Corresponding XRD spectrums are shown in Fig. Thus, it may be concluded that in these experiments melting temperature of Ti was not exceeded. X-ray diffraction spectrum of samples from the lower part of the slag bath after leaching with water: a Exp. Calcium fluoride is widely used as slag in the production of high-quality metals In the experiment No.
With multicomponent slag we can regulate reactor temperature, because of different electrical conductivity of the slag. However, elemental titanium was not found on the seed surface.
X-ray diffraction spectrum of slag samples from the seed stainless steel surface Exp. Therefore, the electrode mass loss in this experiment No. Experiments No. The developed liquid magnesium supply system Fig. This system is complex, and it was problematic to precisely dose magnesium, thus for test experiments No. Solid magnesium electrode feed system with a high-temperature seal. Composite electrode made of stainless steel with Mg tip were used Exp.
During experiment it was observed that melting of magnesium takes place at high speed. Distribution of Mg into the slag system was studied. It was found that most of the metal was in the form of individual spherical particles with a diameter up to few milimeters.
This result shows that magnesium input can be also done by melting Mg electrode. In experiment No. An increased duration of the experiment leads an increase in the dispersity of Mg particles distributed in the slag Fig. According to XRD analysis, the phase composition of impurities in a slag samples from upper, middle and lower part of slag bath is identical Fig. The composition of impurities in the slag located directly at the boundary of the slag melt - metal is characterized by the presence of a copper seed phase - intermetallic compound Fe 0.
Comparative analysis of the proposed X-ray diffraction patterns shows that as the distance from the seed surface increases, the intensity of the diffraction peaks of this crystalline phase decreases Fig. Elements that make up this alloy are enclosed in all slag samples Table 6. Moreover Mg OH 2 and MgO are formed during leaching as a result of the chemical interaction of magnesium with water. According to X-ray fluorescence analysis results Table 6 the largest amount of Mg is in the middle part of the slag bath.
Presence of the W in a slag composition is probably due to its overheating and slight electrode decay. Thus, X-ray diffraction and X-ray fluorescence analysis from different parts of the reactor allow us to conclude that slag in the reactor is quite well mixed if process is maintained for longer time.
Rather high liquid slag convection was predicted by numerical simulation shown in Fig. Experiment No. The results of XRD analysis of material after reaction confirmed the reduction reaction showing the presence of MgCl 2 and pure Ti Fig. However, during dismantling of the reactor and sampling of the material intense smoke emission was noticed.
It can be associated with the presence of unreacted titanium tetrachloride, which indicates an incomplete reaction. Thus, component mixing in the reactor may be incomplete or in some parts of the reactor temperature was too low for optimal reaction. In metallic droplets found in the slag bath volume near the electrode tip where temperature was highest, titanium content is about 50 wt.
XRF analysis of a metallic sediment from seed plate shows high magnesium content which indicates that in this zone temperature were too low Titanium content in slag bath metallic sediment is much higher reaching This experimental result demonstrates that it is important to maintain high temperature in as large volume fraction as possible. In this experiment it was possible to maintain sufficiently high temperature only in small zone between electrode and seed plate. This problem could be solved using larger reactor where cold near-wall zone will be relatively smaller.
Larger reactor with multiple electrodes and additional heating could be a possibility to improve Ti sedimentation on the seed plate. Series of experiments have been carried out for the implementation of the combined Kroll and electroslag processes.
It has been experimentally demonstrated that liquid slag may act as a membrane to separate metallic titanium from reaction products after TiCl 4 reduction with Mg. In this work metallic titanium is obtained and isolated in one step process. Relatively pure metallic titanium was obtained in some parts of the reactor in experiment No.
Titanium reduction reaction were experimentally verified in small scale experiment, showing that reaction takes place and metallic Ti distribution and can be altered by varying process parameters like electric parameters, electrode materials and slag composition. Tungsten electrode and stainless-steel seed are the best choice for process using NaCl based slag.
In further studies, to improve the purity of titanium, it is planned to use slags with boiling point above the melting point of titanium. This could prevent slag boiling and evaporation. In further studies it is planned to do more detailed experimental series to determine optimal electric and component injection regime. Larger reactor should be used because it is difficult to maintain high temperature in this small-scale reactor.
Ishwar, M. International Journal of Current Engineering and Technology. Google Scholar. Olkhov, Y. Thermodynamics of the titanium redox reaction from titanium tetrachloride by magnesium and the choice of optimal ways to intensify the titanium production, Investigations in Titanium Chloric Metallurgy. Zhang, E. A literature review of titanium metallurgical processes. Chunxiang, C.
Titanium alloy production technology, market prospects and industry development. Materials and Design. Article Google Scholar. Kroll, W. The Production of Ductile Titanium. Transactions of the Electrochemical Society. Nagesh, C. Mechanism of titanium sponge formation in the Kroll reduction reactor. Metallurgical and Materials Transactions B.
Zak Fang, Z. Powder metallurgy of titanium — past, present, and future. International Materials Reviews. Suzuki, R. Titanium powder preparation from TiCl 4 in the molten salt. Proceedings Of Powder metallurgy world Congress. Kyoto, Japan. Sathyapalan, A. Exploring Alternative Methods for Titanium Production.
Chumarev, V. Technological possibilities of manufacturing High-grade Ferrotitanium from crude ore. Russian metallurgy. Zhu, F. Klaproth, found a new metal oxide in a rutile ore in Hungary. At this stage, titanium oxide was separated from other oxides in iron sand or rutile ore; metallic titanium, however, could not be extracted by reducing titanium oxide. This was mainly due to the very strong chemical affinity between titanium and oxygen.
After the discovery of titanium by R. Gregor, numerous chemists attempted to extract metallic titanium, but with no success. The raw materials used in previous studies were oxide TiO 2 , potassium hexafluoro-titanate K 2 TiF 6 , titanium tetrachloride TiCl 4 , and other titanium compounds.
In , J. Berzelius reduced K 2 TiF 6 with potassium metal and obtained titanium containing a large amount of nitride. Nilson and O. Petterson succeeded in producing 95 pct pure titanium metal. In , M. Hunter succeeded in producing 99 pct pure titanium metal by reducing TiCl 4 with sodium metal in a closed steel container. The purity of the obtained titanium product excluding the gaseous elements was However, the titanium metal was brittle and not cold-workable because it was heavily contaminated with oxygen.
After improving the impurity control methods during the reduction process, Hunter obtained cold-workable and high-purity titanium. The Hunter process was put to practical use in the s and employed for large-scale production until In , Ruff and Brintzinger obtained 83 pct pure titanium metal by reducing TiO 2 with calcium metal Ca. Kroll, a Luxemburger metallurgist, obtained 98 pct pure titanium metal by using the same method.
However, the titanium product was not hot-workable. In , A. Despite its low productivity, the iodide process was employed to produce high-purity titanium for the semiconductor industry. In , W. Titanium metal was first introduced to the market in The Kroll process involves four sub-processes: 1 the chlorination process, where titanium oxide feed is chlorinated in the presence of carbon to produce TiCl 4 ; 2 the reduction and separation process, where TiCl 4 is reduced with magnesium metal, from which titanium sponge is recovered; 3 the crushing and melting process, where crushed titanium sponge is melted in a vacuum arc or an electron-beam furnace; and 4 the electrolysis process, where magnesium chloride MgCl 2 , separated in the reduction and separation processes, is electrolyzed into Cl 2 gas and magnesium metal.
Titanium occurs as an oxide in nature. Rutile ore with a TiO 2 grade of approximately 95 pct, upgraded ilmenite UGI , or upgraded titanium slag UGS is utilized as a feed material for titanium metal production. Rutile or UGI or UGS powder is placed into a fluidized bed furnace, where the powder reacts with Cl 2 gas in the presence of coke at approximately K. Crude TiCl 4 is obtained by the following carbochlorination reaction:.
Impurities such as FeCl x and AlCl 3 , which have higher boiling points than that of TiCl 4 K , are removed by condensation in this process. VOCl 3 is reduced by a reducing agent such as hydrogen sulfide H 2 S for conversion into vanadium tetrachloride VCl 4 , which has a higher boiling point than that of VOCl 3.
SnCl 4 and SiCl 4 are removed by a multistep distillation process. A schematic illustration of a steel reduction container used for titanium metal production from the TiCl 4 feed is shown in Figure 1. The container containing magnesium metal is kept under argon gas at K, and high-purity TiCl 4 is fed into the container. The reduction of TiCl 4 is described by the following equation:.
Schematic illustration of the reaction system in the Kroll process. Because this reaction is highly exothermic, the container is strongly heated during the reduction process. Therefore, the reduction temperature is rigorously controlled below K by regulating the TiCl 4 feed rate and cooling the container.
Titanium sponge contains MgCl 2 and unreacted magnesium metal inside the pores. MgCl 2 periodically tapped out from the reduction container during the reduction process is transferred to the electrolysis process. After the completion of the reduction reaction, MgCl 2 and the excess magnesium metal left in the titanium sponge are removed through vacuum distillation 0.
The vacuum separation of MgCl 2 and magnesium metal from the titanium sponge in a 10 t batch requires approximately 90 h. The evaporation of magnesium metal and MgCl 2 is endothermic, thus requiring a heat supply to assist the evaporation in vacuum.
Supplying heat deep inside the titanium sponge is technically difficult, particularly for a large-scale batch; therefore, vacuum evaporation takes a long time.
The vacuum separation process is followed by a prolonged cooling process. The titanium sponge recovered from the reduction container is mechanically separated using a die cutter and pulverized into small pieces. After quality inspection, the titanium sponge is transferred to the melting process for titanium ingot production.
Some parts of this titanium sponge, particularly the deposit near the inner wall of the reduction container, are heavily contaminated with iron. The most important feature of the Kroll process is the reliable production of titanium metal with a low oxygen concentration of approximately mass-ppm. Because titanium metal adheres to various locations in the container during the reduction process, its continuous recovery is difficult.
Therefore, a batch process involving container preparation, reduction, distillation, cooling, and titanium recovery is applied. Recently, large-scale facilities capable of producing 13 t of titanium per container have been constructed. However, the production speed of titanium is still low, and the duration of one cycle lasts more than 10 days, i.
In , Borchers and Hupperts reported titanium production by electrolysis,[ 22 ] where TiO 2 was electrolyzed in molten alkaline-earth halide. However, the characteristics of the titanium obtained by this process were unclear. The product was possibly heavily contaminated by oxygen and carbon. After the development of the industrial production of titanium by the Kroll process, many researchers have intensively studied the electrochemical reduction of titanium as a post-Kroll titanium production process.
Di-, tri-, and tetravalent cations are known as stable titanium ions. Tri- and tetravalent cations are stable even in an aqueous solution. Therefore, titanium metal production in an aqueous solution is thermodynamically not feasible. To date, an organic solvent that can be used as a non-aqueous solvent suitable for the reduction of titanium ions has not been found owing to the very strong chemical affinity of titanium to oxygen and nitrogen.
The electrowinning of titanium metal in molten salt has been studied intensively. In the s, some industrialization studies on electrolytic methods led to the construction of pilot plants. The methods were based on the electrolysis of titanium chloride in molten chloride. National Lead Co. New Jersey Zinc Co. Industrial production using the abovementioned electrolytic methods was expected, but the industrialization did not succeed.
Recently, Hsueh et al. Oki and Inoue studied the direct reduction of TiO 2 in a molten salt by electrolysis.
They placed TiO 2 powder in the vicinity of a cathode immersed in molten CaCl 2 and subsequently electrolyzed it to obtain titanium metal. This was a pioneering work; however, the atmosphere control capabilities of the electrolytic reduction method were inadequate. Therefore, the purity of the obtained titanium was low, and their work was not evaluated.
Numerous other electrolytic methods were investigated; however, none of them reached industrialization. The major reasons were 1 low current efficiency owing to the formation of multi-valent titanium ions, 2 difficult separation between the titanium deposit and the electrolytic bath, 3 low productivity due to a slower reaction rate than that obtained in metallothermic reduction, and 4 low space utilization efficiency in the electrolytic cell. To develop a next-generation process for replacing the low-productivity Kroll process, researchers intensively studied electrolytic methods in the s.
The industrialization of these methods, however, did not succeed. Since , processes utilizing both electrolytic and metallothermic reduction have been widely studied. Reducing agents were likewise diversified to include calcium, magnesium etc.
Among these combinations, the development of reduction processes of titanium oxide using calcium metal as a reducing agent advanced in particular. Ono and Miyazaki conducted the pioneering research on calcium deoxidation.
Okabe et al. This enabled a high deoxidation capability. Furthermore, Okabe et al. Following the development of electrochemical deoxidation, Fray et al. This work attracted the attention of numerous researchers, and similar studies have been intensively conducted worldwide Figure 3.
Ono and Suzuki likewise developed a direct production process of titanium metal from TiO 2 the OS process. Calcium metal electrolyzed on the cathode dissolves into molten CaCl 2 to form a strongly reducing molten salt. TiO 2 powder immersed into the molten salt is reduced to titanium metal powder. A potential diagram for the Ti-Cl-O system is shown in Figure 4 [ 39 ] to illustrate the difference between the reduction processes of the chloride and oxide feeds.
The horizontal and vertical axes show the partial pressures of chlorine and oxygen, respectively. Chemical potential diagram for Ti-Cl-O system at K.
During the actual reduction process from oxide feed, a complex oxide or oxycarbide might form. In the direct production process, low-cost titanium production is expected by omitting the chloride synthesis step points c to d and by making the reduction process continuous. The direct reduction of titanium oxide seems reasonable as a reduction process; however, an inexpensive method for the production of high-purity titanium oxide by removing iron, aluminum, silicon, etc.
At this stage, the purity of TiO 2 obtained by upgrading is 96 pct at most, and a more advanced process, like the Bayer process in aluminum smelting purity of Al 2 O 3 achieved is Calcium metal is the only practical reductant for the direct reduction of oxide raw materials TiO x to titanium metals with low oxygen-concentration.
However, the production of calcium metal is technically difficult and costly today. The development of an electrolytic cell with long-term high stability is difficult as calcium easily reacts with carbon and oxygen. There are numerous challenges that have to be addressed before realizing the practical application of titanium smelting utilizing oxide feed. When chloride feed is employed for titanium reduction, magnesium, sodium, and calcium have proved effective as reducing agents in the production of high-purity titanium.
The reduction of TiCl 4 with calcium and sodium is suitable for constructing a continuous reduction process because titanium powder product is obtained. However, an efficient cooling technology for the reactor and efficient utilization of the reaction heat is required as the heat generated in these reduction processes is greater than that in the magnesiothermic reduction of TiCl 4.
Furthermore, the removal of byproducts such as CaCl 2 and NaCl by evaporation is difficult because their vapor pressures are low. Instead, leaching or remelting separation at temperatures higher than the melting point of titanium metal should be conducted. A UK-based venture company, Metalysis, developed a pilot-scale electrolytic cell for the industrialization of the FFC process, producing low-cost titanium powder.
The Armstrong process is based on the sodiothermic reduction of TiCl 4 in the gas phase. Schematic illustration of reaction system in the preform reduction process PRP. The PRP has the advantage of scalability because the preform is suitable for homogeneous heat treatment.
Furthermore, the PRP has good anti-contamination ability because the preform is a self-supporting structure and its contact area with the reactor material is very small. Among electrolytic methods, a smelting process using titanium oxycarbide TiCO Figure 6 has been actively studied.
Titanium oxycarbide, obtained through the carbothermic reduction of TiO 2 , is used as the anode, and titanium metal is produced through electrorefining in a molten salt.
Schematic illustration of the reaction system in molten salt electrolytic refining process using oxycarbide anode. In , Wainer reported the development of oxycarbide electrolysis. In the Kroll process, titanium metal forms as a solid, hindering the construction of a continuous titanium production process. Therefore, the recovery of titanium products in liquid form has been attempted.
Halomet[ 54 ] proposed the magnesiothermic reduction of TiCl 4 at high pressure 0. However, the practical development did not succeed owing to the lack of suitable container materials and to the strict temperature control requirements. Recently, Ginatta developed an electrowinning process for molten titanium metal although its details are unclear. However, it seems that very rigorous and sophisticated thermal management inside the electrolytic cell is required.
Hard and Prieto[ 58 ] proposed an aluminothermic reduction of Na 2 TiF 6 in the presence of molten zinc metal Zn to recover the molten Zn-Ti alloy. Titanium sponge was recovered by removing zinc from the Zn-Ti alloy through vacuum distillation. Kimura et al. Deura et al. Recently, Kado et al. Schematic illustration of the reaction system in the magnesiothermic reduction of TiCl 4 using molten Bi as the collector metal. Subsequently, titanium metal is recovered by removing bismuth from the Bi-Ti alloy by evaporation.
When molten titanium alloy is utilized, the titanium product can be continuously recovered from the reduction vessel, and the construction of a continuous reduction process is anticipated. Fang et al. However, the oxygen in titanium is destabilized by hydride formation and removed, according to the following equation:.
Schematic illustration of the reaction system in the hydrogen-assisted magnesiothermic reduction HAMR process.
The use of magnesium metal as the reducing and deoxidation agent is advantageous because of its low cost compared with that of calcium metal. Very pure liquid titanium IV chloride can be separated from the other chlorides by fractional distillation under an argon or nitrogen atmosphere. Titanium IV chloride reacts violently with water.
Handling it therefore needs care and is stored in totally dry tanks. After the reaction is complete, and everything has cooled several days in total - an obvious inefficiency of the batch process , the mixture is crushed and washed with dilute hydrochloric acid to remove the sodium chloride. This is the method used in the rest of the world.
The method is similar to using sodium, but this time the reaction is:. The magnesium chloride is removed from the titanium by distillation under very low pressure at a high temperature. Jim Clark Chemguide. Uses of titanium Titanium is a highly corrosion-resistant metal with great tensile strength.
Titanium is used, for example: in the aerospace industry - for example in aircraft engines and air frames; for replacement hip joints; for pipes, etc, in the nuclear, oil and chemical industries where corrosion is likely to occur. Titanium Extraction Titanium cannot be extracted by reducing the ore using carbon as a cheap reducing agent, like with iron.
Melting Titanium sponge is melted under argon to produce ingots. SnI 4 TiI 4 violet-black hcp I- but essentially monomeric cf. SnI 4. Preparations They can all be prepared by direct reaction of Ti with halogen gas X 2.
Diamond 2. Workable deposits are found all over the planet, and yet it remains more expensive than any of those other metals. Extracting the Titanium Most titanium mining is done by open pit, meaning that the soil is taken from the ground and sent to factories where the ore can be removed.
This process is usually done with a suction bucket wheel on a floating dredge. Mineral-rich sand is sent through its screens, called trammels, which starts filtering out the unwanted or unnecessary elements. The separation is usually gravity powered, and the waste can be removed with a wet spiral concentrator.
At this point, the separated material can be sent through some electrostatic, magnetic, and other gravity-fed equipment to further refine the materials into something useful.
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