Smelting reduction of carbon-chromite composite pellets - Part 2: dissolution kinetics and mechanism

The kinetics and mechanism of the dissolution of carbon-chromite composite pellets into high-carbon ferrochromium melts were studied. It was found that the time required for the dissolution of unfluxed pellets was significantly longer than that for reduction. This indicates that pellet dissolution may be the limiting factor in determining the operating parameters for a proposed new process for the production of high-carbon ferrochromium using melt circulation. The dissolution process was considered to involve the phase boundary reaction as well as liquid-phase mass transfer of the metal-phase components to the bulk melt. For a 7.94-mm unfluxed pellet an apparent activation energy of 133 kJ/mol was obtained from the average dissolution rate. For unfluxed pellets experimental and theoretical results suggested that the dissolution process was influenced principally by disengagement of the metallic phase from the slag phase.