Influence of the temperature variation at the slag flotation plant in Aurubis, Pirdop on copper grade and recovery (ULiège)

Abstract

Aurubis, Europe’s leading copper producer and world largest copper recycler is running the metallurgical smelter in Pirdop, Bulgaria. The associated flotation plant forms an indispensable part of the smelter infrastructure, by processing on site the flash furnace and converter slags to recover by flotation a Cu concentrate which is then returned back to the smelter. It has been documented by Aurubis, that pulp temperature in the flotation section varies to a large extent function of outside factors. This fact inevitably influences the floatability properties of the copper bearing phases in the ground slag. The main aim of the work will be therefore to study the effect from the pulp temperature on copper recovery. The influence of related process relevant parameters like degree of grinding and minerals liberation, copper occurrence in the slag, slag mineralogy and metals deportment etc. will be also taken into account. Detailed mineralogical characterization of the products will be accompany the work performed in Liege using a SEM-based automated mineralogy platform. The experimental work will consist of replicating in the lab the rougher stage. To this end, batch flotation tests at the various temperatures as recorded at the plant will be performed with copper grade and recoveries established. The reagent scheme used on site will be followed strictly. The grindability of the input slag and the autogenous mill cyclone overflow will be determined likewise. The constantly decreasing content of valuable minerals in the ore bodies requires more energy, with sustainable mineral exploitation, recycling and reuse techniques being on the rise. Such an example is the Aurubis’ processing plant in Pirdop, Bulgaria, which performs valorisation of copper slags through flotation process. Indeed, the aim of this thesis is the investigation of the temperature influence on flotation of copper slags from Pirdop’s processing plant. In order to achieve this goal, an internship has taken place on site in Bulgaria, with the introduction to the facilities and the collection of sample material for the conduction of flotation experiments atthe GEMME lab in the University of Liege. A plant survey consisting of pH, Eh, temperature and Dissolved Oxygen measurements was carried out at the slag flotation plant of Aurubis. Collected samples, together with collector and frother utilized on the plant were shipped to Liege. First, a literature review focusing on the mineralogical and chemical background of the slag flotation study is provided. Secondly, a Design of Experiment (DoE) software assisted on studying the relationship between input and key output variables. Then, the mathematical foundations,necessary to understand how the quantity of flotation reagents and sample to be used for the completion of the tests, were provided. Thus, using the results of the different analytical techniques (XRD, XRF, ICP-AES, automated mineralogy with SEM-EDS, etc.), we attempt to estimate an empirical relationship linking higher flotation temperatures with better flotation recovery and vice versa.