The technical Held to which the invention relates

Generally speaking, the invention relates to extraction of solid materials through subsequent concentrate treatment using flotation, and actually to a new method of analysing lower contents of platinum metals in products of copper ore concentration, melting and refinement, as well as to a construction design of a new device, a stand-alone cell within the mill/hydrocyclone cycle, in order to achieve a desired exploitations of metal from copper concentrate and in refinement.

According to the International Patent Classification, the subject matter of the invention is categorized, i.e. classified and marked with classification symbols B03D 1/08, B03B 5/28 and B03B 5/34.

The technical problem

The technical problem solved through this invention is the following: how to determine metal balances of platinum metals with a lower content during processes of flotation concentration and metallurgical process; to improve exploitation of Pt and of Au by extracting their mineral particles which are otherwise contaminated (lost) to a significant extend (1 1%) when returned before reaching flotation cells for basic flotation, by using flotation concentration in a stand-alone cell and by treating hydrocyclone sand, which leads to reduced losses of useful components, first of all of gold and platinum in flotation process facilities, where useful components of copper, gold, silver, platinum and palladium are valorised from poor complex ores.

The condition of the technology

Procedures and methods for ore processing, as well as their extraordinary great significance and wide use, especially in exploitation conditions with increasingly poor resources, are generally known. In facilities for raw mineral preparation worldwide, a large number of concentration procedures and methods are used, such as gravitational methods, electromagnetic methods, CIP (Carbon-In-Pulp) process, only a few of which are being mentioned here: ASD/MET/MSR001 mass spectrometry, X-RAY diffraction method and OES JARRELL ASH 72000 (optical emission spectrography), for lower contents of platinum metals which provide inaccurate results that are useless for practical purposes, i.e. for creating metal balances of technological processes: concentration, electrolysis and refinement, in order to improve technological production parameters (since platinum is twice as expensive as gold and the price of palladium is 64% of the price of gold).

Searching through patent documentation and referring to professional literature in this field has not produced a similar solution of the set technical problem.

Short description of the essence of invention

According to the invention, the procedure consists of several stages and the device consists of a new construction design. In order to valorise all useful components (Pt, Pd) from a mineral raw material completely and reduce loss, the analysis of their content during a technological process is necessary, as follows: within the ore, the copper concentrate, the cathode, the anode mud in vats and the anode mud after refinement. The procedure is original and unique in the world, and it has been defined based on detailed fundamental laboratory and semi-industrial research of complex ores from Bor and Majdanpek. The device consists of an inlet box, a chamber with a mechanism support bridge, an outlet box with overflow trails, a rotating mechanism, an air valve, conical valves, an exhaust valve (a valve for discharging flotation cell from the cone), a drive unit with an electric motor and an automatic pulp level control system.

Brief description of figures in the drawings

The invention is described in detail in an example of carrying out of the invention shown in the drawings where:

Figure 1 - shows an improved technological process in the New flotation of the Majdanpek Copper Mine, and

Figure 2 - shows the appearance of the device (the flotation cell). Detailed description of the invention

The proposed procedure of analysing Pt and Pd consists of the applied inductively-coupled plasma (IPS) and direct-couplet plasma (DCP) techniques.

- Analysis is performed from a solution;

- From a complex matrix: the copper ore, the copper concentrate, the cathode, the anode mud before and after refinement;

- First, the elements are separated by slow evaporation with a mixture of concentrated (48%) HF and concentrated (70%) FINO ₃ ;

- They are evaporation till dry with HCRHNO ₃ then;

- Management procedure with aqua regia is repeated twice;

- Then the concentrated (37%) HCl+NaCl is added to the dry residual;

- Again evaporation;

- Finally, the dry residual of 2 mg minimum is dissolved in (1 + 1) HCl and diluted with distilled water in 50 ml solution;

- Metal ions are further transposed into gaseous state, in order to emit lights of wavelengths typical for each element;

- Then they are scanned with a computer (with a corresponding model) to the most distinct wavelength in the normal spectral range of 200-1000 nm using photoelectric detection;

- Measurements are performed using spectral lines with the following wavelengths: Pt - λ = 265.945 nm and λ = 306.471 nm, and

Pd - λ = 340.458 nm;

- Analysis of the emission spectrum and of the position of lines and its intensity is used to determine the content of individual elements, such as the Cu concentrate from Majdanpek (a monthly composite) in this case:

Pt = 2.7 g/t Pd = 1.3 g/t.

Flotation concentration, a method which is dominant in preparation of non-ferrous metal ores, allows extraction of useful components by heterocoagulation, regardless of natural characteristics, of the volume of the mineral grain, of its density and susceptibility, but depending on electrostatic characteristics of mineral surface only. The primacy of flotation concentration in non-ferrous metal preparation is also ensured by adequate designs of flotation concentration devices with regulating hydrodynamic parameters for optimal suspension of solid- phase pulp during non-ferrous metal concentration. This is why treatment of more than 2.4 billion tons of non-ferrous minerals using flotation concentration is expected in the future. It should be noted that the technology used for valorisation of platinum metals from platinum ores has been mentioned above. Using a stand-alone cell in the mill/hydrocyclone system also allows treatment of poor complex ores.

The new device allows a significant valorisation of the newly established elements Pt and Pd from poor complex ores into a copper concentrate, which has not been the case so far. Also the new device - the flotation cell (MG-8.5) - has been built in within the existing technological phases in facilities for flotation concentration in order to obtain final concentrates with a market value, whereby good technological exploitations are achieved.

Using the inductively-coupled plasma (IPC) and the direct-coupled plasma (DCP) techniques, the emission spectrometry analysis allowed determination of platinum metals in all products, from the ore to cathode platinum and cathode palladium.

This information allowed a final concept of further production, processing and refinement of copper, non-ferrous and rare metals to be defined. It allowed, in the first place, the stand-alone cell MG-8.5 to be built in the mill/hydrocyclone system, for flotation of platinum and gold minerals released from hydrocyclone sand, which allows improvements in Pt and Au exploitations. A comparison between the results of sections with or without the stand-alone cell, shown in Table 1, shows a very significant improvement of Pt and Au exploitations in the section with a built in stand-alone cell.

The stand-alone cell concentrate has a minimum of 17.62% Cu and participates in the total concentrate with 0.012% in terms of mass.

These results clearly indicate a high efficacy of using a stand-alone cell, according to the invention, for a more complete extraction of Pt and Au in the first place.

At the end of electrolysis from the mud, after the extraction of selenium, the anode mud is extracted from vats, dried and melted in a Dore furnace. The Dore furnace produces a Dore metal, which is a raw material for obtaining precious and platinum metals.

- After deselenisation, Ag is dissolved in baths with a mild HCl solution first, according to the relation:

2Ag + 2HCl 2AgCl + H ₂

- By introducing HNO ₃ to dissolve Ag, a complex Ag ion is obtained: 2NH ₃ + AgCl Ag (NH ₃ ) ⁺ + Cl ^"

Pure Ag is isolated from the solution through a cathode reduction by Ag ion electrolysis, according to the following relation: Ag ⁺ + e ^" .... Ag.

Oxygen is isolated at the platinum inert anode according to the reaction:

The new anode mud (Au+Pt+Pd) is melted and cast in the anode. Then the electrolysis of Au is performed in a mild HNO ₃ +HC1 solution. (A) in this phase is the alloy (PuPtPd), whereas the cathode is a gold foil which is used to obtain a gold bar. Impure Au is oxidised from the metal state (A) and passes to ion solution, with the voltage of 1.6 V, according to the reaction:

Au - 2e ^~ .... Au ²⁺ .

There is a reduction of gold to the cathode when the cathode has a set voltage of 1.013 V, according to the relation:

Au ²⁺ + 2e- .... Au.

There is a reduction of chloroplatinate from the Au refinement mud and a Pt powder is obtained according to the reaction:

Pt ²⁺ + SO ₂ ^2" + H ₂ O = Pt + SO ₄ ^2" + 2H ^1' .

Platinum oxides sulphate to a sulphate and platinum ion (salts) is reduced to pure platinum. The Pt ion reduction is performed with the electrode potential of 1.5 V, which is more negative than the standard value of a Pt metal ion by 0.1 V. With respect to this, there is an oxidation of metal from the anode in case its potential is higher than the standard potential of the element (chloroplatinate) by 0.1 V. Finally, Pd is extracted from the Pt refinement mud. Exploitations of silver, gold, platinum and palladium of 98% are achieved in the refinement process.

The effects of the new method for determination of lower contents of Pt and Pd as well as the new construction of the stand-alone cell MG-8.5 are an increased exploitation of Pt (11%) and exploitation of Au (6%), and exploitations of Ag, Au, Pt and Pd in the refinement process are 98%.

In financial terms, exploiting off the newly established elements to copper concentrate raises its value: platinum raises it by 18.7% and palladium by 6.5%, i.e. by 186 USD per ton.

The improved technological procedure is shown on Figure 1, where a schematic circuit diagram is given for: the bellt, the ball mill with 5.7 m diameter and 8.53 m long, the stand-alone cell, the hydrocyclone and the hydrocyclone pump.

The new method for analysing low contents of platinum metals and the new construction of the stand-alone cell (MG-8.5) allowed improvement of technological process of flotation concentration and refinement, which provide the best exploitations of gold, platinum and palladium. Treatment of poor complex ore with a mean content of elements: Cu=0.432%, Au=0.280g/t, Pt=0.102g/t, Pd=0.071g/t, Ag=1.506g/t obtained the concentrate with a 23.310% quality containing 9.824g/t Au, 2.800g/t Pt, 1.600g/t Pd and 49.730g/t Ag, and the exploitation is 89.500% Cu, 58.420% Au, 57.620% Pt, 51.31% Pd and 55.210% Ag. A comparison analysis of technological results of the improved and the unimproved process shows that technological exploitations in the improved process are higher by Cu=I .37%, Au=6.05% H Pt=I 1.50%. This is the main argument in favour of the improved process, having in mind production reactivation as well as larger exploitations in the refinement process by 2.0%.

According to the invention, the use of the stand-alone cell allows the increase of platinum exploitation by 11% and of gold exploitation by 6%. Since there is no information on the use of a similar equipment (like Autocumpu) in higher-capacity facilities for copper, gold and silver concentration, which can help calculate the size of the unit capacity, the adequate solution of 8.5 m has been obtained from hydrodynamic parameters in an industrial prototype [turbulence, aeration, rotor characteristics, cell flow volume (D _t y/V _st =3.41) and the time pulp stays in the cell being equal to t=l,0 min].

The device is better known under the title the stand-alone flotation cell (MG-8.5). It consists of the inlet box 1 for inserting raw material into the chamber 2 with the mechanism support bridge 4 with the rotor 10 rotating in the stator 11 and driven by the gear unit 6. In the top part of the cell there is the cylindrical outlet box 3 where reagents and a frothing device are inserted and where froth is made through turbulence in 1 minute. Air is supplied over the box 3 and regulated by the air valve 5. The cyclone is geared through the driving unit 6, with the electric motor. On the bottom of the cell there is the exhaust valve 7, i.e. the valve for discharging the flotation cell from the cone connected to the chamber 8, where pulp and froth levels are maintained using the level regulation device 9. The box 3 is a zone of mineralised froth, where froth is extracted and removed, the chamber 3 is a zone of laminar flow (hydraulic transport), under which there is a turbulent zone, where solid phase, water and air are mixed.

The basic characteristic of the applied flotation cell (MG-8.5) mechanism is that it disperses air in the entire chamber, thereby maintaining the solid phase in suspension. This is especially achieved in conditions of treating large grains of hydrocyclone sand, with the density of 60-65% solid, through the pulp circulating between the rotor 10 and the stator 11. Mechanisms with different dimensional characteristics are not able to perform this without additional turbulence elements. The shape of the mechanism (a cone) as well as the chambers allow larger quantities of air, 88 m ³ /m ³ and 1,35 m ³ /m ² , which is higher than other types by 30%. The conical shape of the rotor 10 allows using the entire rotor height to disperse air. This means that the density of raising air bubbles is constant in all parts of the chamber. The cell rotor prevents precipitation of the solid phase, due to efficient pulp agitation in the cell chamber, especially in conditions of treating a rough product such as hydrocyclone sand that cannot be treated in standard flotation cells. The conical shape of the cell chamber also allows the quantity of precipitated solid phase to be only 1.2% of the work capacity of the cell. This quantity is 10- 15% in a rectangular shape of the chamber, by treating a fine product into the hydrocyclone overflow. The shape of the mechanism and the flotation cell chamber allows the machine to start with a full load. This is very important since it operates in a technological mill/hydrocyclone system, because it does not interfere with the operation of the system and there is no loss of useful metals as the results of the cell discharge. The shape of the mechanism and of the chamber is significant because it moves large grains toward the centre of the cell chamber, where they are directed into circulation by the mechanism. A larger depth of the chamber than in other types allows better selectivity of useful minerals and requires a smaller installation space. The selectivity parameter has been improved due to the mechanism being at larger distance from the zone of the mineralised froth. The conical shape of the chamber MG-8.5 is lighter because of a self-support construction with the standard rectangular shape used for the identical volume of 8,5 m , making the difference of 1,200 kg. The cell (MG-8.5) is installed on its own profiles without any additional supports.

The stand-alone cell, compared to the "ANTOCUMPO" design (there are no other designs), is characterised by higher exponential values of the most important hydrodynamic parameters expressed by the ratio of the rotor diameter and the inner cone Dty/Vst in the first place, as well as by the Renolds-number, therefore by a higher grade of suspension homogeneity.

The position of the rotor and the cone within the chamber allows a maximum suspension effect for different granulometric compositions of the solid phase which meets a 1 -second criterion with densities between 60-70% solid in gold and platinum minerals.

The procedure that is the subject matter of this application is original and unique in the world, defined based on detailed fundamental laboratory and semi-industrial research of complex ores from Bor and Majdanpek lasting several years.

The new device allows a significant valorisation of the newly established elements Pt and Pd from poor complex ores into a copper concentrate, which has not been the case so far. The new device - the flotation cell (MG-8.5) - has also been built in within the existing technological phases in the facilities for flotation concentration in order to obtain final concentrates with a market value, whereby good technological exploitations are achieved.

This process is successfully used in facilities with significantly lower capacities than our 300,000 t/year compared to 6,000,000 t/year where much richer sulphide minerals and precious metals are treated. This stand-alone cell is used in a high-capacity mill/hydrocyclone system for the first time and it allows a total exploitation of Au=58.7% and Pt=57.6% from a poor raw material.