RU2169780C1 - Platinum-containing concentrate processing method - Google Patents

Abstract

FIELD: precious metal technologies. SUBSTANCE: concentrates are subjected to oxidative firing to give ashes, which are brought into hydrochlorination reaction to transfer platinum metals into chloride solution, after which they are recovered from solution. According to invention, hot ashes are wetted at 200-350 C with organic reducing agent enabling removal of oxide passivating films from the surface of platinum metal grains, consumption of this agent (in particular, straw oil) being 5-10% of the weight of ashes. EFFECT: increased platinum metal transfer into solution in chlorination stage by 1/2 to 33% depending on the nature of metal. 2 cl, 1 tbl, 3 ex

Description

 The invention relates to the metallurgy of platinum metals and can be used in the production of platinum metals (PM) at non-ferrous metallurgy enterprises and refineries.

 There are various methods for processing platinum-containing concentrates containing from tenths to several tens of percent of the amount of PM. In this case, the key technological aspects are the pretreatment of concentrates and the subsequent transfer of platinum metals (PM) into solution, from where they are extracted by traditional methods, for example, sorption on anion exchangers or cementation (Maslenitsky I.N., Chugaev L.V. Noble metal metallurgy. M ., Metallurgy, 1972, 366 p.).

For example, a known method for the extraction of precious metals by chlorination of the material in a molten salt of KCl-MgCl ₂ at 300-650 ^o C with a purge of gaseous chlorine. After distillation of the volatile chlorides of aluminum, antimony, selenium and tellurium, the resulting melt is leached with acidified water with the conversion of platinum metals into solution (US Pat. No. 5,238,662). The implementation of the chlorination process in the melt requires complex hardware design, including, inter alia, an effective system of gas purification and capture of the resulting aggressive and highly toxic volatile chlorides, which is a significant obstacle to the implementation of the method.

 A known method of processing platinum-containing concentrates Bushveld (South Africa), including plasma melting to obtain enriched platinum-containing matte and subsequent hydrometallurgical extraction of PM (Zubatareva LI Prospects for platinum-bearing chromite. Ed. Journal. Izv. VUZov. Geol. And exploration. ., 1984. Dep. At VINITI 08/08/84, N 5882-84). The disadvantage of this method is the need to use an expensive plasma furnace of complex design (system "EPP-expanded plasma").

In industrial practice, hydrochlorination in combination with preliminary high-temperature (about 1000 ^o C) oxidative roasting is widely used to open platinum raw materials. The use of firing of the starting material ensures the oxidation of chalcogenides, arsenides, and other PM compounds that are difficult to open during chlorination to less resistant metal forms. In this case, high rates of PM transfer to the chloride solution are achieved, however, PM cannot be completely removed from the cinder. Incomplete extraction of PM in the chloride solution upon opening of the calcined platinum-containing raw material is caused by the formation, along with the metal forms, of PM oxides in the form of dense passivating films on the surface of PM grains (Ginzburg S.I. Analytical chemistry of platinum metals. M., Nauka, 1972, p. 88-89).

As a prototype of the present invention, a method developed by the US Bureau of Mining for opening platinum-containing concentrates of Stillwater deposits can be selected, including oxidative calcination of the concentrate at 1050 ^° C, preliminary leaching of the cinder with sulfuric acid solutions at 70 ^° C, oxidative leaching (hydrochlorination) at normal temperature with a mixture of hydrochloric acids and hydrogen peroxide for converting precious metals into solution and precipitation of PM and gold (Meretukov M.A., Orlov A.M. // Metallurgy of noble Metals. M., Metallurgy, 1991, p. 270).

The disadvantages of this method of processing platinum concentrates are:
1. Low extraction of PM in the chloride solution due to the formation of dense passivating oxide films on the surface of the PM grains.

 2. Obtaining at the stage of hydrochlorination of a solid product with a high residual content of platinum metals and, accordingly, the need to create a product turnover or the use of special technological operations to recover platinum metals from it.

 3. A significant amount of work in progress for platinum metals.

 The objective of the invention is to provide a method for processing platinum-containing concentrates with a technical result that allows to increase the extraction of PM in a chloride solution, to reduce the residual PM content in the chlorination residue, to increase the profitability of production by reducing the work in progress for platinum metals.

The technical result is achieved by the use of a method for processing platinum-containing concentrates by oxidative roasting, hydrochlorination of a cinder with the conversion of platinum metals into a chloride solution and subsequent isolation of platinum metals from the solution by known methods, characterized in that before hydrochlorination, the cinder is moistened with an organic reducing agent at 200-350 ^o C, providing removal of oxide passivating films from the surface of grains of platinum metals, with its consumption of 5-10% by weight of the cinder, while as an organic reducing agent use solar oil.

 The method is implemented as follows.

The platinum-containing concentrate is subjected to oxidative roasting (1050 ^o C) for 1 h. The resulting hot cinder at 200-350 ^o C is moistened with an organic reducing agent, such as solar oil, at a flow rate of 5-10% by weight of the cinder. In this case, the surface PM oxides are restored to less resistant metal forms, their reoxidation is excluded due to the low process temperature (the temperature of the hot cinder is lower than the temperature of the formation of PM oxides), there is no pollution of the cake with an organic reagent, the combustion products of which transfer to the gas phase. Hydrochlorination is carried out in a hydrochloric acid solution [HCl] = 200 g / l for 1 h in the presence of hydrogen peroxide.

The optimality of the distinguishing features is as follows:
the lower limit (200 ^o C) of the process temperature determines the minimum at which the necessary conditions are created for the restoration of inert oxide films and metallization of the surface of the grain PM; the upper limit (350 ^o C) determines the maximum at which there is no re-oxidation of metallized PM;
the choice of organic matter is determined by the range of temperatures of its boiling of 200-350 ^o C, which ensures, along with high efficiency recovery of oxide inert films, the absence of contamination of the cinder with organic matter and its combustion products;
the lower limit (5%) of the consumption of organic matter determines the minimum at which the necessary conditions are created for the restoration of inert oxide films and the metallization of the surface of PM grains; the upper limit (10%) is determined by technological (does not increase the extraction of PM in the solution at the chlorination stage) and economic feasibility.

The foregoing is confirmed by the following examples:
Example 1. A platinum-containing concentrate (the content of PM is 1000 g / t) was subjected to oxidative firing in a tube furnace at a temperature of 1050 ^o C for 1 h. Hot cinder at optional temperatures of 150, 200, 275, 350 and 400 ^o C moistened with solar oil with a consumption of 7-5% of the cinder weight. The obtained cake was leached (hydrochlorinated) in a hydrochloric acid solution [HCl] = 200 g / l in the presence of hydrogen peroxide for 1 h. The PM recovery from the cinder reduced under optimal conditions (275 ^o C) to the chloride solution was (%): 97, 3 Pt, 93.4 Pd, 75.2 Rh, 81.3 Ru.

Example 2. The conditions of oxidative roasting and hydrochlorination of the reduced cake are similar to Example 1. The hot cinder at 275 ^o C was wetted with solar oil at a variant flow rate of 2.5, 5, 10, 12.5% of the cinder weight. Recovery to the chloride solution after reduction of the cinder with solar oil at a rate of 2.5% and 12.5% was 96.2 and 97.3% Pt, 92.1 and 93.2% Pd, 58.9 and 75.2% Rh, 61, respectively. 0 and 80.2% Ru.

 Example 3 (prototype). Processing platinum-containing concentrate was carried out according to the conditions of the prototype. Recovery in solution is: 96.8% Pt, 91.9% Pd, 49.6% Rh, 48.3% Ru.

 Examples confirming the optimality of signs are presented in the table.

The data obtained indicate that the implementation of the proposed method for opening platinum-containing concentrates allows you to achieve the following effects:
Technical - increase the extraction of platinum metals in solution at the stage of hydrochlorination by 0.5-33% depending on the type of metal, reducing the residual content of platinum metals in the remainder of the hydrochlorination.

 Economic - increasing the profitability of production by reducing the work in progress for platinum metals.

Claims (2)

1. A method of processing platinum-containing concentrates, including oxidative calcination, hydrochlorination of a cinder with the conversion of platinum metals to a chloride solution and subsequent isolation of platinum metals, characterized in that before hydrochlorination of the cinder, the hot cinder is moistened with an organic reducing agent at 200-350 ^o C to remove oxide passivating films from surface grains of platinum metals, with its consumption of 5-10% of the weight of the cinder.  2. The method according to claim 1, characterized in that solar oil is used as an organic reducing agent.

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