RU2094499C1 - Method for processing concentrate of precious metals - Google Patents

Abstract

FIELD: processing concentrate of precious metals on the base of oxides of silicium and palladium; production of metals of platinum group by refining. SUBSTANCE: before dissolution concentrate which comprises oxide compounds of palladium and silica is mixed with carbon-containing reduction agent. Thus prepared mixture is heated till clinker is prepared. Then clinker is chlorinated in solution of hydrogen chloride acid. EFFECT: improved efficiency. 2 cl

Description

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

 The processing of raw materials in the refining production of PGM includes the operations of dissolving PGM to produce a chloride solution. Individual platinum and palladium and most of their compounds with base elements are relatively easily dissolved in a mixture of hydrochloric and nitric acids (aqua regia). Rhodium, iridium and ruthenium can be converted into a solution only by first converting them into compounds with certain base elements or solid solutions based on platinum and palladium. The choice of the method for the dissolution of PGMs from raw materials (leaching of the initial product directly or the use of preliminary activation operations by heat treatment with additives) depends on its composition. Depending on the ability of the feedstock to form PGM solutions during leaching in chloride media in the presence of an oxidizing agent, it can be classified into two groups: active and persistent.

 Noble metal concentrates in which palladium is in the form of oxygen compounds (oxides) against silica are classified as resistant to dissolution, since palladium oxide dissolves in chloride media to a small extent. So when such concentrates are leached in aqua regia, no more than 60% of palladium passes into the solution. Obviously, in order to achieve the complete conversion of palladium to solution, in this case, more complex processing methods are required.

For the processing of refractory concentrates, in particular schlich platinum, a method is known that includes staged leaching: first, the initial product directly in aqua regia and separation of the insoluble residue, then
the blending of an insoluble residue with barium peroxide, heat treatment of the mixture to form a cake, leaching of cake in hydrochloric acid.

 The purpose of the invention is the high recovery of all PGMs in solution.

 Closest to the proposed one is a method of processing a concentrate of precious metals, including the preparation of a mixture, heat treatment of a mixture to obtain a cake, grinding cake, leaching it in a hydrochloric acid solution, followed by separation of the solution from the insoluble residue by filtration.

The proposed method differs from the known one in that the precious metal concentrate based on silicon and palladium oxides is subjected to processing, the mixture is prepared by mixing the starting material with a carbon-containing reducing agent, the heat treatment to produce a cake is carried out at 600 900 ^° C, and the ground cake is leached with hydrochloric acid at supply of gaseous chlorine.

The essence of the proposed invention lies in the fact that during the calcination process in the presence of a reducing agent, the chemically passive in relation to the processes of chlorination of palladium oxides to the active states of the metal or carbides is almost completely restored. As shown by special laboratory experiments, the formation of chemically active phases of palladium occurs when using the temperature range 600 900 ^o C and such a duration of heat treatment that is sufficient to convert the original powder mixture into a state of sinter. The achievement by the product of calcination of the state of sinter is in this case a necessary and sufficient sign of the completeness of the formation of chemically active phases of palladium during calcination. The sintered state of the calcined product prevents the secondary oxidation of palladium metal by oxygen in the air when it is cooled in air and the silica crystallizes more, which helps to speed up the filtration of the solution when separating the insoluble residue from the pulp of the subsequent hydrochlorination operation. The method involves the launch on the operation of hydrochlorination of both directly lump cake, and cake, previously crushed into powder. The introduction of the operation of grinding sinter is advisable to intensify and simplify the hardware design of the chlorination process.

Calcination of the charge in the proposed method can be carried out in various types of furnaces, allowing to develop a temperature of 600 900 ^o C. However, for reasons of resource conservation, it is preferable to use induction heating in this case when loading the calcined charge in graphite-containing crucibles, which in itself is new, not resulting from modern level of technology.

 Example 1. They took 20 g of a concentrate of platinum metals containing oxide compounds of palladium and silica. The initial concentrate contains, platinum 4.2; palladium 31.9; Rhodium 0.9; iridium 0.31; ruthenium 0.38; 1.65 gold; silver 5.2.

The concentrate was mixed with 1 g of coke, the prepared charge was placed in a chamotte crucible and kept in a mine transmission at a temperature of 800 ^o C for 1 h. 17.65 g of sintered calcined material was unloaded from the crucible, which was chlorinated with gaseous chlorine in a solution of hydrochloric acid to a potential of 1050 mV

 The pulp was filtered, the insoluble residue was washed with hydrochloric acid.

 Received: 100 ml of solution 0 containing, g / l: platinum 8.3; palladium 63.1; Rhodium 0.9; iridium 0.25; ruthenium 0.4; gold 3.33 and 8.9 g of an insoluble residue of calcined PGM concentrate 8.9 g, which contained, according to spectral analysis, platinum traces; palladium 0.8; rhodium - 1.0; iridium 0.4; ruthenium 0.4; no gold was found.

Thus, the extraction into the solution during the hydrochlorination of the calcined concentrate was Pt 99.5; Pd 98.9; Rh 50; Ir 41; Ru 53; Au 99.5%
The resulting insoluble residue (BUT cake) was mixed with other refining intermediates and fluxes, based on the receipt of the mixture of the following composition, wt.

BUT calcined concentrate MPG 30
BUT magnesite lining 35
Ash kilns 15
Soda ash 10
Calcium oxide (fluff lime) 5
Coke 5
The prepared mixture was placed in a fireclay crucible and melted in a shaft electric furnace at a temperature of 1300 ^o C for 30 minutes

 During smelting, the target product of heavy alloy beads weighing 9.45 g, containing 24.5% of platinum metals and gold in total and slag weighing 11.9 g, containing only 0.8% of palladium from precious metals, was obtained. The extraction of MPN from the charge into the target alloy during melting was 95.9%. The PGM alloy is suitable for the extraction of PGM from it by known methods.

 Example 2. The initial product concentrate contained, wt. platinum 3.8; palladium 20.3; gold 3,5. According to x-ray analysis, the main phases in the concentrate are palladium oxide (PdO) and silica.

A concentrate of this composition in 50 55 kg portions mixed with 2 2.5 kg wood sawdust was loaded into graphite or graphite chamotte crucibles of an induction unit with two furnaces (power up to 200 kW, current frequency 800
100 Hz, crucible capacity 50 80 l). The mixture was heated using the supplied to the inductor, in the range of 40 to 60 kW to obtain a cake. The onset of the sintered state was determined by periodic breakdown of the strength of the heat treatment product when pierced with a crowbar. The duration of the heat treatment from the beginning of the voltage supply to the inductor to the formation of cake was 2 3 hours. The temperature in the furnace when the mixture reached the cake state was 800 850 ^o C. The sintered product was unloaded from crucibles into metal boats using hand scrapers.

 In total, 690 kg of concentrate were heat treated in this way. The weight of the cake was 610 kg.

 After grinding in a ball mill, 150 to 155 kg of specimens were chlorinated in a titanium reactor in a solution of hydrochloric acid (T: W 1: 3) with gaseous chlorine until a potential of 1050 mV was reached (relative to the silver-silver reference electrode). The resulting pulp was profiled, the insoluble residue was washed on the filter with a solution of hydrochloric acid, the products were analyzed for the content of platinum metals.

 Received 1,500 l of a solution containing 17.3 g / l of platinum and 91.6 g / l of palladium.

 The insoluble residue (210 kg by dry weight) according to spectral analysis contained, wt. platinum traces, Pd 1.25, Au traces.

 Thus, 98.1% of palladium and more than 99% of platinum and gold were recovered in the solution. The solution was aimed at the selective extraction of gold and platinum metals using known methods.

 The resulting insoluble residue was processed using a reflective fuel furnace in the same way as described in example 1.

Claims (2)

1. A method of processing a noble metal concentrate, including preparing a charge, heat treating the charge to obtain a cake, grinding the cake, leaching it in a hydrochloric acid solution, followed by separating the solution from the insoluble residue by filtration, characterized in that the precious metal concentrate based on silicon oxides and palladium, the preparation of the mixture is carried out by mixing the source material with a carbon-containing reducing agent, heat treatment to obtain a cake is carried out at 600 900 ^o C, and the leaching of crushed cake with hydrochloric acid is carried out with the supply of gaseous chlorine.  2. The method according to p. 1, characterized in that the heat treatment of the mixture with obtaining cake is carried out in an induction furnace when loading the mixture into graphite-containing crucibles.