Manufacture of titanium dioxide

Claim 1

A CONTINUOUS PROCESS FOR THE MANUFACTURE OF TITANIUM DIOXIDE FROM AT LEAST ONE TITANIUM-CONTAINING SUBSTANCE SSELECTED FROM THE GROUP CONSISTING OF MINERAL RUTILE, LEUCOXENE AND A CONCENTRATE PREPARED BY REACTING A TITANIUM DIOXIDE-CONTAINING MATERIAL WITH A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYDROCHLORIC ACID AND HYDROGEN CHLORIDE GAS, WHICH COMPRISES PERFORMING THE FOLLOWING PROCESS STEPS: (A) INCORPORATING AT LEAST ONE METAL OXIDE SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM OXIDE, CALCIUM OXIDE AND ZINC OXIDE WITH THE TITANIUM-CONTAINING SUBSTANCE IN A QUNTITY SUCH THAT THE MOLAR RATIO OF THE METAL OXIDE TO THE TITANIUM DIOXIDE CONTENT OF THE TITANIUM-CONTAINING SUBSTANCE IS AT LEAST 2:1, (B) CALCINATING THE MIXTURE OF METAL OXIDE AND TITANIUMCONTAINING SUBSTANCE AT A TEMPERATURE WITHIN THE RANGE OF FROM 900*C. TO 1,300*C. TO FORM AT LEASST ONE METAL TITANATE, (C) DISSOLVING THE TITANATE IN HYDROCHLORIC ACID TO FORM A SOLUTION, (C) DISSOLVING THE METAL TITANATE IN HYDROCHLORIC ACID TO FORM A SOLUTION, (D) HEATING TO PRECIPITATE TITANIUM DIOXIDE, (E) NEUTRALISING THE REMAINING SOLUTION BY INCORPORATING THEREWITH AT LEAST ONE METAL OXIDE CORRESPONDING TO THE METAL TITANATE FORMED IN PROCESS STEP (B), (G) THERMALLY DECOMPOSING THE NEUTRALISED SOLUTION AT A TEMPERATURE WITHIN THE RANGE OF FROM 200*C. TO 900*C. TO GIVE STEAM, HYDROGEN CHLORIDE AND THE SAID METAL OXIDE, (H) RECYCLING AT LEAST THE GREATER PART OF THE HYDROGEN CHLORIDE FOROMED TO PROCESS STEP (C).