An on-line model for estimating the melting zone in a blast furnace

Abstract

In a blast furnace the melting zone strongly influences the whole process operation. A thermodynamic model for on-line estimation of the position and shape of the melting zone is presented. In this model the upper part of the furnace is divided coaxially. The model is based on energy and material balances for the components. The heat exchange between descending burden and ascending gas is described by a volumetric heat exchange coefficient taking account of both convective and radiative heat transfer. Assuming a stepwise reduction of iron oxides by CO and H 2 as reducing agents the reaction kinetics is modeled with a three interface shrinking core model. Boundary conditions are generated from continuous process measurements e.g. top gas analysis and temperature profile at the stockline. Information from a horizontal gas and temperature profile probe installed about 3 m below the stockline is used for adapting process parameters. A set of differential equations is solved numerically for each coaxial part. The vertical coordinate where the temperature of the burden exceeds the melting temperature of the reduced iron oxides is interpreted as the upper boundary of the cohesive zone.