Synthetic rutile process a

Abstract

A process for recovering titanium as synthetic rutile from an ilmenite unsuited to the standard Becher process by treating the ilmenite in a reducing atmosphere in the presence of a carbonaceous reductant to yield reduced ilmenite in which iron oxides in the ilmenite have been reduced to metallic iron, and separating the metallic iron to obtain a synthetic rutile product. The ilmenite is treated at an elevated temperature lower than that for which the TiO 2 content of the synthetic rutile product is highest but at which there is substantially no reoxidation of metallic iron. The carbonaceous reductant comprises coal selected for a gasification reactivity that increases the rate of reduction of iron oxides and titanium species that at least partly offsets the lowered TiO 2 content of synthetic rutile product resulting from the lower elevated temperature, and achieves a TiO 2 content of ≧90% in the synthetic rutile product.

1 . A process for recovering titanium as synthetic rutile from an ilmenite unsuited to the standard Becher process, including the steps of treating the ilmenite unsuited to the standard Becher process in a reducing atmosphere in the presence of a carbonaceous reductant whereby to convert the ilmenite to reduced ilmenite in which iron oxides in the ilmenite have been reduced to metallic iron, and separating out the metallic iron so as to obtain a synthetic rutile product,
 wherein said treatment of the ilmenite is at an elevated temperature lower than that for which the TiO 2  content of the synthetic ruffle product is highest but at which there is substantially no reoxidation of the metallic iron,   and wherein the carbonaceous reductant comprises coal selected for a gasification reactivity that results in an increased rate of reduction of iron oxides and titanium species effective to at least partly offset the lowered TiO 2  content of the synthetic rutile product resulting from said lower elevated temperature, and to achieve a TiO 2  content of 90% or greater in said synthetic rutile product.   
     
     
         2 . A process according to  claim 1  wherein the elevated temperature of said treatment is less than 1050° C. 
     
     
         3 . A process according to  claim 2  wherein the gasification reactivity is sufficiently high to achieve said offset. 
     
     
         4 . A process according to  claim 3  wherein said gasification reactivity of the coal is relatively high (as defined herein). 
     
     
         5 . A process according to  claim 1  wherein the selected coal has impurity levels of one or more ion-exchanged inorganic elements sufficiently high to increase the gasification rate of the coal thus improving the reducing conditions in the process and thereby increasing said rate of reduction of iron oxides and titanium species. 
     
     
         6 . A process according to  claim 5  wherein the acid extractable portion of said one or more ion-exchanged inorganic elements is at least 50%. 
     
     
         7 . A process according to  claim 1  wherein the selected coal has relatively high impurity levels of ion-exchanged calcium. 
     
     
         8 . A process according to  claim 1  wherein the selected coal is a sub-bituminous or lignite coal. 
     
     
         9 . A process according to  claim 8  wherein the selected coal has a total moisture content between 5 and 40%, volatiles content greater than 30%, and ash content below 10%. 
     
     
         10 . A process according to  claim 8  wherein inherent moisture content of the selected coal is 20% or less, volatiles content is >40% and ash content is <5%. 
     
     
         11 . A process according to  claim 1  further including mixing char with the ilmenite before it is delivered for said treatment step. 
     
     
         12 . A process according to  claim 1  wherein the sulphur content of the coal is less than 1% w/w, and there is no added sulphur present for most of the duration of said treatment. 
     
     
         13 . A process according to  claim 12 , wherein the sulphur content of the coal is less than 0.5%. 
     
     
         14 . A process according to  claim 12 , wherein the sulphur content of the coal is less than 0.2%. 
     
     
         15 . A process according to  claim 12  further including delivering sulphur to the ilmenite during said treatment step for removing manganese impurity as manganese sulphide, such delivery being effected only later during the duration of the reduction treatment. 
     
     
         16 . A process according to  claim 1  wherein the iron content of the ilmenite, expressed as FeO, is greater than 12%. 
     
     
         17 . A process according to  claim 16  wherein the iron content of the ilmenite, expressed as FeO, is less than 30%. 
     
     
         18 . A process according to  claim 1  wherein free oxygen in the treatment atmosphere is no greater than 2.5%. 
     
     
         19 . A process according to  claim 1  wherein the Ti02 content achieved in said synthetic rutile product is at least 93%. 
     
     
         20 . A process according to  claim 1  wherein the ilmenite unsuited to the standard Becher process is one of a primary ilmenite and a hybrid ilmenite. 
     
     
         21 . A process according to  claim 1  wherein the ilmenite unsuited to the standard Becher process is a Murray Basin ilmenite of relatively low Ti content and higher impurity content. 
     
     
         22 . A process according to  claim 3  wherein the selected coal has impurity levels of one or more ion-exchanged inorganic elements sufficiently high to increase the gasification rate of the coal thus improving the reducing conditions in the process and thereby increasing said rate of reduction of iron oxides and titanium species. 
     
     
         23 . A process according to  claim 22  wherein the acid extractable portion of said one or more ion-exchanged inorganic elements is at least 50%. 
     
     
         24 . A process according to  claim 3  wherein the selected coal has relatively high impurity levels of ion-exchanged calcium. 
     
     
         25 . A process according to  claim 3  wherein the selected coal is a sub-bituminous or lignite coal. 
     
     
         26 . A process according to  claim 25  wherein the selected coal has a total moisture content between 5 and 40%, volatiles content greater than 30%, and ash content below 10%. 
     
     
         27 . A process according to  claim 25  wherein inherent moisture content of the selected coal is 20% or less, volatiles content is >40% and ash content is <5%. 
     
     
         28 . A process according to  claim 5  wherein the selected coal is a sub-bituminous or lignite coal. 
     
     
         29 . A process according to  claim 28  wherein the selected coal has a total moisture content between 5 and 40%, volatiles content greater than 30%, and ash content below 10%. 
     
     
         30 . A process according to  claim 28  wherein inherent moisture content of the selected coal is 20% or less, volatiles content is >40% and ash content is <5%. 
     
     
         31 . A process according to  claim 28  wherein the acid extractable portion of said one or more ion-exchanged inorganic elements is at least 50%. 
     
     
         32 . A process according to  claim 3  wherein the sulphur content of the coal is less than 1% w/w, and there is no added sulphur present for most of the duration of said treatment. 
     
     
         33 . A process according to  claim 32 , wherein the sulphur content of the coal is less than 0.5%. 
     
     
         34 . A process according to  claim 32  further including delivering sulphur to the ilmenite during said treatment step for removing manganese impurity as manganese sulphide, such delivery being effected only later during the duration of the reduction treatment. 
     
     
         35 . A process according to  claim 1  wherein the iron content of the ilmenite, expressed as FeO, is less than 30%. 
     
     
         36 . A process according to  claim 3  wherein the Ti02 content achieved in said synthetic rutile product is at least 93%. 
     
     
         37 . A process according to  claim 3  wherein the ilmenite unsuited to the standard Becher process is one of a primary ilmenite and a hybrid ilmenite. 
     
     
         38 . A process according to  claim 3  wherein the ilmenite unsuited to the standard Becher process is a Murray Basin ilmenite of relatively low Ti content and higher impurity content. 
     
     
         39 . A process according to  claim 12  wherein the Ti02 content achieved in said synthetic rutile product is at least 93%. 
     
     
         40 . A process according to  claim 12  wherein the ilmenite unsuited to the standard Becher process is one of a primary ilmenite and a hybrid ilmenite. 
     
     
         41 . A process according to  claim 12  wherein the ilmenite unsuited to the standard Becher process is a Murray Basin ilmenite of relatively low Ti content and higher impurity content.