A novel approach to determine the mixing time in a water model of an AOD converter

Abstract

During the argon-oxygen-decarburization (AOD) process high-chromium steel melts are decarburized by oxygen and inert gas injection through sidewall tuyeres and a top-lance. The tap-to-tap time of the AOD process depends mainly on the time which is necessary to produce a homogeneous distribution of all required components in the melt. This mixing time is correlated to the process time. Shorter tapping times lead to a higher productivity, lower energy consumption and lower operating costs. Prior to the reduction stage, the mixing behavior influences the melting of the solid slag layer after the addition of ferro-silicon. Fast and efficient melting of the solid slag compounds is essential to attain sufficient reduction rates. Conventional approaches to experimentally investigate the mixing efficiency in aqueous models (e.g. the 95%-mixing time criterion), yield results which show a large variance concerning the mixing time for a single operating point. In the present study a novel approach for the determination of the mixing time in a water model of an AOD converter is presented and verified. The results show a lower variance and an increased reproducibility as compared to the prior measurement technique. Using these experimental results, the vessel shape and the required volume flow rate of the AOD process gas can be optimized. Furthermore, numerical simulations can be validated using the presented results. The measurement technique can be utilized in water models representing other metallurgical processes. © 2012 ISIJ.