Title of Invention

AN IMPROVED PROCESS FOR PRODUCING SYNTHETIC RUTILE FROM ILMENITE

Abstract A process of producing synthetic rutile from ilmenite, where granular ilmenite together with granular, carbonaceous reducing agent is charged into a rotary tube, and by supplying air in the rotary tube the ilmenite is reduced at temperatures in the range from 1000 to 1300°C, the mixture containing reduced ilmenite is cooled to temperatures in the range from SO to 200°C, and from the cooled mixture a fine grain fraction containing reduced ilmenite with grain sizes of 0 to not more than 1 mm is separated by screening, which fine grain fraction contains carbon, ash and gangue, characterized in that the fine grain fraction is supplied to an aeration stage, in which the fine grain fraction is stirred in an aquaous chloride solution by supplying air, where iron oxides are formed, that from the aeration stage a suspension containing synthetic rutile, iron oxides, carbon, ash and gangue is withdrawn, which is passed through a gravity separation, where a product phase and a phase rich in iron oxide are obtained, the solids of the product phase comprise 85 to 100 wt-% TIO2, and the phase rich In iron oxide contains 90 to 100 wt-% of the carbon, 90 to 100 wt-% of the ash and 80 to 100 wt-% of the gangue, which are contained In the fine grain fraction coming from the screening and supplied to the aeration zone.
Full Text This inv&ntion relates to an improved process for producing synthetic rutile from ilmenite.
Description
This invention relates to a process of producing synthetic rutile from ilmenite, where granular ilmenite together with granular, carbonaceous reducing agent is charged into a rotary tube, and by supplying air in the rotary tube the ilmenite is reduced at temperatures in the range from 1000 to 1300°C/ the mixture containing reduced ilmenite is cooled to temperatures in the range from 50 to 200^0, and from the cooled mixture a fine grain fraction containing reduced ilmenite with grain sizes of 0 to not more than 1 mm is separated by screening, which fine grain fraction contains carbon, ash and gangue-
Such process is described in the U.S. Patent No. 5,403,379, where together with screening a magnetic separation is effected in addition, as the reduced ilmenite is strongly magnetic and can be separated from nonmagnetic impurities such as ash and gangue.
IA

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The object underlying the invention is to provide a rather inexpensive process of producing synthetic rutile, where a magnetic separation is omitted. In accordance with the invention this is achieved in the above-mentioned process in that the fine grain fraction is supplied to an aeration stage, in which the fine grain fraction is stirred in an aqueous chlo-ride solution by supplying air, where iron oxides are formed,
f.that from the aeration stage a suspension containing synthetic rutile, iron oxides, carbon, ash and gangue is with-drawn, which is passed through a gravity separation, where a product phase and a phase rich in iron oxide are obtained, the solids of the product phase comprise at least 85 wt-% TiO2, and the phase rich in iron oxide contains at least 90 1 wt-% of the carbon, at least^TO wt-%^f the ash and at least /80 wt-%._o-f the gangue, which are contained in the fine grain fraction coming from the screening and supplied to the aeration zone.
The process in accordance with the invention operates without the expensive magnetic separation, and the mixture containing the reduced ilmenite is supplied from the cooler directly into the screening, and from the screening the fine grain fraction is supplied directly to the aeration stage. Carbon, ash and gangue are only separated from the product phase by gravity separation. Usually, screening is effected such that the desired fine grain fraction has grain sizes up to not more than 1 mm.
It is recommended to use an ammonium chloride solution as aqueous chloride solution in the aeration stage. The chloride concentration of the solution usually lies in the range from 7 to 30 g/1.
For the gravity separation of the suspension coming from the aeration stage there is advantageously used at least one hy-drocyclone, at least one hydroseparator or at least one cen-

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trifuge. It is also possible to connect a plurality of these different apparatuses in parallel or in series. The hydro-separators known per se are also referred to as upstream classifiers, when they operate with water flowing upwards.
When the gravity separation is effected by one or several hy-drocyclone stages, it is recommended to employ cyclones with a relatively small diameter. With a higher pressure loss there are also achieved higher centrifugal forces, which improves the separation of solids. The number of the cyclone stages connected in series usually lies in the range from 2 to 4 cyclone stages. The number of the hydrocyclones per stage, which are connected in parallel, expediently lies in the range from 1 to 5 and preferably 1 to 2 hydrocyclones.
Further embodiments of the process will be explained with reference to the drawing, which represents a schematic flow diagram.
To the rotary tube 1 coal, ilmenite, sulfur and recirculated coke (char) are supplied through the charging tube 2. Sulfur or sulfur-containing material may also be introduced from the discharge end of the rotary tube. The grain sizes usually lie below 50 mm. The addition of sulfur per kg ilmenite usually is about 5 to 25 g, and there may not only be added elemen-tary sulfur, but also a sulfur compound. The temperatures in the rotary tube lie in the range from 1000 to 1300°C and preferably 1100 to 1200°C. Blowers 5 connected with the rotary tube deliver combustion air into the interior of the rotary tube, and by means of the coal injection system 6 coal is additionally supplied to the rotary tube by means of air. In the rotary tube 1, the iron oxide content of the ilmenite is reduced.
Hot exhaust gas leaves the rotary tube through the duct 8 and the chimney 9. Separated dust is removed through line 11; it

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is mostly recirculated to the rotary tube in a manner not represented here.
In the rotary tube 1 a hot mixture is formed, which contains reduced ilmenite. This mixture is delivered through the transfer chute 15 to a rotary tube cooler 16, onto the shell of which cooling water is directed from the outside through line 17. From the cooler 16 through the cooler discharge chute 18 a cooled solids mixture with temperatures in the range from 50 to 200°C and preferably not more than 90°C is withdrawn and delivered to a screening means 20, where a coarse fraction is separated, which contains coal and is discharged via line 21. The remaining fine grain fraction, which has grain sizes up to not more than 1.0 mm and preferably not more than 0.8 mm, chiefly consists of reduced ilmenite. The fine grain fraction in addition contains carbon, ash and gangue.
The fine grain fraction from the screening 20 is dosed and delivered through line 22 to a pump condensate tank 23, to which there is also supplied an agueous chloride solution through line 24. The mixture of the tank 23 then flows into an aeration stage 25; air is supplied via line 27. Metallic iron is oxidized by stirring. Usually, several tanks are employed, which are operated continuously or discontinuously, which is, however, not represented in the drawing for simplification. The chloride solution preferably is an ammonium chloride solution, where the chloride concentration lies in the range from 7 to 30 g/1. Oxygen in the form of air is introduced in a hyperstoichiometric amount, with reference to the desired oxidation reactions, where per mol metallic iron 2 to 5 mol O2 are calculated.
From the aeration stage 24 through line 26 a suspension is withdrawn, which contains synthetic rutile, iron oxides, carbon, ash and gangue. This suspension is first introduced into

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the intermediate tank 28. From here, the suspension is supplied to a separating means 30, which preferably operates according to the principle of gravity. The product phase rich in TiO2/ which was recovered through the separation 30, is withdrawn via line 38, the phase poor in TiO2/ which chiefly contains iron oxides, carbon, ash and gangue, is delivered through line 37 to a settling tank 45, where the solids are deposited and, if necessary, can be withdrawn through line 46. A largely clarified chloride solution is withdrawn from the tank 45 through line 25, mixed with fresh solution from line 49, and first of all introduced into the storage tank 50, from where the solution flows into the pump condensate tank 23.
In the product phase rich in TiO2 in line 38 the solids comprise at least 85 wt-% and preferably at least 90 wt-% TiO2. By filtering and drying this product might be recovered as saleable material already at this point. Usually, a higher purity of the product is desired. This can be achieved in a manner known per se by leaching in an aqueous sulfuric-acid solution. In the drawing, the leaching 55 is shown in a simplified representation with its addition of dilute sulfuric acid through line 56. In the suspension withdrawn via line 57 the synthetic rutile is contained, which is dehydrated and recovered, for instance, after filtering and drying (not represented). Exhaust gas is withdrawn via line 58.
Example:
For operating on a laboratory scale, an Australian ilmenite has been provided, which was reduced with coal in the rotary tube furnace at 1200°C. The screened fine grain fraction with grain sizes of not more than 0.7 mm has the following chemical analysis:

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TiO2 63.4 wt-%
Fe 24.9 wt-%
Iron oxides 2.1 wt-%
C 2.0 wt-%
S 0.7 wt-%
Mn 0.9 wt-%
SiO2 + A12O3 + MgO 5.7 wt-%
other substances 0.3 wt-%
The aeration is effected in a stirred tank by supplying air in an aqueous ammonium chloride solution with a chloride content of 20 g/1 for 8 hours. The pH value of the suspension is about 6, the temperature rises to 80°C as a result of exothermal reactions. After the aeration, the suspension is passed through 5 series-connected hydrocyclones of porcelain, which each have a maximum inside diameter of 50 mm. At the entrance into the below-mentioned hydrocyclone, the suspension has the following weight per liter:
1st cyclone 1.35 kg
2nd cyclone 1.45 kg
3rd cyclone 1.45 kg
4th cyclone 1.45 kg
5th cyclone 1.25 kg
The phases poor in TiO2, which leave the respective cyclone, are collected and not used any further, they contain coal and ash. The product phase coming from the 5th hydrocyclone has the following chemical analysis of the solids indicated in column A (in wt-%):

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A B
TiO2 91.1 91.4
Fe (total) 2.9 2.7
SiO2 1.1 1
A12O3 1.2 1.2
MgO 0.24 0.23
Mn 0.84 0.85
C 0.35 0.26
S 0.74 0.73
97 wt-% of the TiO2 delivered to the aeration are obtained in the phase rich in TiO2 (product phase) of the 5th hydrocy-clone. When for comparison purposes the screened fine grain fraction is subjected to a magnetic separation prior to the aeration, for separating carbon and ash, the aeration is performed as described above, and aerated suspension is passed through a hydrocyclone, the solids of the heavy phase have the composition indicated in column B of the above table. There are recovered 95 wt-% of the TiO2 supplied to the magnetic separation.

-8-WE CLAIM
1. A process of producing synthetic rut He from ilmenile, where granular iimenile
together with granular, carbonaceous reducing agent is charged into a rotary
tube, and by supplying air In the rotary tube the ifmenite is reduced at
temperatures In the range from 1000 to 130Q°C, the mixture containing
reduced ilmenite is cooled to temperatures in the range from 50 to 200°C, and
from the cooled mixture a fine grain fraction containing reduced ilmenite with
grain sizes of 0 to not more than 1 mm is separated by screening, which fine
grain fraction contains carbon, ash and gangue, characterized in that the fine
grain fraction is supplied to an aeration stage, in which the fine grain fraction
is stirred in an aqueous chloride solution by supplying air, where iron oxides
are formed, that from the aeration stage a suspension containing synthetic
rut He, iron oxides, carbon, ash and gangue is withdrawn, which is passed
through a gravity separation, where a product phase and a phase rich in iron
oxide are obtained, the solids of the product phase comprise 85 to 100 wt-%
TiO2, and the phase rich In iron oxide contains 90 to 100 wt-% (of the carbon,
90 to 100 wt-% of the ash and 80 to 100 wt-%*Jf the gangue, which are
contained in the fine grain fraction coming from the screening and supplied to
the aeration zone.
2. The process as claimed in claim 1, wherein the solids content of the aqueous
solution in the aeration stage is maintained in the range from 25 to 50 wt-%.
3. The process as claimed in claim 1, wherein by means of screening a fine
grain fraction containing reduced ilmenite with grain sizes from 0 to 1.0 mm is

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separated from the cooled mixture and supplied to the aeration stage.
4. The process as claimed in claim 1 or any of the preceding claims, characterized in that as aqueous chloride solution an ammonium chloride solution with a chloride concentration of 7 to 30 g/1 is used in the aeration stage
5- The process as claimed in claim 1 or any of the preceding claims, characterized in that for gravity separation at least one hydrocyclone, at least one hydroseparator or at least one centrifuge is used.
6. The process as claimed in claim 1 or any of the preceding claims, characterized in that from the phase rich in iron oxide solids are separated, and the chloride solution is recovered, which is recirculated to the aeration stage at least in part.
A process of producing synthetic rutile from ilmenite, where granular ilmenite together with granular, carbonaceous reducing agent is charged into a rotary tube, and by supplying air in the rotary tube the ilmenite is reduced at temperatures in the range from 1000 to 1300°C, the mixture containing reduced ilmenite is cooled to temperatures in the range from SO to 200°C, and from the cooled mixture a fine grain fraction containing reduced ilmenite with grain sizes of 0 to not more than 1 mm is separated by screening, which fine grain fraction contains carbon, ash and gangue, characterized in that the fine grain fraction is supplied to an aeration stage, in which the fine grain fraction is stirred in an aquaous chloride solution by supplying air, where iron oxides are formed, that from the aeration stage a suspension containing synthetic rutile, iron oxides, carbon, ash and gangue is withdrawn, which is passed through a gravity separation, where a product phase and a phase rich in iron oxide are obtained, the solids of the product phase comprise 85 to 100 wt-% TIO2, and the phase rich In iron oxide contains 90 to 100 wt-% of the carbon, 90 to 100 wt-% of the ash and 80 to 100 wt-% of the gangue, which are contained In the fine grain fraction coming from the screening and supplied to the aeration zone.

Documents:

00796-cal-1998 abstract.pdf

00796-cal-1998 claims.pdf

00796-cal-1998 correspondence.pdf

00796-cal-1998 description (complete).pdf

00796-cal-1998 drawings.pdf

00796-cal-1998 form-1.pdf

00796-cal-1998 form-2.pdf

00796-cal-1998 form-3.pdf

00796-cal-1998 letters patent.pdf

796-CAL-1998-CORRESPONDENCE 1.1.pdf

796-CAL-1998-FORM 15.pdf

796-CAL-1998-FORM-27.pdf


Patent Number 201964
Indian Patent Application Number 796/CAL/1998
PG Journal Number 08/2007
Publication Date 23-Feb-2007
Grant Date 23-Feb-2007
Date of Filing 05-May-1998
Name of Patentee METALLGESELLSCHAFT AKTIENGESELLSCHAFT
Applicant Address BOCKENHEIMER LANDSTRASSE 73-77, D-60325, FRANKFURT AM MAIN, GERMANY
Inventors:
# Inventor's Name Inventor's Address
1 LOTHAR FORMANEK LIBELLENWEG 67, D-60529 FRANKFURT AM MAIN, GERMANY
2 ALI NAGHI BEYZAVI PETER HENLEIN STRASSE 22, D-60435, FRANKFURT AM MAIN GERMANY
PCT International Classification Number C 01 G 23/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA