DE2551380C3 - Extraction of the titanium dioxide contained in red mud as titanium tetrachloride - Google Patents

Description

The invention relates to a method for obtaining the titanium dioxide contained in red mud as titanium tetrachloride.

Red mud (ie the residue of the alkaline digestion of bauxite during aluminum extraction) contains, depending on its origin, up to 20% TiO ₂ and stell! Therefore, especially today in a time of increasing raw material scarcity, a titanium tetrachloride represents. Since the waste product red mud costs the aluminum industry practically nothing, the production of titanium tetrachloride from red mud could be economical or become economical in the foreseeable future. Today titanium compounds are usually obtained technically from ilmenite or similar ores, which are considerably richer in titanium than red mud. II-menite ores contain, depending on their origin, 30 to 60% TiO ₂ . In addition to the leaching of such ores with acids, which yields more or less pure titanium dioxide, the chlorination of titanium dioxide-containing starting material in the presence of coal for the production of titanium tetrachloride is known. According to US Pat. No. 1,179,394, a mixture of titanium dioxide and carbon is heated until the volatile constituents are expelled, and then reacted with chlorine at 650 ° C. to form titanium tetrachloride. Beat: L. Terebesi and J. Kornyei (The Ronald Press Company, New York;; J. Barksdale, Titanium, 2 ^nd ed (1966), pp 437-438 Kohaszati Lapok 90 (1957), pp 460 to.) propose to first proceed to 800-930 ° C of red mud, then to chlorinate at 800 ° C, in order to first separate the bulk of the iron as iron trichloride, then to chlorinate aluminum, titanium and silicon together at 900 ° C and the resulting mixture of aluminum trichloride, To treat titanium tetrachloride, silicon tetrachloride and iron trichloride successively with aluminum oxide, titanium dioxide and iron oxide in order to convert the chlorides of aluminum, silicon and titanium into oxides.

The disadvantage of the process used today for the production of titanium compounds is that they occur of the ores commonly used for this purpose are not known in Germany. Red mud is against it a low value, but as a waste product from ongoing aluminum production or on Stockpiles inexpensively raw material available in considerable quantities.

In the process of L. Terebesi and J. Kornyei, which also includes the production of titanium dioxide aims, the large number of procedural steps required is disadvantageous.

The invention is based on the object that in the waste product Rctschlamm in considerable

Titanium dioxide present in abundance can be obtained more easily than before in the form of titanium tetrachloride. The titanium te trachloride can then by known methods to other titanium compounds, in particular titanium metal or titanium dioxide, further-

Ii to be processed.

The invention relates to a method for obtaining the titanium dioxide contained in the red mud as titanium tetrachloride, in which the red mud is treated at temperatures between 600 ° C and 1500 ° C pre-annealed and chlorinated with gaseous chlorine at temperatures between 500 ° C and 1000 ° C, uas method ibt characterized in that after the pre-glowing with coal in the red mud Red mud to coal ratio like 5: 1 to 1: 1 mixed and that chlorination is carried out at temperatures between 550 ° C and 650 ° C.

In a preferred embodiment of the method, the red mud is at temperatures between 800 ° C and 1000 ° C pre-annealed.

ίο New and surprising about this one The invention is that it succeeds in the joint chlorination of the mineral mixture present in red mud preferred to chlorinate the titanium dioxide, if one adheres to the provision of claims I and

Π of the examples holds - so in the test procedure described below in Example 1 SiO ₂ and Al ₂ O, less than 10%, Fe ₂ O, about 40%, TiO _2, however, more than 95% chlorinated - so that from the A sufficiently pure titanium tetrachloride can easily be obtained from the resulting chloride mixture.

What is new and surprising is that this' preferred chlorination of titanium dioxide a temperature of 550 ° C to 650 ° C is sufficient. the Previously known processes chlorinate at temperatures above 600 ° C, preferably at 850 ° C up to 1000 ° C. In contrast to the prevailing opinion in the professional world about chlorination necessary temperature has been shown that for a success of the process described here, the temperature of 600 ° C must not be significantly exceeded, because then in addition to the titanium dioxide also the other constituents of the red mud are more heavily chlorinated.

It is also surprising that it is necessary for the success of the process to use the red mud at temperatures between 600 ° C and 1500 ° C, preferably between 800 ° C and 1000 ° C pre-glow. On the other hand, it is surprisingly not necessary to add the red mud before the Mix the preheat with the coal.

In particular, there is the finding that after the Titanium from red mud working procedure disclosed in claim 1 and in Examples 1 and 2 can be chlorinated more easily than iron, contrary to the prevailing opinion that iron is present in the bean required temperature range is easier to chlorinate (cf. for example J.Barksdale, Titanium [see above], P. 428).

yy i f

This surprising finding can possibly be explained by the fact that

- the titanium compounds of the bauxite partially dissolve during the alkaline digestion and deposit again in the form of amorphous titanium oxides and oxide hydrates [cf. Z. anorg. general chemistry: I .: 390 (1972), p. 97; II .: 396 (1973), p. 303; III .: 408 (1974), p. 21] and that such in part pre-digested titanium compounds are more reactive than those originally in bauxite present titanium minerals;

- In the case of alkaline digestion, the silicates contained in the bauxite combine with sodium and aluminum to sodium alumosbicates, mainly of the cubic sodalite type, which turn out to be chlorinating fairly stable compounds is more difficult than the pure oxides;

- During the preheating phase changes occur in the mincral stock of the red mud.

The advantages that can be achieved with the invention are that in the cheap and in larger Quantities of available waste product red mud due to titanium dioxide present in significant quantities Extraction of titanium tetrachloride, which in turn is used as the starting material! for other titanium compounds serves, is made usable, and that higher-quality titanium ores are not available domestically can be replaced. In particular, the technical progress is that compared to the State of the art fewer by-products are obtained.

In one possible embodiment, the method according to the invention should be based on the figures and are explained in the following examples.

In the figure, 2, 3, 4 mean that through sieves or other suitable devices into the three compartments 2, 3 and 4 divided reaction tube, in which 3 forms the actual reaction space, 1 a feed for chlorine gas 5, 6, 7 three separately controllable ovens for the three compartments 2, 3, 4 of the reaction tube, 8 the exit for the reaction products, 9, 10 and 11 three templates, of which the middle 10 can be cooled is, 12, 13, 14 three thermometers.

25 51 380 4th 12% JeBe- Loss on ignition 1% rest

19% example 1 25% 33 kg Rofschlamm from Boke-Bauxit der Zusam 31% composition 6% TiO ₂ 5% AI ₂ O, 1 % Fe ₂ O, SiO ₂ Na ₂ O CaO

are pre-annealed for 1 hour at 900 ° C and then ■ ßend mixed with 15 kg of petroleum coke. The mixture is in the middle compartment 3 of the reaction tube filled and heated to 600 ° C. with the aid of the furnace 6. The ovens 5 and 7 are heated to 400 ° C to allow deposition of iron trichloride in the reaction tube

in prevent. Once these temperatures are reached, passed through the feed 1 within 4 hours a total of 65 kg of chlorine gas over the mixture. The less volatile chlorides, in particular iron trichloride, preferentially separate in the process

ι> Template 9, the more volatile, especially that Titanium tetrachloride, in the ice-cold template 10. Small amounts of titanium tetrachloride, which already reflected in the template 9, know by careful distillation in the template 10 transferred

■ 20 practice. Template 11 serves as a safety template.

For cleaning, the crude Tiixntetrachlorid in

in a manner known per se, decanted off from the bulk of the solids, filtered, to remove Chlorine residues shaken with mercury and fractionated distilled.

13 kg of 98 percent titanium tetrachloride are formed, corresponding to a yield of 85%; the The main impurity is silicon tetrachloride. The product consists of:

TiCl ₄
SiCl ₄
AlCI,
FeCI,

98.1%

1.6%

0.11%

0.04%

Example 2

The procedure is as in Example 1. However, it is different Example 1 used 15 kg of petroleum coke, 35 kg of chlorine gas and 30 kg of red mud from Weipa bauxite the composition

TiO,

Al ₂ O ₃

Fe ₂ O ₁

SiO.

Na ₂ O

CaO

Loss on ignition

8th%
32%
20%
17%
12%

0%
11%.

Ice forms 4.2 kg of 95 percent titanium tetrachloride, corresponding to a yield of 70%. The product consists of:

55

TiCl ₄
SiCl,

a: ci,

FeCi,

95.1%
3.3%
1.3%
0.1%.

1 sheet of drawings

Claims (3)

Patent claims: 1. Process for the extraction of the titanium dioxide contained in red foam as titanium tetrachloride, in which the red mud is kept at temperatures between 600 ° C and 1500 ° C preheated and chlorinated with gaseous chlorine at temperatures between 500 ° C and 1000 ° C, characterized in that the red mud after incineration with coal in proportion Red mud mixed into charcoal like 5: 1 to 1: 1 and that chlorination is carried out at temperatures between 550 ° C and 650 ° C. 2. The method according to claim 1, characterized in that one red mud and coal mixed in a ratio of 3: 1 to 3: 2. 3. The method according to claim 1 and 2, characterized in that there is petroleum coke as coal begins.