Modeling of the influence of the bath blowing mode on mass exchange processes and slag formation in the oxygen converter

Abstract

Рurpose. Establish rational modes of bath blowing and slag formation when using traditional and experimental materials that ensure effective refining of steel from harmful impurities. To investigate the influence of the change in the hydrodynamic state of the converter bath on the stability of the lining of problem areas of the converter and the loss of metal with removal, emissions, with metal balls merging with the slag. Method. The work uses methods of cold and high-temperature modeling of the steel smelting process. When conducting experiments on cold modeling, the mode of penetration of gas jets into the liquid on the sample and the model was observed with the provision of Lrz/Nv (model) = Lrz/Nv (converter). Nv is the depth of the bath on the model and the wor king converter. Lrz - the length of the reaction zone in high-temperature simulations was determined as the length of the primary reaction zone, and in the cold one - as the length of the jet section formed when the gas jet penetrates the liquid. These conditions, together with ensuring the similarity of the geometry of the model and the sample, were consi dered necessary and sufficient for obtaining data for qualitative and quantitative assessment of both the hydrodynamic state of the converter bath and the effect of changing the method and parameters of blowing the bath on the physicochemical features of steel refining according to the time of the process. An additional condition is compliance with the condition of equality of the ratio of the plane of the bath to the plane of the internal section of the nozzle of the blowing nozzle: (Sbaths/Snozzles) model=(Sbaths/Snozzles) sample on the model and sample. Scientific novelty. Theoretically substantiated and experimentally confirmed the expediency of using to determine the effect on physico-chemical processes and conversion in the converter bath of the blowing mode, for the characteristic of which the parameter - hydrodynamic factor equal to the ratio LrzI/Nv was chosen. In turn, the length of the reaction zone that remains when the gas jet enters the bath depends on the intensity of blowing: Lrz ~ K q0.4. For the first time, the parameter that determines the state of mixing of the bath during its oxygen blowing - LrzI/Nv - was used to determine the intensity of sulfur conversion into slag during the oxygen blowing of the iron-carbon melt of the converter bath for the range of changes in the carbon content in it 3.0...0.25. where LrzI is the length of the primary reaction zone, which is formed when the oxygen jet penetrates the metal melt. The primary reaction zone is the source of the formation of CO bubbles according to the reaction FeO + C = Fe + CO, which are responsible for the intensity of mixing of the bath through the formation of circulating flows of metal in the bath, which in turn are responsible for the transport of impurity elements to the metal-slag boundary. It is shown that in the given range of changes in the content of carbon in the metal melt, the dependence of the removal rate of sulfur from the metal into the slag on the hydrodynamic parameter LrzI/Nv is extreme. At this time, when the maximum mixing effect of the bath is achieved, in the presence of the necessary basicity of the slag phase, the speed of the desulfurization reaction for these conditions is maximum. In the future, in the case of the implementation of the traditional conversion scheme, which is characterized by a sharp increase in the content of iron oxides in the slag (15...17%), the speed of the desulfurization reaction decreased even with a sufficient speed of metal flows. Practical significance. Reducing the intensity of metal bath blowing in the conditions of steel smelting in a laboratory oxygen converter with upper oxygen blowing from 4.0 m3/t•min to 3.2 m3/t•min, while increasing the blowing time by 17.8%, increased the desulphurization rate . Bringing the desulfurization reaction to its fuller completion was achieved due to the rational organization of mixing the melt in the converter bath: the appropriate and effective rate of metal delivery to the reaction surface from the point of view of the completion of steel desulfurization ensured a higher speed of the desulfurization reaction at the border compared to more intensive blowing of the bath with oxygen metal-slag distribution. At the same time, the value of the indicator Ls =(S)/[S] increased from 6.4 to 10.5.