Dehydroxylation of Limonite Ore for Magnetization Roasting: Phase Transformation and Kinetics Analysis

A multi-stage fluidization magnetization roasting is a promising method to treat limonite ore. The dehydroxylation of limonite ore is a key reaction in the pre-heating stage. In this study, the dehydroxylation mechanism of limonite was studied in a laboratory fluidization roasting reactor. The samples were characterized using in situ X-ray diffraction, Fourier transform infrared spectroscopy, and simultaneous thermogravimetry and differential scanning calorimetry analysis. The phase transformation and kinetics analysis were studied. Results indicated that the dehydroxylation occurred at the temperature of 250-350 degrees C with the vanish of hydroxyl functional groups (-OH). The dehydroxylation kinetics followed the 2-D diffusion (Jander) reaction model G(alpha) = [1 - (1 - alpha)1/2]2, and the calculated activation energy was 113.43 kJ center dot mol-1. This study is conducive to exploiting limonite ore resources using magnetization roasting technology.