MXPA96003324A - Procedure for the treatment of sulphurous minerals containing gold and / or silver and at least iron as a metal accompanying - Google Patents

Abstract

The ore that contains gold and / or silver and at least iron as the accompanying metal is calcined at temperatures of the order of 500 to 900 ° C., adding gas containing oxygen. In this operation, a mixture of solid materials containing metal oxides and an exhaust gas containing SO2 is formed. The solid matter mixture from the calcination is cooled, its temperature being lowered by at least 50 ° C. The cooled solids mixture is charged to a fluidized bed reactor, supplying exhaust gas containing SO2 to the fluidized bed reactor. In the reactor, metal sulphate is produced in the solid mixture, with at least 10% of the sulfur content being bound in the exhaust gas. The mixture of solids containing metal sulphate is extracted from the fluidized bed reactor, mixed with an aqueous acidic solution and the metal sulphate is dissolved in it. The remaining solids are taken to a gold extraction device and / or pla

Description

Procedure for the treatment of sulfur minerals containing gold and / or silver and at least iron as the accompanying metal. DESCRIPTION OF THE INVENTION The invention relates to a process for the treatment of a granulated sulfur mineral, containing gold and / or silver and at least iron as the accompanying metal, producing a gas containing S02 and a mixture of solid matters containing metal oxides, by calcination at temperatures within a field of between 500 and 900 ° C, with addition of free oxygen-containing gas. Procedures of this type have already been described in DE-C-4 122 895 and DE-C-4 329 417. In these cases, the calcination of the minerals is optimized. The produced exhaust gas, which contains S02, is cleaned and no longer comes into contact with the mixture of solid materials containing metallic oxides, produced in the calcination. The object of the present invention is to at least partially bind the S02 of the exhaust gases, during the treatment of the ore, and at the same time to improve the yield of obtaining metal, thus achieving a greater production of gold and / or silver. . According to the present invention, this is achieved in the process mentioned at the beginning, by cooling the mixture of solid materials, which contain metallic oxides from the calcination, reducing their temperature by at least 50 ° C, introducing into a fluidized bed reactor the mixing of cooled solids and conducting the exhaust gas containing SOa to the fluidized bed reactor, metal sulphate being produced in the solid matter mixture and binding at least 10% of the sulfur content in the exhaust gas in the form of metal sulphate, extracting from the fluidized bed reactor the solid matter mixture containing metal sulphate, mixing it and stirring it with an aqueous acid solution and thus dissolving the metal sulphate, separating the solids from the solution and conducting these solids into a extraction of gold and / or silver. In the fluidized-bed reactor, at least 20% of the sulfur content in the exhaust gas is preferably bound in the form of metal sulphate. The metal sulphate produced in the solid matter mixture in the fluidized bed reactor, for example ferric sulfate, is soluble in water and is removed in dissolved form from the solid matter mixture. In this way, the volume of pores in the remaining mixture of solids is considerably increased and the possibility of attack of the leaching solution (eg leaching with cyanide) in obtaining the metal is clearly improved. Since in this way copper, zinc and nickel can also be eliminated, at least partially, from the production of noble metal obtained as companion metals, this means a considerable reduction of the cyanide consumption for obtaining the noble metal. At the same time, the volume of subsequent treatment of the exhaust gas is reduced to eliminate the SO.- Copper, zinc and nickel can be obtained separately from the liquid phase. In the fluidized bed reactor, the metal sultafo is normally produced at temperatures between 100 and 650 ° C, but preferably between 200 and 600 ° C. The fluidized bed reactor may be configured in a single stage or also in several stages. As for the fluidized bed, it can be a stationary, circulating or also expanded fluidized bed. The important thing is that in the fluidized-bed reactor an intensive contact between the gas and the solid materials is achieved with sufficient residence times, in order to achieve the desired transformation of the metal oxides into metal sulfates. In the fluidized bed reactor it is transformed, e.g. eg, ferric oxide with S02 and oxygen, according to the following reaction: 2 Fe203 + 6 S02 + 3 02 - > 2 Fe2 (SO *) 3 Faster than S02 reacts S03 with ferric oxide, according to the reaction formula: Fe203 + 3 S03 - > Fe2 (S04) 3. In the fluidized-bed reactor, S03 from S02 under the catalytic effect of the metal oxides there existing in the presence of free oxygen, partly spontaneously, which favors the formation of sulphate. If it is desired to further accelerate the sulphate formation, it is recommended to catalytically oxidize the S02 in the exhaust gas, at least partially, before reaching the fluidized-bed reactor, obtaining S03, and driving to the reactor. fluidized bed an exhaust gas that is more or less enriched with S03. The reactions that take place in the fluidized-bed reactor are exothermic and care must be taken that temperatures do not rise much there. This occurs, on the one hand, because the mixture of solids from the calcination is first cooled, the temperature being reduced by at least 50 ° C, but preferably by at least 10 ° C, before the mixture of solid matter is delivered to the fluidized bed reactor. The mixture of solids containing metallic oxides, produced by the calcination of the sulphide ore, is preferably cooled to temperatures between 100 and 350 ° C, before being introduced into the fluidized bed reactor, and it is also convenient to evacuate the heat from the reactor. fluidized bed by means of indirect cooling With the aid of the attached drawing, possibilities of configuration of the process are explained.In this drawing a flow diagram of the process development is shown.To carry out the calcination, granulated mineral is first introduced into the pipeline. 1. The ore, which can also be a mineral concentrate, normally has grain sizes of the order of between 0.01 and 4 mm.The calcination is carried out at temperatures of the order of between 500 and 900 ° C in the bed circulating fluid in the calcination reactor 2, with the return cyclone 3. The fluidizing gas, which contains free oxygen, is i Introduced by blowing through the pipe 4. This gas can be normal air, air enriched with 02 or another gas rich in 02. In reactor 2 the metal sulfides are transformed into metal oxides and an exhaust gas containing S02. The solids and the exhaust gas arrive, through channel 5, to return cyclone 3, in which the solid materials are partially separated and partially returned to reactor 2 through pipes 7 and 8. A part of the solids at high temperature arrives, through the pipe 9, to a fluidized bed cooler 10, which has cooling elements 11 for indirect cooling. The fluidizing gas, for example air or cooled exhaust gas, containing S02, enters through line 12 and leaves the refrigerator 10 heated through line 13, which also empties into reactor 2. A cooled mixture of solid matter is extracted from the refrigerator 10 through the pipe 5 and can be conducted back to the reactor 2 partially through the pipe 16 in a manner not shown in detail in the figure. A cooled mixture of solids, containing metal oxides and coming from the cooler 10, arrives through line 19 to a fluidized bed reactor 20. To this fluidized bed reactor 20, exhaust gas, containing S02, is fed from the cyclone 3 through the pipe 21 and, through a central pipe 22, it is conducted to the fluidized bed of the reactor 20. Exhaust gas, which contains S02, exits reactor 20 through line 23, is cleaned of dust in an electric filter 24 and then is extracted through line 25. A partial stream of exhaust gas is conducted through from the pipe 26, passing through the blower 27, the pipes 28 and 31 and the distributor 32 in the form of fluidizing gas, to the reactor 20. Through the pipe 35 normal air, air enriched with 02 or oxygen is added technically pure. In reactor 20, the fluidizing gas first reaches the distribution chamber 33 of the gas, before passing up through the grate 34, to the fluidized bed above it and not shown in the drawing. The fluidized bed reactor 20 has a guide surface 36, which has the funnel-shaped upside down and is responsible for the circulation of the solids along the path marked in the drawing by the arrows 37. For the evacuation of the heat, through indirect heat exchange, serve the cooling elements 40. In the fluidized-bed reactor 20 are transformed, at least partially, metal sulfates the metal oxides fed through the pipe 19. If you want to accelerate the reactions In the case of sulphates, it is recommended to enrich the exhaust gas through line 43 with S03, which is effected by catalytic transformation of S02 in the presence of 02. For this purpose, the exhaust gas from line 43 is supplied to through a catalyst 44 (eg, a platinum catalyst with honeycomb structure), and then passed through an indirect refrigerator (45), to before driving the gas to reactor 20. Catalyst 44 transforms S02 and 02 into S03. Catalysts are customary on the market, for example based on vanadium pentoxide. Since the reaction in the catalyst 44 is exothermic, the installation of a refrigerator 45 is recommended below. The exhaust gas, which arrives in the pipe 25 from the electric filter 24 and is not conducted back to the reactor 20 in the continuous circuit, is conducted through another dust removal and cooling device (48), wherein, for example, a wet cleaning with a dry removal of the powder (for example, electric filter or sleeve filter) can be combined. The cleaned gas is removed by line 49. A partial stream of this gas is conducted by means of a blower 50 to a heater 51. The heated gas in line 43 is added in metered form, through line 52, normal air, air enriched with 02 or technically pure oxygen, before the gas enters the catalyst 44. A partial stream of the exhaust gas containing S02 from line 49 can be further conducted to the fluidized bed cooler 10 through the pipe 12a drawn with intermittent strokes. The solid matter-containing metal sulphate mixture exits the reactor 20 through line 53 and is conducted to a stirring tank 54. In this tank 54 diluted sulfuric acid is added through line 55 and thus dissolved as large as possible of metal sulfates. In the acid solution ferric sulfate dissolves very well; copper, nickel and zinc sulfates also dissolve well. The solids and the solution are then conducted through line 56 to a settling tank 57, from which the liquid phase poor in solids is then extracted through line 58. The phase rich in solids, which containing gold and / or silver, arrives through the pipe 59 firstly to a washing treatment device 60, before driving it through the pipe 61 to the installation, not shown in the figure, of extracting the gold and / or of the silver, especially by leaching with cyanide.

The liquid in line 58 contains dissolved metal sulphates, and part of the metals can be recovered. In a manner known per se, copper and silver can be bound in the iron scrap 62, which is located in the tank 63 as a filter layer and must be changed periodically. Subsequently, a zinc extraction device 65 is placed therein, for example, which is operated in a manner known per se, such as that described in EP-A-0 538 168. The remaining solution, containing ferric sulfate, is conducted to a stirred tank 68, in which limestone powder is added through line 69. In this way a gypsum sludge is formed, which is extracted by pipe 70 and can be deposited in a landfill after going through a dehydration facility not shown in the drawing. Example; In a pilot installation equivalent to that shown in the drawing, the calcination reactor 2 has a height of 4 meters and an internal diameter of 0.2 m. In this reactor it is charged, through the pipeline 1, a crude ore with a specific gravity of 2.52 kg / l, whose fine-grained part of less than 5 μm is 15% by weight and whose coarse-grained part exceeding 1 mm is 0.1% in weigh. The main components of the ore are the following: Fe 7.8% by weight S 9.0% by weight Zn 0.3% by weight Cu 0.2% by weight C (organic) 0.5% by weight Inert materials and quartz 82.2% by weight The mineral contains 8.5 ppm of gold and 25 ppm of silver.

Other process conditions are: - amount of raw ore, which passes through the pipe l: 20 kg / h - temperature in the calcination reactor 2: 680 ° C The quantity of the mixture of air and 02 conducted in total through pipes 4 and 13 to the calcination reactor is 30 Nm3 / h. The mixture of air and 02 contains 36% of the volume of 02. The calcined ore arriving through line 19 is led to the fluidized-bed reactor 20 in an amount of 19.0 kg / h and at a temperature of 200 ° C and It has the following composition: Fe202 11.8% by weight S 0.5% by weight ZnO 0.4% by weight CuO 0.3% by weight C (organic) 0.1% by weight Inert materials and quartz 86.9% by weight.

The mineral also has the aforementioned gold and silver content. The following gases are fed to the fluidised-bed reactor 20 through the pipes 21 and the distributor 32: Pipe 21 Distributor 32 Quantity (Nm3 / h) 29 3 Content of SOa (% volum.) 3.7 1.2 Content of S03 (% volum.) 0.2 0.01 Content of O. (% vol.) 30.0 30.0 Temperature 680 ° C 450'c The solid matter contained in the pipe 53 is evacuated in an amount of 20.5 kg / h with a temperature of 450 ° C. Its composition is as follows: Fe203 5.9% by weight Fe2 (S04) 3 12.3% by weight ZnSO * 0.7% by weight CuSO * 0.5% by weight C (organic) 0.1% by weight Inert materials and quartz 80, 5% by weight To the stirring tank 54 is added 200 liters / hour of dilute sulfuric acid with 1.5% by weight of H2SO4, in addition to the solid matter of line 53. The liquid in line 58 contains 4.5 kg / h of Fea (S04) 3, 0.14 kg / h of ZnS04 and 0.09 kg / h of CuS04. The suspension of solids, which passes through the pipe 59, contains 17 kg / h of solids, namely: Fe203 2.5% by weight S 0.6% by weight Inert materials and quartz 96.9% in weigh The content of Cu and Zn is less than 0.01% by weight. The mixture of solids is excellently suited for leaching with cyanide for the extraction of gold.

Claims (6)

1. Claims 1. Process for the treatment of a sulphide mineral in grain, which contains gold and / or silver and at least iron as the accompanying metal, in which it is produced, by calcination at temperatures of the order of between 500 and 900 ° C and adding free oxygen containing gas, a mixture of solids containing metal oxides and an exhaust gas containing S02, characterized in that the solids containing metal oxides from the calcination are cooled, the temperature being lowered by at least 50 ° C, the cooled mixture of solids is charged to a fluidized-bed reactor and exhaust gas containing S02 is introduced into the fluidized-bed reactor, producing in the mixture of solids metal sulphate and liquefying in the form of metal sulphate at least 10% of the sulfur content in the exhaust gas, extracting from the fluidized bed reactor the solid matter mixture which It contains metal sulphate, agitating it with an aqueous acid solution and thereby dissolving the metal sulphate, removing the solids from the solution and feeding the solids to a gold and / or silver extraction device.
2. 2. Method according to claim 1, characterized in that metal sulphate is produced in the fluidized bed reactor at temperatures between 250 and 650 ° C. Method according to claim 1 or 2, characterized in that at least a part of the S02 in the exhaust gas is catalytically oxidized to form S03 outside the fluidized-bed reactor, before the exhaust gas is led to the fluidized-bed reactor. Method according to claim 1 or according to one of the following claims, characterized in that the mixture of solids containing metallic oxides, produced by calcination of the sulphide ore, is cooled to temperatures of between 100 and 650 ° C, before charge it in the fluidized bed reactor. Method according to one of claims 1 to 4, characterized in that the sulphide ore is calcined in a circulating fluidized bed. Method according to one of Claims 1 to 5, characterized in that the exhaust gas containing SO2 is brought into contact with the solids mixture when the mixture of solids containing metal oxides is cooled.