| Summary: | 博士 === 國立臺灣大學 === 化學工程學系研究所 === 86 === In the application of the filtration theory, the relationships among solid
compressive pressure, porosity and specific filtration resistance are
indispensable. This study summarized the methods used to determine the
relationship between porosity vs. Ps and specific filtration resistance vs.
Ps, and then to compare the reliability of these methods.
Stress distribution in a confined wet cake is analyzed by solving the
equation of equilibrium of force acting on the system. An integrated equation
is derived to estimate the stress distribution within the cake providing the
boundary values around the cell are known. The results are applied to
estimate the mean stress acting on the confined cake and also to correct the
effect of side wall friction of the compression-permeability cell (C-P cell)
tests.
The dynamic simulation method proposed by Lu and Hwang(1993) is modified
by considering the variation of the pressure drop across the septum and
specific surface area of particles. The importance of the accuracy of the
value of surface cake porosity is also examined, and the effects of the
operating condition, such as pressure, filtration rate and slurry
concentration, are also discussed.
These results of the obtained relationships between porosity vs. Ps and
specific filtration resistance for different compactness materials through the
proposed dynamic analysis method give the results very close to the corrected
C-P cell test data. Using these obtained results to predict the
performances of the filtration, the results of dynamic simulation can give the
best prediction with an average deviation around 4%, while the corrected
C-P cell test data may give an average deviation around 5%, and the
uncorrected C-P cell test data gives an average deviation around 10%.
For understanding how the sedimentation of the particles will effect the
cake formation in plate and frame type filters, the changing of slurry
concentration and pumping rate were used to examine the uniformity of the
formed cake in frame. The results show that the lower slurry concentration
and lower pumping rate all give a lower rate of cake formation which will
result in a more non-uniform cake.
For understanding how the frictional coefficient of the particles wetted
with different liquid will effect the structure of a filter cake, particles
were suspended into liquids with different properties to examine its effect on
the cake porosity and filtration resistance. The results show that the
changing of frictional coefficient of the wetted particles will effect the
structure and cake characteristics of a filter cake.
|
|---|
