Kullan talteenotto malmeista uutta ja ikivanhaa Leppinen.pdf · 1904 Merrill introduces zinc dust for gold precipitation 1906 Crowe applies vacuum deareation to zinc precipitation

Kullan talteenotto malmeista – uutta ja ikivanhaa Jaakko Leppinen

Rikastustekniikan seminaari, Oulu 23-24.8.2016

•© Outotec – All rights reserved

World gold production in 2012

•Rikastustekniikan seminaari 2016 •2

Europe

Finland 10,800

Sweden 6,000

Spain 3,600

Serbia 0,900

Greece 0,800

Romania 0,600

Poland 0,500

Slovakia 0,300

Denmark 0,100


Gold production routes


Hydrometallurgical processing of gold

ores and concentrates is currently

dominated by cyanide leaching and

around 60% of all gold is produced

using cyanide.

Hydro

metallurgy Smelting

Artisanal mining

Amalgamization


Artisanal gold mining

• 10 to 15 million artisanal miners

producing around 380-450 tonnes

Au/a in more than 70 countries

• About 100 million people – workers

and their families - depend on

artisanal mining compared to about

7 million people worldwide in

industrial mining

• These gold mining operations are

particularly dangerous, as they

often use the mercury

amalgamation process to extract

gold from ores.

• •



Gold production in the past


Gold washing Wash table Manual grinding

Smelting


Gold production today

•6 •Rikastustekniikan seminaari 2016


Developments in gold ore processing

• Gold collected from stream beds (8000 BC)

• Washing of alluvial gold (before 3500 BC)

• Mining of gold (3500 BC)

• Smelting (3000 BC)

• Cupellation to separate other metals from gold-silver alloys (2000 BC)

• Parting to separate silver from gold (600 BC)

• Amalgamization (100 BC)

• Leaching with aqua regia (700 AC)

• Leaching with chloride (1850 AC)

• Cyanidation (1890)

• Flotation process 1905

• Refractory ore treatment with pressure oxidation (1985)

• Refractory ore treatment with bio-oxidation (1986)

• Use of alternative lixiviants for gold leaching (2000-)

• Sensor based ore sorting for gold ores (2000-)


High-temperature techniques Gravity separation techniques

Amalgamization

Leaching

Sensor based

ore sorting

Cyanidation

Hydrometallurgical

treatment of refractory ores

Flotation

Alternative

gold lixiviants


Mineralogical considerations for gold ore types

•Rikastustekniikan seminaari 2016

LIBERATED GOLD

COMPOSITE GRAIN

LOCKED PARTICLEIN SILICATE

LOCKED PARTICLEIN SULFIDE

INVISIBLE GOLD IN SULFIDE

FINE INCLUSIONS IN SULFIDE

FREE-MILLING GOLD ORE REFRACTORY GOLD ORE

Leaching?

Flotation?

Fine grinding?

Gravity separation?

Leaching?

Flotation?

Fine grinding?

Gravity separation?

Decompostion of gold bearing minerals?

•8


Process options for gold processing


•9

Flotation

Gold concentrate to

smelter or leaching

Crushing Grinding

Crushing Grinding

Agitated Cyanide

Leaching Flotation Pre-oxidation Gold

Crushing Grinding

Flotation

Gold

Agitated Cyanide

Leaching

Free

Milling Au

Ore

Refractory

Au Ore

Gravity

concentrate

Heap Leaching

Gold


Mineral Processing Plant

Crushing Grinding Flotation

Ta

il

in

g

Concentrate

Sorting

ORE

Thickening

Filtration

Concentrate

Tailing

Classification

Paste

thickening

Thickening Filtration


Gravity separation

Gravity concentrate

•10

CRUSHING

GRINDING

FLOTATION

THICKENING

FILTRATION

TAILINGS

TREATMENT


Mineral Processing Plant

Crushing Grinding Flotation

Ta

il

in

g

Concentrate

Sorting

ORE

Thickening

Filtration

Concentrate

Tailing

Classification

Paste

thickening

Thickening Filtration


Gravity separation

Gravity concentrate

•11


Size range applicability of gravity separation equipment



Shaking table



Main Applications of Flotation in Gold Processing


1. Flotation of free gold and gold-bearing sulfide minerals to produce a gold-

rich concentrate. The concentrate can be treated by:

o Cyanidation

o Regrinding and cyanidation

o Intensive cyanidation,

o Oxidative pretreatment and cyanidation

o Direct smelting

2. Flotation of carbonaceous material, carbonates, or other material that

would otherwise interfere with processing

•14


Cyanidation process for gold


Crushing

Grinding

Cyanide leaching

Gold ore

Comminution

Leaching

Recovery

Sorption in activated

carbon

Elution from

activated carbon

Electrowinning

Smelting

Gold

Zinc cementation

Merrill-Crowe

S

L


Carbon-in-pulp (CIP) process


ELUTION

REGENERATION

TAILING

ACTIVATED CARBON

ORE FROM

GRINDING

LOADED CARBON

BARREN CARBON

ELECTROWINNING

CYANIDE LEACHING CARBON ADSOPTION

slurry


Cyanidation process routes for gold


Crushing

Grinding

Cyanide leaching

Zinc cementation

(Merrill-Crowe)

Carbon in Pulp

CIP

Carbon in Leach

CIL Carbon in Column

CIC

Solid-liquid separation

Gold ore

Gold is

precipitated from

cyanide solution

using zinc powder

Gold adsorbed on

activated carbon

from cyanide

solution (CIC)

Gold adsorbed on

activated carbon

from cyanide

solution with

solids. Adsorption

take place in a

separate stage

(CIP)

Gold adsorbed on

activated carbon in

slurry cyanide

solution with

solids. Adsoprtion

takes place

simultaneously

with leaching (CIL)

Comminution

Leaching

Recovery

Heap leaching

Heap leaching


Cyanidation process for gold

Rikastustekniikan seminaari 2016 •18

Cyanide leaching

Gold ore

Sorption in activated

carbon

Elution from

activated carbon

Electrowinning

Smelting

Gold

Carbon

Refining

Tailings

1-10 g/t

Solution 1-5 mg/l

5-10 kg/t

100-1000

mg/l

70-80%

99.99%

0.1-1 g/t

Au in ore

Au in solution

Au in carbon Dore bars

Gold bullion


Cyanidation process

Some milestones:

1867 First patent on cyanide leaching

1889 First cyanidation plant : Crown Mine in New Zealand

1890 First cyanidation plant in South Africa: Robinson Deep

1891 First cyanidation plant in USA: Mercur, Utah

1894 Johnson patents charcoal adsorption from cyanide solutions

1904 Merrill introduces zinc dust for gold precipitation

1906 Crowe applies vacuum deareation to zinc precipitation

1949 First CIP plant at San Andreas in Honduras

1951 CIP process patented by McQuiston and Chapman

1952 USBM develops carbon elution process (Zadra)

1970 First cyanide heap leach operation in Carlin, Nevada

1973 AARL elution process

1985 First pressure oxidation plant at Homestake McLaughlin (USA)

1986 Start-up of cencentrate biological oxidation plant in Fairview,

South Africa


First commecial scale plant

Zinc cementation for gold

recovery from solution

Carbon in pulp CIP

New elution methods from

activated carbon

Heap leaching of gold

Pre-treatment methods

for refractory gold


Treatment of gold concentrates in copper smelters


Electro

refining Copper

cathodes

Anode

slime

Anode

slime

treatment

Gold

Palladium

Platinum


Treatment of gold concentrates in copper smelters


Electro

refining Copper

cathodes

Anode

slime

Anode

slime

treatment

Gold

Palladium

Platinum




Hand sorting in 1556



Sorting of vein-type gold ore


Laser image Sorting image Photo

•24


Preconcentration of material – Sensor Based Ore sorting


•1

•2

•3

•4

• Feeding of unsorted material

• NIR sensor

• Color sensor

• Separation chamber

•1

•2

•3

•4

• Suitable particle size 10-250 mm

• Depending on ore characteristics

10 to 70 % of material can be

rejected

• Capacities capable of meeting the

needs of many concentrators (upto

500 tph per unit)

• Today - mature technology

• Good understanding of mineralogy

and ore geology is required

• The most common sensors:

optical and X-ray transmission

(XRT) ..\..\..\TOMRA\CommodasUltrasort_QUARZITE.mov

•25

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Refractory gold ore


INVISIBLE GOLD IN SULFIDE

FINE INCLUSIONS IN SULFIDE

•27



CONCENTRATION

FINE GRINDING PRESSURE

OXIDATION BIO OXIDATION ROASTING

CHEMICAL

OXIDATION

CYANIDATION

GOLD ORE

GOLD

Process options for refractory gold ores


Occurence of gold in recractory ores, examples


Ccp Sp Gn Bou Apy Py Total

% % % % % % %

Conc A 0.17 < 0.1 < 0.1 0.02 9.05 65.28 74.53

Conc B 2.47 1.58 0.54 0.31 15.60 63.48 83.98

Ccp = chalcopyrite (CuFeS2)

Sp = sphalerite (ZnS)

Gn = galena (PbS)

Bou = bournonite (PbCuSbS3)

Apy = arsenopyrite (FeAsS)

Py = pyrite (FeS2)

Mineral composition in concentrates

Distribution of gold between minerals


Chemical reactions in pressure oxidation

Autoclave

2FeS2 + O2 + 2H2O 2FeSO4 + 2H2SO4

4FeSO4 + O2 + 2H2SO4 Fe2(SO4)3 + 2H2O

2FeAsS + 7O2 + 2H2O + H2SO4 2H3AsO4 + Fe2(SO4)3

4CuFeS2 + 17O2 + 2H2SO4 4CuSO4 + Fe2(SO4)3 + 2H2O


Decomposition of sulfide

minerals through

oxidation

http://www.google.fi/url?sa=i&rct=j&q=chemical+reaction+symbols&source=images&cd=&cad=rja&docid=rJLmeqQoi1hkmM&tbnid=MgOxv0dNuyx-3M:&ved=0CAUQjRw&url=http://www.revisescience.co.uk/2010/schools/stedwards/acreversible.asp&ei=Lr5_UamjI4nZsgapz4CQDw&bvm=bv.45921128,d.Yms&psig=AFQjCNGNnTIDTjqMpKA--H0jqb12sSHo_Q&ust=1367412652070583





Five-compartment autoclave



Alternative lixiviants for gold

Thiosulfate

Barrick Gold introduced thiosulfate leaching circuit that achieved commercial production in Q3

2015 and is expected to complete its ramp up by Q3 2016. Barrick Gold’s Goldstrike mine will be

the largest scale use of the alternative lixiviant the world has ever seen.

Thiourea

Has been used to treat antimony –rich concentrate in Australia. No large scale operations so far.

Thiocyanate

Acidic thiocyanate has been investigated by Newmont Gold

Chloride

Outotec is developing it own non-cyanide technology basing on chloride leaching and solvent

extraction. No full-scale operations so far.



Barrick Gold Goldstrike operation with thiosulfate leaching



General diagram for Outotec chloride leaching process

Leaching S/L

S/L

S/L

S/L

S/L

Au extraction

Ag extraction

Au stripping

Ag stripping

Ag cementation

Au reducing

Effluent treatment

Effluent treatment

Evaporation

Cu-Zn precipitate

Solution bleed

Cu-powder

Au -product

Ag -product

Steam

Hydroxide precipitate

Au -concentrate

Oxygen Reductant

Leach residue

•36 •Rikastustekniikan seminaari 2016


Conclusions

• History of gold processing is long, extending back thousands of years

• Minerals processing, hydrometallurgical and pyrometallurgical

techniques are commonly used for gold recovery

• Hydrometallurgical methods play the predominant role in gold

processing

• Currently main new developments are ore sorting and alternative

lixiviants for cyanide

• In addition to conventional mineral processing engineering students

should acquire basic knowledge of gold hydrometallurgy


Documents

Kullan talteenotto malmeista uutta ja ikivanhaa Leppinen.pdf · 1904 Merrill introduces zinc dust for gold precipitation 1906 Crowe applies vacuum deareation to zinc precipitation