Attrition characteristics of iron ore by an air jet in gas-solid fluidized beds.

The effects of superficial gas velocity (U g = 1.25–3.00 m/s) and distributor hole size (8.0–12.4 mm) on the attrition rate of iron ore in a gas-solid fluidized bed with 0.076 m ID × 3.7 m height with or without solid circulation have been determined. The particle density and the Sauter mean diameter of fresh iron ore were 3705 kg/m 3 and 357 μm, respectively. When the kinetic energy rate from the orifice was equal or > 180 J/s, we could determine an attrition rate trend by measuring the fractional mass of fine particle formation (under 500 μm fraction) during 30 min without solids circulation. In the experiments with solids circulation, the attrition rate was determined by measuring the fractional mass of fine particle formation (under 63 μm fraction; variation of threshold size). The attrition rate increases with increasing kinetic energy rate from the orifice (180 J/s < E K < 608 J/s). The kinetic energy rate from the orifice was calculated using the mass flow rate and orifice nozzle velocity. The correlation of the attrition rate with the kinetic energy rate from the orifice is Φ/N = 0.1214E K − 1.3587 above the jet length. [ABSTRACT FROM AUTHOR]