Towards More Reliable $${\text{ {PbO}-{SiO}}}_{2}$$ Based Slag Viscosity Measurements in Alumina via a Dense Intermediate Spinel Layer

Abstract

The goal of this work is to accurately measure the viscosity of an industrial secondary copper smelting slag. Established literature commonly performed such measurements in non-inert labware, such as alumina. Despite the fact that the dissolution of alumina into the slag was addressed as a source for errors, a comprehensive analysis of how this interaction affects the measurement reliability is hitherto lacking. Furthermore, the type of dissolution (direct or indirect) will influence the interaction kinetics. This work aims to verify a possible relation between the dissolution and viscosity measurement reliability. For this purpose, the infiltration depth during and time stability of four different slag (PbO-SiO 2 -CaO-Al 2 O 3 -ZnO-Fe 2 O 3 ) viscosity measurements were analyzed. Both in-situ viscosity measurements and post mortem SEM images of the interface were therefore analyzed. It was observed that a multiphase interfacial layer was formed upon alumina dissolution. This layer consisted of a spinel intermediate layer and an enclosed interfacial slag. EDX measurements confirmed the difference between the latter layer's composition and the bulk slag. Samples with a high interfacial slag viscosity yielded a dense spinel layer. As a result, alumina dissolved indirectly and more reliable viscosity measurements were obtained that were more stable over time. While samples with a low interfacial slag viscosity yielded a discontinuous spinel layer and therefore alumina could dissolve fast into the bulk slag, resulting in more unreliable viscosity measurements that varied over time.

Review on operation of spinel-containing slags of the non-ferrous metallurgy

“…Next to the mentioned spinel, another Cr-rich spinel is formed around the primary chromite grains of the refractory material. The formation of spinel phase between a similar slag system (PbO-SiO 2 -CaO-Al 2 O 3 -ZnO-Fe 2 O 3 ) and an alumina crucible is reported by Vergote et al [84]. During viscosity measurements, the slag reacted with the crucible forming a ZnAl 2 O 4 spinel layer as well as a Zn(Fe,Al) 2 O 4 spinel layer, indicating a parallel Al 2 O 3 dissolution and spinel crystallisation.…”

“…During viscosity measurements, the slag reacted with the crucible forming a ZnAl 2 O 4 spinel layer as well as a Zn(Fe,Al) 2 O 4 spinel layer, indicating a parallel Al 2 O 3 dissolution and spinel crystallisation. This mechanism seems to increase viscosity of the intermediate slag layer at the crucible, which may decrease refractory wear (of Al 2 O 3 -containing bricks) [84].…”

Viscosity experiments of slag-spinel suspensions: The effect of volume fraction, particle size, and shear rate

“…This avoids long slag-gas equilibration times. Moreover, as discussed in our previous work 19 , a significant source of error during viscosity measurements is the interaction of the slag system with the material of the crucible/spindle. In alumina labware, reliable viscosity measurements can be achieved by formation of a spinel passivation layer which results in indirect, slow alumina dissolution.…”

“…In alumina labware, reliable viscosity measurements can be achieved by formation of a spinel passivation layer which results in indirect, slow alumina dissolution. In this previous work 19 , several slag compositions were studied for their compatibility with alumina during slag viscosity measurements. One composition which yielded reliable viscosity measurements at 1200C (Table I, Compatible Liq.)…”

Viskositas: Viscosity Prediction of Multicomponent Chemical Systems

“…There may be 5-20% accuracy errors and 1-5% precision errors [7]. The experimental process of measuring viscosity is expensive both in terms of economics, since the equipment is expensive, in terms of time, since measuring viscosity requires homogenization of the temperature of the sample to be tested, and in terms of operator experience, since the minutiae of the experimental process can distort the final results [8][9][10].…”