DE2037990A1 - Process for the production of titanium dioxide - Google Patents

Description

"Process for the production of titanium dioxide"

Priority: "July 31, 1969, Italy, No. 20 367-A / 69

Titanium dioxide is used in particular as a pigment. For the When used as a pigment, a product with special properties such as hiding power, spreadability or high gloss is required.

There are several methods of making titanium dioxide known. In addition to the sulfuric acid process, the chlorine process has recently become very important. Here the titanium-containing Raw material, such as "rutile or titanium dioxide concentrate, in Titanium tetrachloride transferred and this is after separation the accompanying elements are hydrolyzed or oxidized in the gas phase; see Ullmann, Encyclopedia of Technical Chemistry, 3rd edition, 13 Vol., 1962, pp. 767-769; Kirk-Othmer, Encyclopedia

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of Chemical Technology, Vol. H, 1955, pp. 223-225; HSl patent 2,635,946 and British patent specification 707,389.

In the known process for the production of titanium dioxide., By oxidation of titanium tetrachloride, TiO _{2 is} formed at temperatures above its softening point, ie at temperatures at which it is plasticized so that it easily adheres to surfaces with which it comes into contact . For this reason, in the case of the known methods, deposits can form on the burner and on the boundary walls of the. Seaktixmskammer form, especially at those points where the reaction components come into contact with one another. Deposits formed on the burner are extremely damaging because they disrupt the formation of the flame by making it unstable and irregular. As a result, the end product does not have constant properties. A similar effect occurs when deposits form in the vicinity of the gap through which the reaction components are fed. '-

The object of the invention was to provide an improved method for Manufacture of titanium dioxide by oxidation of titanium dioxide chloride by means of oxygen or free oxygen-containing bases for To provide, in which a fine, regularly shaped, round particles with a bounded within a Grain diameter lying in the range, consisting of agglomerates free product with rutile structure is obtained and in which the formation of deposits in the device concerned

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is avoided, so that a titanium dioxide with constant Properties can be obtained. Another object of the invention was to provide a simply constructed and easy to use Device for carrying out the aforementioned method

to provide. This object is achieved by the invention solved.

The invention thus relates to a process for the production of titanium dioxide by separately introducing preheated titanium tetrachloride and oxygen or free oxygen-containing gases into a reaction zone and reacting in the gas phase in the presence of an auxiliary flame produced by the combustion of a fuel, which is characterized by this ,, That the reaction is carried out in a device which consists of a reaction chamber which is divided into an upper cylindrical zone and a lower cylindrical zone with a larger diameter than the upper cylindrical zone, and the two zones with one another via a frustoconical zone are connected, in which the reaction components mix *

• that in the upper zone of said auxiliary flame% produced in such a manner that the fuel within that zone is completely combusted in that the oxygen or the oxygen-free

• containing gas at room temperature or slightly above haum temperature in tangential direction to the wall of the upper cylindrical zone ^{feeds that the titanium tetrachloride preheated to temperatures of at most 500 0} C in the form of a 0.1 to 0.8 cm wide annular stream with a linear inlet speed feeds from 10 to 70 m per second through a gap in the wall of the frustoconical zone, whereby the titanium tetrachloride gas flow to the flow of the combustion

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-A-

tion formed hot gases jinen angle of 30 to 60 ° includes, and that the reaction is carried out at temperatures of 1200. to HOO ⁰ C and separates the titanium dioxide from the cooled reaction products.

The titanium dioxide is formed in the process of the invention due to the special geometric construction of the reaction chamber so far from the burner that this one before the one. Deposition of solid substances is protected. The formation of Deposits are avoided in the process of the invention at the gap for the supply of titanium tetrachloride, since the reaction components, as mentioned, in this zone are significantly below the Rß action temperature come into contact with each other, apart on the protective effect of the feed stream introduced at high speed. Because the implementation within a zone takes place, which is limited to the central part of the reaction chamber, eventually the formation of deposits on the Boundary walls of the oxidation zone avoided.

The products discharged from the reaction chamber are cooled, and then the titanium dioxide is made using the conventional methods for the separation of solids from gases, e.g. with dust separators or electrostatic filters » The separated gases, which contain the CIp produced in the reaction chamber and the combustion gases, are used for the

in the
Part / system for the cooling of the products discharged from the reaction chamber and partly for the chlorination of titanium ore for the production of titanium tetrachloride

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2G37990

used. "

In the process of the invention, a molar ratio is preferred

from oxygen to titanium tetrachloride from 1.15 * 1 to 1.4: 1. The gas oxidizing is fed for example at temperatures of 15 to 40 C, "" - while "is the preheated .Titantetrachlorid expedient to temperatures of at most 50O ^{0 C.}

In the process of the invention, in addition to oxygen, gases which contain more than 90 ° β> free oxygen can be used as oxidizing gases.

3 examples of suitable fuels for the auxiliary flame are: Carbon monoxide, hydrogen, methane, acetylene or liquefied petroleum gas (a low-boiling aliphatic hydrocarbon). Carbon monoxide is preferred because it does not lead to undesired formation of hydrogen chloride. -. '■'.

: One must in the process of the invention the combustion of the fuel regulate so that the reactants in the zone for the mixture can be heated rapidly to the oxidation temperature of the titanium tetrachloride.

Venn used carbon monoxide as fuel and the titanium tetra; Chloride is preheated to temperatures of 300 to 400 ⁰ C, at least 0.3 mol of carbon monoxide are used per mole of titanium tetrachloride.

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An important feature of the method of the invention is that one feeds the titanium tetrachloride as an annular, laminar gas stream, which with the by the combustion of Fuel generated hot gas stream an angle of 30 to 60 ° includes. The term "laminar gas flow" ^ relates here on streams with a width of 0.1 to 0.8 cm.

• The production of titanium dioxide having the properties described above has not only ^r the ^ -Plamme regulated and in accordance with conventional procedures, a suitable nucleating compound * as aluminum chloride, silicon tetrachloride, or water vapor, may be added, but it must be also provided for such a flow system that same for all particles TERMS oF terms of their formation, growth, the high-temperature resistance and the cooling are ensured.

The foregoing objects are of using the method: reaches the invention in which a rapid mixing of the ■ "titanium tetrachloride with the oxidizing gas and anschlies-

• Send an equally rough homogenization of the reaction participants. with the hot gases created by the combustion of the fuel. The latter fact in particular ensures that the reaction takes place completely in a short section of the zone for the oxidation. In any case

• The reaction takes place in a room in which the total product return flow is sufficiently low. The course of this return flow 8 mainly affects that part of the zone for the oxidation that is two to three times as much from the mixing area

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The diameter of the reaction chamber has a corresponding distance,

If the reaction is carried out for a very short time in the reaction chamber according to the method of the invention, it is avoided that the unreacted titanium tetrachloride comes into contact with the recycled material. This prevents the oxidation reaction from taking place on the surface of the titanium tetrachloride particles already formed. In this manner is neither formation of titanium dioxide particles having 'undesired λ th dimensions nor agglomeration statt..Gemäß the method of the invention, the drawn-off from the reaction chamber products are rapidly cooled to a temperature of 30O ⁰ C.

The gases formed during the reaction can be used for cooling , whereby these gases are freed from dust, cooled and then recycled.

The titanium dioxide is ultimately used by the other implementation pro-

• i ducts separated and quality checks with regard to its ■ subject to reversibility in pigments. Then you treat it to produce the final pigment products in a conventional manner.

The invention also relates to a device for carrying out the aforementioned method (see. Fig.1 and Fig.2), which is characterized in that it consists of a reaction chamber which is divided into an upper cylindrical zone 1 and a lower cylindrical zone 3 with a larger Diameter than the upper cylindrical zone 1 is divided, the two zones across

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a frustoconical tooth 2 are connected to one another, and the one in zone 1 containing a burner 4 and two supply lines 5 for the oxygen or the free oxygen Gas and in zone 2 an annular gap 7 for the introduction of the titanium tetrachloride fed in through lines 6.

Pre-mix type burners are preferably used because relatively short flames can be achieved with them.

The titanium tetrachloride fed in through lines 6 is into the frustoconical zone 2 through the in the

Wall of this zone and essentially one with this wall Right angle enclosing the annular gap transferred. The angle of inclination of the wall of zone 2 in relation to on the longitudinal axis of the reaction chamber is determined so that the desired angle of impact between the Ti'tante * trachlo-rid gas flow and the flow of hot reaction gases is guaranteed.

Another important feature of the invention is that that provided for the oxidation of titanium tetrachloride Gas, such as oxygen, is fed in tangentially to the boundary wall of the upper part of zone 1. The cold, oxygen containing gas is fed in according to FIG. 1 through two supply lines 5. These lines are shown in Fig. 2, the represents a section through the reaction chamber at the level of the supply lines for the oxidizing gas, show in more detail

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posed. The 'oxidizing gas flows in near the wall zone 2, where it is mixed with the titanium tetrachloride. This will damage the wall of the Zone 1 avoided by the flame originating from the fuel and the oxidizing gas is at temperatures that are significantly below the temperatures prevailing during the oxidation, by the titanium tetrachloride gas flow introduced through the gap 7 into zone 2 with the one in the middle of the Reaction chamber brought into contact with the gas stream pulling downwards. This construction also protects the gap 7 for the titanium tetrachloride from the formation of deposits.

The linear inlet velocity of the titanium tetrachloride gas stream into the reaction chamber must be at least 10 m / second. If the implementation is to proceed satisfactorily, it is inexpedient to if it exceeds 70 m / second. To this In the beginning, the oxidizing gas can be rapidly mixed with the titanium tetrachloride at lower temperatures than can be achieved in the formation of the titanium dioxide, after which a second rapid mixing of the reaction components with the hot gases generated by the combustion of the fuel takes place so that the temperature required for the oxidation is established. ■

The examples illustrate the invention.

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Example 1 '

A reaction chamber of the type illustrated in the drawings is used. According to Pig. 1, the zone for the combustion has a diameter of 15 cm 'and a length of 25 cm, while the zone for the oxidation has a diameter of 35 cm and a length of 120 cm. The two zones are connected to one another via a frustoconical zone inclined at 45 °. The reaction chamber is made of a heat-resistant material that contains -70 to 72 ° aluminum oxide. The annular gap for the titanium tetrachloride has a width of 0.1 cm and is delimited by two walls made of nickel and fitted and dimensioned in such a way that there is a constant opening along the entire circumference.

The burner runs on carbon monoxide containing $ 2 hydrogen . and charged with oxygen. The added proportions are gradually up to maximum values of 22.6 lim CO / hour * and from 17 Nm- Op / h elevated. A premix type burner is used, which develops a flame which is essentially consumed within the zone for combustion, so that the the gas supplied to the mixing zone is completely burned.

At the same time, oxygen is being released at a rate of 47 njir / hour. by two at the top of the zone for incineration attached supply lines fed in "The supply of the Oxygen is in Pig «, 2 near? illustrates

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A nitrogen stream is now fed in through the annular gap in the wall of the frustoconical zone. If, which is the case after about 2 hours, constant Conditions prevail, the nitrogen is gradually replaced by titanium tetrachloride.

The titanium tetrachloride containing 2 wt .- ^ aluminum chloride is preheated in heat exchangers made of a Ni / Cr alloy to 400 ⁰ C and at a rate of 320 kg / hour. fed in. The heat exchangers are not included in the drawings. The titanium tetrachloride is supplied through an annular gap 0.1 cm wide, enclosing a right angle with the wall of the frustoconical zone, from which the gas flow exits at a linear velocity of 33 m / sec. The titanium tetrachloride gas flow is transferred into the mixing zone at an angle of 45 ° to the axis of the hot gas flow generated by the combustion of the carbon monoxide.

0.6 mol of carbon monoxide is used per mol of titanium tetrachloride.

The reaction products are cooled ^{to about 30O 0} C in the discharge lines leading away from the reaction chamber by recycling the reaction gases after they have been cooled and freed from dust.

One receives 134 kg of titanium dioxide per hour, the following egg

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has genco-like:
Average grain size: 0.23 µ;

Grain size distribution: 80 $> of the particles "have a grain size of 0.17 to 0.30 μ, with no agglomerates whatsoever having formed;

Crystal structure: over 99 "/> rutile; Reynolds number: 1950.

After completion of the attempt (after 10 hours) are in the Device no deposits found.

The product is ideal for pigments.

Example 2

The procedure of Example 1 is repeated using the same apparatus but the burner becomes a lower one Fuel proportion supplied. There will be 0.4 moles of carbon monoxide per Mol titanium tetrachloride used.

The titanium dioxide obtained in this way has the same properties as the TiO ₂ produced according to Example 1.

Example 3

The procedure of Example 1 is repeated using the same apparatus but the burner becomes a lower one Fuel proportion supplied. There will be 0.3 moles of carbon monoxide per

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Mol i'itantetrachlorid used.

The titanium dioxide obtained in this way has a Reynolds Number of 1800, the particles have a grain size of $ 80 from 0.15 to 0.30 u. Some agglomerates are noted.

Example 4

The procedure of Example 1 is followed using the same Device repeats, but less carbon monoxide is added. 0.2 mol of carbon monoxide is used per mol of titanium tetrachloride.

The titanium dioxide obtained in this way has a Reynolds Number of 1300. The particles are about 80 $ the size of a grain from 0.10 to 0.32 u. There are also numerous agglomerates and some particles are irregular in shape.

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Claims (9)

Claims 1 · Process for the production of titanium dioxide by separated Introducing preheated titanium tetrachloride and oxygen or gases containing free oxygen into a reaction zone and reacting in the gas phase in the presence of a - combustion of a fuel created auxiliary flame, thereby characterized in that the reaction is carried out in a device which consists of a reaction chamber which is in an upper .cylindrical zone and a lower cylindrical zone with a larger Diameter divided as the upper cylindrical zone ..is.t and the two zones having a frustoconical Zone are in communication with each other, in which the reaction components mix so that in the upper zone the auxiliary "Flame is generated in such a way that the fuel is completely burned within this zone, that the oxygen or the free oxygen-containing gas is fed in at room temperature or slightly above room temperature in a tangential direction to the wall of the upper cylindrical zone," that the at temperatures not exceeding 500 ⁰ C preheated titanium tetrachloride in the form of a 0.1 to 0.8 cm wide annular stream with a linear inlet speed of 10 to 70 m per second through a located in the wall of the frusto-conical zone gap feeds, wherein the titanium tetrachloride gas stream forms an angle of 30 to 60 ° with the stream of the hot gases formed by the combustion, and that the. • Carries out the reaction at temperatures from 1200 to 140O ⁰ C and. . separating the titanium dioxide from the cooled reaction products. 109 812/1478 ,. _ ₁₅ -;. ■■. 2. The method according to claim 1, characterized in that the oxidizing gas used is oxygen or a gas containing at least 90 tfo of free oxygen. 3. The method according to claim 1 or 2, characterized. That one uses 1.15 to 1.4 mol of oxygen per mole of titanium tetrachloride. 4. The method of claim 1 to 3, characterized in that one uses an oxidizing effect gas having temperatures from room temperature to 40 ⁰ C. 5.. Method according to Claims 1 to 4, characterized in that that the fuel is hydrogen, methane, acetylene, a liquid gas or preferably carbon monoxide is used. 6. The method according to claim 5, characterized in that there is at least 0.3 mol of carbon monoxide per mole of titanium tetrachloride used. Il 7. The method according to claim 1 to 6, characterized in that one uses a burner of the premix type. 8. The method according to claim 1 to 7, characterized in that that, for cooling, the gases formed during the reaction are freed from dust, cooled and recycled. 9. Apparatus for performing the method according to claim 1098 12 / U7 8 to 8, characterized in that it consists of a reaction chamber consists in an upper cylindrical zone (1). and a lower cylindrical zone (3) of larger diameter than the upper one cylindrical zone (1) is subdivided, the "two zones" being connected to one another via a truncated cone-shaped zone (2) stand, and in zone (1) a burner (4) and two supply lines (5) for the oxygen or the free oxygen . Containing gas and an annular gap in zone (2) (7) for the introduction of the titanium tetrachloride fed in through the lines (6). 10981 2 / U78