Structural transformation of beds during iron ore sintering

During iron ore sintering, material coalescence in the bed determines the physical properties of the agglomerated product. Sinter density and structural quantification by 2D image analysis were used to elucidate the degree of coalescence and densification achieved during sintering. In the first program, samples - representing increasing temperatures - were obtained from three locations down a sintered bed. Sinter density, determined by liquid pycnometry, was found to be strongly dependent on green granulated bed bulk density. Image analysis results indicated a strong dependence between sinter density and porosity. Results also show that more coalescence occurs for blends containing porous ores at increasing sintering temperatures. When sinter basicity and/or coke rate is low the effect of temperature on coalescence is less pronounced for all blends. The second program compared coalescence using 19 to 21 mm sinter from eight different pot tests and blends containing significant porous ores. For the same ore blend sintered under different conditions, measured trends in sinter density and porosity were in line with expectations but the changes were not large because the material in sinter has a high specific gravity of over four and changes in porosity were less than 5%. It was concluded that small increases in coke level could decrease sinter porosity by 5%, resulting in increased sinter tumble strength. Both programs show that when melt volume is high, small increases in temperature have a significant effect on coalescence in the flame front