Modeling studies of fluid flow below flash-smelting burners including transient behavior

Abstract

Water-model experiments were carried out on 1:14-scale models of venturi, distributor, and jet-flow burners to ascertain flow patterns at varying Reynolds numbers (60,000 to 507,000) using time-lapse streak photography and video streak photography. Digital particle image velocimetry (DPIV) was used to determine the axial and radial velocities and to estimate the turbulence kinetic-energy field beneath the distributor burner. In the DPIV experiments, a temporal instability in the main jet exiting from the burner occurred at a Reynolds number=104,000, a Strouhal number≈3×10−3, and a large expansion ratio (shaft/burner-diameter ratio=10). The main jet usually pointed away from the burner inlet but was also observed to fluctuate and precess in a quasi-random fashion. Recom-mendations are made for improving flash-smelting burner performance by promoting conditions to eliminate precessing. The use of higher Reynolds numbers was recommended to improve both the use of shaft volume and the mixing of the concentrate particles and gas stream. A three-dimensional (3-D) mathematical model was used to simulate the water flow through the distributor burner, shaft, and settler. The predicted velocity field consisted of a main jet pointing away from the burner inlet and a large recirculation zone in the center of the shaft. The predicted and measured velocity magnitudes compared well in the recirculation zone, but the steady-state mathematical model predicted higher velocity values in the main jet than were experimentally determined.