Process
Refined rutile (or ilmenite) from the ore is reduced with petroleum-derived coke in a fluidized bed reactor at 1000 °C. The mixture is then treated with chlorine gas, affording titanium tetrachloride TiCl4 and other volatile chlorides, which are subsequently separated by continuous fractional distillation. In a separate reactor, the TiCl4 is reduced by liquid magnesium or sodium (15-20% excess) at 800-850 °C in a stainless steel retort to ensure complete reduction:
- 2Mg(l) + TiCl4(g) → 2MgCl2(l) + Ti(s)
Complications result from partial reduction of the titanium to its lower chlorides TiCl2 and TiCl3. The MgCl2 can be further refined back to magnesium. The resulting porous metallic titanium sponge is purified by leaching or heated vacuum distillation. The sponge is jackhammered out, crushed, and pressed before it is melted in a consumable electrode vacuum arc furnace. The melted ingot is allowed to solidify under vacuum. It is often remelted to remove inclusions and ensure uniformity. These melting steps add to the cost of the product. Titanium is about six times as expensive as stainless steel.
Read more about this topic: Kroll Process
Famous quotes containing the word process:
“... in the working class, the process of building a family, of making a living for it, of nurturing and maintaining the individuals in it “costs worlds of pain.””
—Lillian Breslow Rubin (b. 1924)
“A designer who is not also a couturier, who hasn’t learned the most refined mysteries of physically creating his models, is like a sculptor who gives his drawings to another man, an artisan, to accomplish. For him the truncated process of creating will always be an interrupted act of love, and his style will bear the shame of it, the impoverishment.”
—Yves Saint Laurent (b. 1936)
“I’m not suggesting that all men are beautiful, vulnerable boys, but we all started out that way. What happened to us? How did we become monsters of feminist nightmares? The answer, of course, is that we underwent a careful and deliberate process of gender training, sometimes brutal, always dehumanizing, cutting away large chunks of ourselves. Little girls went through something similarly crippling. If the gender training was successful, we each ended up being half a person.”
—Frank Pittman (20th century)