TITANIUM DIOXIDE

THE PRINCIPLES OF TITANIUM DIOXIDE MANUFACTURE

The raw material used for the manufacture of titanium dioxide when adopting “the sulphate process” is mineral ilmenite. Chemically, it is a mixture of oxides, predominantly those of titanium and iron. Manufacturing technology for titanium dioxide based upon the digestion of mineral ilmenite with sulphuric acid is commonly refered to as “Sulphate Technology”. The ilmenite is milled, dried and then digested with concentrated sulphuric acid, then following ageing and cooling, the digestion mass is dissolved with water. The resultant liquor is then reduced, insoluble particles are separated by clarification, and the liquor is cooled leading to the separation of iron in the form of crystalline copperas, (which is subsequently separated by centrifuges). This is followed by an hydrolisation procedure, during which amorphous flakes of titanium dioxide are liberated, - although they do not possess the desired physical properties. Consequently the resultant slurry is washed and bleached in two stages and, following the addition of other necessary chemicals and concentrating, is ignited at a temperature above 800 °C in a calciner, where particles of applicable pigment are formed in two basic grades, - anatase and rutile. The calcinate is milled in order to gain material which can be directly used, although the majority of production passes through so called ‘surface treatment’, where in a water suspension additional chemicals which improve physical properties, (above all weather resistance and dispersibility), are bound to the surface of the titanium dioxide particles.

The titanium dioxide manufacturing plant was commisioned in 1968, with a production capacity of 22,000 tonnes per year. Between 1981-1984, extensive reconstruction was implimented during regular production activites which resulted in an increased annual capacity of 25,000 tonnes. Further intensification, lifting production capacity up to 35,000 tonnes per year, occured between 1998-2000 and currently in progress are plans to expand further to 54,000 tonnes. During 2009, 45,167 tonnes of titanium dioxide were produced which historically is the highest ever production output.