Process for the preparation of titanium dioxide by digestion of a titanium-containing starting material and ilmenite

摘要

For the preparation of titanium dioxide by the sulphate process, titanium slag and ilmenite are used as starting materials and are digested simultaneously but separately, i.e. different amounts of 98.5% strength and 85% strength sulphuric acid are added to them, the temperatures being slightly below the starting temperatures and the digestion reactions being initiated by adding a small amount of superheated steam. After the digestion, the two mother liquors are mixed and are processed together to give TiO2, the 23% strength dilute sulphuric acid obtained in the process being concentrated to about 85% with isolation of metal salts and being recycled. Highly concentrated sulphuric acid, preferably obtained by roasting the metal sulphates obtained in the process, is predominantly used for the titanium slag digestion, while the excess concentrated 85% strength sulphuric acid is used predominantly for the ilmenite digestion, so that the dilute sulphuric acid obtained can be virtually completely reused in an economical manner.