Chloridization beneficiation of ilmenite
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I.
INTRODUCTION
ILMENITE, the major source material of titanium, occurs on the earth's surface in the form of beach sands and rock deposits. The world reserves of ilmenite are estimated at 1300 million t o n n e s - - 10 pct of which are estimated to occur in India. The bulk of ilmenite currently produced is used in the production of TiO2 pigment by the sulfate route. The mineral, unlike rutile, is not desirable for direct conversion to titanium tetrachloride which is an intermediate in the production of titanium metal or pigment oxide. However, considering the limited reserves of rutile (30 MT in the w o r l d - - 7 MT in India) and its growing demand for the production of the chloride, extensive investigations at various centers have been carried out to beneficiate ilmenite and obtain a substitute for futile. A number of processes 1 such as (1) high temperature/ pressure leaching with hydrochloric acid, 2 (2)oxidation/ reduction roasting followed by acid leaching, 3 (3) oxidation/reduction roasting followed by rusting and desliming, 4 (4) reduction-roasting followed by FeC13 solution leaching,5 (5) reduction-roasting followed by carbonylation, 6 (6) chlorination with hydrochloric acid gas, 7 (7) chlorination with chlorine in the presence of carbon, 8 (8) chloridization treatment with titanium tetrachloride, 9 etc. have been investigated. Reductive smelting and slagging off the titania values and subsequent aqueous processing have also been carried out to produce synthetic rutile. 10 Synthetic rutile obtained by these methods has received general acceptance as feed to chlorinators. Chloridization process is based on the chloride and oxide forming potentials of metals. The term chloride forming affinity of a metal oxide, as measured by the difference between the free energy of its chloride and its oxide at any temperature, is used in selecting a suitable chloridizing agent. H Table I shows the metals arranged in the order of their chloride forming affinity. It shows that at 1573 K copper has more affinity compared to titanium to form chloride from its oxide. It can also be inferred that the titanium tetrachloride will react with oxides of Fe-Cu to form their respective chlorides while itself being converted to titanium dioxide. Figure 1 shows the plot of calculated values of free energy changes for the reactions between TIC14 and other K. SWAMINATHAN and CH. SRIDHAR RAO are Scientific Officers, Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Bombay400 085, India. Present address of the latter is Project Manager, Titanium Project, Defence Metallurgical Research Laboratory, PO: Kanchanbagh, Hyderabad-500 258, India. Manuscript submitted August 17, 1982. METALLURGICALTRANSACTIONSB
Table I.
Order of Some Common Metals
Conventional Chloride Forming Electrochemical Affinity from Oxide Series (Highest (Highest at Top) at Bottom) at 1573 K at 1073 K Cu Cu Pb Pb Pb Cu Sn Zn Zn Ni Co Co Co Ni Sn Fe Sn Ni S Fe Fe V Ti Ti Ti Ge Ge A1 A1 A1 Si Si V O P V S P
Boiling Point of Chlorides, K CuCI PbC12 ZnC12 COC1
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