A low-energy wastewater treatment system for iron phosphate production

Abstract

This invention provides a low-energy-consumption wastewater treatment system for ferric phosphate production, comprising a mother liquor wastewater equalization tank, a wash water wastewater equalization tank, a first pretreatment unit, a second pretreatment unit, a nanofiltration unit, a reverse osmosis unit, and an evaporation unit. The outlet of the mother liquor wastewater equalization tank is connected to the inlet of the first pretreatment unit, the outlet of the first pretreatment unit is connected to the inlet of the nanofiltration unit, and the concentrate outlet of the nanofiltration unit is connected to the inlet of the evaporation unit. Similarly, the outlet of the wash water wastewater equalization tank is connected to the inlet of the second pretreatment unit, the outlet of the second pretreatment unit is connected to the inlet of the reverse osmosis unit, and the product water outlet of the nanofiltration unit is connected to the inlet of the reverse osmosis unit. This invention employs nanofiltration and two-stage reverse osmosis to achieve wastewater reuse while concentrating the wastewater, reducing the investment and operating costs of the evaporator. Furthermore, by evaporating the wastewater, it achieves zero wastewater discharge.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment technology, and in particular relates to a low-energy-consumption wastewater treatment system for iron phosphate production. Background Technology

[0002] Green lithium-ion power batteries, integrating energy saving, environmental protection, and recyclability, are currently the most compliant clean energy source in China. They are mainly used in electric vehicles, communications, homes, energy storage devices, instruments, and model aircraft. Lithium batteries account for a significant portion of the cost of new energy vehicles, approximately 40%. Iron phosphate is also an ideal precursor raw material for the positive electrode materials of in-vehicle lithium-ion power batteries, grid energy storage batteries, and power tool batteries.

[0003] The traditional method for synthesizing ferric phosphate involves reacting divalent ferric salts (such as ferrous sulfate) with ammonium hydrogen phosphate, phosphoric acid, ammonia, hydrogen peroxide, etc. This process generates two streams of acidic ammonium sulfate wastewater: wash water and mother liquor. Both streams contain high levels of ammonia nitrogen, heavy metals, and phosphorus, making wastewater treatment extremely difficult and causing significant harm to the surrounding natural environment. Utility Model Content

[0004] The purpose of this invention is to provide a low-energy-consumption wastewater treatment system for ferric phosphate production.

[0005] Therefore, the above-mentioned objective of this utility model is achieved through the following technical solution:

[0006] A low-energy-consumption ferric phosphate production wastewater treatment system includes a mother liquor wastewater equalization tank, a washing wastewater equalization tank, a first pretreatment unit, a second pretreatment unit, a nanofiltration unit, a reverse osmosis unit, and an evaporation unit;

[0007] The outlet of the mother liquor wastewater equalization tank is connected to the inlet of the first pretreatment unit, the outlet of the first pretreatment unit is connected to the inlet of the nanofiltration unit, and the concentrate outlet of the nanofiltration unit is connected to the inlet of the evaporation unit.

[0008] The outlet of the wastewater equalization tank is connected to the inlet of the second pretreatment unit, the outlet of the second pretreatment unit is connected to the inlet of the reverse osmosis unit, and the product water outlet of the nanofiltration unit is connected to the inlet of the reverse osmosis unit.

[0009] While adopting the above technical solutions, this utility model may also adopt or combine the following technical solutions:

[0010] As a preferred technical solution of this utility model: the concentrate outlet of the reverse osmosis unit is connected to the inlet of the nanofiltration unit.

[0011] As a preferred technical solution of this utility model: the reverse osmosis unit includes a first-stage reverse osmosis device and a second-stage reverse osmosis device;

[0012] The inlet of the first-stage reverse osmosis unit is connected to the outlet of the second pretreatment unit and the permeate outlet of the nanofiltration unit, respectively. The permeate outlet of the first-stage reverse osmosis unit is connected to the inlet of the second-stage reverse osmosis unit, and the concentrate outlet of the first-stage reverse osmosis unit is connected to the inlet of the nanofiltration unit.

[0013] As a preferred technical solution of this utility model: the concentrate outlet of the secondary reverse osmosis device is connected to the inlet of the primary reverse osmosis device.

[0014] As a preferred technical solution of this utility model: the first-stage reverse osmosis device uses a brackish water membrane, and the second-stage reverse osmosis device uses a seawater desalination membrane.

[0015] As a preferred technical solution of this utility model: the first pretreatment unit consists of a heat exchanger, a dosing device, a flocculation sedimentation tank and a microfiltration membrane device.

[0016] As a preferred technical solution of this utility model: the second pretreatment unit consists of a heat exchanger, a dosing device, a flocculation sedimentation tank and a microfiltration membrane device.

[0017] As a preferred technical solution of this utility model: the nanofiltration unit is a high-pressure nanofiltration membrane device.

[0018] As a preferred technical solution of this utility model: the evaporation unit is a forced circulation horizontal tube evaporator or an MVR (mechanical vapor recompression) evaporator.

[0019] This utility model provides a low-energy-consumption wastewater treatment system for ferric phosphate production, which has the following beneficial effects:

[0020] (1) The system equipment is simple and highly operable;

[0021] (2) Wastewater is concentrated by nanofiltration unit. Compared with concentration by only using reverse osmosis unit, it has the purpose of low energy consumption, low cost and high pollution resistance. Furthermore, the nanofiltration unit is a high pressure nanofiltration membrane device. The filtration effect of nanofiltration membrane is worse than that of reverse osmosis, and the salinity of the produced water is higher than that of reverse osmosis produced water. Therefore, under the same concentration, the operating pressure of nanofiltration membrane will be lower than that of reverse osmosis, so as to achieve the purpose of energy saving and low carbon.

[0022] (3) By adopting nanofiltration and two-stage reverse osmosis, wastewater can be reused and concentrated at the same time, reducing the investment and operating costs of the evaporator. Furthermore, the wastewater can be evaporated in the form of evaporation to achieve zero wastewater discharge. Attached Figure Description

[0023] Figure 1 This is a connection diagram of the low-energy ferric phosphate production wastewater treatment system provided by this utility model. Detailed Implementation

[0024] The present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

[0025] A low-energy ferric phosphate production wastewater treatment system includes a mother liquor wastewater equalization tank 101, a washing wastewater equalization tank 102, a first pretreatment unit 201, a second pretreatment unit 202, a nanofiltration unit 301, a reverse osmosis unit, and an evaporation unit 501.

[0026] The outlet of the mother liquor wastewater equalization tank 101 is connected to the inlet of the first pretreatment unit 201, the outlet of the first pretreatment unit 201 is connected to the inlet of the nanofiltration unit 301, and the concentrate outlet of the nanofiltration unit 301 is connected to the inlet of the evaporation unit 501.

[0027] The outlet of the washing wastewater equalization tank 102 is connected to the inlet of the second pretreatment unit 202, the outlet of the second pretreatment unit 202 is connected to the inlet of the reverse osmosis unit, and the product water outlet of the nanofiltration unit 301 is connected to the inlet of the reverse osmosis unit.

[0028] In this embodiment, the concentrate outlet of the reverse osmosis unit is connected to the inlet of the nanofiltration unit 301.

[0029] In this embodiment: the reverse osmosis unit includes a first-stage reverse osmosis device 401 and a second-stage reverse osmosis device 402;

[0030] The inlet of the first-stage reverse osmosis unit 401 is connected to the outlet of the second pretreatment unit 202 and the product water outlet of the nanofiltration unit 301, respectively. The product water outlet of the first-stage reverse osmosis unit 401 is connected to the inlet of the second-stage reverse osmosis unit 402, and the concentrate outlet of the first-stage reverse osmosis unit 401 is connected to the inlet of the nanofiltration unit 301.

[0031] The concentrate outlet of the secondary reverse osmosis unit 402 is connected to the inlet of the primary reverse osmosis unit 401.

[0032] The first-stage reverse osmosis unit removes 70%–80% of ammonium ions and over 95% of phosphate ions.

[0033] In this embodiment: the first-stage reverse osmosis unit 401 uses a brackish water membrane, and the second-stage reverse osmosis unit 402 uses a seawater desalination membrane.

[0034] In this embodiment: the first pretreatment unit 201 consists of a heat exchanger, a dosing device, a flocculation sedimentation tank, and a microfiltration membrane device; the second pretreatment unit 202 consists of a heat exchanger, a dosing device, a flocculation sedimentation tank, and a microfiltration membrane device.

[0035] The purpose of pretreatment is to cool the wastewater through a heat exchanger, adjust the pH of the wastewater through a dosing device, and remove some of the bound ammonia nitrogen and precipitate more than 90% of the dissolved phosphorus in the wastewater through a dosing device, a flocculation sedimentation tank, and a microfiltration membrane device.

[0036] In this embodiment: Nanofiltration unit 301 is a high-pressure nanofiltration membrane device, which retains 50% to 60% of ammonium ions.

[0037] In this embodiment: Evaporation unit 501 is an MVR (Mechanical Vapor Recompression) evaporator, which recovers ammonium phosphate compound fertilizer.

[0038] The above specific implementation examples are used to explain and illustrate this utility model, and are only preferred embodiments of this utility model, not intended to limit this utility model. Any modifications, equivalent substitutions, improvements, etc., made to this utility model within the spirit and scope of the claims shall fall within the protection scope of this utility model.

Claims

1. A low-energy-consumption wastewater treatment system for ferric phosphate production, characterized in that: It includes a mother liquor wastewater equalization tank, a washing wastewater equalization tank, a first pretreatment unit, a second pretreatment unit, a nanofiltration unit, a reverse osmosis unit, and an evaporation unit; The outlet of the mother liquor wastewater equalization tank is connected to the inlet of the first pretreatment unit, the outlet of the first pretreatment unit is connected to the inlet of the nanofiltration unit, and the concentrate outlet of the nanofiltration unit is connected to the inlet of the evaporation unit. The outlet of the wastewater equalization tank is connected to the inlet of the second pretreatment unit, the outlet of the second pretreatment unit is connected to the inlet of the reverse osmosis unit, and the product water outlet of the nanofiltration unit is connected to the inlet of the reverse osmosis unit.

2. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 1, characterized in that: The concentrate outlet of the reverse osmosis unit is connected to the inlet of the nanofiltration unit.

3. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 1, characterized in that: The reverse osmosis unit includes a primary reverse osmosis device and a secondary reverse osmosis device; The inlet of the first-stage reverse osmosis unit is connected to the outlet of the second pretreatment unit and the permeate outlet of the nanofiltration unit, respectively. The permeate outlet of the first-stage reverse osmosis unit is connected to the inlet of the second-stage reverse osmosis unit, and the concentrate outlet of the first-stage reverse osmosis unit is connected to the inlet of the nanofiltration unit.

4. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 3, characterized in that: The concentrate outlet of the secondary reverse osmosis unit is connected to the inlet of the primary reverse osmosis unit.

5. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 3, characterized in that: The first-stage reverse osmosis unit uses a brackish water membrane, and the second-stage reverse osmosis unit uses a seawater desalination membrane.

6. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 1, characterized in that: The first pretreatment unit consists of a heat exchanger, a dosing device, a flocculation sedimentation tank, and a microfiltration membrane device.

7. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 1, characterized in that: The second pretreatment unit consists of a heat exchanger, a dosing device, a flocculation sedimentation tank, and a microfiltration membrane device.

8. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 1, characterized in that: The nanofiltration unit is a high-pressure nanofiltration membrane device.

9. The low-energy-consumption ferric phosphate production wastewater treatment system according to claim 1, characterized in that: The evaporation unit is a forced circulation horizontal tube evaporator or an MVR evaporator.

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