Bibliography: Benchmarking

Bibliography: Benchmarking of models

The following list of references show data useful for benchmarking against the different models.

Benchmarking: Circuit Specific Energy Consumption - Bond/Barratt

• 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.

• 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= 11.1 kWh/t (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)

Benchmarking: SAG Mill Power Draw - Fimiston

• Nelson, M; Valery, W; Morrell, S, Performance Characteristics and Optimisation of the Fimiston (KCGM) SAG Mill Circuit, Page 233 - 248, SAG 1996 Conference, Vancouver, Canada.
  • Diameter inside shell = 10.970 m (36 ft)
  • Diameter inside liners = 10.797 m (35.42 ft, 3.5 inch effective liner thickness)
  • Belly length inside liners (EGL) = 4.417 m (14.5 ft)
  • Centre-line length = 6.920 m

Table 4 presents results of several SAG surveys at different speed and load conditions. The survey measured motor input power. Drives are assumed to have an efficiency of 0.96 and pinion efficiency of 0.985, so the model shell power draw is converted to motor input power by dividing by 0.9456. The predicted power draw of Example project circuit number 7 (Fimiston) using sample MLE, based on the KCGM paper published by Campbell, J. et al; 1998 AusIMM Annual Conference.

Survey	Survey Power, kW at input	Mill speed, %critical	Ball load, %v/v	Total load, %v/v	Pulp %solids, w/w	Morrell SAG Model, kW at input / shell	Loveday/Baratt Model, kW at input / shell
Survey 1	9,255	72.5	13	21.6	65.9	9,268 / 8,764	10,372 / 9,808
Survey 2	10,374	77	13	25.2	63.3	10,481 / 9,911	11,238 / 10,636
Survey 3	8,395	75	15	16.1	70	9,193 / 8,693	10,818 / 10,230
Survey 4	8,299	78	11.5	13.5	60	7,766 / 7,344	can't do
Survey 5	10,976	80	11.5	22.2	60	9,877 / 9,340	10,322 / 9,760
Survey 6	8,616	74	11.5	13.6	63	7,394 / 6,992	can't do
Survey 7	11,684	82	14	20	75	10,782 / 10,195	11,037 / 10,437
Survey 8	11,610	78	13	28.6	75	11,415 / 10,794	11,125 / 10,520
Survey 9	11,571	78	13	25.8	75	10,990 / 10,392	11,668 / 11,033
Survey 10	9,408	80	12	19	75	9,655 / 9,130	10,309 / 9,749

• The overall average difference between the Morrell model motor input predictions and the measurements are -3.4%, and range from -15.3% to +9.1%.
• The overall average difference between the Loveday/Barratt model motor input predictions and the measurements are +4.8%, and range from -6.1% to +25.2%.

The SAG mill belly length reported can be achieved with a 16.5 degree head angle and 2.47 m trunnion diameter.

Benchmarking: SAG Mill Power Draw - Cadia

• Radziszewski, P.; Valery, W, Cadia SAG Mill Simulated Charge Behaviour, Annual General Meeting of the Canadian Mineral Processors, Ottawa, 1999.
  • SAG mill diameter inside liners = 12.024 m (40 ft, 3.3 inch effective liner thickness)
  • SAG mill effective grinding length = 6.072 m (19.9 ft)
  • SAG mill centre line length = 9.212 m
  • Maximum ball size = 125 mm
  • Ore density = 2.60 kg/L
  • Ball density given as 7.85 kg/L.
  • Pulp density not given. Assuming 70% solids by weight.

Table III gives details of six SAG mill surveys:

Survey	Survey Power, kW at shell	Mill speed, %critical	Ball load, %v/v	Total load, %v/v	Morrell SAG Model, kW at shell	Loveday/Baratt Model, kW at shell
Survey 1	11,189	79	0	28.8	11,868	12,126
Survey 2	10,321	79	0	28.5	11,787	12,039
Survey 3	10,824	78	4	25	12,762	13,390
Survey 4	14,945	78	4	40.7	15,806	15,096
Survey 5	17,586	74	12	31.6	17,351	18,216
Survey 6	17,963	78	12	26.1	17,298	18,505

Benchmarking: SAG Mill Power Draw - Cadia

• Boghey, A.; Svalbonas, V.; Jones, S.M., Supply, Installation & Commissioning of the World's Largest Grinding Mill, Annual General Meeting of the Society for Mining, Metallurgy & Exploration (SME), 2000.

Mill filling level 33% v/v. Ball charge not measured, but expected to be in 12% to 13% v/v range. Ore density not indicated, assuming 2.65 kg/L. Ball density given as 7.85 kg/L.

Survey conducted during late commissioning, Figure 8 yields:

Survey	Survey Power, kW at shell	Mill speed, RPM	Mill speed, %critical	Morrell SAG Model, kW at shell	Loveday/Barratt Model, kW at shell
23:30	19,300	8.99	73.7	17,148	18,233
23:40	19,450	9.4	77.1	18,042	19,199
23:50	19,550	9.9	81.2	19,058	19,868

Benchmarking: Ball Mill Power Draw - Fimiston

• Nelson, M; Valery, W; Morrell, S, Performance Characteristics and Optimisation of the Fimiston (KCGM) SAG Mill Circuit, Page 233 - 248, SAG 1996 Conference, Vancouver, Canada.
  • Diameter inside shell = 5.49 m (18 ft)
  • Diameter inside liners = 5.35 m (17.5 ft, 3.0 inch effective liner thickness)
  • Belly length inside liners (EGL) = 7.60 m (25 ft)
  • Centre-line length = 8.76 m
  • Top ball size = 80 mm

Table 5 presents results of a single ball mill survey. The survey measured motor input power. Drives are assumed to have an efficiency of 0.96 and gearbox+pinion efficiency of 0.970, so the model shell power draw is converted to motor input power by dividing by 0.9312. The predicted power draw of Example project circuit number 7 (Fimiston) using sample MLE, based on the KCGM paper published by Campbell, J. et al; 1998 AusIMM Annual Conference.

Survey	Survey Power, kW at input	Mill speed, %critical	Total load, %v/v	Pulp %solids, w/w	Morrell SAG Model, kW at input / shell	Nordberg Model, kW at input / shell
Survey 1	3,864	66.7 68.3 †	38.7	72.0	3,933 / 3,776	3,592 / 3,345

^† The appendix of the paper lists the mill speed as 12.5 RPM. The mill is fixed speed, so the %critical speed is only a function of mill effective diameter (as liners wear). Doing the math (neglecting the balls) gives a 68.3% critical speed.

The ball mill belly length can be achieved with a 18 degree head angle and 1.9 m trunnion diameter.

Historic & Other Interesting Benchmarking

1. Myers, J.F., Michaelson, S.D., Bond, F.C., Rod Milling—Plant and Laboratory Data, Technical Publication No. 2175, American Institute of Mining and Metallurgical Engineers, 1947. [1]