(19)
(11)EP 3 362 184 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
04.12.2019 Bulletin 2019/49

(21)Application number: 16794367.9

(22)Date of filing:  12.10.2016
(51)International Patent Classification (IPC): 
B03D 1/06(2006.01)
B03D 103/02(2006.01)
B03D 101/06(2006.01)
(86)International application number:
PCT/FI2016/050713
(87)International publication number:
WO 2017/064369 (20.04.2017 Gazette  2017/16)

(54)

DIFFERENTIAL FLOTATION OF SULFIDE ORES FOR RECOVERING REFRACTORY GOLD

DIFFERENZFLOTATION VON SULFIDERZEN ZUR GEWINNUNG VON REFRAKTÄREM GOLD

FLOTTATION DIFFÉRENTIELLE DE MINERAIS DE SULFURE POUR RÉCUPÉRER DE L'OR RÉFRACTAIRE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 13.10.2015 FI 20155726

(43)Date of publication of application:
22.08.2018 Bulletin 2018/34

(73)Proprietor: Outotec (Finland) Oy
02230 Espoo (FI)

(72)Inventors:
  • MOILANEN, Jari
    02320 Espoo (FI)
  • LEPPINEN, Jaakko
    02230 Espoo (FI)

(74)Representative: Papula Oy 
Mechelininkatu 1 a
00180 Helsinki
00180 Helsinki (FI)


(56)References cited: : 
  
  • TUTEJA R K ET AL: "Studies on differential flotation characteristics of arsenopyrite/pyrite concentrate", PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON EXTRACTIVE METALLURGY OF GOLD AND BASE METALS,, 1 January 1992 (1992-01-01), pages 217-219, XP009193226,
  • WEIR D ROBERT ET AL: "REFRACTORY GOLD: THE ROLE OF PRESSURE OXIDATION", GOLD 100, PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON GOLD,, vol. 2, 1 January 1986 (1986-01-01), pages 275-285, XP009193223,
  • Y. LIU ET AL: "Flotation separation of carbonate from sulfide minerals, I: flotation of single minerals and mineral mixtures", MINERALS ENGINEERING., vol. 17, no. 7-8, 1 July 2004 (2004-07-01) , pages 855-863, XP055338121, GB ISSN: 0892-6875, DOI: 10.1016/j.mineng.2004.03.006
  • ' Connor ET AL: "0892-6875(94)E0028-A THE FLOTATION OF GOLD BEARING ORES -A REVIEW", Minerals Engineering, 1 January 1994 (1994-01-01), pages 839-849, XP055338300, Retrieved from the Internet: URL:http://ac.els-cdn.com/0892687594901287 /1-s2.0-0892687594901287-main.pdf?_tid=40b 37b30-e231-11e6-bfba-00000aab0f01&acdnat=1 485261364_ad225f68676bb71a56000b892cede617
  • K. A. KYDROS ET AL: "Processing an Auriferous Pyrite Concentrate in the Presence of Reducing Agents", CANADIAN METALLURGICAL QUARTERLY, vol. 34, no. 1, 1 January 1995 (1995-01-01), pages 15-20, XP055338385, CA ISSN: 0008-4433, DOI: 10.1179/cmq.1995.34.1.15
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

Field of the invention



[0001] The present invention relates to recovery of gold from materials comprising refractory gold-containing minerals and more particularly to a method of beneficiating gold-containing materials comprising refractory gold-containing sulfidic minerals prior to gold leaching for increasing concentration of leachable gold in the gold-containing material.

Background of the invention



[0002] Currently gold-containing materials such as gold ores and concentrates are almost exclusively subjected to cyanide leaching for recovery of gold. However, in non-free-milling gold-containing materials such as refractory ores and concentrates gold particles are in locked within a matrix, most commonly sulfidic minerals, and cyanide solution cannot break up the sulfide structures such as pyrite (FeSz) and/or arsenopyrite (FeAsS). Thus pretreatment is necessary to decompose the mineral structure to liberate gold for subsequent recovery. Typically gold-containing refractory sulfidic materials is preprocessed before leaching by pressure oxidation (POX) to facilitate the recovery of gold at economic scale. There are also processes recovering gold using halide media from sulfidic or other gold-containing materials. However, presence of refractory sulfidic materials decreases gold recovery also in these processes.

[0003] In pressure oxidation sulfidic minerals are oxidized exposing encapsulated gold and liberating it into solution for subsequent recovery by leaching. The POX process takes place in an autoclave in harsh conditions at high temperature and high pressure. The cost of such autoclave equipment is high and often the autoclave capacity limits the processing capacity of the gold processing plant.

[0004] To maintain the heat and acid balance the POX process also requires certain sulfur content in the treated material. The sulfur content can be adjusted before the POX processing by processing all or part of the material in a sulfide flotation process where material having low sulfur content is removed as flotation tailings and the flotation concentrate is reported to the POX.

[0005] WO2013110757A1 discloses a method for enrichment of metal sulfide ores in desired minerals in cases where the ores have sulfide-containing gangues by addition of an oxidant to slurries prepared from the ores during or immediately prior to froth flotation without any conditioning of the pulp.

[0006] US6210648B1 discloses a method for flotation of refractory auriferous sulfides using an oxygen-deficient flotation gas for a non-selective flotation of different iron-containing sulfide mineral species prior to POX. The method promotes the flotation of the refractory auriferous sulfides and claims to enhance separation of sulfide minerals, including refractory auriferous sulfides, from non-sulfide gangue material. The flotation concentrates are recovered from the flotation froth enriched in sulfide minerals. However, the method does not allow selective separation of sulfidic minerals from each other.

[0007] Also Tuteja et al: "Studies on differential flotation characteristics of arsenopyrite/pyrite concentrate", Proceedings of the international conference on extractive metallurgy of gold and base metals, 1992, pages 217-219 and Weir et al: "Refractory gold: The role of pressure oxidation", Gold 100, Proceedings of the international conference on gold, Vol. 2, 1986, pages 275-285 deal with the recovery of refractory gold.

Brief description of the invention



[0008] It is thus an object to provide a method and an apparatus for implementing the method so as to alleviate the above disadvantages. The objects of the invention are achieved by a method and a process, which are characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.

[0009] The surface modifying froth flotation is based on selective modification of the surface of the reactive sulfidic mineral particles having high gold content. This may be achieved by adjusting the electrochemical potential of the froth flotation process to a level where the surfaces of the reactive sulfidic mineral particles are chemically modified rendering the reactive sulfidic mineral particles having high gold content hydrophilic and non-floatable while the non-reactive sulfidic mineral particles having low gold content remain hydrophobic. Modification of the surface of the particle can be attained by addition of a surface modifying chemical such as oxidizing or reducing agent or by other chemical means.

[0010] It is an advantage of the present method is that when material comprising mostly gold-containing sulfidic minerals is processed the POX processing capacity is increased and/or capex costs relating to POX process is reduced.

Brief description of the drawings



[0011] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the drawings, in which

Figure 1 illustrates as a first example a process flow of a process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals; and

Figure 2 illustrates as a second example a process flow of a process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals;

Figure 3 illustrates as a third example a process flow of a process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals;

Figure 4 illustrates flotation recovery rate of different types of sulfidic pyrite minerals as a factor to electropotential of the flotation pulp.


Detailed description of the invention



[0012] The present invention is directed to recovery of gold form gold-containing raw materials refractory gold-containing sulfidic minerals. Gold in refractory gold-containing minerals is poorly amenable to leaching making the recovery process utilizing direct cyanidation uneconomical. Typical gold-containing material comprising refractory gold-containing minerals has a gold recovery rate less than 80% when subjected to direct cyanidation. The term "refractory gold-containing material" refers to the presence of gold locking or cyanide consuming materials, particularly sulfidic minerals such as iron sulfides (e.g. pyrite, marcasite, pyrrhotite), arsenic sulfides (e.g. arsenopyrite, orpiment, realgar), copper sulfides (e.g. chalcopyrite), antimony sulfides (e.g. aurostibnite, stibnite), tellurides, elemental sulfur, or any mixture thereof.

[0013] Said gold-containing raw material typically comprises less than 80% w/w, in particular less than 50% w/w, preferably less than 35% w/w, more preferably less than 25% w/w, even more preferably 10 to 0% w/w native gold of the total gold in the said raw material, the total gold comprising native gold and gold locked in the raw material, in particular in sulfidic minerals. The term "native gold" refers to free-milling gold as opposite to gold locked in the material, in particular sulfidic minerals such as iron sulfides (e.g. pyrite). Typically said refractory gold-containing raw material is or is derived from ore or concentrate wherein the main mineral is pyrite or arsenopyrite. In addition to gold and sulfur, the said raw material may further comprise other elements such as silver, copper, nickel, cobalt, zinc, iron, lead, aluminum, and/or silicon.

[0014] Such gold-containing refractory raw material comprises 1) a first type of refractory sulfidic minerals having high gold content and 2) a second type of refractory sulfidic minerals having low gold content. It has been surprisingly realized that there is marked difference the chemical reactivity of said first type of refractory sulfidic minerals having high gold content and said second type of refractory sulfidic minerals having low gold content although said first type and said second type of sulfidic minerals are to be classified within a single species of refractory sulfidic minerals, e.g. pyrite. The first type of refractory sulfidic minerals having high gold content appears to have reactive surface while the second type of refractory sulfidic minerals having low gold content appears to have non- or less-reactive surface. As gold is in particular associated with the reactive sulfidic minerals it is desirable to be able to separate the different types of the refractory sulfidic minerals to improve the quality of the POX processes material. The present process is based on selective modification of the surfaces of the reactive refractory sulfidic mineral particles having high gold content thus making the said particles non-floatable.

[0015] For example gold bearing pyrite varies in mineral morphology, in particular surface area of the sulfidic mineral. Reactive pyrite having high gold content is typically present in the raw material as microcrystalline pyrite, whereas non-reactive pyrite having low gold content is present as coarse pyrite.

[0016] The gold content of the reactive sulfidic minerals having high gold content is higher than the gold content of the non-reactive sulfidic minerals having low gold content. In particular the gold content of the reactive sulfidic minerals having high gold content is above 5 pm, preferably above 8 ppm, more preferably between 10 to 100 ppm. Further in particular the gold content of the non-reactive sulfidic minerals having low gold content is below 5 ppm, preferably below 1 ppm, more preferably between 0 to 0.1 ppm.

[0017] Accordingly provided herein is a process for recovery of gold form gold-containing raw materials comprising refractory gold-containing minerals, in particular gold-containing refractory sulfidic minerals, comprising
  1. (a) obtaining gold-containing raw material comprising refractory gold-containing sulfidic minerals comprising first type of refractory sulfidic mineral having high gold content and second type of sulfidic mineral having low gold content;
  2. (b) forming a mineral pulp comprising first type of refractory sulfidic mineral particles having high gold content and second type of sulfidic mineral particles having low gold content by suspending ground gold-containing material in water and optionally further milling the material;
  3. (c) conditioning the mineral pulp by addition of a surface modifying chemical for modifying the surface of the first type of refractory sulfidic mineral particles having high content thus making the said particles non-floatable to obtain a conditioned pulp;
  4. (d) subjecting the conditioned pulp to a froth flotation process to separate first type of refractory sulfidic mineral particles having high gold content from the second type of sulfidic mineral particles having low gold content;
  5. (e) recovering the non-floatable first type of refractory sulfidic mineral particles having high cold content as flotation tailings;
  6. (f) pressure oxidizing (POX) the flotation tailings recovered in step (e) to obtain a discharge slurry comprising liberated gold; and
  7. (g) recovering gold from the discharge slurry obtained in step (f).


[0018] Figure 1 is illustrates a first example of a process for the recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals. Referring to Figure 1, gold-containing refractory raw material comprising 1) a first type of refractory sulfidic mineral having high gold content i.e. "reactive refractory sulfidic mineral" and 2) a second type of refractory sulfidic mineral having low gold content i.e. "non-reactive refractory sulfidic mineral", typically provided as ground ore, is mixed with water to form a mineral pulp 1. Said mineral pulp comprising reactive refractory sulfidic mineral particles having high gold content and non-reactive sulfidic mineral particles having low gold content is subjected to a conditioning phase 10 wherein the reactive refractory sulfidic mineral particles are deactivated i.e. rendered aerophobic and non-reactive to flotation chemicals by addition of a surface modifying chemical 2, which modifies the surface of the reactive sulfidic mineral particles. Deactivation of the reactive refractory sulfidic mineral particles thus renders said particles non-floatable while the non-reactive sulfidic mineral particles which do not interact or react with the surface modifying chemical 2 remain floatable. The deactivation of the first type of sulfidic mineral particles having high gold content accordingly prevents enrichment of gold in froth in the following selective sulfidic mineral forth flotation phase 20, and allows selective removal of second type of sulfidic mineral particles having low gold content.

[0019] For allowing deactivation of the reactive sulfidic mineral particles before the flotation phase, the conditioning phase 10 is performed before selective sulfidic mineral froth flotation phase 20. Preferably the surface modifying chemical 2 is added at least 2 minutes before initiation of the selective sulfidic mineral flotation phase 20. For enhanced selectivity, the surface modifying chemical 2 is added at least 5 minutes before initiation of the flotation phase 20. As under extended exposure to the surface modifying chemical 2 also some of the second type of sulfidic mineral particles having low gold content may become deactivated and thus made less readily floatable, the duration of the conditioning phase 10 preferably does not exceed 30 min, more preferably 15 min, even more preferably 10 min. However, the desirable duration of the conditioning phase 10 is dependent on the relative nature of the first type and second type of sulfidic mineral particles and even longer duration of the condition phase 10 may be tolerable.

[0020] The conditioning phase 10 is preferably performed in an agitated reactor referred herein as "a deactivation reactor".

[0021] The surface modification of the reactive pyrite minerals having high gold content is attained in the conditioning phase 10 by introduction of a surface modifying chemical 2. Desirable amount of the surface modifying chemical is dependent on the surface area of reactive pyrite and the amount of other minerals consuming the surface modifying chemical 1. Preferably the amount of the surface modifying chemical 1 is 50 to 500 g/t of treated ore. Preferably the surface modifying chemical 2 is selected from a group consisting of nitrogen, oxidizing agents, reducing agents, complexing agents and any mixtures thereof.

[0022] In a particular example, modifying the surface of the reactive sulfidic mineral particles making the said particles non-floatable is accomplished by oxidizing the surfaces of the reactive sulfidic mineral particles by dosing of an oxidizing agent. Preferably said oxidizing agent is selected from a group consisting of hydrogen peroxide, oxygen, ozone, alkali permanganate, chlorine, bromine, sulfuric acid, and any mixtures thereof. More preferably said oxidizing agent is hydrogen peroxide. The suitable amount of the oxidizing agent is dependent on the surface area of reactive pyrite and the amount of other minerals consuming the oxidizing agent in the selected condition such as electrochemical potential. Preferably the amount of the oxidizing agent is 50 to 500 g/t of treated ore.

[0023] In an alternative example, modifying the surface of the reactive sulfidic mineral particles making the said particles non-floatable is accomplished by reducing the surfaces of the reactive sulfidic mineral particles by dosing of a reducing agent. Preferably said reducing agent is selected from a group consisting of hydrogen, carbon monoxide, sodium sulfide, sodium hydrosulfide, sodium dithionite, sulfur dioxide, ferrous sulfate, Fe powder, Zn powder, and any mixtures thereof. The suitable amount of the reducing agent is dependent on the surface area of reactive pyrite and the amount of other minerals consuming the reducing agent in the selected condition such as electrochemical potential. Preferably the amount of the reducing agent is 50 to 500 g/t of treated ore.

[0024] In an alternative example, modifying the surface of the reactive sulfidic mineral particles making the said particles non-floatable is accomplished by modifying the surfaces of the reactive sulfidic mineral particles by dosing of a complexing agent. Preferably said complexing agent is selected from a group consisting of ethylenediaminetetraacetic acid (EDTA), diethylenetriamine (DETA), alkali cyanide, ammonia, alkali chloride, and any mixtures thereof. The suitable amount of the complexing agent is dependent on the surface area of reactive pyrite and the amount of other minerals consuming the complexing agent in the selected condition such as electrochemical potential. Preferably the amount of the complexing agent is 50 to 500 g/t of treated ore.

[0025] After conditioning phase 10 has been finished the conditioned pulp 11 comprising deactivated first type of refractory mineral particles is subjected to the selective sulfidic mineral froth flotation phase 20. The conditioned pulp 11 is introduced to tanks known as flotation cells that are aerated to produce bubbles. Any aerophilic and/or hydrophobic particles attach to the gas bubbles, which rise to the surface forming a froth. In the selective sulfidic mineral froth flotation phase 20 the non-reactive sulfidic mineral particles remaining or are rendered aerophilic by optional addition of one or more of a surfactant, a frother, or a collector chemical and separation is achieved by passing air bubbles through the conditioned slurry. The undesirable second type of refractory sulfidic mineral particles having low gold content adhere to the air bubbles forming a froth floating on the surface of the pulp.

[0026] The forth is removed as a flotation overflow 22 and the first type of refractory sulfidic mineral particles having high remain in the pulp together with any gangue mineral unresponsive to the froth flotation and can be recovered in as the flotation underflow 21 the form of a mineral pulp, i.e. flotation tailings.

[0027] The flotation tailings 21 are then subjected to a pressure oxidation phase 30, wherein under conditions known to a skilled person, the sulfidic minerals are oxidized exposing encapsulated gold and liberating it into solution. Gold can then be recovered from the thus obtained discharge slurry 31 comprising liberated gold by conventional methods known to a person skilled in the art, for example by leaching.

[0028] Gold containing raw materials typically comprise also silicates in addition to gold bearing minerals. If desired, these silicates may be removed from the mineral pulp prior to pressure oxidation phase 30. Removal of the silicates can be performed either before separation of the first type and second type of sulfidic minerals or after it.

[0029] Figure 2 illustrates as a second example a process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals wherein silicates are removed by flotation after separation of the reactive and non-reactive sulfidic minerals by conditioning 10 and selective sulfide froth flotation 20. In Figure 2 like components are designated by the same reference numerals as used in Figure 1.

[0030] As already discussed in connection of Figure 1, mineral pulp 21 comprising second type of sulfidic minerals having high gold content has been recovered as flotation tailings from the selective sulfidic mineral flotation phase 20. In the example presented in Figure 2, the mineral pulp 21 is subsequently subjected to a silicate flotation phase 40 before it is subjected to pressure oxidation phase 30.

[0031] The silicate flotation phase 40 can be performed by any conventional method known to a person skilled in art. In silicate flotation phase 40 silicates are floated rendering a silicate-depleted mineral pulp 41 comprising sulfidic minerals having high gold content depleted of silicates as the flotation tailing i.e. flotation underflow and the silicates are removed as the overflow 42 of the flotation phase. After this further beneficiation phase, the obtained silicate-depleted mineral pulp 41 is then subjected to pressure oxidation as discussed in context of Figure 1.

[0032] Figure 3 illustrates as a third example a process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals wherein the silicates are removed by bulk sulfide flotation of sulfidic mineral particles before separation of the first type and the second type of sulfidic mineral particles by conditioning 10 and selective sulfide froth flotation 20. In Figure 3 like components are designated by the same reference numerals as used in Figure 1 and/or Figure 2.

[0033] Referring to Figure 3, gold-containing raw material, typically ground ore, is mixed with water to form a mineral pulp 1. Said mineral pulp is subjected to a bulk sulfide flotation phase 50, wherein sulfidic minerals are floated and thus separated from silicates.

[0034] The bulk sulfide flotation phase 50 can be performed by any conventional method known to a person skilled in art, rendering a pre-treated mineral pulp 51 depleted of silicates and comprising both first type of refractory sulfidic mineral particles having high gold content and second type of refractory sulfidic mineral particles having low gold content as the overflow. The silicates are depressed and removed as the underflow 52 of the silicate flotation phase 50. After this bulk sulfide flotation phase 50, the pre-treated mineral pulp 51 is then subjected to a conditioning phase 10 and a selective sulfidic mineral flotation phase 20, followed by a pressure oxidation phase 30, as discussed in context of Figure 1.

[0035] Figure 4 illustrates exemplary flotation recovery rate of different types of sulfidic pyrite minerals as a factor to electropotential of the flotation slurry. Pyrite 1 illustrates recovery of reactive pyrite minerals having high gold content and Pyrite 2 illustrates recovery of non-reactive pyrite minerals having low gold content. As can be seen from the Figure 2, when the conditions of the flotation slurry are kept at the desired range mainly Pyrite 1 is recovered indicating that in these conditions only the surfaces of the reactive sulfidic mineral particles are modified thus rendering the said particles non-floatable while surfaces of Pyrite 2 remain unmodified and can be removed by flotation.

[0036] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.


Claims

1. A process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals, in particular gold-containing refractory sulfidic minerals, comprising

(a) obtaining gold-containing raw material comprising refractory gold-containing sulfidic minerals comprising first type of refractory sulfidic mineral having high gold content and second type of sulfidic mineral having low gold content, said first type and said second type of sulfidic minerals are to be classified within a single species of refractory sulfidic minerals;

(b) forming a mineral pulp comprising first type of refractory sulfidic mineral particles having high gold content and second type of sulfidic mineral particles having low gold content by suspending ground gold-containing material in water and optionally further milling the material;

(c) conditioning the mineral pulp by addition of a surface modifying chemical for modifying the surface of the first type of refractory sulfidic mineral particles having high content thus making the said particles non-floatable to obtain a conditioned pulp;

(d) subjecting the conditioned pulp to a froth flotation process to separate first type of refractory sulfidic mineral particles having high gold content from the second type of sulfidic mineral particles having low gold content;

(e) recovering the non-floatable first type of refractory sulfidic mineral particles having high gold content as flotation tailings;

(f) pressure oxidizing (POX) the flotation tailings recovered in step (e) to obtain a discharge slurry comprising liberated gold; and

(g) recovering gold from the discharge slurry obtained in step (f).


 
2. A process as claimed in claim 1, wherein the gold-containing material comprising refractory gold-containing minerals has a gold recovery rate less than 80% when subjected to direct cyanidation.
 
3. A process as claimed in claim 1, wherein the refractory gold-containing material comprises gold locking or cyanide consuming materials, particularly sulfidic minerals such as iron sulfides, arsenic sulfides, copper sulfides, antimony sulfides, tellurides, elemental sulfur, or any mixture thereof.
 
4. A process as claimed in any one of claims 1 to 3, wherein the gold content of the first type of refractory sulfidic mineral having high gold content is above 5 ppm, preferably above 8 ppm, more preferably between 10 to 100 ppm.
 
5. A process as claimed in any of the preceding claims, wherein the gold content of the second type of refractory sulfidic mineral having low gold content gold is below 5 ppm, preferably below 1 ppm, more preferably between 0 to 0.1 ppm.
 
6. A process as claimed in any one of claims 1 to 5, wherein the surface modifying chemical is selected from a group consisting of nitrogen, oxidizing agents, reducing agents, complexing agents and any mixtures thereof.
 
7. A process as claimed in claim 6, wherein the surface modifying chemical is an oxidizing agent.
 
8. A process as claimed in claim 7, wherein the oxidizing agent is selected from a group consisting of hydrogen peroxide, oxygen, ozone and alkali permanganate, chlorine, bromine, sulfuric acid, and any mixtures thereof.
 
9. A process as claimed in claim 6, wherein the surface modifying chemical is a reducing agent.
 
10. A process as claimed in claim 9, wherein said reducing agent is selected from a group consisting of hydrogen, carbon monoxide, sodium sulfide, sodium hydrosulfide, sodium dithionite, sulfur dioxide, ferrous sulfate, Fe powder, Zn powder, and any mixtures thereof.
 
11. A process as claimed in claim 6, wherein the surface modifying chemical is a complexing agent.
 
12. A process as claimed in claim 11, wherein said complexing agent is selected from a group consisting of ethylenediaminetetra-acetic acid (EDTA), diethylenetriamine (DETA), alkali cyanide, ammonia, alkali chloride, and any mixtures thereof.
 
13. A process as claimed in any one of claims 1 to 12, wherein the amount of the surface modifying chemical is 50 to 500 g/t of treated ore.
 
14. A process as claimed in any one of claims 1 to 13, wherein the gold containing raw material comprises silicates in addition to gold bearing minerals and these silicates are removed from the mineral pulp prior to pressure oxidation phase.
 
15. A process as claimed in claim 14, wherein the silicates are removed subsequent to the selective mineral flotation phase (d) before it is subjected to pressure oxidation phase, preferably by silicate flotation.
 
16. A process as claimed in claim 14, wherein the silicates are removed prior to conditioning phase (c) and the selective mineral flotation phase (d) from the mineral pulp, preferably by bulk sulfide flotation.
 


Ansprüche

1. Verfahren zur Rückgewinnung von Gold aus Goldenthaltenden Rohstoffen, umfassend refraktäre Gold-enthaltende Mineralien, insbesondere Gold-enthaltende refraktäre sulfidische Mineralien, umfassend

(a) Gewinnen von Gold-enthaltendem Rohstoff, der refraktäre Gold-enthaltende sulfidische Mineralien umfasst, die eine erste Art von refraktärem sulfidischem Mineral mit hohem Gold-Gehalt und eine zweite Art von sulfidischem Mineral mit niedrigem Gold-Gehalt umfassen, wobei die erste Art und die zweite Art von sulfidischen Mineralien innerhalb einer einzigen Spezies von refraktären sulfidischen Mineralien einzustufen sind;

(b) Bilden eines Erzschlamms, umfassend eine erste Art von refraktären sulfidischen Mineralteilchen mit hohem Gold-Gehalt und eine zweite Art von sulfidischen Mineralteilchen mit niedrigem Gold-Gehalt durch Suspendieren von gemahlenem Gold-enthaltendem Material in Wasser und gegebenenfalls weiteres Mahlen des Materials;

(c) Konditionieren des Erzschlamms durch Zugabe einer Oberflächen-modifizierenden Chemikalie zum Modifizieren der Oberfläche der ersten Art von refraktären sulfidischen Mineralteilchen mit hohem Gehalt, wodurch die Teilchen nicht schwimmfähig werden, um einen konditionierten Schlamm zu erhalten;

(d) Unterziehen des konditionierten Schlamms einem Schaum-Flotationsverfahren, um die erste Art von refraktären sulfidischen Mineralteilchen mit hohem Gold-Gehalt von der zweiten Art von sulfidischen Mineralteilchen mit niedrigem Gold-Gehalt zu trennen;

(e) Rückgewinnung der nicht schwimmfähigen ersten Art von refraktären sulfidischen Mineralteilchen mit hohem Gold-Gehalt als Flotationsrückstände;

(f) Druckoxidation (POX) der in Schritt (e) rückgewonnenen Flotationsrückstände, um eine Austragsschlämme zu gewinnen, die freigesetztes Gold umfasst; und

(g) Rückgewinnung von Gold aus der in Schritt (f) erhaltenen Austragsschlämme.


 
2. Verfahren nach Anspruch 1, wobei das Gold-enthaltende Material, das refraktäre Gold-enthaltende Mineralien umfasst, eine Goldrückgewinnungsrate von weniger als 80 % aufweist, wenn es einer direkten Cyanidierung unterzogen wird.
 
3. Verfahren nach Anspruch 1, wobei das refraktäre Gold-enthaltende Material Gold-blockierende oder Cyanidverbrauchende Materialien umfasst, insbesondere sulfidische Mineralien, wie Eisensulfide, Arsensulfide, Kupfersulfide, Antimonsulfide, Telluride, elementaren Schwefel oder ein beliebiges Gemisch davon.
 
4. Verfahren nach einem der Ansprüche 1 bis 3, wobei der Gold-Gehalt der ersten Art von refraktärem sulfidischem Mineral mit hohem Gold-Gehalt über 5 ppm, vorzugsweise über 8 ppm, bevorzugter zwischen 10 und 100 ppm liegt.
 
5. Verfahren nach einem der vorangehenden Ansprüche, wobei der Gold-Gehalt der zweiten Art von refraktärem sulfidischem Mineral mit niedrigem Gold-Gehalt unter 5 ppm, vorzugsweise unter 1 ppm, bevorzugter zwischen 0 bis 0,1 ppm liegt.
 
6. Verfahren nach einem der Ansprüche 1 bis 5, wobei die Oberflächen-modifizierende Chemikalie ausgewählt ist aus einer Gruppe, bestehend aus Stickstoff, Oxidationsmitteln, Reduktionsmitteln, Komplexbildnern und beliebigen Gemischen davon.
 
7. Verfahren nach Anspruch 6, wobei die Oberflächen-modifizierende Chemikalie ein Oxidationsmittel ist.
 
8. Verfahren nach Anspruch 7, wobei das Oxidationsmittel ausgewählt ist aus einer Gruppe, bestehend aus Wasserstoffperoxid, Sauerstoff, Ozon und Alkalipermanganat, Chlor, Brom, Schwefelsäure und beliebigen Gemischen davon.
 
9. Verfahren nach Anspruch 6, wobei die Oberflächen-modifizierende Chemikalie ein Reduktionsmittel ist.
 
10. Verfahren nach Anspruch 9, wobei das Reduktionsmittel ausgewählt ist aus einer Gruppe, bestehend aus Wasserstoff, Kohlenmonoxid, Natriumsulfid, Natriumhydrogensulfid, Natriumdithionit, Schwefeldioxid, Eisen-(II)-sulfat, Fe-Pulver, Zn-Pulver und beliebigen Gemischen davon.
 
11. Verfahren nach Anspruch 6, wobei die Oberflächen-modifizierende Chemikalie ein Komplexbildner ist.
 
12. Verfahren nach Anspruch 11, wobei der Komplexbildner ausgewählt ist aus einer Gruppe, bestehend aus Ethylendiamintetraessigsäure (EDTA), Diethylentriamin (DETA), Alkalicyanid, Ammoniak, Alkalichlorid und beliebigen Gemischen davon.
 
13. Verfahren nach einem der Ansprüche 1 bis 12, wobei die Menge der Oberflächen-modifizierenden Chemikalie 50 bis 500 g/t behandeltes Erz beträgt.
 
14. Verfahren nach einem der Ansprüche 1 bis 13, wobei der Gold-enthaltende Rohstoff neben Gold-tragenden Mineralien Silikate umfasst und diese Silikate vor der Druckoxidationsphase aus dem Erzschlamm entfernt werden.
 
15. Verfahren nach Anspruch 14, wobei die Silikate nach der selektiven mineralischen Flotationsphase (d) entfernt werden, vorzugsweise durch Silikat-Flotation, bevor sie einer Druckoxidationsphase unterzogen werden.
 
16. Verfahren nach Anspruch 14, wobei die Silikate vor der Konditionierungsphase (c) und der selektiven mineralischen Flotationsphase (d), vorzugsweise durch Massensulfid-Flotation, aus dem Erzschlamm entfernt werden.
 


Revendications

1. Procédé permettant de récupérer de l'or à partir de matières premières aurifères comprenant des minéraux aurifères réfractaires, en particulier des minéraux sulfurés réfractaires aurifères, comprenant

a) l'obtention d'une matière première aurifère comprenant des minéraux sulfurés aurifères réfractaires comprenant un premier type de minéral sulfuré réfractaire à forte teneur en or et un second type de minéral sulfuré à faible teneur en or, ledit premier type et ledit second type de minéraux sulfurés étant à classer sous une seule espèce de minéraux sulfurés réfractaires ;

b) la formation d'une pulpe minérale comprenant un premier type de particules minérales sulfurées réfractaires à forte teneur en or et un second type de particules minérales sulfurées à faible teneur en or, par mise en suspension d'un matériau aurifère moulu dans de l'eau et éventuellement par un broyage supplémentaire du matériau ;

c) le conditionnement de la pulpe minérale par adjonction d'une substance chimique de modification de surface destinée à modifier la surface du premier type de particules minérales sulfurées réfractaires à forte teneur, rendant ainsi lesdites particules non flottantes pour obtenir une pulpe conditionnée ;

d) l'application à la pulpe conditionnée d'un procédé de flottation par moussage permettant de séparer le premier type de particules minérales sulfurées réfractaires à forte teneur en or du second type de particules minérales sulfurées à faible teneur en or ;

e) la récupération du premier type de particules minérales sulfurées réfractaires non flottantes à forte teneur en or en tant que résidus de flottation ;

f) l'oxydation sous pression (POX) des résidus de flottation récupérés à l'étape e) pour obtenir une bouillie de décharge comprenant de l'or libéré ; et

g) la récupération d'or à partir de la bouillie de décharge obtenue à l'étape f).


 
2. Procédé selon la revendication 1, dans lequel le matériau aurifère comprenant des minéraux aurifères réfractaires présente un taux de récupération d'or inférieur à 80 % lorsqu'il est soumis à une cyanuration directe.
 
3. Procédé selon la revendication 1, dans lequel le matériau aurifère réfractaire comprend des matériaux emprisonnant de l'or ou consommant du cyanure, particulièrement des minéraux sulfurés tels que sulfures de fer, sulfures d'arsenic, sulfures de cuivre, sulfures d'antimoine, tellurures, soufre élémentaire ou un quelconque mélange de ceux-ci.
 
4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel la teneur en or du premier type de minéral sulfuré réfractaire à forte teneur en or est supérieure à 5 ppm, préférablement supérieure à 8 ppm, plus préférablement comprise dans une plage de 10 à 100 ppm.
 
5. Procédé selon l'une quelconque des revendications précédentes, dans lequel la teneur en or du second type de minéral sulfuré réfractaire à faible teneur en or est inférieure à 5 ppm, préférablement inférieure à 1 ppm, plus préférablement comprise entre 0 et 0,1 ppm.
 
6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel la substance chimique de modification de surface est choisie dans un groupe constitué de l'azote, des agents oxydants, des agents réducteurs, des agents complexants et de mélanges quelconques de ceux-ci.
 
7. Procédé selon la revendication 6, dans lequel la substance chimique de modification de surface est un agent oxydant.
 
8. Procédé selon la revendication 7, dans lequel l'agent oxydant est choisi dans un groupe constitué du peroxyde d'hydrogène, de l'oxygène, de l'ozone et d'un permanganate alcalin, du chlore, du brome, de l'acide sulfurique et de mélanges quelconques de ceux-ci.
 
9. Procédé selon la revendication 6, dans lequel la substance chimique de modification de surface est un agent réducteur.
 
10. Procédé selon la revendication 9, dans lequel ledit agent réducteur est choisi dans un groupe constitué de l'hydrogène, du monoxyde de carbone, du sulfure de sodium, de l'hydrogénosulfure de sodium, du dithionite de sodium, du dioxyde de soufre, du sulfate ferreux, de la poudre Fe, de la poudre de Zn et de mélanges quelconques de ceux-ci.
 
11. Procédé selon la revendication 6, dans lequel la substance chimique de modification de surface est un agent complexant.
 
12. Procédé selon la revendication 11, dans lequel ledit agent complexant est choisi dans un groupe constitué de l'acide éthylène diamine tétra-acétique (EDTA), de la diéthylènetriamine (DETA), d'un cyanure alcalin, de l'ammoniaque, d'un chlorure alcalin et de mélanges quelconques de ceux-ci.
 
13. Procédé selon l'une quelconque des revendications 1 à 12, dans lequel la quantité de substance chimique de modification de surface va de 50 à 500 g/t de minerai traité.
 
14. Procédé selon l'une quelconque des revendications 1 à 13, dans lequel la matière première aurifère comprend des silicates en plus des minéraux aurifères et ces silicates sont éliminés de la pulpe minérale avant la phase d'oxydation sous pression.
 
15. Procédé selon la revendication 14, dans lequel les silicates sont éliminés à la suite de la phase de flottation sélective des minéraux d) et avant que la pulpe soit soumise à la phase d'oxydation sous pression, préférablement par flottation des silicates.
 
16. Procédé selon la revendication 14, dans lequel les silicates sont éliminés de la pulpe minérale avant la phase de conditionnement c) et la phase de flottation sélective des minéraux d), préférablement par flottation globale des sulfures.
 




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Cited references

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