oxidation device 6; the first crystallization device 5 includes a first evaporator, a first crystallizer, and a first centrifuge connected in sequence; the inlet of the first evaporator is connected to the concentrated liquid outlet of the concentration device 4; the second crystallization device 7 includes a second evaporator, a second crystallizer, and a second centrifuge connected in sequence; the inlet of the second evaporator is connected to the outlet of the oxidation device 6; a first pH adjustment device is provided at the inlet of the nanofiltration device 3; a second pH adjustment device is provided at the inlet of the oxidation device 6; a third pH adjustment device is provided at the inlet of the first crystallization device 5; and a fourth pH adjustment device is provided at the inlet of the second crystallization device 7.

[0038] In this embodiment, the nanofiltration device 3 uses a fouling-resistant spiral wound membrane element with a molecular weight cutoff of 150 Da, the concentration device 4 uses a disc tube reverse osmosis device, and the oxidation device 6 uses an electro-Fenton device.

[0039] In operation, landfill leachate first enters a multi-media filter 1 and an ultrafiltration unit 2 to remove colloids, suspended solids, macromolecular organic matter, and microorganisms for pretreatment. The pretreated permeate then enters a nanofiltration unit 3, where the pH of the nanofiltration feed water is adjusted to 8-9 by a first pH adjustment device. Then, under an operating pressure of 1.5-2.5 MPa, the membrane system separates the feed water into nanofiltration permeate, which mainly contains monovalent salts such as NaCl and KCl and a small amount of small-molecule organic matter, and nanofiltration concentrate, which mainly contains divalent salts such as CaSO4 and MgSO4 and most of the macromolecular organic matter such as humic acid.

[0040] Nanofiltration permeate enters the disc tube reverse osmosis unit, where it is concentrated to TDS > 15%, forming a concentrate (mainly NaCl). The permeate from the disc tube reverse osmosis unit meets discharge standards or is reused. The concentrate is sent to the first crystallization unit 5 (NaCl evaporation and crystallization line), where, after evaporation, crystallization, and centrifugation, white sodium chloride solid is obtained, which can be further purified for use as industrial salt.

[0041] Nanofiltration concentrate enters the electro-Fenton device, and the pH of the influent is adjusted to 3-4 by the second pH adjustment device. Under acidic conditions and the action of an electric field, recalcitrant organic matter is effectively degraded. The oxidized effluent enters the second crystallization device 7 (CaSO4 evaporation crystallization line), and after evaporation, crystallization, and centrifugation, high-purity calcium sulfate dihydrate (gypsum) solid is obtained, which can be used as an additive in building materials, etc.

[0042] The above examples are merely illustrative of this utility model and do not constitute a limitation on the scope of protection of this utility model. All designs that are the same as or similar to this utility model are within the scope of protection of this utility model.

Claims

1. A leachate fractionation crystallization apparatus, characterized by: It includes a nanofiltration device (3), a concentration device (4), a first crystallization device (5), an oxidation device (6), and a second crystallization device (7); the inlet of the concentration device (4) is connected to the clean water outlet of the nanofiltration device (3); the inlet of the first crystallization device (5) is connected to the concentrated liquid outlet of the concentration device (4); the inlet of the oxidation device (6) is connected to the concentrated water outlet of the nanofiltration device (3); and the inlet of the second crystallization device (7) is connected to the outlet of the oxidation device (6).

2. The landfill leachate desalination and crystallization equipment as described in claim 1, characterized in that: It also includes an ultrafiltration device (2); the outlet of the ultrafiltration device (2) is connected to the inlet of the nanofiltration device (3).

3. The apparatus for the fractional crystallization of landfill leachate according to claim 2, characterized in that: It also includes a multi-media filter (1); the outlet of the multi-media filter (1) is connected to the inlet of the ultrafiltration device (2).

4. The landfill leachate desalination and crystallization equipment as described in claim 1, characterized in that: The first crystallization device (5) includes a first evaporator, a first crystallizer and a first centrifuge connected in sequence; the water inlet of the first evaporator is connected to the concentrated liquid outlet of the concentration device (4).

5. The landfill leachate desalination and crystallization equipment as described in claim 1, characterized in that: The second crystallization device (7) includes a second evaporator, a second crystallizer, and a second centrifuge connected in sequence; the inlet of the second evaporator is connected to the outlet of the oxidation device (6).

6. The apparatus for the fractional crystallization of landfill leachate according to claim 1, wherein: The nanofiltration device (3) is equipped with a first pH adjustment device at its inlet.

7. The landfill leachate desalination and crystallization equipment as described in claim 1, characterized in that: The oxidation device (6) is equipped with a second pH adjustment device at the water inlet.

8. The apparatus for the fractional crystallization of landfill leachate according to claim 1, wherein: The first crystallization device (5) is equipped with a third pH adjustment device at the water inlet.

9. The apparatus for the fractional crystallization of landfill leachate according to claim 1, wherein: The second crystallization device (7) is equipped with a fourth pH adjustment device at the water inlet.

10. The apparatus for the fractional crystallization of landfill leachate according to claim 1, wherein: The oxidation device (6) includes one of an electro-Fenton device, an ozone catalytic oxidation device, or a persulfate advanced oxidation device.

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