Effects of superficial gas velocity and temperature on entrainment and electrostatics in gas-solid fluidized beds

The effects of superficial gas velocity and temperature on particle entrainment and electrostatic charges in fluidized binary mixtures of glass beads were investigated in a column of 150 mm inner diameter and 2 m height. The degree of electrification in the bed was measured by four collision ball probes at different levels. The charge density of entrained particles in the freeboard was determined by a freeboard sampler constructed as a Faraday cup. An instrumented pipe coated with Ni in the reactor exit line measured the electrical current transferred from entrained fine particles by collisions. The particle entrainment flux and electrostatic charge inside the bed and freeboard region increased with increasing superficial gas velocity. Temperature had negligible effect on the entrainment flux over the limited range studied. However, electrostatic charges decreased and the charge polarity reversed as the bed temperature increased from 20 to 75 °C.