Modelling of injecting a ternary coal blend into a model ironmaking blast furnace

Abstract

The operation of ironmaking blast furnaces (BFs) involves several minerals such as iron ore, coals and flux. The practice of injecting a coal blend is widely employed in ironmaking BFs, typically binary blend or ternary blend. It is desirable to understand the overall performance of a coal blend and their individual behaviours of component coals. In this paper, a three-dimensional CFD model is described to simulate the flow and combustion of a ternary coal blend under simplified BF conditions. Three component coals in the ternary blend are tracked separately and undergo chemical reactions individually. The overall performance of ternary coal blend and individual behaviours of three component coals are analysed over the entire domain and quantified along the chamber axis, respectively, with special reference to flow, temperature, gas species and coal combustion efficiency. The simulation results show that generally, an inclined high-speed gas jet and coal plume are formed along the axis followed by an expansion and recirculation near the wall, resulting in the higher temperature and lower O2 at the lower part of the chamber. Individually, the coal of higher VM content devolatilises faster, shows larger particle size downstream, and reaches a higher burnout and a slightly higher particle temperature in the end. The non-addition is observed in predicting the burnout of the ternary coal blend due to the interactions among three component coals. The model provides an effective tool for ternary blend’s design and operation optimisation in ironmaking BFs.