SCALING CONSIDERATIONS FOR CIRCULATING FLUIDIZED-BED RISERS

The ratio between actual gas velocity to particle velocity in the hydrodynamically fully developed region of Circulating Fluidized Bed risers (CFB) may be approximated by phi = 1 + 5.6/Fr + 0.47Fr(t)0.41 = U(g)/epsilonV(p). This ratio, termed the slip factor, is about 2 at operating conditions characteristic of industrial risers several meters in diameter and agrees with observations of J. M. Matsen (in D. L. Keairns (ed.), Fluidization Technology, Vol. 2, Hemisphere, 1976, p. 135). The proposed relationship between the gas and solids velocity is an adequate first approximation to estimate gas and solids residence times, blower capacity and standpipe length.