The Relationship between Grinding Time of Mill Scale and Physicochemical Properties of the Produced Pellets and Its Reduction Kinetics in a Static Bed via Hydrogen

The obtained mill scale sample from the Egyptian Iron and Steel Company was screened on 4.75mm sieve from which the passed material was subjected to sieve analysis to determine the particle mean size. Furthermore, the passed material was subjected to grinding for specific periods of time (1 hour and its multiples up to 4 hours). Mill scale passing through the 4.75mm sieve and all grinding products were agglomerated on cold by pelletizing method by adding 2% molasses as a binder material. Then the agglomerated products were tested by drop damage resistance and compressive strength tests in both green and dry states to identify the quality of each. Some parameters were studied exclusively for the reduction process; grinding time, hydrogen flow rate, and reduction temperature. The agglomerated products were subjected to reduction by Hydrogen with different flow rates at different temperatures (600 - 1000ºC). All reduced pellets at 1000ºC were characterized chemically by using XRF, mineralogically by using XRD, microscopically by optical microscope and, finally by performing SEM-EDS analysis. The obtained results arose from this study showed that the maximum reduction percentage was 99.98% for pellets made from 3 hours grinding time series, at 2 L/min. H2 gas flow rate, 1000ºC reduction temperature, and 45 minutes reduction time. Kinetic study showed that the rate controlling step of all reduction reactions is that of diffusion with activation energy (Ea ) of 8.27 kJ/mole.