(602g) Interactions Among Operating Conditions, Electrostatics and Particle Entrainment in Gas-Solid Fluidized Beds

Particle entrainment is a key parameter in gas-solids fluidized beds , but its prediction is extremely difficult, with empirical correlations differing by orders of magnitude, even for standard systems and operating conditions.  One likely reason is that electrostatics are not considered in the entrainment experiments and in developing correlations.  However, recent studies at UBC have shown that entrained particles carry a net charge which can influence particle motion in the freeboard and bed hydrodynamics, because removal of fine particles of one polarity results in particles in the dense bed being charged oppositely.  This paper will present preliminary results of experiments in which we have measured simultaneously entrainment and charges on the entrained particles for binary particle systems and different operating conditions. These experiments are conducted in a three-dimensional pressured vessel of 150 mm inner diameter and 2 m height constructed of stainless steel, equipped with a distributor consisting of two stainless steel perforated plates. The degree of electrification in the bed is measured by four collision ball probes (stainless steel, 5.3 mm O.D.), located at different levels and directly connected to electrometers (Kistler Model 5010B Digital Electrometer). The charge density of entrained particles in the freeboard is measured by a sampling pipe constructed as a Faraday cup. An instrumented stainless pipe (ID=38.1 mm, L= 400 mm) coated with Ni is installed in the reactor exit line to measure the electrical current transferred from entrained fine particles to the metal pipe from collisions.