RU2080396C1 - Method for agglomeration of fine-grain titaniferous mineral - Google Patents

Abstract

A process for increasing the particle size of fines of a titaniferous mineral containing more than 45 % by weight of titanium. The process comprises mixing the fines with a binding agent and water to produce an agglomerate. The agglomerate is then dried and sintered.

Description

The invention relates to agglomerates of a titanium-containing material suitable for producing Ti Cl ₄ .

In known processes of a material with a high content of titanium dioxide (over 85% TiO ₂ are the preferred raw materials for the production of TiCl ₄ , which are the subject of description based on the particle size of the materials and the content of some impurities of the elements.

TiCl ₄ is a low boiling point liquid that can be purified by distillation or chemical methods, after which it can be burnt in oxygen to generate TiO ₂ pigment and chlorine gas, reacted with magnesium or electrolyzed to produce metallic titanium.

The raw material is a titanium-containing mineral with a particle size in the range of 100 to 300 μm fed into the pseudo-fluidized bed reactor, where it is subjected to reductive chlorination at temperatures in the range of 900 to 1000 ^o C. Petroleum coke or similar material with a large number of carbon atoms is added to the layer as fuel and how reducing agent. Oxygen may be added to the inlet stream to maintain reaction temperatures. The resulting TiCl ₄ exits the reactor in gaseous form together with gaseous chlorides of impurity elements and trapped small solid particles from the pseudo-fluid layer. These gases are purified from solid particles and condense. The final TiCl ₄ is purified by distillation or by chemical methods.

In the chlorination step, most of the metallic impurities form volatile chlorides, which exit the reactor in a gaseous stream of TiCl ₄ . However, alkali and alkaline earth metals form relatively non-volatile chlorides, which are in a liquid state at reaction temperatures and, therefore, tend to form agglomerated masses in the layer to the level of potential shutdown of the process. Therefore, process operators typically impose strict restrictions on the content of these elements in raw materials. Impurities, such as iron, cause economic damage to the process in that they consume coke to restore them and, more importantly, the expensive reagent chlorine, which is released along with iron chloride compounds. Silicon and aluminum are also partially chlorinated in this process, leading to excessive consumption of chlorine. Aluminum chloride compounds are also a source of corrosion problems in process equipment.

 As the chlorination of the mineral particle continues, it decreases in size until it reaches a point at which it is carried away by the gas stream and leaves the reactor as an inevitable and irreversible loss. As a rule, these losses can reach up to 5 10% of the supplied materials. When the diameter of the feed particles is reduced to below 150 microns, the loss of volatilization becomes relatively much higher than for materials of ordinary size. Such losses are economically and operationally acceptable.

The closest in technical essence and the achieved result is a method of agglomeration of a titanium-containing mineral with a content of> 45 Ti weight. including its mixing with a binder containing TiO ₂ , bituminous coking coal and water, drying and heat treatment at a temperature of 900 1000 ^o C for 10 20 min [1] However, this known process was not accepted by the industry. One of the reasons is that the chlorination process is reductive chlorination, so that carbon must be present in the feed material in a specific ratio to the TiO ₂ -containing material, which may not be suitable for developing the strength of the composition. Further, the agglomerate is destroyed by exposure to carbon before complete chlorination occurs, and thus material with a fine particle size is lost in the process through volatilization with a gas stream.

 The aim of the invention is to overcome one or more difficulties in the process of chlorination in a liquid ("boiling") layer of fine-grained titanium-containing materials.

 Accordingly, the invention provides a method for increasing the size of fine particles of a titanium-iron mineral containing more than 45 weight. titanium, moreover, this method consists in mixing fine particles with a binder and water to obtain a dry sinter, drying the sinter and sintering it.

 The agglomerated particles thus obtained are resistant to grinding forces associated with transportation and handling operations. Such agglomerated particles also resist physical and chemical degradation forces and temperatures associated with the chlorination process in the fluidized bed.

 Agglomerated particles can be obtained in the preferred range of particle size (size) in accordance with the dynamic requirements of the reductive chlorination process in the fluidized bed, for example in the range of 100 to 150 microns, more preferably in the range of from 150 to 250 microns. If the particle size is below these limits, they can be carried away with the gas stream and, therefore, lost for the reaction. If the particle size is above this range, they will tend to weigh in a pseudo-liquid layer and form an inactive layer in this part of the reactor.

The titanium-containing particles may be from any suitable titanium-containing mineral or minerals. Titanium-containing minerals may be natural or synthetic in origin. The titanium-containing mineral may be a detrital mineral. Titanium can be present in titanium-containing minerals in the form of titanium dioxide, in titanium-containing minerals it can be approximately 85 weight. and more. A preferred source containing titanium dioxide is a deposit that includes any of the minerals
rutile, anatase and leukoxen.

 Titanium-containing minerals after extraction can be subjected to an initial concentration process. This concentration process can lead to an increase in the average titanium dioxide content, for example, to about 90 weight. or higher.

 However, a titanium-containing mineral deposit in Horsham, Victoria, Australia, of this type, is further characterized, as a rule, by fine particle size. The unusually small size suggests that the main loss of volatilization may occur during later treatments with reductive chlorination in the pseudo-fluid layer.

 The titanium-containing mineral may be present in the agglomerated particles in any suitable amount. Titanium-containing minerals may be present in amounts of approximately 95 to 99.5 weight. from the total weight of the synthesized agglomerate.

 The amount of added water may vary depending on the sieve distribution of the initial titanium-containing particles and the required size of the agglomerates. The amount of water may vary from approximately 5 to 15 weight. preferably 8 weight. of the total weight of titanium particles, a binder and water.

 The binder or substances for the titanium-containing particles may be of any suitable type. The binder for titanium-containing particles must be such as to create agglomerates capable of withstanding the forces of physical, chemical and thermal degradation at the stages of drying and firing of the process. The binder may be ceramic or glass-forming material. The binder may be carbon-free binder. There may be about one binder. A combination of two or more binders can be used to provide strength under various operating environmental conditions of drying and firing.

 Calcium and sodium-containing binders are not preferred, since calcium and sodium can react in the process of reductive chlorination, leading to the formation of destructive liquid precipitates. Binders may contain calcium and sodium, but they should not lead to problems in chlorination.

 The binder for titanium-containing minerals may be such that it will not seriously contaminate the bound titanium-containing particles for subsequent processing, for example, in the process of reductive chlorination.

 Binders for titanium-containing particles may include: 1) colloidal silicon dioxide; 2) silicon dioxide, water-soluble silicates or mixtures of silicon dioxide with fluorite; 3) clay minerals, including bentonite, kaolinite and montmorillonite; 4) boomets; 5) a mixture of boehmite with silicon dioxide; 6) geotite; 7) lignosulfonate; 8) sodium carbonate (saturated aqueous solution); 9) sodium silicate; 10) a mixture of the carbonate of an element of group 11 with a clay mineral; 11) sugars, for example, molasses; 12) a mixture of an aluminum salt with an organic amide; 13) titanium-containing organic and inorganic solutions; 14) polyvinyl acetate; 15) water-based organic binders.

 The amount of binder for the titanium-containing particles must be sufficient to form the corresponding agglomerate. Preferably, the amount of binder is insufficient to encapsulate the titanium-containing particles. The preferred amount of binder in the range of approximately 0.5 to 5 weight.

 The mixing step in the process in accordance with the invention can be carried out in any suitable way. Agglomeration can be carried out in devices including grinding and shredding operations, for example, in rotating disk and drum granulators or V mixers, or in devices including impact and cutting operations, for example, in high-intensity microagglomerators or mixers, or in devices including those and other operations . Agglomeration can be carried out in stages or in a closed circuit with sorting sieves.

The drying step can be carried out at elevated temperatures, for example 75-150 ^° C. This step is preferably carried out so as to limit the residence time of the agglomerates in this part of the process to less than 30 minutes. The drying step may be carried out in any suitable drying apparatus. A fluidized bed dryer or a rotary dryer may be used.

At the stage of firing, the temperatures and residence time should be sufficient to obtain a homogeneous or heterogeneous phase bond between particles within the agglomerates. The agglomerates can be heated to a temperature of approximately 1000 1500 ^o C, preferably 1200 1400 ^o C. the residence Time of the agglomerates in the above temperature range can be from about 5 minutes to about 6 hours.

 The calcining step may be carried out in any of a number of suitable devices, including a pseudo-fluid bed, a kiln or a kiln kiln.

 In a preferred embodiment of the invention, the process may include a preliminary step of grinding at least a portion of the source of titanium-containing particles.

 The preliminary grinding stage can be used to improve the control of fineness in the production of agglomerates and thereby to provide greater strength and density of the calcined product. Titanium particles can be ground in any suitable mill. A ball mill, a rod mill, or an intensive grinding device may be used.

 The size of the titanium-containing feed for grinding can vary from 0 to about 100 weight. depending on the source and type of titanium-containing material.

 The grinding step can provide particles having an average particle size of from about 1 μm to about 50 μm.

 Sintered agglomerate may include many sintered agglomerated particles. The bond formed between the titanium-containing particles may include boundary recrystallization of the particles, that is, the boundaries of the titanium-containing particles can physically merge. The bond formed between the titanium-containing particles may further include jumpers with a secondary phase formed by the binder. The sintering step may tend to decrease or eliminate the binder from the agglomerated particles. The initial binder may burn out in whole or in part. The initial binder may be present and / or incorporated in whole or in part into the crystal lattice of the particles.

 Below the invention will be more fully described with reference to the accompanying examples. It should be borne in mind, however, that the following description is for illustration only and by no means to limit the scope of the invention described above.

 Example 1

 Laboratory model V of the Paterson-Kelly mixer was originally used to transfer 9.2 kg of dry leukoxeva with 1% dry bentonite powder for 1 2 minutes. The leucoxene size was 75% in the range of 50 to 100 μm and 25% in the range of 50 μm. The size distributions of the two fractions are presented in table. 1 and 2.

 V mixer rotates at 40 rpm. Water was then introduced into the mixture through an amplifier rod rotating inside the mixer housing at a speed of 1,500–3,000 rpm. The core of the amplifier was used both for cutting off solids and for injecting water into the charge in finely divided form. The amount of added water was about 8% of the weight of solids and the time required for crushing it was about 4 minutes. The next 1 - 2 minutes were allotted for mixing to achieve microagglomerates of final fineness and compaction.

The product was then shipped to a large tray, scattered over its area and kept in an oven at 80 ^° C for 48 hours to ensure complete drying.

The dried product was passed through a sieve to a particle size range of 125,500 microns. 100 g of microagglomerators were placed on a ceramic plate and aged for 25 minutes at a temperature of 1260 ^o C. The synthesized product was then subjected to a series of physical and chemical tests considered appropriate to determine its suitability as a starting material for the reductive chlorination process.

 Visual inspection of microagglomerators after synthesis revealed two obvious changes compared to dried, but not synthesized material. Firstly, some shrinkage occurred either due to a decrease in the internal voids of microagglomerates, or due to a decrease in the space between the granules of the agglomerate mass after sintering. Secondly, the color of the material has changed from dun to reddish brown. Further, the material took a glassy or reflective appearance compared to the dull surface of the unfired material.

 Microscopic examination of the synthesized product showed a high density of particles within the agglomerates with many bridges between the particles. Analysis using an electronic microprobe did not reveal any compositional discrepancies between the material of the jumpers and particles. No significant degradation or adhesion of the agglomerate-agglomerate as a result of firing was noted. X-ray diffraction analysis of the calcined microagglomerates showed the main rutile and pseudobrunite phases, that is, crystalline phases that could have formed from the original leukoxen itself.

 The size of the product after firing is illustrated in table. 3.

 The test for "strength" on microagglomerates was carried out as follows. A microagglomerate was placed between two glass slides and weights were placed on them until the first destruction of the agglomerate. This occurred at a load of more than 1 kg (i.e., approximately 10 N) for 300 μm agglomerates. The pieces of agglomerates had similar dimensions, i.e. there was a slight or no tendency to turn into dust. Calculations show that with such a fixed strength, it would be possible to store agglomerates without destruction due to compression forces in heaps or in bins with a height of approximately 50 m.

A better and reproducible abrasion resistance test was carried out by vigorously shaking one gram of a close-in-size microagglomerate fraction (-335 ^o C250 μm) for 5 minutes in a cylindrical tube with an inner diameter of 18 mm and a length of 50 mm with 3 ceramic balls with a diameter of 8 mm . During this test, the material was subjected to both impact and abrasion. The average particle diameter after this test decreased from 303 microns to 170 microns. This is comparable with the characteristics of a similar sample of the original leukoxene material, which decreased in diameter to 220 microns.

 From this we can conclude that from the point of view of storage and transportation, microagglomerates are industrially acceptable material.

Small samples (10 g) of microagglomerates were tested for chlorination in a pseudo-liquid layer in a laboratory reactor at a temperature in the range of 950 1100 ^o C. The results showed that with more than 50% chlorination:
(1) there was no evidence of an effect on intergranular bonds; on the contrary, the bonds seemed relatively more inert than the bulk of the individual granules of the mineral;
(2) when the titanium dioxide of the microagglomerates was partially removed, the unreacted core of the material with the original appearance (except for bleaching) remained within the microagglomerates; the pores of the affected outer sheath have noticeably increased in size.

In the table. Figure 4 shows the initial and final particle size distributions of the calcined agglomerates, which were brought to 89% chlorination in laboratory tests in the fluidized bed. There is a clearly insignificant formation of 90 μm material during chlorination, which suggests that chlorination can be achieved without breaking bonds or losses in the reactors in the form of small particles carried away with the gases. Similar results were obtained when bringing chlorination to 95%
The fluidization characteristics of microagglomerates were measured depending on the size and compared with the behavior of theoretical balls of petroleum coke and leucoxene based on sea sand. The results, presented as a practical minimum liquefaction rate in air at room temperature depending on the average particle diameter, are illustrated in FIG. 1. These results show higher than expected minimum rates of liquefaction at smaller particle diameters and lower than expected minimum rates of liquefaction at larger particle diameters. This behavior can be partially explained by the influence of the size distribution and partially by the influence of the density and shape and roughness of the surface. It is assumed that the chlorination process can be designed for larger particles of agglomerate than in the case of conventional downloads, thereby providing the possibility of improving the process.

 Example 2

 About 10 kg of crushed leukoxene was agglomerated and dried in the same manner as described in example 1.

Microagglomerates were loaded into a small furnace with a pseudo-liquid layer, in which the temperature of the layer was maintained at 1260 ^o C. The operational parameters of the furnace were as follows:
layer diameter 30 cm
air chamber temperature 1000 ^o C
fuel air chamber 1 RS (liquefied petroleum gas)
fuel for a layer of coke coal coal
surface velocity of a gas in a fluidized bed 71 cm / sec
agglomerate feed rate 22 kg / h
To control the temperature and surface velocity of the gas within the layer in a given range, it was found necessary to enrich the intake air with oxygen on this small-sized equipment.

 The average residence time of the material within the layer was 20 minutes.

 The amount of material of the layer carried away by the exhaust gas was estimated at 4.5%. Distributions by particle size of the charge, product and carried away material are illustrated in FIG. 2.

 The final product was subjected to the abrasion test described in Example 1. The result showed a decrease in average particle size from 303 μm to 190 μm.

 Example 3

 Agglomeration tests were carried out on the material with the following size distribution.

 Agglomeration was carried out in the Flexomiko industrial agglomerator, manufactured by the company Sugi Process Engineers, Lelystad, the Netherlands, at a solids feed rate of 840 kg / h. Bentonite was pre-mixed with the charge at a 1% addition and lignosulfonate was added as a 33% solution at 2.8 kg of solid / h. The water supply in addition to the addition of lignosulfonate was 1 l / min.

 After continuous passing through an agglomerator and a dryer with a liquid layer, 67.5% of the product had a fineness in the range of +125 500 μm. Product with a diameter of more than 125 μm was collected for subsequent firing in an oven.

The agglomerates were fired in a countercurrent rotary kiln operating on liquid fuel and having a length of 3.6 m and an inner diameter of 0.23 m. At a rotation speed of 2 rpm and a slope of 1 degree, the agglomerate was in the high temperature (1260 ^o C) zone was approximately 20 minutes In total, 60 kg of agglomerates were fired in an oven at a feed rate of 16.2 kg / h.

 The fine-grained material in the charge and the material degraded during firing were carried away by combustion gases, the final product was 69% of the charge in the furnace. The particle size distribution of the load and the final product are presented in table. 6.

 Continuous agglomeration experiments were conducted in an industrial mixer manufactured by Patterson Kelly Propeti Ltd., Pennsylvania, USA. The loading of ground leukoxene had the following particle size distribution.

 The mixer was charged with ground leukoxene at a rate of 0.6 t / h in addition to bentonite at a speed of 6 kg / h and an organic binder (polyvinyl acetate) at 1.5 kg / h. Water was added in a volume of 10% of the load weight through nozzles mounted on the shaft of a set of high-speed rotating blades within the sintering chamber. The residence time of the mineral in the sinter was 20 minutes

The agglomerated product was dried in a tube dryer to a maximum temperature of 80 ^o C.

 The particle size distribution of the dried product is presented in table. eight.

The dried agglomerated product was fed at a rate of 73 kg / h to a firing unit with a pseudo-fluidized bed at a temperature of 1250 ^° C. The unit had a diameter of 0.46 m and a height (above the distribution plate) of 0.56 m. The air-rich propane combustion product was a diluting gas. The distillate was sprayed into the base of the liquefied bed to provide additional heat by burning with oxygen remaining in the liquefying gases. The average residence time of the agglomerates in the fluidized bed was approximately 60 minutes.

 The fine-grained material present in the charge and generated during firing in the fluidized bed was captured by combustion gases and removed through a hot cyclone. Only 17% of the load was carried away in this stream.

 The particle size distribution of the calcined agglomerates in the fluidized bed and entrainment are presented in table. 9.

Claims (16)

1. The method of agglomeration of a fine-grained titanium-containing mineral, comprising mixing a mineral with a content of more than 45% titanium with a binder and water to obtain agglomerate, drying it and heat treatment of dry agglomerate, characterized in that the heat treatment is carried out by heating to a temperature in the range of 1000 1500 ^o C for a period of time sufficient to sinter the agglomerate.  2. The method according to claim 1, characterized in that as a binder use a substance capable of forming glass or ceramics during sintering.  3. The method according to p. 1, characterized in that the binder is selected from any compounds of the group including colloidal silicon dioxide, or silicon dioxide, water-soluble silicates, or mixtures of silicon dioxide with fluorite, or clay minerals, such as bentonite, kaolinite and montmorillonite, or boehmite, or a mixture of boehmite with silicon dioxide, or geotite, or lignosulfonate, or a saturated aqueous solution of sodium carbonate, or sodium silicate, or a mixture of the carbonate of an element of group II with a clay mineral, or sugar, such as molasses, or a mixture of salt with an organic aluminum amide or titanium-containing organic and inorganic solutions, or polyvinyl acetate, or a water-based organic binders.  4. The method according to any one of paragraphs. 1 to 3, characterized in that the agglomerate is formed by mixing a fine-grained mineral, a binder and water through shock shear.  5. The method according to any one of paragraphs. 1 to 4, characterized in that the binder is 0.5 to 5 wt. of the total weight of the fine-grained mineral and binder to dry weight.  6. The method according to any one of paragraphs. 1 5, characterized in that the amount of water is 5 to 15 wt. of the total weight of the fine-grained mineral, binder and water. 7. The method according to any one of paragraphs. 1 to 6, characterized in that the drying of the agglomerate is carried out for less than 30 minutes at a temperature of 75 to 150 ^o C. 8. The method according to any one of claims 1 to 7, characterized in that the agglomerate is sintered at a temperature in the range of 1200-1400 ^o C for 5 minutes to 6 hours  9. The method according to any one of paragraphs. 1 to 8, characterized in that the titanium-containing mineral is a mixture of fine-grained and coarse-grained minerals.  10. The method according to p. 9, characterized in that the titanium-containing mineral is pre-crushed.  11. The method according to p. 10, characterized in that the mineral is ground to particles having an average size in the range of 1 to 50 microns.  12. The method according to any one of paragraphs. 1 to 11, characterized in that the sintered agglomerate has an average particle size in the range of 100 to 500 microns.  13. The method according to any one of paragraphs. 1 to 12, characterized in that the agglomerates have an average particle size in the range of 150 to 250 microns.  14. The method according to any one of paragraphs. 1 13, characterized in that the mineral is a detrital mineral.  15. The method according to any one of paragraphs. 1 to 14, characterized in that the mineral contains more than 85 wt. titanium dioxide.  16. The method according to any one of paragraphs. 1 to 15, characterized in that the mineral is rutile, anatase or leukoxene.

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