Benchmarking: Bond - Fort Knox

Benchmarking: Bond/Barratt - Fort Knox

• Magnuson, R.; Hallow, J.; Mosher, J.; Major, K., The Fort Knox Mill: Design, Commissioning and Operation. Proceedings of the SAG 2001 Conference, Vancouver, Canada.

Checking the July 1999 survey against the Bond/Barratt model for SAB circuit. Using 15% E_ssbm contingency.

The paper is believed to report power and specific power consumption values relative to the plant DCS. It is assumed that the DCS measurement happens at the motor input leads; the conversion of DCS to shell power for synchronous motors with pinions is 0.960 × 0.985 = 0.9456.

• Work index for ball milling=13.67 kWh/t (12.4 kWh/st);
• Work index for rod milling=12.02 kWh/t (10.9 kWh/st);
• assume Work index for crushing=10 kWh/t (similar to pilot plant samples).
• Feed F₈₀ size= 106 mm
• Product P₈₀ size= 178 µm
• Measured E_total= 10.5 kWh/t relative to shell (10.1 kWh/st relative to DCS)
  • Bond/Barratt model E_total= 11.95 kWh/t (model 7% high)
• Measured Wi_O= 14.8 kWh/t (13.4 kWh/st)
  • Bond/Barrat model Wi_O= 16.6 kWh/t (model 11% high)

Mill power draw is given in both Tables 4 and 6. It appears that the units in Table 4 are incorrect, and the SAG and ball mill power draw values appear to be kW and not horsepower, as stated. The power draw values from Table 6 are:

• SAG mill power draw= 8,910 kW (11,950 hp). Assumed to be DCS indication.
  • Conditions to match power draw: balls=16% v/v; filling=31% v/v; speed=75% c/s; 6" liner.
• Ball mill power draw= 10,330 kW (13,850 hp, sum of two mills). Assumed to be DCS indication.
  • Conditions to match power draw: filling=29% v/v; speed=74% c/s; 6" liner.
• Measured throughput= 1733 t/h (1910 st/h)
  • Bond/Barratt model= 1522 t/h (model 13% low)

Result for default model conditions:

	Etotal	WiO		Tonnage
Model	11.95	16.60	kWh/t	1,522	t/h
Measured	10.50	13.97	kWh/t	1,733	t/h
Difference	1.45	2.63	kWh/t	211	t/h
Difference	12.9%	17.2%		12.9%