AU627072B2

AU627072B2 - Process for producing titanium dioxide concentrates

Info

Publication number: AU627072B2
Application number: AU62420/90A
Authority: AU
Inventors: Hiromi Koga; Tadayoshi Nakamura; Akira Ueno
Original assignee: Ishihara Sangyo Kaisha Ltd
Current assignee: Ishihara Sangyo Kaisha Ltd
Priority date: 1989-09-12
Filing date: 1990-09-11
Publication date: 1992-08-13
Anticipated expiration: 2010-09-11
Also published as: MY106846A; AU6242090A

Description

S 627072 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION NAME ADDRESS OF APPLICANT: Ishihara Sangyo Kaisha, Ltd.

3-22, Edobori-l-chome Nishi-ku Osaka Japan NAME(S) OF INVENTOR(S): Hiromi KOGA Tadayoshi NAKAML RA Akira UENO ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

9 S COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: d\ox'\de Process for producing titanium Leide concentrates The following statement is a full description of this invention, including the best method of performing it known to me/us:- .i 1 BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a process cd; for producing a titanium oxide concentrate which is an upgrade material rich in titanium oxide and suitable for a fluidized chlorination process by removing an S° iron content from a titaniferous ore or similar ores S(merely. referred to as "titaniferous ores or materials).

RELATED ART S 10 Titanium tetrachloride used as raw material o 4 t in the production of titanium dioxide pigment by a chloride process and metallic titanium is usually obtained S. by the chlorination of titaniferous materials by a 0441 fluidization process. In this case, it is important that the titaniferous materials are upgrade and 0 o0 substantially free from fine powder and can easily be chlorinated by a fluidization process.

,As such titaniferous materials, there are used natural rutile and upgrade titanium oxide concentrates obtained by removing an iron content from titaniferous ores such as ilmenite, and ilmenite-hematite ores. As an industrial method for removing an iron content, there is a method of leaching titaniferous ores with sulfuric acid, in which the ores are previously reduced to a ferrous state and a seed for the acceleration -la 7- i 1 of hydrolysis of a titanium salt, or a titanium (III) salt is allowed to be present at the time of leaching.

(See Japanese Patent Kokoku Post-Exam. Publn=Nos.

49-18330 and 49-37484).

In the conventional partial reduction-acid leaching method, titaniferous ores of a high metamorphic grade of which the titanium component can easily be concentrated have been used as raw materials, but because of the recent reduction of resources thereof, there is a o, 10 need to utilize a titaniferous ore of a low miotamorphic grade which has not been considered much. However, ea according to the conventional technique, it is o difficult to obtain the desired upgrade titanium oxide concentrate from the ore of a low metamorphic grade.

SUMMARY OF THE INVENTION I The object of the present invention is to provide a method for producing a titanium oxide 0 concentrate from a titaniferous ore of a low metamorphic grade.

20 As a result of the inventors' study on the 41 treating conditions of respective steps in the method Sfor obtaining the titaniumoxide concentrate by first oxidizing the titaniferous ore of a low metamorphic grade, then reducing the ore and thereafter leaching it with sulfuric acid, it has been found that the removal of iron easily proceeds at leaching when the oxidization of the ore is carried out so that the RA(L 2- L 1 oxidized ore has a pseudo-brookite structure and 90-100% of the iron content is converted to a ferric state and thereafter the ore is reduced and leached with sulfuric acid.

That is, the present invention is a method for ci producing a titanium oxide concentrate, characterized by oxidizing a titaniferous ore to make an oxidized ore which has a pseudo-brookite structure and of which 9 0 -100%Lof the iron content is in a ferric state, 10 reducing the oxidized ore at a temperature of 700-950 0

C

and then leaching the ore with sulfuric acid to remove iron from the ore.

The present invention further includes a method for producing a titanium oxide concentrate where a titanium (III) salt and/or a seed for the acceleration of hydrolysis of the titanium salt are added in case of a4 t leaching with sulfuric acid.

44.* S DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Raw titaniferous ores used in the present 20 method include, for example, ilmenite, metamorphic materials of ilmenite, such as ilmenite-hematite ore, and these ores which have been subjected to pretreatment, and ores having a composition and properties similar to those of the above ores. The effect of the present invention is remarkable when the titaniferous ore containing at least 10% of ferrous iron is used as raw ore. The particle size of the ores used is normally R 1 1 3 1 1 i j -j *441 44 a( I 99( o at a to a4 t o 0 1 within the range of 50-500 pm, but ores which are larger than this size can be ground.

According to the method of the present invention, first a titaniferous ore is oxidized at a pre-f'eracy "\ore temperature of 900 0 C or higher,kpreferably 950-1050 0

C

to make an oxidized ore which has a pseudo-brookite structure and of which 90-100% of the iron content is in a ferric state. This oxidation prior to the reduction referred to hereinafter results in the 10 conversion of the titaniferous ore to the state predominantly having the pseudo-brookite structure. It is important that 90-100%, preferably 95-100% of the iron content is converted to a ferric state by the oxidation.

If the content of ferric iron is less than 90% or the pseudo-brookite structure is not present in the oxidized ore, the removal of iron by the subsequent leaching with sulfuric acid cannot sufficiently be performed. An oxygen-containing gas such as air is normally used as an oxidizing agent. A fluidized bed type reactor, rotary kiln and the like are used as reaction apparatuses. An oxidizing period of time is usually 10-120 minutes.

Next, this oxidized ore is reduced at a temperature of 700-950 0 C, preferably 800-900°C to convert most of iron to iron in a ferrous state which can easily be leached in the subsequent leaching step with sulfuric acid. By this reduction treatment, the content of ferric iron in the reduced ore is decreased I- 4 ;I i I Sj^ 1 4409 4 94 9* 4 49 4 99490 I I ii 1 to 10% or less, preferably 5% or less based on the amount of iron content. If the reducing temperature is lower than 700 0 C, the content of ferric iron is more than and the removal of iron by leaching with sulfuric acid cannot sufficiently be performed. If the reducing temperature is higher than 950°C, the elution of iron cannot sufficiently be performed and the yield of titanium oxide decreases.

The reducing agent includes, for example, gaseous oto' 10 reducing agents such as H2 and CO, mixed gases thereof, reducing gases obtained by reforming hydrocarbon gases e such as natural gas, and solid reducing agents such as coke, S' coal and charcoal. Especially, the reducing gases obtained 0 4 by reforming natural gases and mainly composed of methane are industrially preferred. Fluidized bed type reactors, rotary kiln and the like arekused as reducing apparatuses. A reducing period of time is usually 10-120 minutes. After the reduction, impurity particles mainly composed of silica and alumina obtained in the ore or remaining reducing agent in case of using the solid "*44 reducing agent cankbe removed by subjecting the reduced I! ore to the magnetic separation treatment.

Next, this reduced ore is leached with sulfuric acid. As the leachant, mineral acids such as hydrochloric acid can be considered to be used in addition to sulfuric acid, but sulfuric acid is most preferred for attaining the object of the present 1 4 d -0 ;s i; I te9 9r '4 9Y 9 9 9 9 991 9 14 99 A 904 9 9* 94 4t 999 1 invention and industrially carrying out the present invention. As sulfuric acid, mention may be made of a waste sulfuric acid discharged from the hydrolysis step in the production of titanium dioxide pigment by a sulfate process and a pickling acid discharged from the pickling step in iron making industries. The concentration of sulfuric acid is suitably 100-500 g/l in terms of free H2SO4* The amount of sulfuric acid used iskabout 1.5-3 times the chemical equivalent necessary to 10 dissolve impurities in the ore. Leaching is usually carried out at a temperature from the boiling point to 150 0 C for 3-15 hours. An autoclave and the like are used as a leaching apparatus.

Furthermore, in this leaching with sulfuric acid, the elution speed and elution amount of iron can be di increased and besides the yield of titanium oxide can be enhanced by allowing a titanium (III) salt and/or a seed for the acceleration of titanium salt hydrolysis to be present in an eluate. For allowing the titanium (III) salt 20 to be present in the system, there are a method of adding a titanium (III) sulfate solution, a method of reducing a titanium (IV) salt in the system to a titanium (III) salt by adding a metallic iron powder to the eluate, and the like. The seed for the acceleration of hydrolysis of the titanium salt is a seed crystal used for the precipitation of titanium by the hydrolysis of a titanium salt solution in the production of a *itanium dioxide pigment by a general sulfuric acid process. This is prepared, 6i1 I-I 1 for example, by neutralyzing an acidic solution of a titanium salt such as titanium oxysulfate and properly aging the precipitated colloidal titanium compound.

When the titanium (III) salt and/or seed for the acceleration of hydrolysis of a titanium salt are used, the amount of the titanium (III) salt added is 1-15 g/l, preferably 2-10 g/l in terms of TiO 2 for an amount of liquid at the initial stage of leaching.

The added amount of the seed for the acceleration of 10 hydrolysis of a titanium salt is about 0.05-2%, normally 0.1-1% in terms of TiO 2 of titanium in the seed based on the reduced ore.

SAfter leaching with sulfuric acid, fine 4 r4 powders are removed and the remainder powders are subjected to washing and filtration and, if necessary, to drying, and thereafter calcined at a temperature of 800-1,000°C o to obtain an upgrade titanium oxide concentrate. If o 4 necessary, an eluate before calcination may be subjected to magnetic separation by a magnetic separator to di separate the titaniumgoxide concentrate as non-magnetic material and then the titanium/oxide concentrate may be calcined.

The titanium oxide concentrate produced as above is suitable as raw material to be chlorinated by the fluidization process.

In this specification, is by weight unless otherwise notified.

t *I a _fiB 1 4Ul

Q

.4 *I 44 44p 1 Example 1 Table 1 (unit: Components TiO 2 FeO Fe203 MnO MgO Al 2 0 3 SiO 2 Content 59.1 16.2 15.8 2.87 0.12 0.98 1.64 1,000 g of a titaniferous ore having a composition as shown in Table 1 was charged in a rotary kiln and was oxidized with a mixed gas of air and nitrogen 5 in an equal amount at 20 1/min for 30 minutes at 1,000 0

C.

In the resulting oxidized ore, 99.2% of the iron content was in a ferric state. This oxidized ore was analyzed by X-ray diffractometry to find no ilmenite structure, but find a pseudo-brookite structure and rutile structure.

Subsequently, this oxidized ore was reduced by passing a reducing gas (H 2 50 vol% and N 2 50 vol%) at 1/min for 45 minutes at 850 0 C. Then, this was cooled to 100 0 C while passing nitrogen gas was subjected to the removal of non-magnetic materials by a small-sized magnetic separator under 13,500 Gauss. The state of iron in this reduced ore is shown in Table 2. in Table 2 means the total amount of iron contained in the reduced ore.) This reduced ore was analyzed by X-ray diffractometry to find no pseudo-brookite structure.

Ii 8 c .i Table 2 (unit: Components Fe /T-Fe Fe /T-Fe Content 98.0 1 400 g of this reduced ore was charged in an iron-made autoclave having a lead lining and provided with a stirrer and 1.2 liter ofa leachant (concentration of free H2SO4: 265 g/l) prepared by adjusting a waste 5 sulfuric acid discharged from the hydrolysis step of the production of titanium dioxide pigment by a sulfate process and leaching was carried out at 130 0 C for 8 hours.

Thereafter, fine powders were removed by a sieve of 200 mesh (74 im) and the coarse powders were washed and filtered, then dried and calcined at 900 0 C for 1 hour to obtain a titanium oxide concentrate of the present invention. (Sample A) 4 4 1 Example 2 di A titanium.

4 oxide concentrate of the present invention (Sample B) was obtained in the same manner as in Example 1, except that the oxidation of the ore was carried out at 1,050 0 C for 20 minutes to obtain an oxidized ore of which 99.6% of the iron content was in a ferric state and then, the oxidized ore was reduced at 7500C Sfor 60 minutes (Fe3+T-Fe in the reduced ore was 7 for 60 minutes (Fe /T-Fe in the reduced ore was 9 1 Example 3 di A titaniumAoxide concentrate of the present invention (Sample C) was obtained in the same manner as in Example 2, except that titanium (III) sulfate was added in an amount of 6.0 g/l in terms of TiO 2 at the time of leaching with sulfuric acid.

Example 4 A titanium oxide concentrate of the present 'r 4' Cinvention (Sample D) was obtained in the same manner 10 as in Example 1, except that the oxidation of the ore was Pott carried out at 950°C for 30 minutes to obtain an oxidized ore of which 98.4% of the iron content was in a Oi a ferric state, and then this oxidized ore was reduced at 850 0 C for 45 minutes by passing a reducing gas

(H

2 30 vol%, CO: 20 vol%, CO 2 5 vol%, and N 2 45 vol%) 3+ at 20 1/min (Fe /T-Fe in the reduced ore was i Example di A titanium oxide concentrate of the present invention (Sample E) was obtained in the same manner as 20 in Example 4, except that titanium (III) sulfate in an amount of 4.0 g/l in terms of TiO 2 and a seed for the acceleration of hydrolysis obtained by neutralyzing titanium oxysulfate in an amount of 0.3% in terms of TiO 2 of titanium contained therein were added at the time of leaching with sulfuric acid.

!J

1 Example 6 A titanium oxide concentrate of the present invention (Sample F) was obtained in the same manner as in Example 1, except that the oxidation of the ore was carried out for 60 minutes at 920 0 C to obtain an oxidized ore of which 93.6% of the iron content was in a ferric state; this oxidized ore was reduced at 925 0 C for 30 minutes by passing a reducing gas (H 2 vol%, CO: 20 vol%, CO 2 5 vol%, N 2 45 vol%) at 20 1/min 10 (Fe /T-Fe in the reduced ore was and titanium (III) sulfate in an amount of 7.0 g/l in terms of TiO 2 and a seed for the acceleration of hydrolysis obtained by neutralizing titanium oxysulfate in an amount of 0.4% in terms of TiO 2 of titanium contained therein were added at the time of leaching with sulfuric acid.

Comparative Example 1 A titanium oxide concentrate (Sample G) was l obtained in the same manner as in Example 1, except that the oxidation of the ore was carried out for 90 minutes S 20 at 850 0 C to obtain an oxidized ore of which 92.0% of the iron content was in a ferric state, but any pseudobrookite structure was not seen.

Comparative Example 2 di A titanium 4 oxide concentrate (Sample H) was obtained in the same manner as in Example 1, except that the oxidation of the ore was carried out at 800 0 C for 120 S- 11 i T o 4 RAU a.

T. T 1: 8Ir 8* 4i 8 8

I,

II

1 minutes to obtain an oxidized ore of which 88.0% of the iron content was in a ferric state and no pseudobrookite structure was seen and, furthermore, titanium (III) sulfate in an amount of 7.0 g/l in terms of TiO 2 and a seed for the acceleration of hydrolysis obtained by neutralized titanium oxysulfate in an amount of 0.4% in terms of TiO 2 of titanium contained therein were added at the time of leaching with sulfuric acid.

Comparative Example 3 10 A titanium oxide concentrate (Sample I) was obtained in the same manner as in Example 1, except that the reduction was carried out at 975 0 C for 30 minutes (Fe3+/T-Fe in the reduced ore was Comparative Example 4 A titanium lxide concentrate (Sample J) was obtained in the same manner as in Example 1, except that the reduction was carried out at 650 0 C for 90 minutes (Fe3+/T-Fe in the reduced ore was 17.6%) and titanium (III) sulfate was added in an amount of 7.0 g/l in terms of 20 TiO 2 and a seed for the acceleration of hydrolysis obtained by neutralizing titanium oxysulfate in an amount of 0.4% in terms of TiO 2 of titanium contained therein were added at the time of leaching with sulfuric acid.

The TiO 2 grade, TiO 2 yield and the removal of iron of the titanium oxide concentrates obtained above are shown in Table 3. The TiO 2 grade in Table 3 is 444r 8E 8 *4 t 41 04484I 4

I

B

i

I

j 3 j 12 i i 'Y ii C.L .I i. -L i~r~

CI

t 0 64i 0, O 6 00 0 00410 01 1 indicated with the percentage of TiO 2 content in the titanium oxide concentrates, the TiO 2 yield is indicated with the percentage of Tio 2 content in the titanium oxide concentrates based on the TiO 2 content in the reduced ore to be leached, and the removal of iron is indicated with the percentage of the iron content eluted based on iron content in the reduced ore to be leached.

Table 3 Titanium oxide concentrate Sample TiO 2 grade TiO 2 yield Removal of iron Example 1 A 95.0 97.6 98.0 S 2 B 91.8 96.6 91.8 S 3 C 93.4 96.8 95.0 4 D 92.8 96.0 94.2 S 5 E 95.6 98.4 98.6 S 6 F 94.0 95.0 96.3 Comparative G 86.5 92.4 82.2 Example 1 2 H 88.5 93.0 86.4 S 3 I 88.0 87.2 87.5 4 J 85.2 93.2 78.5 The present invention provides a process for i obtaining an upgrade titanium oxide concentrate from titaniferous ores of a low metamorphic grade without greatly changing the conventional apparatus and 13 i e m i- i cxt 1technique. The titaniuln xide concentrate obtained by this process is suitable as raw material for chlorination by the industrial fluidization process.

be 4 04 a 464 1 t 44 IL 4

I

14

Claims

1. A process for producing a titanium dioxide concentrate, which comprises oxidizing a titaniferous ore to obtain an oxidized ore which has a pseudo-brookite structure and of which 90-100% by weight of the iron content is in a ferric state, then reducing the oxidized ore at a temperature of 700-950°C and thereafter leaching the reduced ore -iith sulfuric acid to remove the iron content in the -e.

2. A process for producing a titanium dioxide concentrate according to Claim 1, wherein the leaching with sulfuric acid is carried out in the presence of at least one material selected from the group consisting of a titanium (III) salt and a seed for the acceleration of hydrolysis of a titanium salt. .o

3. A process for producing titanium dioxide S: 20 concentrates, substantially as hereinbefore described with reference to the examples. e a S: -i DATED this 28th day of May, 1992 Ishihara Sangyo Kaisha, Ltd. By Its Patent Attorneys DAVIES COLLISON CAVE II RRi 920528,dbdat124,62420.res,15 4 34