The electrical conductivity of fluidized beds of coke and graphite up to 1200°

Abstract Nitrogen‐fluidized beds of petroleum coke and graphite were heated by applying an a.c. voltage to electrodes submerged in the bed. Bed resistivities, calculated from the voltage and power input required to maintain a constant temperature, show a similar decrease in resistivity, for both materials, with increasing temperature up to 600°C., however, at about 600°C. the resistivity of graphite beds continues to decrease while that of coke beds goes through a minimum and then increases. This was attributed to arc formation at the contacts between coke particles when the applied voltage exceeds a critical value. Similar behavior was not observed for graphite as the operating voltage never exceeded the critical value.