Development of a process model for a Peirce-Smith converter

Abstract: Copper was one of the first metals ever extracted and used by mankind. It is used for its unique properties, like corrosion resistance, good workability, high thermal conductivity and attractive appearance. New mines are opened to maintain a supply of primary feedstock to copper smelters. These new deposits are in many instances found to have a more complex mineralogy with several minor elements. Besides treating primary material, copper smelters also show an increasing interest in treating secondary material, such as copper containing scrap from waste electric and electronic equipment, which also have a complex composition.Waste electric and electronic equipment are first disassembled and upgraded by mechanical processing, generating a product stream called e-scrap, that can be added directly to the smelting processes as cold material or melted in a separate furnace producing a metallic alloy (referred to as black copper) and a slag phase. The black copper can be refined in different ways, whereof one is by using it as a secondary feed material for input to Peirce-Smith converters. Consequently the load of minor elements to the converter can be expected to increase with an increased treatment of e-scrap.This increased complexity of the raw material can potentially lead to smelter plants having to deal with a feedstock containing several minor elements such as; antimony, bismuth, arsenic, gold, silver, etc. in levels that can influence the ability to, in a cost effective way, maintain the final grade of the copper cathode. Process simulations can be an important tool for understanding the impact of process parameters on the product quality and for the purpose of process optimisation. In the present work a dynamic, non-equilibrium model based on thermodynamics over the Peirce-Smith converter has been developed. The non-equilibrium conditions have been simulated by introducing individual but linked segments. The purpose of using segments was to consider different reaction zones which yield different conditions within the converter. The model was validated using plant data and showed good agreement for the major elements. The agreement between plant and calculated data for Pb, and Zn was not as good and more work is required regarding this aspect. The model was used to investigate the influence on the distribution of Bi and Sb during addition of black copper with or without slag. When black copper is added to a blow, the removal of Bi and Sb becomes lower compared to a blow without addition of black copper. Similar result is obtained during addition of black copper with slag. To maintain a total removal of Bi and Sb in similar levels as a blow without black copper, the black copper should be added as early as possible during the converting operation.