RU2165993C2 - Charge for recovery of noble metals by melting - Google Patents

Abstract

FIELD: metallurgy of noble metals, more particularly production of platinum group metals, gold and silver. SUBSTANCE: charge comprises, wt.%: calcium oxide or calcium oxide-based industrial products, 4-15; circulating silicate slag resulting from production of platinum group metals, 30-60; or water-insoluble residues, the balance. Charge makes it possible to reduce removal of dust during melting operation, to produce desired fragile alloy and to obtain low-viscous and low-melting slags. EFFECT: improved quality of the charge. 2 ex, 3 tbl

Description

 The invention relates to the metallurgy of noble metals (BM) and can be used in the production of platinum group metals (PGM), gold and silver.

 In the production of precious metals, various non-target products and wastes are generated containing PGM, silver, gold, in particular, such as dust collectors or water-insoluble residues of dust collectors (i.e., dust collectors), as well as recycled and conventional waste slag.

 A characteristic feature of dust shelters or n.o. Dust collectors is that their base is represented by a large number of different base elements and their compounds, mainly volatile (selenium, lead, bismuth, etc.), silver chloride, as well as carbon black, silica and other refractory oxides.

 The basis of PGM slags is made up of silicates of sodium, calcium, iron, magnesium and other base metals. Recycled slags contain quite a lot of kings of target alloys of pyrometallurgical enrichment tangled at the base of slag, consisting of PGM, gold, silver, as well as copper, tellurium, selenium, antimony, bismuth, etc.

 Recycled slag is usually subjected to depletion remelting, while receiving depleted conventional waste slag. For carrying out depletion remelting of recycled slag, various compositions of the blends are known that give satisfactory indicators for the recovery of precious metals. Recycling of dust shelters or n.o. Dust collection presents significantly greater difficulties.

 In the generally available literature, the compositions of the blends for the extraction of BM from dust sublimates by melting are not described. It is indicated, for example, only that waste can be recycled by the pyrometallurgical method — by melting a mixture containing soda, borax, glass and, in some cases, coal as fluxes, and copper is used as a collector of precious metals [Fundamentals of Metallurgy. T. 5. - M .: Metallurgy, 1968, p. 316].

To extract precious metals from various insoluble residues formed in hydrometallurgical processes of refining plants, a mixture for melting the following composition is known [Sidorenko Yu.A., Efimov V.N. - Non-ferrous metals, 1996, N 5, p. 75],%:
- calcium oxide - 10-13;
- silicate glass - 17-20;
- insoluble residues (n.o.) - the rest.

 This charge is closest to the claimed and adopted as a prototype.

The disadvantages of the prototype charge when using it for melting dust sublimates or acting dust bursts include;
- large dust removal during melting;
- obtaining during the smelting process a malleable (plastic) target alloy, which cannot be crushed to the powder state necessary for its hydrometallurgical processing;
- not obtained when melting low-viscosity and low-melting slag, which leads to increased residual noble metals in the slag.

 The technical result of this invention is to remedy these disadvantages.

This result is achieved by the fact that the proposed mixture for the extraction of precious metals by melting, containing intermediate products and waste products of precious metals and a material containing calcium oxide, according to the invention, as industrial products and waste products, it contains dust bins or water-insoluble residues of dust bins containing precious metals and circulating silicate slags for the production of platinum group metals, as a material containing calcium oxide, calcium oxide or intermediate products based on calcium hydroxide, in the following ratio,%:
Calcium oxide or intermediate products based on calcium oxide - 5-15
Recycled silicate slag for the production of platinum group metals - 30-60
Dust exhalations or water-insoluble residues of dust excursions - Else

 The silicate base of the reverse slag promotes the pelletization of wet dust during drying of the charge and is involved in the process of silver recovery from AgCl. Kings melted from slag not only have high brittleness themselves, but are also able to give brittleness to an additional amount of silver-lead-based alloys attached to them.

The content of recycled silicate slag in the charge of less than 30% is not enough to ensure the required melting temperature (not higher than 1300 ^o C), regardless of the type of industrial products and (or) waste used.

 In addition, this often does not achieve the effect of embrittlement of the target alloy.

 The content of recycled slag in the charge, equal to 30%, provides satisfactory indicators for the extraction of BM from almost all varieties of dust or n.o. dust fires. An increase in the content of recycled slag in the charge from 30 to 60% contributes to a continuous improvement in the quantitative indicators of BM extraction using any of the types of industrial products and (or) waste used in the practice of producing BM.

 An increase in the content of the additive of recycled slag in the charge of more than 60% is impractical, since it does not lead to a further improvement in the recovery of BM during smelting, while reducing the useful melt n.o. dust.

 The reduction reaction of silver chloride by the components of the slag is accompanied by a decrease in the content of sodium oxide in the slag. In order to maintain the optimal properties (viscosity and fusibility) of the slag melt during the metallization of silver chloride, an additive of calcium oxide or the addition of some material based on it is introduced into the charge.

 A decrease in the content of calcium oxide in the charge of less than 5% is undesirable, as it can lead to an incomplete reaction of the reduction of silver chloride. An increase in the content of calcium oxide of more than 15% is also impractical, since it leads to the formation of unnecessarily basic slags during smelting.

Examples of using
Example 1. To prepare the mixture took 29.0 g N.O. dust of electrostatic precipitators (by dry weight), 29.0 g of crushed refined silicate slag of refining production and 6.5 g of calcium oxide (lime). All components of the mixture were mixed, the mixture was loaded into an alundum crucible and placed in a laboratory electric furnace. After a 45-minute isothermal exposure at a temperature of 130 ^o C, the crucible with melting products was removed from the furnace. After cooling, the smelting products were removed from the crucible, divided according to the natural phase boundaries. In this case, it was obtained: 35.0 g of slag, 5.8 g of metallized heavy alloy and 4.3 g of chalcogenide matte-like alloy. According to the results of spectral analysis, the slag did not contain PGM, gold, and silver. Target melting products — metallized heavy alloy and matte-like chalcogenide (so-called “light”) alloy — were brittle enough for mechanical grinding; they were ground on a laboratory vibration mill to a particle size of minus 0.315 mm and analyzed for the content of PGM, gold and silver (Table 1 )

 PGM and gold from the crushed target melting products of the proposed charge can be further easily converted to a chloride solution by known methods, including using the most progressive method of chlorination in a solution of hydrochloric acid (see I.N. Maslenitsky, L.V. Chugaev , V.F. Borbat et al. Metallurgy of precious metals, Vol. 2, edited by L.V. Chugaev. - M.: Metallurgy, 1987, p. 416).

 Example 2. For the preparation of the charge took 592 kg of wet (W = 45%) n.a. dust explosions of electrostatic precipitators produced by PGM, 324 kg of recycled granular slag (W = 5%) produced by PGM and 138 kg of wet (W = 50%) cakes based on calcium oxide.

 All initial wet components of the charge were divided into six equal portions and loaded in layers into 6 boats, 175-176 kg each (see table. 2).

In total, 6 charge boats were prepared, which were simultaneously loaded into a drying hearth furnace. The drying parameters of the mixture: temperature - 300 ^o C, time - 9 hours.

 After drying, a mixture of all the components of the charge from 6 boats was poured into the loading hopper. Then, the charge from the hopper was loaded for melting in a rotary-type reflective fuel furnace.

The furnace was turned on for heating and the mixture was melted. The temperature of the melt in the furnace before draining the melting products was determined using an infra-beam pyrometer and was 1200-1250 ^o C.

 Smelting products were drained from the furnace into cast-iron ladles-molds. After cooling, 428 kg of slag and 96.2 kg of the target noble metal alloy were recovered from the ladles.

 The target alloy of precious metals was sufficiently brittle and was ground in a ball mill to a particle size of minus 1 mm. Smelting products were tested and analyzed for the content of PGM, gold and silver. The target alloy was tested after grinding, the slag was tested by sampling during discharge from the fiery-liquid state.

 The content of noble metals in the obtained melting products are presented in table. 3.

 The crushed target alloy was further subjected to dissolution and processing using known methods.

Claims (1)

The mixture for the extraction of precious metals by melting, containing industrial products and waste products of precious metals and a material containing calcium oxide, characterized in that as industrial products and waste products it contains dust bins or water-insoluble residues of dust bins containing precious metals, and recycled silicate slags for the production of platinum metals groups, as a material containing calcium oxide, calcium oxide or intermediate products based on calcium oxide in the following ratio of components ntov,%:
Calcium oxide or intermediate products based on calcium oxide - 5 - 15
Recycled silicate slag for the production of platinum group metals - 30 - 60
Dust collectors or water-insoluble residues of dust collectors - Other

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