7TH EUROPEAN COKE AND IRONMAKING CONGRESS - ECIC 2016

Effect of heating rate on the properties of two non-coking coals in thermal regime of tunnel kiln direct reduction of iron (TKDRI) process has been investigated. The low rate heating condition of raw materials in refractory crucibles of tunnel kiln was simulated in a vertical TGA for two different non-coking coals. The heating rates of 1.5, 3 and 7 oC/min from room temperature to 1100oC were chosen for non-isothermal heating of coals. Coal mass and volumetric changes were observed during the test by TGA and dilatometry analysis. XRD and scanning electron microscopy of raw coals and chars were used to analyse the effect of heating rates on coal and char structure. The results showed Maximum Rate of Devolatilization (MRD) shifts to higher temperatures with increasing the heating rate (HR). According to coal dilatometry, high volatile coal shows more sensitivity to heating rates than high-carbon coal. The effect of heating rate on char reducibility arises from changes in char reactivity and structural ordering. Lower heating rates lead to higher char reducibility and more ordered structure.