A smaller, but high value and strong expectations for growing applications of titanium dioxide is titanium metal production. With its physical and chemical properties Titanium metal represent a material for new technological and environmental innovative applications. It’s the best corrosion resistant metal, it has double strength of steel and has less weight. Areas of usage are aerospace, defence, automobil, construction, offshore, healthcare, chemical industry, power and sporting goods.
Titanium dioxide does not occur in nature in its pure form, but is derived from ilmenite or leuxocene ores containing 45 – 65 % TiO2. In addition it can be mined from natural rutile reserves with commercial typical content of 94 – 96 % TiO2. So far the rutile production has been made on rutile beach sand. Hard rock deposits, including Engebø, are also candidates for the supply chain of the titanium industry. The global rutile production in 2005 was 360,000 tons. By way of comparison, the global production of ilmenite in 2005 was 4.8 million tons.
Ilmenite is the most widespread titanium mineral. The vast majority of the world’s resources are found in coastal areas of Australia, South Africa, India, Brazil, Madagascar, and USA. The mineral is also found in hard rock deposits in Norway and Canada. The table below shows Ilmenite mine production 2006-2007 ('000 tons).
Tabell - Ilmenite (oppdatert 2007)
In contrast to ilmenite the vast majority of the world resources of rutile are more restricted with production concentrated in USA, Australia, and South Africa. The table below shows Rutile mine production 2006-2007 ('000 tons).
Tabell - Rutile (oppdatert 2007)
Usually ilmenite and rutile are mined together from sand gains. For many sand deposits operations, by-product minerals such as monazite and zircon play a significant role economically when it comes to developing a deposit.
Suction dredging is used where possible, although wet mining is also used to mine ore reserves located below the water table. Upon wet mining dredging material is then transferred to a wet plant from where it is screened and then concentrated using spiral.
In ilmenite hard rock deposits the ore has to be mined and crushed, and the ilmenite has to be separated out. The separation process is expensive which implies that ore grade requirements should be high.
Some deposits are mined mainly for their zircon and rutile contents, notably deposits at the east coast of Australia. In these cases ilmenite is separated from the other minerals at the concentration stage using wet high intensity magnetic separation. The ilmenite may then be returned to the tailings, stockpiled at the mine site or sold for low value applications such as sandblasting.
Because of the limited resources of naturally occurring rutile, the mining industry has developed two beneficial products that are used as substitutes for natural rutile: synthetic rutile and titanium slag. Both products are produced by upgrading ilmenite by removing iron oxide and other impurities. The titanium feedstocks are upgraded through two main processing routes, the sulphate and the chloride processes. The first uses sulphuric acid as extraction agent, the second uses chloride. One factor that has led to the increase in capacity to upgrade ilmenite into beneficiated slag or synthetic rutile is the trend in the TiO2 pigment industry towards greater chloride route capacity, which requires higher quality feedstock.
In TiO2 production, the chloride process is favoured for two main reasons; firstly, TiCl4, the intermediate product, is easily purified and oxidiced to a superior pigment and chlorine; secondly, it is easier to produce exact TiO2 particle distributions. In this process higher quality feedstock is required to minimize chlorine consumption and to prevent operational difficulties, which generally is not tolerant of high impurity levels.
In the sulphate route, the production of TiO2 pigment, ilmenite and Ti slag are directly reacted with sulphuric acid to produce titanium sulphate and iron sulphate. The titanium sulphate is subject to selective thermal hydrolysis to produce hydrated TiO2. This is further washed and calcined to produce titanium pigments.
Comparing the two routes and considering the trend to move to the chloride processes, one factor is lower associated costs. But industry experts also emphasise that the chloride route TiO2 pigment has better properties for the premium grade coatings. These properties are color brightness, covering ability, durability and gloss. This is the major factor behind the decline in sulphate pigment use and the trend away from the consumption of sulphate grade ores. These are mostly low-grade primary ilmenites and slags made from high alkali/high iron content ilmenites.
The chlorination reactors for rutile, synthetic rutile, slag and ilmenite are similar, but the higher volume of chlorine required for ilmenite reduces capacity. For high grade ores the process is more efficient and simple. Du Pont, the world leader in the pigment industry, uses blends of the various raw materials and decides the blend based on price of raw materials including ore, coke, chlorine and waste processing.
Requirement for secondary ilmenite among pigment producers for both synthetic rutile as well as chlorination grade ilmenite has led to increasingly strong demand for the minerals. Escalating costs of chloride and waste processing have also been drivers for producers to use higher-grade ores. Producers have responded by expanding slag capacity to maximize profits from valuable iron co-product and use of higher-grade content ilmenite.
If you want to read more about Ilmenite and Tiatium follow the links below
If you want to read more about Ilmenite and Titanium follow the links below;
|
Ilmenite and Titanium |