In the pulp making industries, the value of freeness or specific surface area of pulp is measured to check the quality of pulp. But, there have been few inf ormations about the physical correlation between these values and the operational conditions of processing of pulp.
In this paper, to make clear the factors which concern in values of freeness and specific surface area of pulp, the experimental investigations were performed on the relation among the pressure drop of water through pulp bed and freeness, specific surface area of pulp measured by Pulmac method.
Freeness and specific surface area of pulp were correlated with shape factor of fiber and the projected area of fiber related to pressure drop of water through pulp bed.
From the experiments, it was found that both values, freeness and specifie surface area, can be estimated from the pressure drop of water through pulp bed.

View full abstract

The filtration behavior of calcite/water su spension containing various amount of Sodium hexameta-phoshate (NaPOM₃)₆, were observed and the specific filter cake resistance was analized in a view point of interfacial electrochemical phenomenon.
In the filtration experiment, the relation between filtrate volume and filtration time, and also the porosity of filter cake were measured, using a vacuum type filtration apparatus.
Two kinds of average specific filter cake resistances, denoted as α and α' were determined from the filtration data. Here, the α is a resistance calculated by the filtration equation derived from Hagen-Poiseuialle's law and α' is one calculated by Kozeny-Carman's equation.
The resistance α takes larger value than α', and a dependence on zeta-potential of the electrical double layer which is elevated to be dispersive by increasing the addition amount of (NaPO₃)₆ is quite different between them, as like increasing α, against decreasing α'.
The value of relative viscosity η'/η equivalent to α'/α increases gradually accompanied with zeta-potential until maximum value of about 8, where η and η' are viscosity of water in bulk and in filter cake respectively. The η'/η is also changed “thixotropically” by the flowing velocity of the fluid through the micro porous filter cake.
For these results, it is discussed that the electrical double layer and oriented water molecules surrounding the suspended particle will originate the large porosity due to keep far the particle-particle distance, and high viscous water film at the interface.

View full abstract