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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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
ALS® + AQUA REGIAACID PARTING + ELECTROLYSIS
ITEMACID PARTING + EGR
to obtain Au9999ALS® + AQUA REGIA
to obtain Au9999
Operator hours 61 38,5
Fume Extraction 3 x Critical 1 x Critical
Chlorine - -
HCl 440kg 340kg
HNO3 780kg 220kg
Fe Powder 200kg -
Na₂O₅S₂ - 180kg
Process Water 3800 litres 3100 litres
Power (kW/Hr) 4000 3620
Refractory Usage 55% 100%
Consumables 100% 67%
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
Fume Extraction Critical Critical Critical - Critical
Chlorine - - - - -
HCl - 240kg 200kg - 340kg
HNO3 730kg - 50kg - 220kg
Fe Powder - 200kg - - -
Na₂O₅S₂ - - - - 180kg
Process Water 1,400 litres 800 litres 1600 litres - 3,100 litres
Power (kW/Hr) 1420 940 1640 1860 1760
Refractory Usage 41% 22% 14% 100% 24%
Consumables 73% 64% 73% 41% 100%
Effluent 1,300 litres 1,100 litres 600 litres - 1,900 litres
Estimate unrecoverable Gold
losses0,015% - 0,01% 0,001% 0,01%
Au
50
-Ag4
0-C
u10
50
0Kg
per
day
O
utp
ut:
Au
99
99
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
ALS® + AQUA REGIAACID PARTING + ELECTROLYSIS
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)
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
ALS does not generate scrubber wastes or liquid effluent
ALS does not require the use of hazardous process chemicals
Overall water usage and liquid waste is significantly lower
Overall power consumption reduced by 10%
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
CHLORINATION + ELECTROLYSIS ALS® + AQUA REGIA TYPICAL PROCESS REQUIREMENTS
ITEM CHLORINATIONSODA
REDUCTIONELECTROLYSIS ALS AQUA REGIA
Operator hours 2 2 16 3 16
Fume Extraction Critical Critical Critical - Critical
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
Refractory Usage 78% 100% 56% 56% 100%
Consumables 11% 11% 89% 22% 100%
Effluent - - 300 litres - 1,100 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 20 19
Fume Extraction 3 x Critical 1 x Critical
Chlorine 22kg -
HCl 50kg 70kg
HNO3 - 30kg
Fe Powder - -
Na₂O₅S₂ - 50kg
Water Usage 300 litres 950 litres
Power (kW/Hr) 1460 1400
Refractory Usage 100% 67%
Consumables 91% 100%
Effluents 300 litres 1100 litres
Estimate unrecoverable Gold
losses0,06% 0,011%
Au
70
-Ag1
5-C
u15
10
0Kg
per
day
O
utp
ut:
Au
99
99
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
CHLORINATION + ELECTROLYSIS ALS® + AQUA REGIA
Au
70
-Ag1
5-C
u15
10
0Kg
per
day
O
utp
ut:
Au
99
99 COMPARISON HIGHLIGHTS
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
Effluents reduced by 75%
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
Overall power consumption reduced by 4%
Inventory tracking and control is easier
ALS does not generate scrubber wastes or liquid effluent
ALS does not require the use of hazardous process chemicals
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
ALS® + AQUA REGIAACID PARTING + ELECTROLYSIS TYPICAL PROCESS REQUIREMENTS
ITEM ACID PARTINGSILVER
RECOVERYELECTROLYSIS ALS AQUA REGIA
Operator hours 13 10 16 3 16
Fume Extraction Critical Critical Critical - Critical
Chlorine - - - -
HCl - 90kg 50kg - 70kg
HNO3 290kg - - - 30kg
Fe Powder - 55kg - - -
Na₂O₅S₂ - - - - 50
Process Water 900 litres 450 litres 300 litres - 950 litres
Power (kW/Hr) 700 400 900 380 1020
Refractory Usage 80% 40% 100% 100% 100%
Consumables 81% 56% 100% 13% 100%
Effluent 1,200 litres 600 litres 300 litres - 1,100 litres
Estimate unrecoverable Gold
losses0,015% 0,000% 0,01% 0,001% 0,01%
ITEMACID PARTING + EGR
to obtain Au9999ALS + AQUA REGIA to obtain Au9999
Operator hours 39 19
Fume Extraction 3 x Critical 1 x Critical
Chlorine - -
HCl 140kg 70kg
HNO3 290kg 30kg
Fe Powder 55kg -
Na₂O₅S₂ - 50kg
Water Usage 1650 litres 950 litres
Power (kW/Hr) 2000 1400
Refractory Usage 100% 91%
Consumables 100% 48%
Effluents 2100 litres 1100 litres
Estimate unrecoverable Gold
losses0,025% 0,011%
Au
70
-Ag1
5-C
u15
10
0Kg
per
day
O
utp
ut:
Au
99
99
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
ALS® + AQUA REGIAACID PARTING + ELECTROLYSIS
Au
70
-Ag1
5-C
u15
10
0Kg
per
day
O
utp
ut:
Au
99
99 COMPARISON HIGHLIGHTS
ADVANTAGES OF ALS + AQUA REGIA (70/15/15 - 100kg)
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
Effluents reduced by 50%
Operating hours reduced by 50%. Overall turnaround time twice as fast
Silver chloride generated is 260kg compared to 4kg
Overall power consumption reduced by 30%
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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
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
Estimate unrecoverable Gold
losses0,025% 0,001% 0,01%
ITEMAQUA REGIA + AQUA REGIA
to obtain Au9999ALS + AQUA REGIA to obtain Au9999
Operator hours 26 19
Fume Extraction 1 x Critical 1 x Critical
Chlorine - -
HCl 110kg 70kg
HNO3 60kg 30kg
Fe Powder - -
Na₂O₅S₂ - 50kg
Water Usage 1700 litres 950 litres
Power (kW/Hr) 1840 1400
Refractory Usage 50% 100%
Consumables 100% 79%
Effluents 1500 litres 1100 litres
Estimate unrecoverable Gold
losses0,025% 0,011%A
u7
0-A
g15
-Cu
151
00
Kg p
er d
ay
Ou
tpu
t: A
u9
999
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
ALS® + AQUA REGIAAQUA REGIA + AQUA REGIA
Au
70
-Ag1
5-C
u15
10
0Kg
per
day
O
utp
ut:
Au
99
99 COMPARISON HIGHLIGHTS
ADVANTAGES OF ALS + AQUA REGIA (70/15/15 - 100kg)
Overall chemical usage reduced by 40%
Estimate unrecoverable Gold losses are 0,011% (2,5 time less)
Water usage is approximately halved
Effluents reduced by 30%
Operating hours reduced by 25%
Overall power consumption reduced by 24%
ALS operating cost is very low in comparison to other processes
Less process steps
Less fumes produced
Less labour required
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
ACID PARTING + ELECTROLYSIS TYPICAL PROCESS REQUIREMENTS
ITEM ACID PARTINGSILVER
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 -
Estimate unrecoverable Gold
losses0,015% 0,000% 0,01% 0,001% 0,01%
ITEMACID PARTING + EGR
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
Estimate unrecoverable Gold
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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
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
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining
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 control is easier
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 control is easier
Metal loss is reduced
LBMA Assaying and Refining Conference 2019The Use of Acidless Separation Technology in Precious Metal Refining