© CoalTech Pty Ltd 2004Fig 1. Expected Fineness
for a Given Petrographic Analysisat Pilot Mill Nominal Operating Conditions
2Fig 2. Expected Capacity for a Given Fineness
and Hardgrove Grindability Index (HGI)
3
Vertical Spindle Mill Performance Curvesbased on pilot scale tests1
35 40 45 50 55 60 65 70 75 80 85
Predicted Fineness (% minus 75 mm)
35
40
45
50
55
60
65
70
75
80
85
30 40 50 60 70 80 90HGI
10
15
20
25Rate = 500 kg/hr
Roll Pressure = 3 to 4 MPaRoll Pressure = 2 MPaRoll Pressure = 6 MPa
Data only shown for roll pressures 3 to 4 MPa
Notes:For detailed information on how these curves were generated see
CoalTech’s Report - ACARP Research Project C13062 “PredictingPulveriser Performance” by P. Bennett, 2004.
While the predicted fineness results are for ACIRL’s pilot scale millthey do indicate the ranking of coals in terms of PF fineness basedon Petrographic Analysis, see Fig. 3.
The capacity factors given by Fig. 2 are similar to the values givenby mill manufacturers’ curves and are based on Fig. 4.
The fineness determined by Fig. 1 indicates whether the milloperating conditions (roll pressure, classifier setting, etc) will requiredto be increased or decreased from the mill’s “nominal” settings toachieve a fineness of 70% passing 75 m.
1
2
3
4
Fig 3 Fit to Maceral Group Model Fig 4 Specific Power
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
55
60
65
70
75
80
85
Mean Maximum Reflectance of Vitrinite %
Vitrinite +Lipitinite vol %
20
3040506070
8090
100
HGI 35 40 45 50 55 60 65 70 75 80 85 90
0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6Capacity Factor
55
60
65
70
75
80
85
25 30
For this 40 HGIcoal mill conditionscan be decreasedto achieve afineness of 70%
Note 4
