FI58112C - FOERFARANDE FOER FRAMSTAELLNING AV FINFOERDELADE OXIDER AV GRUNDAEMNEN VILKAS KLORIDER AER LAETTFLYKTIGA - Google Patents

Description

I ANNOUNCEMENT

jggr · lbj (11) UTLÄGGNINGSSICRIFT böl 1 2 C Patent filed 10 12 1; ό0 · # »^ Patent meddelat ^ (51) Kv.ik.Wci.3 C 01 G 23/04, C 01 B 13/22 ENGLISH I —FI N LAN D (21) PmnttihtliMNu * —P «tiw« ft »ekRln | 2920 / lk (22) H »k * ml * clouds - Aiwftknlngsdag 07.10.7b (23) Alkupttlvt —Gltt) (h« tsda | 07.10.7 ^ +

(41) Tullut JuIMmIuI - Bllvlt offuntllg 09 ,. 7C

Patent and Registration Office (44) NihtivtoJp ™ j. month.Jullai.un date.-

Patent · och registerstyralsen AniOktn utiagd och uti.tknftm pubiicund 29.08.80 (32) (33) (31) Pyydetty ttuolkwi — Begird prlorltet o8.10.73

Federal Republic of Germany Förbundsrepubliken Tyskland (DE) P 23501 + 69.0 (71) Kronos Titan-GmbH, 5090 Leverkusen 1, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (72) Achim Hartmann, Leverkusen, Achim Kulling, Lummkusen, Leverkusen,

Leverkusen, Federal Republic of Germany Tyskland (DE) (7I +) 0y Roister Ab (5I +) Method for the preparation of finely divided oxides of elements with readily volatile chlorides

The invention relates to a process for the preparation of finely divided oxides of elements whose chlorides are easily volatile by reacting the corresponding chlorides with oxygen or an oxygen-containing gas at high temperatures.

It is known to produce finely divided oxides, e.g. titanium oxide, by introducing a volatile chloride, e.g. titanium tetrachloride and oxygen or an oxygen-containing gas, into the oxidation chamber either mixed together or separately. In the oxidation chamber, a reaction takes place at high temperatures to form the corresponding oxide, e.g. titanium dioxide, in finely divided form and chlorine. To achieve the required high temperatures, at least one of the two reaction components must be heated before being introduced into the oxidation chamber and / or some other substance must be introduced which is either heated to high temperature before being introduced into the oxidation chamber or combusted inside the oxidation chamber to generate heat. The oxidation chamber may be either empty or may have a fluidized bed of coarse particles. The resulting mixture of gas and solid, which is generally above 1000 ° C, must be cooled after leaving the oxidation chamber before the solid is separated from the mixture. Cooling can be performed by mixing the mixture with cold gas and / or indirectly in an externally cooled heat exchanger. The separation of the pigment is performed in a filter and / or cyclone and / or in another suitable device. The oxide can be separated dry or by washing with a suitable, for example aqueous liquid. After separation of the pigment, the chlorine is ground to a chlorination plant to re-produce the corresponding chloride from the ore or some other oxide material that is re-used to produce the starting oxide. To this end, it is necessary to pressurize the chlorinated gas before it is introduced into the chlorination plant in order to overcome the pressure losses in the chlorination plant. In this connection, difficulties arise, in particular due to the fact that the acetic-containing gas contains small amounts of unreacted chloride, oxide chloride and oxide particles which were not retained by the separation device during the separation of the pigment. These substances adhere to the compressors and form deposits. This causes recurring malfunctions. Therefore, it is absolutely necessary to release chlorine-containing gas from these substances before compressing the gas.

German application 1 817 347 proposes washing the gas at a temperature not exceeding 50 ° C with concentrated sulfuric acid and then compressing it in a liquid-piston-compressor device using concentrated sulfuric acid as the working liquid. The gas is then passed to a separator to remove residual solids and sulfuric acid before being introduced to the chlorination plant. The method has significant drawbacks. The substances separated by washing react to form sulphate and are lost from the process. In addition, due to the formation of sulphate, the viscosity of sulfuric acid increases, so that it is difficult to handle and often has to be replaced by fresh sulfuric acid. The cold compressed gas must be reheated before being fed to the chlorination plant or, in addition, a considerable amount of fuel, for example coke, must be burned in the chlorination plant to maintain chlorination. The whole plant with its refrigeration units, washing equipment, compressors and residue separation equipment is very complex, which makes it difficult to control the process. The devices are prone to interference and cause high repair costs.

A new process has now been invented for the preparation of finely divided oxides of elements whose chlorides are easily volatile by reacting the corresponding chlorides with oxygen or an oxygen-containing gas at high temperatures, which process does not have the said drawbacks. The process is characterized in that the reaction is carried out at an overpressure of less than 1.4 aty and the reaction mixture is passed, due to the overpressure, without further compression, through the subsequent steps to the chlorination step, where the chloride in question is reconstituted.

An essential advantage of this method is that the pressure in the oxidation chamber is sufficient to pass the reaction mixture through all subsequent parts of the plant so that after oxide removal, the reaction mixture 58112 can be fed to the chlorination plant with sufficient overpressure without the need for intervening compressors. The only point where pressure is generated is the point where the reaction components are introduced into the oxidation chamber. In this case, a much higher load on the oxide separation device is possible than in known methods. In the case of the same amount of material to be treated, the separating device can be smaller or the same amount of material to be treated can be increased by dimensioning the separating device. The same applies to the oxidation chamber itself and to the cooling device downstream of the oxidation chamber. A further advantage of the method according to the invention is that it is not necessary to wash the gas released from the oxides with sulfuric acid and to carry out post-purification. With the omission of the washing plant, the disadvantage that unreacted chlorides and oxide chlorides are lost is also eliminated. On the contrary, these can be passed through the entire plant to the chlorination dam. The oxidation of the chloride can therefore be carried out, depending on the circumstances, in such a way that it takes place incompletely, i.e. that a significant portion of the chloride does not react in the oxidation chamber. Until now, the oxidation has had to be carried out at the highest possible temperatures in order to make the chloride reaction as complete as possible, while in the process according to the invention it is possible to work at lower temperatures. In this case, on the one hand, energy can be saved for preheating the reaction components and, on the other hand, the cooling device for the reaction mixture can be smaller and / or simpler than in known methods. In the case where flammable auxiliary gases are used, the amount required is less than in the corresponding known methods.

They can also be omitted altogether. Since no compressors are required after the oxide is separated from the gas mixture, it is not necessary to cool the gas to a lower temperature than is absolutely necessary! necessary for the separation of the oxide. As a result, it is possible to lead the gas to the chlorination plant at a higher temperature than before. In this way, the need for fuel in the chlorination plant is reduced.

The whole plant with its oxidation chambers and chlorination plants is simple in structure; the process can be easily adjusted.

The lower limit of the overpressure used in the oxidation chamber depends on e.g. the dimensions of the whole plant, the quantities of private substances to be used and other reaction conditions. They can be easily figured out to try on a case-by-case basis. All that matters is that the overpressure in the oxidation chamber is sufficient to overcome the pressure drop in the freezing plant, the oxide separation plant and the chlorination plant.

It is preferable if the reaction mixture formed in the reaction is cooled after leaving the oxidation chamber by cooling indirectly in a heat exchanger. Improved heat transfer is achieved due to overpressure in the line. No compressors are required for the cooling circuit. It is also not necessary to strongly cool the portion of the reaction gas required to cool the reaction mixture.

i 58112

A preferred embodiment of the invention is based on cooling the reaction mixture under an overpressure between 200 and 400 ° C and, after separation of the oxide, without further cooling and without using compressors, to a chlorination plant where the chloride is re-formed due to reaction with ore or other oxidic material. Chlorine and unreacted chloride are recycled without losses and disturbances throughout the plant.

A particularly preferred embodiment of the process according to the invention is characterized in that the element is titanium and a titanium dioxide pigment is prepared. In this case, titanium tetrachloride is reacted as chloride. Of course, in addition to titanium tetrachloride, it is possible to introduce into the oxidation chamber, in a manner known per se, small amounts of other substances which promote the formation of pigment, in particular rutile pigment, or affect the size of the particles. Examples are aluminum chloride, water vapor or alkali metal compounds. It is also possible to add substances which form a coating on the pigment particles after the reaction in a manner known per se.

In this case, the process according to the invention is particularly advantageous because, often with the subsequent addition of other metal halides to the hot reaction mixture, these metal halides react with a part of the titanium dioxide formed to form titanium tetrachloride. The titanium tetrachloride formed interferes as little as the unreacted titanium tetrachloride in the oxidation chamber during further processing of the reaction mixture.

Other examples of volatile chlorides from which the corresponding oxides can be prepared include e.g. chlorides of silicon, aluminum and zirconium.

Another preferred embodiment of the process according to the invention is characterized in that the element is iron and iron oxide is produced. Most titanium ores are highly ferrous and the production of titanium dioxide pigments produces large amounts of iron compounds that burden the process and are unusable or difficult to use. Therefore, prior to the production of titanium dioxide, efforts have often been made to remove at least some of the iron from the ore in order to use an iron-poor material for the production of titanium tetrachloride. In addition, the titanium tetrachloride formed must be released from the ferric chloride formed at the same time. In both cases, large amounts of iron trichloride are formed. These can be converted by means of the process according to the invention into iron oxide, which can be used as a pigment or which is suitable for the production of metallic iron, without energy costs.

The oxide can be removed from the reaction mixture leaving the evacuation chamber in a manner known per se by washing with a liquid; however, it is particularly advantageous if the separation of the oxide is carried out dry in a filter and / or a cyclone. Due to the overpressure in the reaction mixture, the oxide concentration therein increases and the formation of agglomerates intensifies, which can be easily separated. Therefore, the oxide separation device may be less similar to the known separation results than in the known methods, or if the oxide separation device is the same size, its performance is higher. In addition, the pressure drop is small, so that the pressure remaining behind the oxide separation device is sufficient to transfer the mixture to the chlorination plant without renewed compression. By selecting a suitable filtration material or wall material for the cyclone, the separation of the oxide can be performed at relatively high temperatures, thus saving energy in chlorination. In the case of oxide separation, the liquid or liquid vapors do not impure the reaction mixture and no losses of unreacted chloride occur, which would occur when performing the green separation of the detergent.

Example An oxidation chamber was used which was constructed in substantially the same manner as the chamber described in German Patent 1,592,529 and had an inner diameter of 150 mm and a length below the titanium tetrachloride feed points of 1000 mm. To this oxidation chamber were introduced 96 Nm / h of oxygen and 500 kg / h of titanium tetrachloride, preheated to 250 ° C, respectively.

350 ° C.

Together with the titanium tetrachloride, so much aluminum chloride was introduced that the titanium dioxide pigment formed contained $ 2.00 In addition, 32 NmV * 1 of room temperature carbon monoxide was introduced and burned at the top of the oxidation chamber. The reaction took place under an overpressure of 1.2 aty. Immediately upon leaving the oxidation chamber, the temperature of the reaction mixture was 1500 ° C. The reaction took place in 99 »7 estonian. The reaction mixture was passed through a 9-meter-long aluminum cooling tube having an inner diameter of 100 mm and cooled externally with water. To prevent the formation of pigment deposits, 10 kg / h of sand was introduced into the reaction mixture before being introduced into the cooling tube. The reaction mixture exited the cooling tube at 400 ° C; the pressure had dropped only slightly. The reaction mixture was then passed to a filtration plant 2 with a filter surface area of 5 m. The pressure drop in the filtration plant was 0.061 at. The sand and separated pigment were removed by means of a spiral and separated and further treated in a known manner. Upon leaving the filtration plant, the gas pressure was 1.0 aty and the temperature was 350 ° C and it was passed directly to the chlorination plant, where titanium tetrachloride was reconstituted.

Claims (6)

6,58112 A process for the preparation of finely divided oxides of elements whose chlorides are volatile by reacting the corresponding chlorides with oxygen or an oxygen-containing gas at high temperatures, separating the oxides and passing the reaction gases to the chlorination step, characterized in that the reaction is carried out under 1 ° C is passed, due to overpressure, without further compression, through the subsequent steps to the chlorination step, where the chloride in question is reconstituted, Process according to Claim 1, characterized in that the reaction mixture formed in the reaction is cooled after it has left the oxidation chamber by means of indirect cooling in a heat exchanger, Process according to Claims 1 and 2, characterized in that the reaction mixture is cooled under an overpressure to between 200 ° C and 100 ° C and, after separation of the oxide, is passed without further cooling and without the use of compressors to a chlorination plant. Process according to Claims 1 to 3, characterized in that the element is titanium and a titanium dioxide pigment is prepared. Process according to Claims 1 to 3, characterized in that the element is iron and iron oxide is produced. Process according to Claims 1 to 5, characterized in that the oxide separation is carried out dry in a filter and / or in a cyclone.