Application of the Fuller–Thompson equation in sinter blend design to increase sinter productivity

Abstract

Sintering is an important phase of the iron-making chain, as it allows the usage of finer iron ore particles in the blast furnace whilst still maintaining furnace performance. An on-going challenge for sinter plants is to obtain higher productivity from their sinter blends, or maintain sinter productivity whilst using more financially attractive iron ores. One of the most effective means to reduced blend cost is to use a higher proportion of concentrated iron ores in the blend. The key characteristic of concentrated ores is that they have a finer particle size distribution (PSD) than traditional sinter feeds and are widely known to negatively impact sinter bed permeability and sinter productivity. In this study, various iron ore blends were used to demonstrate the effect that the PSD of the sinter blend has on granulation and subsequent sintering process parameters during laboratory-scale sintering. Particular focus was applied to the impact of the PSD of the layering material in blend (−0.5 mm). Cold bed superficial gas velocity (SGV) was correlated to the spread of the PSD within the layers around granule nuclei. Widening the PSD spread within the layer increased cold SGV due to a narrowing in the spread of the granule size distribution (GSD) and increase in mean granule diameter. The Fuller–Thompson (FT) blend exhibited increased SGV during sintering (hot SGV) which led to shorter sintering times. This was a result of an enhanced ‘hot SGV efficiency’ (a measure for the ratio of hot SGV to cold SGV) over what was anticipated based on the trend with mean granule diameter. Complete industrial blends were compared with blends designed to the FT equation at varying proportions of layering particles in the blends (−0.5 mm). At equal proportions of layering particles in the blends, the FT blends exhibited increased cold and hot SGV by up to 20% and 25%, respectively, and led to a maximum 10% decrease in sintering time. Further, blends designed to the FT equation enabled the incorporation of 4 wt-% more layering particles and still exhibited similar cold SGV, hot SGV and sintering times to the industrial blends.