### Modelling and optimization of a rotary kiln direct

Table I. Model inputs used in the evaluation of kiln performance Design parameters Values Kiln internal diameter 4.34 m Kiln length 80 m Kiln inclination 1.5 Solids angle of repose 31 Operating parameters Range Kiln rotational speed 0.25–0.39 r/min Bed residence time 6–10 h C/Fe ratio (based on reducible Fe) 0.51–