Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/04—Oxides; Hydroxides
  • C01G23/047—Titanium dioxide
• • 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
  • C22B34/1204—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 preliminary treatment of ores or scrap to eliminate non- titanium constituents, e.g. iron, without attacking the titanium constituent
  • C22B34/1209—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 preliminary treatment of ores or scrap to eliminate non- titanium constituents, e.g. iron, without attacking the titanium constituent by dry processes, e.g. with selective chlorination of iron or with formation of a titanium bearing slag

Definitions

• the present invention relates to a process for the formation of acid digestible titania products.
• titania bearing minerals feed to processes for the formation of white titania pigments.
• chloride and sulphate processing are generally less stringent than for the chloride method.
• a particular requirement of the sulphate process for pigment production is that the mineral feed should be substantially digestible in strong sulphuric acid. For naturally occurring titanium bearing minerals this requirement is met only by ilmenite mineral (FeO. Ti0 2 ) or its weathered products with strictly limited degrees of alteration to rutile and ferric titanate.
• ilmenite feed has the disadvantage of low titania content while slag feed has the coupled disadvantages of requiring dangerous and unpredictable digestion conditions and providing incomplete titania recovery in digestion and subsequent dissolution.
• ilmenites are suitable for pigment production via the sulphate process or upgrading to slag.
• ilmenites with greater than about 0.15% Cr 2 0 3 have not found direct or indirect application in sulphate pigment production, as chromium causes severe problems with pigment product colouration.
• Ilmenites with relatively high iron contents (especially in excess of the composition "FeO. Ti0 2 ”) and with high gangue contents (eg. about 5% total contained alumina and silica) are unlikely to be suited for upgrading to a valuable slag product, and may also not compete economically with other feeds for the production of sulphate process pigments.
• the product should be formed economically at scales of operation of less than 25% of current slagmaking operations.
• the titanium content of the product should be equal to or higher than the range of titanium contents associated with slag products.
• the titanium mineral source for the product may be minerals other than ilmenite. Ilmenites which are not suitable for slagmaking or direct feeding to sulphate pigment operations should also be capable of upgrading to useful products by the process considered.
• Acid digestibility and titanium recovery in sulphate process pigment should be higher for the product than for currently available slag products.
• the necessary additives are not readily incorporated into a titania matrix in either oxidation or reduction roasting.
• High temperature reduction typically 1200 - 1300°C is necessary with most available natural minerals for homogeneous distribution of additives to occur in static carbon beds in residence times of less than two hours. This is despite the claim in the prior art that reduction can be operated at temperatures as low as 1130°C with sufficiently effective additive incorporation to ensure full development of acid solubility.
• the object of the present invention to provide an industrially useful process for the production of acid soluble titania. Accordingly the present invention provides a process for producing acid soluble titania which process comprises the steps of:-
• b represents the percentage by weight of Mn ⁇ contained in the mineral
• d represents the percentage by weight of Ti0 2 contained in the mineral
• step (iii) cooling the product of step (ii) ;
• step (iv) subjecting the product of step (iii) to an aqueous chemical treatment to substantially remove iron from the mineral
• manganese or magnesium compound is an oxide or is capable of decomposing to an oxide under reaction conditions.
• the manganese or magnesium compound is an oxide or is capable of decomposing to an oxide under reaction conditions.
• Titanium bearing minerals such as ilmenite, leucoxene, anatase and rutile
• Fine titanium minerals eg. those for which 100% passes through a lOO ⁇ aperture screen
• the majority of titanium bearing minerals eg. those found in beach sands will benefit by grinding during mixing in order to provide adequate mineral/additive contact or sufficient mineral surface area for subsequent steps.
• the titania product may contain greater than 90% Ti0 2 (on the basis of contained titanium) , yet it will normally have higher solubility in sulphuric acid and exhibit higher recoveries of titania in sulphate process pigment than slag products, which typically only contain up to 85% Ti0 2 .
• the product properties will depend on the particular feed used.
• the flowsheet illustrating a preferred embodiment of the invention is depicted diagrammatically in Figure 1.
• the flowsheet consists of an (optional) grinding step followed by an optional mixing/agglomeration step, a thermal reduction and cooling step and an iron metal removal step.
• Optional mineral separations step may follow iron removal.
• a particular preferred step is agglomeration prior to the heating step.
• agglomeration prior to the heating step.
• the present invention allows for the use of mineral in fine grained form (typically 100% passing a lOO ⁇ m aperture screen but 95% coarser than 5 ⁇ m diameter) .
• the agglomerates are capable of being treated in the reduction systems of the present invention.
• titaniferous minerals it will be necessary to grind the feed, using any suitable technique prior to the agglomeration step. Since the titania product derived from a mineral feed which is finer than 20 m in diameter is not be easily separable from fine iron oxide products in subsequent processing steps the grinding step should seek to minimise the proportion of the mineral reporting to the minus 20 ⁇ m fraction.
• the weight average particle size of the ground product would ideally lie betwe 50 ⁇ m and lOOzm.
• the agglomeration step will typically include the addition binder to a moistened (eg. 5 - 12% moisture) fine mineral feed in a suitable agglomerating device.
• a moistened (eg. 5 - 12% moisture) fine mineral feed in a suitable agglomerating device.
• Either low intensity disk or drum type or high intensity mixing type agglomerators are preferably used, although briquetting or any other suitable technique may be applied.
• a range of suitable agglomeration techniques has been described in International Patent Application No. PCT/AU89/00314. There are few limitations on agglomerate size, although advantageously only a few percent of the agglomerated prod should pass a screen with 50 ⁇ m aperture and agglomerates of less than 4mm particle size will be more readily treate in subsequent steps of the present invention. A narrow particle size distribution is not required.
• additives may be incorporated in either the agglomeration or grinding steps. Even distribution of additives within the agglomerates is advantageous.
• Additives may be included in powdered or slurry form or in solution with the moisture input to the agglomeration step.
• additives may include compounds of magnesium, as disclosed in prior art.
• compounds of manganese may be used to achieve special advantages under some circumstances.
• any suitable organic or inorganic binder may be used in the agglomeration step.
• inorganic binder eg. sodium silicate, bentonite and other clay minerals, magnesium salts, lime, soda, etc
• organic binder eg. lignosulphonate, PVA, molasses etc.
• Binders which hydrolyse in-situ eg. tetraethyl orthosilicate, aluminium sulphate/urea mixtures
• Binder additions in the range 0.5 - 5.0% on a water free basis have been found to be suitable. In the case of inorganic binders it is beneficial ' to limit binder addition to less than 1% on a water free basis.
• the formation of densely packed agglomerates which shrink and sinter significantly upon heating is consequently to be avoided.
• the desired open structure is more readily achievable where the mineral to be agglomerated contains only small quantities of material of smaller particle diameter than 20 ⁇ m and where the average size of agglomerates is less than 1mm (although larger particle size can be used) .
• Additional steps may be incorporated between grinding and agglomeration, for example where grinding has resulted in the liberation of gangue or impurity bearing grains.
• a separation step of any type but especially including separations based on particle size and density, magnetic or electrostatic response or on surface properties, or on any combination of these properties, may be included. If necessary the liberated and upgraded mineral may then be dried prior to agglomeration, using any suitable drying device.
• Titania reduction may then be completed in a short region of rising bed temperature near the kiln discharge end.
• the result is reaction completion under the necessary high temperature conditions (eg. at 1170°C) while the charge is held at significantly lower temperatures (eg. 1130°C) for the majority of its reduction time.
• Such operation also assists in minimising accretions.
• Additives may also be incorporated in order to assist in removal of impurity grains in operations subsequent to reduction.
• chromite metallisation is encouraged by addition of manganese into agglomerates, enhancing chromium removal from the acid soluble titania product by magnetic separation after aqueous aeration in which the magnetic ferrochrome alloy remains passive. Separations based on chromite metallisation are the subject of International Patent Application No. PCT/AU89/00461.
• the char may be separated from the minerals by a combination of sizing and magnetic separation. Where the mineral has been agglomerated prior to reduction the reduced agglomerates may be crushed to liberate gangue which has not been metallised, allowing upgrading by magnetic separation.
• An important aspect of the present invention is an improvement to prior art processes for removal of metallic iron from reduced mineral. Prior art methods of aqueous aeration for metallic iron removal have been applied to removal of iron only from non acid soluble titania matrices.
• the improvement resides in the definition of the necessary conditions for the effective removal of iron metal from an acid soluble titania matrix with control of the nature of the separable iron oxide product.
• it is the definition of specific reagents which are effective in assisting iron removal by aqueous aeration which is the basis of the improvement.
• the method of aqueous aeration presently disclosed involves the agitated suspension of metallised acid soluble titania in a solution of reagents formulated in a particular manner into which finely divided air bubbles are introduced.
• aqueous aeration is conducted in the temperature range 60 - 80°C and will continue for from 8 to 24 hours.
• the improvement comprises adding reagents to the aeration step which form complexes with iron in order to stabilise iron in aqueous solution and also have the effect of locally buffering pH in such a manner that iron oxides form only at higher oxidation potentials, i.e. at sites away from metal bearing grains.
• the reagents should also ideally act to stabilise a particular iron oxide (eg.
• aqueous systems which provide for chelation or complexing of iron i.e. sequestering agents for iron, and therefore have the effect of stabilising iron temporarily in aqueous solution in pores in and around the titanate grains are highly effective as aeration systems.
• the stability of iron in solution must not be such as to prevent its precipitation as iron oxide under the strongly oxidising conditions which exist in the general aeration liquor. Strong stabilisation of iron in solution will result in consumption of complexing reagents and sharp increase in pH. As a consequence further transport of iron out of titanate grains will be retarded and in-situ iron oxide precipitation may result.
• Agglomerate disintegration during aeration allows removal of the thus liberated gangue or impurity bearing grains by any suitable means after aeration.
• Iron oxides are first removed from the predominantly titaniferous granular product of aeration by wet cycloning, gravity based separation, wet screening or any other effective means.
• Subsequent separation of non titaniferous grains eg. by flotation, magnetic separation, electrostatic separation or gravity based separation
• Such an upgrading step is particularly useful for impurity grains whose properties are similar to the process feed properties prior to the disclosed treatments but where a property difference exists between product grains (eg. where the feed is contaminated by chromite) .
• a particular feature of the acid soluble titania product formed according to the disclosed procedures is that a small amount of metallic iron, at 0.1 - 2% by weight of th product, remains in a form which is totally inaccessible to aeration or acid leaching. It has been found that this residual iron metal typically is distributed in metal particles of diameter less than 3 ⁇ m which are totally encapsulated by dense acid soluble titania. This residual iron metal allows an effective magnetic separation of the product from non magnetic contaminants, eg. quartz and silicate gangue, while not interfering with the removal of highly magnetic material at lower magnetic field strengths and field strength gradients.
• non magnetic contaminants eg. quartz and silicate gangue
• titaniferous product washing with dilute acid for example 5 - 20% sulphuric acid
• dilute acid for example 5 - 20% sulphuric acid
• chromite grains remaining in the titaniferous products of the processes described herein may not be apprecially soluble in acid digestion of the contained titania.
• the chromite grains are rendered inert to acid digestion during thermal reduction in the presence of ilmenite. This disclosure has important implications for the usefulness of the product in the sulphate process for pigment manufacture. Examples : The following examples describe a number of tests which serve to illustrate the methods disclosed herein.
• Example 1 In this example 300g of a fine grained ilmenite of composition provided in Table 1 and average particle size of 55 ⁇ m was mixed with 150g of renovated brown coal char (-4mm + 0.5mm) and placed into a stainless steel furnace pot. A 10mm layer of char was placed on top of this mixture and the pot was positioned in a heated muffle furnace. The charge reached a maximum temperature of 1180°C after 75 minutes and was held in the furnace for a further 120 minutes before the pot was removed and allowed to cool in air.
• Table 1 300g of a fine grained ilmenite of composition provided in Table 1 and average particle size of 55 ⁇ m was mixed with 150g of renovated brown coal char (-4mm + 0.5mm) and placed into a stainless steel furnace pot. A 10mm layer of char was placed on top of this mixture and the pot was positioned in a heated muffle furnace. The charge reached a maximum temperature of 1180°C after 75 minutes and was held in the furnace for a further 120 minutes before the pot was removed and allowed to cool in air
• Coarse char was separated from the reduced product by sizing through a 200 ⁇ m screen, followed by magnetic separation to provide a separate metallised ilmenite product. Chemical analysis indicated that metallisation of iron was 94.1% complete. X-Ray diffraction analysis indicated that virtually all contained titania was present as anosovite, with no evidence of rutile, reduced rutiles or nitrides/carbides.
• Impurity separation after reduction and char separation was tested by magnetic separation of a subsample using a laboratory Carpco lift type magnetic separation, rejecting non magnetics.
• 44% of the chromium could be rejected as non-magnetic chromite, accompanied by only 10% of the contained titania.
• the iro oxides formed in aeration were primarily blac magnetite, as confirmed by X-Ray diffraction. After removal of separable iron oxides by screening at 38 ⁇ m the aeration product contained a total of 6.3% iron, with 0.3% iron present as metal.
• the titanium content of the product, expressed in terms of the dioxide was 84.4%.
• Magnetic separation in a Carpco lift-type magnetic separator was performed to reject 72 of the contained chromium (as chromite) , 37% of the contained aluminia and 48% of containe silica to a magnetic fraction, leaving an 86.9% Ti0 2 non-magnetic product at 0.30% Cr 2 0 3 .
• Example 2 In this example 5g of a fine grained siliceou leucoxene of composition provided in Table 2 and average particle size of
• Example 3 was conducted identically to example 2 with the exception that 7.5% Mn0 2 addition was made in place of the magnesite addition.
• the acid solubility of titania in the reduced product was measured as 97.4% in this case.
• Example 4 Ilmenite having the composition provided in Table 3 was ground and sized to the range -106 + 53 ⁇ m.
• Example 5 In this example the ilmenite to be reduced (55/zm average particle size) was first agglomerated with addition of 3% lignosulphonate, 0.7% bentonite and 10% moisture in a laboratory Patterson-Kelly agglomerator. The -2mm + 0.25mm agglomerated product was dried for subsequent reduction. The composition of the agglomerates is provided in Table 4. A 400g quantity of agglomerates was admixed with 200g of -4mm + 1.4mm renovated brown coal char, with a top layer of char as for example 1. Reduction at 1180°C as for example 1 then followed. After reduction and separation of char from the cooled reduced agglomerates they were carefully crushed in closed circuit with a 90im aperture screen such as to fall in
• Magnetic separation was then used to reject 4.9% of the material to a non magnetic fraction containing 29% of the original chromium and producing a magnetic product
• Example 6 Product acid solubility was tested as per example 1 without further grinding.
• the titania in the product was determined to be 88.1% soluble.
• the final phosphorus content 35 was 0.09% P 2 0 5 compared with an ilmenite feed phosphorus content of 0.46% P 2 0 5 .
• Example 6 In this example 300g of a fine grained ilmenite of composition provided in Table 5 and average particle size of 55 m was mixed with 150g of renovated brown coal char (-4mm + l.4mm) and placed into a stainless steel furnace pot for reduction in an identical manner to that described in Example 1.
• Magnetic separation of the mineral after reduction removed 25.0% of the contained chromium as non magnetic chromite grains.
• the reduced and separated product was subjected to aqueous aeration in 1.8 litres of 0.2% NH 4 C1,
• the iron oxides formed were separated by screening to undersize at 38 m screen aperture, and were confirmed to consist of red/brown lepidocrocite.
• the +38 ⁇ m mineral contained a tocal of 4.2% iron, with 0.03% iron present as metal.
• Magnetic separation was performed on the +38 m aerator product to reject 29.8% of the contained chromium (as chromite) , 13.9% of the contained alumina and 9.9% of the contained silica to a magnetic fraction, leaving a 90.2% Ti0 2 non-magnetic product at 0.61%
• the iron oxide produced in aeration was predominantly a brown amorphous material which did not settle readily and could not be removed from the +38 ⁇ m product. It was evident that in-situ iron oxide formation within titanate grains had occurred as the +38im product contained a total of 6.3% iron, with continuing evidence of iron present as metal.
• Example 8 Tn this example agglomerates in the particle size range -4mm + 0.25mm were formed from ilmenite of composition given in Table 6 by mixing with 3% lignosulphonate, 0.7% bentonite and 7% moisture, followed by drying in a rotary dryer. These agglomerates were fed to a 5m long, 0.4m internal diameter rotary kiln at 5kg/hr with 13kg/hr of -5mm + 0.5mm Victorian brown coal char.
• the temperature distribution in the kiln was controlled by use of discharge end burner and air injection lances inserted into the kiln gas space from the feed end such that for the final 2.5m of kiln length the temperature was above 1100°C and for the final 0.5m of kiln length the temperature was 1135°C.
• the kiln discharge was cooled in an Archimedes spiral before collection. The cooled discharge was magnetically separated from char and analysed by
• Example 3 has identified manganese additions as effective in promoting the formation of acid soluble phases in a similar or superior manner to that of magnesium disclosed in the
• Table 1 Composition of Ilmenite in Example 1, wt %
• Sample contains 3.5% free quartz and 3.5% free zircon.
• Table 3 Composition of Ilmenite in Example 4 wt %

Landscapes

• Chemical & Material Sciences (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Inorganic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)

Priority Applications (3)

Applications Claiming Priority (1)

Publications (1)

Family

ID=3763700

Family Applications (1)

Country Status (2)

Cited By (2)

Citations (1)

• 1990
  • 1990-05-24 JP JP2510190A patent/JPH06500304A/ja active Pending
  • 1990-05-24 WO PCT/AU1990/000217 patent/WO1991017956A1/en unknown

Patent Citations (1)

Also Published As

Similar Documents

Legal Events