Frequency and Intensity or Severity of Impact

Danforth (1969) developed two independent expressions to quantify the freatment of fibres. According to this theory, refining is expressed as a function of two factors, namely number (N) and severity (5), of the refining impacts between the bar edges [Equations (13.8) and (13.9)]. 

This theory includes most of the factors which affect refining. However, the main problem is the use of constants, which precludes quantification unless a considerable amount of trial work is undertaken to assign values to the two constants. 

The C factor theory developed by Kerekes (1990) is based on the same starting point as that of other refining theories the effective refining energy may be directly related to the number of impacts and the intensity or energy content of each impact as shown below in Equation (13.10)  

The C -factor represents the capacity of the refiner to impose impacts upon pulp fibres passing through. The C-factor finks the power input, P, and pulp mass flow rate, F, through a refiner to the average number, N, and intensity, /, of impacts imposed on fibres. N and I are derived Ifom the relationships shown in Equations (13.11). 

The C-factor itself is a function of filling geometry, rotation speed, consistency, fibre length and fibre coarseness. For a disc refiner, the C factor is given by Equation (13.12). 

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