Drying of Water-Atomized Iron Powders

Abstract

The developed drying process is characterized by a combination of conductive and convective methods with parallel flows of the heat carrier and dried material in conductive heat-mass transfer and with countercurrent flows of the air–steam mixture and dried material in convective heat-mass transfer. After study of heat transfer and drying kinetics, the drying modes for water-atomized iron powder were optimized. The heat flux transferred by conduction through the inner wall of the drum to the dried iron powder is 3.45 • 10⁶ W/m² at the beginning of parallel flow and 0.4 • 10⁶ W/m² at the end. The heat consumption for drying at the optimum amount of the air supplied to the drum for convective heat transfer by countercurrent flow 983 kg/h reduces to 415 kJ/kg compared with 511 kJ/kg for 300 kg/h. Relative specific humidity of the air–steam mixture is 0.034–0.045 because of a large amount of dry air and high temperature, i.e., the mixture is very far from saturation, eliminating the condensation on dried powder.