TY - THES

T1 - Developing a refractory test method for Platinum-Group-Metals Smelters

AU - Tichy, Stefan

N1 - embargoed until 01-03-2026

PY - 2021

Y1 - 2021

N2 - Various changes in the smelting process have increased the aggressiveness of conditions in South African platinum group metals furnaces over the past decades. This manifests itself above all in significantly reduced lifetimes of the used copper cooling elements. Gaseous sulphur and chlorides in the off-gas have been identified as the main causes of this corrosive attack. In order to reduce wear and thus extend service intervals, various approaches are being pursued. In this work, two different refractory coatings for the protection of coolers are investigated, which have the potential to reduce the corrosion problem and require low effort to be applied. Both systems use the acid atmosphere resistant binder water glass. One rests upon SiO2, and is characterized by highest acid resistance, the other on SiC which has higher thermal conductivity. The investigations confirm the good resistance, adhesion, as well as diffusion-inhibiting effect of both coating materials for a stress period of at least eight hours. Attacked by pure gaseous sulphur, the maximum corrosion rate at 100 °C is 85.5 mm/y for bare copper. In experiments with one- to two-millimetre-thick SiO2 or SiC coatings, values of 10.3 and 11.1 mm/y, respectively, were achieved in this temperature range. The same trends are also observed in experiments with sulphur vapor and small amounts of gaseous HCl as corrosive species. From 197.0 mm/y at 120 °C in the uncoated state, the corrosion rate decreased to 6.8 (SiO2) and 6.0 mm/y (SiC) for the coated samples. Before the two coating systems can be used in field application, further studies are required to confirm sufficient adhesion also for longer exposure times.

AB - Various changes in the smelting process have increased the aggressiveness of conditions in South African platinum group metals furnaces over the past decades. This manifests itself above all in significantly reduced lifetimes of the used copper cooling elements. Gaseous sulphur and chlorides in the off-gas have been identified as the main causes of this corrosive attack. In order to reduce wear and thus extend service intervals, various approaches are being pursued. In this work, two different refractory coatings for the protection of coolers are investigated, which have the potential to reduce the corrosion problem and require low effort to be applied. Both systems use the acid atmosphere resistant binder water glass. One rests upon SiO2, and is characterized by highest acid resistance, the other on SiC which has higher thermal conductivity. The investigations confirm the good resistance, adhesion, as well as diffusion-inhibiting effect of both coating materials for a stress period of at least eight hours. Attacked by pure gaseous sulphur, the maximum corrosion rate at 100 °C is 85.5 mm/y for bare copper. In experiments with one- to two-millimetre-thick SiO2 or SiC coatings, values of 10.3 and 11.1 mm/y, respectively, were achieved in this temperature range. The same trends are also observed in experiments with sulphur vapor and small amounts of gaseous HCl as corrosive species. From 197.0 mm/y at 120 °C in the uncoated state, the corrosion rate decreased to 6.8 (SiO2) and 6.0 mm/y (SiC) for the coated samples. Before the two coating systems can be used in field application, further studies are required to confirm sufficient adhesion also for longer exposure times.

KW - Platingruppenmetalle

KW - Korrosion

KW - Feuerfestmaterial

KW - Beschichtungen

KW - Kupferkühlelemente

KW - Platinum group metals

KW - Corrosion

KW - Refractories

KW - Coatings

KW - Copper coolers

M3 - Master's Thesis

ER -