EP0100865B1 - Process for the production of a hydrolyzable titanyl sulphate solution - Google Patents

Description

The present invention relates to a method for producing a hydrolyzable titanyl sulfate solution from mixtures of previously ground llmenite- and titanium- (III) -containing raw materials, in particular titanium (111) -containing slags, digestion of the raw material mixtures with sulfuric acid and dissolving of the solidified reaction masses in an aqueous solvent.

Digestion of ores to extract the valuable components contained therein is a heterogeneous reaction in which solids are reacted with liquid or molten components.

For heterogeneous reactions, the general rule is that the reaction rate or the turnover per unit of time is essentially determined by the size of the surface of the solid. For a high reaction rate or as complete a material conversion as possible, it is advantageous to have a solid with the largest possible surface area. The surface of a given amount of solids is largely determined by the size of the particles. The smaller the individual particles, the larger the surface available for a heterogeneous reaction.

An increase in the surface area of solids is generally achieved by grinding processes. Before the digestion, the solids to be digested are usually ground to a specific fineness in grinding units such as drum ball mills, ball vibrating mills, pendulum mills or roller mill mills, which are equipped with suitable classifying devices. The energetic efficiency of such dry grinding is known to be very poor and efforts have not been lacking in the past to improve this situation.

Despite all the improvement measures, the grinding of titanium ores is still very ineffective from the point of view of energy utilization, and there is a desire for further optimization.

According to US Pat. No. 2,437,164, the grinding of titanium ores, in particular ilmenite, can advantageously be carried out in the presence of naphthenic acids.

Due to economic, ecological and also procedural advantages, binary or tertiary raw material mixtures are increasingly used for the production of hydrolyzable titanyl sulfate solutions. In addition to ilmenite, these consist to a large extent of titanium-containing slags which, in contrast to ilmenites, have a more or less large amount of trivalent titanium.

However, the presence of naphthenic acids in the raw material mixtures containing sulfuric digests containing titanium (III) leads to considerable disadvantages during the course of the process. A strong foam formation depends on the reaction product escaping from the digestion vessel, and there is also a strong SO _z development during the digestion reaction. Finally, the titanium (III) content of the slags is practically completely broken down during the digestion, so that titanyl sulfate solutions are formed which are poorly suited for hydrolysis. The degradation of trivalent titanium by various carbon-containing compounds, such as naphthenic acids, is also described in US Pat. No. 2,850,357.

The publication M.T. Melnik, E.V. Smirnova, "Improved process for grinding imenite and titanium dioxide" Lakokrasoch Mater. lkh. Phrimen, Volume 3, No. 58, 1972, describes the grinding of ilmenite in the presence of triethanolamine or "organo-silicon fluid G KZh-94" and the reduction in grinding time that is achieved with it.

However, the grinding of titanium (III) -containing raw materials and the subsequent use of the raw materials ground in this way for the production of a titanium sulfate solution with avoidance of disadvantages, such as high SO _z emission and degradation of the titanium (III) content, cannot be derived.

It was therefore an object of the present invention to provide a process for improved ore grinding which does not have the disadvantages described above and is universally applicable in particular for slag containing titanium (III).

It was surprisingly found that the addition of alkanolamines and / or polysiloxanes leads in the dry grinding of Titanschlakken to a clear improvement of the grinding, without other disadvantages, such as _for a high SO emission, reduction of the titanium (III) content, foam or to produce unsatisfactory digestion yield.

The present invention thus relates to a process for preparing a hydrolyzable titanyl sulfate solution from mixtures of previously ground ilmenite and titanium (III) -containing raw materials, in particular titanium (III) -containing slags, digestion of the raw material mixtures with sulfuric acid and dissolving of the solidified reaction masses in an aqueous solvent, the titanium (III) -containing raw materials being ground in the presence of organic auxiliaries from the group of the alkanolamines and / or polysiloxanes.

The auxiliary agent or additives are added to the slag for grinding in amounts of 0.002 to 0.5% by weight, preferably 0.005 to 0.15% by weight, even small amounts giving a clear economic advantage. The addition can take place before the actual grinding of the slag, but also by means of suitable feeding devices into the mill during the grinding process. A procedure is preferred in which the auxiliary is added to the slag before the drying preceding the grinding. It is cheap, but does not constitute a limitation of the inventive concept, to add the auxiliaries in the form of aqueous solutions and / or emulsions, because this results in the better distribution of the adjuvant the total surface of the regrind is conveyed. The auxiliary can be added in mixing drums, but also, for example, by spraying devices. In principle, all methods are suitable which ensure a uniform distribution of the auxiliary over the total volume of the material to be ground.

Particularly good results are obtained if the alkanolamine is a monoisopropanolamine and / or a diisopropanolamine and / or triisopropanolamine.

The polysiloxanes used can have a chain, branched or cyclic structure and can contain alkyl, aryl and / or cycloalkyl radicals and / or hydroxyl radicals. Due to economic considerations, polydimethylsiloxanes are particularly suitable.

In order to achieve a favorable distribution of the organic auxiliaries according to the invention, it is advantageous to add them in the form of aqueous emulsions and / or solutions.

The method according to the invention can in principle be applied to the most varied designs of dry grinding units, such as, for example, ball drum, ball oscillating, pendulum or roller roller mills. In any case, a significant improvement in the grinding is achieved, which is either expressed in an increased fine particle size of the ground material with the same grinding output used or, if the desired fine particle size is sought, leads to a reduction in the grinding time or, in other words, to an increase in throughput of the ground material through the mill. This results in considerable energy savings in the grinding energy to be used.

Difficulties have arisen in the usual discontinuous digestion of sulfuric acid from ore mixtures of the type described, which are based on the fact that the reaction temperature passes through two or more maxima. This means that the reaction mixture does not solidify uniformly or does not solidify until the reaction temperature has passed the maximum. These effects can impair the flow, handling, monitoring and control of the operational digestion reaction.

It has been found that the grain size of the ores used is of crucial importance when carrying out the joint sulfuric acid digestion of ilmenite and titanium-containing slags.

The difficulties described do not occur if the llmenite raw materials used for the hydrolysis are relatively coarser in terms of their mean particle size than the titanium (III) -containing raw materials used.

This finding contradicts the general view that the ilmenites and titanium-containing slags used in the digestion of sulfuric acid should be as fine as possible in order to achieve a satisfactory digestion behavior (cf. e.g. Winnacker-Küchler, Chemische Technologie, 2nd ed., Vol. 2, P. 572).

Particularly good results are achieved when using ilmenite raw materials with an average particle size of 0-90% less than 40 [Lm titanium (III) -containing raw materials with an average particle size of 91-100% less than 40 µm and that when used of ilmenite raw materials with an average particle size of 0-60% smaller than 40 pm titanium (III) -containing raw materials with an average particle size of 65-100% smaller than 40 µm are used.

The raw materials are ground in the grinding units described above, which are equipped with suitable classifying devices in order to achieve a targeted adjustment of the grain size distribution of the ground material. The grain sizes can also be generated using pendulum mills or roller mills. If necessary, the setting of a certain particle size of the ores intended for the sulfuric acid digestion can also be carried out by means of screening devices, such as Vibrating screens or air jet screens are used.

The additives according to the invention enable the grain sizes to be obtained to be obtained economically (see also FIG. 5).

In addition to achieving a good digestion result, ore mixtures with the defined grain sizes are characterized in that the ore components used in the raw material mixture reach the maximum reaction temperature in the same time after starting the digestion reaction and the mixture solidifies uniformly when this temperature is reached. Such ore mixtures can be easily digested with sulfuric acid even in discontinuous batch operation.

The method according to the invention is explained by way of example below. Unless otherwise stated, all percentages are percentages by weight.

• 1) Glasgefäss, 0 10 cm, zylindrischer Teil 20 cm, konischer Teil 10 cm lang,
• 2) Messinggefäss mit Heizbandage und Asbestschnur umwickelt, befindlich in einem aussen isolierten Schutzgefäss,
• 3) Tauchrohr zur Einleitung von Luft
• 4) Gummiabdeckung,
• 5) Röhrenofen zur Lufterhitzung,
• 6) Thermoelement mit Regler (7) und Trafo (8)
• 9) Rotameter,
• 10) Transmitter und Druckschreiber (11),
• 12) Trafo für Gefässbeheizung
• 13) Doppelelement für Trafo und Schreiber (14),
• 15) Thermoelement für Schreiber (Gemischtemperatur),
• 16) Thermometer (Gemischtemperatur),
• 17) Tropftrichter.

The tests were carried out in the apparatus shown in FIG. 1. Numbers (1) to (17) identify the following parts:

• 1) glass vessel, 0 10 cm, cylindrical part 20 cm, conical part 10 cm long,
• 2) Brass vessel wrapped with a heating bandage and asbestos cord, located in an externally insulated protective vessel,
• 3) Immersion tube for the introduction of air
• 4) rubber cover,
• 5) tube furnace for air heating,
• 6) Thermocouple with controller (7) and transformer (8)
• 9) rotameter,
• 10) transmitter and printer (11),
• 12) Transformer for heating vessels
• 13) double element for transformer and recorder (14),
• 15) thermocouple for recorders (mixture temperature),
• 16) thermometer (mixture temperature),
• 17) dropping funnel.

Example 1-16

The titanium raw materials specified in Tab. 1 are brought to a uniform grain size <1 mm via a sieve, sprayed with the auxiliaries listed in Tab. 1, optionally dried at 150 ° C and in 300 g portions in steel cylindrical grinding bowls (volume 1000 ml) filled, 1800 g of steel balls of 15 mm in diameter were added and the grinding bowls were rotated on a roller block for 8 hours. After the grinding procedure had been completed, the percentage of different fractions was determined by sieve analysis and the particle size distribution was determined in this way. The results are recorded in Table 1 and make it clear that the addition of the auxiliaries according to the invention leads to an increased fine particle size of the ground material.

Example 17-28

The titanium (III) -containing slag B, which is described in more detail in Table 2, is brought to a uniform particle size of <1 mm using a sieve, with varying amounts of a 60% strength aqueous solution of a mixture of 1 part by weight. Monoisopropanolamine and 1 part by weight. Sprayed diisopropanolamine and dried at 150 ° C.

The slag prepared in this way was filled in quantities of 300 g into steel grinding bowls (volume 1000 ml), 1800 g of steel balls with a diameter of 15 mm were added and subjected to vibratory grinding on a vibration device (“Vibraton”, from Siebtechnik, Mühlheim-Speldorf). The results of these series of tests show that, with the same grinding time, the addition of the auxiliary agent increases the fine particle size or that the fine particle size, which is achieved after 3 hours of grinding time without auxiliary agents, is present in suitable amounts after 2 hours of grinding time when the grinding aid is used . This means that the grinding time is reduced by 33%.

Example 29-33

• 86,2% Ti0₂; 28,8% Ti(III) als Ti0₂ gerechnet; 7,7% Fe gesamt.

A slag containing titanium (III) of the following composition was used for grinding tests:

• 86.2% Ti0 ₂ ; 28.8% Ti (III) calculated as Ti0 ₂ ; 7.7% total Fe.

• 85,3% 40 µm;12,5% 40-90 µm; 2,2% 90 µm.

The sieve analysis of the starting material gave the following result:

• 85.3% 40 µm; 12.5% 40-90 µm; 2.2% 90 µm.

The slag characterized in this way was ground in two rows without or with the addition of 0.1% of a 1: 1 mixture of mono- and diisopropanolamine for different times in a vibrating ball mill in accordance with Example 17-28. The results are shown graphically in FIG. 2. They show that with the grinding aid according to the invention, a fine particle size of 100% 40 gm is achieved after 2 hours (A), while without the addition of auxiliary agents, even after 4 hours' residence time (h) in the mill, no adequate fine particle size is achieved (B).

Example 34-39

Equal amounts of a slag B from Examples 17-28 were reacted in a suitable apparatus for the purpose of digestion with an 88% sulfuric acid by diluting a 96% acid with water according to known methods and the SO _z emitted during the digestion reaction Quantity determined analytically. Experiments 34 and 35 serve as reference experiments and were carried out without the addition of auxiliary materials. Experiments 36 and 37 were carried out with the addition of 0.1% (based on ore) of the auxiliary according to the invention from Examples 17-28. Experiments 38 and 39 were carried out with the addition of 0.1% (based on ore) naphthenic acid in accordance with the teaching of US Pat. No. 2,437,164. Table 4 shows the results of this series of tests. They show that the addition of naphthenic acid leads to an almost 100% increase in SO ₂ emissions and an undesirably strong foam formation occurs. In contrast, Examples 36 and 37 behave with the aid according to the invention with respect to SO _z emission and foam formation like Reference Examples 34 and 35.

Examples 40-43

Equal amounts of a slag from Examples 29-33 were reacted in the apparatus of Examples 34-39 for the purpose of digestion with an 88% sulfuric acid by diluting oleum (25% free SO ₃ ) with a 65% sulfuric acid and the The amount of SO _z emitted during the digestion reaction was determined analytically. Experiments 40 and 41 serve as reference experiments and were run without the addition of auxiliary materials. Experiments 42 and 43 were carried out with the addition of 0.075% of a polydimethylsiloxane in the form of an aqueous emulsion (trade name: Bayer silicone oil emulsion H ^{@ -} average molecular weight 8000).

The results of this series of tests are summarized in Table 5. They show that the addition of polydimethylsiloxane does not lead to any deviations from the behavior of the reference examples.

Examples 44-45

A slag from Examples 29-33 is reacted in a suitable apparatus with an 88% sulfuric acid by diluting oleum (25% free SO ₃ ) with a 65% sulfuric acid. Test 44 was carried out with the addition of 0.1% mono- / diisopropanolamine (1: 1), test 45 with 0.1% naphthenic acid. After manufacture, the reaction mass was aged for 5 hours at 180 ° C., dissolved in water and the dissolved proportion of the TiO _{2 used} and the content of trivalent titanium in the solution were determined.

The results are summarized in Table 6 and show that when using naphthenic acid a factor 5-6 higher

Example 46

In the digestion apparatus described in more detail in FIG. 1, 318.6 g of a concentrated sulfuric acid with an H ₂ S0 ₄ content of 65.0% and 400 g of a ternary raw material mixture consisting of 80 g to a particle size of 88% <40 were placed µm ground IImenit, which has a Ti0 ₂ content of 60.0%, an iron content of 24.7% and an iron (III) content of 17.4%, 160 g ground to a grain size of 85% <40 µm Slag A, which has a Ti0 ₂ content of 85.3%, a titanium (III) content of 28.8% (calculated as Ti0 ₂ and based on slag) and an iron content of 7.7%, and 160 g to a grain size of 77.4% <40 microns ground slag B, which has a Ti0 ₂ content of 71.6%, a titanium (III) content of 9.2% (calculated as Ti0 ₂ and based on slag) and has an iron content of 9.9%.

3 minutes after switching on the air bath, which can be heated with 750 watts and serves to compensate for heat losses due to radiation, 426.0 g of oleum with an S0 ₃ concentration of 21.1% were started within 10 minutes by passing through 500 air / hour to start the digestion reaction added. The temperature of the air flow entered was tracked to the inside temperature of the vessel in order to avoid heat losses. The temperature-time profile of the digestion reaction is shown in FIG. 3. One can see the formation of a second pronounced maximum of the reaction temperature about 32 minutes after passing through the first maximum. The reaction mass originally solidified in point c liquefied again and finally solidified when point e was reached, with a spontaneous sharp rise in pressure in the reaction mass. At point c, part of the digestion mass was discharged from the reaction vessel.

The digestion product remaining in the vessel was aged in a drying cabinet at 180 ° C. for 5 hours and then ge by adding 800 ml of water at 70 ° C. in the course of 4 hours while passing 100 l of air per hour solves. There were 95.0% of the Ti0 _{2 used} in the solution. The average Ti (III) content of the solution was 2.2% of the dissolved TiO ₂ .

The example shows that the digestion reaction when using fine-particle ilmenite (expressed as a percentage <40 µm) together with larger-scale slags undesirably with formation of two temporally far apart maxima of the reaction temperature, a large delay in the time until the reaction mass is finally solidified and an undesirable one Pressure increase in the decomposition vessel takes place.

Example 47

The test procedure corresponded in all points to that of Example 46, with the difference that the ilmenite used had a grain size of between 75 μm and 90 μm to 100%. 4 shows the temperature over time. In contrast to Example 46, there is no second temperature maximum. The experiment was carried out without spontaneous pressure development in the digestion tank. After appropriate separation and dissolution of the reaction mass in water, 94.8% of the Ti0 _{2 used was} in solution. The average Ti (III) content of the solution was determined to be 7.2% of the dissolved TiO ₂ .

The example shows that the use of relatively coarsely divided ilmenite together with slags enables problem-free digestion behavior in discontinuous operation.

Example 48

The experimental procedure corresponded in all points to that of Examples 46 and 47, with the difference that the grain size of the ilmenite used was 100% in the range between 90 µm and 125 µm. The course of the reaction corresponded to that of Example 47. There were 94.2% of the TiO _{2 used} in solution with a Ti (III) content of 6.8% of the dissolved TiO ₂ . According to the invention, problem-free digestion behavior was also achieved when the ilmenite used was further coarsened.

Example 49

In the apparatus of Example 46, 315.5 g of a concentrated sulfuric acid with an H ₂ SO ₄ content of 65.0% and 400 g of a ternary raw material mixture consisting of 66.8 g to a grain size of 87.6% <were placed 40 μm ground ilmenite, which has a TiO ₂ content of 59.6%, an iron content of 24.4% and an iron (III) content of 17.2% and each 166.6 g of the two slags of Example 46 registered.

The procedure was continued as in Example 46 and the reaction was started with 429.3 g of oleum having an SO ₃ concentration of 21.8%. The temperature-time curve corresponded approximately to that of FIG. 3. Here, too, a spontaneous pressure increase occurred in the digestion vessel when the second temperature maximum was reached and the majority of the digestion mixture was discharged from the container. Collected parts of the reaction mass were aged and dissolved in accordance with Example 46. There were 93.2% of the Ti0 _{2 used} in solution. The average Ti (III) content was 6.1% of the dissolved Ti0 ₂ .

Example 49 serves as a comparative example for the subsequent experiments and, like Example 46, shows that when finely divided ilmenite is used together with relatively large-sized slags, an unfavorable course of the reaction is obtained.

Example 50

• 11 % < 40 µm,10% 40-75 µm, 7,8% 75-90 µm, 16,3% 90-125 µm, 55,1% 125-150 µm. Er war demnach relativ grossteiliger als die eingesetzten Schlacken. Der Temperatur-Zeit-Verlauf entsprach in etwa dem in Fig. 4, d.h. es trat nur 1 ausgeprägtes Temperaturmaximum auf. Es befanden sich 92,2% des eingesetzten Ti0₂ in Lösung. Der Ti(III)-Gehalt der Lösung lag bei 8,2% vom gelösten Ti0₂.

The procedure was as in Example 49, with the difference that the ilmenite used was characterized by the following grain size distribution:

• 11% <40 µm, 10% 40-75 µm, 7.8% 75-90 µm, 16.3% 90-125 µm, 55.1% 125-150 µm. It was therefore relatively larger than the slags used. The temperature-time curve corresponded approximately to that in FIG. 4, ie only 1 pronounced temperature maximum occurred. There were 92.2% of the Ti0 _{2 used} in solution. The Ti (III) content of the solution was 8.2% of the dissolved TiO ₂ .

Example 50 again shows that, according to the invention, the use of relatively coarsely divided ilmenite together with finely divided slags enables problem-free digestion behavior.

Example 51

The procedure was as in Example 49, with the difference that the slag A used was ground to 100% <40 μm in a ball vibrating mill and the slag B used was also ground to 100% <40 μm.

At 87.6% <40 µm, the ilmenite used was relatively coarser than the slags used.

A temperature-time curve corresponding to Fig. 5 was obtained, i.e. in comparison to Example 49, FIG. 3, the second temperature maximum was only hinted at and there was no spontaneous pressure increase in the reaction vessel.

After further processing, 96.7% of the Ti0 _{2 used was found} in the solution. The titanium (III) content was 7.5% of the dissolved Ti0 ₂ .

Example 51 shows that it is possible to obtain digestion behavior without problems even with relatively fine-particle ilmenite, as long as it is ensured according to the invention that the slags used are relatively fine-particle than the ilmenite or, conversely, the ilmenite used is relatively larger-scale than the slags used.

Example 52

• a) A titanium slag of the following composition - 71.6% Ti0 ₂ (of which 9.2% as Ti (III), 7.7% Fe - is in a continuous ball mill ground with pneumatic discharge. Before entering the mill, the raw ore is 0.01% of a mixture of 1 part by weight. Monoisopropanolamine and 1 part by weight. Diisopropanolamine added. The ground ore deposited in a cyclone has a fineness of 89% less than 40 µm. The throughput of the mill is determined to be 9.01 to / h.
• b) A titanium slag corresponding to Example 52a) was subjected to grinding under the same conditions, with the difference that no auxiliary agent was added to the raw ore before the grinding. The ground ore deposited has a fineness of 87% less than 40 µm. The throughput of the mill was determined to be 7.83 to / h. It follows that the addition of 0.01% mono- / diisopropanolamine with the same to better fineness has increased the throughput by 15%.

It becomes clear that even the addition of the smallest quantities leads to a great improvement in throughput.

Claims (10)

1. Process for the preparation of a hydrolysable titanyl sulphate solution from mixtures of previously ground ilmeniteand titanium(III)-containing raw materials, digestion of the raw material mixtures with sulphuric acid and dissolution of the solidified reaction masses in an aqueous solvent, characterised in that the titanium(III)-containing raw materials are ground in the presence of organic auxiliaries from the group comprising the alkanolamines and/or polysiloxanes.

2. Process according to Claim 1, characterised in that the titanium(III)-containing raw materials are titanium(III)-containing slags.

3. Process according to one of Claims 1 or 2, characterised in that the alkanolamine is a monoisopropanolamine and/or a diisopropanolamine and/or a triisopropanolamine.

4. Process according to one of Claims 1 to 3, characterised in that the polysiloxane is a long- chain and/or branched alkyl-, acryl-, cycloalkyl- and/or hydroxyl-substituted polysiloxane.

5. Process according to Claim 4, characterised in that the polysiloxane is a polydimethylsiloxane.

6. Process according to one of Claims 1 to 5, characterised in that the organic auxiliaries are used in the form of aqueous solutions and/or emulsions.

7. Process according to one of Claims 1 to 6, characterised in that the organic auxiliaries are used in quantities of 0.002 to 0.5% by weight, based on the mixture used.

8. Process according to one of Claims 1 to 7, characterised in that the organic auxiliaries are used in quantities of 0.005 to 0.15% by weight, based on the mixture used.

9. Process according to one of Claims 1 to 8, characterised in that the ilmenite raw materials used for the digestion are, with respect to their average particle size, relatively more coarsely divided than the titanium(III)-containing raw materials used.

10. Process according to Claim 9, characterised in that when using ilmenite raw materials with an average particle size of 0-90% smaller than 40 ₁₁m titanium(III)-containing raw materials with an average particle size of 91-100% smaller than 40 µm are used and when using ilmenite raw materials with an average particle size of 0-60% smaller than 40 µm titanium(III)-containing raw materials with an average particle size of 65-100% smaller than 40 µm are used.

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