Insights into the Formation of Titanium in the TiRO™ Process

The TiRO (TM) process is a new process being developed at CSIRO for the direct continuous production of titanium powder. The reaction takes place in a fluidised bed reactor (FBR) at temperatures between 650 degrees C and 712 degrees C. Titanium tetrachloride and magnesium powder with a d(50) around 150 mu m are injected into the FBR with an argon carrier gas. A seed bed of pre-existing product is required to initiate the reaction. The product particles are spheroidal and range in size with d(50) from 300 to 700 mu m. They comprise a matrix of magnesium chloride with micron sized titanium particles uniformly dispersed throughout. The likely reaction mechanism is discussed. Environmental Scanning Electron Microscopy (ESEM) and electron probe microanalysis of polished sections of product particles indicates the reaction starts on the surface of freshly added magnesium particles which become encapsulated with product. The reaction appears to continue on two fronts as the magnesium is consumed; at the interface of the magnesium core and surrounding reaction products and, at the outer surface of the particle. Completely reacted particles contain some or no internal voidage. Product particles are larger than predicted based on reaction stoichiometry. Their growth is attributed to agglomeration within the bed.