RU2309122C2 - Method of processing beryllium-containing concentrates - Google Patents

Abstract

FIELD: mining industry and inorganic synthesis.

SUBSTANCE: invention is intended for use in processing of beryllium-containing ore concentrates into beryllium hydroxide. To that end, initial bertrandite-phenacite-fluorite concentrate is activated by adding to it fluorine-containing compounds in such amount as to provide level of fluorine in resulting emulsion 8 to 21%, after which reaction mixture is sulfatized with 93% sulfuric acid at 250-320°C for at least 0.5 h. Sulfatized product is then leached to form crude beryllium hydroxide, which is dissolved in alkali and diluted to provoke hydrolysis resulting in technical-grade beryllium hydroxide.

EFFECT: increased recovery of beryllium into technical-grade beryllium hydroxide, reduced production waste, and diminished number of steps.

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Description

The invention relates to the metallurgy of beryllium, in particular to the processing of beryllium-containing ore concentrates to beryllium hydroxide.

There is a sulfate method for extracting beryllium from a beryl concentrate, in which the chemical activity of a beryl concentrate is increased by melting the concentrate at high temperature without adding fluxes, granulating the melt in water and subsequent heat treatment of the granulate [1-5].

The obtained melt granulate is treated with sulfuric acid and leached with water. As a result of this operation, a solution of beryllium sulfates, aluminum and various impurities contained in the beryl concentrate is obtained, and an insoluble residue of filtered silica.

Melting of beryl concentrate and heat treatment of its granulate does not require additional consumption of chemicals. This method of opening the concentrate is based solely on crystallographic changes in the molecular structure of beryl resulting from its melting at 1650 ° C and rapid cooling of the melt at a rate of more than 750 ° C / s [2]. Moreover, due to the high cooling rate, the structure of the liquid melt is fixed in the granulate, i.e. glass structure. Such material is practically unbreakable by sulfuric acid. However, in the process of subsequent heat treatment (thermal activation) of the melt granulate at 950 ° С, its structure is transformed in such a way that beryllium is released in solid solution in the form of modified phenakite microcrystals, which are quite soluble in sulfuric acid.

The usual practical yield of beryllium from a concentrate into a sulfate solution using this technology is, on average, about 91% wt. [3]

In the case when the condition for the cooling rate of the melt (cooling rate less than 750 ° C / s) is not met in the granulation operation, beryllium is released in solid solution in the form of crystallized beryllium oxide, which, in the future, is practically not opened by sulfuric acid. In practice, due to the limited thermal conductivity of the melt, this phenomenon occurs if the size of the drops of melt falling into the water exceeds 0.5 inches [2]. Therefore, the melt granules with sizes exceeding 13 mm are screened out and sent for re-melting.

Significant disadvantages of flux-free technology are [2, 3]:

- low extraction of beryllium in the sulfate solution and, accordingly, high losses of beryllium with waste;

- high energy consumption, since the processes of melting, heat treatment of the granulate and its sulfation occur at high temperatures - 1650 ° C, 950 ° C, 300 ° C, respectively;

- the need for turnover for re-smelting of granulate with a particle size of more than 13 mm in an amount of up to 15% of its total mass.

Closest to the claimed invention in terms of similar features is a method for the joint processing of bertrandite-phenakite-fluorite and beryllium concentrates with a beryllium content of 3.6-4.3% by weight. and 1.7-2.1%, respectively, based on the melting of a mixture of these concentrates with soda [6]. According to this method, the chemical activity of the concentrates is achieved in that the concentrates are mixed to obtain a mass ratio of SiO ₂ : CaO in their mixture of 1.4, sodium carbonate is added to the mixture of concentrates to obtain a mass ratio of SiO ₂ : (CaO + Na ₂ O) in charge equal to 1.1 ÷ 1.3. The prepared mixture is melted, the melt is granulated in water, the granulate is wet milled to a particle size of less than 150 microns, the resulting water-granulate pulp is concentrated and it is sulfated with sulfuric acid at 120 ° C. Next, beryllium sulfate is leached from the sulfate mass with water, crude beryllium hydroxide is precipitated from the sulfate solution, alkaline dissolution of the crude beryllium hydroxide, dilution of the resulting solution with water, resulting in the hydrolysis of sodium beryllate and precipitation of technical beryllium hydroxide.

The described method for the joint processing of beryllium concentrates provides the extraction of beryllium from granulate into a sulfate solution at 97 ÷ 99% wt.

The specified method for the joint processing of bertrandite-phenakite-fluorite and beryl concentrates is not without drawbacks, because:

- does not provide 100% by weight processing of beryllium-rich bertrandite-phenakite-fluorite concentrate, because this silicon concentrate lacks the silicon required by this technology to form acid-opening phases with beryllium. Silicon deficiency is covered by the addition of silicon-rich beryl concentrate, which accounts for at least 20% wt .;

- does not provide for the disposal of a valuable component of bertrandite-phenakite-fluorite concentrate - fluorine. Using this method, almost all the fluorine contained in the initial charge is extracted together with beryllium in a sulfate solution, which leads to a fluorine-rich solution of beryllium sulfate and further reduces the completeness of precipitation of beryllium from this solution in the form of beryllium hydroxide;

- according to this method, a large amount of dump cake is formed;

- the implementation of the method requires 5 expensive technological operations at the stage of its preparation for sulfuric acid opening (blending of bertrandite-phenakite-fluorite concentrate with beryllium concentrate and soda ash in a predetermined ratio, smelting the mixture, granulating the melt, grinding the granulate, preparing the water pulp of the crushed granules with a given ratio T: G).

The problem to which the claimed invention is directed, is to develop a method for processing bertrandite-phenakite-fluorite concentrate, providing not only high extraction of beryllium into water-soluble sulfate, but, most importantly, high extraction of beryllium into finished products - technical hydroxide, utilization of silicon contained in the concentrate and fluorine in the form of hydrofluoric acid (KFVK) and reducing the number of process operations and production wastes.

The essence of the proposed method for processing beryllium-containing concentrates is that, in contrast to the known method, which includes the stage of activation of the concentrate, sulfatization of the activated concentrate with sulfuric acid, water leaching of a sulfated product, precipitation of beryllium crude hydroxide from an sulfate solution, alkaline dissolution of beryllium hydroxide and dilution, dilution sodium beryllate to technical beryllium hydroxide, according to the proposed method, the original bertrandite α-phenakite-fluorite concentrate is activated by adding fluorine-containing compounds (in the form, for example, CaF ₂ , HF, etc.) in such an amount that the fluorine content in this mixture is from 8 to 21% wt., after which the resulting reaction mass subjected to sulfatization with 93% sulfuric acid at a temperature of 250 ÷ 320 ° C for at least 0.5 hours

The task is achieved by the fact that in the process of opening the bertrandite-phenakite-fluorite concentrate with 93% sulfuric acid in the presence of activating additives, fluorine compounds in the process of heating the reaction mass already at a temperature of 100 ÷ 200 ° C interact with the acid with the formation of gaseous hydrogen fluoride. In this case, first of all, the interaction of gaseous hydrogen fluoride with beryllium silicates, with the formation of gaseous silicon fluoride, is accompanied by the destruction of the crystal lattice of beryllium minerals, and thereby increases their chemical activity, which further provides the possibility of deep opening of the concentrate activated in this way 93% sulfuric acid at a temperature of 250 ÷ 320 ° C, with the formation of water-soluble beryllium sulfate - BeSO ₄ · 2H2O.

It was found that at a temperature of less than 250 ° C, apparently, due to the strong temperature dependence of the reaction of the interaction of gaseous hydrogen fluoride with beryllium silicates, the degree of opening of the concentrate sharply decreases, and the extraction of beryllium drops from more than 99% to, for example, 91% at a temperature of 235 ° C. At a temperature of 320 ° C, dehydration of the readily soluble bivalium sulphate of beryllium - BeSO ₄ · 2H ₂ O, formed during the sulfation process, to more difficultly soluble BeSO ₄ takes place. Therefore, when the specified temperature of sulfatization of the concentrate is exceeded, the extraction of beryllium in the sulfate solution in the process of water leaching decreases by 3-6%.

Bertrandite-phenakite-fluorite concentrate contains from 5 to 12% fluorine, which is involved in the activation of the opening process according to the described scheme. However, as a rule, the amount of fluorine contained in the concentrate is not sufficient to achieve an industrially acceptable recovery of beryllium from the concentrate.

Gaseous silicon fluoride is removed from the reaction zone and disposed of in a separate apparatus in the form of hydrofluoric acid. Due to the defluorination of the concentrate during its opening with sulfuric acid, the leaching operation provides a solution of beryllium sulfate with a low fluorine content, which further improves the completeness of the deposition of beryllium from a sulfate solution into beryllium hydroxide.

The number of process steps, energy and reagent costs during the implementation of the method are reduced, because there are no operations of the smelting of the concentrate with soda and the production of water-granulate pulp of granulate melt. The amount of production waste in the form of mother liquors and waste cakes is also reduced due to the higher beryllium content in the feedstock compared to the prototype.

Implementation example

To implement the method, weighed samples of bertrandite-phenakite-fluorite concentrate weighing 100 g are mixed with 14 g and 10 g of fluorite-CaF ₂ (examples No. 5 and No. 3, respectively) and with 12.6 ml and 5.4 ml of 40% hydrofluoric acid (examples No. 2 and No. 4, respectively). In Example No. 1, an activating additive was not used. The resulting mixture was treated with 93% sulfuric acid at the rate of 0.8 ml of acid per 1 gram of concentrate. The resulting reaction mass sulfates, keeping the mixture for at least 30 minutes at a temperature of 250 ÷ 320 ° C. In this case, the resulting gaseous silicon fluoride is absorbed in a separate apparatus with hydrofluoric acid to obtain CPVC. The sulfated product is leached with water at T: W = 1: 5 (in the initial concentrate), at a temperature of 90 ÷ 100 ° C for 20 minutes. Sulfuric acid pulp from the leaching operation is neutralized with an ammonia solution to a pH of ~ 3.5 and filtered. The cake obtained after filtration is subjected to double filter-repulpative washing from beryllium sulfate at Т: W = 1: 7 (in the initial concentrate) and a temperature of 90 ÷ 100 ° С for 15 min. The residual beryllium content in the cake determines the completeness of beryllium extraction. Beryllium crude hydroxide is precipitated from the filtrate (sulfate solution) with an ammonia solution and the completeness of the deposition of beryllium into rough hydroxide is determined, from which, after dissolution in alkali and hydrolysis of sodium beryllate, the final processing product is obtained - technical beryllium hydroxide.

For comparison with the claimed invention receive sulfated product by the prototype method. For this purpose, a mixture of bertrandite-phenakite-fluorite and beryl concentrates is prepared, the amount of each of which is determined from the calculation of the required mass ratio in the mixture of silicon and calcium concentrates contained in the composition in terms of SiO ₂ : CaO oxides of 1.4. Sodium carbonate is added to the prepared concentrate mixture based on the calculation of the mass ratio in the mixture between silicon, calcium and sodium in terms of SiO ₂ : (CaO + Na ₂ O) oxides equal to 1.1–1.3.

Then the resulting mixture is loaded into a graphite crucible and melted at a temperature of ~ 1360 ° C. The melt is poured into cold water, the obtained granules are crushed. The crushed melt is pulp in water at a ratio of T: W = 1: 1. To the resulting pulp was added 93% sulfuric acid at the rate of 0.8 ml of acid per 1 gram of granulate, the resulting reaction mass was incubated for 5 min at a temperature of 120 ° C. The processing of the thus obtained sulfated product is carried out similarly to the processing of the sulfated product according to the claimed invention.

Table 1 shows the characteristics of the concentrates used in the work, and in table 2 the results of the implementation of the method according to the claimed invention and, for comparison, the prototype method.

Table 1
chemical composition of beryllium concentrates Name of concentrate The content of components,% wt. Be SiO ₂ Cao F Bertrandite-phenakite-fluorite 3.6-4.3 15-27 12-30 5-14 Beryl 1.8-2.1 53-57 1-2 1-2

From the data given in table 2, it follows that when implementing the method according to the claimed invention (examples No. 2-4), the extraction of fluorine in the gas phase is from 94 to 96% wt., The extraction of beryllium from the concentrate in the sulfate solution from 94.5 up to 98.1% wt., the completeness of deposition of beryllium in rough hydroxide from 99.4 to 97.3% wt., and through extraction of beryllium in technical hydroxide from 94.4 to 98.4% wt. All of these indicators are not inferior to the parameters of the prototype method. Additionally, in the implementation of the proposed method obtained hydrofluoric acid in an amount of from 10 to 23% by weight of the concentrate.

With a decrease in the fluorine content in the reaction mass of less than 8% wt. (Example No. 1), the extraction of beryllium from the concentrate drops sharply and thus its losses increase. The increase in fluorine content in the reaction mass above 21% wt. impractical since this does not increase the completeness of opening the concentrate, and, on the other hand, can lead to rapid corrosion of equipment.

Thus, when processing bertrandite-phenakite-fluorite concentrate, the claimed method, compared with the prototype method, allows more efficient extraction of beryllium into a sulfate solution and hydroxide and provides the removal of fluorine from granulate with the possibility of utilizing the latter in the form of a valuable commercial product - hydrofluoric acid. In addition, the technical results achieved in the claimed method are provided in comparison with the prototype method using a shorter flow chart, reducing energy costs by 40 ÷ 50%, reducing the mass of feedstock and reagents by 5 ÷ 18% and reducing the volume of waste water and mass dump cakes 7 ÷ 24%.

Information sources

1. Stefanyuk S.L. Metallurgy of magnesium and other light metals. - M.: Metallurgy, 1985.

2. Everest D. Chemistry of beryllium. - M.: Chemistry, 1968.

3. White D., Burke J. Beryllium. - M.: IL, 1960.

4. Beryllium. Science and technology. / Edited by Webster D., London G.J. et al. Per. from English under the editorship of Tikhinsky G.F., Papirova I.I. - M.: Metallurgy, 1984.

5. Silina G.F., Zarembo Yu.I., Bertina L.E. Beryllium. Chemical technology and metallurgy. - M .: Atomizdat, 1960.

6. Zhurkova Z.A., Matyasova V.E., Matyasov N.G., Samoilov V.I. A method of extracting beryllium from beryllium flotation concentrates. A.S. 2107742.1996.

Claims (1)

A method of processing beryllium-containing concentrates, which includes the stage of activation of the concentrate, sulfatization of the activated concentrate with sulfuric acid, water leaching of the sulfated product, precipitation of beryllium crude hydroxide from a sulfate solution, alkaline dissolution of beryllium crude hydroxide, dilution and hydrolysis of sodium beryllium to give technical hydroxide, bertrandite-phenakite-fluorite concentrate is activated by adding a fluorine-containing compound to it in such an amount that the fluorine content in the specified mixture ranged from 8 to 21 wt.%, after which the resulting reaction mass was subjected to sulfatization with 93% sulfuric acid at a temperature of 250-320 ° C for at least 0.5 hours