A device for desalting or treating wastewater by electrodialysis is called an electrodialyzer.
(1) the structure of the electrodialysis device is composed of a membrane reactor, a polar region and a compacting device.
1) membrane reactor: its structural unit includes a positive membrane, a separator and a negative membrane, and a structural unit is also called a membrane pair.An electrodialysis apparatus consists of a number of membrane pairs, collectively called a membrane stack.The clapboard is usually made of l~2mm hard polyvinyl chloride board, and the board is provided with water distribution holes, water distribution flume, water flow channel, water collecting flume and water collecting hole.The function of the clapboard is to form a water chamber between the two layers of film, forming the channel of flowing water, and playing the role of water distribution and water collection.
2) pole region: the main function of pole region is to supply direct current to the electrodialysis device, lead raw water into the water distribution hole of the membrane reactor, discharge fresh water and concentrated water out of the electrodialysis device, and pass through and discharge polar water.The polar region is composed of a supporting plate, an electrode, a polar frame and an elastic backing plate.The role of electrode plate is to reinforce the plate and install in and out of the water pipe, commonly made of thick hard polyvinyl chloride board.The function of the electrode is to close the internal and external circuits and create a uniform direct current field in the electrodialysis apparatus.Graphite, lead, iron wire coated nails and other materials are commonly used for anodes.The cathode can be made of stainless steel and other materials.The pole frame is used to maintain a certain distance between the plate and the membrane reactor, forming the pole chamber and the passage of the pole water.Pole frame is usually made of thick mesh multi-channel plastic plate with thickness of 5~7mm.Pad plate to prevent water leakage and adjust the role of uneven thickness, commonly made of rubber or soft PVC board.
3) compaction device: it is used to form the pole area and the membrane pile into a watertight electrodialysis unit as a whole.May use the pressure plate and the bolt to tighten, may also use the hydraulic pressure to tighten.The basic assembly form of electrodialysis is shown in figure 17-4.In practice, dentsu often USES terms such as "level", "segment" and "series" to distinguish various assembly forms.The number of pairs of electrodes in an electrodialysis apparatus is called a "stage"; those with a pair of electrodes are called a first stage; those with two pairs of electrodes are called a second stage; and so on.In an electrodialysis apparatus, the membrane reactor part whose inlet and outlet directions are the same is called a section.