The Kroll process is a pyrometallurgical industrial process used to produce metallic titanium. It was invented in 1940 by William J. Kroll in Luxembourg. After moving to the United States, Kroll further developed the method in 1945 for the extraction of zirconium. The Kroll process replaced the Hunter process for almost all commercial production. Pyrometallurgical refers to a type of chemical metallurgy used to change metals, for example: roasting or smelting. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... Year 1940 (MCMXL) was a leap year starting on Monday (link will display the full 1940 calendar) of the Gregorian calendar. ... William Justin Kroll (born Guillaume Justin Kroll; November 24, 1889 - March 30, 1973) was a metallurgist from Luxembourg. ... Year 1945 (MCMXLV) was a common year starting on Monday (link will display the full calendar). ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Standard atomic weight 91. ... The Hunter process was the first industrial process to produce pure ductile metallic titanium, and was invented in 1910 by M. A. Hunter, an American chemist. ...

The 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 Mg (15-20% excess) at 800-850 °C in a stainless steel retort to ensure complete reduction: Rutile is a mineral composed primarily of titanium dioxide, TiO2. ... Ilmenite is a weakly magnetic iron-black or steel-gray mineral found in metamorphic and igneous rocks. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Titanium tetrachloride (or titanium(IV) chloride) is the chemical compound with the formla TiCl4. ... Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. ... The 630 foot high, stainless-clad (type 304L) Gateway Arch defines St. ...

2Mg(l) + TiCl₄(l) → 2MgCl₂(l) + Ti(s) [T = 800-850 ^oC]

Problems in this stage result from the formation of the lower chlorides TiCl₂ and TiCl₃. The MgCl₂ can be further refined back to magesium.) After several days reaction stops, the pressure rises, and the spongy titanium is crushed and melted into an ingot. General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... Titanium tetrachloride (or titanium(IV) chloride) is the chemical compound with the formla TiCl4. ... Magnesium chloride is composed of magnesium and chlorine and is a typical ionic halide, being highly polar and soluble in water. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... Titanium(II) chloride is a black solid with the formula TiCl2. ... Titanium(III) chloride, TiCl3, is a red-violet salt that decomposes at 425 °C. Categories: | ... Magnesium chloride is composed of magnesium and chlorine and is a typical ionic halide, being highly polar and soluble in water. ... [[Image:[[Gold bars|Gold ingots. ...

The resulting porous metallic titanium sponge, impurities, and unreacted magnesium are 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. Leaching is the process of extracting a substance from a solid by dissolving it in a liquid. ... This article or section does not cite its references or sources. ... An electric arc furnace is a system that heats charged material by means of an electric arc. ... [[Image:[[Gold bars|Gold ingots. ... Look up Vacuum in Wiktionary, the free dictionary. ...

History and subsequent developments

The Hunter process was replaced by the Kroll process that was invented by Kroll. The Kroll process has not been replaced by a molten electrolytic process because of redox recycling, diaphragm failure and dendritic deposition in the electrolyte solution. However another process, the FFC Cambridge Process, has been patented for a solid electrolytic solution, and there is a partial process for eliminating the titanium-sponge processing. This article is about the chemical process. ... The FFC Cambridge Process is an electrochemical method in which solid metal compounds, particularly oxides, are cathodically reduced to the respective metals or alloys in molten salts. ...

References

• P.Kar, Mathematical modeling of phase change electrodes with application to the FFC process, PhD thesis; UC, Berkeley, 2007.
• Habashi, F. (ed.) Handbook of Extractive Metallurgy 1129±1180 Wiley-VCH, Weinham, 1997.
• G. Z. Chen, D. J. Fray, T. W. Farthing "Direct Electrochemical Reduction of Titanium Dioxide to Titanium in Molten Calcium Chloride" Nature 2000, Volume 407, pages 361-4.