Influence of Temperature on Reaction Mechanism of Ilmenite Ore Smelting for Titanium Production
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INTRODUCTION
TITANIUM has good physical and chemical properties, such as excellent strength, corrosion resistance, fatigue resistance, fracture toughness, and high-temperature characteristics. Therefore, it is expected that there will be steady demand for titanium in the fields of desalination, power generation, etc. To obtain high yields of titanium, relatively high-concentration TiO2, such as rutile (~ 95 mass pct), should be used as a raw material. However, rutile is a limited resource in nature. Alternatively, ilmenite is regarded as a promising resource. According to a U.S. geological survey,[1] there are 62 million tons of rutile reserves in the world and 870 million ton of ilmenite reserves. Therefore, ilmenite ore, which is more than ten times as abundant as rutile, has become an important source for producing titanium. DONG HYEON KIM, TAE SUNG KIM, and JOO HYUN PARK are with the Department of Materials Engineering, Hanyang University, Ansan 15588, Korea. Contact e-mail: [email protected] JUNG HO HEO is with the Hanyang University, Seoul, Korea and also with the Research & Development Center, LS-Nikko Copper, Ulsan 44997, Korea. HYUN SIK PARK is with the Resources Recovery Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon 34132, Korea. Manuscript submitted December 16, 2018. Article published online May 17, 2019. 1830—VOLUME 50B, AUGUST 2019
Because ilmenite has a lower-purity TiO2 (30 to 65 mass pct) compared to rutile, it must be upgraded to obtain TiO2-rich slag. Many of the previously developed processes use hydrometallurgical processing to increase the purity.[2,3] One of the well-known processes is the Benilite process.[2] This is a process of partial reduction of ilmenite using a rotary kiln, followed by leaching with hydrochloric acid and separating the TiO2. Another process is the Becher process.[3] Like the Benilite process, the Becher process leaches out TiO2 after reduction to obtain synthetic rutile; however, there are significant differences between these processes, including a higher processing temperature. Reduced ilmenite is collected in a 1 pct NH4Cl solution and blown with air to oxidize the iron in ilmenite into a slime. This process is widely used because it has low operating costs. However, it has the disadvantage of taking 14 to 16 hours to oxidize metallic iron into iron oxide. Despite the development of these aforementioned processes, it is not easy to selectively remove iron and other impurities from ilmenite, which has lower-purity TiO2. Also, these processes of making synthetic rutile can lead to environmental problems, such as the production of large amounts of acid waste. Therefore, alternative processes have been developed. One such alternative process is pyrometallurgical ilmenite smelting. Compared to hydrometallurgical processing, the
METALLURGICAL AND MATERIALS TRANSACTIONS B
Table I. Ti 32.6
Chemical Composition of Ilmenite Ore (Mass Percent) Fe
Si
Al
Mn
Mg
O
28.7
1.9
1.3
1.1
0.4
33.9
Fig. 1—XRD pattern of raw ilmeni
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