The Sugar Engineers

Mill Capacity Calculations

There are a large number of formulae for the calculation of the capacity of a milling tandem. Hugot gives the following formula:

A = 0.9 c·n·√N·(1-0.06·n·D)·L·D²/f

where

• c
  is a factor dependent on the cane preparation equipment,
  c
  = 1.3 if the tandem is preceded by a shredder
• n
  is the mill speed in rev/min
• N
  is the number of rollers in the tandem
• L
  is the length of the roll in metres
• D
  is the mean diameter of the rollers in metres
• f
  is the fibre percent cane

The problem with M. Hugot's equation is that is a function of the square of the mill speed, which means mathematically that the mill capacity will increase with speed, reach a maximum and then deacrease, as the speed increases. This could be interpreted in an engineering sense that the mill will have an optimum speed to operate at beyond which the capacity deacreses due to slippage of bagasse in the mill. It does not seem prudent to design the mills so that the capacity could be in the decreasing region.

The online calculator below uses data gleaned and adapted from the graph supplied by Walkers in Dr Rein's book Cane Sugar Engineering and from the skoda.cz nomogram below.

Mill Capacity Calculations Online

Mill Data

Number of Mills
Mill Roll Length 36 42 48 54 60 66 72 78 84 90 95 100 105 inch

Mill Roll Diameter is assumed to be half of the roll length

Operational Data

Roll Speed rpm m/min
Fibre%Cane
Mill Hydraulic Pressure MPa

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Mill Sizing Nomogram

The nomogram below from skoda.cz is a quick guide to sizing a milling tandem