Scaling phenomenon of cathode plate of electrolytic cell in electrolytic chlorine production technology
One of the more critical problems encountered in the preparation of chlorine-containing solutions by electrolysis is the fouling of electrode plates and cathode plates (usually in the cathode area). This is because during the electrolysis process, the pH of the cathode area increases, resulting in the formation of CaCO3 (Equation 6) and Mg(OH)2 on the cathode surface.
Cathode fouling can be removed by continuous rotating brushes or rotating blades, pickling, pulsed current, ultrasonic, reverse pole and other methods. Rotating brushes or rotating blades are usually used for continuous descaling on the surface of the circular cathode, and the on-line descaling is timely, but the long-term energy efficiency is low. Pickling usually uses low-concentration hydrochloric acid to regularly clean the scale on the cathode surface. The method is simple, but there is the problem of post-treatment of the hydrochloric acid waste liquid, and the pulse current usually produces a large number of air bubbles. It is the best automated in-situ descaling method at present. During the inversion process, the polarity of the cathode and anode is reversed, and the former scaled cathode is used as the anode for electrolysis, the pH value of the nearby area decreases, the cathode scale layer dissolves, and the cathode is descaled.
The use of the reverse electrode will significantly affect the catalytic activity of the electrode and the service life of the electrode. Therefore, when choosing electrode materials, in addition to considering electrode activity, it is also necessary to consider electrode life. Inverted electrodes will shorten electrode life. The rapid rise of the cell voltage indicates the peeling of the active film layer on the surface of the electrode material, that is, the failure of the electrode. At this time, the electrode needs to be replaced or repaired.