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Displacement Washing of non-Porous Particles
Authors: Pulcer Martin | Potůček František
Year: 2003
Type of publication: ostatní - přednáška nebo poster
Name of source: Int. Student's Seminar on Chemistry and Technology of Wood, Pulp and Paper
Publisher name: -*-
Place:
Page from-to:
Titles:
Language Name Abstract Keywords
cze Displacement washing; Dispersion model; Kraft pulp
eng Displacement Washing of non-Porous Particles In displacement washing, the mother liquor in the packed solids is displaced with clean water. The solute concentration in the bed is a function of time and the location in the bed. The experiments were carried out in the displacement washing cell consisting of a vertical glass cylinder 110 mm high, 35 mm inside diameter, and closed at the lower end by a permeable septum. The non-porous particles occupied the volume between the septum and a permeable piston. To start the washing experiment distilled water was distributed uniformly through the piston to the top of bed. At the same time the displaced liquor was collected at atmospheric pressure from the bottom of the bed via the septum. Samples of the washing effluent taken at different timed intervals until the effluent was colourless. All samples were analyzed for alkali lignin using an ultraviolet spectrophotometer operating at a wavelength of 295 nm. The washing cell was randomly packed with glass beads or glass rings. The height of packed bed was kept constant in all runs - 30 mm. The displacement washing process is characterized by: the Peclet number, the Reynolds number, the dispersion coefficient, wash yield, the mean residence time and the space time. Experimental data for displacement washing can be presented in the form of washing curves, which are plots of the dimensionless solute concentration versus the wash liquor ratio. Peclet number can be used as the similarity criterion for longitudinal mixing. It varies from zero for perfect mixing to infinity for plug flow. Reynolds number is defined for wash liquid flowing through the voids in a packed bed. The quality of the displacement washing can be characterized by the wash yield. The values of wash yield for glass rings obtained experimentally are grouped along to the theoretical dependence derived from the data reported from the special letter. The dependence between axial dispersion coefficient and superficial wash liquid velocity is linear and it is Displacement washing; Dispersion model; Kraft pulp

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