High‐pressure particulate expansion and minimum bubbling of fine carbon powders

Abstract

AbstractParticulate expansion and minimum bubbling parameters (n, u′t, umB, εmB) are measured for fine carbon powders (dp = 44 and 112 μm) fluidized with synthesis gas (H2/CO = 0.8) at pressures within the range 2,070 < P < 12,420 kPa in an industrial, pilot‐scale fluidized bed. Deviations between minimum bubbling (umB and εmB) and minimum fluidization (umf and εmf) conditions increase with increasing pressure, P. The expansion index, n, decreases with increasing P and always exceeds values recommended by Richardson and Zaki for solid/liquid systems. Particulate bed expansion for the fine powders is well characterized by the equations of Foscolo et al. and Abrahamsen and Geldart. The theory of Foscolo and Gibilaro adequately estimates the onset of bubbling for both powders at all P, provided that experimentally determined values of n and u′t, are applied. For the dp = 112 μm powder, the theory of Foscolo and Gibilaro is applicable with calculated values of ut and experimental values of n.