The Determination of the Cake Characteristics and Its Application

• Main Authors: Huang, Yun-Peng, 黃雲鵬
• Other Authors: Lu Wei-Ming
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/65378594523317293082

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.