Effect of Cerium Oxide on Acid Slag Viscosity
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EFFECT OF CERIUM OXIDE ON ACID SLAG VISCOSITY A. S. Kirichenko1 and S. M. Nekhamin2
UDC 669.4: 669.046.5: 669.046.582.5: 669.054.8
Results of calculating the viscosity of acid slags according to the most well-known models used in steelmaking plants for slags with high basicity are analyzed. It is found that with an error of 10%, the calculations of viscosity according to the Urbain model coincide most fully with known data from the slag atlas in relation to acid slags typical for processing spent ceramic-based automotive catalysts. Within the composition of the active coating based on platinum group metals applied to ceramic unit of an automobile catalyst there is extensive use of lanthanide metals, their oxides, and salts that improve product quality characteristics. Cerium oxide is used advantageously, and an increase in concentration of this oxide is confirmed by chemical analysis of a ground mixture of spent automobile catalytic converters supplied for recycling. However, none of the models take account the effect of cerium oxide on melt viscosity. A requirement for taking this into account gives rise to the importance of the task in question. In order to determine this effect, charge composition was calculated to obtain viscosity of 2 poise typical for the technique employed, a charge was melted in a 1 MW DC arc furnace, and melt viscosity was determined by an inclined trough method. Melt temperatures were measured when the viscosity was the same as in the previous experiment. As a result of these studies the effect of cerium oxide concentration on temperature at which values of similar viscosity are achieved is determined. The value of the previously unknown coefficient of the effect of CeO 2 on acid slag viscosity (equal to 2.24) is obtained, when it is considered as a network modifier in an Urbain model. Keywords: slag viscosity, acid slag viscosity, effect of CeO 2 on melt viscosity, inclined trough method, Urbain model, spent automobile catalytic converters.
Spent automobile catalytic converters are predominantly treated in electric furnaces, melting acid-resistant ceramic with transfer into slag and deposition of heavy metals of the platinum group on a furnace hearth [1–3]. In order to predict the minimum exposure time required in order to deposit all of the valuable components on a furnace hearth it is necessary to know melt viscosity. Currently the following mathematical models are well known making it possible to predict viscosity in relation to charge composition and melt holding temperature: Model based on optical basicity (OB), Shu, Riboud, Lida, Urbain, Mills, and Koiama [4–11]. Models are used in steel smelting production and calculations are made for slag with high basicity. In order to analyze the adequacy calculated results have been compared for these models with the results for viscosity from a slag atlas in the region typical for processing spent catalytic converters based on aluminum silicates and designated in Fig. 1 by letters A, B, and C [12–14]. Point A corresponds to 20% СaO, 40% SiO
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