Bibliography: Benchmarking

Bibliography: Benchmarking of models

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

Benchmarking: SAG Mill Power Draw

• 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: Ball Mill Power Draw

• 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	3,485 / 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]