Mieke Campforts

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

Cu-droplet losses in slags are an important problem in Cu-industry, limiting the metal recovery. An important cause responsible for the entrainment of copper droplet losses in slags is their sticking behaviour to spinel solids. In the present study, the interaction between spinel solids and Cu-droplets is investigated in an industrially relevant slag system (PbO–CaO–SiO2–Cu2O–Al2O3–FeO–ZnO) using two complementary experimental set-ups. Firstly the influence of the sedimentation time is studied and secondly the presence of entrained (sticking) droplets is studied as a function of height in the slag layer. Based on the experimental results, a mechanism that explains the sticking Cu-droplets is proposed. Finally, a model describing the sedimentation of sticking and non-sticking droplets is formulated based on the experimental data.

Wetting behaviour of Cu based alloys on spinel substrates in pyrometallurgical context

Metal droplet losses in slags are an important issue in copper industry. One significant aspect that promotes the entrainment of metal droplets in the slag is their attachment to spinel solids. In the present study, the wetting behaviour of copper alloys on spinel substrates has been investigated in the presence and absence of a slag phase. At first, the attachment was investigated using a synthetic slag containing spinel particles. Microstructural analysis of quenched slag reveals the presence of microdroplets sticking onto a surface of the spinel particles. Second, the metal–spinel interaction was investigated using the sessile drop technique. Wetting angle measurements were performed between Cu–Ag alloys and MgAl2O4 substrates. A non-wetting behaviour between the alloys and substrates was observed. The results suggest that the oxygen partial pressure and the amount of Ag in the alloy both influence the wetting behaviour.

Sessile drop evaluation of high temperature copper/spinel and slag/spinel interactions

Abstract Metal droplets sticking to spinel solids, present in metallurgical slag systems, play an important role in hindering the sedimentation of copper in slags. To understand this phenomenon, the interaction between spinel particles with Cu on one hand and with slag, on the other hand, was evaluated. A dedicated approach was applied, using an industrially relevant synthetic slag system PbO–FeO–SiO 2 –CaO–Al 2 O 3 –Cu 2 O–ZnO, pure copper and MgAl 2 O 4 substrates to represent the industrial slag, the entrained copper droplets and the spinel solids, respectively. Both the copper–MgAl 2 O 4 and the slag–MgAl 2 O 4 interaction were studied using sessile drop measurements, combined with an extensive microstructural analysis. Additionally, the effect of time on the slag–MgAl 2 O 4 interaction was studied using immersion experiments. Copper displayed a non-wetting behaviour on MgAl 2 O 4 , whereas slag displayed a reactive wetting and an interaction layer of (Mg, Fe, Zn)(Al, Fe) 2 O 4 spinel was formed at the interface, which was also observed in the immersion experiments. Moreover, the diffusion of MgO and Al 2 O 3 from the spinel substrate into the slag droplets was noted.

Study of the Effect of Spinel Composition on Metallic Copper Losses in Slags

In both primary and secondary copper production, copper losses in slags are a decisive factor confining the process efficiency. An important cause for mechanical entrainment of metal droplets in slags is their attachment to solid spinel particles present in the slag phase, hindering sedimentation. To further optimize the production process, it is important to gain insights in the fundamental mechanisms governing this attachment. In the present study, the influence of the spinel composition on the attachment of copper droplets is investigated. First, the attachment is studied in an industrially relevant synthetic PbO–CaO–SiO2–Cu2O–Al2O3–FeO–ZnO slag system. Second, the wetting of copper on two spinel substrates (ZnFe2O4 and MgAl2O4) has been studied in the absence of a slag system, by sessile-drop experiments. Based on the results of both types of experiments, a clear influence of the spinel composition on the sticking behavior of copper droplets is noted. These observations might be transferred to industrial processes to adapt processing parameters to diminish copper losses in industrial slags.

Investigation of Reactive Origin for Attachment of Cu Droplets to Solid Particles

AbstractBoth primary and secondary copper productions encounter a limitation in the process efficiency due to droplet losses in slags. One of the causes for the mechanical entrainment of these droplets is their interaction with solid spinel particles, hindering the sedimentation of the copper droplets. Previous experiments with synthetic slags provided insights into this interaction and yielded two possible mechanisms: separately formed droplets and particles become attached to one another due to fierce agitation of the slag and metal phases; or the spinel particles and metal droplets form as the result of a chemical reaction together with a new droplet or alongside a droplet that was already present in the system. This experimental study aims to investigate the hypothesis of the formation of copper droplets sticking to spinel particles due to a chemical reaction further. A slag that is initially free from Cu droplets was prepared. After creating controlled conditions to induce the chemical reaction, the formation of sticking droplets was observed. The results from this experiment therefore confirm the previously proposed reactive mechanism.