FI71544B - FOERFARANDE FOER FRAMSTAELLNING AV TITANSULFATLOESNING - Google Patents

Description

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The present invention relates to a process for preparing a titanium sulphate solution. The titanium dioxide pigment can be prepared from the titanium sulfate solution prepared by the process of the invention by hydrolysis.

10 Titanium dioxide is a well-known material with desirable pigment properties and is useful in paint and coating compositions and plastic materials. Several different processes are known for producing a titanium dioxide material, for example, a sulfate process and a chloride process.

Typically, in a sulfate process for the production of titanium compounds, a titanium-containing material such as ilmenite ore, including solid ilmenite, ilmenite sand, and titanium-20-containing or furnace slag, is reacted with concentrated sulfuric acid (e.g., 90-96% sulfuric acid). The reaction is sometimes referred to as "extraction" or "ore extraction". The extraction reaction between the titanium-containing material and concentrated sulfuric acid is exothermic in nature and progresses very rapidly. Typically, the titanium-containing material and concentrated sulfuric acid are placed in a reaction vessel called an extraction tank. Water is usually added to the extraction tank to initiate and accelerate the acid-ore reaction under the influence of the heat of dilution of the acid, resulting in vigorous boiling of the aqueous-acid solution at about 100-190 ° C and development of very large amounts of water vapor and vapor particles. As the vigorous reaction progresses, the water evaporates and the reaction mass becomes solid; the reaction ends in the solid phase at a temperature of approximately 2,71544 at 18 ° C. The solid reaction mass, referred to as the "cake", is allowed to cool. The solid cake is then dissolved in water or dilute acid to give a solution of sulfate salts of iron, titanium and other trace metals in the titanium-containing material. The extraction operation is a batch process performed in one and the same extraction tank. Use as many extraction tanks as necessary according to the desired capacity of the manufacturing plant to produce the titanium sulfate solution.

The sulphate solution obtained after extraction (containing iron and titanium salts) is further treated by known measures to remove ferrous sulphate, commonly referred to as "viht-15 Rilli", to obtain a titanyl sulphate solution which, on hydrolysis, produces hydrated titanium dioxide. Titanium dioxide hydrate is usually subjected to a calcination treatment in a suitable incinerator to remove water of hydration and provide an unhydrated titanium dioxide pigment. The above process is described in more detail in, for example, U.S. Patent Nos. 1,504,672, 3,615,204 and 3,071,439.

The sulfate process for the preparation of titanium compounds described above has several environmental disadvantages. For example, the violent reaction that takes place in extraction tanks leads to undesired emission problems. Solutions of dilute sulfuric acid, commonly referred to as "spent acid", resulting from the removal of viqurill and hydrolysis of titanyl sulfate, also pose serious disposal problems because large amounts of such spent oxygen cannot be recycled to an extraction tank using concentrated sulfuric acid or regenerated.

A new sulphate process for the preparation of titanium-35 compounds has now been developed which substantially avoids 71544 or eliminates the above-mentioned disadvantages of the complete sulphate process. As used herein, the term titanium sulfate is used interchangeably to denote sulfate salts of titanium, such as thionyl sulfate and thian (3) sulfate.

The invention relates to a process for preparing a titanium sulphate solution, which process is characterized in that a) a titanium-containing material in an amount of about 10-400% greater than the stoichiometric amount required to react with sulfuric acid to form titanium sulphate 1Q is reacted with b) a dilute sulfuric acid solution is about 25-60% by weight based on the total weight of the solution, the reaction mixture obtained at a temperature below about 140 ° C is cooled to a temperature below about 110 ° C without precipitating reaction products to form a reaction mixture containing titanium sulfate, and insoluble solids are separated to form a titanium sulfate solution.

The process according to the invention can be applied in the production of titanium dioxide as follows: 1) a) a titanium-containing material in an amount of about 10-400% greater than the stoichiometric amount required to react with sulfuric acid to form titanium sulfate is reacted with b) a dilute sulfuric acid solution 25% is about 25-60% by weight based on the total weight of the solution, the reaction mixture obtained at a temperature below about 140 ° C (2) is cooled to a temperature below about 110 ° C without precipitating the reaction products; (3) insoluble solids and ferrous sulfate are removed from the reaction mixture to give a titanium sulfate-30 solution; (4) hydrolyzing the titanium sulfate solution to form titanium dioxide hydrate; (5) titanium dioxide hydrate is calcined to provide titanium dioxide and (6) titanium dioxide is recovered.

The invention can also be applied in a continuous process for the preparation of titanium dioxide 35, in which 71544 1) a) a titanium-containing material in an amount of about 10-400% greater than the stoichiometric amount required to react with sulfuric acid to form titanium sulfate is reacted 5 b) with a dilute sulfuric acid solution

the concentration is about 25-60% by weight based on the total weight of the solution, at a temperature below about 140 ° C

2) the resulting reaction mixture is cooled to a temperature of about 110 ° C in a second reaction vessel without mixing the reaction products; 3) unreacted titanium-containing material is separated from the reaction mixture to give a solution of ferrous sulfate and titanium sulfate 4) ferrous sulfate is removed from a solution of ferrous sulfate and titanium sulfate to give a solution of titanium sulfate to form titanium oxide 7) titanium dioxide is recovered

The accompanying figure shows an application of the present invention in a continuous titanium dioxide production process.

In the process of the invention, it is surprising that the titanium-containing material can be reacted completely in the liquid phase without the need for a separate reduction step, with dilute sulfuric acid to provide a stable 3Q hydrolyzable titanium sulfate solution that can be used to prepare titanium compounds and titanium dioxide pigments.

The extraction reaction is performed using a titanium-containing material. As used herein, the term titanium-containing material 35 means a material that contains recoverable titanium when treated by the process of the invention. Such materials include, for example, titanium-containing slag, kiln slag, ilmenite ores such as magnetic ilmenite and massive ilmenite, and ilmenite sands.

The extraction reaction is carried out using a sufficient amount of titanium-containing material to provide an excess of material of about 10-400% above the stoichiometric amount. This amount can also be shown to be 1.1 to 5 times the stoichiometric amount. The following formula shows the stoichiometry of the extraction reaction:

FeTiO 3 + 2H 2 SO 4 -> TiO 5 SO 4 + FeSC> 4 + 2H 2 O The use of excess titanium-containing material in the extraction reaction is efficient and desirable to achieve a successful and operational process in accordance with this invention without the need to grind excess ore.

The surface area of the titanium-containing material preferably varies between about 0.05 and 0.6 m / cm. Ore with a larger surface area could be used, but it does not provide any benefit due to increased grinding costs. As mentioned above, an excess of titanium-containing material of about 10-400% above the stoichiometric amount required to react with sulfuric acid should be used in the process extraction reaction. The use of smaller amounts of mixture results in unacceptably low reaction rates and long processing times so that the process becomes uneconomical. The use of larger amounts of material than recommended is undesirable due to the greatly reduced flowability of the reaction mixture and the need to recycle large amounts of unreacted titanium-containing material to the extraction reactors. Unexpectedly, for example, it has been found that doubling the amount of titanium-containing material, such as Maclntyre-35 ore, above the stoichiometric amount required to react with dilute sulfuric acid 6,71544 increases the reaction rate by at least about 10-fold in the last extractor. It should be noted that the reaction rates vary depending on the source of titanium iron material used during the extraction.

The concentration of sulfuric acid used in the process according to the invention should be between about 25 and 60% by weight, based on the total weight of the acid solution. Less than about 25 weights; n acid concentration is undesirable because hydrolysis of titanium dioxide occurs during the extraction reaction and in conjunction with the use of such acids. Premature hydrolysis of titanium salt solutions prevents the formation of pigment-grade titanium dioxide at a later stage in the process. The use of an acid with a concentration greater than about 60% by weight is also undesirable because 15 (1). the resulting reaction solution is more viscous and more difficult to handle, (2) spent acid cannot be recycled economically unless the used acid is concentrated, which unnecessarily increases operating costs, and (3) higher concentration of reaction products in solution promotes ferrous sulfate mono-hydrate and recoverable titanyl sulfate. The presence of ferrous sulphate monohydrate makes the unladen weight separation inefficient and difficult to remove by filtration.

The operating conditions of the process for carrying out the extraction reaction can be easily adjusted depending on the concentration of dilute sulfuric acid and the excess titanium iron-containing material used in each case to obtain optimum process operation. To illustrate this, the use of dilute sulfuric acid at a low concentration, e.g. less than 40% by weight, initially requires process operation at the lower end of the recommended temperature range due to the lower boiling point of the dilute sulfuric acid. It is desirable to increase the amount of titanium-containing material used to extract as much material as possible in the first 71544 extraction reactor, at which point the operating temperature and reaction rate are usually higher. As mentioned below, the temperature in the subsequent extraction reactors is kept at a lower level than in the first extraction reactor and, overall, must be lowered to prevent or avoid premature hydrolysis of the titanium salt solution.

The temperature at which the extraction reaction takes place is below n, 140 ° C and preferably, from 55 ° C to the prohibition point of the reaction solution, i.e. between n-55-140 ° C. The choice of too low a temperature in the extraction reaction should be avoided, as the extraction reaction proceeds too slowly and thus requires an extended residence time of the reagents in the extraction reactor. Prolonged residence times should also be avoided to avoid the risk of formation of unwanted nuclei in the reaction solution due to premature hydrolysis of the titanium salt. The choice of temperatures above 140 ° C is not recommended because the titanium salt hydrolyzes at much higher rates at higher temperatures.

It should be avoided to carry out the extraction reaction below about 55 ° C, since the reaction products begin to precipitate from solution and the viscosity of the reaction mixture increases, which makes the removal of unreacted solids very difficult. The recommended operating temperature for carrying out the extraction reaction is between about 70-110 ° C. It should be noted that the extraction reaction of the process of this invention may be carried out as a batch reaction, e.g., in a reaction vessel from which the reaction mixture, after the extraction reaction has progressed to the desired extent, is removed and further processed in other vessels.

In a preferred embodiment of the process according to the invention, the extraction reaction is carried out continuously in at least two reaction vessels and in which the titanium-containing material and dilute sulfuric acid are made to flow in parallel.

When the process is carried out continuously, it is preferable 71544 to use two or more extraction reactors. The total number of extractors depends on the ease of controlling the reaction, the production of the plant and the process treatment *

When performing the extraction reaction in two extraction reactors or stages, it is recommended that the first extraction device be kept below about 140 ° C and preferably below about 110 ° C and the second extraction device be kept below about 100 ° C, preferably below at about 75 ° C.

When performing the extraction reaction in three extraction reactors or stages, it is recommended that the first extraction device be kept below nf at 140 ° C and preferably below 110 ° C, the second extraction device is kept below about 110 ° C and preferably below about 100 ° C. ° C and the third extractor is kept below about 80 ° C and preferably below 15 n, 75 ° C.

When performing the extraction reaction in four extraction reactors or stages, it is recommended that the first extraction device be kept below about 140 ° C and preferably below about 110 ° C, the second extraction device be kept below n.

At 110 ° C and preferably below about 90 ° C, the third extraction device is kept below about 100 ° C and preferably below about 86 ° C and the fourth extraction device is kept below about 90 ° C: and preferably below about 75 ° C.

When performing the extraction reaction in five extraction reactors or stages, it is recommended that the first extraction device be kept below about 140 ° C and preferably below about 110 ° C, the second extraction device be kept below about 110 ° C and preferably below at about 90 ° C, the third extractor is kept below about 100 ° C and preferably below 30 n, at 85 ° C ', the fourth extractor is kept below about 90 ° C and preferably below about 80 ° C. And the fifth extractor is kept below about 85 ° C and preferably below about 75 ° C.

All of the above extractor temperatures can be varied depending on the desired yield and the reaction times used in each of the 35 steps. An essential feature of the process according to the invention is that the temperature of the extraction reaction is lowered as the reaction proceeds in order to prevent or avoid premature hydrolysis of the titanium salt solutions obtained. Premature hydrolysis of the titanium salt solution prevents the formation of titanium dioxide, a pigment grade.

The duration of the extraction reaction in the extraction apparatus is controlled by the conversion of the titanium-containing material or by the optimum degree of extraction in question. stage. In general, it is advisable to extract or react as much titanium-containing material as possible in the first extraction reactor or stage with the highest temperature to prevent hydrolysis of the titanium sulfate in solution. For example, in a continuous, multi-stage system using Maclntyre ore as a source of titanium-containing material, it is sometimes possible to extract in the first stage up to about 90% by weight of the sto-20 kilometric amount of ore charged to the process, excluding excess ore. Preferably about 30-80% and most preferably about 60-80% by weight of the stoichiometric amount of ore is extracted in the first step except for the excess ore. The conversion is measured by the amount of reaction completed, calculated from the stoichiometric amount of titanium-containing material used.

The temperature is used to control the extraction reaction, preferably by monitoring the ratio of active acid to titanium in the reaction solution. This ratio is an indication of the con-30 version or extraction rate. The expression "active acid" means the total amount of free acid in the reaction solution and the acid which is combined with titanium in the reaction solution. The ratio of active acid to titanium dioxide (active acid: titanium dioxide) is calculated as the sum of both the free acid in solution and the acid combined with titanium in solution 71544 10 divided by the titanium in solution (calculated as TiO 2). The active acid content of the solution can be determined, for example, by titrating a selected sample (by weighing or piping technique) with a 0.5 N base solution (NaOH) to a pH of 5 in a solution buffered with 4.0 barium chloride / ammonium chloride. Titration gives the concentration of the free acid and the acid which is associated with TiO2 and is called the active acid. To illustrate this, 60 ml of a buffer solution containing 75 g / l barium chloride and 250 g / l ammonium chloride is added to a beaker containing the sample in question and diluted with water to 250 ml and titrated with 0.5 N base to the methyl orange end point.

In the batch process, the concentration of active acid can vary widely and is critical other than the extent to which the extraction and reduction take place in the liquid phase. In a continuous process, the active acid is allowed to drop from infinity at the beginning of the reaction to between 1.50 and 7.0 at the end of the reaction, depending on the extraction conditions. Typically, the ratio of 20 active acids to TiO 2 ranges from 2.0 to 3.5. As the amount of active acid decreases, the stability of the titanyl sulfate solution against hydrolysis decreases. In general, the temperature of the reaction solution should be kept below about 140 ° C and preferably below about 110 ° C when the ratio of active acid to titanium (calculated as titanium dioxide) drops to about 2.0. To illustrate this in a two-step extraction process, the temperature of the reaction solution in the first stage of the extraction reaction or in the extraction apparatus should be kept below about 140 ° C, e.g. 110 ° C until the ratio of active acid to titanium dioxide in the reaction solution decreases to about 3.0. below about 100 ° C, e.g. 70 ° C. In contrast, in a three-step extraction process, the temperature of the first step is maintained at about 100 ° C to provide a reaction mixture in which the ratio of active acid to titanium dioxide in the reaction solution is between about 2.5 and 3.0 11 71544 and then the reaction is carried out in a second step n At a temperature of 100 ° C to obtain a reaction mixture in which the ratio of active acid to titanium dioxide in the reaction solution is between about 2.2 and 2.5. The reaction can then be completed in a third step at a temperature below about 80 ° C to give a reaction mixture in which the ratio of active acid to titanium dioxide in the reaction solution is about 2.0.

After completion of the extraction reaction, the resulting reaction mixture containing titanium sulfate, ferrous sulfate and a trace element derived from a titanium-containing material can be treated to recover a titanium sulfate solution for the preparation of titanium compounds or treated according to conventional sulfate process techniques to prepare titanium.

Reference is now made to the figure showing the production of titanium dioxide using a multi-stage reactor system. Reference numeral 10 shows an extraction reactor. Titanium-containing material such as ilmenite ore is fed to the extraction reactor 10 from the ore storage tank 11. Dilute sulfuric acid having a concentration of about 25-60% by weight based on the total weight of the acid solution is fed to the strong acid source 12 (96% by weight). ) from the mixture, either in combination with recycled acid (15-45% by weight) or water directly to the extraction reactor 10. The ilmenite ore and dilute sulfuric acid in the extraction reactor 10 are continuously stirred at a temperature not exceeding the boiling point of the reaction solution in the reactor.

The reagents in the extraction reactor 10 are maintained at a temperature below about 140 ° C and preferably between n.

55-140 ° C. More specifically, the reagents in the extraction reactor 10 are preferably kept at 110 ° C. The extraction reactor 10 can be maintained at any suitable pressure; normal pressure is recommended for economic reasons.

35 When the reaction mixture is continuously treated in the three-stage extraction system shown, it is transferred from the extraction reactor 10 to a conventional separation device 13, e.g. a filter or cyclone separator, in which part or all of the can be continuously transferred from the extraction reactor 10 to the extraction reactor 15, whereby it does not involve the recycling of unreacted ilmenite ore to the extraction reactor 10.

The reaction solution in the extraction reactor 15 is preferably kept at a somewhat lower temperature than the temperature of the extraction reactor 10. For example, the reaction mixture in the extraction reactor 15 is maintained at about 100 ° C. The temperature control in the extraction reactor 15 can be implemented by adding recycled acid or water.

The pressure in the extraction reactor 15 is preferably normal pressure, but higher pressures may be used if desired.

The reaction mixture can be continuously transferred from the extraction reactor 15 to a conventional separation device 16, e.g.

20 to a filter or cyclone separator in which the unreacted ilmenite ore is partially or completely separated and recycled through the recycle tube 17 back to the extraction reactor 15. Alternatively, the reaction mixture can be continuously transferred from the extraction reactor 15 to the extraction reactor 18, 25 without recirculation of unreacted ilmenite ore.

It is preferred to maintain the reaction mixture in the extraction reactor 18 at about 70 ° C and normal pressure.

The reaction mixture from the extraction reactor 18 is continuously fed to a suitable separation device 19, e.g.

a filter or self-weight separator (or several such arranged in series and / or in parallel) in which the unreacted ilmenite ore is separated from the liquid reaction product. Excess or unreacted ilmenite is circulated through lines 21 and 21 'to one or both of the extraction reactors 18 and / or 10. The liquid reaction product from the separation device 19 is passed to a settling device 20, e.g. a conventional, settling device 71544 13

Q

or a LAMEL - * apparatus in which a side rock or other unwanted solid material is removed from the reaction product.

As mentioned above, the extraction reaction is carried out in 5 extraction reactors 10, 15 and 18. However, the extraction reaction does not have to be carried out in three extraction reactors. In fact, the process can be carried out batchwise using a single Yea extraction reactor. However, it is recommended to use two or more extraction tanks to carry out the process continuously. When only two extraction reactors are used, the temperature of the second extraction reactor, such as the extraction reactor 15, can be set to a lower temperature, for example 70 ° C.

Each extraction reactor should also be equipped with 15 suitable stirring means, indicated at 9 in the figure, to keep the reagents and the reaction solution well mixed.

A suitable reducing agent, for example iron or titanium (3) sulphate from tank 22 may be added to the extraction reactor 10 or the extraction reactor 15 or both reactors for the purpose of reducing the trivalent Ferri ion in the extraction solution to a divalent ferroion. The presence of the reduced form prevents contamination of the subsequently obtained titanium hydrate with ferric salts. The amount of reducing agent added to the reaction solution in the extraction equipment 25 depends on the amount of Ferri ion in the ilmenite ore fed. In general, about 3-8% by weight of the reducing agent, based on the total weight of the reacted ilmenite ore, is sufficient to provide satisfactory results in a process using ilmenite ore containing 5-13% Ferri ion. The addition of a reducing agent such as a track has another advantageous effect in that it accelerates the rate of the extraction reaction. Thus, with this measure, it is possible to avoid a separate reduction step to the extraction solution, which would otherwise be necessary. The reducing agent can be added at any stage of the extraction operation.

The amount of reducing agent used is selected so that not only all the trivalent iron in the ilmenite ore is converted to the divalent state, but also part of the titanium in the reaction solution is reduced to the trivalent state to obtain a titanium sulfate solution for hydrolysis of titanium containing trivalent. The presence of trivalent titanium prevents the formation of ferric iron that would be adsorbed on the titanium dioxide particles in the next hydrolysis step of the process. It has been ha-XO found that the accelerating effect of iron on the rate of the extraction reaction increases as the particle size of iron decreases.

A certain amount of metal sulfates, e.g., ferrous sulfate monohydrate, usually precipitates during the extraction reaction without any noticeable deterioration in the fluidity of the reaction mixture. The ferrous sulfate monohydrate can be easily dissolved at the end of the extraction reaction by adding water.

At least a portion of the water can be replaced with a titanium sulfate solution liberated from a large portion of the ferrous sulfate (by crystallization and separation of ferrous sulfate-20 heptahydrate at a later stage in the process described below). By this measure, the addition of excess water to the system can be minimized or avoided. Usually the excess water has to be removed at a later stage of the process, e.g. by evaporation.

Water or a solution of water and titanium sulfate may be added to the reaction solution in the last extraction tank or at a suitable point between the last extraction tank and the separator 19 to provide cooling.

The resulting solution containing titanium sulfate, ferrous sulfate, and minor amounts of substances derived from ilmenite ore can be recovered and treated to prepare titanium compounds. Alternatively, the solution may be treated to produce a titanium dioxide pigment, whereby the reaction solution is passed to a settling device to remove solids from the solution.

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In the preparation of titanium dioxide, the reaction solution is then passed from a settling apparatus 20 to a crystallization apparatus 23, where vihtrill (i.e. ferrous sulfate heptahydrate) is crystallized and removed by known process steps.

5 For example, the solution is cooled in a continuous or batch vacuum crystallizer to about 10-20 ° C by placing it under a vacuum of 23.5 mmHg to form large crystals of vihtrill (FeSO 4 - 7K 2 O) which can be easily filtered through a drum or table filter. The Vihtrill cake can be washed to recover Liu-10 molten titanium. The reaction solution from the filter can be concentrated by known measures, e.g. by evaporation before it is subjected to hydrolysis. The reaction solution can also be clarified either before or after crystallization and removal of ferrous sulfate heptahydrate. The clarification topic before crystallization is preferred if it is desired to obtain highly pure ferrous sulfate heptahydrate, which can be further processed, for example, to prepare reagents used for the purification of water and sewage.

The reaction solution is preferably subjected to a fine filtration step before hydrolysis. After removal of the ferrous sulphate heptahydrate and clarification and fine filtration of the reaction solution, if necessary, a titanium sulphate solution with a preferred FerTiCl 2 ratio is obtained and can be directly hydrolysed or optionally evaporated by known means in a vacuum evaporator to the desired TiO 2.

The reaction solution from crystallization 23 consists of a solution of titanyl sulfate (TiOSO 2), which is fed to a hydrolysis apparatus 24, where the titanyl sulfate is hydrolyzed by known process steps to obtain titanium dioxide hydrate. In particular, the titanyl sulfate solution is hydrolyzed to provide insoluble titanium dioxide hydrate by diluting the titanyl sulfate solution with water at elevated temperatures.

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For example, a predetermined amount of titanyl sulfate solution, preferably with a titanium dioxide content of more than 200 g / l, is preheated to more than 90 ° C and added with stirring to water at substantially the same temperature and in a ratio of 3-4 1/2 parts of solution per part of water. The solution is brought to a boil and titanium dioxide in the form of colloidal particles precipitates; the colloidal particles flocculate to form a filterable titanium dioxide hydrate. The method and means for performing the hydrolysis step are well known in the art and are described, for example, in U.S. Patent Nos. 851,487 and 3,071,439.

After hydrolysis, the titanium dioxide hydrate is filtered through a filter device 25, such as a Moore filter, and the resulting filter cake is fed to a calciner 26 where it is heated in a known manner to remove hydration water and adsorbed sulfuric acid to give titanium dioxide as a suitable pigment.

A significant advantage of the process according to the invention is that the problem of "spent acid" disposal can be reduced or even eliminated, a problem which is characteristic of the conventional sulphate process used for the production of titanium dioxide pigment. In particular, the spent acid from the extraction, crystallization and hydrolysis steps of the process is reprocessed or recycled for use in carrying out the extraction reaction with ilmenite ore. Thus, the process of the invention may be free or substantially free of spent waste acid.

To illustrate this, the spent acid from the filter 25 is passed through line 27 and returned to the extraction reactor 10. If desired, the spent acid from the filter 25 can be concentrated, for example by evaporation, in a known manner in the concentrator 28 before being returned to the extraction reactor 10.

17 71544

Another significant advantage of the process of the invention is that the recycled spent acid can be fed directly to any or all of the extraction reactors to control the temperature in each extraction reactor. The above provides an effortless and efficient way to balance and control the reaction temperature between reactors.

The principle and practice of the present invention are illustrated in the following examples, in which the specified proportions 10 and percentages are by weight unless otherwise indicated. Conversions are measured by the amount of reaction that has taken place for the stoichiometric amount of treated ore.

Area was measured by the sedimentation method described by Jacobsen, A.E. and Sullivan, W.F., 15 "Method for Particle Size Distribution for the Entire

Subsieve Range, ”Vol. 19, page 855 in Analytical Chemistry (November 1947).

Example 1 800 g of ilmenite ore (Maclntyre ore) with an area of 0.39 m / cm was charged to an extraction reaction vessel, 1.16 liters of 43% by weight sulfuric acid was added to the reaction vessel. The temperature of the reagents was raised to 108 ° C with heating under constant agitation with a stirrer made of Teflon material. After 50 minutes, a 15 cm sample of the reaction mixture was filtered by gravity through glass filter paper into a 100 ml polypropylene bottle. The filtrate was analyzed for active acid and titanium (expressed as TiCl 4). The active acid content of 30 was 430 g / l, giving a ratio of active acid to titanium of 7: 1.

The conversion of the reaction was determined after about 1/4 hour by analyzing a sample of the reaction solution. The analyzed acid had an active acid content of 396.9 g / l and a titanium content of 78.5 g / l (TiCl 2).

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After about 1 1/4 hours, powdered iron was added to the reaction vessel to provide a reducing agent for the ferric iron content of the reaction mixture.

After about 1 3/4 hours, the temperature of the reaction mixture 5 was lowered to 70 ° C by placing the reaction vessel in a cooling water tray. Analysis of a portion of the reaction solution after cooling and removal of insoluble solids showed an active acid content of 353.3 g / l I 2 SO 4 and a titanium content of 89.25 g / l (TiCl 4), giving a ratio of active acid to titanium of 3.96.

The reaction mixture was maintained at 70-74 ° C for about 15 hours. The reaction mixture was cooled to about 50 ° C to quench the reaction, filtered to remove insoluble solids, and analyzed for active acid and titanium content. The active acid content was 275.8 g / l and the titanium content was 136.2 g / l (TiCl 2), giving a ratio of 2.025 active acid to titanium.

The reaction solution was stable and suitable for hydrolysis to prepare the titanium dioxide pigment. The titanium dioxide pigment can be prepared from the reaction solution using a technique known per se.

Example 2 A two-stage system was constructed consisting of a heated stirred five liter first stage reactor with an overflow to a heated, stirred 25 liter second stage reactor. Maclntyre ilmenite ore with a particle size distribution of 30 (U.S. Standard sieves):

Mesh weight% +100 1.2 + 200-100 35.8 35 + 325-200 23.0 71544 + 400-325 6.0 -400 34.0 and containing 46.8% TiCl 2 were continuously fed to the first stage at a rate of 3.78 g / min. A dilute sulfuric acid solution having the following analysis: ^ 29.9% free H 2 SO 4 1.4% titanium (3) sulfate 3.3% soluble titanium (as TiO 2) was also fed to the first stage at a rate of 12 r5 ml / min. Titanium (3) sulfate was added to the reaction vessel to provide a reducing agent for the ferric iron content of the reaction mixture. Both steps were initially charged with sufficient ore to provide a 100% excess over stoichiometric amount. Unreacted ore flowing over from the second stage was recycled to the first stage to maintain this excess ore in the system. The first stage reactor was adjusted to 106 ° C, while the second stage reactor was adjusted to 71 ° C. The residence times of the first and second stages were about 6.8 hours and 34.2 hours, respectively.

After sufficient time to equilibrate, it was found that 54.2% of the TiO2 in the ore feed had reacted in the first stage and 28.2% had reacted in the second stage. A total conversion of 82.4% was achieved in these two stages. Analysis of the final product was: 7 9 9% soluble titanium (TiCl 2) 9.0% free H 2 SO 4 0.3% titanium (3) sulfate (as TiO 2)

Example 3 The system described in Example 2 was operated at the following feed rates to the first stage reactor: 3.27 g / min ilmenite ore (46.8% TiO 2) 12.28 g / min dilute sulfuric acid solution containing 42.9% free H 2 SO 4. and no titanium (3) sulfate at all.

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Powdered iron was also fed to the first stage at a rate of 0.19 g / min. Powdered iron was added to the reaction vessel to provide a reducing agent to the ferric iron content of the reaction mixture.

An excess of 100% ore over the stoichiometric amount was maintained in the system as in Example 2. The first stage reactor was adjusted to 106 ° C and the second stage to 72 ° C. The residence times of the first and second phases were about 9.5 hours and 47.1 hours, respectively. When equilibrium was reached, it was found that 73.9% of the TiO 2 in the ore feed had reacted in the first stage and 20.9% in the second stage.

With these two steps, an overall conversion of 94.9% was achieved. Analysis of the final product was: 8.9% soluble titanium (as TiO 2) 8.8% free H 2 SO 4 0.1% titanium (3) sulfate (as TiO 2)

Example 4 A reaction acid solution containing 41.4% by weight of sulfuric acid was prepared by combining 96.5% by weight of sulfuric acid, spent sulfuric acid solution containing 16.32% by weight of sulfuric acid, and water in a reaction vessel. The reaction acid was heated to 100 ° C with constant stirring.

25,130 g of ilmenite ore, twice a stoichiometric amount, was heated to 100 ° C and charged to a reaction vessel. The temperature of the reaction mixture was then raised to about 108 ° C and held for 10.5 hours. Samples of the reaction mixture were taken periodically and analyzed.

Analysis of a sample taken about 45 minutes after the addition of ilmenite ore showed an active acid content of 35.90% and a titanium content of 1.72% (TiO 2), giving a ratio of active acid to titanium of 20.87.

Analysis of a sample taken after 10.5 hours at about 108 ° C showed an active acid content of 23.10% and a titanium content of 7.49% (TiCl 2), giving a ratio of active acid to titanium of 3 , 08.

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Example 5 This example illustrates multi-step, continuous extraction processes in which a 41.7% sulfuric acid solution is reacted with a 100% stoichiometric excess of 5 Maclntyre ilmenite ore with a TiCl 2 content of 46.8% in the presence of a powdered iron reducing agent in an amount of is 5% by weight of the reacted ilmenite ore. Table I shows the temperature, residence time and conversion conditions of the extractor for the extractors in 10 different multi-stage extraction processes.

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Claims (1)

A process for preparing a titanium sulphate solution by treating a titanium-containing material with dilute sulfuric acid, characterized in that a) a titanium-containing material in an amount of about 10-400% greater than the stoichiometric amount required to react with sulfuric acid to form titanium sulphate is reacted with a dilute sulfuric acid solution having a concentration of about 25-60% by weight based on the total weight of the solution, at a temperature below about 140 ° C, preferably at 55-140 ° C, the reaction mixture is cooled to a temperature below about 110 ° C, preferably below 75 ° To C without precipitating reaction products to form a reaction mixture containing titanium sulfate, and insoluble solids are separated to form a titanium sulfate solution.