GB2051022A - Process and apparatus for preparing titanium tetrachloride - Google Patents

Abstract

A process for preparing titanium tetrachloride in an apparatus comprising a shell (1) made of an upper part (4) and a lower part (5) interconnected by a tapered part (6) and having a top (2) and a tapered bottom part (3), wherein there is fed into a bed of a carbonaceous material having a temperature of from 600 to 700 DEG C, simultaneously and co-currently, through an inlet (9) a starting feedstock comprising a titanium-containing material and a carbonaceous material in a current of gaseous chlorine and through en inlet (10) an additional current of gaseous chlorine, wherein the bed of carbonaceous material comprising the zone of reaction of the starting feedstock with the gaseous chlorine to produce titanium tetrachloride is formed due to the continuous supply into the reaction zone through an inlet (7) of a carbonaceous material fed counter-current to the supplied starting feedstock and gaseous chlorine in an amount sufficient to fill more than one third of the reaction zone volume. <IMAGE>

Description

SPECIFICATION Process and apparatus for preparing titanium tet chloride The present invention relates to a process for preparing titanium tetrachloride and to an apparatus for carrying out the process.

The present invention in one aspect provides a process for preparing titanium tetrachloride, comprising feeding into a bed of a carbonaceous material having a temperature of from 600 to 700"C, simultaneously and co-currently, (1 ) a starting feedstock comprising a titanium-containing material and a carbonaceous material in a current of gaseous chlorine and (2) an additional current of gaseous chlorine, wherein the bed of carbonaceous material comprising the zone of reaction of the starting feedstock with the gaseous chlorine to produce titanium tetrachloride is formed due to a continuous supply, into the said reaction zone, of a carbonaceous material fed counter-current to the supplied starting feedstock and gaseous chlorine in an amount sufficient to fill more than one third of the reaction zone volume.

By means of the present invention the specific productivity of the process for the preparation of titanium tetrachloride may reach 1.5 to 2.0 ton per m2 per hour, a yield of titanium tetrachloride equal to 94-96% may be attained, the production costs of the final product may be reduced by 50-60%, and the content of a solid residue in the final titanium tetrachloride may be reduced by 3-5 times as compared to prior art processes.

To additionally increase the yield of titanium tetrachloride and eliminate losses oftitaniumcontaining material during chlorination thereof, an oxychloride and/or chloride titanium-containing pulp may be added to the reaction zone cocurrentlywith the supplied carbonaceous material every 3 to 10 sec at a rate of at most 0.8 m/sec.

The invention in another aspect provides apparatus for carrying the process for preparing titanium tetrachloride according to the first aspect of the invention, comprising a vertical cylindrical shell made of upper and lower cylindrical parts interconnected by a tapered part with an angle of taper directed towards the upper cylindrical part of the shell equal to 30-90 , and a top rigidly secured to the upper part of the cylindrical shell, the cylindrical shell having a tapered bottom part, at least one inlet for admission of the starting feedstock in a current of gaseous chlorine arranged at the junction of the lower cylindrical part of the shell with the said bottom part, at least one inlet for admission of gaseous chlorine arranged in the bottom part of the shell at a height equal to 1/3 - 2/3 of the height of the bottom part, and an outlet for discharging by-products of the reaction arranged at a height from the junction of the lower part of the shell with the said tapered part equal to 1/20 - 1/4 of the internal diameter of the upper part of the shell.

To prolong the service life of the apparatus and reduce its manufacturing costs, it is preferred to provide a casing over the upper cylindrical part of the shell and the top of the shell so as to form, together with the top and the shell upper part wall, a cavity for the supply of a cooling agent.

Owing to the above-mentioned arrangement of the inlets for admission of the starting products and the particular structure of the shell, it is now possible to ensure a uniform distribution of chlorine over the entire volume of the apparatus and, consequently, to increase the specific productivity of the process and the yield of the desired product, i.e. titanium tetrachloride.

The present invention is intended for preparing titanium tetrachloride from a starting feedstock preferably comprising 75-80% by weight of a titaniumcontaining material with a particle size of at most 0.1 mm including oxides of titanium, ferrous oxide, silica and chromium oxide, and 20-25% by weight of a carbonaceous material with a particle size of at most 0.15 mm such as pitch, petroleum or blast furnace coke.

A starting feedstock of the above-mentioned composition is obtained by intermixing the titaniumcontaining and carbonaceous materials in appropriate proportions in a suitable device such as a conical drum granulator.

The starting feedstock is admitted, in a current of gaseous chlorine, into a bed of a carbonaceous material, e.g. into a bed of lamp pitch, petroleum or blast-furnace coke.

It has been found that the amount of the carbonaceous material, wherein the reaction of formation of titanium tetrachloride occurs, should constitute over 1/3 of the reaction zone volume. Failure to fulfil this requirement (pressure of the supplied gaseous chlorine is preferably 0.7 atm.g) results in a lowered process rate. The carbonaceous material is fed continuously into the reaction zone in a direction countercurrent to the supplied gaseous chlorine and the starting feedstock. The supply rate of the carbonaceous material is preferably equal to about 0.00015 m/sec.These conditions of supply of the starting reagents ensure an intensive heat-exchange between particles of the starting feedstock and the carbonaceous material, increase the time of contact between the reagents, and enable acception of chlorine by the titanium-containing material up to 100%; in doing so, losses of the titanium-containing material in the form of dust with the reaction products are reduced, thus largely preventing contamination ofthe resulting titanium tetrachloride.

It should be noted that the portion of the gaseous chlorine stream admitted along the starting feedstock should preferably constitute 10 to 15% of the total amount of gaseous chlorine supplied into the reaction zone.

To increase the yield of titanium tetrachloride, to permit utilization of the production wastes, and to prevent the titanium-containing starting material from being lost as dust with the reaction products, it is preferable that an oxychloride and/or chloride titanium-containing pulp be admitted into the reaction zone every 3-10 sec at a rate of at most 0.8 m/sec. Oxychloride and/or chloride titaniumcontaining pulps comprise waste products resulting from the production of titanium tetrachloride upon clarification of the condensed titanium tetrachloride.

Such a pulp is a mixture of chlorides of iron, aluminium, silicon and vanadium and/or oxych chlorides of aluminium, silicon and titanium with finely divided particles of the titanium-containing material and carbonaceous reducing agent. The content of solids in this mixture (pulp) is about 475 g/l.

The invention will be further described, byway of example only, with reference to the accompanying drawing, which is a side elevational view, partly in section, of an apparatus for carrying out the process according to the invention for preparing titanium tet rachloride.

The apparatus shown in the drawing comprises a substantially vertical steel shell 1 in the upper part of which there is a ridigly mounted top 2. The bottom part 3 of the cylindrical shell 1 tapers in the shape of a frustrum. The cylindrical shell 1 is made oftwo cylindrical parts of different diameter, the upper part 4 of the shell 1 having an internal diameter 1.5 times greater than the internal diameter of the lower part 5 of the shell 1. By fulfilment of this requirement an optimal speed of streams of the reagents is obtained togetherwith an optimal yield oftitaniumtetrachloride in the practical operation of the apparatus.

The upper part 4 and the lower part 5 of the shell 1 are connected by means of a tapered part 6. To meet the requirement of the ratio between the inner diameters of the upper and lower parts of the shell 1, the tapered part 6 has an angle oftaperadirected towards the upper part 4 of the shell equal to 30-90 .

Increasing this angle of taper above 90" will result in retarding the movement of the starting products in the apparatus, i.e. the walls of the tapered part 6 will form a threshold in the path of the reagents. Reduc ing the angle of taper below 30 will result in such modification of the speeds of the reagents so as to cause an intensive carry-over of un reacted components from the apparatus.

In the top 2 ofthe shell 1 there is an inlet pipe 7 for the supply of carbonaceous material into the apparatus. An inlet pipe 8 for admission into the apparatus of chloride and/or oxychloride pulps is provided in the wall ofthe upper part 4 ofthe shell.

At the junction of the tapered bottom part 3 with the lower part 5 of the shell 1 there are inlet pipes 9 for admission into the apparatus of the starting feedstock consisting of the titanium-containing material and a reducing agent, i.e. carbonaceous material, in a current of gaseous chlorine. There are also provided inlet pipes 10 for admission of gaseous chlorine which are provided in the walls of the bottom part 3 at a height equal to 1/3 to 2/3 of the height of the tapered bottom part 3. The thus selected height of the inlet pipes 10 ensures a uniform distribution of gaseous chlorine overthe entire volume of the apparatus thus resulting in an increaseciyield of titanium tetrachloride. It is advisable to provide at least four inlet pipes 10 for admission of gaseous chlorine.In the shell 1, at a height from the junction of the lower part 5 df the shell 1 with the tapered part 6 equal to 1/20 -1/4Ofthe internal diameterofthe upper part 4 of the shell 1, an outlet pipe 11 its provided for the removal from the apparatus of vapour-gas by-products of the reaction, such as car bon, oxides of silicon, and partial oxides of titanium.

When the pipe 11 is placed atthe height exceeding 1/4 of the internal diameter of the upper part 4 of the shell 1, this requires an increased thickness of the bed of the carbonaceous material which, in turn, necessitates an increased pressure in the pipes for admission of gaseous chlorine. When the pipe 11 is placed at the height below 1/20 of the internal diame terofthe upper part4 of the shell 1, the productivity of the apparatus is considerably reduced.

An outlet pipe 12 for the removal from the apparatus of vapour-gas products of the reaction including titanium tetrachloride is provided in the uppermost end of the part 4 ofthe shell 1.

In the lowermostend of the bottom part 3 there is provided an outlet pipe 13 for the removal from the apparatus of the reaction products consisting of carbon, small amounts of titanium dioxide and other metal oxides.

There is rigidly secured to the upper part 4 of the shell 1 and the top 2 thereof a casing 14 forming with the top 2 and walls ofthe shell 1 a cavity for a cooling agent. The casing 14 is fixed at a distance of at least 50 mm from the shell 1. The casing 14 can be manufactured from a thin sheet of steel or glass-metal fibres. The cooling agent is water.

The casing 14 makes it possible to avoid lining of the shell 1 at this location, thus reducing the manufacturing costs of the apparatus and increasing its service life.

The shell walls not protected by the casing 14 are lined with a thermo- and chloro-resistant material such as a high-alumina refractory material with a porosity of at most 12%.

The preparation oftitanium tetrachloride in the apparatus described above is conducted in the following manner: Prior to charging the reagents into the apparatus, a temperature of 600-800"C is created inside the shell 1 by means of an ejection burner fed with natural gas via the pipes 10. After achieving this temperature the burners are removed. Acarbonaceous material such as a pitch, petroleum or blast-furnace coke maintained at a temperature of at least 600"C is charged into the apparatus via the inlet pipe 7 at a rate of about 0.00015 m/sec. The carbonaceous material is charged in an amount which is sufficient to fill more than 1/3 of the entire volume of the reaction zone. It has been found that the thickness of the carbonaceous material bed should be varied within the range of from 1.0 to 2.5 m. Thereafter, the supply of the starting feedstock and gaseous chlorine is started.

To this end, gaseous chlorine, e.g. gaseous anodic chlorine-gas with a concentration of chlorine within the range of from 68 to 70% (the balance being oxygen), is fed through the inlet pipes 10. The speed of gaseous chlorine atthe outlets of ejection nozzles (not shown) at a diameter of the latter of 15 mm is equal to 432 m/sec. The starting feedstock is supplied through the inlet pipes 9, which feedstock consists of a titanium-containing material and a reducing agent, i.e. carbonaceous material, in a stream of gaseous chlorine. The portion of the chlorine stream supplied with the starting feedstock is varied within the range of from 10 to 15% of the total amount of gaseous chlorine supplied into the process.

The preparation oftitanium tetrachloride in the apparatus occurs on account of the heat evolved in the following chemical reactions: TiO2 + 2C + Cl2 = TiC14 + 2CO + Q TiO2 +0+ C12 = TiC14 + cm2 + Q The process is conducted with continuous discharge of the reaction products from the apparatus.

Thus, a vapour-gas mixture comprising TiCI4, SiCI4, Al Cl3, FoCI3, VOCI3, Fez 12, CO, CO2, O2 and COCK, is discharged from the apparatus via the pipe 11. The unreacted remaining mixture containing TiO2, C, MgCI2, CaCI3, MgO and CaO is withdrawn via the pipe 13.

Titanium tetrachloride formed in the course of the reaction of the starting feedstockwith gaseous chlorine is discharged from the apparatus via the pipe 12. The resulting titanium tetrachloride contains substantially no impurities.

A chloride and/or oxychloride titanium-containing pulp is added into the apparatus via the pipe 8 at a temperature within the range of from 400 to 1,00000.

It is preferable to supply the pulp at a rate of at most 0.8 m/sec every 3-10 sec.

Dust-like fractions of the titanium-containing material and the carbonaceous reducing agent entrained with the vapour-gas mixture are wetted by the supplied pulp and descend into the reaction zone; therewith, titanium tetrachlo ride evaporates from the pulp simultaneously with conversion of oxych chlorides of titanium and aluminium to chlorides and after-chlorination of fine particles of titania to titanium tetrachloride.

This process for preparing titanium tetrachloride makes it possible to reduce losses due to wetting and recycling fines of the titanium-containing material and carbonaceous reducing agent, and to recover titanium tetrachloride from pulps, thus increasing the productivity of the apparatus by 15-20%.

At the above-mentioned rates of supply of the starting material, gaseous chlorine and carbonaceous material, there occurs intensive heat-exchange between particles of the titanium-containing material and the carbonaceous material and their heating to a temperature of 980"C.

The carbonaceous material is partly combusted due to the reaction with oxygen of the chlorine gas with the formation of carbon monoxide. At high temperatures and underthe above-mentioned conditions of supply of the reagents there occurs an intensive chlorination of the titanium-containing material with the production of titanium tetrachloride.

This process makes it possible to prolong the time of contact between the titanium-containing material and gaseous chlorine in a multi-channel mobile bed of the carbonaceous material and elevate the accepting of chlorine by the titanium-containing material up to 100%, lower losses of the chlorinated material thus eliminating contamination of the resulting titanium tetrachloride, and to increase the degree of recovery of the principal component up to 93.7%.

The invention will be further described with reference to the following illustrative Examples.

Example 1 75% by weight of a titanium-containing material with a particle size of 0.1 m containing oxides of titanium, ferric oxide, silica, alumina and chromium oxide and 25% by weight of a pitch coke with a particle size of 0.15 mm were mixed in a drum granulator.

The resulting starting material with a content of car bon of 24.3% by weight was admitted in a stream of gaseous chlorine through inlet pipes 9 into the reaction zone into a bed of a pitch coke (temperature of 650"C) continuously fed from the pipe 7 countercurrently with the starting material. Gaseous chlorine was fed into the bed of pitch coke through pipes 10. The speed of the ascending stream of gaseous chlorine was 0.148 m/sec, and the speed of the gas stream in the coke bed was 0.27 m/sec. The process temperature was varied within the range from 780 to 850"C, and the chlorine supply rate was 9 1/mien. As a result of the treatment of 1,660 g of the starting material there were obtained 1,690 g of titanium tetrachloride.No break-through of chlorine was observed with increasing chlorine supply rate up to 15 1/min at continuous charging and discharg ing operations. The content of titanium oxide in the by-products of the reaction was 16.3%.

Example 2 80% by weight of a titanium-containing material with a particle size of 0.09 mm including oxides of titanium, ferric oxide, silica, alumina and chromium oxide and 20% by weight of a petroleum coke with a particle size of 0.15 mm were intermixed in a drum granulator. The resulting starting material was con tinuouslyfed, over 7 hours, in a current of gaseous chlorine through pipes 9 into the reaction zone into a bed of petroleum coke (temperature of 700"C) continuously fed via the pipe 7 counter-currently to the starting material. The thickness of the petroleum coke bed was 1.8-2.0 m. Gaseous chlorine was fed into the bed of petroleum coke through pipes 10. The rate of the ascending stream of chlorine was 0.148 m/sec, and the flow rate of gaseous chlorine was 1,200-1,400 kg/hr.The process temperature was 980"C. Treatment of 7.0 tons of the starting material resulted in 10.5 tons of titanium tetrachloride. The yield oftitanium tetrachloride was 93.7%.

Example 3 77% by weight of a titanium-containing material with a particle size of 0.1 mm including oxides of titanium, ferric oxide, silica, alumina and chromium oxide and 23% by weight of a pitch coke with a particle size of 0.15 mm were mixed in a drum granulator.

The resulting starting material was introduced, in a stream of gaseous chlorine, through pipes 9 into the reaction zone into a bed of petroleum coke (temperature of 650"C) continuously fed via the pipe 7 counter-currently with the starting material. Gaseous chlorine was fed into the bed of petroleum coke through pipes 10. An oxychloride pulp containing, in percent by weight, titanium 17.5, iron 3.15, aluminium 2.48, silicon 0.22, magnesium 0.08, calcium 0.07, manganese 0.23, vanadium 0.11, chromium 0.14, chlorine 65.1, and oxygen 10.9, was fed into the apparatus via the pipe 8 every 3 sec. at a rate of 0.7 m/sec. The process temperature was 780-850 C. Fine particles of the titanium-containing material and the carbonaceous material (pitch coke) entrained with the vapour-gas mixture ,i1ed during the process were wetted with the pulp and descended back into the reaction zone of the apparatus. Therewith, titanium tetrachloride was evaporated and fine particles of titanium dioxide were after-chlorinated to titanium tetrachloride. The vapour-gas mixture effluent from the apparatus was condensed to recover titanium tetrachloride of a high purity grade of about 96-98%. The content of titanium in the waste products was at most 1%. The content of carbon was at most 10%.

Example 4 80% of a titanium-containing material with a particle size of 0.09 mm including oxides oftitanium, ferric oxide, silica, alumina and chromium oxide and 20% by weight of blast-furnace coke with a particle size of 0.15 mm were intermixed in a drum granulator. The resulting starting raw material was continuously fed, in a current of gaseous chlorine, via pipes 9 into the reaction zone into a bed of pitch coke (temperature of 680"C) continuously fed via the pipe 7 counter-currently to the starting material. The thickness of the pitch coke was 1.8-2.0 m. Gaseous chlorine was fed through pipes 10 into the bed of pitch coke.An oxychloride pulp consisting of, in percent by weight, titanium 18.8, iron 2.16, aluminium 3.0, silicon 0.11, magnesium 0.08, vanadium 0.16, oxygen 11.5, and chlorine 68.7 was fed into the apparatus via the pipe 8 every 10 sec. at a rate of 0.7 m/sec. The process temperature was within the range of from 780 to 850"C. Fine particles entrained with the vapour-gas mixture formed during the process were wetted with the pulp and descended into the reaction zone of the apparatus. Therewith, there occurred evaporation of titanium tetrachloride and conversion of oxychlorides of titanium and aluminium to chlorides thereof. The vapour-gas mixture effluent from the apparatus was condensed to recovertitanium tetrachloride of a high purity grade.

The yield of titanium tetrachloride was 97-98%. In by-products of the reaction there were contained at most 1%oftitanium oxide and 10%ofcarbon.

Claims (7)

1. A process for preparing titanium tetrachloride, comprising feeding into a bed of a carbonaceous material having a temperature of from 600 to 7000C., simultaneously and co-currently, (1) a starting feeds tockcomprising atitanium-containing material and a carbonaceous material in a current of gaseous chlorine and (2) an additional current of gaseous chlorine, wherein the bed of carbonaceous material comprising the zone of reaction of starting feedstock with the gaseous chlorine to produce titanium tet rachloride is formed due to a continuous supply, into the said reaction zone, of a carbonaceous material fed counter-current to the supplied starting feedstock and gaseous chlorine in an amount sufficient to fill more than one third of the reaction zone volume.

2. A process as claimed in Claim 1, wherein an oxychloride and/or chloride titanium-containing pulp is added co-currently with the supplied car bonaceous material every 3-10 sec at a rate of at most 0.8 m/sec.

3. A process for preparing titanium tetrachloride, substantially as herein described with reference to the accompanying drawing.

4. A process for preparing titanium tetrachloride, substantially as herein described in any of the foregoing examples.

5. Apparatus for carrying out the process for preparing titanium tetrachloride according to Claim 1, comprising a substantially vertical cylindrical shell made of upper and lower cylindrical parts interconnected by a tapered part with an angle of taper directed towards the upper cylindrical part of the shell equal to 30-909 and a top rigidly secured to the upper part of the cylindrical shell, the cylindrical shell having a tapered bottom part, at least one inlet for admission of the starting feedstock in a current of gaseous chlorine arranged at the junction of the lower cylindrical part of the shell with the said bottom part, at least one inlet for admission of gaseous chlorine arranged in the bottom part of the shell at a height equal to 113 213 of the height of the bottom part, and an outlet for discharging by-products of the reaction arranged ata height from the junction of the lower part of the shell with the said tapered part equal to 1/20-1/40fthe internal diameter of the upper part of the shell.

6. Apparatus as claimed in Claim 5, further comprising a casing provided overthe upper cylindrical part of the shell and the top of the shell, the casing forming, together with the top and the wall of the upper part of the shell, a cavity for a cooling agent.

7. Apparatus for preparing titanium tetrachloride, substantially as herein described with reference to, and as shown in, the accompanying drawing.