the use of acidless separation technology in precious ... 2019/7. general... · aqua regia + aqua...

The Use of Acidless Separation Technology in Precious

Metal Refining

Authors:Giovanni FaoroKarl RedlichManuel Boscato

ALS technologies has beenintroduced 4 years ago after

the period of Research & Development.

The technology is now usedin many refineries as an

integral part of traditionalrefining processes.

We have now a significantamount of data about

performance and capabilities on different substrates.

LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining

Refining processes:1. Chlorination + Electrolysis2. Acid Parting + Electrolysis3. Aqua Regia+Aqua Regia

3. ALS + Aqua regia

Feedstock composition:Alloy #1:Au50-Ag40-Cu10Alloy #2:Au70-Ag15-Cu15

Ag Au

Base Metals

Refining AuProcess of finishing

Refining Ag Process of finishing

Alloy#1Alloy#2

ALS


Quantitative Criteria :- Mass Balance

- Energy consumption- Labour time

- Unrecoverable metal loss

Qualitative Criteria :- Process simplicity

- Ease of metal control/inventory- By-products with PM content

considerationsTo other processesTo final products

PROCESS

PM Wastewater By-products

Power

Labour

Feedstock Chemicals

Unrecoverableloss

PM Recovery


TYPICAL PROCESS REQUIREMENTS

ITEM CHLORINATIONCHLORIDE

REDUCTIONELECTROLYSIS ALS® AQUA REGIA

Operator hours 8 13 26 12 26,5

Fume Extraction Critical Critical Critical - Critical

Chlorine 130kg - - - -

HCl - 30kg 200kg - 340kg

HNO3 - - - - 220kg

Fe Powder - 60kg - - -

Na₂O₅S₂ - - - - 180kg

Process Water - 1,800 litres 1,600 litres - 3,100 litres

Power (kW/Hr) 1680 920 1640 1860 1760

Refractory Usage 100% 19% 9% 70% 17%

Consumables 27% 64% 73% 41% 100%

Effluents - 1,700 litres 600 litres - 1,900 litres

Estimate unrecoverable

Gold losses0,04% 0,01% 0,01% 0,001% 0,01%

ITEMCHLORINATION + EGR

to obtain Au9999ALS® + AQUA REGIA

to obtain Au9999

Operator hours 47 38,5

Fume Extraction 3 x Critical 1 x Critical

Chlorine 130kg -

HCl 230kg 340kg

HNO3 - 220kg

Fe Powder 60kg -

Na₂O₅S₂ - 180kg

Water Usage 3400 litres 3100 litres

Power (kW/Hr) 4240 3620

Refractory Usage 100% 68%

Consumables 100% 86%

Effluents 2300 litres 1900 litres

Estimateunrecoverable

Gold losses0,06% 0,011%

Au

50

-Ag4

0-C

u10

50

0Kg

per

day

O

utp

ut:

Au

99

99CHLORINATION + ELECTROLYSIS ALS® + AQUA REGIA


CHLORINATION + ELECTROLYSIS ALS® + AQUA REGIA

Au

50

-Ag4

0-C

u10

50

0Kg

per

day

O

utp

ut:

Au

99

99 COMPARISON HIGHLIGHTS

ADVANTAGES OF ALS® + AQUA REGIA (50/40/10 - 500kg)

Estimate unrecoverable Gold losses are 0,011% (6 times less)

Chlorine gas usage is eliminated, then also the related safety and management costs

Chloride slag by-product to be recovered is 14kg compared to approximately 370 kg

Approximately 20% reduction in overall operating hours

Metallic by-product from the ALS is fed directly into Aqua Regia and Electrolytic Silver

Overall power consumption reduced by 15%

Fewer process steps

ALS does not require fume scrubbing as no fumes are generated

ALS does not generate scrubber wastes or liquid effluent

ALS does not require the use of hazardous process chemicals


ALS® + AQUA REGIAACID PARTING + ELECTROLYSIS

ITEMACID PARTING + EGR

to obtain Au9999ALS® + AQUA REGIA

to obtain Au9999

Operator hours 61 38,5


Chlorine - -

HCl 440kg 340kg

HNO3 780kg 220kg

Fe Powder 200kg -


Process Water 3800 litres 3100 litres

Power (kW/Hr) 4000 3620



Effluent 3000 litres 1900 litres

Estimate unrecoverable Gold

losses0,025% 0,011%

TYPICAL PROCESS REQUIREMENTS

ITEM ACID PARTINGSILVER

RECOVERYELECTROLYSIS ALS® AQUA REGIA

Operator hours 18 17 26 12 26,5


Chlorine - - - - -

HCl - 240kg 200kg - 340kg

HNO3 730kg - 50kg - 220kg


Na₂O₅S₂ - - - - 180kg

Process Water 1,400 litres 800 litres 1600 litres - 3,100 litres

Power (kW/Hr) 1420 940 1640 1860 1760


Consumables 73% 64% 73% 41% 100%

Effluent 1,300 litres 1,100 litres 600 litres - 1,900 litres


losses0,015% - 0,01% 0,001% 0,01%

Au

50

-Ag4

0-C

u10

50

0Kg

per

day

O

utp

ut:

Au

99

99



Au

50

-Ag4

0-C

u10

50

0Kg

per

day

O

utp

ut:

Au

99


ADVANTAGES OF ALS® + AQUA REGIA (50/40/10 - 500kg)

Acid Parting requires a high quantity of added silver (500kg), ALS no need any

Silver chloride generated by Acid Parting is 940kg compared to 14kg with ALS®

Effluents reduced by 40%

Estimate unrecoverable Gold losses are 0,011% (2,5 times less)

Metallic by-product from the ALS is fed directly into Aqua Regia and Electrolytic Silver

Operating hours reduced by 33%. Overall turnaround time is much quicker

ALS avoids the high chemical usage and costs associated with Acid Parting

ALS does not require fume scrubbing as no fumes are generated



Overall water usage and liquid waste is significantly lower



CHLORINATION + ELECTROLYSIS ALS® + AQUA REGIA TYPICAL PROCESS REQUIREMENTS

ITEM CHLORINATIONSODA

REDUCTIONELECTROLYSIS ALS AQUA REGIA

Operator hours 2 2 16 3 16


Chlorine 22kg - - - -

HCl - - 50kg - 70kg

HNO3 - - - - 30kg

Fe Powder - - - - -

Na₂O₅S₂ - - - - 50

Process Water - - 300 litres - 950 litres

Power (kW/Hr) 280 280 900 380 1020


Consumables 11% 11% 89% 22% 100%

Effluent - - 300 litres - 1,100 litres


losses0,04% 0,01% 0,01% 0,001% 0,01%

ITEMCHLORINATION + EGR

to obtain Au9999ALS + AQUA REGIA to obtain Au9999

Operator hours 20 19


Chlorine 22kg -

HCl 50kg 70kg

HNO3 - 30kg

Fe Powder - -



Power (kW/Hr) 1460 1400





losses0,06% 0,011%

Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99

99


CHLORINATION + ELECTROLYSIS ALS® + AQUA REGIA

Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99


ADVANTAGES OF ALS + AQUA REGIA (70/15/15 - 100kg)

Estimate unrecoverable Gold losses are 0,011% (6 times less)

Chlorine gas usage is eliminated, then also the related safety and management costs


Chloride slag by-product to be recovered is very little compared to high volume produced with Chlorination

Gold is not tied up in electrolyte

Metallic by-product from the ALS is easily recovered


Inventory tracking and control is easier




ALS® + AQUA REGIAACID PARTING + ELECTROLYSIS TYPICAL PROCESS REQUIREMENTS


RECOVERYELECTROLYSIS ALS AQUA REGIA

Operator hours 13 10 16 3 16


Chlorine - - - -

HCl - 90kg 50kg - 70kg

HNO3 290kg - - - 30kg


Na₂O₅S₂ - - - - 50

Process Water 900 litres 450 litres 300 litres - 950 litres

Power (kW/Hr) 700 400 900 380 1020


Consumables 81% 56% 100% 13% 100%

Effluent 1,200 litres 600 litres 300 litres - 1,100 litres


losses0,015% 0,000% 0,01% 0,001% 0,01%





Chlorine - -

HCl 140kg 70kg

HNO3 290kg 30kg

Fe Powder 55kg -



Power (kW/Hr) 2000 1400





losses0,025% 0,011%

Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99

99



Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99



Acid Parting requires an addition of 180kg Silver, ALS no need any

Estimate unrecoverable Gold losses are 0,011% (2,5 time less)

Water usage is approximately halved


Operating hours reduced by 50%. Overall turnaround time twice as fast

Silver chloride generated is 260kg compared to 4kg


ALS operating cost is very low in comparison to other processes

Metallic by-product from the ALS is easily recovered

Less process steps

Inventory tracking and control is easier


ALS® + AQUA REGIAAQUA REGIA + AQUA REGIA TYPICAL PROCESS REQUIREMENTS

ITEMAQUA REGIA - DOUBLE

REFINEALS AQUA REGIA

Operator hours 26 3 16

Fume Extraction Critical - Critical

Chlorine - - -

HCl 110 - 70kg

HNO3 60kg - 30kg

Fe Powder - - -

Na₂O₅S₂ - - 50

Process Water 1700 litres - 950 litres

Power (kW/Hr) 1840 380 1020

Refractory Usage 100% 100% 100%

Consumables 100% 9% 70%

Effluent 1500 litres - 1,100 litres


losses0,025% 0,001% 0,01%

ITEMAQUA REGIA + AQUA REGIA




Chlorine - -

HCl 110kg 70kg

HNO3 60kg 30kg

Fe Powder - -



Power (kW/Hr) 1840 1400





losses0,025% 0,011%A

u7

0-A

g15

-Cu

151

00

Kg p

er d

ay

Ou

tpu

t: A

u9

999


ALS® + AQUA REGIAAQUA REGIA + AQUA REGIA

Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99



Overall chemical usage reduced by 40%

Estimate unrecoverable Gold losses are 0,011% (2,5 time less)

Water usage is approximately halved


Operating hours reduced by 25%


ALS operating cost is very low in comparison to other processes

Less process steps

Less fumes produced

Less labour required


ACID PARTING + ELECTROLYSIS TYPICAL PROCESS REQUIREMENTS


RECOVERYELECTROLYSIS ALS ELECTROLYSIS

Operator hours 13 10 16 3

Fume Extraction Critical Critical Critical -

Chlorine - - -

HCl - 90kg 50kg -

HNO3 290kg - - -

Fe Powder - 55kg - -

Na₂O₅S₂ - - - -

Process Water 900 litres 450 litres 300 litres -

Power (kW/Hr) 700 400 900 380

Refractory Usage 80% 40% 100% 100%

Consumables 81% 56% 100% 13%

Effluent 1,200 litres 600 litres 300 litres -


losses0,015% 0,000% 0,01% 0,001% 0,01%


to obtain Au9999ALS + ELECTROLYSIS

to obtain Au9999

Operator hours 39

Fume Extraction 3 x Critical

Chlorine -

HCl 140kg

HNO3 290kg

Fe Powder 55kg

Na₂O₅S₂ -

Water Usage 1650 litres

Power (kW/Hr) 2000

Refractory Usage 100%

Consumables 100%

Effluents 2100 litres


losses0,025% 0,011%

Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99

99

TO B

E C

OM

PLE

TED

TO B

E C

OM

PLE

TED

ALS® + ELECTROLYSIS


Au

70

-Ag1

5-C

u15

10

0Kg

per

day

O

utp

ut:

Au

99

99

ALS® + ELECTROLYSISACID PARTING + ELECTROLYSIS

COMPARISON HIGHLIGHTS

ADVANTAGES OF ALS + ELECTROLYSIS (70/15/15 - 100kg)

It is the “greenest” process of the ones analysed

It is desirable also when copper content is 30% or more

It is important that Ag content in the electrolysis is low and ALS can achieve that easily

Metal loss is reduced (total 0,01%)

Metal control is easier


CONCLUSIONSAlloy #1: Au50-Ag40-Cu10 Alloy #2: Au70-Ag15-Cu15

Significant advantages in all major aspectsconsidered

Reduction of by-products generated by the process


Metal loss is reduced

Similar consumption of resources (power, labour, water etc.) in case of Chlorination +

Electrolysis

Significant advantages in all major aspectswhen compared to Acid Parting + Electrolysis

or Aqua Regia + Aqua Regia


Metal loss is reduced


the use of acidless separation technology in precious ... 2019/7. general... · aqua regia + aqua...

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