Frequently asked questions
What is slag granulation?
Slag granulation is the process of converting molten metallurgical slag into solid granules. Dry slag granulation is an emerging technology that avoids the large volumes of water used in conventional wet granulation, recovers waste heat from the molten slag, and produces a glassy granule suitable for use as a supplementary cementitious material in construction.
What is low emission steelmaking?
Low emission steelmaking refers to technologies and process modifications aimed at significantly reducing the greenhouse gas emissions of integrated steel production. Approaches include substituting renewable carbon such as charcoal for coal and coke, improving energy efficiency, recovering waste heat from molten slag, and developing alternative ironmaking routes.
What are the kinetics of metallurgical reactions?
The kinetics of metallurgical reactions describes the rates at which chemical reactions occur between metals, slags, gases, and refractories at high temperatures. Understanding reaction kinetics is essential for designing efficient pyrometallurgical processes, as the overall rate is often controlled by mass transfer in the condensed or gaseous phase rather than by thermodynamic equilibrium.
What is pyrometallurgy?
Pyrometallurgy is the branch of metallurgy concerned with the extraction and processing of metals at high temperatures, typically above 500°C. It encompasses smelting, converting, refining, and heat treatment of ferrous and non-ferrous metals, and relies on the thermodynamic and kinetic behaviour of molten metals, slags, mattes, and gases.
What is melt chemistry?
Melt chemistry is the study of the physical and chemical properties of molten materials — including slags, mattes, metals, and salts — at high temperatures. It encompasses thermodynamic properties such as activity coefficients and phase equilibria, transport properties such as viscosity and diffusivity, and structural properties that govern interfacial behaviour. Understanding melt chemistry is fundamental to designing and optimising pyrometallurgical processes.
What is the role of slag viscosity in pyrometallurgical processes?
Slag viscosity affects almost every aspect of furnace performance. A slag that is too viscous will impede metal-slag separation, trap metal droplets, slow down reactions, and increase the risk of freeze-ups. A slag that is too fluid may increase refractory wear and cause operational instability. Viscosity is controlled through slag composition — particularly silica content, basicity, and the presence of network-modifying oxides — and temperature.
What causes slag foaming in steelmaking?
Slag foaming occurs when gas bubbles generated by chemical reactions — primarily CO from carbon oxidation — are stabilised within the slag rather than escaping freely. The tendency to foam depends on slag viscosity, surface tension, and the presence of fine solid particles. Controlled foaming is deliberately used in electric arc steelmaking to shield the arc and improve energy efficiency, but uncontrolled foaming can cause dangerous slopping events.
What is the difference between calcium ferrite and iron silicate slag?
Calcium ferrite slags are used in copper converting and are based on the CaO-FeOx system. They offer high copper solubility control, good impurity rejection, and compatibility with magnesia refractories. Iron silicate slags are based on the FeO-SiO2 system and are more common in copper smelting. The choice between them depends on the process, the feed material, the impurity profile, and the refractory system in use.