Ferrotitanium is produced mainly by aluminothermic reduction, in which titanium bearing feed is reduced by aluminium powder and the heat released by the reaction drives the charge through to completion. The recovery rate, meaning the share of titanium that finishes in the metal rather than in the slag or the dust, is decided by four controllable variables: the quality and sizing of the feed, the quantity and sizing of the aluminium, the blending of the charge, and the firing schedule.
Feed Quality: Rutile and Titanium Concentrate
Grade is the first lever on recovery. Rutile with a titanium dioxide content above about 90 percent and titanium concentrate above about 50 percent gives a hotter, more complete reduction, because a richer feed needs less slag forming gangue per unit of titanium and therefore retains more of the reaction heat in the metal. Placer derived concentrate generally reduces more favourably than primary ore because of its mineralogy and its lower content of refractory gangue.
A high ratio of iron oxide to titanium dioxide in the concentrate is also beneficial. The iron oxide reduction releases additional heat, improves the pre firing behaviour of the charge and gives a cleaner separation between metal and slag, which improves both the economic and the technical result of the run.
Particle Size of the Feed
Sizing has to be tight, because both extremes lose titanium. Feed that is too fine becomes airborne during charging and is carried off as dust before it can take part in the reaction. Feed that is too coarse presents too little surface area, so the aluminothermic reaction cannot complete within the thermal window and a proportion of the titanium reports to the slag instead of to the metal. Practical operating ranges are 100 to 160 mesh for rutile and 40 to 100 mesh for titanium concentrate, with as little oversize and undersize as screening can achieve.
Blend Ratio, Firing Temperature and Time
The ratio of titanium concentrate to rutile is normally held at about 3.5 to 1. Firing temperature is generally kept between 750 and 850 degrees Celsius, with a firing time of three to five hours. The schedule has to be respected at both ends: a temperature that is too low or a time that is too short leaves the reduction incomplete, while overheating or overlong holding drives titanium into the slag and increases losses. A well balanced charge reacts steadily, produces a fluid slag that separates cleanly, and leaves a sound ingot with little entrapped slag.
| Parameter | Practical range | Effect of deviation |
|---|---|---|
| Rutile titanium dioxide content | above 90 percent | Lower grade reduces reaction heat and recovery |
| Concentrate titanium dioxide content | above 50 percent | Dilutes the charge and raises slag volume |
| Rutile particle size | 100 to 160 mesh | Finer material is lost as dust, coarser reacts incompletely |
| Concentrate particle size | 40 to 100 mesh | Outside the range the thermal reaction becomes uneven |
| Concentrate to rutile ratio | about 3.5 to 1 | Off ratio shifts the heat balance and slag fluidity |
| Firing temperature | 750 to 850 degrees Celsius | Too low leaves unreacted feed, too high drives metal to slag |
| Firing time | three to five hours | A short time gives an incomplete reduction |
Aluminium Reductant Quality and Sizing
The reductant is as important as the feed. An aluminium content of 98 percent or more is the usual choice, because the higher grade metal gives a cleaner and more complete reduction with less residue and less slag. Particle size then controls both the reaction rate and the aluminium consumption.
Oversized aluminium particles present a small surface area, so the reaction is slow and prolonged, heat is not concentrated where it is needed, and the metal and slag are difficult to separate.
An excess of fine aluminium is equally damaging, because fines burn and oxidise before they can reduce titanium, wasting reductant and lowering the effective yield.
A balanced size distribution reacts quickly, reaches peak temperature in the right place and leaves a fluid slag that releases the metal droplets cleanly.
Because the reductant is usually the most expensive input, matching its grade and size to the feed is normally the fastest way to improve the recovery rate on an existing furnace.
Charging Practice and Metal Separation
Charge preparation should be uniform: feed and reductant blended thoroughly rather than layered, so that the reaction front travels evenly through the crucible and no zone is left under reduced. After the reaction, allow the charge to settle so that the slag can be tapped or skimmed before the metal solidifies. A fluid, well heated slag separates cleanly, while a viscous one traps titanium rich droplets and directly reduces recovery.
Finally, the finished ferrotitanium should be sampled and checked against the agreed specification, with grades defined under GB/T 3282 and, for international trade, the corresponding ISO delivery specification for ferrotitanium. Consistent sampling of the metal and of the slag gives the plant the two numbers it needs to tell where the losses actually occur: titanium in the metal, and titanium locked in the slag.
Frequently Asked Questions
Q: What is the main cause of a low ferrotitanium recovery rate?
Incorrect feed or reductant sizing and a firing schedule outside the 750 to 850 degrees Celsius and three to five hour window.
Q: What aluminium grade should be used as the reductant?
An aluminium content of 98 percent or more is normally selected, because it gives a cleaner and more complete reduction with less residue.
Q: Which feed combination gives the best result?
Rutile above 90 percent titanium dioxide together with concentrate above 50 percent, blended at about 3.5 to 1.
Q: Why does an excess of fine aluminium hurt recovery?
Fines oxidise before they can reduce the titanium, so reductant is consumed without producing metal and titanium losses rise.
Q: Why keep the firing time between three and five hours?
Shorter times leave the reduction incomplete, while longer times at high temperature drive titanium into the slag.
Q: How can titanium losses be measured?
By assaying both the metal and the slag of the same heat, which shows whether the loss sits in unreacted feed or in entrapped slag droplets.
