CA1116866A - Separation of ilmenite and rutile - Google Patents

Abstract

SEPARATION OF ILMENITE AND RUTILE

ABSTRACT
This invention relates to a process for separating rutile and ilmenite from ilmenite leach tails and is effected by treating the leach tails from an acidic leach to a flota-tion step whereby gangue is separated from the unreacted il-menite and rutile. The latter is then roasted at an elevated temperature in a hydrous atmosphere to convert the ilmenite to a magnetic material. Thereafter the ilmenite may then be subjected to a magnetic separation whereby non-magnetic rutile may be recovered while the magnetic portion is re-cycled for further separation.

Description

1111;~366 SEPARAT O~ OE IL~EI~Iq'E l~lD RUTiLE

SPECIFICATION

Titanium in met(lllic form or as a compound is an important element in the chemical series. For example, titanium dioxide is utilized in paint pigments, in white rubbers and plastics, floor coverings, glassware and ceramics, painting inks and as an opacifying agent in papers. The other titanium compounds are used in elec-tronics, as fire ~- retardants and waterproofing agents. The metal may be used as such or in alLoy form as structural material in aircraft, in jet engines, marine equipment, textile machir.ery, surgical instruments, orthopedi.c applicances, sporting equipment and food handling equipment. Ileretofore in recovering the ti-^1 tanium from titanium bearing sources such as ilmenite, rutile, etc., the titanium has been subjected to separation steps which-involve the formation of titanium as a compound in a ~5 valence state of +4, such compounds usually involving titanium oxide. However, when attempting to separate titanium dioxide from impurities which are also contained in the ore such as iron, the hydrolysis of the titanium dioxide at elevated temperatures from solutions con-taining soluble titanium species usually results in also obtaining relatively large amounts of iron impurity with the titanium dioxide product.
In the prior ar-t, various methods have been utilized to recovcr titanium values from titanium bearing sources.
For example, in U.S. Patent No. 3,236,596 an unroasted il-menite ore is leached with hydrogen chloride at an elevated ~J~
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~:emperat~ . Fol.lo~;.ng this, di.ssolv~d iron is reduced with iron or other reduc~,ants to preclpitate ferrous ch:Lorlde by sat-urating the li.quor with hydrogen chloride gas. The hydro-gel-l chloride is then extracted from -the liquor by a vacuum distillation and the titanium is recove.~ed by conventional means. Likewise, U.S. Patent 3,825,419 reduces an ilmenite ore to produce ferrous oxides. The reduced ore is then leached for about 4 hours under a moderate pressure thereby dissolving the iron in the acid along with about 15% of the titanlum. The iron is recovered as ferric oxide containing impuriti.es in the spray roaster while the insoluble product which is primarily titanium diox:ide but which contains all of the silica present in the original ore is recovered.
U.S. Patent 3,859,077 also discloses a process for recovering - 15 ti-tanium in which a tltanium tetrahalide is mixed with iron oxide in slag or a titaniferous ore at an extremely high temperat~re of about 1000C. to produce volatile impurity chlorides and titanium dioxide. A similar patent, U.S.
Patent 3,929,962 also reduces a titanium bearing ore at a high temperature to produce titanium sesquioxide which is in a forrn whereby it is easier to treat for a titaniurn-iron separation. Another pri,or art reference, U.S. Patent 3,903,239 teaches a method for recovering titanium in which unroast~d ilmenite is leached over a period of days at room temperature to recover about 80~ of the titaniurn. Sulfur dioxide is added after the leaching to cause a precipitation of the ferrous chloride after which titanium dioxide is recovered by diluting and heatirig the solution. While the magnetic susceptibility ~16866 of ilmen.ite hls been known to chancJe by subjecting the il-menite to a hi.gh temperature roast, I have now found t:hat by utilizing th~ process of the present invention it is possible to insure complete conversion of the ilmenite to a magnetic material which then may be separated from non-magnetic rutile and recycled for further treatment. By utilizing the method of the present invention it will be possible to obtain a conversion of the raw ore to the de-sired titanium metal values thereby permitting the pro-duction of said titanium metal values in an economically feasible manr,er.
This invention relate.s to a process for separating rutile from ilmenite. More specifically, the invention is ; concerned with the process for recovering greater yields of titanium from a titanium bearing source such as ilmenite thus insuring the obtention of said titanium in an economi-cally feasible manner. By utilizi.ng the improvement herei.n described in a process for o~taining titanium from a titanium bearing source, it is possible to obtain greater yields of the desired product with a separation of magnetic material from non-magnetic material w.hereby the former may be recycled . for further separation steps.
It is therefore an object of this invention to pro-vide an improved process for the production of titanium metal values.
A further object of this invention is to provide an improvement in a process for separating a titanium metal value such as rutile from a titanium bearing source such as ilrnenite in a more economical and commercicllly fcasible manner .
In one aSE~( ct an embodinlent of this invention re-sides in a process for the separation of rutile and ilmenite from ilmenite leac h tails which compriscs sub jecting said leach tails to a flotation trea~ment to separate gangue from said leach tails, subjecting the separated leach tails to a roast at an elevated temperature in a hydrous atmosyhere where-by said ilmenite is rendered magnetic in nature, and separating the non-magnetic rutile from the magnetic ilmenite.

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A specif ic embodiment of this invention is found in a process for the separation of rutile and ilmenite from ilmenite leach tai ls which comprises sub jecting said leach tails to a flo~ation treatment to separate gangue frc)m said leach tails, thereafter subjecting the separated leach tails to a roast at a- temperature in the range of from about 700 to about 1000C. in a hydrous atmosphere which is afforded by the presence of steam whereby said ilmenite is rendered magnetic in nature and thereafter separating the non-magnetic rutile from the magnetic ilmenite.
The present invention is concerned with a process for separating ilmenite and rutile from ilmenite leach tails.
By utilizing the present proc ess, it will be possible to ef-f~ct a more complete separation of ilmenite from rutile and ultimately obtain a higher yield of the desired titanium metal values. The method for obtaining the desired titanium metal value is effected by subjecting a titanium bearing souxce which also contains other metals including iron, vanadium, chromium ancl manganese, such as an ilmenite ore, .

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~68~6 to a reductive roast at an elevated temperature in the range of from 650 to 1000C., said reductive roast being effectedin the presence of a reductant such as hydrogen, carbon monoxide, combination of carbon monoxide and hydrogen, or any other suitable reductant. In the preferred embodiment the reduc-tive roast is effected on a metal bearing source such as an ore which has been c~ushed to a particle size less than 100 mesh for a period of time which may range from 0 5 up to 2 hours. One particular reducing atmosphere which may be used to accomplish the purpose of the roast comprises a mixture of about 50~ carbon monoxide and 50% hydrogen with an excess of the reductant being utillzed in order to completely re-duce the iron which is present in the system to the metal.
Following the reductive roast of the metal bearing source, the source is then su~jected to an aqueous hydrogen chloride leach which is also effected at elevated temperatures usually in the range of from 85 to 105C. for a period of time ranging from 0.25 up to 1 hour in duration. The aqueous hydrogen chloride solution which may also be characterized as hydrochloric acid will contain from 20% up to 37% hydro-J gen chloride. Upon completion of the leach step the solu-bilized titanium metal values will be separated from the solid tails which will comprise unreacted ilmenite, some rutile and gangue which comprises silica, mica and quartz. v The solid tails which remain are suspended in a water slurry and an appropriate flotation collector reagent is added such as tall oil or oleic acid. The pH of the slurry is adjusted to a range of from 6 to ~. The adjustment of ~h~- p~l is accomplishe~l by the addition of an acid or base, the usLIal additive bein~3 a base such as lime. The slurry is agit.lted viyorously or approxiMatel~ 5 minutes, at which tir;le air bubbles are introduced into the siurry, resulting in ; the ilmenite and ru-tile floating on or near the surface of the slurry while the gangue will sink and collect at the bottom of the vessel. Thereafter the suspended ilmenite ~nd rutile may be filtered or skimmed off with the froth and recovered.
Following recovery of the mixture of ilmenite and rutile, the solids are then subjected to a roast. The roas-t is effec-ted at an elevated temperature in the range of from 700 to 1000C. and preferably at a range of from 750 to 900C. To insure a conversion of the ilmenite to a magnetic material durin(3 the roasting, the a~oresaid roast is effected in a hydrous atmosphere, said hydrous conditions being nec-essary to convert the;ilmenite to a magnetic material rather than remaining non-magnetic in nature. The hydrous atmosphere during the roast is effected by the presence of water which may be in the form of steam or vapor. The ilmenite and ru-tile are roasted in this hydrous atmosphere for a period of tirne which may range from 0.5 up to 2 hours in duration, the amount of time required being that which is sufficent to convert all of the ilmenite to a magnetic material.
Upon completion of the desired roasting period the magnetic ilmenite may be separated from the non-magnetic ru-tile by any conventional means such as applying a magnetic force to the miY~ture whereby the ilmenite is attracted to said magnetic force while the non-magnetic rutile remains in position.

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Thereaf~er the ilme~ite which has been separate~ from the rutile may be recovered and recycled to form a port:ion of the feedstock which is subjected to the aforesaid steps of reductive roasting and leaching, while -the rutile may be recovered and processed in any conventional manner to ob-tain the desired titanium values.
While the aforesaid description of the process is indicative of a batch type operation, it is also contemplated within the scope of this invention that it is possible to ; - 10 effect the process using a continuaus method oE operation ~-in which the charge stock comprising crushed ore is con-tinuously fed to a reducing roast zone wherein the charge is subjected to a reductive roast utilizing a reductant of the type hereinbefore set for-ch which is also continuously charged to this zone. After passage through the zone for a prede-` termined period of time the reduced charge stock is con-tinuously withdrawn and passed to a leaching æone wherein it is subjected to leach treatment with a hydrogen chloride source such as hydrochloric acid. The leaching zone is maintained at an elevated temperature and after passage through this zone the leach liquor and tails are continu-ously withdrawn and passed to a separation zone wherein the leach liquor con-taining dissolved metal chlorides is continu-ously withdrawn after separation from the leach tails. The leach tails comprising undissolved or unreacted ilmenite, rutile and gangue is continuously charged to a flotation zone wherein a flotation slurry is effected at a pH in the range of from 6 to 8, said pH being maintained by the intro-~116866 duction of an acid or base in an amount necessary to afford the desired range. The ilmenite and rutile are continuously withdra~n from this zone ~ decan-tation, filtration or other means known in the art and passed to a roast zone wherein the solids are subjected to a roast at a temperature in the range of from 700 to 1000C. in a hydrous atmosphere, said atmosphere being afforded by the continuous introduction of water in the form of vapor or steam to the roast zone. Ater passage through the roast zone the solids are passed to a separation zone wherein they are subjected to the action of a magnetic force, the magne-tic nature of ilmenite material causing a separation from the non-magnetic rutil~. After separation of the non-maynetic rutile from the magnetized ilmenite has been effected, the latter may be recovered lS by any conventional means and recycled to the reductive roast zone to form a por-tionof the feedstock while the ru-tile is collected and subjected to any convention~ means of treatment whereby the desired titanium values may be recovered.
It is to be unders-tood that the leached liquor which con-tained the dissolved metal chlorides after having been separated from leached tails may be treated to precipitate titanium dioxide which is thereafter recovered and passed to storage.
The following examples are given for purpo$es of illustrating the process of this invention. However, it is to be understood that said examples are given merely for purposes of illustration andthat the present process is not necessarily limited thereto.

EX~MPLE 1 A sample of ilmenite rnay be crushed to -100 mesh and therea~ter heatecl to a temperature of 750C. under nitrogen in a rotating quartz furnace tube. Following this hydrogen and carbon monoxide gas may be passed through the tube at a rate of 640 cc/min. for a period of 1 hour while maintaining -~ the temperature of the tube at about 750C. At the end of the 1 hour period the tube and sample contained therein may be cooled under nitrogen to room temperature and the reduced ilmenite ore may be mixed with concentrated hydrochloric acid and heated to a temperature of 100C. The solid ilmenite ore may be leached for a period of 0.25 hours under reflux and filtered.
The leached solids were suspended in a water slurr,v containing oleic acid. The ph of the slurr,v was adjusted to about 7 by the addition of lime. The slurry was then agitated for five minutes, at which time air bubbles were introduced, - causing the ilmenite and rutile to float on the surface. The ilmenite and rutile were then skimmed off and recovered.
The ilmenite and rutile solids were then roasted for a period of 1 hour at a temperature of 900C in a fluid-bed reactor using steam as the fluidizing gas. After cooling, it was found that the ilmenite in the sample was magnetic in nature and was completely attracted to a magnet.
In contradistinction to this, when a second sample of the ore was roasted for a period of 1 hour at a temperature of 900C. using dry air as a fluidizing gas, the sample after Gooling exhibited no reactivity to the magnet.
EXAMPLE II
In this example a sample of ilmenite ore from Norway was treated in a manner similar to that set forth in Example I above and roasted in a fluid-bed reactor for a period of 2 .

hours at a temperature of 900C. using steam as the fluidizing gas. At the encl of the 2 hour pcriod the sample was cooled and the ilmenite was follnd to be completely attracted to ; a magnet.
A second sample of the ilmenite ore from Norway when roasted at 750C. in a fluid-bed reactor using steam as the fluidizing gas also exhibited a high reactivity to a magnet upon cooling.
Conversely, if the samples of Norwegian ilmenite ore are treated in an oxidizing atmosphere which is anhydrous in nature, the ore, after treatment, will not exhibit any magnetic activity.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the separation of rutile and ilmenite from ilmenite leach tails which comprises subjecting said leach tails to a floculation treatment to separate gangue from said leach tails, subjecting the separated leach tails to a roast in the range of temperatures from about 650° to 1000°C
in a hydrous atmosphere whereby said ilmenite is rendered magnetic in nature, and separating the non-magnetic rutile from the magnetic ilmenite.

2. The process of claim 1 wherein said hydrous atmosphere is afforded by the presence of steam.

3. The process of claim 1 wherein said hydrous atmosphere is afforded by the presence of water vapor.

4. The process of any of claims 1 to 3 wherein said elevated temperature includes temperatures in the range of from 700° to 1000°C.

5. The process of any of claims 1 to 3 wherein the flotation treatment is effected at a pH in the range of from 6 to 8.