Determining changes in the temperature field of a graphitized hollow electrode during metal processing periods in ladle-furnace

This paper reports an analysis of the process of heating a graphitized hollow electrode (GHE) during steel processing in ladle-furnace. The results of the numerical modeling of electrode operation are given. The data on the temperature field of the electrode were obtained when electricity was supplied and during periods without electrical loading. Values of the Joule heat released at electrode operation during the periods of metal heating in ladle-furnace were calculated; they amounted to 1.11–1.15 MW/m3. Coefficients of the heat transfer by convection have been calculated for the inner and outer GHE surface: 1.60 and 1.80, and 5–17 W/(m2∙°C), respectively. Values of the electrode temperature gradient in the high-temperature zone were obtained, which, for the first heating period, reached 8,286 °C/m, for the third ‒ to 6,571 °C/m. It was established that during the cooling periods of the electrode, the temperature gradient is significantly reduced and amounts to the inner surface of 379 °C/m; to the outer surface ‒ 3,613 °C/m; the vertical plane to the end of the electrode ‒ 1,469 °C/m. The directions to improve the installation’s thermal work and reduce its resource intensity during out-of-furnace processing of steel have been defined. It has been determined that during the periods of electrode operation with current supply, significant values of the temperature gradient are observed, which are concentrated in the end part. During the periods of operation without current supply, a locally overheated zone forms, taking the shape of a torus flattened along the axis, which is created as a result of the accumulation of heat from the preceding period. The data have been acquired on the effect exerted by the gas supply through a hollow electrode on the parameters of formation of the high-temperature GHE regions. It has been shown that the supply of neutral gas through a graphitized hollow electrode at a flow rate of 0.05 m3/min shifts the high-temperature zone to the periphery by 3.5–4.2 mm, as well as reduces its height by 1.0–1.2 mm. The study reported here could make it possible to calculate expedient gas and material consumption for controlling the oxidation of metal and slag, to reduce the consumption of graphitized electrodes, to bring down energy- and resource costs for metal production

Effect of CRI and CSR on the softening-melting behavior of burden in the high temperature zone

The influence of coke properties on the softening and melting behavior of burden was investigated through high temperature reaction tests. The results indicated that with an increase in the CRI of coke, the T′10% and T′40% both decreased while the ΔT′1 increased. The higher CRI got, the lower Ts was. In other words, under the identical primary slag condition, the resistance of cohesive zone for gas would increase with the increasing of CRI, as a result, the ΔPmax and S both rose. Because the S increased with increasing of coke which was less than 5 mm, it is necessary for the improvement of permeability to increase the CSR of coke. Notably, the CRI and CSR could reflect the quality of coke at high temperature, consequently, they still can be used as the quality indices of coke in the cohesive zone.