Influence of Process Parameters on Copper Content in Reduced Iron Silicate Slag in a Settling Furnace

Abstract

During the pyrometallurgical extraction of copper, a significant fraction of this metal is lost with discard slag, which decreases profits and overall copper recovery. These copper losses can be reduced by using a settling furnace, in which suspended droplets containing copper separate from slag under the influence of gravity. An industrial trial was conducted in a settling furnace to increase the knowledge of the effect of temperature and settling time on the copper content of slag, and thus enhance the settling process to increase copper recovery. Slag samples were collected from four sample points: the ingoing and outgoing slag stream, within the furnace during settling, and the granulated slag. The chemical composition of the slag samples was analyzed and compared between batches with different temperatures and settling times. The appearance of copper and its associated phases were analyzed using a scanning electron microscope with an energy-dispersive X-ray spectroscopy detector (SEM-EDS). The results indicated that the outgoing slag copper content increased with an increase in temperature, and it was also concluded to be influenced by the attachment of copper to spinels and gas bubbles. The results indicate that regulating the settling furnace temperature to a lower interval could increase copper recovery.

Effect of Sulfur Content on Copper Recovery in the Reduction Smelting Process

“…Thermodynamics and melting separation affect the recovery of copper in the reduction process. In other words, with the increase in sulfur content, the metal phase transfers to matte, which is more difficult to settle at the bottom [40]. In essence, it is not conducive to metal recovery in a limited time.…”

A Method for Synthesizing Iron Silicate Slags to Evaluate Their Performance as Supplementary Cementitious Materials

“…The bath temperature in the settling furnace, from where the industrial slag is tapped and granulated, was unknown for the slag used in the present study. However, reported operational temperatures vary between 1210 and 1288 • C [45,50]. Furthermore, toward the end of tapping the furnace, temperatures exceeding 1300 • C are common due to continued electrical heating [50].…”

“…The idea of including chromium(III) oxide was based on its characteristics in the industrial process. Chromium, coming from, e.g., refractories and electronic scrap, is a strong nucleation agent in industrial slags [44], leading to the crystallization of chromium-rich spinel phases [45]. Due to the importance of the amorphous content in SCM applications [28,46,47] and the lower activation energy for heterogeneous compared to homogeneous crystallization [48], chromium was considered significant to include for the relevance of the experimental approach.…”

Mineralogical Characterization of Historic Copper Slag to Guide the Recovery of Valuable Metals: A Namibian Case Study

“…The composition of the slag is dependent on the mineralogy of the ore, but it typically contains oxides of gangue elements such as iron, silicon, magnesium, calcium, phosphorus, and copper [ 21 , 22 , 23 ]. The slag also contains some proportions of copper matte that is mechanically dragged when tapping from the settling zone of the smelter crucible [ 24 ].…”