XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3793
written describing the use of pilot size HPGR for scaling
up to a larger operational HPGR (van der Meer, Morrell, et
al.). In addition to COREM testing, Weir conducted a final
confirmation test program after vendor selection to verify
test results and lock in performance parameters.
The COREM test work for the project consisted of 5
open circuit pass tests (see Table 3) and 7 lock cycle tests
using a composite sample representing expected feed to the
HPGR in full scale operation. The intent of the 5 open
circuit passes was to evaluate the impact of varying mois-
ture content and applied pressure on product particle size
distribution, specific throughput, and specific energy to
determine expected operating pressure prior to starting the
lock cycle program. The results of the open circuit pass tests
showed nominal operating pressure of 3.5 N/mm2 where
the size reduction was maximized with the least amount of
required power.
Upon completion of the open circuit testing, the lock
cycle program was started using the targeted 3.5 N/mm2
pressure to fully understand HPGR operating parameters
in the full-scale operation. The lock cycle program consisted
of batch processing with HPGR product being screened at
the envisioned operating cut size of 4 mm and the screen
oversize being blended back with the fresh feed ahead of
the next run. For the first three lock cycle passes there was
variation in the specific throughput, power consumption,
and product size distribution. The specific throughput con-
tinued to vary for the fourth lock cycle pass and by the
fifth pass steady state had been reached. This steady state
condition was confirmed in the fifth through seventh lock
cycle pass and can be seen below in Table 4.
In addition to HPGR scale up, there was further test-
ing conducted to review flake competency, autogenous
wear layer build-up, the impact of HPGR processing on
bond work index, and understanding the wear life of the
tyres. These results are shown below:
• Flake competency testing showed few flakes present
which were not competent and easily broken up
• Tyres showed solid build-up of autogenous wear
layer between the studs indicating adequate protec-
tion for long wear life
• Bond work index showed a reduction from
15.5 kWh/t to 12.7 kWh/t
• Expected tyre wear life exceeding 8,000 hours and
above 12,000 hours once fully optimized
Given the results of test work conducted jointly with
COREM, High Pressure Grinding Rolls (HPGR) were
selected for the Côté Gold comminution flowsheet. The
Côté ore body is primarily Tonalite and Diorite Breccia with
average Bond Work Index of approximately 15.6 kWh/t
and average AxB value of 25.9, as reported earlier. It was
noted during ore hardness variability test work that there
was not much variation in hardness between lithologies and
that an HPGR would be a more appropriate and economic
option than a SAG mill as there were savings in power con-
sumption and wear parts.
Lovatt et al. recently published real operational
trade-off between Tropicana (HPGR-based) and Gruyere
(SABC). It was concluded that the HPGR-based circuit
proved to have 20.1% lower OPEX costs despite having a
19.4% higher CAPEX cost. The payback of the HPGR cir-
cuit was only 1.5 years. Considering Gruyere’s comminu-
tion characteristics, with an AxB value of 31.5 and Ai value
of 0.53, the feeding conditions are comparable but slightly
less aggressive which suggests that Côté will benefit from
even greater OPEX advantages. In terms of the recovery
Table 3. Open circuit test work conditions
Test#
Moisture,
%
Specific Press.,
N/mm2
Velocity,
RPM
DOE-1 4.5 2.5 18.0
DOE-2 4.5 4.5 18.0
DOE-3 3.5 3.5 18.0
DOE-4 2.5 2.5 18.0
DOE-5 2.5 4.5 18.0
Table 4. HPGR Locked cycle, closed circuit test work conditions
Test#
P80, mm
Circulating
Load, %
Specific
Press.,
N/mm2
Specific
Throughput,
t/h/m3/s
Net Energy,
kwh/t
Generated
–4 mm, %
P80 Final
Product, mm Feed Edge Center
6 (Cycle 1) 15.62 15.00 8.35 47 3.6 253.8 1.61 57.0 2.16
7 (Cycle 2 14.37 14.18 8.44 103 3.5 224.7 1.67 55.0 2.11
8 (Cycle 3) 14.67 13.89 7.13 97 3.5 232.1 1.61 63.0 2.25
9 (Cycle 4) 13.62 13.47 6.83 90 3.5 237.7 1.60 62.4 2.67
10 (Cycle 5) 14.40 13.01 7.62 92 3.4 229.8 1.61 57.0 2.14
11 (Cycle 6) 14.55 13.67 8.29 94 3.4 226.6 1.64 54.8 2.09
12 (Cycle 7) 13.85 13.64 7.72 96 3.4 226.3 1.63 63.4 2.32
written describing the use of pilot size HPGR for scaling
up to a larger operational HPGR (van der Meer, Morrell, et
al.). In addition to COREM testing, Weir conducted a final
confirmation test program after vendor selection to verify
test results and lock in performance parameters.
The COREM test work for the project consisted of 5
open circuit pass tests (see Table 3) and 7 lock cycle tests
using a composite sample representing expected feed to the
HPGR in full scale operation. The intent of the 5 open
circuit passes was to evaluate the impact of varying mois-
ture content and applied pressure on product particle size
distribution, specific throughput, and specific energy to
determine expected operating pressure prior to starting the
lock cycle program. The results of the open circuit pass tests
showed nominal operating pressure of 3.5 N/mm2 where
the size reduction was maximized with the least amount of
required power.
Upon completion of the open circuit testing, the lock
cycle program was started using the targeted 3.5 N/mm2
pressure to fully understand HPGR operating parameters
in the full-scale operation. The lock cycle program consisted
of batch processing with HPGR product being screened at
the envisioned operating cut size of 4 mm and the screen
oversize being blended back with the fresh feed ahead of
the next run. For the first three lock cycle passes there was
variation in the specific throughput, power consumption,
and product size distribution. The specific throughput con-
tinued to vary for the fourth lock cycle pass and by the
fifth pass steady state had been reached. This steady state
condition was confirmed in the fifth through seventh lock
cycle pass and can be seen below in Table 4.
In addition to HPGR scale up, there was further test-
ing conducted to review flake competency, autogenous
wear layer build-up, the impact of HPGR processing on
bond work index, and understanding the wear life of the
tyres. These results are shown below:
• Flake competency testing showed few flakes present
which were not competent and easily broken up
• Tyres showed solid build-up of autogenous wear
layer between the studs indicating adequate protec-
tion for long wear life
• Bond work index showed a reduction from
15.5 kWh/t to 12.7 kWh/t
• Expected tyre wear life exceeding 8,000 hours and
above 12,000 hours once fully optimized
Given the results of test work conducted jointly with
COREM, High Pressure Grinding Rolls (HPGR) were
selected for the Côté Gold comminution flowsheet. The
Côté ore body is primarily Tonalite and Diorite Breccia with
average Bond Work Index of approximately 15.6 kWh/t
and average AxB value of 25.9, as reported earlier. It was
noted during ore hardness variability test work that there
was not much variation in hardness between lithologies and
that an HPGR would be a more appropriate and economic
option than a SAG mill as there were savings in power con-
sumption and wear parts.
Lovatt et al. recently published real operational
trade-off between Tropicana (HPGR-based) and Gruyere
(SABC). It was concluded that the HPGR-based circuit
proved to have 20.1% lower OPEX costs despite having a
19.4% higher CAPEX cost. The payback of the HPGR cir-
cuit was only 1.5 years. Considering Gruyere’s comminu-
tion characteristics, with an AxB value of 31.5 and Ai value
of 0.53, the feeding conditions are comparable but slightly
less aggressive which suggests that Côté will benefit from
even greater OPEX advantages. In terms of the recovery
Table 3. Open circuit test work conditions
Test#
Moisture,
%
Specific Press.,
N/mm2
Velocity,
RPM
DOE-1 4.5 2.5 18.0
DOE-2 4.5 4.5 18.0
DOE-3 3.5 3.5 18.0
DOE-4 2.5 2.5 18.0
DOE-5 2.5 4.5 18.0
Table 4. HPGR Locked cycle, closed circuit test work conditions
Test#
P80, mm
Circulating
Load, %
Specific
Press.,
N/mm2
Specific
Throughput,
t/h/m3/s
Net Energy,
kwh/t
Generated
–4 mm, %
P80 Final
Product, mm Feed Edge Center
6 (Cycle 1) 15.62 15.00 8.35 47 3.6 253.8 1.61 57.0 2.16
7 (Cycle 2 14.37 14.18 8.44 103 3.5 224.7 1.67 55.0 2.11
8 (Cycle 3) 14.67 13.89 7.13 97 3.5 232.1 1.61 63.0 2.25
9 (Cycle 4) 13.62 13.47 6.83 90 3.5 237.7 1.60 62.4 2.67
10 (Cycle 5) 14.40 13.01 7.62 92 3.4 229.8 1.61 57.0 2.14
11 (Cycle 6) 14.55 13.67 8.29 94 3.4 226.6 1.64 54.8 2.09
12 (Cycle 7) 13.85 13.64 7.72 96 3.4 226.3 1.63 63.4 2.32