RU2376395C1 - Method of processing of dust from refining production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used for reprocessing of wastes from refining production, particularly for reprocessing of dust-fumes or non-water-soluble residues of dust-fumes which are concentrates of dust from refining production. Method of reprocessing of dust concentrate from refining production includes leaching in solution of caustic soda, separation of not-solved residue from alkaline solution, melting of not-solved residue with admixtures and grinding. After melting and grinding it is implemented reprocessing of received at melting of bottom heavy alloy as concentrate of refining production. Before leaching in solution of caustic soda initial product is depulping in water. Received pulp is acidified by addition of acid up to achievement of pH=1-2 and subject to grouting treatment by addition of iron powder.

EFFECT: reduction of amount of noble metals, transferring into alkaline solution at leaching stage of DFRP in caustic soda, increasing of direct extraction of noble metals.

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Description

The invention relates to the metallurgy of noble metals (BM) and can be used in the technology of refining metals of the platinum group (PGM).

Various inappropriate products and wastes inevitably arise at refineries, containing PGM, silver, gold, in particular, such as dust collectors and water-insoluble residues of dust extracts, obtained by cleaning the dust and gas tunnel and electrostatic precipitators (the so-called dust concentrate of refining production).

A characteristic feature of both pulverized dusts and refining dust concentrate (CAP) is that their base is represented by a large number of different chemical elements and their compounds, mainly volatile non-precious metal chalcogenides, ammonium and silver chlorides, lead, and soot carbon. This intermediate product contains from 0.5 to 3% PGM (in total), from 0.05 to 0.3% gold, from 3 to 15% silver, from 10 to 25% lead, from 4 to 8% selenium, from 4 up to 10% tellurium, from 2 to 4% arsenic. The processing of dust shelters or KAPA presents significant difficulties and is associated with large material and labor costs.

From generally available literature it is known that the processing of dust can be carried out 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].

The disadvantages of this analogue method when it is used for processing dust concentrate of refining production (CAPA), which contains, along with BM, significant amounts of base metals chalcogenides, should be attributed:

- the formation during smelting of large quantities of secondary dust combustors enriched with volatile chalcogenides, containing BM and in need of processing;

- the transition of chalcogenides during smelting to the target BM alloys, which increases their mass, reagent consumption and labor for refining.

A known method of processing products containing chalcogenides of base metals, lead, platinum group metals, gold and silver, designed specifically for the processing of dust concentrate refining production.

According to this method, the dust concentrate of refining production is leached in a solution of caustic soda, the insoluble residue is separated from the alkaline solution and the insoluble residue is melted by adding fluxes and refining intermediate products to obtain a bottom heavy alloy, the bottom heavy alloy is crushed and processed as a concentrate of refining production. [RF patent No. 2291212, Efimov V.N., Temerov S.L., Moskalev A.V., Churkin V.A., Gubin M.V. - BI No. 1, 2007]. This method is the closest in technical essence to the claimed method and adopted as a prototype.

The use of the prototype method for processing dust concentrate of refining production (KAPA) along with a number of positive features is associated with the following negative consequences.

When leaching of CAPA (which almost always contains a certain amount of ammonium chloride) in the solution of caustic soda, the formation of noble metals (water-soluble amino complexes) soluble in water and stable in an alkaline environment occurs. As a result, not only the majority of chalcogenes and arsenic, but also some relatively small amount (up to 200 mg / l) of noble metals (BM) are transferred to the alkaline solution from the initial product, which significantly complicates and increases the cost of subsequent decontamination operations of the obtained solutions.

The technical result is to reduce the number of BM, passing into an alkaline solution during the processing of KPAP.

The achievement of the technical result is ensured by the fact that the dust concentrate of refining production is pulped in water, the pulp is acidified by adding acid to establish a pH value of 1-2, it is subjected to cementation by the addition of iron powder, then it is leached in a solution of caustic soda, the insoluble residue is separated from the alkaline solution and melted insoluble residue by adding fluxes and refining intermediate products to obtain a bottom heavy alloy, the bottom heavy alloy is crushed and Abaty as a concentrate of refining production.

The essence of the method consists in the restoration of BM from water-soluble amino complexes in the process of cementation by iron powder.

Using the proposed method can significantly reduce the amount of BM passing into an alkaline solution during the processing of KPAP, increase the direct extraction of BM in insoluble residue and reduce the cost of decontamination of alkaline solutions.

An example of using the method

We took 150 g of wet (W = 35.7%) dust concentrate from refining production (CAPA). According to the analysis, the initial product (by dry weight) contained, wt.%: Pt - 0.676; Pd 1.031; Rh 0.02; Ir 0.008; Ru - 0.314; PGM (in total) - 2.053%; Au 0.254; Ag - 14.69; Te - 4.62; Se - 4.89; Sn - 9.07; As - 2.36; Pb - 24.9.

The initial product was pulped in 300 ml of water, acidified with sulfuric acid until a pH of 1-2 was established, the pulp was heated to 80 ° C and cemented with iron powder until the ORP value was set to + 90 mV (iron powder consumption was 2 g). 88 ml of caustic soda (d = 1.457 g / cm ³ ) was added to the resulting pulp and leached in an alkaline solution with stirring at a temperature of 80-90 ° C for 1 h, after which the alkaline solution was separated by filtration from the insoluble residue. In this case, two products were obtained: an alkaline solution in an amount of 365 ml and an insoluble residue. The yield of the latter amounted to 138.7 g (W = 46.5%) or 76.9% of the starting product launched for leaching. According to the analysis, the content of BM in n.o. amounted to,%: Pt - 0.873; Pd 1.338; Rh 0.03; Ir - 0.01; Ru - 0.406; Au 0.321; Ag - 19.1%. Thus, the content of PGM, gold and silver (in total) increased and amounted to 22.078%, which is 1.3 times more than in the starting material before leaching.

Base elements passed into the caustic soda solution from the initial product. According to the results of the analysis, their concentration in solution was, g / l: Te - 5.72; Se - 7.11; Sn - 4.09; As 4.79; Pb - 10.39. Thus, 46.5% tellurium, 54.5% selenium, 17.0% tin, 75.9% arsenic, and 14.9% lead were transferred from the starting material into the solution. More than 99.9% of PGM, gold and silver remained in the insoluble residue. In an alkaline solution, 28.0 mg / L of PGM (in total) and 20.0 mg / L of silver were detected.

The second product obtained by filtration of the pulp — the insoluble residue — was melted by adding fluxes and refining intermediate products.

For this, an insoluble residue (74.2 g by dry weight) was mixed with the addition of a refined industrial product and fluxes. Refined industrial product (the so-called cementate) was taken in an amount of 100% by weight of the insoluble residue (i.e. 74.2 g), fluxes - silicate-sodium glass - in the amount of 15% by weight of the charge, soda ash - 7, 5% of the mass of the charge, coke - in the amount of 3.7% of the mass of the charge. The total mass of the charge was 200.9 g.

All components of the charge were mixed and loaded into a melting alundum crucible. The crucible was placed in a shaft laboratory electric furnace and subjected to isothermal exposure (melting) for 45 minutes at a temperature of 1300 ° C. After melting, the crucible was unloaded from the furnace.

After cooling the melt, a hardened product was recovered from the crucible, which was divided according to the formed phase boundaries. The following three melting products were obtained:

- 9.9 g of bottom heavy alloy of platinum metals and gold containing (according to ICP) 39.3% PGM and gold (in total);

- 47.2 g matte-like light alloy;

- 81.3 g of sodium silicate slag that does not contain (according to spectral analysis) platinum group metals and gold.

A matte-like light alloy can be subjected to nitric acid leaching of base metals and the recovery of precious metals using known methods.

The heavy BM bottom alloy is sufficiently brittle; it is crushed into powder and processed as a concentrate of refining production by known methods.

It should be noted that in a parallel experiment, when leaching a sample of the same batch of CAPA in a solution of caustic soda according to the prototype method, i.e. without cementing the pulp with iron powder, an alkaline solution was obtained containing 191.0 mg / l of PGM (in total) and 75.0 mg / l of silver, which is significantly inferior to the indicators achieved by the claimed method.

Claims (1)

A method of processing a dust concentrate of refining production, in which the initial product is pulped in water, the pulp is acidified by adding acid to establish a pH of 1-2, it is subjected to cementation by adding iron powder, then it is leached in a solution of caustic soda, the insoluble residue is separated from the alkaline solution and melted insoluble residue by adding fluxes and refining intermediate products to obtain a heavy bottom alloy, grinding and processing it as an affi concentrate azhnogo production.