Circulating fluidized beds (CFB) employed comprised: 0.0158 m riser diameter with 7.2 m height, 0.09 m riser diameter with 7.2 m height or 3.6 m height, and 0.254 m riser diameter with 10.5 m height. Measurements reported hen comprise solid hold-up and axial gas-mixing. Solid circulation rates up to 350 kg/m(2) s and gas velocities of 2, 4, 6, 8 ms were employed. Axial dispersion measurements using a non-adsorbed tracer confirm relatively low dispersion in the 0.0158 m dia riser. and for the 0.254 m dia riser a continual monotonic increase in axial dispersion with increase in air velocity up to 8 m/s. "Contact efficiency" (Dry) measurements were made for the 0.0158 and 0.254 m dia risers. in the 0.254 m dia riser, all "contact efficiencies" were measured at 100%.