Injection phenomena and heat transfer in copper converters

The injection dynamics and related accretion build up, as well as bath motion and heat losses in copper converters, have been investigated. The studies involved physical and mathematical models coupled with plant trials at four copper smelters to examine gas discharge phenomena, bath slopping and heat transfer within the converter. The laboratory work, performed on a 1|4th scale model of a converter, indicated significant tuyere interaction. Air discontinuously discharges into the bath with a frequency which increases with gas flow rate and is affected by the bath circulation velocity in the tuyere region. Measurements have delineated slopping behaviour in terms of tuyere submergence and the buoyancy power input to the bath. The industrial trials were conducted in Peirce-Smith, Hoboken and Inspiration converters under normal conditions. A tuyerescope attached to the back of a tuyere permitted the direct observation of accretion growth and the sampling of accretions during blowing. The tests indicated that the copper converter operates under bubbling conditions. Pressure pulses from the tuyeres revealed that in non-ferrous submerged injection processes three regimes of gas-liquid interaction can be identified: bubbling, unstable envelope and channelling. The relative dominance of each regime is affected by tuyere line erosion, viscosity of the bath and tuyere submergence. Analysis of the accretion samples revealed that accretions in the copper converter form mainly by the solidification of bath at the tuyere tip. Oxygen enriched air does not prevent accretion formation, but seems to produce a softer, easy-to-punch accretion. The type of puncher as well as punching frequency affect conditions inside the tuyere pipe and this could have an influence on accretion formation. The mathematical heat transfer model indicated that when the converter is out of the stack, heat losses through the mouth of the converter cause the internal surface to cool rapidly which may lead to freezing at the tuyere line and tuyere blockage when blowing is resumed. The temperature gradient, localized to within 60-80 mm of the refractory inside wall, changes markedly within the first minutes of the converter being out of stack. This may generate thermal stresses in the converter wall and contribute to refractory erosion at the tuyere line. Covering the converter mouth during out-of-stack periods significantly reduces the change in temperature gradient at the inside wall as well as heat losses from the converter.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat