The basic structure of the electrolytic cell
According to the structure of the cell, the electrolytic cell is divided into two types: bottom type and bottomless type; according to the shape of the tank shell, it is divided into two types: square and rectangular; according to the anode structure, it is divided into pre-baked anode and continuous self-baked anode; according to the method of conduction, it is divided into Conductive side and upper conductive, etc.
The electrolytic cells used in the past are mostly bottomless rectangular side conductive continuous self-baking anodes. In recent years, the 160~350kA electrolyzer with bottomed upper conductive prebaked anode has been widely used.
It is divided into two types: soluble and insoluble. In the electrolytic cell for refining copper, the anode material is soluble blister copper to be refined. It dissolves into the solution during the electrolysis process to supplement the copper precipitated from the solution on the cathode. In the electrolyzer used for electrolyzing aqueous solutions (such as salt solution), the anodes are insoluble, and they basically do not change during the electrolysis process, but they often have a catalytic effect on the anode reaction on the surface of the electrode. In the chemical industry, insoluble anodes are mostly used.
In addition to meeting the basic requirements of general electrode materials (such as conductivity, catalytic activity strength, processing, source, price), the anode material also needs to be insoluble or passivated in strong anode polarization and higher temperature anolyte. , Has high stability. For a long time, graphite is the most widely used anode material. However, graphite is porous, has poor mechanical strength, and is easily oxidized to carbon dioxide. It is continuously corroded and peeled off during the electrolysis process, which gradually increases the electrode spacing and the cell voltage. When used for electrolysis of salt water solution, the overpotential of chlorine evolution on the graphite electrode is also higher.
In the molten salt electrolyzer, because the electrolysis temperature is much higher than that in the aqueous solution electrolyzer, the anode material is more stringent. The electrolytic molten sodium hydroxide generally uses steel, nickel and their alloys. Only graphite can be used for electrolytic melting of chloride.