Modelling of Processes in the Trickling Zone of the Iron Blast Furnace

Phenomena taking place in the trickling zone of the blast furnace are not well enough understood for quantitative predictions. Models describing the blast furnace need adjustment of the heat transfer coefficients by one or two orders of magnitude to be able to predict realistic temperatures. This needs theoretical justification or methodology. Further, better knowledge of liquid hold-up and residence time distributions for the liquid phases, slag and metal, are needed for predicting reactions with greater confidence. The paper contains two parts. In the first part, it is hypothesised that some part of the heat transfer coefficient adjustment can be explained by evaporation-condensation of constituents of metal and slag, many of which have significant vapour pressures at the temperature prevailing in the bosh of the furnace. Some preliminary, and approximate, estimation of the enthalpy effects are made using a 1-d model for the trickling zone. For more realistic predictions one needs to estimate the spatial variation of the liquid hold-up and residence time, for both slag and metal. Since the data available are largely for cold model experiments, that too in one dimension, the subject is revisited to develop equations which can be used in a two-dimensional model. Though these formulations are in a preliminary stage, the equations have been incorporated into a 2-d model of the trickling zone, and the hold-up for slag and metal have been predicted. Further work is in progress