CA2001751A1 - Recovery of titanium values from minerals - Google Patents
Recovery of titanium values from mineralsInfo
- Publication number
- CA2001751A1 CA2001751A1 CA002001751A CA2001751A CA2001751A1 CA 2001751 A1 CA2001751 A1 CA 2001751A1 CA 002001751 A CA002001751 A CA 002001751A CA 2001751 A CA2001751 A CA 2001751A CA 2001751 A1 CA2001751 A1 CA 2001751A1
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- process according
- mineral
- bed
- fine
- fine grained
- Prior art date
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-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
- B01J8/32—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with introduction into the fluidised bed of more than one kind of moving particles
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/02—Halides of titanium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/10—Obtaining titanium, zirconium or hafnium
- C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
- C22B34/1218—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining titanium or titanium compounds from ores or scrap by dry processes
- C22B34/1222—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining titanium or titanium compounds from ores or scrap by dry processes using a halogen containing agent
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Combustion & Propulsion (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Silicon Compounds (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
Abstract
ABSTRACT
A process for chlorinating a fine grained mineral containing titanium dioxide in a fluidized bed comprising adding the fined grained mineral to a fluidized bed comprising a coarse grained material and a source of active carbon. A chlorinating agent is introduced into the fluidizing gas to chlorinate the titanium dioxide and produce titanium tetrachloride.
Titanium tetrachloride vapour is recovered from the exit gases. The superficial velocity imparted to the particles comprising the fluidized bed represents a substantial proportion of the terminal velocity of the mineral grains.
A process for chlorinating a fine grained mineral containing titanium dioxide in a fluidized bed comprising adding the fined grained mineral to a fluidized bed comprising a coarse grained material and a source of active carbon. A chlorinating agent is introduced into the fluidizing gas to chlorinate the titanium dioxide and produce titanium tetrachloride.
Titanium tetrachloride vapour is recovered from the exit gases. The superficial velocity imparted to the particles comprising the fluidized bed represents a substantial proportion of the terminal velocity of the mineral grains.
Description
20~1751.
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RECOVERY OF TITANIUM VALUES FROM MINERALS
This invention relates to a process for recovery of titanium values from minerals containing titanium dioxide.
Fluidised bed chlorination technology is well known for the manufacture of TiO2 pigment from naturally 10 occurring high titanium dioxide materials, and a range of synthetic high titanium dioxide substitutes derived from ilmenite. However, the known art is unsuitable for the treatment of fine grained titanium dioxide containing materials. As will be explained in more detail below, 15 attempts to treat fine grained titanium dioxide ; containing materials according to the prior art have :~
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: -failed due to excessive entrainment losses, and it is the common view that fine minerals cannot be retained within fluidised beds of conventional design for sufficient time to achieve the desired reaction.
S It is an object of the present invention to provide a process whereby titanium values may be recovered from fine grained titanium dioxide containing materials.
A further object is the recovery of titanium 10 values from fine titanium dioxide minerals bychlorination in fluidised beds operated at intensities similar to those used in the treatment of coarser minerals.
As indicated above, a major use of naturally ?5 occurring high titanium dioxide content materials, and a range of synthetic high titanium dioxide substitutes derived from ilmenite, is TiO2 pigment manufactured by the chloride process.
In the chloride process carbochlorination of 20 the titanium dioxide results in the formation of titanium tetrachloride vapour, which may be condensed and then purified by chemical means and distillation. Titanium tetrachloride produced in this manner is subsequently combusted with oxygen to yield pure TiO2 pigment and 25 recoverable chlorine.
Almost all Western chloride pigment producers now use fluidised bed chlorination technology, which latter has replaced fixed bed chlorinators requiring carbon bonded mineral briquette feeds.
The application of fluidised bed technology to chlorination, in which feed mineral is continually consumed, introduces a number of constraints on the feed ;
mineral properties, viz: ;
1. For a given chlorinator the production rate can 35 only be maintained at capacity, while obtaining good ~ ;
pigment recovery from the feed, if the fluidised bed . :. ,. .~
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2001~5 design suits the particle size distribution of the feed.
Feeds coarser than the design feed may require higher gas velocities (i.e. production rates) than the chlorinator is designed for in order to remain fluidised. Particles 5 of feed finer than designed for will be ejected from the fluidised beds and may constitute significant losses. ~ ~ ;
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RECOVERY OF TITANIUM VALUES FROM MINERALS
This invention relates to a process for recovery of titanium values from minerals containing titanium dioxide.
Fluidised bed chlorination technology is well known for the manufacture of TiO2 pigment from naturally 10 occurring high titanium dioxide materials, and a range of synthetic high titanium dioxide substitutes derived from ilmenite. However, the known art is unsuitable for the treatment of fine grained titanium dioxide containing materials. As will be explained in more detail below, 15 attempts to treat fine grained titanium dioxide ; containing materials according to the prior art have :~
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: -failed due to excessive entrainment losses, and it is the common view that fine minerals cannot be retained within fluidised beds of conventional design for sufficient time to achieve the desired reaction.
S It is an object of the present invention to provide a process whereby titanium values may be recovered from fine grained titanium dioxide containing materials.
A further object is the recovery of titanium 10 values from fine titanium dioxide minerals bychlorination in fluidised beds operated at intensities similar to those used in the treatment of coarser minerals.
As indicated above, a major use of naturally ?5 occurring high titanium dioxide content materials, and a range of synthetic high titanium dioxide substitutes derived from ilmenite, is TiO2 pigment manufactured by the chloride process.
In the chloride process carbochlorination of 20 the titanium dioxide results in the formation of titanium tetrachloride vapour, which may be condensed and then purified by chemical means and distillation. Titanium tetrachloride produced in this manner is subsequently combusted with oxygen to yield pure TiO2 pigment and 25 recoverable chlorine.
Almost all Western chloride pigment producers now use fluidised bed chlorination technology, which latter has replaced fixed bed chlorinators requiring carbon bonded mineral briquette feeds.
The application of fluidised bed technology to chlorination, in which feed mineral is continually consumed, introduces a number of constraints on the feed ;
mineral properties, viz: ;
1. For a given chlorinator the production rate can 35 only be maintained at capacity, while obtaining good ~ ;
pigment recovery from the feed, if the fluidised bed . :. ,. .~
,'' '',"":~
2001~5 design suits the particle size distribution of the feed.
Feeds coarser than the design feed may require higher gas velocities (i.e. production rates) than the chlorinator is designed for in order to remain fluidised. Particles 5 of feed finer than designed for will be ejected from the fluidised beds and may constitute significant losses. ~ ~ ;
2. Fluidised bed chlorinators currently in operation were originally designed to suit beach sand ~ ;
rutile feed, which normally has an average particle size 10 in the range 150 - 250 ,um. It is generally accepted that feeds with appreciable quantities (e.g. greater than 15%) of material in the -100 ~m size fraction are not acceptable for these chlorinators and will result in excessive losses due to gas entrainment.
15 3. Feeds must not produce even trace quantities of defluidizing liquid phases in chlorination. Phases which melt at chlorination temperatures and elemental inputs which chlorinate to liquid forming chlorides (e.g. alkali and alkali earth elements) must therefore be avoided.
This limitation is severe as liquids formed in chlorination tend to accumulate and will cause defluidization at levels as low as 0.3% of bed weight.
4. Feeds should not contain more than a small proportion ~e.g. about 1%) of material which is 25 relatively inert to chlorination, such as quartz. Inert material may build up in fluidised bed chlorinators to the point that production capacity is limited by bed composition.
There are other constraints on feeds to 30 chlorinators which are not fluidised bed operation dependent. For example, chlorine and coke consuming impurities, such as iron, represent an economic penalty on the chlorination process, especially where arrangements for disposal of the product chloride wastes , "
20017Sl : " 5 must be made. In general the value of a feed will be related to its titanium dioxide content, which should be in the range 85 - 96~ Tio2.
Typically mineral residence times in industrial 5 fluidised bed chlorinators are of the order of 5 to 10 hours. These long residence times are determined by the maximum superficial gas velocity, bed area, and a requirement that the chlorinating agent (normally gaseous chlorine) be fully utilized. This in turn determines bed 10 height and bed mineral content.
There is evidence in the technical literature that mineral reaction rates in chlorination are limited by fluidised bed chlorinator dynamics and carbon surface reactivities, rather than by limitations on the maximum 15 possible mineral reaction rate. Consequently reported laboratory studies have indicated mineral residence times for complete effective chlorination of from 8 seconds to 30 minutes, depending on conditions employed and the fineness of grind of the original mineral. It is agreed 20 however, that conditions corresponding to optimum mineral reaction rates cannot be achieved in industrial practice without unacceptable mineral or chlorinating agent losses.
In one prior art arrangement, U.S. Patent 25 4,440,730 (Bonsack), it was projected that the fluidised ;
bed chlorination treatment of conventionally sized (+200 ~m) rutile mineral could be carried out at mineral reaction rates of less than 30 minutes at 1000C if the usual petroleum coke reductant was replaced by brown coal 30 char. However, no attempt has been made to treat fine '~
mineral e.g. at -60 ,um) in such an arrangement, as it is the common view that fine minerals cannot be retained within fluidised beds of conventional design for sufficient time to allow substantial reaction.
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In another arrangement, U.S. Patent 4,442,076 (Bonsack), a variation of titanium dioxide bearing fine minerals including anatase, rutile and titaniferous slags (e.g. -50 ,um) was treated using brown coal char as 5 reductant, in what has been described as an "entrained flow chlorinator". In this arrangement mineral and char were introduced into the chlorine gas charged into the top of a vertical shaft which was maintained at a temperature above 1000C. The combination of fine 10 minerals and of a carbon source having a large, active surface area resulted in mineral reaction times of as low as eight seconds at acceptable recoveries. However, reservations about scale-up to industrial level under workable mineral/gas mixing conditions and at acceptable 15 residence times, have stopped further development of the concept.
Also disclosed in prior art processing, (USBM
Rep. of Invest. 8165, Harris et al, 1976), is a method for treatment of fine grained ilmenite mineral by 20 fluidised bed chlorination in which the fluidised bed consisted entirely of coke, with mineral passing vertically through the bed. In this case relatively fine grained coke was used in order to maintain a fluidised bed. The method was not adopted in practice due to the 25 concerns about excessive losses of fine coke by entrainment in product gases. Successful use of the process has not been demonstrated for less reactive j;~
minerals, such as rutile, which can be more economically treated in other ways.
There is currently little incentive for the redesign of existing fluidised bed chlorinators, since beach sand and other closely sized coarse feeds are still readily available, and are expected to represent the :
major feedstocks in future. However, there exist a 35 number of potential titanium dioxide feed sources ~
(including natural mineral, slag fines and chlorinator ~ ;
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blown over fines) which cannot readily be treated in "as received" form by known techniques in conventionally sized chlorinators due to their fine mineral grain size.
Thus there has been a hitherto unsatisfied need 5 for a process which will achieve high recoveries from fine mineral feeds without loss of productivity, preferably in chlorinators of close to conventional fluidised bed design. In developing the present invention a study of the modes of operation of such chlorinators 10 has been made with a view to achieving the following:
(i) Ensure mineral distribution across the entire reactor area;
(ii) Provide an environment such that virtually complete mineral chlorination occurs prior to lS delivery of mineral particles into the exit gas stream;
(iii) Allow sufficient gas/mineral contact and mass and heat transfer to ensure complete utilisation of chlorine within the reactor system.
These desiderata associated with the recovery ;
20 of titanium values from fine minerals, have not been met ~ ;
in prior art processing under industrially realistic conditions. It is an object of the present invention to overcome the difficulties associated with the treatment of fine minerals in chlorinators of close to conventional , . , 25 design. This refers particularly to high recoveries of mineral and chlorine values at efficiencies similar to those attainable in current practice with coarse mineral feeds.
Accordingly the present invention provides a 30 process for chlorinating fine grained natural or synthetic sources of titanium values which process ~;
comprises:
adding a fine grained material containing -. . .:.::
titanium dioxide to a fluidized bed comprising a coarse -~
35 grained material and a source of active carbon, the bed being fluidized by a fluidizing gas; introducing a ~
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, - 8 -chlorinating agent into the fluidizing gas to chlorinate titanium dioxide and produce titanium tetrachloride thereby and recovering titanium tetrachloride from exit gases leaving the fluidized bed wherein the fluidizing 5 gas imparts a superficial velocity to particles comprising the fluidized bed that represents a substantial proportion of the terminal velocity of the fine grained material.
The abovementioned superficial velocity may be 10 for example from 10 to 40 cm sec 1, which is similar to the fine grained titanium dioxide containing mineral terminal velocity at for example 20 to 60 cm sec 1, Mineral particle residues, preferably containing less than 15% of the originally contained 15 titanium dioxide, are removed from the fluidised bed by elutriation into exit gases, from which they may be separated subsequently.
Titanium sources may include such materials as ~, titanium concentrates (e.g. containing rutile, anatase ,.. ..
20 and leucoxene), titaniferous slag, titaniferous minerals ~
recovered from chlorinator wastes, and various products ; , derived from ilmenite known as synthetic rutile or ,, upgraded ilmenite, although the process of this invention , is not in any way restricted to these materials. "Fine 25 grained mineral" refers to titanium dioxide not acceptable in conventional fluidised bed chlorination ;
operations due to anticipated losses as fines. "Fine grained" is taken to mean having a size distribution such ;~
that more than 50% of the titanium values are in 30 particles less th,an lOO ~um in diameter.
In a preferred embodiment of the process, fine , ,~
mineral and an active carbon source are added to a bed of , coarse fluidised mineral and char at 1000C at a rate sufficient to provide for a stoichiometric proportion of 35 chlorinating agent in the fluidising gases. The superficial gas velocity in the fluidised bed is set to 200~75~
g values similar to those used in conventional industrial chlorinators, viz. approximately 20 cm sec 1 Contrary to expectations from the teachings of prior art it was found that under such circumstances recoveries of up to 5 65% of the titanium values in the feed as titanium tetrachloride could be achieved in a bed of only 30 cm in height. Since industrial chlorinators have bed heights 10 to 20 times greater than this, recoveries of greater than 90~ are projected for industrially sized 10 chlorinators.
High recoveries were achieved in mineral residence times as low as 30 seconds, calculated from steady state bed compositions, after continuously feeding -at a known rate for some hours.
lS Although we do not wish to be limited by an hypothetical or postulated mechanism for the observed beneficial effects of the process of the invention, it is believed that the provision of the bed of coarse fluidised mineral (for example, beach sand mineral in the ~i 20 size range 200 to 600 ,um) together with the active carbon ~
source, for example char, which has enabled treatment of ;;
finely particulate minerals without unacceptable mineral a~d char losses, may operate in the following manner. ~
It appears that the coarse mineral acts to ;~;
25 distribute fine mineral uniformly across the bed area, supports the char in the fluidised bed under conditions in which the char would normally not be fluidised, and provides good char/mineral mixing. Apparently it also has the effect of retarding transport of fine mineral 30 into the exit gas stream by ensuring a degree of ~-~
backmixing of fine solids and hence providing longer average residence times.
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We believe that the char support function of the coarse fluidised mineral is important in maintaining char losses at low levels. By allowing the feeding of coarser char the amount of char delivered to blown over 5 solids is reduced.
The use of an active car~on source is also an important feature of the invention. The principal aim in the treatment of fine minerals according to the invention is to accelerate mineral chlorination rates, for example 10 such that reaction half life (i.e. the time taken for the weight of an average sized fine mineral grain to be 50%
consumed by chlorination) is only a fraction of the time a particle remains within the reaction zone. Reaction half life is reduced by fineness of mineral grain size 15 and reactive surface area of the carbonaceous reductant.
A combination of the use of fine mineral and highly active carbon surface has resulted in particular examples of very short reaction half lives, of the order of ten seconds.
An advantage of the use of fluidised beds for ;
chlorination reactions lies in the ability to vary ;~
relative mineral to carbon ratios within the fluidised bed. It is possible to maintain a different ratio of mineral to carbon within the bed from that in the feed, 25 resulting in optimisation of reaction rate without compromise of feed ratios away from the optimum mass balance.
The chlorination reaction involves two discrete solid reagents, carbon and titanium dioxide (in mineral) 30 and a single gaseous;realgent (e.g. chlorine). For such reactions to proceed at reasonable rates gaseous ;
intermediates are very likely to be involved.
It is believed that activated species, such as active monatomic chlorine radicals, are involved in the 35 actual chlorination reaction, in a reaction sequence such as:
20017$~.
C12 (g) = 2Cl (adsorbed, carbon surface) Cl = Cl (g) (desorbed gaseous monatomic chlorine) TiO2 + (4-2x) Cl (g) = TiOX C14_2x + (1 x/2) 2 (g) . , , ,,. ~ .
/202 + CO (g) C2 (g) ' ' .
CO (g) + C = 2 CO (adsorbed, carbon surface) : . . ..., ~
CO = CO (g) (desorbed, gaseous) TiOX C14_2X + xCO (g) 4 ~;
While the above reaction sequence is not certain, there is evidence that carbon surfaces become - ;~;
directly involved in the acceleration of chlorination reactionR, even where an excess of other reductants such as carbon monoxide, is present.
According to the reaction sequence shown above the presence of a greater surface area of active carbon for the adsorption reactions, will provide faster reactions by increasing the rate of formation of the active chlorinating species. Where the rate of reaction 20 is not limited by the rate of formation of the active chlorinating species, such as is the case for a small ;~
amount of reacting mineral in a fluidised bed containing active carbon, the rate of reaction per unit surface of mineral will be greatest. Under these circumstances for , 25 a given fluidised bed the reaction half life will be the ;; , smallest possible fraction of the reaction zone retention '!' ~.''':'' time of the mineral, and recoveries of titanium values will be greatest.
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The coarse fluidised bed mineral, used for mineral distribution and char support, may be any suitable mineral. In particular, it may be a relatively chlorination inert mineral, such as beach sand quartz, or 5 a mineral which reacts in chlorination to produce valuable products, such as rutile, anatase, synthetic rutile or titaniferous slag.
Where an inert bed material is used, a small amount of bed material, up to several percent by weight -10 of the titanium bearing feeds, will be required to be fed into the reactor. This bed makeup accounts for losses by attritioning of the bed and unselective chlorination ;
reactions. Sized blown over bed material will be returned to the bed with the bed makeup mineral. It has 15 been found that beach sand quartz represents a very suitable coarse bed mineral due to its ideal fluidisation properties, its ready availability and its low cost.
Where a reactive coarse bed mineral is to be used it is necessary to operate with a sufficient 20 supplementary feed of coarse mineral in order to maintain bed fluidisatioh. Beach sand rutile (at 250 ,um average particle size, for example) would form an advantageous supplementary feed material.
A suitable carbonaceous reducing agent for use 25 in the disclosed process is char derived from Victorian brown coal. This char typically has a surface area of some lOOm2/g and is ideally suited for use according to the manner described. A char in the size range 0.5 mm -4.0 mm, with an average particle size of approximately 2 30 mm, is particularly suitable. Carbon sources such as petroleum coke and anthracite char, typically having surface areas of lm2/g which are normally used in chlorination, will not have the same advantageous effect.
However, such carbon sources can be applied to the 35 present process, provided somewhat higher carbon contents ~ ;
and deeper beds are used to ensure complete reaction. ~ -~
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The fluidisation and mixing characteristics of coarse mineral and char dictate that the char component of the bed material should not exceed approximately 75~
of the bed weight at superficial fluidising velocities of 5 20 - 30 cm sec 1 However, bed carbon losses will be greatest and fine mineral/char mixing will be poorest at high proportions of char in the fluid bed. For high surface area carbon sources, such as Victorian brown coal char,it has been found to be advantageous to operate the 10 process at bed char contents of less than 40% of the bed -~
weight. Nevertheless, the char content of the bed is a ~ ;
variable which may be altered within wide ranges, ~ ;
depending on fluidised bed dimensions. ;
The fluidised bed chlorination process as 15 disclosed herein may be carried out in any suitable reactor. In a typical embodiment char and bed mineral are metered separately into the top of the fluidised bed, with char additions determined by chloxine input rates and bed mineral additions determined by bed pressure 20 drops. Fine titaniferous feed may be metered either into the top of the fluidised bed directly, or for very fine feeds, by injection through pneumatic feed injectors beneath the surface of the fluidised bed. Feed injectors ~
may pass into the bed from above or through the ~ ;
25 distributor plate from below. ~ ~
Best advantage may be taken of bed mixing ~ ;
conditions with feed injection from above, although éither method may be used to provide adequate mixing in a ;
carefully considered design. The injecting gas may be 30 either a chlorinating agent, inert gas or air. Fine mineral feed metering is controlled according to monitored chlorine and mineral losses in exit gases, with the intention of maximising chlorine consumption by fine mineral and minimising chlorine consumption by bed 35 mineral. Typically the system will be operated with 5 -10% losses of mineral to exit gases.
The preferred chlorinating agent is chlorine gas, although other chlorinating agents such as ferric chloride (injected as solid or vapour), phosgene and carbon tetrachloride are suitable for bringing about 5 chlorination. In practice chlorine gas is useful in enabling regeneration from titanium tetrachloride and in avoiding any input of non-chlorinating diluents.
An additional advantage of the use of the described system relates to an observed behaviour of 10 titaniferous feeds containing relatively inert impurity phases, such as quartz and zircon. Where a fine grained mineral is contaminated with such impurities, for example, in siliceous leucoxene, good recoveries will be obtained in chlorination of titanium values but inerts by 15 virtue Gf their fine grained nature, will be swept from the reactor with the exit gases. Conventional reactors which have been designed for the treatment of coarse minerals normally require suspension of operations to allow removal of built up inert phases in the 20 chlorinator In conventionally operated reactors inert phases result in loss of chlorination intensity due to bed dilution. By operating the present system the addition of inerts with feeds has the effect of either 25 reducing inerts makeup requirements or elutriating inert fines from the reactor system, neither of which is harmful to continuous operations In some circumstances coarse titaniferous minerals contaminated with inerts may be beneficially treated by preliminary grinding prior to 30 treatment to provide fines input.
There is no implied limitation in the invention described to fine minerals with a particular size distribution. The process' main advantage is in allowing the treatment of titaniferous feeds of any size 35 distribution, with excellent recoveries. For example, beneficiates from grinding/mineral processing circuits or ;
. ~. " ' ""'''..,:' 200~751 titaniferous slag milling products may be treated whereas up till now at least some proportion of such materials ;
could not be treated in fluidised bed chlorinators.
Brief Description of the Drawings S The accompanying drawing, Figure 1, illustrates ;
a reactor of the type employed in the examples below.
Figure 1 is a side elevation partially in cross-section of a fluid bed reactor 1 comprising a fluidised bed 2 contained in a cylindrical housing 3.
10 The reactor has a feed tube 4 for feeding reactants and fluid bed components into the reactor. A sintered distributor 5 is located near the base 6 of the reactor.
The reactor has an inlet 7 in its base 6 for feeding gaseous chlorinating agents into the reactor and an 15 outlet 8 for removing gaseous products.
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Examples i The following non-limiting examples illustrate preferred embodiments of the invention. Table 5 provides a summary of the examples.
20 Example 1 i Chlorination was performed in a 75 ~ internal diameter fused quartz reactor having a porous sintered quartz distributor plate. The constant temperature heated length of the quartz reactor was 50 cm at 1000C.
25 Heating was provided by use of an electrical resistance furnace. This type of reactor is schematically illustrated in Figure 1.
In all cases a starting bed of carbon and coarse mineral 25 cm in height (approximately 1.2 kg in 30 weight at 40% carbon) was charged into the reactor.
Chlorine was fed into the base of the reactor to provide a superficial gas velocity of 22 cm sec 1, upon which the bed became fluidised. Fine rutile mineral, sized to ZO~)~7~i~
between 50 and 100 ~m was fed into the bed at a rate equivalent to the chlorine addition rate for stoichiometric conversion of mineral to chlorides. Sized char or coke was added at a consumption rate calculated 5 from measured chlorine, carbon monoxide and carbon dioxide contents in exit gases and known chlorine input rates.
Exit gases were cleaned of solids in a heated drop out box and cyclone maintained at a temperature of 10 150~C. Solids exiting with gases accounted for all mineral losses. Water cooled and ethylene glycol refrigerant chilled condensers were used to condense liquid titanium tetrachloride. Gases were scubbed in 7 sodium carbonate solution and exhausted to atmosphere.
The method of operation was to feed the fluidised bed at steady state for one to two hours at a continuous fine mineral feed rate of 30 grams per minute.
At the end of this time the chlorine content of the exit gases was monitored, the titanium tetrachloride 20 production rate was measured and the gas and solid inputs were stopped.
The bed solids were allowed to cool under a light nitrogen flow and then removed from the bed. The weight percent of titanium bearing minerals in the final 25 bed was determined by chemical analysis. The fine mineral residence time could then be determined according to:
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26~0175~ . :
, - 17 -r =60 x weight mineral in bed (seconds) fine mineral fe3ed rate (per min) The performance of the described system using 5 petroleum coke as the carbon source was determined. Fine ' rutile feed and petroleum coke particle size distributions are provided in Tables 1 and 2. The initial coarse bed mineral (beach sand quartz) was sized to lie in the range 200-500 ym and the bed was composed , 10 of 40% petroleum coke and 60% mineral. Recovery of ', ;' ' titanium values in titanium tetrachloride was about 65~ ' ,'','' in this case, but in long residence times (eg. 172 ;' ~ ' seconds).
The recovery achieved in this case is 15 consistent with expected elutriation of mineral from the reactor upon chlorination to a size (approximately 43 um) having the superficial velocity (22 cm sec 1) as its terminal velocity.
Example 2 Here Victorian brown coal char of particle size distribution recorded'in Table 3, was substituted for petroleum coke and titanium value recovery remained at 65~. Fine mineral residence time was reduced to about 30 seconds in this case. Clearly the substitution of char ~, 25 for petroleum coke has dramatically reduced the titania , ,' reaction time, as measured by the shorter residence time ,, ,, required to reduce particle diameter to a size having the superfici,al velocity as,the particle terminal velocity. '~ '~
Example 3 (,~"
This test was conducted in identical manner to '~
that of Example 2 with the exception that a finer grained titaniferous feedstock (see Table 4) was used in place of '~
the previous feed. Titanium value recovery in this case ~ ,,;
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was only 43%. However, this level of recovery was achieved in a residence time of only approximately 14 seconds. Further, since the feed mineral size was such to allow immediate transport with reactor exit gasses, it 5 is evident that the bed formulation has the effect of ensuring sufficient mineral hold-up to allow a significant degree of reaction to take place. For practically sized industrial chlorinators an equivalent degree of mineral retention at similar reaction rates 10 will ensure virtually complete mineral chlorination before fine particles leave with reactor exit gases.
Example 4 A series of tests was conducted for which a 1:1 ratio of beach sand rutile feed to fine rutile feed was 15 used to make up a mineral feed rate of 33 g/min. The beach sane rutile was sized to lie within the range 150-212 ~m, while the fine rutile feed size distribution is provided in Table 1. Further, 50% of the coarse quartz used in the starting bed of previous examples was 20 replaced with the sized beach sand rutile. Conditions were otherwise identical to those of Example 2.
It was possible to separately estimate ;~
residence times for coarse and fine minerals from the ; ~ ;
final bed composition and the particle size distribution 25 of the titanium minerals in the bed at the end of the 50 minute test. Coarse mineral residence time was 25 ;
seconds at greater than 90% recovery of coarse mineral titania to titanium tetrachloride while fine mineral residence time was 6.1 seconds at approximately 41%
30 recovery. It is postulated that a lower proportion of coarse rutile in the original bed and in the feed would have resulted in higher recovery from the fine rutile due to competition from the coarse mineral surfaces for ;
chlorine, which was 100% utilised in this trial.
. ,',. ' ,: .:, ~, . ..
20~)~75~
This example has further demonstrated the ability of the system disclosed herein, involving the use of a bed of coarse mineral and active carbon fluidised Dy chlorination gases, to effect recovery of titania from -5 fine particle feeds. In addition, the ability to simultaneously recover titanium values from feeds .
containing both coarse and fine particles wherein the : ..
coarse mineral component of the fluidised bed is at least : :
partially composed of coarse titania bearing 10 mineralisation has been demonstrated.
, 2001~51.
- 20 ~
Table 1 : Size Distribution of Fine Futile Feed (Examples 1, 2, 4) -Size Range (~m)Wt ~
+106 0.52 -106 + 90 11.37 - 90 + 75 31.78 - 75 + 63 33.28 - 63 + 53 13.13 - 53 9.92 ,~
10 Table 2 : Size Distribution of Petroleum Coke*
(Example 1) Size Range (~m)Wt %
-2000 + 1000 50 -1000 + 500 50 .,:
15 * synthetically sized mixture.
Table 3 : Size Distribution of Victorian Brown Coal Char*
Size Range (~m)Wt % :
-2000 + 1000 50 -1000 + 500 50 20 * synthetically sized mixture.
':
.
20017~
, :;;.,.:.
Table 4 : Size Distribution of Fine Futile Rutile Feed (Example 3) Size Range (~m) Wt %
+53 9.5 -53 + 45 29.9 -45 + 38 41.7 -38 18.9 ~, ~,""
- ~.
,~
. -, .-, ,, .., .~,.....
" ~
'' .'`'"'''''''' ' ," "','.', "'",,~
I . , ' ~, .:
~. '",' ~, : ' '~
2001751.
Table 5 : Summary of Trials in Examples 1 to 4 Test Example 1 Example 2 Example 3 Example 4 Reductant Petroleum Victorian Victorian Victorian Coke brown coal brown coal brown coal S char char char Initial bed weight (g) 1200 1200 1200 1400 Carbon in initial bed (g) 500 500 500 500 ", 10 Coarse rutile in initial bed (g) - - _ 400 Titania Mineral addition rate (g/min) 30 37.1 32 16.5 coarse 16.5 fine 15 50% passing aperture for mineral ~ -~
feed (ym) 70 70 43 184 coarse 70 fine .: , Chlorine addition 20 rate (Nl/min) 11.4 12.8 11.4 11.4 CO/CO2 at steady rate 0.78 50.0 6.0 80.0 : ' . ' ~;
.
,, . ~ i ~ . .. .. . . . . . ..
Z001'75~
"' Coke addition rate (g/min) 5.0 4.8 7.1 7.6 Final bed weight (g) 12431000 1258 1331 % titania mineral 5 in final bed 6.9 1.8 0.60 32.2 % titania recovery 65 65 43 69 Chlorine utilisation % 9o 9o 7s 9 .
Titania mineral 10 residence time(secs) 172 29.1 14.1 25.0 coarse 6.1 fine Fine mineral recovery/
residence time %/sec 0.382.2 3.0 7.1 , ;, . ...
' ; .;; '"
~ ;''' `
zoo~sl. , , ' .
Table 6 : Composition of Rutile Feeds wt %
Ti 57.1 :
Fe 1.60 ;~
Si 0-33 ~ ~ -Al 0.32 Cr 0.10 Mg 0.01 V 0.34 Mn 0.04 ~~
Zr 0.67 : :
Ca 0.01 ; ~ ~
,, ; ~.
Table 7 ~ osition of Carbon Reductants (%) Fixed C S Ash Volatiles 15 Pet.coke 98.7 3.6 0.4 0.6 ~rown coal char 93.5 0-3 3.0 3.5 '' '",'," '; ,', ; ,`"''"'~;'', "' " ' ', ', .. '' ',: "~' .
rutile feed, which normally has an average particle size 10 in the range 150 - 250 ,um. It is generally accepted that feeds with appreciable quantities (e.g. greater than 15%) of material in the -100 ~m size fraction are not acceptable for these chlorinators and will result in excessive losses due to gas entrainment.
15 3. Feeds must not produce even trace quantities of defluidizing liquid phases in chlorination. Phases which melt at chlorination temperatures and elemental inputs which chlorinate to liquid forming chlorides (e.g. alkali and alkali earth elements) must therefore be avoided.
This limitation is severe as liquids formed in chlorination tend to accumulate and will cause defluidization at levels as low as 0.3% of bed weight.
4. Feeds should not contain more than a small proportion ~e.g. about 1%) of material which is 25 relatively inert to chlorination, such as quartz. Inert material may build up in fluidised bed chlorinators to the point that production capacity is limited by bed composition.
There are other constraints on feeds to 30 chlorinators which are not fluidised bed operation dependent. For example, chlorine and coke consuming impurities, such as iron, represent an economic penalty on the chlorination process, especially where arrangements for disposal of the product chloride wastes , "
20017Sl : " 5 must be made. In general the value of a feed will be related to its titanium dioxide content, which should be in the range 85 - 96~ Tio2.
Typically mineral residence times in industrial 5 fluidised bed chlorinators are of the order of 5 to 10 hours. These long residence times are determined by the maximum superficial gas velocity, bed area, and a requirement that the chlorinating agent (normally gaseous chlorine) be fully utilized. This in turn determines bed 10 height and bed mineral content.
There is evidence in the technical literature that mineral reaction rates in chlorination are limited by fluidised bed chlorinator dynamics and carbon surface reactivities, rather than by limitations on the maximum 15 possible mineral reaction rate. Consequently reported laboratory studies have indicated mineral residence times for complete effective chlorination of from 8 seconds to 30 minutes, depending on conditions employed and the fineness of grind of the original mineral. It is agreed 20 however, that conditions corresponding to optimum mineral reaction rates cannot be achieved in industrial practice without unacceptable mineral or chlorinating agent losses.
In one prior art arrangement, U.S. Patent 25 4,440,730 (Bonsack), it was projected that the fluidised ;
bed chlorination treatment of conventionally sized (+200 ~m) rutile mineral could be carried out at mineral reaction rates of less than 30 minutes at 1000C if the usual petroleum coke reductant was replaced by brown coal 30 char. However, no attempt has been made to treat fine '~
mineral e.g. at -60 ,um) in such an arrangement, as it is the common view that fine minerals cannot be retained within fluidised beds of conventional design for sufficient time to allow substantial reaction.
~' ' ";;' ,.. .
'' " :-, , :, 2001~5~
In another arrangement, U.S. Patent 4,442,076 (Bonsack), a variation of titanium dioxide bearing fine minerals including anatase, rutile and titaniferous slags (e.g. -50 ,um) was treated using brown coal char as 5 reductant, in what has been described as an "entrained flow chlorinator". In this arrangement mineral and char were introduced into the chlorine gas charged into the top of a vertical shaft which was maintained at a temperature above 1000C. The combination of fine 10 minerals and of a carbon source having a large, active surface area resulted in mineral reaction times of as low as eight seconds at acceptable recoveries. However, reservations about scale-up to industrial level under workable mineral/gas mixing conditions and at acceptable 15 residence times, have stopped further development of the concept.
Also disclosed in prior art processing, (USBM
Rep. of Invest. 8165, Harris et al, 1976), is a method for treatment of fine grained ilmenite mineral by 20 fluidised bed chlorination in which the fluidised bed consisted entirely of coke, with mineral passing vertically through the bed. In this case relatively fine grained coke was used in order to maintain a fluidised bed. The method was not adopted in practice due to the 25 concerns about excessive losses of fine coke by entrainment in product gases. Successful use of the process has not been demonstrated for less reactive j;~
minerals, such as rutile, which can be more economically treated in other ways.
There is currently little incentive for the redesign of existing fluidised bed chlorinators, since beach sand and other closely sized coarse feeds are still readily available, and are expected to represent the :
major feedstocks in future. However, there exist a 35 number of potential titanium dioxide feed sources ~
(including natural mineral, slag fines and chlorinator ~ ;
200~51.
, . .
blown over fines) which cannot readily be treated in "as received" form by known techniques in conventionally sized chlorinators due to their fine mineral grain size.
Thus there has been a hitherto unsatisfied need 5 for a process which will achieve high recoveries from fine mineral feeds without loss of productivity, preferably in chlorinators of close to conventional fluidised bed design. In developing the present invention a study of the modes of operation of such chlorinators 10 has been made with a view to achieving the following:
(i) Ensure mineral distribution across the entire reactor area;
(ii) Provide an environment such that virtually complete mineral chlorination occurs prior to lS delivery of mineral particles into the exit gas stream;
(iii) Allow sufficient gas/mineral contact and mass and heat transfer to ensure complete utilisation of chlorine within the reactor system.
These desiderata associated with the recovery ;
20 of titanium values from fine minerals, have not been met ~ ;
in prior art processing under industrially realistic conditions. It is an object of the present invention to overcome the difficulties associated with the treatment of fine minerals in chlorinators of close to conventional , . , 25 design. This refers particularly to high recoveries of mineral and chlorine values at efficiencies similar to those attainable in current practice with coarse mineral feeds.
Accordingly the present invention provides a 30 process for chlorinating fine grained natural or synthetic sources of titanium values which process ~;
comprises:
adding a fine grained material containing -. . .:.::
titanium dioxide to a fluidized bed comprising a coarse -~
35 grained material and a source of active carbon, the bed being fluidized by a fluidizing gas; introducing a ~
. .,: ,, .. :;"...:
. . ::. :,,~
Z001~7S~
, - 8 -chlorinating agent into the fluidizing gas to chlorinate titanium dioxide and produce titanium tetrachloride thereby and recovering titanium tetrachloride from exit gases leaving the fluidized bed wherein the fluidizing 5 gas imparts a superficial velocity to particles comprising the fluidized bed that represents a substantial proportion of the terminal velocity of the fine grained material.
The abovementioned superficial velocity may be 10 for example from 10 to 40 cm sec 1, which is similar to the fine grained titanium dioxide containing mineral terminal velocity at for example 20 to 60 cm sec 1, Mineral particle residues, preferably containing less than 15% of the originally contained 15 titanium dioxide, are removed from the fluidised bed by elutriation into exit gases, from which they may be separated subsequently.
Titanium sources may include such materials as ~, titanium concentrates (e.g. containing rutile, anatase ,.. ..
20 and leucoxene), titaniferous slag, titaniferous minerals ~
recovered from chlorinator wastes, and various products ; , derived from ilmenite known as synthetic rutile or ,, upgraded ilmenite, although the process of this invention , is not in any way restricted to these materials. "Fine 25 grained mineral" refers to titanium dioxide not acceptable in conventional fluidised bed chlorination ;
operations due to anticipated losses as fines. "Fine grained" is taken to mean having a size distribution such ;~
that more than 50% of the titanium values are in 30 particles less th,an lOO ~um in diameter.
In a preferred embodiment of the process, fine , ,~
mineral and an active carbon source are added to a bed of , coarse fluidised mineral and char at 1000C at a rate sufficient to provide for a stoichiometric proportion of 35 chlorinating agent in the fluidising gases. The superficial gas velocity in the fluidised bed is set to 200~75~
g values similar to those used in conventional industrial chlorinators, viz. approximately 20 cm sec 1 Contrary to expectations from the teachings of prior art it was found that under such circumstances recoveries of up to 5 65% of the titanium values in the feed as titanium tetrachloride could be achieved in a bed of only 30 cm in height. Since industrial chlorinators have bed heights 10 to 20 times greater than this, recoveries of greater than 90~ are projected for industrially sized 10 chlorinators.
High recoveries were achieved in mineral residence times as low as 30 seconds, calculated from steady state bed compositions, after continuously feeding -at a known rate for some hours.
lS Although we do not wish to be limited by an hypothetical or postulated mechanism for the observed beneficial effects of the process of the invention, it is believed that the provision of the bed of coarse fluidised mineral (for example, beach sand mineral in the ~i 20 size range 200 to 600 ,um) together with the active carbon ~
source, for example char, which has enabled treatment of ;;
finely particulate minerals without unacceptable mineral a~d char losses, may operate in the following manner. ~
It appears that the coarse mineral acts to ;~;
25 distribute fine mineral uniformly across the bed area, supports the char in the fluidised bed under conditions in which the char would normally not be fluidised, and provides good char/mineral mixing. Apparently it also has the effect of retarding transport of fine mineral 30 into the exit gas stream by ensuring a degree of ~-~
backmixing of fine solids and hence providing longer average residence times.
, , : . , . . ":", 20017S~
We believe that the char support function of the coarse fluidised mineral is important in maintaining char losses at low levels. By allowing the feeding of coarser char the amount of char delivered to blown over 5 solids is reduced.
The use of an active car~on source is also an important feature of the invention. The principal aim in the treatment of fine minerals according to the invention is to accelerate mineral chlorination rates, for example 10 such that reaction half life (i.e. the time taken for the weight of an average sized fine mineral grain to be 50%
consumed by chlorination) is only a fraction of the time a particle remains within the reaction zone. Reaction half life is reduced by fineness of mineral grain size 15 and reactive surface area of the carbonaceous reductant.
A combination of the use of fine mineral and highly active carbon surface has resulted in particular examples of very short reaction half lives, of the order of ten seconds.
An advantage of the use of fluidised beds for ;
chlorination reactions lies in the ability to vary ;~
relative mineral to carbon ratios within the fluidised bed. It is possible to maintain a different ratio of mineral to carbon within the bed from that in the feed, 25 resulting in optimisation of reaction rate without compromise of feed ratios away from the optimum mass balance.
The chlorination reaction involves two discrete solid reagents, carbon and titanium dioxide (in mineral) 30 and a single gaseous;realgent (e.g. chlorine). For such reactions to proceed at reasonable rates gaseous ;
intermediates are very likely to be involved.
It is believed that activated species, such as active monatomic chlorine radicals, are involved in the 35 actual chlorination reaction, in a reaction sequence such as:
20017$~.
C12 (g) = 2Cl (adsorbed, carbon surface) Cl = Cl (g) (desorbed gaseous monatomic chlorine) TiO2 + (4-2x) Cl (g) = TiOX C14_2x + (1 x/2) 2 (g) . , , ,,. ~ .
/202 + CO (g) C2 (g) ' ' .
CO (g) + C = 2 CO (adsorbed, carbon surface) : . . ..., ~
CO = CO (g) (desorbed, gaseous) TiOX C14_2X + xCO (g) 4 ~;
While the above reaction sequence is not certain, there is evidence that carbon surfaces become - ;~;
directly involved in the acceleration of chlorination reactionR, even where an excess of other reductants such as carbon monoxide, is present.
According to the reaction sequence shown above the presence of a greater surface area of active carbon for the adsorption reactions, will provide faster reactions by increasing the rate of formation of the active chlorinating species. Where the rate of reaction 20 is not limited by the rate of formation of the active chlorinating species, such as is the case for a small ;~
amount of reacting mineral in a fluidised bed containing active carbon, the rate of reaction per unit surface of mineral will be greatest. Under these circumstances for , 25 a given fluidised bed the reaction half life will be the ;; , smallest possible fraction of the reaction zone retention '!' ~.''':'' time of the mineral, and recoveries of titanium values will be greatest.
. . ~
Z00~75~
The coarse fluidised bed mineral, used for mineral distribution and char support, may be any suitable mineral. In particular, it may be a relatively chlorination inert mineral, such as beach sand quartz, or 5 a mineral which reacts in chlorination to produce valuable products, such as rutile, anatase, synthetic rutile or titaniferous slag.
Where an inert bed material is used, a small amount of bed material, up to several percent by weight -10 of the titanium bearing feeds, will be required to be fed into the reactor. This bed makeup accounts for losses by attritioning of the bed and unselective chlorination ;
reactions. Sized blown over bed material will be returned to the bed with the bed makeup mineral. It has 15 been found that beach sand quartz represents a very suitable coarse bed mineral due to its ideal fluidisation properties, its ready availability and its low cost.
Where a reactive coarse bed mineral is to be used it is necessary to operate with a sufficient 20 supplementary feed of coarse mineral in order to maintain bed fluidisatioh. Beach sand rutile (at 250 ,um average particle size, for example) would form an advantageous supplementary feed material.
A suitable carbonaceous reducing agent for use 25 in the disclosed process is char derived from Victorian brown coal. This char typically has a surface area of some lOOm2/g and is ideally suited for use according to the manner described. A char in the size range 0.5 mm -4.0 mm, with an average particle size of approximately 2 30 mm, is particularly suitable. Carbon sources such as petroleum coke and anthracite char, typically having surface areas of lm2/g which are normally used in chlorination, will not have the same advantageous effect.
However, such carbon sources can be applied to the 35 present process, provided somewhat higher carbon contents ~ ;
and deeper beds are used to ensure complete reaction. ~ -~
,'' ~' '" '' 200175~.
The fluidisation and mixing characteristics of coarse mineral and char dictate that the char component of the bed material should not exceed approximately 75~
of the bed weight at superficial fluidising velocities of 5 20 - 30 cm sec 1 However, bed carbon losses will be greatest and fine mineral/char mixing will be poorest at high proportions of char in the fluid bed. For high surface area carbon sources, such as Victorian brown coal char,it has been found to be advantageous to operate the 10 process at bed char contents of less than 40% of the bed -~
weight. Nevertheless, the char content of the bed is a ~ ;
variable which may be altered within wide ranges, ~ ;
depending on fluidised bed dimensions. ;
The fluidised bed chlorination process as 15 disclosed herein may be carried out in any suitable reactor. In a typical embodiment char and bed mineral are metered separately into the top of the fluidised bed, with char additions determined by chloxine input rates and bed mineral additions determined by bed pressure 20 drops. Fine titaniferous feed may be metered either into the top of the fluidised bed directly, or for very fine feeds, by injection through pneumatic feed injectors beneath the surface of the fluidised bed. Feed injectors ~
may pass into the bed from above or through the ~ ;
25 distributor plate from below. ~ ~
Best advantage may be taken of bed mixing ~ ;
conditions with feed injection from above, although éither method may be used to provide adequate mixing in a ;
carefully considered design. The injecting gas may be 30 either a chlorinating agent, inert gas or air. Fine mineral feed metering is controlled according to monitored chlorine and mineral losses in exit gases, with the intention of maximising chlorine consumption by fine mineral and minimising chlorine consumption by bed 35 mineral. Typically the system will be operated with 5 -10% losses of mineral to exit gases.
The preferred chlorinating agent is chlorine gas, although other chlorinating agents such as ferric chloride (injected as solid or vapour), phosgene and carbon tetrachloride are suitable for bringing about 5 chlorination. In practice chlorine gas is useful in enabling regeneration from titanium tetrachloride and in avoiding any input of non-chlorinating diluents.
An additional advantage of the use of the described system relates to an observed behaviour of 10 titaniferous feeds containing relatively inert impurity phases, such as quartz and zircon. Where a fine grained mineral is contaminated with such impurities, for example, in siliceous leucoxene, good recoveries will be obtained in chlorination of titanium values but inerts by 15 virtue Gf their fine grained nature, will be swept from the reactor with the exit gases. Conventional reactors which have been designed for the treatment of coarse minerals normally require suspension of operations to allow removal of built up inert phases in the 20 chlorinator In conventionally operated reactors inert phases result in loss of chlorination intensity due to bed dilution. By operating the present system the addition of inerts with feeds has the effect of either 25 reducing inerts makeup requirements or elutriating inert fines from the reactor system, neither of which is harmful to continuous operations In some circumstances coarse titaniferous minerals contaminated with inerts may be beneficially treated by preliminary grinding prior to 30 treatment to provide fines input.
There is no implied limitation in the invention described to fine minerals with a particular size distribution. The process' main advantage is in allowing the treatment of titaniferous feeds of any size 35 distribution, with excellent recoveries. For example, beneficiates from grinding/mineral processing circuits or ;
. ~. " ' ""'''..,:' 200~751 titaniferous slag milling products may be treated whereas up till now at least some proportion of such materials ;
could not be treated in fluidised bed chlorinators.
Brief Description of the Drawings S The accompanying drawing, Figure 1, illustrates ;
a reactor of the type employed in the examples below.
Figure 1 is a side elevation partially in cross-section of a fluid bed reactor 1 comprising a fluidised bed 2 contained in a cylindrical housing 3.
10 The reactor has a feed tube 4 for feeding reactants and fluid bed components into the reactor. A sintered distributor 5 is located near the base 6 of the reactor.
The reactor has an inlet 7 in its base 6 for feeding gaseous chlorinating agents into the reactor and an 15 outlet 8 for removing gaseous products.
.' ,', .;:",, ~,"
Examples i The following non-limiting examples illustrate preferred embodiments of the invention. Table 5 provides a summary of the examples.
20 Example 1 i Chlorination was performed in a 75 ~ internal diameter fused quartz reactor having a porous sintered quartz distributor plate. The constant temperature heated length of the quartz reactor was 50 cm at 1000C.
25 Heating was provided by use of an electrical resistance furnace. This type of reactor is schematically illustrated in Figure 1.
In all cases a starting bed of carbon and coarse mineral 25 cm in height (approximately 1.2 kg in 30 weight at 40% carbon) was charged into the reactor.
Chlorine was fed into the base of the reactor to provide a superficial gas velocity of 22 cm sec 1, upon which the bed became fluidised. Fine rutile mineral, sized to ZO~)~7~i~
between 50 and 100 ~m was fed into the bed at a rate equivalent to the chlorine addition rate for stoichiometric conversion of mineral to chlorides. Sized char or coke was added at a consumption rate calculated 5 from measured chlorine, carbon monoxide and carbon dioxide contents in exit gases and known chlorine input rates.
Exit gases were cleaned of solids in a heated drop out box and cyclone maintained at a temperature of 10 150~C. Solids exiting with gases accounted for all mineral losses. Water cooled and ethylene glycol refrigerant chilled condensers were used to condense liquid titanium tetrachloride. Gases were scubbed in 7 sodium carbonate solution and exhausted to atmosphere.
The method of operation was to feed the fluidised bed at steady state for one to two hours at a continuous fine mineral feed rate of 30 grams per minute.
At the end of this time the chlorine content of the exit gases was monitored, the titanium tetrachloride 20 production rate was measured and the gas and solid inputs were stopped.
The bed solids were allowed to cool under a light nitrogen flow and then removed from the bed. The weight percent of titanium bearing minerals in the final 25 bed was determined by chemical analysis. The fine mineral residence time could then be determined according to:
.~
: ;~, .''",.,:
26~0175~ . :
, - 17 -r =60 x weight mineral in bed (seconds) fine mineral fe3ed rate (per min) The performance of the described system using 5 petroleum coke as the carbon source was determined. Fine ' rutile feed and petroleum coke particle size distributions are provided in Tables 1 and 2. The initial coarse bed mineral (beach sand quartz) was sized to lie in the range 200-500 ym and the bed was composed , 10 of 40% petroleum coke and 60% mineral. Recovery of ', ;' ' titanium values in titanium tetrachloride was about 65~ ' ,'','' in this case, but in long residence times (eg. 172 ;' ~ ' seconds).
The recovery achieved in this case is 15 consistent with expected elutriation of mineral from the reactor upon chlorination to a size (approximately 43 um) having the superficial velocity (22 cm sec 1) as its terminal velocity.
Example 2 Here Victorian brown coal char of particle size distribution recorded'in Table 3, was substituted for petroleum coke and titanium value recovery remained at 65~. Fine mineral residence time was reduced to about 30 seconds in this case. Clearly the substitution of char ~, 25 for petroleum coke has dramatically reduced the titania , ,' reaction time, as measured by the shorter residence time ,, ,, required to reduce particle diameter to a size having the superfici,al velocity as,the particle terminal velocity. '~ '~
Example 3 (,~"
This test was conducted in identical manner to '~
that of Example 2 with the exception that a finer grained titaniferous feedstock (see Table 4) was used in place of '~
the previous feed. Titanium value recovery in this case ~ ,,;
' ~, ~ ,.. ..
. . ,~ ;,;; .
'' ~''",.' ~;
Z001~51.
was only 43%. However, this level of recovery was achieved in a residence time of only approximately 14 seconds. Further, since the feed mineral size was such to allow immediate transport with reactor exit gasses, it 5 is evident that the bed formulation has the effect of ensuring sufficient mineral hold-up to allow a significant degree of reaction to take place. For practically sized industrial chlorinators an equivalent degree of mineral retention at similar reaction rates 10 will ensure virtually complete mineral chlorination before fine particles leave with reactor exit gases.
Example 4 A series of tests was conducted for which a 1:1 ratio of beach sand rutile feed to fine rutile feed was 15 used to make up a mineral feed rate of 33 g/min. The beach sane rutile was sized to lie within the range 150-212 ~m, while the fine rutile feed size distribution is provided in Table 1. Further, 50% of the coarse quartz used in the starting bed of previous examples was 20 replaced with the sized beach sand rutile. Conditions were otherwise identical to those of Example 2.
It was possible to separately estimate ;~
residence times for coarse and fine minerals from the ; ~ ;
final bed composition and the particle size distribution 25 of the titanium minerals in the bed at the end of the 50 minute test. Coarse mineral residence time was 25 ;
seconds at greater than 90% recovery of coarse mineral titania to titanium tetrachloride while fine mineral residence time was 6.1 seconds at approximately 41%
30 recovery. It is postulated that a lower proportion of coarse rutile in the original bed and in the feed would have resulted in higher recovery from the fine rutile due to competition from the coarse mineral surfaces for ;
chlorine, which was 100% utilised in this trial.
. ,',. ' ,: .:, ~, . ..
20~)~75~
This example has further demonstrated the ability of the system disclosed herein, involving the use of a bed of coarse mineral and active carbon fluidised Dy chlorination gases, to effect recovery of titania from -5 fine particle feeds. In addition, the ability to simultaneously recover titanium values from feeds .
containing both coarse and fine particles wherein the : ..
coarse mineral component of the fluidised bed is at least : :
partially composed of coarse titania bearing 10 mineralisation has been demonstrated.
, 2001~51.
- 20 ~
Table 1 : Size Distribution of Fine Futile Feed (Examples 1, 2, 4) -Size Range (~m)Wt ~
+106 0.52 -106 + 90 11.37 - 90 + 75 31.78 - 75 + 63 33.28 - 63 + 53 13.13 - 53 9.92 ,~
10 Table 2 : Size Distribution of Petroleum Coke*
(Example 1) Size Range (~m)Wt %
-2000 + 1000 50 -1000 + 500 50 .,:
15 * synthetically sized mixture.
Table 3 : Size Distribution of Victorian Brown Coal Char*
Size Range (~m)Wt % :
-2000 + 1000 50 -1000 + 500 50 20 * synthetically sized mixture.
':
.
20017~
, :;;.,.:.
Table 4 : Size Distribution of Fine Futile Rutile Feed (Example 3) Size Range (~m) Wt %
+53 9.5 -53 + 45 29.9 -45 + 38 41.7 -38 18.9 ~, ~,""
- ~.
,~
. -, .-, ,, .., .~,.....
" ~
'' .'`'"'''''''' ' ," "','.', "'",,~
I . , ' ~, .:
~. '",' ~, : ' '~
2001751.
Table 5 : Summary of Trials in Examples 1 to 4 Test Example 1 Example 2 Example 3 Example 4 Reductant Petroleum Victorian Victorian Victorian Coke brown coal brown coal brown coal S char char char Initial bed weight (g) 1200 1200 1200 1400 Carbon in initial bed (g) 500 500 500 500 ", 10 Coarse rutile in initial bed (g) - - _ 400 Titania Mineral addition rate (g/min) 30 37.1 32 16.5 coarse 16.5 fine 15 50% passing aperture for mineral ~ -~
feed (ym) 70 70 43 184 coarse 70 fine .: , Chlorine addition 20 rate (Nl/min) 11.4 12.8 11.4 11.4 CO/CO2 at steady rate 0.78 50.0 6.0 80.0 : ' . ' ~;
.
,, . ~ i ~ . .. .. . . . . . ..
Z001'75~
"' Coke addition rate (g/min) 5.0 4.8 7.1 7.6 Final bed weight (g) 12431000 1258 1331 % titania mineral 5 in final bed 6.9 1.8 0.60 32.2 % titania recovery 65 65 43 69 Chlorine utilisation % 9o 9o 7s 9 .
Titania mineral 10 residence time(secs) 172 29.1 14.1 25.0 coarse 6.1 fine Fine mineral recovery/
residence time %/sec 0.382.2 3.0 7.1 , ;, . ...
' ; .;; '"
~ ;''' `
zoo~sl. , , ' .
Table 6 : Composition of Rutile Feeds wt %
Ti 57.1 :
Fe 1.60 ;~
Si 0-33 ~ ~ -Al 0.32 Cr 0.10 Mg 0.01 V 0.34 Mn 0.04 ~~
Zr 0.67 : :
Ca 0.01 ; ~ ~
,, ; ~.
Table 7 ~ osition of Carbon Reductants (%) Fixed C S Ash Volatiles 15 Pet.coke 98.7 3.6 0.4 0.6 ~rown coal char 93.5 0-3 3.0 3.5 '' '",'," '; ,', ; ,`"''"'~;'', "' " ' ', ', .. '' ',: "~' .
Claims (20)
1. A process for chlorinating fine grained natural or synthetic sources of titanium values which process comprises:
adding a fine grained material containing titanium dioxide to a fluidized bed comprising a coarse grained material and a source of active carbon, the bed being fluidized by a fluidizing gas; introducing a chlorinating agent into the fluidizing gas to chlorinate titanium dioxide and produce titanium tetrachloride thereby and recovering titanium tetrachloride from exit gases leaving the fluidized bed.
adding a fine grained material containing titanium dioxide to a fluidized bed comprising a coarse grained material and a source of active carbon, the bed being fluidized by a fluidizing gas; introducing a chlorinating agent into the fluidizing gas to chlorinate titanium dioxide and produce titanium tetrachloride thereby and recovering titanium tetrachloride from exit gases leaving the fluidized bed.
2. A process according to Claim 1 wherein the fluidising gas imparts a superficial velocity to particles comprising the fluidised bed that represents a substantial proportion of the terminal velocity of the fine grained titaniferous material in the feed.
3. A process according to Claim 1 wherein the superficial velocity lies in the range from 10 to 40, cmsec-1.
4. A process according to Claim 1 wherein the fine grained material has a particle size distribution in which more than 50% of titanium value is contained in particles having a diameter of less than 100 µm.
5. A process according to Claim 1 wherein the coarse grained material is a beach sand mineral having an average particle size in the range from 200 to 600 µm.
6. A process according to Claim 1 wherein the source of active carbon is char.
7. A process according to Claim 5 wherein the beach sand mineral is beach sand quartz.
8. A process according to Claim 5 wherein the beach sand mineral is beach sand rutile having an average particle size in the range from 150 to 250 µm.
9. A process according to Claim 5 wherein the beach sand mineral is beach sand rutile having an average particle size of about 250 µm.
10. A process according to either Claim 8 or Claim 9 wherein the beach sand rutile present in the fluidized bed is up to 65% by weight of the fine grained material.
11. A process according to Claim 6 wherein the char is derived from Victorian brown coal.
12. A process according to Claim 11 wherein the char as a particle size distribution lying in the range from 0.5 to 4 mm.
13. A process according to Claim 1 wherein the fine grained material is added to the fluidized bed at a rate determined by the quantity of chlorine and fine grained material in the exit gases.
14. A process according to Claim 1 wherein the chlorinating agent is chlorine.
15. A process according to Claim 1 wherein the chlorinating agent is selected from the group consisting of ferric chloride, phosgene and carbon tetrachloride.
16. A process according to Claim 1 wherein the fine grained material comprises material produced by grinding a coarse grained material contaminated with inerts.
17. A process according to Claim 1 wherein the initial fluidized bed contains about 60% by weight of the coarse grained material and about 40% by weight of the source of active carbon.
18. A process according to Claim 1 wherein the fine grained material is siliceous leucoxene having an average particle size in the range from 45 to 65 µm and containing 20% by weight of silica as quartz inclusions.
19. A process according to Claim 1 wherein the fine grained is selected from the group consisting of anatase, upgraded ilmenite, titaniferous slag, titaniferous minerals recovered from chlorinator wastes, ilmenite, and synthetic rutile.
20. Titanium tetrachloride produced by a process according to any one of Claims 1 to 19.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPJ1218 | 1988-10-28 | ||
| AUPJ121888 | 1988-10-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2001751A1 true CA2001751A1 (en) | 1990-04-28 |
Family
ID=3773479
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002001751A Abandoned CA2001751A1 (en) | 1988-10-28 | 1989-10-30 | Recovery of titanium values from minerals |
Country Status (4)
| Country | Link |
|---|---|
| KR (1) | KR900701663A (en) |
| CA (1) | CA2001751A1 (en) |
| WO (1) | WO1990004569A1 (en) |
| ZA (1) | ZA898175B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2487183C1 (en) * | 2012-01-10 | 2013-07-10 | Учреждение Российской академии наук Институт химии и химической технологии Сибирского отделения РАН (ИХХТ СО РАН) | Method for complex processing of kyanite |
| RU2518807C1 (en) * | 2013-01-30 | 2014-06-10 | Федеральное государственное бюджетное учреждение науки Институт химии и технологии редких элементов и минерального сырья им. И.В. Тананаева Кольского научного центра Российской академии наук (ИХТРЭМС КНЦ РАН) | Method of kyanite concentrate recycling |
| RU2653519C2 (en) * | 2015-12-11 | 2018-05-10 | Акционерное общество "Ордена Трудового Красного Знамени Научно-исследовательский физико-химический институт им. Л.Я. Карпова" (АО "НИФХИ им. Л.Я. Карпова") | Method for production of titanium tetrachloride |
| CN113387383A (en) * | 2021-05-24 | 2021-09-14 | 龙佰四川钛业有限公司 | Production method of high-fluidity titanium dioxide flash-dried material |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5320815A (en) * | 1987-07-13 | 1994-06-14 | E. I. Du Pont De Nemours And Company | Fluidized bed process |
| CN103086423B (en) * | 2011-11-03 | 2014-10-29 | 攀钢集团研究院有限公司 | Method for producing titanium tetrachloride from rutile |
| CN103818950B (en) * | 2014-02-27 | 2015-04-08 | 重庆大学 | Boiling chlorination furnace for preparing titanium tetrachloride by using fine-graded artificial rutile |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1066750B (en) * | 1959-10-08 | |||
| DE1071345B (en) * | 1959-12-17 | British Titan Products Company Limited Billmgham Durham (Großbritannien) | Plant for the continuous chlorination of titanium-containing material | |
| DE879546C (en) * | 1949-10-19 | 1953-06-15 | Titan Co Inc | Process for the production of titanium tetrachloride and iron oxide from titanium and iron-containing raw materials |
| DE1035901B (en) * | 1955-02-18 | 1958-08-07 | British Titan Products | Plant for the continuous chlorination of titanium-containing material |
| DE1067781B (en) * | 1956-10-31 | 1959-10-29 | British Titan Products | Method and device for introducing finely divided, fluidized, solid material into a reaction vessel |
| AU472288B2 (en) * | 1971-04-29 | 1973-10-18 | Wendell E. Dunn, Inc | A process for beneficiating titaniferous ores |
| US3867505A (en) * | 1971-10-26 | 1975-02-18 | Ppg Industries Inc | Method and apparatus for chlorinating metal bearing materials |
| GB1563304A (en) * | 1975-09-24 | 1980-03-26 | Quebec Iron & Titanium Corp | Chlorination of titanium slags |
| DE2551380C3 (en) * | 1975-11-15 | 1979-06-13 | Ernst Dr. Schultze-Rhonhof | Extraction of the titanium dioxide contained in red mud as titanium tetrachloride |
| JPS52151699A (en) * | 1976-06-11 | 1977-12-16 | Ishihara Sangyo Kaisha Ltd | Production of titanium tetrachloride |
| IT1134196B (en) * | 1980-11-06 | 1986-07-31 | Samin Spa | PROCEDURE FOR THE EXPLOITATION OF LEUCITICAL ROCKS |
| BR8805863A (en) * | 1987-11-10 | 1989-08-01 | Du Pont | FLUIDIZED BED PROCESS FOR CHLORATION OF MATERIAL CONTAINING TITANIUM; AND PETROLEUM LOAD COKE |
-
1989
- 1989-10-26 WO PCT/AU1989/000465 patent/WO1990004569A1/en unknown
- 1989-10-26 KR KR1019900701356A patent/KR900701663A/en not_active Application Discontinuation
- 1989-10-27 ZA ZA898175A patent/ZA898175B/en unknown
- 1989-10-30 CA CA002001751A patent/CA2001751A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2487183C1 (en) * | 2012-01-10 | 2013-07-10 | Учреждение Российской академии наук Институт химии и химической технологии Сибирского отделения РАН (ИХХТ СО РАН) | Method for complex processing of kyanite |
| RU2518807C1 (en) * | 2013-01-30 | 2014-06-10 | Федеральное государственное бюджетное учреждение науки Институт химии и технологии редких элементов и минерального сырья им. И.В. Тананаева Кольского научного центра Российской академии наук (ИХТРЭМС КНЦ РАН) | Method of kyanite concentrate recycling |
| RU2653519C2 (en) * | 2015-12-11 | 2018-05-10 | Акционерное общество "Ордена Трудового Красного Знамени Научно-исследовательский физико-химический институт им. Л.Я. Карпова" (АО "НИФХИ им. Л.Я. Карпова") | Method for production of titanium tetrachloride |
| CN113387383A (en) * | 2021-05-24 | 2021-09-14 | 龙佰四川钛业有限公司 | Production method of high-fluidity titanium dioxide flash-dried material |
| CN113387383B (en) * | 2021-05-24 | 2022-10-28 | 龙佰四川钛业有限公司 | Production method of high-fluidity titanium dioxide flash drying material |
Also Published As
| Publication number | Publication date |
|---|---|
| KR900701663A (en) | 1990-12-04 |
| WO1990004569A1 (en) | 1990-05-03 |
| ZA898175B (en) | 1991-10-30 |
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