Andrew Chryss

Titanium Powder from the TiRO™ Process

A new continuous process for the direct production of CP titanium powder is being developed at CSIRO. The TiRO™ process has two major steps. The first step is conducted in a fluidised bed where titanium tetrachloride and magnesium powder react to form small (1.5 µm) titanium metal particles uniformly dispersed inside larger spheroidal magnesium chloride particles with an average particle size of 350 µm. The second step involves vacuum distillation in which the magnesium chloride is removed from the titanium. During vacuum distillation the magnesium chloride is volatilised and the micron sized titanium particles come together to form partially sintered predominantly spheroidal porous particles with a similar shape to the starting particle, some which appeared to be hollow. A mechanism for their formation is proposed. The spheroidal particles are all lightly sintered together. The vacuum distilled product was very lightly ground to liberate the spheroidal particles which had an average particle size of about 200 µm. With further grinding an angular Ti powder was produced. The ground titanium was free flowing and had a tap density of 2.4 g/cm3.

A DNS Investigation of the Effect of Yield Stress for Turbulent Non-Newtonian Suspension Flow in Open Channels

The use of fixed-shape open channels in industrial processes is common in the mineral processing industry. With lack of fundamental understanding about the mechanisms involved in how a turbulent flow of a non-Newtonian carrier fluid transports suspension particles, direct numerical simulation may come into the research as a validation tool. Direct numerical simulation (DNS) of the turbulent flow of non-Newtonian fluids in an open channel is modeled using a spectral element-Fourier method. The simulation of a yield-pseudoplastic fluid using the Herschel-Bulkley model agrees qualitatively with experimental results from field measurements of mineral tailing slurries. The simulation results over-predict the flow velocity by approximately 40% for the cases considered, however, the source of the discrepancy is difficult to ascertain. The effect of variation in yield stress, flow behavior index, and assumed flow depth are investigated and used to assess the sensitivity of the flow to these physical parameters. This methodology is seen to be useful in designing and optimizing the transport of slurries in open channels.

A DNS Investigation of Non‐Newtonian Turbulent Open Channel Flow

The flow of non‐Newtonian fluids in open channels has great significance in many industrial settings from water treatment to mine waste disposal. The turbulent behaviour during transportation of these materials is of interest for many reasons, one of which is keeping settleable particles in suspension. The mechanism governing particle transport in turbulent flow has been studied in the past, but is not well understood. A better understanding of the mechanism operating in the turbulent flow of non‐Newtonian suspensions in open channel would lead to improved design of many of the systems used in the mining and mineral processing industries. The objective of this paper is to introduce our work on the Direct Numerical Simulation of turbulent flow of non‐Newtonian fluids in an open channel. The numerical method is based on spectral element/Fourier formulation. The flow simulation of a Herschel‐Bulkley fluid agrees qualitatively with experimental results. The simulation results over‐predict the flow velocity by approximately 15% for the cases considered, although the source of the discrepancy is difficult to ascertain. The effect of variation in yield stress and assumed flow depth are investigated and used to assess the sensitivity of the flow to these physical parameters. This methodology is seen to be useful in designing and optimising the transport of slurries in open channels.