Raw Material Quality
The higher the quality of titanium concentrate and rutile, the better the tempering effect. When the grade of rutile is above 90 percent and the grade of titanium concentrate is above 50 percent, the recovery rate is higher; placer ore has a better tempering effect than primary ore. The higher the ratio of ferrous oxide to iron oxide in titanium concentrate, the better the roasting effect and the better the economic and technical indicators.
Particle Size Control
The particle size of titanium concentrate and rutile should be appropriate. If it is too fine, it is easy to fly and loss increases; if it is too coarse, the thermite reaction is insufficient and the recovery rate decreases. Therefore, the particle size of rutile is generally controlled at 100-160 mesh, and the particle size of titanium concentrate is controlled at 40-100 mesh. The ratio of titanium concentrate to rutile should be kept at about 3.5:1.
Calcination Practice
The calcination temperature is generally controlled at 750-850 deg C, and the calcination time is 3-5 hours. Inadequate calcination temperature and too short a calcination time affect the full progress of the unit thermal effect and recovery reaction, with a negative impact on the recovery rate.
Aluminum Charge Control
The higher the grade of aluminum particles used in the production of ferrotitanium, the better the recovery reaction; generally, aluminum particles with an aluminum content of more than 98 percent are used. The particle size of aluminum particles affects the speed of the chemical reaction and the utilization rate of aluminum. If the aluminum particles are too coarse, the specific surface area is small, the interface chemical reaction lasts for a long time, which is not conducive to the concentration of heat, and slag and iron are not easy to separate. If the aluminum particles are too fine, flying and burning losses increase, and the alumina content in the too-fine particles increases, resulting in insufficient aluminum.
The silicon in ferrosilicon can combine with the titanium in the alloy to form compounds such as Ti5Si3, which prevents the formation of aluminum compounds, reduces the amount of aluminum entering the alloy, improves the utilization rate of aluminum, and is beneficial to the improvement of the titanium recovery rate.
Unit Thermal Effect
The factors that affect the unit thermal effect are: the chemical reaction heat of the charge and the physical heat brought into the charge. Production practice shows that a low unit calorific value makes the recovery reaction difficult, slag fluidity poor, and slag-iron separation incomplete; a high unit calorific value makes the reaction intense with splashing and large process losses. From experiments, the recovery rate of titanium increases with the amount of aluminum, but too much aluminum reduces the unit heat effect, thickens the slag, and can cause the alloy aluminum content to exceed its limit; the amount of aluminum must be controlled within an optimal range.
Frequently Asked Questions
What raw material grades improve titanium recovery? Rutile above 90 percent and titanium concentrate above 50 percent give higher recovery, with placer ore better than primary ore.
What calcination parameters are used? Typically 750-850 deg C for 3-5 hours.
Why must the aluminum charge be optimized? Too little aluminum gives incomplete reaction; too much reduces the unit heat effect and can exceed the alloy aluminum limit.
Why is the ratio of titanium concentrate to rutile important? Keeping the ratio at about 3.5:1 with the correct particle sizes balances reaction speed and recovery: material that is too fine flies and is lost, while material that is too coarse leaves the thermite reaction incomplete.
What happens if the unit thermal effect is too low or too high? low unit calorific value makes the recovery reaction difficult and slag-iron separation incomplete, while a high value makes the reaction intense with splashing and large process losses.
