Modelling and computer simulation of reagents diffusion in high temperature diffusion controlled heterogeneous reactions
Purpose: In this paper a computational method which takes into account convection in the melting metal and slag phases is discussed. Design/methodology/approach: A deterministic computational model of high-temperature heterogeneous reaction between metal and oxide melts has been developed. Findings: Transport of reagents and products of reaction occur simultaneously both by diffusion and by laminar natural convection of the melting metal and oxide fluxes. The convection-diffusion equations have been numerically solved by a finite-differences time-implicit discretization scheme. The model was implemented by program which had been written in C# language. The computations have been performed for desulfurization reaction between liquid metal and slag phases. Research limitations/implications: To verify the reliability of the model, the computed results have been compared with experimental data. The good agreement has been obtained. The numerical results agree well with the results which were found by two independent experiments. Originality/value: This computational model enables to obtain results, for example sulfur concentration changes along the x axis, which is very difficult, almost impossible, to get by experiment. Using this mathematical model allows to predict the distribution of elements in the metal during the refining process and to reduce expenses in selection of optimum process’ conditions, which provide the metal with required composition. This model can be used for quantitative analysis of the diffusion stage of the heterogeneous reactions.
X-ray TV study of the penetration of tin into a steel melt
A technique is developed and an X-ray TV study is performed to investigate the penetration of spherical tin samples into the steel 40Kh melt at a temperature of 1550°C. Cold spherical tin particles 1–2 in weight are found to dissolve in the tin-free steel at an initial rate of 180 ± 50 mol/(m2 s). A sample dissolves fully in less than 2 s. When a sample reaches the steel–gas phase interface, its dissolution rate decreases by many times. Separation with the formation of a two-phase system occurs at 1.6–1.9 mol % tin in steel. The density of the iron-based alloy is lower than that of the tin-based alloy. Pure tin and the saturated solution of iron in tin wet Al2O3-based refractory ceramic better than pure iron or its alloy with tin.
Oxidation rates of liquid copper and liquid copper sulfide
The kinetics of oxidation of liquid copper and copper sulfide were determined when the rate was controlled by the diffusion of the oxidizing gas to the melt interface. The method incorporated a capillary tube sample holder and the flux rate was measured by a quartz spring and cathetometer. The sample of copper sulfide was suspended from the balance in a tube furnace through which was passed a mixture of oxygen and argon gas. The oxidation of molten copper sulfide was found to proceed by the formation of copper followed by the formation of copper oxide. From the results, the diffusion coefficients of SO2 and O2 in argon were calculated over a temperature range of 1150° to 1350°C. The data compare well with the empirical equations for the diffusion of these gases. At lower temperatures, a different oxidation behavior is observed due to solidification of the sample.