STUDY ON THE KINETICS AND THE VARIABLE INTERNAL POROSITY DURING
EXTRACTION FROM VEGETABLE MATERIAL
E. Simeonov, I. Seikova, A. Mintchev
STUDY ON THE SLUDGE CHARACTERISTICS AND RHEOLOGICAL
BEHAVIOUR AT DEWATERING WITH VACUUM FILTERS
B. Koumanova, M. Karsheva
STUDY ON
THE SLUDGE CHARACTERISTICS AND RHEOLOGICAL BEHAVIOUR AT DEWATERING WITH VACUUM
FILTERS
B. Koumanova, M. Karsheva
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: bogdana@uctm.edu
|
Received 18 September 2002
Accepted 22 October 2002
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The results from the investigation on the
characteristics and rheological behaviour during the conditioning and vacuum
filtration of the sludge in Sofia Wastewater Treatment Plant are presented.
Samples of raw sludge, sludge after conditioning with aluminium hydroxychloride
and lime, sludge cake and filtrate after vacuum filter, were studied. Atomic
absorption spectrometry, silicate analysis and elementary analysis were used
to describe the chemical distribution of sludge constituents. Co-axial cylinders
viscometer Rheotest RV2 was used for the rheological measurements. The flow
curves for the raw sludge and for the conditioned sludge are definitely non-Newtonian.
The first one is non-linear without intercept and could be described by the
power law rheological model of Ostwald-de-Waele. The Bingham model is more
suitable for the conditioned sludge. The rheological parameters were determined
by less squares method. Exponential dependence of flow index n on the organics
content in raw sludge was observed.
Keywords: sludge, dewatering, vacuum filter, rheological properties.
STUDY ON
THE KINETICS AND THE VARIABLE INTERNAL POROSITY DURING EXTRACTION FROM VEGETABLE
MATERIAL
E. Simeonov, I. Seikova, A. Mintchev
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: evgeni@uctm.edu
|
Received 13 May 2002
Accepted 26 May 2002
|
The structural modifications in the solid
associated with the porosity increase were investigated experimentally during
the extraction of tannins for oak bark (Quercus frainetto Ten) - water system.
The kinetics of extraction was studied under periodical conditions in a stirred
vessel for internal diffusion limited regime. The mercury penetration method
was applied for measurement of the pore-size distributions in the range of
0.005-50 m. The samples were analysed before, during and after the extraction
process. From the comparison of the commulative distribution curves was demonstrated
that the relative volumes of the pore size are redistributed toward the smaller
pore region of the distribution curve with the advancement of the extraction.
As a result the internal porosity increases from =0.55 m3m-3 for initial fresh
material to =0.84 m3m-3 in the final equilibrium state. Three parametric power
function relating porosity evolution with the extraction time was found to
fit the experimental data.
Keywords: Solid-liquid extraction, Kinetics, Pore-size distribution,
Mercury porosimetry, Porosity, Vegetables.
