WO1990004569A1

WO1990004569A1 - Recovery of titanium values from minerals by fluidized-bed chlorination

Info

Publication number: WO1990004569A1
Application number: PCT/AU1989/000465
Authority: WO
Inventors: Michael John Hollitt; Denby Harcourt Ward; John Takos
Original assignee: Wimmera Industrial Minerals Pty. Ltd.
Priority date: 1988-10-28
Filing date: 1989-10-26
Publication date: 1990-05-03
Also published as: KR900701663A; ZA898175B; CA2001751A1

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.

Description

RECOVERY OF TITANIUM VALUES FROM MINERALS BY FLUIDIZED-BED CHLORINATION 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 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, attempts to treat fine grained titanium dioxide

containing materials according to the prior art have 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.

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 values from fine titanium dioxide minerals by

chlorination in fluidised beds operated at intensities similar to those used in the treatment of coarser

minerals.

As indicated above, a major use of naturally 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 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 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 only be maintained at capacity, while obtaining good pigment recovery from the feed, if the fluidised bed 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 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 in the range 150 - 250 μm. It is generally accepted that feeds with appreciable quantities (e.g. greater than 15%) of material in the -100 urn size fraction are not

acceptable for these chlorinators and will result in excessive losses due to gas entrainment.

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

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 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 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 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 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 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 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

4,440,730 (Bonsack), it was projected that the fluidised bed chlorination treatment of conventionally sized (+200 urn) rutile mineral could be carried out at mineral reaction rates of less than 30 minutes at 1000°C if the usual petroleum coke reductant was replaced by brown coal char. However, no attempt has been made to treat fine mineral e.g. at -60 urn) 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. 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 μm) was treated using brown coal char as 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 1000°C. The combination of fine 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 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

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 concerns about excessive losses of fine coke by

entrainment in product gases. Successful use of the process has not been demonstrated for less reactive 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 number of potential titanium dioxide feed sources

(including natural mineral, slag fines and chlorinator 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 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 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 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 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 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 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 caroon, 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 wherein the fluidizing 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 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 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 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 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

particles less than 100 urn 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 1000°C at a rate sufficient to provide for a stoichiometric proportion of chlorinating agent in the fluidising gases. The

superficial gas velocity in the fluidised bed is set to values similar to those used in conventional industrial chlorinators, viz. approximately 20 cm sec . Contrary to expectations from the teachings of prior art it was found that under such circumstances recoveries of up to 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

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.

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 size range 200 to 600 μm) together with the active carbon source, for example char, which has enabled treatment of finely particulate minerals without unacceptable mineral and char losses, may operate in the following manner.

It appears that the coarse mineral acts to 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 into the exit gas stream by ensuring a degree of

backmixing of fine solids and hence providing longer average residence times. 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 solids is reduced.

The use of an active carbon 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 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 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, 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) and a single gaseous reagent (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 actual chlorination reaction, in a reaction sequence such as: Cl₂ (g) = 2Cl^* (adsorbed, carbon surface)

Cl^* = Cl (g) (desorbed gaseous monatomic chlorine) TiO₂ + (4-2x) Cl^o (g) = TiO_χ Cl_4-2x (l-x/2) O₂ (g)

¹/20₂ + CO (g) = CO₂ (g)

CO₂ (g) + C = 2 CO^* (adsorbed, carbon surface) CO^* = CO (g) (desorbed, gaseous)

TiO_x Cl_4-2x + xCO (g) + 2x Cl (g) = TiCl₄ (g) + x CO₂ (g) While the above reaction sequence is not certain, there is evidence that carbon surfaces become directly involved in the acceleration of chlorination reactions, 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 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 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. 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 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 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 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

supplementary feed of coarse mineral in order to maintain bed fluidisation. Beach sand rutile (at 250 urn average particle size, for example) would form an advantageous supplementary feed material.

A suitable carbonaceous reducing agent for use in the disclosed process is char derived from Victorian brown coal. This char typically has a surface area of some 100m²/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 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 present process, provided somewhat higher carbon contents and deeper beds are used to ensure complete reaction. 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 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 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 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 chlorine input rates and bed mineral additions determined by bed pressure 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

distributor plate from below.

Best advantage may be taken of bed mixing conditions with feed injection from above, although either method may be used to provide adequate mixing in a carefully considered design. The injecting gas may be 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 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 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 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 virtue of 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

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 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 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

distribution, with excellent recoveries. For example, beneficiates from grinding/mineral processing circuits or 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

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. 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 outlet 8 for removing gaseous products.

Examples

The following non-limiting examples illustrate preferred embodiments of the invention. Table 5 provides a summary of the examples. Example 1

Chlorination was performed in a 75 mm 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 1000°C. 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 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 between 50 and 100 urn 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 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 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

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 bed was determined by chemical analysis. The fine mineral residence time could then be determined according to:

The performance of the described system using 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 ran -500 um and the bed was composed 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. 172seconds).

The recovery achieved in this case is consistent with expected elutriation of mineral from the reactor upon chlorination to a size (approximately 43 μrn) 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 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 superficial 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 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 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 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 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 μm, 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 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 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% 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. 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 by chlorination gases, to effect recovery of titania from 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

mineralisation has been demonstrated.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

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.

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 orocess 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.