Process for the recovery of titanium dioxide and value metals and system for same

Abstract

A process and system for recovering titanium dioxide and other value metals from a titanium bearing solid is disclosed. The process includes leaching the solid in hydrochloric acid to produce a leachate comprising undissolved solids and a leach solution comprising the titanium dioxide and the value metals, wherein the hydrochloric acid concentration is maintained above a value required to maintain the titanium dioxide and the value metals dissolved in the leach solution at atmospheric pressure. The leachate is separated into the leach solution and the undissolved solids. The concentration of hydrochloric acid concentration in the leach solution is reduced to recover titanium dioxide by hydrolysis and precipitation to produce a titanium dioxide rich slurry. In a preferred embodiment, HCl is recovered with a matrix solution.

What is claimed is: 
     
         1 . A process for recovery of titanium dioxide and value metals from a titanium bearing solid, the process comprising the steps of:
 (a) leaching the solid in hydrochloric acid to produce a leachate comprising undissolved solids and a leach solution comprising the titanium dioxide and the value metals, wherein the hydrochloric acid concentration is maintained above a value required to maintain the titanium dioxide and the value metals dissolved in the leach solution at atmospheric pressure;   (b) separating the leachate into the leach solution and the undissolved solids; and   (c) reducing the concentration of hydrochloric acid concentration in the leach solution to recover titanium dioxide by hydrolysis and precipitation to produce a titanium dioxide rich slurry.   
     
     
         2 . The process of  claim 1 , wherein reducing the hydrochloric acid concentration is by heating the leach solution and removing free HCl by HCl distillation of the leach solution. 
     
     
         3 . The process of  claim 1 , wherein reducing the hydrochloric acid concentration is by adding water to the leach solution. 
     
     
         4 . The process of  claim 1  wherein pigment grade TiO 2  is recovered directly from solutions containing ferric iron. 
     
     
         5 . The process of  claim 1 , wherein the titanium dioxide slurry is separated in a solid/liquid separator and the TiO2 free filtrate produced in the separator is further treated to recover vanadium. 
     
     
         6 . The process of  claim 5 , wherein the further treatment of the TiO 2  free filtrate is by solvent extraction with an extractant and the further treatment produces a vanadium free raffinate. 
     
     
         7 . The process of  claim 6 , wherein the extractant is D2EHPA (di-2-ethyl hexyl phosphoric acid) or LIX63. 
     
     
         8 . The process of  claim 6 , wherein the extractant is LIX63. 
     
     
         9 . The process of  claim 6 , further comprising mixing the raffinate with a matrix solution to produce a reaction mixture and adding an oxygen containing gas to the oxygenate the mixture with HCl production. 
     
     
         10 . The process of  claim 7 , wherein the matrix solution comprises ZnCl 2 . 
     
     
         11 . A system for recovering titanium dioxide comprising:
 a) a leaching section comprising
 a vessel having an ore inlet for a titanium dioxide bearing solid, and an acid inlet for hydrochloric acid, 
 an agitator mixing the titanium dioxide bearing solid and the acid to produce a leachate comprising
 a leach solution and undissolved solids; and 
 
 a leachate outlet for discharging the leachate; 
   b) a solid liquid separator comprising
 a leachate inlet hydraulically connected to the leachate outlet, 
 a separation device hydraulically connected to the leachate inlet, for separating the leach solution from the undissolved solids, the device comprising an undissolved solids discharge and a leach solution outlet; and 
   c) a titanium dioxide precipitator for reducing the concentration of the acid in the leach solution and recovering titanium dioxide by precipitation from the leach solution, the precipitator comprising
 a leach solution inlet hydraulically connected to the leach solution outlet, 
 an HCl acid outlet, and 
 titanium dioxide slurry outlet. 
   
     
     
         12 . The system according to  claim 11 , wherein the titanium dioxide precipitator comprises a heater for boiling the leach solution to liberate free HCl via the HCl acid outlet and a means of collecting and discharging the precipitated a titanium dioxide slurry. 
     
     
         13 . The system of  claim 11 , further comprising an acid condenser hydraulically connected to the HCl acid outlet condensing the free HCl. 
     
     
         14 . The system of  claim 11 , further comprising means of recycling the condensed free HCl to the leaching solution. 
     
     
         15 . The system of  claim 11 , further comprising a solvent extraction system for extractant LIX63 hydraulically linked to the leach solution outlet, the solvent extraction system comprising a raffinate outlet. 
     
     
         16 . The system of  claim 15 , wherein the raffinate outlet is hydraulically linked to a HCl recovery system comprising a circulating matrix solution and an injection inlet for an oxygen containing gas. 
     
     
         17 . The system of  claim 16 , wherein the HCl recovery system comprising a reactor for recovering hydrochloric acid and for oxidation/hydrolysis of metal from metal chloride solution, the reactor comprising:
 a tank compatible with a mixture comprising the metal chloride solution, a matrix solution, an oxygen containing gas and a solid comprising a metal oxide, the tank comprising   a base,   the base defining a first diameter and a first cross sectional area, the base comprising a metal oxide slurry outlet, a matrix solution outlet and a gas inlet;   a top opposite the base,   the top comprising a solution inlet, a hydrochloric acid outlet, a matrix solution inlet, the top defining gas an expansion zone having a second cross sectional area and,   a wall attached to the top and the base defining a volume and a height of the tank;   wherein a ratio of the second cross sectional area to the first cross sectional area is greater than 1 and whereby the hydrochloric acid leaves the mixture as a hydrochloric acid containing gas in the gas expansion zone at the top of the tank.   
     
     
         18 . The system of  claim 16 , wherein the reactor comprises an aspect ratio of the height to the first diameter from 5 to 1-20 to 1. 
     
     
         19 . The system of  claim 16 , wherein the circulating matrix solution comprises ZnCl 2 .