A bipolar membrane stack separator design with magnetic stirring

Abstract

The application is a bipolar membrane stack design with magnetic stirring partition plate, which can realize the separation of easily settled colloid solution. The stack includes polar plate, polar chamber partition plate, ordinary partition plate, magnetic stirring partition plate, diaphragm, magnetic stirring device, end plate and flow channel joint. The bipolar membrane stack of the partition plate mainly includes polar plate, polar chamber partition plate, ordinary partition plate, magnetic stirring partition plate, diaphragm, magnetic stirring device, end plate and flow channel joint. The magnetic stirring partition plate of the electrodialyzer is attached with a smooth magnetic needle, which can realize uniform rotation in a limited space. The patent application aims at the problem that the existing bipolar membrane electrodialyzer cannot realize effective ion exchange of easily crystallized material system (because the material crystallization will block the flow channel and alkali chamber), prevents precipitation, configures magnetic stirring to realize uniform and stable outflow of the material, and improves the acid and alkali collection effect of the system.

Description

Technical Field

[0001] This invention relates to membrane separation systems, and in particular to a bipolar membrane stack separator design with magnetic stirring. Background Technology

[0002] Electrodialysis is a device that uses ion exchange membranes and a direct current electric field to selectively migrate electrolyte ions in water, thereby achieving water desalination.

[0003] Bipolar membranes are a novel type of ion-exchange composite membrane, typically composed of a cation exchange layer (N-type membrane), an interfacial hydrophilic layer (catalytic layer), and an anion exchange layer (P-type membrane). Under a direct current electric field, bipolar membranes can dissociate water, yielding hydrogen ions and hydroxide ions on either side of the membrane. Utilizing this characteristic, bipolar membrane electrodialysis systems, combining bipolar membranes with other cation and anion exchange membranes, can convert salts in aqueous solutions into their corresponding acids and bases without introducing new components; this method is called bipolar membrane electrodialysis.

[0004] The industrial application of bipolar membrane electrodialysis requires high standards for the feed water. Specifically, divalent and higher-valent cations in the feed water need to be largely removed to prevent the formation of hydroxide precipitates from metal ions. This places extremely high demands on the application scope of industrial electrodialysis.

[0005] Therefore, existing technologies and equipment need to be improved to adapt to more liquid systems. Summary of the Invention

[0006] This invention provides a bipolar membrane stack design with a magnetic stirring baffle to solve the above-mentioned problems.

[0007] One technical solution adopted in this invention is to provide a bipolar membrane stack design with a magnetic stirring baffle, including: a polar chamber baffle, a common baffle, a magnetic stirring baffle, a diaphragm, a magnetic stirring device, an end plate, and a flow channel connector.

[0008] Furthermore, the membrane includes anion exchange membrane, cation exchange membrane, and bipolar membrane, through which directional separation of ions is achieved.

[0009] Furthermore, the magnetic stirring baffle is embedded with a magnetic needle, which can achieve stirring at a certain speed under the action of an external magnetic field; the external magnetic stirring device utilizes the principle of like poles repelling and unlike poles attracting to use the magnetic field to drive the magnetic needle to rotate in a circle, thereby achieving the purpose of stirring the liquid.

[0010] Furthermore, the electrode plate is made of titanium-coated tantalum-niobium, the end plate is made of plexiglass, and the inlet and outlet water flows are connected to each liquid chamber; the flow channel connector is made of polyoxymethylene (POM) to enable liquid flow.

[0011] Furthermore, the polar chamber partition has no flow channels; the ordinary partition has centrally symmetrical flow channels.

[0012] Furthermore, the length of the magnetic needle matches the space left inside the magnetic stirring baffle, and its thickness is uniform and less than the thickness of the baffle.

[0013] Furthermore, the magnetic stirring device is connected to a corresponding control valve, which can adjust the magnetic stirring speed.

[0014] This invention relates to a bipolar membrane stack design with a magnetic stirring baffle, applicable to conventional electrodialysis. It enables the separation of easily settling colloidal solutions. The bipolar membrane stack includes electrode plates, electrode chamber baffles, ordinary baffles, a magnetic stirring baffle, a diaphragm, a magnetic stirring device, end plates, and flow channel connectors. The bipolar membrane stack with the baffle mainly comprises: electrode plates, electrode chamber baffles, ordinary baffles, a magnetic stirring baffle, a diaphragm, a magnetic stirring device, end plates, and flow channel connectors. The magnetic stirring baffle of the electrodialysis unit is equipped with smooth magnetic needles, enabling uniform rotation within a confined space. This invention addresses the issue that existing conventional electrodialysis methods produce crystal precipitation when the concentration in the concentrate chamber is too high, and bipolar membrane electrodialysis units cannot effectively separate easily crystallizing materials (because crystallization will clog the flow channels and alkali chamber). To address the need for uniform flow of solutions containing solid particles and prevent precipitation in existing electrodialysis, magnetic stirring is incorporated to achieve uniform and stable material outflow, improving the system's product collection efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a bipolar membrane stack design with a magnetic stirring baffle as described in this invention.

[0016] Figure 2 This is a schematic diagram of a bipolar membrane stack design with a magnetic stirring baffle as described in this invention, showing the structure of a conventional electrodialysis unit and a bipolar membrane electrodialysis unit with magnetic stirring baffles.

[0017] Figure 3 This is a schematic diagram of a bipolar membrane stack design with a magnetic stirring baffle as described in this invention.

[0018] The components in the attached diagram are labeled as follows: 1. Electrode plate, 2. End plate, 3. Electrode chamber partition, 4. Ordinary partition, 5. Magnetic stirring partition, 6. Diaphragm (yellow for anion exchange membrane, green for cation exchange membrane, and red for bipolar membrane), 7. Magnetic stirring device, 8. Flow channel connector. Detailed Implementation

[0019] The present invention will be further described below through specific embodiments. However, the scope of the present invention is not limited thereto.

[0020] Example 1

[0021] Attachment Figure 2 The components are stacked in sequence and reinforced with plexiglass. The bipolar membrane stack is then tightened with bolts, ensuring that each bolt is positioned uniformly. Five sets of effective repeating units are placed in the center of the bipolar membrane stack.

[0022] This case study uses five sets of bipolar membranes to form an electrodialysis membrane stack, organized into eight flow channels. These channels guide the flow from acid chamber inlet to acid chamber outlet, from alkali chamber inlet to alkali chamber outlet, from salt chamber inlet to salt chamber outlet, and from electrode chamber inlet to electrode chamber outlet.

[0023] The flow rate in each compartment is controlled at 30 L / h by a water pump regulating valve. The system operates for 1 hour using a 3A constant current DC power supply, with a 1 mol / L calcium methionine solution as the salt source for bipolar membrane electrodialysis. Using the bipolar membrane stack design with magnetic stirring of this invention, the alkali production efficiency of electrodialysis is increased by approximately 60% compared to the original non-magnetically stirred bipolar membrane stack. Furthermore, current efficiency is improved, and energy consumption is reduced.

[0024] Example 2

[0025] The difference between Example 2 and Example 1 is as follows:

[0026] The electrodialysis membrane stack consists of 10 sets of bipolar membranes, organized into 8 flow channels. These channels guide the flow from acid chamber in to acid chamber out, from alkali chamber in to alkali chamber out, from salt chamber in to salt chamber out, and from electrode chamber in to electrode chamber out.

[0027] The flow rate in each compartment was controlled at 30 L / h via a water pump regulating valve. The system operated for 2 hours using a 2A constant current DC power supply to treat copper gluconate produced by a factory using bipolar membrane electrodialysis. The control group with ordinary separators achieved an 82% Cu(OH)₂ recovery rate. Under similar energy consumption, the Cu(OH)₂ recovery rate using magnetically stirred separators reached over 98%. Compared to bipolar membrane stacks without magnetic needles, the final alkali concentration was also improved.

[0028] Table 1 is a comparison table of test results for Embodiment 1 and Embodiment 2 of the present invention.

[0029] Table 1 Comparison of test results for Example 1 of the present invention

[0030] project Bipolar membrane electrodialysis alkaline endpoint concentration (mol / L) Current efficiency (%) <![CDATA[Energy consumption per ton of soda ash (kWh / ton of Ca(OH)2)]]> Example 1 0.86 84 3010 Comparative Example 1 (without magnetic stirring) 0.52 56 5246

[0031] Table 2 Comparison of test results for Example 2 of the present invention

[0032] project Alkali concentration (mol / L) at the endpoint of bipolar membrane electrodialysis. Current efficiency (%) <![CDATA[Energy consumption per ton of alkali (kWh / ton Cu(OH)2)]]> <![CDATA[Recovery rate of Cu(OH)₂]]> Example 2 2.04 78 2996 98% Comparative Example 2 (without magnetic stirring) 1.21 54 5461 82%

Claims

1. A bipolar membrane stack with a magnetic stirring baffle, characterized in that, include: The system comprises a diaphragm, end plate, electrode chamber diaphragm, ordinary diaphragm, electrode plate, flow channel connector, magnetic stirring diaphragm, and magnetic stirring device. The magnetic stirring diaphragm is embedded with a magnetic needle, which stirs at a speed of 0-1000 rpm under the action of an external magnetic field. The length and width of the magnetic stirring diaphragm are both between 10cm and 100cm, matching the diaphragm. The width of the flow channel does not exceed 5% of the diaphragm width. The magnetic needle is externally coated with a PTFE-based film using a hot-melt method to prevent the needle from being worn down and contaminating the liquid phase when handling liquids that react with it. The magnetic needle is one of neodymium iron boron magnets, samarium cobalt magnets, alnico magnets, and ferrite magnets. The length of the magnetic needle is within the internal space of the magnetic stirring diaphragm. The magnetic needles are spaced and uniform in thickness; their diameter is smaller than the thickness of the partition; they are one of three types: olive-shaped, cylindrical with a collar, or long cylindrical without a collar, each designed for bipolar membrane electrodialysis of different liquid phase systems; the magnetic stirring device utilizes the principle of like poles repelling and unlike poles attracting to drive the magnetic needles in circular motion, thereby stirring the liquid; the magnetic field is based on the principle of electromagnetic induction, introducing an alternating magnetic field into each compartment to cause the magnetic needles to rotate, thus achieving liquid stirring; the magnetic stirring device includes an external control valve to control the switch and the magnitude of the magnetic field, and also includes a speed control module connected to relays with different coil windings to regulate the stirring speed.

2. The bipolar membrane stack with a magnetic stirring baffle according to claim 1, characterized in that, The diaphragm includes anion exchange membrane, cation exchange membrane, and bipolar membrane, which enable directional ion separation; the end plate is made of plexiglass and is designed to connect the inlet and outlet water flows of each feed chamber; the electrode chamber partition has no flow channels; the ordinary partition has centrally symmetrical flow channels; the electrode plate is made of titanium coated with tantalum and niobium; the flow channel connector is made of polyoxymethylene to enable liquid flow.

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