Two-dimensional temperature distribution in a fixed bed at high spatial resolution visualized by in-situ measurement of iron-ore sintering during combustion

Abstract

Temperature history in the sinter bed is related to the quality of sinter produced via fixed combustion, but there are limited reports on the experimentally determined temperature distribution in the sinter bed. This study experimentally investigates two-dimensional temperature distribution and its time variation in the sinter bed during combustion by scanning 12 thermocouples in alumina tubes placed in the sinter bed. The thin alumina tubes were vertically inserted into the sinter bed, which enabled temperature measurement without disturbing the shrinkage behavior during the measurement. The temperature data of the thermocouples were reconstructed to numerically visualize the two-dimensional temperature distribution with high spatial resolution; the width of the layer above 900 °C increased from ~20 mm to ~100 mm around the central axis as the reaction proceeded, and the temperature near the wall was lower than that around the central axis. The unprecedented comprehensive data on the temperature distribution also enabled numerical validation of the reaction. The time course profile of the flame front speed (FFS) was visualized at each radial position; the FFS was ~10 mm/min near the central axis of the top layer and ~20 mm/min near the edge. Further analysis visualized the time variation of the gas flow rate at each radial position. Rietveld analysis of sinter samples showed a clear correlation between the temperature history during the reaction and the mineral phases, that is, calcium ferrites and Fe3O4. The temperature measurement technique of this study will provide data required for further improvement of charging systems and burners.