DE1241808B - Process and device for the production of finely divided metal oxides - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

BOIj

German class: 12 g -5/01

Number: 1241 808

File number: F 40243IV a / 12 g

Filing date: July 16, 1963

Open date: June 8, 1967

The invention relates to the production of finely divided Metal oxides by burning a mixture of metal chloride and oxygen under Use of an auxiliary gas flame, the flows of the reaction gas mixture and the auxiliary S cross fuel gas-oxygen mixture.

The inventive measures can not only for the oxidation of titanium tetrachloride, but also for the oxidation of other vaporizable metal chlorides to the oxides of the corresponding metals to be used. Among other things, z. Belly the chlorides of zirconium, aluminum, tin, chromium, iron and silicon (which in the context of this Invention is counted among the metals) can be used as a starting material.

It is known that metal chlorides in the vapor phase can be used at high temperatures, e.g. B. at over 1000 ° C, burned in oxygen to form a suspension of metal oxide particles in a chlorine-containing To get gas. The finely divided oxide particles produced in this way are, for. B. useful as pigments.

Many modifications of this general type of procedure are known. The chloride vapor can e.g. B. mixed with an inert diluent gas or with various substances prior to combustion which should improve the quality of the oxide to be produced. There are several for this Burner assemblies have been used to provide adequate mixing of metal chloride vapor and oxygen and the length of time the oxide remains in the burn zone accurately to regulate.

Three main groups of the process should be mentioned here: Process with an auxiliary flame, d. H. a flame from an auxiliary fuel gas, usually carbon monoxide, into which the metal chloride and the oxygen are introduced to initiate combustion, processes where none Auxiliary flame is used, and processes in which the combustion of the metal chloride in a fluidized bed of the oxide produced by the combustion takes place. All of these types of procedure exhibit certain disadvantages.

A device is also known in which a mixture of metal chloride vapor and oxygen-containing gas flows out centrally and in a straight line into the tubular reaction space, while the auxiliary fuel gas, eg CO-HO ₂ , is introduced into the flow of the reaction mixture in several jets from the outside being, the direction of each beam being the axis of the direction of movement of the reaction process and apparatus for manufacture
of finely divided metal oxides

Applicant:

Fabriques de Produits Chimiques de Thann

et de Mulhouse,

Thann, Haut-Rhin (France)

Representative:

Dipl.-Chem. Dr. H. Wittek, patent attorney,

Heidelberg-Schlierbach, Im Grund 20

Named as inventor:
Dipl.-Ing. Robert Leon Jean Mas, Thann;
Dipl.-Ing. Andr £ Louis Michaud, Vieux Thann,
Haut-Rhin (France)

Claimed priority:

Great Britain of July 17, 1962 (27 499),

dated February 8, 1963 (5317) -

miseries crosses. The mixture of TiCl ₄ and O _{2 is} heated only gradually and very unevenly due to the thickness of the jet.

In the method according to the invention, metal chloride and oxygen are introduced into the central CO + O ₂ flame in several jets. As a result, the penetration of reaction gas and auxiliary flame is much more intense.

As a result, a better product is also obtained, as can be seen from a comparison of curve D in FIG. 5 and 6 corresponding to the Swiss patent 265192 can be seen with a curve according to the method according to the invention.

For example, in processes without the use of an auxiliary flame, it is necessary to preheat the gaseous reactants, which is large and expensive equipment makes necessary outside the reactor.

Processes using a fluidized bed have the same drawbacks, and it is required to keep the fluidized bed at a high constant temperature.

In processes with an auxiliary flame, the problem of heating reactants is eliminated, but

709 589/330

3 4

the difficulty here still lies in the flare-up from the walls of the reaction chamber being sustained kept at a homogeneous and stable distance, thus avoiding pollution of the flame. In the known processes this is formed metal oxide and the corrosion of the walls Difficulty hitherto not completely overcome is prevented. It also gets the mix off been. 5 metal chloride and oxygen faster with the fire

In such processes (cf. German patent gases of the auxiliary flame mixed than in the earlier Documents 948 415 and 1036 221) are titanium tetra-usual processes; the chloride flame thus becomes Chloride, oxygen, and carbon monoxide are much better regulated by an an, and one obtains an equal number of inlet opening inferior product arranged in a circle. It was also found that genes in a parallel direction into the interior of the carbon io not in the method according to the invention Monoxide auxiliary flame introduced, which the reaction is necessary, activating substances and nuclear formers, such as SiIitionsmittel heated to combustion temperature. The zium and aluminum chloride, which im Carbon monoxide flame is used by a relatively large general in the known processes Number of individual flames formed around the. In the method according to the invention were inlet openings burn around, by which the 15 the nitrogenous in the auxiliary flame, the reac-reactants to be introduced. This arrangement formation favorably influencing products (because results in a complex flame structure, which the gases supplied to the flame usually do difficult to regulate precisely, and this deficiency contain nitrogen), which leads to stability and homogeneity to uneven metal oxide products. did the bleach flame better. So it exists

In another method, a stream 20 does not need any other activating agents or

add hot fire gases from an auxiliary flame to a nucleating agent. The maximum number of cores,

cylindrical combustion chamber in one direction which e.g. B. nitrogen formed in the auxiliary flame

Introduced tangentially to the walls of this chamber, containing oxyde and ozone, is then generated when

and in this spiraling stream the initial temperature difference between the

hot fire gases will then be a mixture of 35 reactants and the fire gases is greatest.

Metal chloride and oxygen are injected, as in the known processes, the auxiliary

in the finer direction parallel to the axis of the combustion flame, preferably a carbon monoxide flame. In

πϊέ'τ. In this process, the warmest part it can reach a temperature of

FeMÜming of the metal chloride generated ram (here reach 2400 ⁰ C, but the one emitted by it

hereinafter referred to as "chloride flame") of 30 fire gases are slightly cooler and have e.g. one

the auxiliary flame disconnected and the regulation of the temperature of about 1900 ° C. The injection

This causes chloride combustion to a certain extent from the mixture of metal chloride and oxygen

measure relieved, but the mixture of metal on another Tempcraturabfall eg 1400 ⁰ C

chloride and oxygen with the hot fire gases. The last-mentioned temperature can still

is not done quickly enough to be further reduced by removing the walls of the

sufficient regulation of the chloride flame to allow cooling zone in which the chloride flame burns, which often

borrowed, and besides, the walls of the burning is beneficial.

chamber of the spirally moving gases The maximum temperature of the auxiliary flame can be corroded, can be reduced by adding more oxygen

The inventive method consists in 40 as to convert all of the carbon monoxide into that the auxiliary fuel gas is required in a pre-combustion chamber before carbon dioxide. It is similar when Entrance into the reaction chamber ignites, which releases oxygen in the form of air (what flamed auxiliary fuel gas through a single central usually the case) is supplied as the stick opening introduced into the reaction chamber and the substance part of the combustion heat of the coal reaction mixture absorbed in several rays from outside 45 monoxyds.

forth in the burning stream of the auxiliary fuel gases at high temperatures and in the presence of (Fire gases) is introduced, whereby the direction nitrogen and water vapor burns carbon mon each Jet the flow axis of the burning oxide to a mixture containing carbon dioxide, water, Crosses the flow of the auxiliary fuel gases. The reaction - hydrogen, carbon monoxide, oxygen, nitrogen gases are advantageously at an angle of 45 to 50 oxide and contains H, O and OH radicals. If the 90 ° to the direction of movement of the combustion gases mixture cools, ozone and nitrogen dioxide can introduced. be generated.

In the new, as in the aforementioned, the invention is most advantageous in the will drive the temperature of the mixture of reac- production of titanium dioxide in one for use agents (Chloride and Oxygen) very quickly from 55 formation suitable as a pigment form by the association Relatively low temperature over the dew-burning of titanium tetrachloride explained. That’s the point of the halides produced at a much higher level, titanium dioxide has a very uniform grain size the minimum value of the reaction temperature, with the average maximum value low temperature increases. So the initial can be below 0.5 μ. The grain size can vary somewhat temperature of the mixture of chloride vapor and 60 will be, by changing the process conditions Oxygen with or without an inert gas varies between 120.

and 150 ° C, while the fire gases in which the invention further relates to a device for

the mixture is injected, a temperature of carrying out the method according to the invention.

1900 ⁰ C; the following sudden this comprises a cylindrical reaction chamber D,

Heating the reactants promotes homogeneity, which is in open connection with the pre-combustion chamber C

the nature and consistency of the properties of the preservation and forms a common axis with it,

a metal oxide. In the method according to the invention, a plurality of channels m 4, mS with ge

However, the fire gases and the chloride rings with a diameter for supplying the reaction gas

mixture leads into the reaction chamber D , the axes of which intersect the axis of the reaction chamber D , and a cooling water jacket around the reaction and pre-combustion chamber.

The volume of the pre-combustion chamber is large enough to completely burn off the carbon monoxide or another fuel, but not so great that a noticeable Cooling of the fire gases takes place before they exit the pre-combustion chamber. The length of stay The gases in this chamber can range from a few tenths of a second to just one or two Hundredths of a second.

The pre-combustion chamber and the reaction chamber are expediently combined like a venturi tube educated.

Furthermore, a furnace can be equipped with several burner devices of the type mentioned above.

The invention is explained in more detail below with reference to schematic drawings.

F i g. Fig. 1 shows in section a front view of a burner device with a cooled reaction chamber, the tubes for injecting the chloride in the includes right angles to the axis of the fire gas; the dimensions entered are given in millimeters;

Fig. 2 shows in section a front view of a burner device, the reaction chamber in the Size is reduced and in which the injection pipes are at an acute angle of approximately 45 ° to the flow of fire gas lie;

F i g. 3 is a horizontal section along the line AA of the burner device according to FIG. 2 and shows the symmetrically arranged injection pipes for the chloride;

F i g. 4 shows in section a front view of a burner device with a pre-combustion chamber and a reaction chamber forming a venturi;

5 and 6 show the statistical distribution of TiO ₂ particles obtained by the process according to the invention in comparison with particles produced by known processes.

In Fig. 1 denotes A a burner head with concentric tubes, B the cooling jacket of the part cooled by the circulation of cold water, the water entering through inlet nl and exiting through outlet η 2; C identifies the pre-combustion chamber in which the carbon monoxide or another auxiliary gas is burned, and D is the reaction chamber.

The oxygen is introduced into the burner head A through the inlet g1 and enters the pre-combustion chamber C through the inlet opening g 2 , wherein it previously flows past the guide elements h 1 and h 2. Carbon monoxide or another auxiliary fuel gas is introduced through the inlet kl and burns in the chamber C after it has flowed past the guide elements k 2 and Λ 3, which are provided to increase the turbulence of the gas.

Nitrogen can be introduced through the inlet Zl and be mixed with the auxiliary fuel gas while the auxiliary flame and combustion through the window / 2 can be observed.

The mixture of, for example, titanium tetrachloride with an excess of oxygen enters the burner head A through the inlet ml. The mixture enters the reaction chamber through the inlet m2, m3 and the opening m4, m5 and through further openings symmetrically arranged on the circumference, as shown in FIG. 3. The openings can have different shapes and z. B. be square.

This burner device can be operated as follows: The auxiliary flame, usually one S carbon monoxide flame is put into operation and the gas flow is regulated in a suitable manner. The ver> Burning carbon monoxide results in a very hot flame that has a temperature of more than 2000 ° C (e.g. up to 2400 ° C) and the

generated fire gases are also very hot. These gases hit the chloride jets at the entrance of the reaction chamber D.

A reaction temperature of around 1350 ° C is suitable for the production of rutile.

Figures 2, 3 and 4 also show burner devices according to the invention. These burners are preferably constructed of metal and can e.g. B. off Aluminum is made, which is protected against corrosion and excessively high temperatures with a cooling jacket

»Ο is through which water or another suitable coolant flows, e.g. B. an oil with low vapor tension. The oxygen stream, which entrains the chloride vapor, flows through this jacket in a metal tube, causing excessive cooling of the vapors

as is avoided. The combustion of the auxiliary flame is practically perfect when the fire gas reaches the point at which the chloride vapor is introduced will. To avoid heat loss, the interior of the pre-combustion chamber is preferably equipped with a Lined with ceramic material.

A preferred burner arrangement according to the invention is shown in FIG. 4, which represents a special burner device, the reaction chamber D forming with the pre-combustion chamber C a Venturi tube E into which the halide is introduced. The Venturi shape enables a partial vacuum and high speed to be achieved in the narrow space between the pre-combustion chamber and the reaction chamber, thereby facilitating mixing.

The advantages of this arrangement (if they flame for the combustion of titanium tetrachloride with an auxiliary ¹ uses of carbon monoxide) are:

faster and more efficient mixing of the gases;

a substantial increase in the number of nucleators produced with their better utilization;

an increase in the amount of titanium dioxide yielded per hour while being economical at the same time Consumption in carbon monoxide;

improved properties of the pigments.

The F i g. 5 and 6 are explained in example 2. The following examples illustrate the invention.

example 1

An aluminum burner of the type shown in FIG. The type shown in Figure 1 is placed in a cylindrical furnace The total height of the apparatus is 150 cm, its diameter 45 cm. He is with 2.5 m »water cooled per hour and 50 m per hour »

Oxygen 80 m and 155 m ^J monoxide ⁸ a mixture of titanium tetrachloride and oxygen, 33 volume percent and 67 volume percent oxygen tetrachloride containing charged.

The quality of the product corresponds to that of example 2.

Example 2

A reaction furnace is used to produce titanium dioxide with pigment properties as rutile or anatase of any type is used, but preferably an oven with a discharge device for the hot gases containing titanium dioxide, as described in French patent 1,307,280. Of the The burner shown in FIG. 4 with the dimensions given there is arranged in this furnace.

^{45 m s of} oxygen and 70 m ^{3 of} an auxiliary fuel gas containing carbon monoxide, which consists of 75 percent by volume of carbon monoxide, 5 percent by volume of carbon dioxide and 20 percent by volume of nitrogen, are introduced into the burner per hour. It is introduced through a single pipe, that is, the pipe for introducing nitrogen is not used. A mixture of titanium tetrachloride and oxygen with 39 to 40 percent by volume of titanium tetrachloride is introduced in an amount of 215 m ^s per hour.

304 kg of titanium dioxide are obtained per hour, its statistical distribution from the point of view of Particle size distribution is very interesting. The particle size distribution of different samples according to Weight and number gives a very valuable indication of the pigment qualities of the various Types of titanium dioxide as shown in FIG. 5 and 6 of the drawing. F i g. 5 shows the statistical Distribution of particles in percent by weight and angstrom units. The weight percent will be calculated according to the following formula:

Statistical volume of all particles corresponding to a given size

Statistical volume of all tested particles

Fig. 6 shows the distribution of the particle size of the same sample as in Fig. 5, with the difference that the percentage distribution according to the number of particles tested as a function of the particle size is shown. Each point shown in the curve represents the percentage of particles that have a diameter of a given size range. This range is obtained by taking the mean values the particle sizes grouped together to determine the method of calculation and presentation of results to simplify. The average diameter of the particles is obtained according to the following formula:

Sum of the statistical volumes
of all measured particles

Sum of the statistical surfaces
of all measured particles

It is generally known that a white pigment has good coloring and hiding power since the size of its particles corresponds perfectly to the wavelength of the light rays that brighten the products on which it is applied, such as: B. paintings, glass, enamel, plastic, textiles, Paper and the like

The wavelength of the visible luminous spectrum extends between 2000 and 8000 A. The pigment particles should have a size that is as close as possible to half the wavelength of light, in that they meet is.

From this it follows that, if one wants to achieve the maximum of the reflected light and the maximum of the opacity, it is imperative that the dimensions of the grains be as close as possible to between the limits 1000 and 4000A. Within these dimensional limits, the mass distribution of the grains can easily be shifted towards the fine particles (curve A in FIGS. 5 and 6) or towards the coarse particles (curve B in FIGS. 5 and 6).

The products of types A and B represent the limits of these deviations, outside of which the essential pigment properties, color strength and hiding power, decrease sharply. The product of type C in FIG. 5 and 6, obtained by following the procedure of Example 2, are within the limits and therefore have good pigment properties. The mean diameter of the particles of the product of type C is 1922 A and lies between »ο 1800 and 2500A, the mean diameters of the products of types A and B.

Curve D (F i g. 5 and 6) represents the granulometric mass distribution by weight and number of a product produced by the method of Swiss Patent Application 265 192. The product has a not very good granulometric mass distribution with regard to weight and number. The curves are much more flattened and extend outside the limits defined above as necessary. The mean diameter is 3238 Å and is therefore much too high and leads to a loss of luminosity of 15 to 20%.

Example 3

A burner with pre-combustion and reaction chambers of the type shown in FIG. The type shown in FIG. 1 is arranged in an oxidation furnace, as described in French patent specification 1307 280, with which titanium dioxide can be continuously obtained. The main features of the burner are as follows: The pre-combustion chamber C has the shape of an elongated drum with a height of 530 mm and a maximum diameter of 130 mm. The reaction chamber D is cylindrical and has a diameter of 130 mm and a height of 390 mm. The injection openings m 4 and mS have a diameter of 25 mm. A total of eight of these openings are provided, which are arranged symmetrically in the upper part of the reaction chamber. Its diameter is less than the diameter of the opening ml through which the mixture of metal chloride and oxygen is introduced into the burner head. In the burner head there are also the separate openings in the inlet kl and gl for the carbon monoxide and the oxygen.

First, the auxiliary flame is formed as follows: Oxygen in an amount of 60 m ^s / hour is supplied through the opening gl. and through opening A: 1

Carbon monoxide in an amount of 100 m ³ / hour. introduced and the mixture lit. This creates a powerful hot flame. When the gases coming from the pre-combustion chamber C have heated the inner walls of the reaction chamber, a mixture of titanium tetrachloride and oxygen, in an amount of 55 mVh. Titanium tetrachloride and 72 m ^s / h. Oxygen introduced so that the mixed gases 44.5 volume percent

cent titanium tetrachloride. TiO ₂ is continuously used in an amount of 195 kg / hour. produced.

All production samples analyzed show pigment quality and excellent properties and Particle size distributions.

Example 4

In an oxidizing furnace that recirculates all combustion gases to cool the produced Titanium dioxide, as described in British Patent 673,725, is a carbon monoxide burner with a reaction chamber of reduced size, as shown in FIG. 2 is installed. This burner has the inlet openings required for the reaction gases. The diameter the openings for the entry of carbon monoxide and oxygen are 65 and 40 mm, respectively. The pipe for admitting the mixture of titanium tetrachloride and oxygen has a diameter of 100 mm. *> The total height of the combustion head is 550 mm and the height of the pre-combustion chamber is 725 mm. It are eight openings, each 18 mm in diameter, for the injection of the reaction gases at an angle of 45 ° to the gases of the auxiliary flame.

The burner is charged under the following conditions: The auxiliary flame is set at 60 mVh. Oxygen and 100m ^s / h. a gas containing 67 percent by volume of carbon monoxide. The chloride flame is obtained by injecting a gaseous mixture of titanium tetrachloride and oxygen through the eight injection ports mentioned above. The mixture is from 67 m ^s / h. Titanium tetrachloride and 90m ^s / h. Oxygen is formed and contains 42.5 percent by volume of titanium tetrachloride. The flame obtained in the furnace is constant and homogeneous. As in other burners according to the invention, it is sharply separated from the auxiliary flame, although the size of the reaction chamber is very reduced. The titanium dioxide is in an amount of 236 kg / hour. produced with 7 kg recoverable residue and has pigment properties.

The method according to the invention can not only in the oxidation of titanium tetrachloride in the Vapor phase are used, but also in the oxidation of other metal chlorides, such as e.g. the chlorides of aluminum, iron, zirconium, hafnium and niobium, all of which are Temperature below 500 ° C can be evaporated at atmospheric pressure. Essentially be uses the same technique and apparatus as described above.

The titanium dioxide pigments obtained according to the invention are fine and regular and can therefore z. B. can be used for the pigmentation of plastics.

Claims (6)

Patent claims: 1. A process for the production of fine metal oxides by incinerating a mixture of Metal chloride and oxygen using an auxiliary gas flame, the currents of the Cross reaction gas mixture and the auxiliary fuel gas-oxygen mixture, characterized in that that the auxiliary fuel gas in a pre-combustion chamber before entering the reaction chamber ignited, the ignited auxiliary fuel gas through a single central opening in initiated the reaction chamber and the reaction mixture in several jets from the outside is introduced into the burning stream of the auxiliary fuel gases (fire gases), with the direction each jet crosses the flow axis of the fire gas. 2. The method according to claim 1, characterized in that the reaction gases in one Angle of 45 to 90 ° to the direction of movement of the flow of the auxiliary fuel gas are introduced. 3. The method according to claim 1 or 2, characterized in that as an auxiliary fuel gas in known Way carbon monoxide is used. 4. Device for performing the method according to claims 1 to 3, characterized by a cylindrical reaction chamber (D) which is in open communication with the pre-combustion chamber (C) and forms a common axis with it, wherein a plurality of channels (τη 4 , mS) with a small diameter for supplying the reaction gas mixture into the reaction chamber (D), the axes of which intersect the axis of the reaction chamber (D), and through a cooling water jacket around the reaction and pre-combustion chamber. 5. Apparatus according to claim 4, characterized in that the pre-combustion chamber and the Reaction chambers are designed together like a venturi. 6. Arrangement for performing the method according to claims 1 to 3, characterized by a multi-device furnace according to claims 4 and 5. Considered publications:
Swiss patent specification No. 265 192. When the application was announced, two priority documents were displayed. For this purpose 2 sheets of drawings 709 589/330 5. »7 ® Bundesdruckerei Berlin