DE2855467B2 - Process for the production of synthetic titanium dioxide via the direct digestion of rutile with sulfuric acid - Google Patents

Description

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The invention relates to a process for the production of synthetic titanium dioxide from natural rutile (TiO ₂ ), rutile-containing polymineral titanium ores and slags via direct digestion as titanium sulfate insoluble known rutile, in the same way as, for example, ilmenil; (FeTiOj) can be completely unlocked.

Synthetic titanium dioxide is the starting material for the production of titanium dioxide pigments and, increasingly, highly enriched rutile is the raw material for the production of titanium tetrachloride for metal extraction. The production of synthetic «0 titanium dioxide has so far been based predominantly on the processing of ilmenite, titanomagnetite (ilmnite magnetite) and iron titanate-containing slags according to the principle of the“ Norwegian process ”. With, for example, 70-96% sulfuric acid is the raw material in "a mixed related to the TiOrGehalt ratio of 1.2-1.8 and transferred at 120-180 ⁰ C in a water-soluble Titansullätkuchen The digestion cake is or after the reaction in water Dilute acid released from the% process cycle The concentration is generally between 150 and 25) g T1O2 / I. Before the titanium content is precipitated by hydrolysis as titanium dioxide hydrate, any trivalent iron present is reduced, for example with iron scaffold, and 70 ~ 80% of the iron is deposited _{in the form of FeSO 4} · H _{2 O.} After the solution has been cleaned of other foreign substances such as B. As, P, Zr, Pb etc. at pH> 1.5 the hydrolysis of titanium dioxide hydrate takes place by! Heating up to 100 ° C

Titanium dioxide hydrate is removed by heat treatment dries, dehydrated, of volatile matter (e.g. sulfuric acid) and converted into crystallized titanium dioxide with pigment character (anatase or rutile pigment) (Ullmanns Encyklöpadie der technischen Chemie, Vol. 13,! ». 761 ff., 3rd edition, Urban and Schwarzenberg Munich-Berlin 1962).

For natural rutile, which can contain up to 30% Fe (Ramdohr P., Struiz, H .: Klockmanns textbook der Mineralogie, 16, ed. p. 530, F. Enke Verlag Stuttgart 1978), polymineral titanium ores and slags containing rutile is a production of synthetic titanium dioxide according to the principle of the Norwegian process due to the fact that rutile does not react with H2SO4 alone, but only in the melt flow with bisulfate or by fluoride or by alkalis can not be carried out (Gmelins Handbuch der inorganic Chemie, Titan, p. 85, 8th edition. Verlag Chemie GmbH, Weinheim 1951). Boiling concentrated sulfuric acid (338 "C) released after ¹ AStUndiger action of only 2.7% at 800 ⁰ C previously calcined TiO ₂ (rutile) (Cheme, Deiss Berg, Martin-Borret, App. Chim. Anal 28 [1946] 197/8 ).

There has been no lack of attempts to develop digestion processes for rutile. A prey practiced Possibility to manufacture synthetic titanium dioxide from natural rutile or from rutile slags the metallurgical Ilmenite processing by reducing smelting for the recovery and reduction of the iron content is obtained Chlorination of the raw material to titanium tetrachloride. Titanium tetrachloride vapor can then both with superheated steam and directly with oxygen or an oxygen-containing gas can be converted to titanium dioxide. This process can have a disadvantage The effect of the released hydrogen chloride on the resulting titanium dioxide by a relatively coarse crystalline product without pigment properties can arise.

When processing rutile concentrates, polymineral titanium ore concentrates containing rutile and titanium-rich slag from metallurgical ilmenite processing with an iron content of over 10% there are considerable difficulties in the chlorination. On the one hand, when titanium raw materials with a high iron content are chlorinated, too much chlorine is used Formation of iron (IIl) chloride consumed for that hardly Use, and from which chlorine can only be recovered at high costs for others will be ferric chloride despite its higher level Boiling point is entrained with the tetrachloride vapor and in the coolers in solid, finely divided form deposited. Since iron (III) chloride is also only 0.03% soluble in liquid titanium tetrachloride, form blockages that make the technical implementation of the process difficult (Ullmanns Encyklöpädie der technical chemistry vol. 17, p. 419 ff, 3rd edition, Urban and Schwarzenberg Munich-Berlin 1966, Gmelins Handbuch der inorganic Chemie, Titan, pp. 92 / 93.8. Edition Verlag Chemie GmbH. Weinhpyn 1951).

Other proposals for the digestion of natural rutile or rutile slags have so far for the Production of synthetic titanium dioxide has no technical importance

For example, the laid-open specification DE-OS 17 92 582 states that "natural rutile or synthetic rutile concentrates with a particle size of less than 40 μm are treated with sulfuric acid at temperatures of 220 to 280 ° C for a digestion time of 1 to 24 hours" (claim 4, pp II), so that anhydrous titanylsulfate arises "But must be adhered to for a good digestion rate of over 95% minimum times here that are for Aufschlußtemperauiren of 220 ⁰ C for 20 hours to 280 ⁰ C at 3 hours." ( P. 5, paragraph 1). »However, the crystalline reaction product only dissolves very slowly in water or dilute sulfuric acid. the

However, the rate of dissolution can be increased considerably if the solution is reduced to such an extent that small amounts of Ti ³ + ions are present "(S, 2, Abs, 3). For continuous digestion it is suggested that" with a concentrated sulfuric acid of 94 to 98 percent by weight H ₂ SO ₄ content in a large excess amount calculated on the titanium dioxide content of the starting material "is worked," preferably ... with a TiO ₂ to H ₂ SO ₄ ratio of 1: 4 to 1:10 " (P. 3, para. 2; claim 6, p. 12). Since in the specified temperature range between 220 and 280 ⁰ C after a certain time a temporary conversion of the suspension into a colloid-like state "occurs and the precipitated titanyl sulfate can hardly be filtered and washed" (p. 4, paragraph 2), ι The digestion must be carried out in several stages (claim 7, p. 12).

A disadvantage of the above process proposal that a complete digestion of natural and synthetic rutile, the upper grain limit is set at 40 microns is not possible with sulfuric acid in the preferably claimed temperature range of 220 to 280 ⁰ C in a process stage, at temperatures above 225 ° C Any excess of concentrated sulfuric acid forms a titanyl sulfate with a low water content that is sparingly soluble in cold and warm water (A. v. Pamfilov, AT Chudjakova, Zumal obscej Chim. 19 [1949J p. 1443/53), so that this temperature is a limit for represents the conversion of rutile with sulfuric acid to water-soluble titanyl sulphate. Since the reaction product formed in the temperature range between 220 and 280 ° C also falls in the form of a "collide-like" precipitate that is difficult to filter, the following measures are required which call into question technical application:

- Use of 94 to 98% H2SO4 up to 19 times Excess,

- Reduction of part of the Ti ⁴⁺ ions to Ti ³ + ions,

- Multi-stage process management. The opposite of rutile concentrates with undefined

Increase in the reaction kinetics achieved in the reaction with sulfuric acid when the grain boundaries are broken down to an upper grain boundary of 40μΐη by ball milling, is a consequence of the increase in the surface area. The increase in surface area by ball milling, which is essentially characterized by frictional stress, is achieved by breaking up structure-related weak zones, which can be preferred levels of cleavage, for example. There is no change in the thermodynamic requirements through the formation of structural variants and unstable intermediate states. Reaction temperatures below 220 ° C. are therefore of no technical importance for the conversion of rutile with an upper grain limit of 40 μm; at 220 ° C., the reaction time for a 95% conversion of this material with 94 to 98% H ₂ SO ₄ to give titanyl sulfate is 20 hours.

Due to the fact that rutile is largely insoluble in sulfuric acid, the other proposed methods have in common that detachable compounds are initially generated via reactions in the gas phase and in the melt flow and by solid-state reactions. So z. B. proposed to ^{treat rutile preheated to 1040 0} C at temperatures up to 290 ⁰ C with NH ₄ F and the resulting volatile TiF ₄ in aqueous NHj or NH ₄ F solution Catch deposition of TiOj (Burgess Titanium Co, SS. Svendsen, Can, P, 369 915 [1938] according to G1938II 4368; Norw. P. 58 413 [1937] according to C, 1937II4466; Norw. P, 58 757 [1938] according to C, 1936 U 1409), further proposals relate to the formation of alkali or alkaline earth titanates at elevated temperatures, which then after treatment with acids (H ₂ SO ₄ , HCl, H ₂ SO ₃ ) are suitable solutions for the hydrolysis of Titanium dioxide hydrate result. Thus, for example by Richter HW (US.P. 19 32087 (1933) C 193 411 396) rutile treated at temperatures up to 650 ⁰ C with 75% NaOH solution and with NazCO3 avoiding the molten state, so that a calcination product is produced, which contains around 46% acid-soluble TiO ₂ as Na ₂ TiO _3. To remove the Fe, the residue is _{washed out with 5-10% H 2} SO ₄ and then digested with 50% H ₂ SO ₄ . Is the use of MgO for the decomposition of rutile via the formation of MgTiO ₃ at temperatures of 1500 ⁰ C the subject of various patenting (Metal & Thermit Corp. SJ Lubowsky (BJ 3 51841-1931 - C 1931II1740;. 7 FP 02642-1931 - after C. 1931 Π1472; US.P. 16 40 952 - 1927 - C 1927 Il 2336; US.P. 17 93 501 - 1931 - C 193112915).

The disadvantage of the last-mentioned process is the reduction in the metal content of the ore concentrates due to the addition of reactants. For the complete conversion of rutile z. B. with MgO to MgTiO ₃ , the addition of MgO leads to a reduction in the titanium content of the raw material from a maximum of 60 to 40%. Furthermore, the added foreign elements must be separated again and, if possible, regenerated in a subsequent process step to form the output connection. In addition to a very high level of reagent consumption compared to the direct digestion of rutile with sulfuric acid, these manipulations lead to a considerable outlay in terms of process technology.

Although it must be admitted that a satisfactory digestion can be achieved, in particular with the above-mentioned process of chlorination of rutile or rutile slag from metallurgical ilmenite processing, there has so far been no economical solution if the raw materials mentioned are not in the form of high-percentage concentrates or with iron contents above 10 % are available. Particularly for rutile sands, which, due to their fine grain size, cannot be _{enriched to the required high-percentage concentrates with 90-95% TiO 2} using conventional mechanical processing methods, and rutile-containing polymineral titanium ore concentrates with TiOr contents below 80%, there is no alternative to the chlorination process.

It has now been found that, contrary to the doctrinal opinion, a direct, complete digestion of rutile as well as rutile-containing polymineral titanium ores and slags with sulfuric acid in one stage is possible if a mechanical activation of rutile or a rutile component in titanium raw materials in the form of structural changes due to lattice disturbances and lattice vacancies takes place in such a way that the ratio of the reflection intensities of the activated material which can be determined by X-ray fine structure measurements for rutile to the inactive starting material /// "is less than 0.7, preferably 0.50.

In the case of mechanical activation, which is essential to the invention, the shock load of rutile about those caused by the crushing effect

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Surface enlargement in addition to structural variations and unstable intermediate states due to lattice disturbances and lattice vacancies, the latter generated as a result of the dissociation of a low proportion of oxygen. electrical conductivity (Ehrlich, P .: phase relationships and magnetic behavior in the titanium-oxygen system, Z. Elektrochemie 45 [1939] pp. 262 - 72; Verwey, EJ.W .: electron level in non-metallic substances, Philips techn. Rundschau 9 [1947 ] Pp. 47-54) shows such a strong improvement in the digestion behavior of rutile with sulfuric acid that direct digestion in one stage is possible at temperatures as low as 200 ° C. As a comminution process for producing structural changes, vibratory milling is used due to its predominantly impacting stress accelerations of up to 10 g and point temperatures greater than 800 ⁰ C are particularly suitable.

Vibrating mills are to be understood according to i's physicochemical reactors (Gock, E: measures to reduce the energy requirement in the Vibratory grinding, processing technology, 1979, p. 343/47).

In conventional ball milling, in which the impacting stress only plays a subordinate role alongside the frictional stress the stress energy for the generation of structural changes is generally not sufficient, so that a complete digestion of rutile with sulfuric acid after this pretreatment method is not possible in one process stage the patent application DE-OS 17 92582 confirmed in the for the digestion of rutile, which in the Ball mill is crushed to an upper grain limit of 40 µm, with concentrated sulfuric acid in the Excess for the production of anhydrous titanyl sulfate sine multi-stage process management claimed will. The increase in the reactivity of rutile after ball milling to an upper grain limit of 40 | xm is essentially the result of the improvement the statistical relationship in the contact between mineral surface and disintegrant. A change in thermodynamic conditions, like them in the case of mechanically activated rutile, among other things, by increasing the electrical conductivity of the magnetisability and reducing the reaction temperature as a result of the structural changes to the Expression is not achieved by crushing rutile to an upper grain limit of 40 μm by ball milling Offenlegungsschrift DE-OS 17 92 582 based on information about the reaction conditions of the digestion of rutile with an upper grain limit of 40 μηι confirmed The following extreme reaction conditions are granted in this document:

- Reaction temperatures up to 300 ° C

- Sulfuric acid (94-98%) up to a 19-fold excess

- Response times up to 24 hours

... "for a good degree of digestion of over 95%", "minimum times must be observed, which for digestion temperatures of 220 ° C are 20 hours ... 6 ^r >" (p. 5, paragraph 1).

The superiority of the method of mechanical activation over that of surface enlargement Ball milling for the digestion of rutile with sulfuric acid can best be demonstrated by the reaction conditions. With a degree of activation J / io = 055, a digestion of 97% is achieved under the following conditions (see Table 1, page):

- reaction temperature 200 ° C

- sulfuric acid (85%) about stoichiometric (TiO ₂ ZuH ₂ SO ₄ = I : 2J5)

- Response time 3 hours.

In the mechanical activation of rutile, which is essential to the invention, the degree of mechanical activation is determined with the aid of the ratio of the X-ray diffraction intensities of the activated material (I) to the inactive starting material (Io). In order to define the inactive starting material and to delimit it, it was determined that ball milling is preceded by grinding in such a way that the grain size is less than 10 µm (see also p. 8.1. Paragraph).

The degree of mechanical? Activation of rutile can be determined by measurements of the increase in the specific electrical conductivity and susceptibility as well as by reducing the X-ray intensities at the for rutile-specific crystal lattice planes in X-ray structure recordings. While conductive If the ability and susceptibility measurements require pure rutile concentrates, the X-ray fine structure recordings of rutile can also be made if this Mineral occurs in low concentration or as a component of polymineraiischer titanium ores and slags

The measurement of the X-ray intensities in X-ray diffraction on statistically distributed crystal lattice planes in powder preparations and thus the determination the degree of mechanical activation of rutile depending on the energy expenditure of the vibratory milling process is according to the von H. Neff in »Fundamentals and Application of the X-ray Fine Structure Analysis ", Oldenbourg, Munich, 1962, Chapter 10 and by R. Glocker in "Material testing with X-rays", Springer-Verlag, Berlin 1971, Chapter VL 21. and 26. methods described possible. The radiographic examinations for the inventive Procedures were carried out with a Krirtalloflex IV with a counter tube goniometer. A An X-ray tube with a Co-anticathode and an X-proportional counter tube served as a radiation detector with an Fe filter in front. The measurements of the intensities were carried out with the Bragg's Equation for certain crystal lattice planes calculable angles as well as by determining the integral cursing intensities when going through the angle ranges in question with the help of a Pulse counter.

The preparation was arranged by pressing the powder samples to be measured into the medium Hole (0 20 mm) made of a square sample holder. In order to rule out any influence of the preparation method in comparative measurements, The initial weight and pressing pressure were kept constant (2.5 g, 0.2 t).

The X-ray diffraction intensity was measured at the following lattice planes of rutile, the position of which is determined by the Miller indices (hk / ^: 110 (d = 3.25A °) 211 (d = 1.69 A ⁰ ) 101 (d = 2, 49 A °)

With increasing mechanical Bea.ispr Hing of The rutile values are reduced by vibratory milling

X-ray diffraction intensities without significant line broadening. This is an expression of lattice disturbance, which are referred to as "frozen thermal oscillations". It is based on the idea that the heat oscillations of the atoms and their ϊ normal position in the lattice suddenly occur through the action of energy be fixed, so that there is a shift in the centers of gravity of the atom; the thermal vibrations are then executed around this new layer. The mean atomic displacement ö.y in called perpendicular to the network plane under consideration.

In order to avoid absolute measurements, for the radiographic determination of the grid disturbances at Rutile as a function of the mechanical stress, which by R. Fricke (Z. Elektrochemie Vol. 46 [1940] ι> P. 491) for chemically active substances proposed measurement of the intensity ratio between a an undisturbed reference preparation and a disturbed preparation according to the following equation

i'iuiViilicn: X

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It means:

λ is the wavelength of the X-ray light and
& the observed angle of reflection.

For the mechanical activation of rutile, which is essential to the invention, as a function of the mechanical Stress by vibratory grinding can be, as could be proven by series tests, the simplify the measurement method described in the form that instead of the logarithmic ratio, the direct intensity ratio between the inactive starting material and the mechanically activated Material is used. For the definition of the inactive starting material it was determined that by ball milling a comminution in such a way that the grain size is 100% smaller than 10 μm. Since the phase boundary of the rutile structure is secured up to a stoichiometry of T1O130 in the event of an oxygen deficit (Ehrlich, P .: phase relationships ... in the titanium / oxygen system, Z. Elektrochemie 45 [1939] p. 362/72) each intensity ratio /// "represents a cumulative parameter, which is a compression of information about grain distributions, Lattice disturbances and lattice vacancies, and which has a certain digestion behavior of rutile in Sulfuric acid is assigned.

The effect of mechanical activation of rutile achieved by vibratory milling depends on the concentration and nature of any accompanying minerals that may be present, on the construction and operating conditions of the vibratory mill and on the duration of the milling. With increasing milling time, the rate of disintegration of rutile and polymineral titanium ore concentrates and slags containing ilutile with sulfuric acid increases, so that the milling and disintegration times can be coordinated with one another. If a longer digestion time can be justified in terms of process technology, a short grinding time is sufficient. In view of the volume of the digestion reactor, however, it is advantageous to keep the reaction time short. Vibratory grinding is therefore preferably carried out in such a way that the intensity ratio 7 / _fo determined for rutile by X-ray is at least 0.70

The digestion of mechanically activated rutile to be carried out in the process according to the invention as ore concentrate with any degree of enrichment, as a component of polymineral titanium ores or -Slag can, based on the TiCV content of the respective raw material, with sulfuric acid in practical stoichiometric ratio. If necessary, for accompanying elements, which in turn is sulfuric acid consume, made an additional dosage.

The kinetics of the digestion of mechanically activated rutile is strongly temperature dependent. The digestion is therefore preferably carried out at temperatures above 180 ^0C. The best results are obtained if the digestion is carried out at temperatures between 200 and 250 ⁰ C.

As a heat source for the digestion, the heat of hydration, which when a small amount is added The amount of water to which the titanium raw material mixed with concentrated sulfuric acid is released are used. The at the lowering of the boiling point resulting from the dilution of sulfuric acid bcs'imni * then here at 760 Torr achievable digestion temperature. In addition, adding a small amount of water has the advantage a reduction in the viscosity of the raw material-acid mixture, so that the diffusion conditions and thus the reaction rate of the conversion in the digestion reaction by mechanical or pneumatic Movement of the digestion mass can be improved.

Elevated pressures are unnecessary in the novel process, if the boiling point of the applied sulfuric acid concentration is above 180 ⁰ C. For any necessary processing of thinner acids, for example, 55% sulfuric acid whose boiling point is 130 ° C, to achieve the preferred temperature range above 180 ⁰ C, an increased steam pressure is required.

The further processing of the water-soluble digestion mass produced by the process according to the invention can be based on the process engineering of the »Norwegian Process« for the processing of Ilmenites are made as follows: Dissolve the digestion mass with water or dilute acid the cycle of the process, separation solid - liquid, Purification of foreign elements from the filtrate, precipitation of titanium dioxide hydrate by hydrolysis, calcination from titanium dioxide hydrate to titanium dioxide, as well as production of TiOr pigments by mechanical and chemical post-treatment.

The invention is illustrated by the following examples:

example 1

The effect of mechanical activation can best be demonstrated on a pure concentrate of natural rutile. A rutile concentrate with the following composition was used:
5930% Ti (9931% TiO ₂ )
0.07% Fe

The theoretical Τι content of rutile is 5935%. The mechanical activation took place in the satellite container of an operational vibratory tube mill. The specific energy expenditure per ton of regrind is given as a measure of the mechanical stress. The degree of mechanical activation of rutile is given by the ratio of the X-ray diffraction intensities of the activated millbase (I) to the inactive starting material (Iq) at the lattice plane 110 corresponding to 2θ = 32.1 ° when using Co radiation.

presses. The production of the defined grain size 100% less than 10 μm for the inactive starting material took place by grinding in a ball mill. For the digestion of 100 g of rutile, 85% strength was used Sulfuric acid used in a stoichiometric ratio. The reaction temperature was 200 ° C. Table 1 shows the dependency of the mechanical activation

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of rutile from the specific energy expenditure in vibratory grinding and the resulting reaction speed the digestion with sulfuric acid to water-soluble titanium sulfate. The degree of exposure was determined in each case by determining the water-soluble fraction or by quantitative X-ray fine structure analysis established.

Table 1 Clean-
Intensities
(Uli) Degree of exposure ("■ '")
in .dependent wedge of 3 h Digestion time lh) 6 h 8h = Specifi
shear
F-'nergic-
A u Ivan el // ,,. 2 h 20.0 4 h 27.3 29.9 kWh / t 1.0 17.0 in c
J7, J 22.0 S2 7 6!, 0 I. 0 0.78 34.6 72.1 Λ Λ Ο
TT, (J 96.5 98.4 ■ 75 0.64 57.0 79.5 80.2 98.7 - 120 0.58 66.9 97.0 90.9 - - 180 0.55 85.2 - 240

Example 2

For the rutile concentrate according to Example 1, Table 2 shows the influence of the initial sulfuric acid concentration on the reaction rate of the digestion. The degree d>: r mechanical activation, expressed by the ratio of the X-ray diffraction intensities l / _{/ a} was 0.58. The solids content and the digestion temperature were constant influencing variables at 100 g and 200 ° C.

Table 2

ll _: so ₄ -Con /.

Inclusion Trail (%)

depending on digestion time (h)

3h

2 h

4 h

55.4
59.6
66.9

67.0
71.2
79.5

77.2 83.9 90.9

Example 2 0.58. The at different reaction temperatures depending on the reaction time The results obtained are shown in Table 3

Table 3

Tem- digestion level (%)

peralur depending on the digestion time (h)

C 2h 4h 6h 8h

180

200

200 "

220

250

Since stoichiometric conditions are assumed for the conversion of rutile with sulfuric acid, a reduction in the initial sulfuric acid concentration can only be achieved by adding water or superheated steam to this amount of acid. The dilution with water resp. Superheated steam occurring reduction in the viscosity of the Rohsnoff-acid mixture leaves a mechanical or pneumatic movement of the reaction mixture. The associated improvement the diffusion conditions come, as Table 2 shows, expressed by an increase in the rate of response.

Example 3

The concentrate according to Example i is also used to demonstrate the temperature dependence of the digestion of rutile. For all experiments, IOC g of rutile were mixed with 90% H ₂ SO _4. The degree of mechanical activation Vu> was 53.6
59.6
62.0
68.4
69.5

66.6
85.1
87.4
89.0
89.5

78.5 96.1 97.9 98.2 98.6

The test series marked with an asterisk in Table 3 was carried out with 55% strength sulfuric acid, which has its boiling point at 130 ^° C., in an autoclave at an increased water vapor pressure (7.5 bar) at 200 ^° C. The result shows that, provided that there is a sufficient supply of acid, the reaction temperature is the decisive operating condition

Example 4

To demonstrate the general validity of the digestibility of rutile by mechanical activation, the digestion results for a low content rutile concentrate with 75.6% TiO ₂ are given in Table 4. The following composition was analyzed for the rutile concentrate:
4532% Ti (75.6% TiO ₂ )
1131% Fe
1.09% Si
1.72% approx
0.75% Al
038% Mg

According to Example 1, the digestion took place with 100 g of solid and 85% H ₂ SO * in a stoichiometric ratio at 200 ^° C., depending on the mechanical stress caused by vibration.

Table 4

More specific
Energy expenditure X-ray
intensities
(110) Degree of expansion (%> depending on
from the duration of the slaughter (h) 4 h (i h 8 h kW h / i ///., 2 h 18.2 21.6 23.9 O 1.0 13.1 83.0 95.8 98.3 130 0.61 65.3 87.2 98.7 ._ 190 0.52 71.2

Example 5

As an alternative to the chlorination process, rutile slags, which are produced by reducing melting of ilmenite concentrates in order to reduce and recover the iron content, can be digested directly with sulfuric acid in one step using the process according to the invention. As test material was a titanium slag, which was annealed at 900 ⁰ C for rutile formation, used with the following metal contents: 46.8% Ti (78% TiO ₂₎
11.4% Fe

1.3% Si

0.5% Al

0.17% V

0.24% Mg

For the digestion of 100 g titanium slag, S5% H2SO4 was used in a siöclviöiTictrischcri ratio Cirsgc. The operating temperature was 200 ⁰ C. In Table 5, the decomposition result in dependence is indicated by the degree of mechanical activation at different reaction time.

Table 5

Specific X-ray
Energy expenditure intensities
(HO) Hm Degree of exposure (%) depending on
on the digestion time (h) 4 h 6 h 8 h kW h / t 1 2 h 23.4 28.4 33.2 O 0.64 13.9 84.0 87.9 98.7 130 0.57 66.2 87.2 98.8 - 180 Example 6 69.8

The digestion of a rutile-containing polytineral Titanium ore concentrate ntdi the invention The method is based on the example of an artificially produced mixture of 35 wt .-% rutile, 30 wt .-% ilmenite and 35% by weight of titanomagnetite, in which titanium is also present as ilmenite, is shown. The chemical analysis showed the following composition:

33.6% Ti (21% Ti as rutile)
21.0% Fe
1.2% Mg
0.8% Al
7.4% SiO ₂
0.8% V

gg g g

H2SO4, 200 ⁰ C. The determination of the degree of mechanical activation was carried out from the ratio of X-ray diffraction intensities /// "of Rutilanteils to the lattice plane 110. In the mechanical activation of rutile in the presence of other minerals, these act as grinding aids, so that the for the specific energy expenditure required for activation is reduced. Table 6 shows the digestion result after various reaction times. While the ilmenite portion of the ore mixture can also be digested without pretreatment, complete digestion according to the invention is only possible after mechanical activation of the rutile portion.

Table 6 Roentgen-
intensities
Rutile (HO)
HlO Degree of exposure (%) depending on
on the duration of exposure (h)
2h 4h 38.1
82.0
85.3 6h 8h More specific
Energy expenditure
kWh / t 1
0.58
030 27.3
63.4
/ 2.4 47.9
96.0
98.7 68.4
99.0 0
105
180

Example 7

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In titanium-containing blast furnace slag, titanium is present in the form of iron titanates, which are produced by the reaction of Obtain rutile with FejOs at high temperatures. in the in general, these slags can be digested in the same way as ilmenite. Significant loss of titanium arise, however, if free rutile is present in addition to the iron titanates. Such a slag that in addition 30% by weight of rutile were admixed, was digested according to the method according to the invention. The chemical analysis showed the following composition:

Table 7

47.8% Ti (of which at least 18% Ti as TiO ₂ ) 10.6% Fe 0.2% Mn 0.7% Ca 3.2% SiO ₂ 0.6% Al 0.4% V

The digestion conditions were: 100 g of a slag-rutile mixture, 85% H ₂ SO ₄ , 200.degree. Table 7 shows the digestion result as a function of the degree of mechanical activation of the rutile content after various reaction times.

More specific
Energy expenditure Roentgen-
intcnsities
Rutile (110) Degree of exposure (%) depending on
from the Aufschlussdiuicr (h) 4 h (i Il X h kW h / l II, .. 2 h 49.8 62.4 78.6 0 1 .34.0 84.5 98.5 - 105 0.60 66.3 88.9 100 - 160 0.54 72.9

Claims (2)

Patent claims: 1, A process for the production of synthetic titania via the direct decomposition of natural rutile, rutile-containing polymineralic titanium ores and slag with sulfuric acid at temperatures above 180 ⁰ C in a process stage, said ores, ore concentrates and slags are mechanically activated prior to the pulping, characterized characterized in that the mechanical activation by vibratory grinding is carried out in such a way that the degree of mechanical activation generated by impact loading, expressed by the radiographic is parameter J // _{o, is} less than 0.7 2. The method according to claim 1, characterized in that the degree of mechanical activation generated by the dun: h impact load, expressed by the radiographic parameter Ui _{0, is} less than 0.5