Ilmenite separation processes

Titanium slag and synthetic mtile are also used as raw materials in the production of titanium whites. Titanium slag results from a metaHurgical process during which iron (qv) is removed from ilmenite by reduction with coke in an electric arc furnace at 1200—1600°C. Under these conditions, iron oxide is reduced to metal, melts, and separates from the formed titanium slag. Titanium slag contains 70—75% Ti02 and only 5—8% iron. 

A number of high temperature processes for the production of titanium carbide from ores have been reported (28,29). The aim is to manufacture a titanium carbide that can subsequently be chlorinated to yield titanium tetrachloride. In one process, a titanium-bearing ore is mixed with an alkah-metal chloride and carbonaceous material and heated to 2000°C to yield, ultimately, a highly pure TiC (28). Production of titanium carbide from ores, eg, ilmenite [12168-52-4], EeTiO, and perovskite [12194-71 -7], CaTiO, has been described (30). A mixture of perovskite and carbon was heated in an arc furnace at ca 2100°C, ground, and then leached with water to decompose the calcium carbide to acetjdene. The TiC was then separated from the aqueous slurry by elutriation. Approximately 72% of the titanium was recovered as the purified product. In the case of ilmenite, it was necessary to reduce the ilmenite carbothermaHy in the presence of lime at ca 1260°C. Molten iron was separated and the remaining CaTiO was then processed as perovskite. 

Both processes also use up-graded ilmenite (slags). About 30% of the world s titanium feedstocks are suppHed by titanium slag producers in Canada, South Africa, and Norway. Slags are formed by the high temperature reduction of ilmenites in electric furnaces. Much of the iron oxide content is reduced to metallic iron and separated as a saleable by-product. Magnesium and other impurities may also be incorporated in the following equations. 

The resultant slag, a complex mixture of titanates, may contain 70—85% Ti02- The slag route is particularly useful when ilmenite is closely associated with haematite, from which it cannot economically be separated mechanically. Because the iron content of the slag is low, its use reduces the quantity of iron sulfate in the Hquid effluent of sulfate process plants. Slag used as a feedstock for TiCl production must be low in magnesium and calcium. A variety of other ilmenite beneficiation or synthetic mtile processes have been pursued, primarily to provide alternative chloride process feedstocks. Low grade ilmenite... 

However, separation between resistance levels of 1000 to 300 kH may be marginal. A typical application of conductivity sorting is the separation of massive ilmenite from anorthosite. Both are compact rocks, but ilmenite is a good electrical conductor, whereas anorthosite is an insulator. The dimensions and operating information for the Sor-tex CS-03 conductivity sorter, which is capable of processing up to about 25,000 kg/h (27.5 tons/h) of 0.05-to 0.15-in mesh size (2 to 6 in), are given in Table 19-4. 

Sulphate process. The ilmenite is reacted with sulphuric acid giving titanium sulphate and ferric oxide. After separation of ferric oxide, addition of alkali allows precipitation of hydrous titanium dioxide. The washed precipitate is calcined in a rotary kiln to render titanium dioxide. The nucleation and calcination conditions determine the crystalline structure of titanium dioxide (e.g. rutile or anatase). 

The electrostatic separation method is the exclusive choice in some specific situations, for example in the cases of rutile and ilmenite deposits. These deposits generally contain minerals of similar specific gravities and similar surface properties so that processes such as flotation are unsuitable for concentration. The major application of electrostatic separation is in the processing of beach sands and alluvial deposits containing titanium minerals. Almost all the beach sand plants in the world use electrostatic separation to separate rutile and ilmenite from zircon and monazite. In this context the flowsheet given later (see Figure 2.35 A) may be referred to. Electrostatic separation is also used with regard to a number of other minerals. Some reported commercial separations include those of cassiterite from scheelite, wolframite from quartz, cassiterite from columbite, feldspar from quartz and mica, and diamond from heavy associated minerals. Electrostatic separation is also used in industrial waste recovery. 

The ilmenite production from heavy mineral sands exclusively utilizes a physical separation method using magnetic separation, gravity concentration and electrostatic separation. Flotation is practiced mainly for beneficiation of fine mineral sands containing rutile, ilmenite and zircon. The ilmenite that is produced in a number of operations in Western Australia, India and the USA is high in chromium, which makes the ilmenite unusable. This section discusses a new process that was developed for chromium removal from ilmenite concentrates. 

The fine -250-mesh product was preconcentrated using gravity (tabling) followed by zircon flotation and magnetic separation to produce rutile and ilmenite concentrate. The process flowsheet with points of reagent additions is presented in Figure 25.14. Using... 

Several large deposits of fine mineral sands containing mtile, ilmenite and zircon exist in Australia (Wimmera mine) and in the Soviet Union. The mtile, ilmenite and zircon cannot be preconcentrated. In most cases, flotation was used which involved bulk flotation followed by titanium-zircon separation. Over the years, several effective processes have been developed for bulk flotation followed by titanium-zirconium separation. The type of... 

There are now two processes in widespread use for making titanium dioxide pigments. In the sulphate process, finely ground ilmenite is digested in sulphuric acid and the iron is reduced and separated as iron(II) sulphate. The titanium(IV) sulphate is hydrolysed by steam to a hydrous oxide, which is thoroughly washed to remove soluble impurities and finally calcined at a temperature of about 1000 °C to give the anatase form of titanium dioxide. 

The crude monazite sands are first concentrated by the general mechanical and physical treatments of mineral dressing. Brazilian monazite sands are processed mainly by the electromagnetic separation technique. The Indian monazite industry is essentially based on the recovery of rutile and ilmenite. Ilmenite has a magnetic susceptibility very close to that of monazite and thus direct electromagnetic separation cannot be applied to the Indian Travancore monazite sands. 

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