THE VISUALIZATION OF THE ELECTROCHEMICAL-BEHAVIOR OF METAL PARTICLES IN SPOUTED, FLUIDIZED AND PACKED-BEDS

The electrochemical behaviour of metal particles in spouted, packed an d fluidized bed electrodes can be visualized in the same way as in the electrochemical corrosion demonstration. The cathodic reaction, indic ated by bright red colour (grey in black-white photographs), occurs on the particles in contact with the cathode current feeder. The profile of red colour corresponds to the current density distribution. This i s relevant for all particles in the fixed packed bed and in the annulu s of the spouted bed, and for those particles in the fluidized bed whi ch are in contact with the cathode current feeder. All the particles i n the spout and fountain of the spouted bed and the majority of the pa rticles in the fluidized bed are not in contact wi th the cathode curr ent feeder. They are characterized by bipolar behaviour because the re sistance of the electrical transfer through the particle is less than that through the surrounding electrolyte. The anodic reaction, indicat ed by dark blue colour (black in black-white photographs), occurs on t he part of the particles in the direction of the cathode current feede r, while the opposite side of the particles is under the cathodic reac tion, visualized by bright red colour. The method described could be u sed for the optimization of three-dimensional electrodes.