Benchmarking: Amelunxen SGI - Agnico Eagle

Benchmarking: Amelunxen SGI Specific Energy Consumption - Agnico Eagle Laronde

Starkey, J., Robitaille, J., Cousin, P., Jordan, J. and Kosick, G., Design of the Agnico-Eagle Laronde Division SAG mill. Proceedings of SAG 2001, pages III-165 to III-178.

Survey conducted shortly after start-up

Design Criteria

Actual operating data, table 7 from the reference

• SAG circuit F₈₀ = 100 mm
• transfer T₈₀ = 244 µm
• circuit P₈₀ = 74 µm
• SAG power draw (at motor input) = 1350 kW (at mill shell = 1283 kW)
• SAG mill ball charge = 10.6 % vol
• SAG mill discharge % solids = 84% weight
• SAG mill speed 8.59 RPM (53.4% of critical)

(to achieve DCS power of 1350 kW requires 14% vol mill load)

• ball mill power draw (sum of 2 mills, at motor input) = 1422 kW (at mill shell = 2 × 673 kW = 1346 kW)
• ball mill % solids = 83% weight

(to achieve 1422 kW, assume 30% vol mill charge, 17 RPM)

Design criteria

• SGI (actually SPI&tm;) of ore (Oct 1, 2000 to - April 30,2001); assumed to be the 25^th percentile = 24 minutes.
• Wi_BM assumed to be 10 kWh/tonne.
• Plant availability = 94.4%

Mill criteria

• SAG mill: 24 foot nom diam by 12 foot effective grinding length (EGL)
• ball mill: two 11 foot nom diam by 17 foot (assumed to be EGL)
• SAG mill single variable speed motor 4500 HP
• Ball mill single fixed speed motors 1000 HP (each mill)
• assume rubber liners in SAG, nominal 8½ inch liner thickness
• assume steel liners in ball mills, nominal 3¼ inch liner thickness

Modelling

The Bond/Barratt SABC-B model is used with the default 10% E_ssbm calibration factor.

• circuit F₈₀ = 132 mm
• circuit P₈₀ = 180 µm
• The average ball mill work index given as 16 kWh/short ton = 17.6 kWh/tonne
• The relationship between A×b and Wi_RM for Andean copper porphyries can be used to determine the following rod mill work index values.
  • A×b of Esperanza ore; avg= 39; becomes Wi_RM=14.5 kWh/tonne
• No crushing work index is given. Assume a value of 12 kWh/tonne (slightly higher than typical porphyry)
• No ore density is given. Assume similar to Los Bronces, density=2.64 t/m³

SAG mill is modelled using following:

• Austin model
• assume ore density 2.64 t/m³, same as Los Bronces
• nominal diameter 40 foot, effective grinding length 26 foot (deduct 2 ft from cylinder length)
• assume 6 inch liner effective thickness, mill speed 75% of critical
• ball charge 16% v/v; total filling 26% v/v gives the desired 92.4% utilization of motor power

Ball mill is modelled using following:

• Nordberg wet overflow model
• assume ore density 2.64 t/m³, same as Los Bronces
• nominal diameter 27 foot, effective grinding length 44.5 foot (deduct 6 inches from cylinder length)
• assume 6 inch liner effective thickness, mill speed 75% of critical
• total filling 30% v/v gives the desired 95% utilization of motor power

Results

Result for default Amelunxen SGI SAB model conditions:

	Esag	Epeb	Ebm	Etotal	t/h
Predicted		-
Survey		-
Difference		-
Difference		-