electrodialysis

Electrodialysis device is an emerging water treatment equipment that uses ion exchange membrane and direct current electric field to selectively migrate ions of dielectric in the solution, thereby achieving the purpose of desalination, concentration, purification and refinement of the solution. Electrodialysis devices have a wide range of applications, including desalination and desalination of water, seawater concentration and salt production, refined dairy products, fruit juice deacidification and purification, chemical product production, as well as the pretreatment of pure water in industries such as food and light industry, high-purity water in industries such as electronics and hospitals, primary softening and desalination of boiler feedwater, desalination of brackish water into drinking water, and deep treatment of industrial wastewater. The device mainly consists of a positive membrane, a negative membrane, end electrodes, a common electrode, separators, clamping plates, porous plates, rubber gaskets, etc. In addition, silicon rectifiers, flow meters, filters, water tanks, etc. need to be configured.

1、 Working principle

There are many alternating positive and negative membranes in the electrodialysis device, which are separated into small water chambers. When raw water enters these small chambers, ions in the solution undergo directional migration under the action of a direct current electric field. The cation membrane only allows cations to pass through while retaining anions; The anion membrane only allows anions to pass through while retaining cations. As a result, some of these small chambers become freshwater chambers with very little ion content, and the effluent is called freshwater. The small chamber adjacent to the freshwater chamber becomes a concentrated water chamber that gathers a large number of ions, and the effluent is called concentrated water. Thus, ions are separated and concentrated, and water is purified.

2、 Application scope

Electrodialysis devices have the main advantages of simple process, high desalination rate, low water production cost, convenient operation, and no environmental pollution. They are widely used in desalination of water and are specifically applied in the following situations:

Desalination of seawater and brackish water. According to our experimental data, brackish water with a salt content of up to 60 grams per liter can be desalinated into drinking water, solving the problem of drinking water sources in desert areas.

Produce soft water (with a resistivity of 106 ohms per centimeter), which can be used as feed water for low-pressure boilers without the need for salt regeneration and can save about 20% of coal.

The pre-treatment of deep desalinated water and high-purity water adopts electrodialysis ion exchange method, which expands the scope of raw water use and is widely used in power, electronics, chemical, pharmaceutical, scientific research and laboratory applications. It reduces water production costs by more than 50%, saves about 80% of the acid and alkali used in ion exchange regeneration, and extends the regeneration cycle by more than five times. Used for purification in beverage and food processing to improve the quality of beer and soda.

Electrodialysis devices can also be used for chemical separation, concentration, and industrial wastewater treatment and recovery.

3、 Construction and assembly methods

1. Construction: The electrodialysis device consists of three parts: membrane stack, polar region, and compression device.

(1) Membrane stack: It is composed of a considerable number of membrane pairs.

Membrane pair: It consists of a cation exchange membrane and a separator A (or B); A negative membrane and a partition B (or A) are composed.

Ionic exchange membrane: It is a key component of electrodialysis and is a heterogeneous membrane produced by our factory, Shanghai Chemical Plant.

Partition: Divided into concentrated and fresh water partitions, alternately placed between the anode and cathode membranes to maintain a certain distance between them. Water flows along the plane of the partition, and current flows perpendicular to the plane of the partition. Partition thickness 0.9 millimeters

(2) The polar region includes electrodes, polar frames, and water conducting plates.

Electrode: For connecting to the power supply, our factory uses titanium coated ruthenium electrodes.

Polar frame: placed between the electrode and the membrane to prevent the membrane from sticking to the electrode and providing support.

(3) Compression device: It is used to compress the electrodialysis device, so that the membrane stack, electrodes, and other components form a whole without water leakage.

2. Assembly method: The assembly method of the electrodialysis device is represented by "stage" and "segment", and the membrane stack between a pair of electrodes is called "stage". Each membrane in the same direction of water flow is called a 'segment'. Increasing the number of stages is equivalent to increasing the desalination process, which means that the assembly method can be adjusted according to different requirements of freshwater production and effluent quality. Generally, there are several forms: one stage, one stage; One level multi segment; Multi level segment; Multiple levels and segments.

4、 Specification and Performance

Model Description of Electrodialysis Devices Produced by Our Factory

DKD 1-11-3×3-150

Dimensions Table of Diaphragm for Electrodialysis Unit

5、 Auxiliary equipment

In addition to the main body, the electrodialysis device must also be equipped with auxiliary equipment such as rectifiers, filters, acid washing facilities, water pump instruments, etc. For the convenience of users, our factory can provide a complete set of auxiliary equipment and instruments. We will now provide a list of auxiliary equipment that is compatible with electrodialysis (Table 2).

Several explanations in Table 2:

(1) This table is applicable for raw water with a salt content of ≤ 800 milligrams per liter. If the salt content of the raw water is greater than 800 milligrams per liter, the rectifier model needs to be adjusted according to the salt content.

(2) The calculation of desalination rate of electrodialysis device adopts DDS-11A conductivity meter, which is supplied with matching equipment

(3) When using a concentrated water circulation system, it is necessary to configure a concentrated water tank and a water pump. The concentrated water tank can be a plastic water tank with a capacity equivalent to 40% of the fresh water volume.

Main Equipment List

Ordering Instructions

1. The ordering unit must specify the specifications and models. If special specifications or other requirements are needed, additional explanations must be provided.

2. If supporting auxiliary equipment is required, please specify the requirements.

3. If the user needs our factory to design an electrodialysis system or assist in selection, detailed analysis data of raw water quality must be provided.