Effect of differential flow schemes on gas-liquid flow and liquid phase mixing in a Basic Oxygen Furnace

Abstract

At present, for about 70% steel production worldwide, a Basic Oxygen Furnace (BOF) is used to reduce impurities like C, Mn, P, S, Si, etc. present in liquid metal. In order to improve the mixing efficiency and therefore the quality of steel, bottom blowing plays a prominent role and is affected by several parameters i.e. gas flow rate, flow schemes, the number of bottom tuyeres used and their locations. In the present study, 3D transient Euler–Lagrange (EL) simulations of dispersed gas–liquid flow were performed in a 6:1 scaled–down cold flow model of BOF steel converter to predict the gas-liquid flow and mixing time for different bottom blowing schemes. The predictions of mixing time were verified using mixing time measurements performed using in-house developed miniaturized conductivity probes. Effect of various differential flow schemes on dynamics of gas-liquid flow and mixing time was investigated. The predicted spatially–averaged mixing times were found to be in a good agreement with the measurements, for various differential flow schemes considered in the present work. Among these schemes, W– and V–differential flow schemes, that provide variation of gas flow rate in θ–direction led to the best mixing. The mixing time for these schemes was found to be reduced by 25–30% than that of conventional uniform flow scheme. The dynamic differential scheme in which the inlet flow was changed with time, required additional time to attain a new flow field corresponding to the changed inlet flow condition and therefore required a longer mixing time. The experimentally verified computational model and the results presented in the present work will be useful to improve mixing in commercial BOF vessels.