DE580541C - Process for the extraction of chromium - Google Patents

Description

Process for the extraction of chromium It is known that chromium compounds, like chromium oxides or chromium chlorides, at elevated temperature with hydrogen in chromium can be transferred. However, this process has been used in technical applications up to now not found because of considerable technical difficulties in carrying it out result. So z. B. when using the technically easily accessible chromium (3) chloride the drawback asserts that in the course of the reduction chromium (?,) chloride is an intermediate product forms that melts at about goo ° and at the temperatures required for reduction of over iooo ° volatilized. The formation of the fusible intermediate causes the reaction material to stick together, causing the hydrogen to act is made so difficult that the reaction in technically appropriate times cannot be completed. The evaporated chromium chloride also settles partly on the walls of the reaction chambers, which are mostly made of ceramic material solid and causes a destruction of the mass here with partial reduction. To the Part of the evaporated chromium chloride is also carried on unchanged by the reducing gas and settles on the cold parts of the apparatus. Below the melting point of the chromium (z) chloride, however, the reaction does not proceed with sufficient speed.

It has now been found that the reduction of reducible chromium halides with hydrogen can be carried out much more easily if you have them in the presence of metals. Metal alloys or such compounds of metals that are easily are reducible, or mixtures of these substances. Intimate ones are appropriate Mixtures of the finely divided substances of the type mentioned with those to be reduced Chromium halides used. As additives can, for. B. are used nickel, Copper, ferrochrome, also easily reducible compounds such as copper chloride, Nickel oxide, cobalt carbonate. Mixtures of such compounds can also be used and with metal powders. Has proven to be particularly advantageous an addition of chromium powder proved. Namely while z. B. at rooo ° without the addition of chromium only about half of the applied chromium chloride can be converted into chromium, after adding chrome powder when working under otherwise identical conditions over 98 ° (o of the chloride converted into chromium. A similar effect is achieved by the additive obtained from iron powder. Mixtures of chromium chloride and iron chloride, how they z. B. obtained in the chlorinating digestion of chrome iron stone, can be used to advantage. The iron chloride is here already at a relatively low level Temperature reduced to iron.

The reduction of the chromium halides is expedient at temperatures executed from 90o to 13c0 °. The reaction products «earth in the form of powder or obtained as a coherent spongy sinter cake, which made up without difficulty must be removed from the reduction chamber. If you use technical, carbon-containing chromium chloride, so takes place when working according to the present method decarburization takes place at the same time. The carbon content goes down to less than 11, the original salary back. The latter can be of particular advantage Trap used as an additive iron oxide, with the carbon content z. B. from 1.5% to about 0.1 ° 1o can be reduced.

In order to achieve pure products, it is advisable to use pure hydrogen to work. In particular, it is necessary in this case to remove the hydrogen from Oxygen, water vapor and other oxygen-containing contaminants carefully to free.

The chromium obtainable by the present process can, in contrast to that produced by the aluminothermic route, both by itself and as a mixture with the added metals easily processed on fine-grained powder and in this Form for certain ineta: llurgical procedures can be used with particular advantage.

Example 1 In an electrically heated oven with ceramic Material (e.g. Pythagoras mass) is lined, an intimate mixture of 1o kg of chromium (3) chloride purified by sublimation with 6 kg of chromium powder hydrogen carefully stripped of oxygen and water vapor at a flow rate of 15 cbm per hour initially treated for 2 hours at 50 ° to 700 °, whereupon the temperature is increased to 120o °. After 8 hours of treatment at 120o ° the mixture turns into a cohesive, porous and metallic shining mass converted. The chromium chloride is practically completely reduced to chromium. That The product, which is usually obtained as a sinter cake, can be turned into a fine dust without difficulty Powders of any fineness can be crushed. The chromium obtained is practical completely pure. Part of the product obtained can be used for the next operation can be used as additional material.

Example 2 An intimate mixture consisting of 10 kg of technical chromium (3) chloride (with 42 ° 10 carbon, based on the chromium content) and 3 kg of finely powdered iron is mixed with purified hydrogen at a flow rate of 15 cbm per hour for 2 hours Treated at 50o to 700 °, whereupon the temperature is increased to z2oo °. After 8 hours of treatment at 1200 °, the mixture has been transformed into a coherent, porous and metallically shiny mass of the following composition: 50.2 % chromium, 48.0 ° J0 iron, 1.4% carbon.

In a similar way: a mixture of 5 kg of carbon-free, through Sublimation of purified chromium (3) chloride and 2.5 kg of carbon-free iron powder with hydrogen freed from oxygen and water vapor at a flow rate of 8. cbm per hour, initially for 2 hours at 50 ° and then for 12 hours be treated at iooo °. A carbon-free product of the following is formed Composition: 57.4% iron, 42.17% chromium.

98.8% of the chromium chloride used is thus converted. Under the same conditions, but without the addition of iron, only 60 ° 10 chromium chloride is converted.

The poorly sintered products can be easily pulverized.

Example 3 An intimate mixture of 5 kg of chromium (3) chloride (with about q. % Carbon, based on the chromium content) and 1.5 kg of iron oxide is first treated with high-purity hydrogen at 50 ° to 60 ° for about 11/2 hours treated at a flow rate of 7.5 cbm per hour. In this case, the chromium (3) chloride is first reduced to chromium (2) chloride, whereby the exposed carbon is converted into volatile compounds while loosening the mass. With careful, not too rapid heating, the formation of chromium oxide, the reduction of which is more difficult than that of chloride, can easily be avoided. The temperature is then gradually increased to 120 ° for the purpose of complete reduction. After 8 hours of treatment at 1200 °, 88% of the amount of chromium (3) chloride used is reduced to chromium, and the carbon content, converted to the metallic components, is only 0.18

Claims (1)

PATENT CLAIM: Process for the production of chromium by reduction of chromium halides, possibly including those that contain carbon Hydrogen at elevated temperature, characterized in that the reduction after Addition of finely divided metals that do not melt at the reduction temperatures, Metal alloys or such metal compounds under the working conditions are easily reducible, advantageously with e = purified hydrogen.