Gas flows and mixing in models of the Inco flash smelting furnace

The flow of gases in the Inco flash smelting furnace has been studied, with the primary objective of improving the mixing of gases in the uptake. Experimental trials were performed in physical models of the furnace gas space in which the flow patterns were examined by means of flow visualization, tracer mixing studies and velocity distribution measurements. Two different models of the flash furnace and uptake have been built and operated: a 1/20 linear scale water model and a 1/5 linear scale air model. Similarity of the flow patterns in the uptake was expected between the models and the plant, given the close agreement of the scaling criteria.;These experiments indicated that the most significant factor affecting the mixing in the uptake is the afterburner configuration. In the range applicable to the plant operation, Reynolds number and jet momentum were found to have little effect on the mixing in the uptake. The afterburner configuration which provided the best mixing conditions, had staggered opposite pairs of jets flowing at 90° to the longitudinal axis of the furnace. The staggered jet arrangement allowed for maximum coverage of the uptake cross-section while keeping the opposing jets close enough that they still interact. This configuration was implemented in the plant at Copper Cliff in 1996.;A mathematical model has been developed using the computational code FLUENT v 4.5 to simulate the flow of gases in the air model. The principal objective was to determine whether the mathematical model could successfully simulate the flow patterns observed in the air model without the addition of afterburner flow in the uptake. The mathematical model predictions suggest that the furnace flow is very prone to become asymmetric. The results of the numerical simulations indicated that very small inequalities in the jet angles or jet flows can lead to asymmetric flow.;The predicted asymmetric flow conditions and measured dimensionless fields were qualitatively similar. The steady state numerical model cannot account for the temporal flow instability at the transition between the furnace and uptake, as was observed in the physical models. The flow instability at this transition produced a pulsating-type flow pattern, which was driven by cyclic imbalances of pressure in the system.;In the furnace space, the turbulent jets from adjacent nozzles flowed directly toward the model floor where they combined to form a single jet stream. The strong jet flows make it inevitable that extensive separation from the side walls and roof occurs. This effect is amplified by the abrupt junction to the uptake. Projecting the air model findings to the plant, the amount of recirculation was estimated to be about three times the flow through the burner jets.