Green zero-emission desalted water production system

Abstract

The utility model belongs to desalted water production technical field discloses a kind of green zero-emission desalted water production systems, including cation exchange resin unit, anion exchange resin unit, first bipolar membrane electrolysis unit, nanofiltration unit, second bipolar membrane electrolysis unit, electrodialysis unit, third bipolar membrane electrolysis unit and desalted water tank.The utility model will anion exchange resin reproduction wastewater be handled respectively, by nanofiltration, electrodialysis and the combination of bipolar membrane electrolysis, make high-salt wastewater conversion into the regenerant of anion exchange resin unit, and acid, alkali are distinguished, and the discharge of all units can be utilized in system, energy consumption is greatly reduced, operating cost is reduced, reach green zero-emission and resource circulation.

Description

Technical Field

[0001] This utility model belongs to the field of desalination production technology, specifically relating to a green zero-emission desalination production system. Background Technology

[0002] Desalination is an important means of industrial water treatment. Currently, the main methods include reverse osmosis desalination, ion exchange desalination, electrodialysis desalination, evaporation desalination, and electroadsorption desalination. Reverse osmosis desalination is a physical method that does not require acid or alkali and has always been the dominant process for industrial water desalination. However, with the increasing demands for water conservation, emission reduction, and environmental protection, the 25% high-salt discharge from reverse osmosis dewatering systems has become a major factor restricting emission reduction in the desalination industry. Currently, most companies concentrate the 25% discharged brine through high-pressure reverse osmosis and then achieve zero discharge through evaporation and crystallization. However, such a zero-discharge process brings a series of problems: (1) It requires the addition of chemical hardening agents, which is not only troublesome to operate but also generates a large amount of solid waste. (2) High-pressure reverse osmosis systems not only have high energy consumption but also pose a risk of high-pressure operation. (3) High-salt crystallization in deep concentration systems also affects the membrane life. (4) The high energy consumption of evaporation and crystallization brings an economic burden to enterprises. (5) The salt produced by evaporation and crystallization cannot find an application market due to its quality and small scale. Some of it is even treated as solid waste. However, such solid waste cannot be eliminated and actually returns to the environment, thus losing the goal of serving the environment.

[0003] Therefore, it is necessary to find a green process to achieve zero emissions from desalination systems. Summary of the Invention

[0004] This invention addresses the technical problems of high energy consumption and high cost in existing desalination wastewater treatment systems by providing a green zero-emission desalination production system. The system separately treats the wastewater generated during the regeneration of anion and cation exchange resins. Through a combination of nanofiltration, electrodialysis, and bipolar membrane electrolysis, the high-salt wastewater is transformed into a regenerator for the anion and cation exchange resin units. Furthermore, acids and alkalis are separated, allowing all emissions from all units to be utilized within the system. This significantly reduces energy consumption and operating costs, achieving green zero emissions and resource recycling.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A green, zero-emission desalination production system includes a cation exchange resin unit, an anion exchange resin unit, a first bipolar membrane electrolysis unit, a nanofiltration unit, a second bipolar membrane electrolysis unit, an electrodialysis unit, a third bipolar membrane electrolysis unit, and a desalination tank. The outlet of the cation exchange resin unit is connected to the inlet of the first bipolar membrane electrolysis unit via a pipeline. The outlet of the anion exchange resin unit is connected to the inlet of the desalination tank and the nanofiltration unit via pipelines. The outlet of the nanofiltration unit is connected to the inlet of the second bipolar membrane electrolysis unit and the electrodialysis unit via pipelines. The concentrate outlet of the electrodialysis unit is connected to the inlet of the third bipolar membrane electrolysis unit via a pipeline. The acid outlets of the first, second, and third bipolar membrane electrolysis units are connected to the regenerated liquid inlet of the cation exchange resin unit via pipelines. The alkali outlets of the second and third bipolar membrane electrolysis units are connected to the regenerated liquid inlet of the anion exchange resin unit via pipelines.

[0006] In the above technical solution, the alkali outlet of the first bipolar membrane electrolysis unit is connected to the dehydration equipment.

[0007] The above technical solution also includes a rinsing unit, the outlet of which is connected to the rinsing water inlet of the cation exchange resin unit and the anion exchange resin unit via pipes.

[0008] In the above technical solution, the freshwater outlet of the electrodialysis unit is connected to the inlet of the nanofiltration unit via a pipeline.

[0009] Compared with the prior art, the beneficial effects of this utility model are as follows: This invention uses cation and anion exchange to produce desalinated water. At the same time, the cation and anion exchange regeneration can achieve the purpose of ion concentration in wastewater, replacing the traditional reverse osmosis membrane concentration process. This not only greatly shortens the salt concentration process chain, but also eliminates the need for the complex pretreatment of the reverse osmosis membrane desalination system.

[0010] Compared to the desalination wastewater treatment method of reverse osmosis concentration + evaporation crystallization, this invention treats the wastewater generated by the regeneration of anion and cation exchange resins separately. Through the combination of nanofiltration, electrodialysis and bipolar membrane electrolysis, the high-salt wastewater is transformed into a regenerator for the anion and cation exchange resin units. Furthermore, acids and alkalis are distinguished, and all emissions from all units can be utilized within the system. This significantly reduces energy consumption and operating costs, achieving green zero emissions and resource recycling. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of a green zero-emission desalination production system according to this utility model.

[0012] In the attached diagram, the following labels are used: 1 is a cation exchange resin unit, 2 is an anion exchange resin unit, 3 is a demineralized water tank, 4 is a cation exchange unit wastewater tank, 5 is an anion exchange unit wastewater tank, 6a is the first bipolar membrane electrolysis unit, 6b is the second bipolar membrane electrolysis unit, 6c is the third bipolar membrane electrolysis unit, 7 is a precipitation tank, 8 is a hydrochloric acid tank, 9 is a nanofiltration unit, 10 is a monovalent anion salt wastewater tank, 11 is a divalent anion salt wastewater tank, 12 is an electrodialysis unit, 13 is a sodium hydroxide tank, and 14 is a sulfuric acid tank. Detailed Implementation

[0013] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0014] like Figure 1 As shown, a green zero-emission desalination production system includes a cation exchange resin unit 1, an anion exchange resin unit 2, a first bipolar membrane electrolysis unit 6a, a nanofiltration unit 9, a second bipolar membrane electrolysis unit 6b, an electrodialysis unit 12, a third bipolar membrane electrolysis unit 6c, and a desalination tank 3.

[0015] The outlet of the cation exchange resin unit 1 of this invention is connected to the inlet of the first bipolar membrane electrolysis unit 6a via a pipeline. In one embodiment, a cation exchange unit wastewater tank 4 can be installed between the outlet of the cation exchange resin unit 1 and the inlet of the first bipolar membrane electrolysis unit 6a to temporarily store cation wastewater. Once the liquid level in the cation exchange unit wastewater tank 4 reaches 70%, the valve on the pipeline is opened to allow the wastewater to enter the first bipolar membrane electrolysis unit 6a.

[0016] The outlet of the anion exchange resin unit 2 of this invention is connected to the inlet of the demineralized water tank 3 and the nanofiltration unit 9 via pipes. In one embodiment, an anion exchange unit wastewater tank 5 can be installed between the outlet of the anion exchange resin unit 2 and the inlet of the nanofiltration unit 9 to temporarily store anion wastewater. Once the liquid level in the anion exchange unit wastewater tank 5 reaches 70%, the valve on the pipe is opened to allow the wastewater to enter the nanofiltration unit 9.

[0017] The outlet of the nanofiltration unit 9 of this invention is connected to the inlet of the second bipolar membrane electrolysis unit 6b and the electrodialysis unit 12 via pipes. In one embodiment, a monovalent anion salt wastewater tank 10 is installed between the outlet of the nanofiltration unit 9 and the inlet of the electrodialysis unit 12, and a divalent anion salt wastewater tank 11 is installed between the outlet of the nanofiltration unit 9 and the inlet of the second bipolar membrane electrolysis unit 6b for temporary storage of wastewater. After the liquid level reaches 70%, the valve on the pipe is opened to allow the wastewater to enter the electrodialysis unit 12 and the second bipolar membrane electrolysis unit 6b respectively.

[0018] The concentrated water outlet of the electrodialysis unit 12 of this invention is connected to the inlet of the third bipolar membrane electrolysis unit 6c through a pipe, and the fresh water outlet of the electrodialysis unit 12 is connected to the inlet of the nanofiltration unit 9 through a pipe, thereby realizing fresh water reflux.

[0019] The acid outlets of the first bipolar membrane electrolysis unit 6a, the second bipolar membrane electrolysis unit 6b, and the third bipolar membrane electrolysis unit 6c of this invention are connected to the regeneration inlet of the cation exchange resin unit 1 via pipes. The alkali outlets of the second bipolar membrane electrolysis unit 6b and the third bipolar membrane electrolysis unit 6c are connected to the regeneration inlet of the anion exchange resin unit 2 via pipes. In this way, the acid and alkali generated by the bipolar membrane electrolysis are used for the regeneration of the cation exchange resin unit 1 and the anion exchange resin unit 2, respectively.

[0020] Because divalent cation salts are prone to precipitation, they are generally not used as regeneration solutions. In this invention, the alkali outlet of the first bipolar membrane electrolysis unit 6a is connected to a dewatering device. In one embodiment, the alkali outlet of the first bipolar membrane electrolysis unit 6a is connected to a sedimentation tank 7, where the precipitated divalent cation salts are treated by a sludge dewatering device before being transported for disposal.

[0021] This invention also includes a rinsing unit. The outlet of the rinsing unit is connected to the rinsing water inlets of the cation exchange resin unit 1 and the anion exchange resin unit 2 via pipes. The rinsing drainage is discharged from the outlets of the cation exchange resin unit 1 and the anion exchange resin unit 2. For ease of operation, valves are installed at the outlet of the cation exchange resin unit 1, the inlet pipe of the cation wastewater tank 4, and the rinsing drainage pipe. Valves are also installed at the outlet of the anion exchange resin unit 2, the inlet pipe of the anion wastewater tank 5, and the rinsing drainage pipe. The material flow on each pipeline is achieved by switching the valves.

[0022] The main salts in fresh water are Cl⁻, SO₄²⁻, Na⁺, Ca²⁺, and Mg. 2+ The present invention first uses a cation exchange resin to adsorb Na⁺, Ca²⁺, and Mg⁺ from water. 2+ Next, the solution passes through anion exchange resin to adsorb Cl⁻ and SO₄²⁻ from the water, producing desalinated water for production. When the resin becomes saturated, a high-concentration regenerated solution is used for reverse exchange to restore the resin to its initial state, thus achieving recycling.

[0023] The wastewater generated after the regeneration of cation exchange resin unit 1 mainly consists of CaCl2, MgCl2, and NaCl. This wastewater is treated by the first bipolar membrane electrolysis unit 6a. Under the action of the electric field, the anions and cations undergo directional migration. The generated Ca(OH)2 and Mg(OH)2 are treated by the sludge dewatering equipment and then transported off-site for disposal. The generated HCl is used for the regeneration of cation exchange resin.

[0024] The wastewater generated after anion exchange resin regeneration mainly consists of Na₂SO₄ and NaCl. Through the NF nanofiltration unit, divalent and monovalent ions are separated to obtain monovalent anion salt wastewater (NaCl wastewater) and divalent anion salt wastewater (Na₂SO₄ wastewater), creating conditions for bipolar membrane electrolysis to produce acids and alkalis. For the divalent anion salt wastewater (Na₂SO₄ wastewater), it is treated by the second bipolar membrane electrolysis unit 6a, causing directional migration of anions and cations. The generated H₂SO₄ and NaOH are used for the regeneration of the cation and anion exchange resins, respectively. For the monovalent anion salt wastewater (NaCl wastewater), it is concentrated by the electrodialysis unit 12. The desalinated wastewater is returned to the inlet of the nanofiltration unit 9, while the concentrated wastewater is treated by the third bipolar membrane electrolysis unit 6c, causing directional migration of anions and cations. The generated HCl and NaOH are used for the regeneration of the cation and anion exchange resins, respectively.

[0025] Compared to the desalination wastewater treatment method of reverse osmosis concentration + evaporation crystallization, this invention treats the wastewater generated by the regeneration of anion and cation exchange resins separately. Through the combination of nanofiltration, electrodialysis and bipolar membrane electrolysis, the high-salt wastewater is transformed into a regenerator for the anion and cation exchange resin units. Furthermore, acids and alkalis are distinguished, and all emissions from all units can be utilized within the system. This significantly reduces energy consumption and operating costs, achieving green zero emissions and resource recycling.

[0026] The embodiments described above are merely preferred embodiments of this utility model and are only used to explain this utility model. They are not intended to limit the scope of implementation of this utility model. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of this utility model should be included within the scope of the patent application of this utility model.

Claims

1. A green, zero-emission desalination water production system, characterized in that, The system includes a cation exchange resin unit (1), an anion exchange resin unit (2), a first bipolar membrane electrolysis unit (6a), a nanofiltration unit (9), a second bipolar membrane electrolysis unit (6b), an electrodialysis unit (12), a third bipolar membrane electrolysis unit (6c), and a desalination tank (3). The outlet of the cation exchange resin unit (1) is connected to the inlet of the first bipolar membrane electrolysis unit (6a) via a pipe. The outlet of the anion exchange resin unit (2) is connected to the inlet of the desalination tank (3) and the nanofiltration unit (9) via pipes. The outlet of the nanofiltration unit (9) is connected to the inlet of the second bipolar membrane electrolysis unit (6a) via a pipe. The inlet ends of the membrane electrolysis unit (6b) and the electrodialysis unit (12) are connected by pipes. The concentrate outlet end of the electrodialysis unit (12) is connected by pipes to the inlet end of the third bipolar membrane electrolysis unit (6c). The acid outlet ends of the first bipolar membrane electrolysis unit (6a), the second bipolar membrane electrolysis unit (6b), and the third bipolar membrane electrolysis unit (6c) are connected by pipes to the regeneration inlet of the cation exchange resin unit (1). The alkali outlet ends of the second bipolar membrane electrolysis unit (6b) and the third bipolar membrane electrolysis unit (6c) are connected by pipes to the regeneration inlet of the anion exchange resin unit (2).

2. The green zero-emission desalination production system according to claim 1, characterized in that, The alkaline water outlet of the first bipolar membrane electrolysis unit (6a) is connected to the dehydration equipment.

3. The green zero-emission desalination production system according to claim 1, characterized in that, It also includes a rinsing unit, the outlet of which is connected to the rinsing water inlet of the cation exchange resin unit (1) and the anion exchange resin unit (2) via pipes.

4. The green zero-emission desalination production system according to claim 1, characterized in that, The freshwater outlet of the electrodialysis unit (12) is connected to the inlet of the nanofiltration unit (9) via a pipe.

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