The influence of slag compositional changes on the chemical degradation of magnesia-chromite refractories exposed to PbO-based non-ferrous slag saturated in spinel

Abstract

In non-ferrous metallurgy the refractory life is application dependent, typically going from several months up to 2 years or more. Slag engineering is widely used to reduce the dissolution rate of a refractory lining by forming a solid protection layer at the slag-lining interface, thereby increasing the lining's lifetime. The non-ferrous slag in this paper is engineered to form a protective spinel layer. This phase, however, only forms near and at the slag-lining interface, while deeper inside the sample forsterite grains are detected, resulting in direct contact between the still unsaturated slag and the magnesia-chromite refractory phases. At this position the MgO dissolution increases with a factor 3-4 compared with the slag-refractory interface, attacking the bonding between grains and decreasing the brick's mechanical strength. As this happens deeper inside the sample, the spalling risk increases. Strategies to simultaneously reduce refractory dissolution and spalling are discussed.

Origin and sedimentation of Cu-droplets sticking to spinel solids in pyrometallurgical slags

“…This can be written as indicated in equation (6) and 7 (7) In this reaction scheme, the copper droplets and spinel solids are formed on the same location, which might also imply that a small fraction of Cu-oxide can be incorporated in the spinel structure. In literature concerning primary copper production, a similar reaction has been described where cuprous oxide may react with ferrous oxide by 21,24,36 28,37 The presence of magnetite was argued to play a key role in this higher growth rate. The cations in magnetite are characterised with an increased mobility, which serves as a possible explanation for the higher growth rate.…”

“…The cations in magnetite are characterised with an increased mobility, which serves as a possible explanation for the higher growth rate. 28,38,39 Consequently, all cations have an increased mobility, which serves as a possible explanation for the higher growth rate. 28 In the present work, the spinel layers/particles that form around the copper droplets are Fe-rich and the spinel solids can be considered as partially consisting of magnetite.…”

Investigation of High-Temperature Slag/Copper/Spinel Interactions

“…Nightingale and Monaghan [51] observed the formation of spinel crystals within seconds after the submersion of MgAl 2 O 4 in a slag containing CaO, Al 2 O 3 , and SiO 2 . Scheunis et al [52] investigated the interaction between magnesia chromite refractory and a spinel saturated PbO non-ferrous slag, for which the formation of a new spinel layer with a growth rate of 290.5 lm 2 /h was observed. Although this experiment was carried out on lab scale, it presents information relevant for industrial processes as it shows that sticking droplets can occur when all conditions are fulfilled to simultaneously form both spinel particles and copper droplets in the slag.…”

The effect of a temperature gradient on the phase formation inside a magnesia–chromite refractory in contact with a non-ferrous PbO–SiO2–MgO slag

“…PbO systems are known to deeply infiltrate the sample [15] and previous research [16] studied the behavior of such a PbO-SiO 2 -MgO slag in contact with the same refractory brick under isothermal conditions. The goal of this work is to determine the effect of the temperature gradient on the infiltration behavior of the slag, the formation of reaction phases and the modification in slag composition.…”