Viscosity Measurement And Prediction Model Of CrO_x-bearing Slag

Slag viscosity is a critical physical property which must been considered in the slag design and optimization faced in the pyrometallurgical ironmaking and steelmaking processes.Particularly,the viscosity of molten slag is the single most important physical property governing the transportation and recovery of metals.The accumulation of Cr-containing slag viscosity data can contribute not only to guiding industrial production but also to developing and expanding the viscosity calculation model.However,the low solubility and the different valence states of chromic oxide in metallurgical slags cause many difficulties in experiments,thus,the viscosity data of chromium bearing slag reported are very limited and not systematic.Some developed viscosity calculation models are also limited due to the lack of viscosity data of Cr-containing slag.In this paper,the cylinder rotation method was used and the viscosity and structure of slag containing Cr₂O₃ and CrO under different fluid properties are measured and detected based on the study of the characteristics of Cr-containing slag,the effecting factors are also analyzed.Finally,the viscosity prediction model of Cr₂O₃-containing slag is obtained.The main contents and results are as follows:(1)The characteristics of the slag containing chromium were discussed.The results show that with the increase of PO2 and the addition of structural modifier,the proportion of Cr³⁺ in the slag increases gradually,the addition of Cr₂O₃ and MgO will increase the solid fraction of the slag.The results show that the fluid properties of Cr₂O₃-containing slag will change.The actual post-experimental composition did not change compared to the weighed target composition and no characteristic peaks appear in most quenched samples,the valence of Cr in the Cr₂O₃-containing slags and the CrO-containing slags was proved as Cr³⁺ and Cr²+respectively.(2)When Cr-containing slag is Newtonian fluid,the increase of Cr₂O₃ and CrO content can reduce the slag viscosity and CrO has a better effect.With the increase of Al₂O₃ content,the viscosity of slag first increases and then decreases and the increase of MgO,FeO content and R will reduce the slag viscosity.(3)Compared with Cr-free slag,Cr₂O₃ containing slag could reduce Al₂O₃ content when the slag reach the maximum viscosity,combined with a large amount of MgO and form spinel and made the FeO-containing slags more complex with different multivalent metallic oxide.(4)The results of degree of polymerization showed that with the increase of Cr₂O₃,CrO,MgO,FeO and basicity and the structure of slag became simple.Cr³⁺,Cr²+,Mg²⁺ and FeC2+ existed in silicate slag as structural modifiers.The increase of Al₂O₃ content will make[AlO₄]tetrahedron transform to[AlO₆]octahedron,and the structure of slag changed from complex to simple.(5)When Cr-containing is non-Newtonian fluid,the viscosity of slag increases with the increase of solid fraction.The solid fraction determined the fluid property of slags.The fluid features of molten slag transformed from Newtonian fluid to non-Newtonian fluid when the solid rate is more than 10%or 10%>solid fraction>5%together with content of dissolved Cr₂O₃ decreases.(6)The optimization results of Iida model show that the fitting effect is better in the low viscosity region(0 Pa·S-0.3 Pa·S);the BP neural network model has high fitting degree and is suitable for Cr-containing slags with all fluid properties,which has great advantages and application potential.Through the above research,the fluid characteristics of Cr-containing slag were obtained,the viscosity data of Cr-containing slag were accumulated,the degree of polymerization and the effecting factors of Cr-containing slag were investigated and the viscosity prediction model for Cr-containing were acquired in this paper.All this could provide a certain theoretical basis for the production of Cr-containing metal.