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Project

Plasma-driven Slag Fuming from Industrial Process Residue

Slags produced from secondary copper smelting contain a considerable amount of ZnO. These slags are treated in a slag fuming furnace, where the ZnO undergoes an endothermic reduction reaction by metallurgical coal and Zn is evaporated and recovered either as metal or zinc oxide dust. The submerged plasma slag fuming process is a new technology that uses electricity as energy source instead of fossil fuel burners. Instead of adding the reductant through tuyeres, it is pelletized and added through a separate feeding system. These changes enable increased process manoeuvrability, process intensification due to the high flame temperature of the plasma and reduced greenhouse gas emissions.

It is essential to know the limits of submerged plasma slag fuming to make utmost use of it. Therefore, in this study, Aurubis Beerse’s batch-type plasma-driven slag fuming furnace process model is developed in FactSage 7.0. A dynamic flowsheet-modelling approach is used to model the complex thermodynamic and kinetic interactions in the slag fuming furnace. The heat exchange between the slag bath, the freeboard and the water-cooled reactor walls were also modelled to have a full heat balance of the process. The model is used to study the rate-limiting factors of the process and optimize its parameters to achieve high process efficiency.

The model showed that the tuyere gas efficiency, which is the ratio of the heat transferred from the tuyere gas to the slag bath and the total heat in the tuyere gas, is an essential kinetic parameter as it affects the thermal and zinc fuming efficiency. However, it is sensitive to several process parameters such as bath temperature, height and viscosity. Petcoke reactivity, which is the amount of petcoke reacting in the slag bath per unit time, plays a role only for a brief period when the petcoke feed rate is varied. The simulation results, such as bath temperature and total ZnO produced, were consistent with the measured data.

Date:31 Mar 2017 →  1 Apr 2022
Keywords:Metal Extraction, Fayalite Slag, Zinc, Plasma, Slag Fuming
Disciplines:Materials science and engineering, Other materials engineering
Project type:PhD project