Patent ID: 7618601
Filing Date: 2009-11-17
Classification: C01G,C22B

Abstract:
1. A process for enrichment of anatase mechanical concentrates in order to obtain synthetic rutile with low contents of rare earth and radioactive elements, comprising the following sequence of unit operations: calcination of the anatase concentrate in a fluidized bed or rotary kiln, at a temperature between 400° C. and 600° C., during a period of time from 15 to 60 minutes, wherein hydrated iron oxides are converted into hematite after hydration water is removed, providing a reduction in the time required for the next step; reduction of the calcined product, in a fluidized bed or rotary kiln, at a temperature between 400° C. and 600° C., during a period of time from 5 to 30 minutes, using as reducing agent hydrogen, natural gas or any carbon based reductant, the result of which is the transformation of hematite into magnetite; dry or wet low-intensity magnetic separation of the reduced product, in magnetic separators provided with permanent magnet and drum, the field intensity ranging from 600 to 800 Gauss, in which the magnetic fraction generated in the reduction step is discarded; dry, high-intensity, high-gradient magnetic separation of the non-magnetic fraction from the low-intensity separation, in drum or roll separators with rare-earth permanent magnet, magnetic field ranging from 10000 to 15000 Gauss, extracting silicates, secondary phosphates, monazite, calzirtite, zircolinite and uranium and thorium containing minerals; leaching of the high-intensity magnetic fraction in agitated tanks or fluidized bed columns, with a solution of 20-25% w/w HCl, at a solid-liquid ratio of 1:2 w/w, at a temperature between 90° C. and 107° C., and for a leaching residence time from 2 (two) to 4 (four) hours, promoting solubilization of impurities rich in iron, aluminium, phosphates, magnesium, barium, calcium, strontium, rare earths, uranium and thorium; filtering of the leached product in a belt filter; drying the filtered product in a rotary or fluidized bed drier; oxidation of the dried product in a rotary kiln or fluidized bed reactor, at a temperature range from 900° C. and 1200° C., in the presence of a mixture of the following substances: alkali metal sulphates, alkali metal carbonates, phosphoric acid (H leaching of the quenched product in agitated tanks or columns, in such a way that said leaching can be carried out using either 25.0% w/w hydrochloric acid (HCl), at a solid-liquid ratio of 1:2 w/w, at a temperature range from 90° C. and 107° C., for 2 (two) to 4 (four) hours, or 55.0% w/w sulphuric acid (H filtering of the product from the second leaching in a belt filter; drying of the filtered product in a rotary or fluidized bed drier; and dry, high-intensity, high-gradient magnetic separation of the product of the second leaching in drum or roll separators with rare-earth permanent magnet (10000 to 15000 Gauss), discarding the magnetic fraction and recovering the non-magnetic fraction as the end product (P), that is, the synthetic rutile of interest.