DE567270C - Manufacture of beryllium fluoride - Google Patents

Description

Preparation of beryllium fluoride to which the present invention relates a process for the preparation of berylline nifluoride by digestion of Bervll with Aninion fluoride in continuous operation.

From G i b s o n an, `experienced is given for the digestion of beryl in which this with ammonium fluoride is about three times the theoretically required Amount in a standing container for a long time. being the present Silicic acid evaporates as SiF, and Bervllitimfluorid together with the fluorides the accompanying metals remains. The procedure is for use in the laboratory thought and has not yet found a technical utilization; Rather, nian has Your digestion with sodium silicofluoride is preferred. This should be decisive have been. that in the case of digestion with inhalation fluoride, the predominant part of the latter is consumed for the formation of silicon tetrafluoride and aluminum chloride, which in themselves represent more usable by-products, and that too your Gibson's method requires a substantial excess of amniotic fluoride Recovery made cumbersome and difficult.

According to the present invention, beryl finite amine fluoride becomes in continuous Process open-minded, with all not bound to <las beryllium Fluorine is recovered as aminone fluoride and recycled.

The digestion of beryl according to the invention is basically the same do well with neutral and acidic ammonium fluoride. Since, however, as a result of the decomposable Ic = it of the neutral salt at temperatures above .Io 'C, the regeneration of the same is more difficult the digestion is expediently carried out with the acid salt. Here lets at the same time the property of the acid salt that it is initially when heated passes into the liquid phase, utilize in an advantageous manner.

Attempt the digestion by heating a briquetted mixture von Bervll and ammonium fluoride to be carried out in a rotary kiln. have proven that at As the heating progresses, the goods stick together, which means that they are processed extremely difficult, if not made impossible. It therefore became the way selected, the ammonium fluoride for itself in an evaporator placed in front of the rotary kiln to heat and the rotary kiln, in which the finely ground beryl is in constant motion is held. to be supplied in vapor form. By using the pre-evaporator it is possible, the evaporation of the ammonium fluoride in best adaptation to the respective in to regulate the Bervllinengen entering the rotary kiln. on the other hand favored the dusty character of the, which existed throughout the course of the reaction Reaction material in connection with the thorough whirling with the, gaseous Ammonium fluoride the course of the reaction. It is therefore sufficient to use an io- bis 20% excess fluoride over the theoretical amount and at a reaction temperature from 35o to 60o ° C a throughput time of the raw material of 1 hour to achieve a complete To achieve volatilization of the silica. The implementation proceeds according to the equation 3Be0 # A1203. 6S102 + 18NH4F. HF - 3BeF2 + - 2AIF3 -t- 6 SiF4 + i8NH3 '-, 18H20. Those arising in the reaction after the ammonia is initially split off Exhaust gases, which essentially consist of SiF4 and the excess ammonium fluoride, are now with simultaneous cooling to about 150 ° C and below with ammonia gas treated in excess, the SiF4 in the form of a solid compound, SiF, # z 1VH3, precipitates together with the excess ammonium fluoride. The eliminated Solid substances are appropriately, expediently by mechanical or electrical Dust filter, brought to the separation and in a known manner on ammonium fluoride processed. The latter is preferably done by adding it to water, treating with excess ammonia. Separation of the precipitated silica and evaporation or spraying the solution. There are 4 ;. the one used for the digestion Ammonium fluoride according to the equations 6SiF4 -f-. 12NH3 _--- 6SW4.2NH3 6 SW4 # 2NH3 -j- 1 - NH3 -f- 12H20 = 6S102 - (- 24NH4F 24NH4F - 12NH4F # HF + 12NH3 regenerated and returned to the evaporator.

The almost chemically pure silica resulting from this decomposition is an excellent raw material for the production of silica gel, water glass, etc. like

The work-up of the mixture of remaining in the digestion Beryllium fluoride, aluminum fluoride and iron oxide are carried out in a known manner Dissolve the beryllium fluoride with water and evaporate on beryllium oxyfluoride or further conversion to beryllium hydroxide or beryllium salts. @ From the essentially The dried residue consisting of aluminum fluoride and iron oxide is also used processed the aluminum fluoride on ammonium fluoride. This is expediently done by by treatment with concentrated sulfuric acid with the addition of silica in In a manner known per se, SiF4 is first freed and this with the furnace exhaust gases is combined, whereupon it finitely these together by reaction with ammonia Ammonium fluoride is worked out.

The neutral ammonium fluoride initially formed during regeneration is then converted into the acid salt in a known manner by heating, which is used for a new digestion is used, while the ammonia gas split off here for the Separation of that contained in the furnace exhaust gases and that from the decomposition of aluminum fluoride originating Si F4 is used. In this way it is possible to do the whole too to circulate the ammonia gas required in the process, only the operational ones Losses arise.

Example The overview shows the course of the Digestion and that of the cycle of the substances used in digestion are shown. The beryl, which is finely ground in the mill a, first falls into a silo b, from to which it is fed in measured quantities to the iron rotary kiln c, which is heated to about 500 ° C will. From the evaporator d is the rotary kiln gaseous acidic ammonium fluoride in about z0% excess over the amount corresponding to the beryl introduced forwarded. The movement of the goods through the rotary kiln is regulated so that after about one hour treatment the digested material in the heated to about 400 ° C Chamber e exits and separates here from the reaction gases. The latter will be passed into a second chamber f, cooled to about i 50 ', which simultaneously nor ammonia gas is fed in, so that not only that is used to react in excess applied ammonium fluoride condenses, but also the S 'F4 by addition Ammonia is precipitated in solid form. The solid components are now fed to the stirring vat g, which was also not used up during the precipitation Ammonia gas is supplied. Silica precipitates out in the filter 1a is separated from the solution. The latter is finally concentrated in the evaporator i and processed on acid ammonium fluoride, which in turn is the \ 'steamer d is supplied, while the excess and that split off from the neutral fluoride Ammonia gas is passed to the Kamtner f.

The solid residues of the digestion, consisting of Be F., A1 F3 and Fe. O, are first extracted with water in the stirring vat k and in the filter 1 in a BeF = -containing solution and a solid one made of A1F3 and Fe.O .; existing residue decomposed. The solution is Na on BeF in the evaporator. processed, while the residues at n are treated with sulfuric acid and part of the silica from the filter Ir , whereby aluminum and iron sulfate are formed with the elimination of gaseous Si F, which is combined with the furnace gases and fed to chamber f.

The yield of Bervlliumfluorid is about 90 to 95% of the theoretical :Lot.

Claims (5)

PATENT CLAIMS: i. Process for the preparation of vitreous fluoride by digestion of Bervll with ammonium fluoride, characterized in that the Auf end in continuous operation, expediently in a rotary kiln, by action of amniotic fluoride vapors, and (let (read a lump of silicon tetrafluoride by treatment with ammonia and decomposition of the resulting solid compounds recovered in the form of ammonium fluoride and used for further digestion will. 2. The method according to claim i, characterized in that also during the digestion The aluminum fluoride formed is converted into ammonium fluoride via silicon tetrafluoride will. 3. The method according to claim i and a, characterized in that acidic ammonium fluoride is used for the digestion, with the expedient in the representation of the acidic Fluoride ammonia split off by thermal decomposition of the neutral fluoride is used for the separation of solid compounds from the furnace exhaust gases. Procedure according to one of the preceding claims, characterized in that the digestion in Rotary kiln takes place, this is expediently supplied with ammonium fluoride in vapor form. 5. The method according to any one of the preceding claims, characterized in that the fixed connections separated from the furnace exhaust gases by mechanical or electrical dust filters are brought to the separation.