Characterization of gas upward-solids downward countercurrent fluidized flow

Experiments were carried out in a specially designed 0.025 m i.d., 5 m high gas upflow-solids downflow fluidized bed to measure axial pressure gradien t profiles and actual solids holdups. Fluidized catalytic cracking (FCC) pa rticles (rho (p) = 1300 kg/m(3), d(p) = 70 mum) and two types of glass bead s (rho (p) = 2500 kg/m(3), d(p) = 123 and 332 mum) were used. The results s how that such counterflow is possible over a large range of operating condi tions. The flow development and friction are discussed in relation to the p ressure gradient profiles. Based on the changes of the mean particle veloci ty and the particle slip velocity, the particle agglomeration was studied. The actual solids holdup measured by a pair of pinch valves and the apparen t solids holdup calculated from the pressure gradients are also compared fo r different operating conditions. (C) 2001 Elsevier Science B.V. All rights reserved.