Thermochemistry of MgCr2O4, MgAl2O4, MgFe2O4 spinels in SO2−O2−SO3 atmosphere

The present paper investigates high-temperature sulphate corrosion of basic refractory ceramics containing magnesium spinels (MgAl2O4, MgFe2O4, MgCr2O4 and their solid solutions) widely used in metallurgy, chemical, ceramic and glass industry. This group of refractories are exposed to a number of destructive factors during a working campaign. One of such factors is gas corrosion caused by sulphur oxides. However, gas sulphate corrosion of basic refractory materials containing magnesium spinels, which has a great practical meaning for the corrosion resistance of the material main components, is not sufficiently examined. This work presents a thermodynamic analysis of (MgCr2O4, MgAl2O4, MgFe2O4)?SO2?O2?SO3 system aimed to calculate: i) the standard free enthalpy of chemical reactions, ii) the equilibrium composition of the gas mixture initially containing SO2 and O2 and iii) sulphates equilibrium dissociation pressure and equilibrium partial pressure for the reaction of SO3 with the spinels to predict the temperature range of corrosion products? stability. A thermochemical calculation provides information about equilibrium state in the analysed system. In real conditions the state of equilibrium does not have to be achieved. For this reason, the results of calculations were compared with experimental data. The experiment results were consistent with the theoretical predictions.

Development of Desulfurization Agent in RH Refining Process

Sulfur is a kind of harmful element in steel, and it is beneficial to molten steel to reduce the content of sulfur. On the basis of research, suitable desulfurizing agent and process parameters were chosen. The results of industrial test show that the average desulfurization efficiency is as high as 30%. In addition, there is a good result of T[O]&[N] control as well. With this testing program, the total content of FeO and MnO in ladle slag is bellow 12%, and it is beneficial to desulfurization. Increasing the content of CaO in desulfurization is conducive to desulfurization. On the other hand, There exists a serious problem in the test, and it is the erosion of RH immersion tubes, bottom of vacuum chamber, and refractory of ladle lining. In order to avoid or decrease this problem, basic refractory must be chosen.