774 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
As the above economic analysis shows, incorporation of
a thiocyanate EO circuit into the two mines being studied
returns a net positive result. The EO circuit incorporated
into the Mexican process within the SART plant shows a
simple payback of four years, which is within the current
LOM (based on current proven reserves). The facility in the
Abitibi region of Quebec, while still a net positive return,
did not show a payback within the site’s current LOM,
indicating the need to expand beyond the base economic
driver for this process implementation, and to look at addi-
tional benefits which the EO process would provide.
ASSESSMENT OF CONSTRAINTS AND
LIMITATIONS
While returning positive yearly returns, as the above discus-
sion has shown, the process is sensitive to many factors, and
each of these need to be taken into account for each process
solution, site, jurisdiction, etc. Some sensitivities, and site
specific considerations affecting the implementation of an
EO circuit are discussed below:
• IX: effect of residual SCN in recycled regenerant
The rich SCN regenerant solution which strips the
IX columns is sent to the electro oxidation circuit
to recover HCN from SCN. However, as SCN is
oxidized, the efficiency of the circuit is reduced. To
maintain a high EO current efficiency, a high SCN
concentration is beneficial – ie, it is beneficial for the
EO circuit to have a high recirculating load of SCN,
and short efficient batches within the EO. However,
this base level of SCN could affect the subsequent
regeneration of the IX resin. The limit of this has yet
Table 8. Summary of scoping level capital costing for electro-oxidation circuits
Parameter Units Case Study 1: Mexico Case Study 2: Abitibi
Ion Exchange Columns USD $0 $2,508,000
Electric Cell Cost USD $1,321,000 $316,000
Electrode Cost* USD $1,101,000 $264,000
Rectifier Cost† USD $1,052,000 $526,000
Scrubbing System USD $797,000 $530,000
Vendor Equipment Subtotal USD $4,271,000 $4,144,000
Installation Factor 1.5
Vendor Equipment Installed Cost USD $6,406,500 $6,216,000
Tanks USD $164,000 $424,000
Transfer Pumps USD $96,000 $98,000
Installation Factor 3
Mechanical Equipment Installed Cost USD $780,000 $1,566,000
Total Installed Cost USD $7.19 $7.78
*The electrode cost is based conservatively on titanium electrode with mixed metal oxide (MMO) coating for all electrodes
† Rectifier cost is estimated based total kW needed and assuming direct current (DC)
Table 9. Operating cost summary for case studies
Modelling Parameter Units Case Study 1: Mexico Case Study 2: Abitibi
NaCN Recovered t/d
tpa
5.4
1,774
1.5
506
Value of NaCN Recovered USD/a $4.40 M $1.26 M
Running Power MW 3.2 1.2
Power Cost USD/a $2.61 M $0.65 M
Maintenance Cost USD/a $0.22 M $0.25 M
Operating labour Assumed no incremental labor required, as existing staff at site is sufficient
Total OpEx USD/a ($2.83 M) ($0.90 M)
Potential Economic Benefit USD/a $1.57 M $0.36 M
Simple Pay back Years 4.8 23
Current LOM Years 9 12
As the above economic analysis shows, incorporation of
a thiocyanate EO circuit into the two mines being studied
returns a net positive result. The EO circuit incorporated
into the Mexican process within the SART plant shows a
simple payback of four years, which is within the current
LOM (based on current proven reserves). The facility in the
Abitibi region of Quebec, while still a net positive return,
did not show a payback within the site’s current LOM,
indicating the need to expand beyond the base economic
driver for this process implementation, and to look at addi-
tional benefits which the EO process would provide.
ASSESSMENT OF CONSTRAINTS AND
LIMITATIONS
While returning positive yearly returns, as the above discus-
sion has shown, the process is sensitive to many factors, and
each of these need to be taken into account for each process
solution, site, jurisdiction, etc. Some sensitivities, and site
specific considerations affecting the implementation of an
EO circuit are discussed below:
• IX: effect of residual SCN in recycled regenerant
The rich SCN regenerant solution which strips the
IX columns is sent to the electro oxidation circuit
to recover HCN from SCN. However, as SCN is
oxidized, the efficiency of the circuit is reduced. To
maintain a high EO current efficiency, a high SCN
concentration is beneficial – ie, it is beneficial for the
EO circuit to have a high recirculating load of SCN,
and short efficient batches within the EO. However,
this base level of SCN could affect the subsequent
regeneration of the IX resin. The limit of this has yet
Table 8. Summary of scoping level capital costing for electro-oxidation circuits
Parameter Units Case Study 1: Mexico Case Study 2: Abitibi
Ion Exchange Columns USD $0 $2,508,000
Electric Cell Cost USD $1,321,000 $316,000
Electrode Cost* USD $1,101,000 $264,000
Rectifier Cost† USD $1,052,000 $526,000
Scrubbing System USD $797,000 $530,000
Vendor Equipment Subtotal USD $4,271,000 $4,144,000
Installation Factor 1.5
Vendor Equipment Installed Cost USD $6,406,500 $6,216,000
Tanks USD $164,000 $424,000
Transfer Pumps USD $96,000 $98,000
Installation Factor 3
Mechanical Equipment Installed Cost USD $780,000 $1,566,000
Total Installed Cost USD $7.19 $7.78
*The electrode cost is based conservatively on titanium electrode with mixed metal oxide (MMO) coating for all electrodes
† Rectifier cost is estimated based total kW needed and assuming direct current (DC)
Table 9. Operating cost summary for case studies
Modelling Parameter Units Case Study 1: Mexico Case Study 2: Abitibi
NaCN Recovered t/d
tpa
5.4
1,774
1.5
506
Value of NaCN Recovered USD/a $4.40 M $1.26 M
Running Power MW 3.2 1.2
Power Cost USD/a $2.61 M $0.65 M
Maintenance Cost USD/a $0.22 M $0.25 M
Operating labour Assumed no incremental labor required, as existing staff at site is sufficient
Total OpEx USD/a ($2.83 M) ($0.90 M)
Potential Economic Benefit USD/a $1.57 M $0.36 M
Simple Pay back Years 4.8 23
Current LOM Years 9 12