Public defence, Processing of Materials, MSc Iida Pankka

Title of the thesis: Thermophysical properties of refractory materials in copper smelting

Thesis defender: Iida Pankka
Opponent: Associate prof. Inge Bellemans, Ghent University, Belgium
Custos: Professor Daniel Lindberg, Aalto University School of Chemical Engineering

In copper smelting, batchwise operating matte converters, such as Peirce-Smith converters, are usually the vessels that pose the greatest challenges in refractory wear. Understanding and reducing refractory wear is important for reasons of safety, on-line availability and smelting cost.

In this thermal conductivity was studied in relation to material structure. Thermal stress is one of the causes of refractory wear. While thermal conductivity of as-delivered refractory bricks and pure substances, such as copper, has been studied, there is little information on the thermal conductivity of multiphase heterogenous materials such as refractory bricks. Thermal conductivity values are also important for modeling and engineering design.

This thesis features two different types of samples: refractory bricks and ladle slag linings. The refractory bricks were taken from two different industrial Peirce-Smith copper converters, one at Boliden Harjavalta smelter (Finland) and one at Boliden Rönnskär smelter (Sweden). The end-of-life ladle slag lining samples were taken from Boliden Harjavalta. The samples were studied using a mix of X-ray microtomography, SEM-EDS and laser flash analysis. FactSage was utilized for calculating specific heat and density for the thermal conductivity calculations.

The infiltrate of the bricks was found to consist of copper metal and low-iron matte. As the volume fraction of metal and matte rises, so does thermal conductivity. The thermal conductivity rise was found to be very moderate compared with the thermal conductivity of metallic copper. This can be explained by the infiltration filling randomly oriented porosity and thus failing to form radial conductivity pathways through the brick.

Keywords: refractory bricks, ladle slag linings, post-mortem analysis, thermal conductivity, copper matte, slag, copper

Thesis available for public display 7 days prior to the defence at Aalto University's public display page.