FI58505B - NY TITANDIOXIDSAMMANSAETTNING - Google Patents

Description

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Fstmt · och r * gift «rttyr» laan · AmMcm utlagd och uti. * KrifcM pubHemd 10/31/17 Technology bv, Wagnerlaan 1A, Hilversum, The Netherlands (NL) (72) Wendell Earl Dunn, Jr., Woollahra, New South Wales, Australia-Australia (AU) (7U) Oy Jalo Ant-Wuorinen Ab (5U) New titanium dioxide composition This invention relates to a novel titanium dioxide composition obtained by treating titanium-containing ores, which has superior properties to natural rutile in the production of titanium dioxide pigments as a starting material.

In recent years, natural rutile deposits have been alarmingly depleted. Rutile has been the main starting material in the manufacture of titanium dioxide pigments, which are mainly used in paints, rubber and paper. Another important source of titanium dioxide is titanium-containing ores (nTi0PmFe 0).

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The treatment of titanium-containing ores to increase the relative amount of titanium dioxide they contain is already well known. Wet and dry processes such as acid treatment and alkali extraction as well as metallurgical slag removal and finally chlorination have been used to remove unwanted constituents from the ore. Chlorination of titanium-containing ores has involved either converting the entire ore mass to a mixture of volatile chlorides of titanium, iron and other metals and separating the components by distillation to produce substantially pure titanium tetrachloride, or preferably chlorinating iron oxides and other readily chlorinable metal oxides without chlorinating.

In the past, however, chlorination resulted in either a treated product, 2 58505 with a high iron content because chlorination was stopped when the titanium began to disappear, or chlorination was continued in such processes, resulting in a low iron content of the product but significant titanium losses. Continuous chlorination gives a titanium dioxide product which is poor due to its softness and fineness which in turn leads to titanium losses in the subsequent stages of the process.

Due to its physical strength and chemical purity, rutile is the preferred starting material for the production of titanium dioxide pigment, where it is chlorinated to titanium tetrachloride and then oxidized to the final titanium dioxide pigment product.

However, rutile has the disadvantage that its chlorination is much slower and more difficult than currently known processed ores.

A new titanium dioxide composition has now been found, which is a preferred starting material for the preparation of titanium dioxide pigments. The product has a higher bulk density, is cleaner and harder than the products obtained by processing titanium-containing ores according to previously known methods.

The novel composition of the present invention is more advantageous to use as a raw material in fluidized bed chlorination reactors than the products obtained by extraction because it has lower porosity and because larger pores reduce friability and dust losses. This avoids the large surface areas formed in the measurement processes, whereby the amount of adsorbed water in the particles is reduced. Adsorbed water has the disadvantage that it causes chlorine losses in the fluidized bed chlorination process when it converts chlorine to hydrochloric acid. The chlorination rate of this new composition of matter is between the chlorination rates of natural rutile and the new background products, and is high enough to reduce the bed thickness and increase the CO 2 / CO ratio in fluidized bed chlorination reactors. Chlorination rates are shown in Figure 1.

The invention relates to a novel titanium dioxide composition containing from 95.0 to 99.5 wt.% Of titanium dioxide, up to 1.0 wt.% Of iron oxides and easily chlorinable metal oxides, the remainder consisting of silicates and other difficult to chlorinate oxides.

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This new composition of matter has a bulk density of 1.6-2.4 g / cm 3, a hardness (VHN) of 275-650, and a porosity of 0.03-0.1 cm -1. The product can be used as a pigment.

In the process of preparing the composition of this invention, chlorine is passed through a fluidized bed having a thickness of about 0.6 m and a diameter of about 1.7 m (surface area about 2.2 m) and consisting of a titanium-containing 3,585,50 ore mixture. which contains 10-30 weight? carbon, at a temperature of 900-1100 ° C

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In a patient at a speed of about 0.15 m / sec. using about 1.7 nr / min of chlorine with air and nitrogen to maintain the flow rate and temperature. The layer becomes fluid and the chlorine is completely consumed inside the layer, forming ferric chlorides and mainly ferric chloride and other metal chlorides. These chlorides are continuously removed from the reactor in gaseous form. After 20-30 minutes or more, or until the "tickle" point, which is the time at which TiCl 2 leaves the fluidized bed, is reached, the iron oxide content of the product is about 2-10% by weight. The iron content is further reduced by alternating contact of the layer with a reducing agent such as carbon monoxide and then chlorine until the iron oxide content of the product is 1.0% by weight. or less, as described in our Finnish patent application No. 719/71 · The product can be further purified on a vibrating table after cooling in a reducing atmosphere to remove unreacted carbon and passing it through a magnetic separator to remove private particles containing a significant amount of iron oxide.

Alternatively, the product can be produced in a circulating process in which partially treated ore and carbon are continuously added to a fluidized bed reactor at 900-1100 ° C and chlorine is passed through the ore mixture so that the amount of overflow exits the reactor and cooled under reducing conditions. . The cooled ore is passed through a magnetic separator to separate the titanium dioxide product containing up to 1% by weight of? ferric oxide. All partially processed ore containing more than 1.0% by weight? iron oxide is returned to the reactor with new ore. This alternative process is described in more detail in our U.S. Patent Application Ser. No i + 563, filed February 21, 1970.

Figure 1 shows schematically in the form of a curve the chlorination rates of the product obtained by extracting naturally occurring rutile, the product according to the invention and titanium-containing ores in a manner known per se. The weight of the remaining product is expressed in grams as a function of the chlorination time in minutes.

Figure 2 shows the rate of change in bulk density in the chlorination of natural rutile, the product of the present invention (run TT-4) and the product obtained by extracting titanium-containing ores in a manner known per se. The change in bulk density (g / cm -1) is expressed as a function of the number of grams of residues obtained from chlorination.

Figure 3A is a photomicrograph at 200x magnification of treated titanium-containing ore produced by the measurement process 1a.

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Figure 3B is a photomicrograph at 200x magnification of a novel treated titanium-containing ore of the present invention.

Figure 4A is a photomicrograph 500x magnification of the rutile particle surface.

Figure 4B is a photomicrograph of a particle of the present invention.

Without wishing to be bound by any theory, it can be assumed that the higher density and hardness of the composition of this invention is due to the formation of thian tetrachloride in the reactor bed and then reaction with iron oxide in the crystal lattice of ilmenite. It is economically and technically advantageous to form titanium tetrachloride in the bed and the high carbon content accelerates the conversion of chlorine to titanium tetrachloride so that titanium tetrachloride and not chlorine, is the substance that causes the conversion of iron oxides to iron chlorides and deposits titanium dioxide molecules in particles. It is also necessary to maintain the reducing conditions in the bed and thus excess carbon is added to the reactor to maintain the reducing conditions at all times.

It is believed that the total reaction in the bed is reaction (a) with other reactions occurring during the process being (b), (c) and (dj: (a) 1/2 C + FeO-TiOg + Clg - FeClg + TiO 2 + 1/2 CO g (b) TiO 2 2 Cl 2 + 2 C = TiCl 2 + CO and CO 2 in a ratio of about 9: 1 at 1000 ° C (c) TiCl 2 + 2FeO-TiO 2 = 2FeCl 2 + TiO 2 * TiO 2 (dj 3A TiCl 2 + FeO 2 -TiO 2 - FeCl3 + 3/4 TiOg-TiOg The process equipment used may be a conventional fluidized bed chlorination reactor, and the carbonaceous material should preferably be low carbon chlorine such as charcoal, petroleum coke and the like. may be 40% iron oxide and 54% titanium dioxide In addition to these components and depending on their origin, ilmenite contains varying amounts of silica and silicates which are difficult to chlorinate and chromium, manganese and vanadium oxides which are easily chlorinated.

The metal chlorides formed as a by-product mainly contain ferric chloride and small amounts of ferric chloride, manganese chloride, chromium chloride and chlorides of other metals. The by-product stream also contains carbon monoxide, carbon dioxide, nitrogen and small amounts of titanium and chloride.

The characteristics of a typical extracted product prepared by aqueous acid extraction of reduced ilmenite are shown in column A of Table I as defined above.

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Table I

A B C D E

Extracted product according to the invention CO + Clg CO + Clg Rutile composition

TiO 2% 95.55 9.2 95.2 95-99.5

Fe% 1.43 1.7 0.02 1.0

Bulk density g / cm 3 1.4 1.4 1.16 2.64 1.6-2.4

Hardness (VHN) 116 199 175 995 275-650

Porosity (g / cnP) 0.17 0.03-0.1

Chlorination processes normally involve reacting the ore with chlorine and carbon monoxide. When the amount of residual iron oxide in the particles in these processes has decreased to 2-10 wt.%, Titanium losses begin to occur in the form of volatile titanium tetrachloride. The product according to this method is shown in column B of Table I. Continuation of chlorination further reduces the iron content but the product becomes permanently soft and crumbly due to the loss of titanium particles. The properties of such a product are shown in column C of Table I. The properties of natural rutile and the new composition are shown in columns D, respectively. E.

The particles of the composition of matter of this invention are essentially solid titanium dioxide and its density, hardness, porosity and chlorination rate properties are between the corresponding properties of rutile and previously known products.

The hardness reported in Table I is Vickers hardness (VHN) as determined by a Vicker low load microbrinell hardness tester as described in Zussman, Physical Methods in Determinative Mineralogy, Academic Press, London and New York, 1967, pp. 131-150.

Bulk density was determined by weight and volume measurements. Porosity was determined with a mercury porosimeter in the pore diameter range of 0.2-20 microns.

The chlorination rate was determined using 20 g of the treated product or natural rutile in a fluidized bed to which a mixture of 50% CO 2 and Cl 2 was introduced at a rate of 26 mmol / min. both at a temperature of 1000 ° C. The results are shown in Figure 1.

The wear of the various raw materials in the fluidized bed under chlorination conditions was studied by performing an experiment in which 20 g of the raw material was reacted at 1000 ° C with 26 mmol / min of CO and Cl 2. The results of 6 58505 series of weight measurements with increasing time intervals relative to volume weight are shown as a log-log curve in Figure 2. The volume and weight of a substance that retains its geometric shape as it loses components from its surface decrease in a constant ratio, keeping the volume weight constant.

When a substance is chlorinated internally, its volume remains constant, its weight decreases and the slope of the remaining weight-density curve will be 45 ° · A substance that is partly chlorochemically and partly internally will be between these previous cases. As the substance deteriorates to complete decomposition or surface decomposition, the curve showing the ratio of residual weight to density falls perpendicularly. From this one can see what kind of dust losses can be expected for different substances.

Figures 3a and 3B show two photomicrographs of the treated products taken under a microscope at 2000x magnification. Photomicrograph 3A is taken of Sample A, which is extracted titanium dioxide, and Photomicrograph 3B is taken of Sample B, which is a composition of matter of the present invention. It can be seen in micrograph 3A that it has a large number of fine pores while micrograph 3B has much fewer pores and the pores are larger. This clearly shows the difference due to the recoating of titanium. Figures 4A and 4B show two samples viewed on an electron micrograph at 5000x magnification. Figure 4A shows natural rutile, and it is known that rutile is very dense and has a low porosity, while Figure 4B clearly shows the growth of granules due to the re-deposition of titanium dioxide.

The novel composition according to the invention has surprisingly good properties. This product can be converted to titanium tetrachloride while minimizing dust generation compared to the use of extracted titanium-containing ore. Jolla dust refers to the small titanium dioxide particles used to form titanium tetrachloride. Dust formation causes titanium losses. It is also much more advantageous to use the product of this invention compared to rutile because it has a higher chlorination rate than rutile.

The higher hardness and strength of the product of this invention minimizes titanium losses because further chlorination to form titanium tetrachloride produces less fines. The chlorination rate of the composition according to the invention is higher than that of rutile. As a result, a lower ore layer can be used, which has the advantage of lower carbon consumption and less carbon monoxide formation, and thus the process for producing titanium chloride becomes safer and more economical.

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The following illustrates a process according to the invention. Temperatures are expressed in degrees Celsius and percentages are by weight unless otherwise indicated.

Example 1:

The composition of matter according to the invention was prepared in a cylindrical flat-bottomed brick bed reactor with a brick lining thickness of about 23 cm and an inner diameter of about 1.7 m. and 60 cm above the flow threshold above which some of the solid reactants leave.

The bottom of the fluidized bed reactor was equipped with a gas distribution device with openings of about 3.6 cm.

A mixture of Murphy ore ilmenite and 25 wt.% Petroleum coke was added to the reactor. The average diameter of the titanium-containing ore was δ microns and the analysis was as follows: 54.1 wt.% TiO 2, 21.0% FeO 2, 21.0% Fe 2 O 2, 1.51% MnO and the rest mainly silicates. After the ore-coke mixture was sufficiently added to the reactor, the temperature in the reactor was raised to 1000 °, and the mixture of chlorine and air was passed through a fluidized bed.

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through it at a flow rate of about 1.7 nr / min, it was occasionally necessary to dilute chlorine with air and oxygen or nitrogen to maintain the temperature in the reactor at 1000 ° to convert iron oxide to volatile ferric chlorides, mainly ferric chloride containing small amounts of ferric chloride, which was removed from the reactor through a stainless steel outlet along with nitrogen, HCl and other gases.

After the addition of sufficient chlorine to convert all the iron oxide in the ore to ferric chloride, large amounts of titanium tetrachloride vapors were detected in the exhaust gases. The reactor and its contents were then cooled under reducing conditions in the presence of propane and the contents were screened to remove unreacted carbon. The remainder of the contents were passed through a magnetic separator to obtain a first fraction having an iron content of 1.0% by weight / 6 or less of iron oxide and a second fraction having an iron content of 1.0% by weight or more of iron oxide.

The product comprising the first fraction was cream in color and had the following characteristics:

TiO 2% 96.5

Fe% 0.17

Bulk density g / cnP 1.73

Hardness 337

Porosity 0.00 8 58505

Example 2: About 45 kg of ilmenite and a sufficient amount of charcoal were charged to a chlorination reactor and heated. The chlorination unit was a conventional fluidized bed reactor with an inner diameter of about 43 cm, a jacket of stainless steel lined with refractory bricks, and equipped with an inlet pipe for solids on the side wall, a bottom dispenser for feed gases and a conical roof with a conical roof kaasunpoistoput-

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ki. The layer was fluidized at about 0.25 rpm with air. When the temperature had risen to 900 °, about 11 kg of Great Lake petroleum coke was fed to the reactor. Air was excluded at 1000 ° and chlorine was introduced at a rate of about 0.25 nr / min. From time to time, small amounts of oxygen-reducing chlorine were also fed with a total flow of n.

0.25 rpm to maintain temperature balance. The exhaust gases containing ferric chlorides, CO 2 and small amounts of CO and TiCl 4 were washed with base in a countercurrent washer. The chlorine feed was stopped when the liquid leaving the base scrubber turned thick white, indicating that TiCl 4 had left the bed. About 0.06 nr / min was then fed, while the ore layer was reduced with the carbon 10

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minutes, then about 0.03 nr / min Clg and about 0.22 nr / min were fed until TiCl 4 was again detected in the effluent. The alternating reduction and chlorination steps were performed five times. At each chlorination step, the chlorine input was stopped when TiCl 4 was detected; the chlorination time therefore varied gradually from 5 minutes to 1 minute. The layer was then allowed to cool, magnetically separated and treated on a wet vibratory table. A product was obtained with the following characteristics:

TiO 2% 96.5

Fe% 0.17

Bulk density 1.73 g / cm -1 VHN (Hardness) 435

Porosity 0.075 g / cm 2

The product of the invention is as such useful as a filler for rubber and paper when first ground to reduce particle size. For example, 1.0-10 weight /? the product can first be ground in a ball mill and then mixed with unvulcanized rubber in a rubber roller. The filled unvulcanized rubber is then mixed with a suitable accelerator and compressed at an elevated temperature in a mold to produce a tough, light rubber product.

As described above is the composition of this invention