This study presents the results of an investigation of liquid flow and dispersion in the bulk and wall region as well as liquid dispersion in the whole cross-section in a packed column with and without counter-current gas flow. In the study a column of 30 cm in diameter packed with 2.54 cm Rashig rings was used. Water was uniformly distributed at the top while air was introduced and distributed uniformly at the bottom of the packed column. Using a point injector, an input pulse of sodium choride solution was introduced at the axis of the column through a small diameter injection tube at a bed height of 25 cm. The responses were measured at four radial positions, using conductivity cells attached to the supporting plate, and were recorded simultaneously with the input pulse, which was recorded as a pressure signal using a pressure transducer. The dispersion equation was solved analytically, and the axial and radial dispersion coefficients in the bulk region were estimated by a non-linear optimization technique. The values of interstitial liquid velocity in the bulk region were estimated from the first moment of the input and output pulses. A plane tracer injector was used to introduce an input pulse of sodium chloride solution to the whole cross section area of the column at bed height of 15 cm. The responses were measured at four radial positions, simultaneously using the four conductivity cells. The input pulse was recorded as a pressure signal. A dispersion equation was solved analytically and total dispersion coefficients were estimated by a non-linear optimization technique. The values of the interstitial liquid velocity in the bulk and wall region were estimated from the first moment on the input and output pulses. The responses in the bulk and wall region were used separately in a dispersion equation which was solved analytically to estimate the axial dispersion coefficients in the bulk and wall region respectively. The operation was repeated at eight different heights up to 150 cm, and the total dispersion coefficients were estimated at each height for different liquid and gas flow rates. The above results were used to study the validity of Gunn's (1980) theoretical analysis, which was based on the assumption that the total dispersion coefficients in a packed column has two important contributions, local dispersion in the packing and axial dispersion due to the differences in liquid flow conditions between the wall and bulk regions of packing. By this treatment, a two-dimensional formulation of dispersion may be reduced to a one-dimensional axisymmetric formulation of dispersion for the limit of long dispersion times. Good agreement between experiment and theory was found.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636015 |
| Date | January 1988 |
| Creators | Baker, S. A. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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