DE518780C - Digestion of chrome and similar ores - Google Patents

Description

Digestion of chromium and similar ores It is known when digging von Chromeisenstein provided the ore from the outset with a sufficient amount for digestion Amount of soda and 1q. to add up to 1d parts of lime to 10 parts of ore. Instead of Lime has been used successfully with dolomite, recently also in burnt form.

In order to save alkali, the ores are first digested with one insufficient amount of alkali carbonate and then the leached frit with further amounts of alkali with the addition of suitable additives, in particular lime treated. Here it has already been established that the amount of lime is opposite to that in the case of direct full digestion, relatives were significantly reduced.

According to the present invention, in the digestion with insufficient Amounts of alkali for the purpose of simplifying and making the process cheaper and type of anti-melting additives, whether you like them with the first or second digestion or add to both, modified.

This happens once in such a way that you are burned right from the start or unburnt lime alone or magnesium carbonate or magnesium oxide alone, or a mixture of these components is added to the mixture of chrome ore and alkali, but the added amount of calcium oxide should not be greater than half that Corresponds to the amount by weight of the chromium ore used. From magnesium oxide, etc. are to use the amounts equivalent to calcium oxide.

It has been found that the troublesome formation of sodium ferrite and Sodium aluminate is omitted when z. B. 2 to 3 parts burnt lime on r Part of the iron oxide present in the ore is used.

You can also distribute this addition over the two phases of the process, by z. B. in the first phase one to two thirds and in the second two up to a third of the surcharge used.

Another modification of the anti-melt additive If chromium ore is digested with insufficient amounts of alkali, this means that after the first digestion has been carried out without additives, in the case of the second digestion as a supplement, small amounts of magnesia alone or in a mixture with lime. about in the ratio as it is in dolomite, use.

The method is intended to be used particularly when the chrome ore is digested in a rotary kiln Find use. It is necessary to melt the mass itself a tough river to prevent completely or at least almost completely, what only when using of surcharges succeeds.

It has already been proposed to use lesser chrome ore Lime quantities to produce a melt, which Sodium and calcium chromate contains, and the leached mixture of the two chromates then with ammonium carbonate to decompose. With this method, too, one has, since one has the partial formation of Calcium chromate in the melt aimed for the transfer of all chromium Insufficient amounts of soda used in sodium chromate. But the amount of lime used With 90 parts burnt lime for 100 parts chrome ore, it was almost twice as large than in the present procedure.

Because according to him, according to a content of chrome ores at approximately 20 '/ "iron oxide, an average of 50 parts of quicklime, are added; it is precisely with this amount that one achieves the desired formation of a loose and therefore The frit that can be easily opened to the end, so that you can use it for the second treatment Soda does not need to be heated in the rotary kiln until it melts, and there are still no losses on chromium through the formation of calcium, which is a problem in the usual leaching process chromats has.

Example i When roasting a chrome ore, the Fe0 oxidizes to Fe., 0 "; so if an ore has 22.5% FeÖ, one has to take it with it in the heat after the digestion Calculate 25 ° / a Fez O $.

There are 100 parts of chrome ore with 50 % Cr20 $ and 22.5 % Fe0 with 35 parts soda and 50 parts quick lime of the oxidizing roasting at 700 to 100 ° C 3 to q. Subjected for hours. This creates a frit in which half of the chromium used is present in the form of water-soluble sodium chromate, which is leached out in the usual way. The residues are dried somewhat and, with the addition of a further 40 parts of soda, another 3 to q. Exposed to the oxidizing flame for hours at 700 to 100 ° C. The digestion converts g5% of the original chromium oxide into soluble chromate.

The 50 parts quicklime can be replaced by 36 parts Magnesium oxide; 25 parts burnt magnesia, 25 parts burnt lime, or withdrew parts of potassium carbonate or an equivalent mixture of the above substances.

Example e 100 parts of ore of the above composition will be mixed with 4o parts of soda and 3 to q. Roasted for hours at 700 to 100 ° C. This converts about half of the chromium oxide into soluble chromate. The 35 parts of soda and 54 parts are added to the leach residue from the first step Parts of magnesia or the equivalent substances or mixtures of substances given in Example i.

Example 3 Instead of as specified under example i, except at the beginning Adding 5o parts of lime to soda, you only use 2o to 3o parts of lime, glowing, leaching the chromate with water and mixed the resulting residue except with soda with the remaining 2o to 3o parts of lime. Instead of lime, de can be used in example i specified equivalent substances are used.

Claims (1)

PATENT ANJSPRUCH Production of alkaline earth free alkali chromate by alkaline digestion of chrome ores in several stages using burnt or unburnt lime or magnesium oxide as aggregates, characterized in that that the sum of the surcharges to be distributed to the individual levels if necessary to two to three times the weight of the iron present in the ore (i.e. less than half the weight of the ore) remains limited.