Preheating and roasting characteristics of hematite–magnetite (H–M) concentrate pellets

Regressive orthogonal design experiments have been carried out based on the analysis of the oxidation and induration behaviours of individual magnetite and hematite pellets. The research shows that the optimal pellet preheating time and temperature, and roasting time and temperature change with hematite/magnetite (H/M) ratio. Under the conditions of preheating temperature 900°C, preheating time 10 min, roasting temperature 1275°C and roasting time 15 min, the compression strength of preheated and roasted pellets is found to be respectively more than 444 N/pellet (N/P) and 3993 N/P when the magnetite content in the pellets exceeds 20%. The pellet strengths meet the requirements of rotary kilns and blast furnaces respectively.