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About the Bond_Mill ThroughputSpreadsheet ...

Scope :

The Bond_Mill Throughput spreadsheet was designed to estimate the Grinding Capacity of a given mill of knowndimensions and operating conditions - Net Power Draw in particular - based on the traditional Bond's Law and the Hogg& Fuersteneau Power Model (see Mill Power_Ball Mills spreadsheet for further details on such model).

Theoretical Framework :

Undoubtedly, the extensive work ofFred C. Bond ("The Third Theory of Comminution", AIME Trans.,Vol. 193, p. 484,1952. Also in Mining Engineering, May 1952) has been widely recognized as a very significant contribution to a firstunderstanding of the operational response of conventional ball mills in various grinding circuits. His Third Theory or"Law" of Comminution has become the most traditionally accepted framework for the evaluation of existing grindingoperations as well as the design of new installations :

E = 10 Wi(1/P

801/2 1/F

801/2 )

where :

E = Specific Energy Consumption, kWh/ton ground.F

80= 80% passing size in the Fresh Ore Feed Stream, microns.

P80

= 80% passing size in the Final Ground Product, microns.

Wi

= Bond's Work Index, indicative of the hardness of the ore, kWh/ton.

The Bond's Law so allows, as a first approach, to estimate the energy demand (kWh) required to grind each ton of ore.Such Specific Energy Consumption determines in turns the Capacity of the grinding section, by the expression :

M = P/Ewhere :

M = Fresh Ore Throughput (not including Circulating Load), ton/hr.

P = Net Mill Power Demand, kW.

Bond's Work Index may be estimated directly from operational data (whenever available) from back-calculation of the firstequation above. In such case is denoted as the Operational Work Index :

Wio

= E / 10 (1/P80

1/2 1/F80

1/2 )

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Moly-Cop Tools / 59135951.xls 05/25/2011 / 18:41:52

BOND'S LAW APPLICATIONEstimation of a Conventional Ball Mill Grinding Capacity

Remarks

molino 10x 10, fresh feed

GRINDING TASK :

Ore Work Index, kWh/ton (metric) 21.00 Specific Energy, kWh/ton 21.09

Feed Size, F80, microns 4000 Net Power Available, kW 303

Product Size, P80, microns 74.0 Number of Mills for the Task 1

Total Plant Throughput, ton/hr 14.37 Net kW / Mill 303

Mill

MILL DIMENSIONS AND OPERATING CONDITIONS : Power, kW

249 Balls

Diameter Length Mill Speed Charge Balls Interstitial Lift 13 Overfilling

ft ft % Critical Filling,% Filling,% Slurry Filling,% Angle, () 41 Slurry

9.40 9.40 74.00 45.00 40.00 100.00 35.00 303 Net Total

L/D rpm 10.0 % Losses

1.00 18.49 337 Gross Total

% Solids in the Mill 76.00 Charge Mill Charge Weight, tons Apparent

Ore Density, ton/m3 2.70 Volume, Ball Slurry Density

Slurry Density, ton/m3 1.92 m3 Charge Interstitial above Balls ton/m3

Balls Density, ton/m3 7.75 8.33 34.43 5.68 1.77 5.028

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