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|The Prospects of Titanium Sponge Production in India||Dr. R.N. Patra, CMD, Indian Rare Earths Limited|
Ilmenite, leucoxene and rutile are commercially important source of titanium metal. The contents of titanium dioxide (TiO2) vary from 35% to 65% in ilmenite. Iron oxide both in ferrous and ferric forms constitutes the residual major portion of this ore. Silica, alumina, and oxides of vanadium, chromium, calcium, magnesium and sometimes radioactive elements such as thorium and uranium comprise of the minor impurities in ilmenite. Leucoxene has about 75 to 92% TiO2 while Rutile contains between 92% to 95% TiO2. Ilmenite having the least content of titanium dioxide is most abundantly available and rutile having the highest titanium content is least abundant in nature. Global production of ilmenite is reported to be 120 million ton compared to only 0.6 million ton of rutile and 0.11 million ton of leucoxene in the year 2010. Hence bulk of the ilmenite is converted to titanium slag, synthetic rutile, or upgraded slag containing 75% to 96% TiO2 by adopting various pyro metallurgical and hydrometallurgical processes to compensate for the supply and demand gap of rutile, which is the most preferred feed stock for production of titanium metal. About 94% of the world titanium feed stock is used for production of titanium dioxide pigment whereas less than 3% is only used for production of titanium metal. The remaining 2 to 3% of titanium feed stock is consumed by welding electrode manufacturing industry and for miscellaneous industrial chemicals applications.
Usage Titanium Metal
Titanium possesses the highest strength to weight ratio and the low corrosion rate and is primarily consumed for making building structures, bodies of transport vehicles, chemical process equipment, storage tanks, etc. Further, they also have strategic applications in ballistic missiles and aerospace industries. Titanium metal is also used in consumer goods, spectacle frames, watches, jewelry, cookware, building and constructions, food industry, desalination plant, power generation units, offshore marine applications, flue gas desulphurization scrubbers and recreation items, such as bicycle, golf stick etc.
Titanium Production Processes and Plants - World Status
Titanium bearing feed stocks such as chlorinatable titanium slag, synthetic rutile and upgraded slag which contain preferably higher than 85% TiO2 are chlorinated at around 8000 C by using chlorine gas in the presence of calcined petroleum coke to produce titanium tetrachloride which is liquid at room temperature. In Japan and USA production of titanium tetrachloride is carried out using a fluidized bed reactor, whereas in Russia, Ukraine, Kazakhstan and China, molten salt chlorinators are used for above purpose.
Titanium sponge production by Hunter Process uses sodium to reduce titanium tetrachloride. This process yields titanium metal of higher purity containing lower quantities of iron compared to those produced by Kroll Process and the material was ductile when hot and brittle when cold.
Titanium sponge is produced by reducing titanium tetrachloride with magnesium metal at 9000C. Titanium sponge production by magnesium reduction of titanium tetrachloride found commercial acceptance.
High Pure Titanium Metal
Von Arkel developed a process to produce titanium in a relatively pure form by thermal decomposition of titanium Iodide (TiI4) at 13000C under low pressure. Iodine liberated is diffused back into impure titanium for further conversion into titanium Iodide. This process is used to produce very high pure titanium crystal bar for electronics industry.
Current global production of titanium metal powder is estimated to be not more than 10000 ton per annum and no reliable data is available for its production. Most production of titanium powder takes place in Russia, Ukraine, China and Japan.
Indian Efforts on Developing Production Technology for Titanium
Based on experience of pilot plant operation at Nuclear Fuel Complex (NFC), a Technology Development Center for titanium sponge was established at Defense Metallurgical Research Laboratory, Hyderabad (DMRL) in 1984 for developing Kroll Process to a level of commercial viability. This technology has been adopted in the 500 tpa titanium sponge manufacturing facility set up in KMML. India became the 7th country to produce titanium sponge. The technology so far developed needs further refinement before considering its adoption on commercial scale.
As far as production of titanium powder is concerned, NFC had developed a process consisting of hydriding of titanium scrap to brittle hydride, its grinding to powder form and final dehydrogenation at higher temperature to yield titanium powder. National Aeronautical Laboratory, Bangalore has also developed technology to produce titanium powder from molten titanium metal.
Mishra Dhatu Nigam Limited, Hyderabad (MIDHANI) is the only company in India having large scale facilities for melting of titanium sponge which is so far being imported. MIDHANI caters to the need of Hindustan Aeronautic Limited (HAL) who are engaged in production of aircrafts, helicopters for the defense organizations.
Challenges for Titanium Production in India
High cost of production of titanium metal coupled with the technical difficulties associated with its production which involves multiple stages of processing involving handling of corrosive process inputs at high temperature and adoption of complex technically challenging procedures to handle the metal at high temperature in completely inert atmosphere have been barrier for its large scale industrial production. The production of titanium metal is dominated by a handful of players.
Global production of titanium sponge is about 60% of its installed capacity. Economy of titanium metal production largely depends on availability of chlorine and magnesium metal of high purity at competitive price in addition to adoption of the state of the art titanium sponge production technology.
Availability of downstream fabrication facility and the technology for the same to produce titanium ingots and metal sheets form the titanium sponge considerably impact the growth of titanium sponge producing industry. Both the titanium sponge production and titanium metal processing industry complement each other for their economic viability.
Availability of chlorine in India is not a problem as chlor-alkali industry producing caustic soda and chlorine by electrolysis of brine is well established.
There is at present no magnesium manufacturing unit in India and magnesium metal for production of titanium sponge is imported from overseas.
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