Page 29 - Academic Press Encyclopedia of Physical Science and Technology 3rd Chemical Engineering

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Encyclopedia of Physical Science and Technology EN001-13 May 25, 2001 21:6

Adsorption (Chemical

Engineering)

Douglas M. Ruthven
University of Maine

I. Forces of Adsorption
II. General Applications
III. Microporous Adsorbents
IV. Adsorption Equilibrium
V. Adsorption Kinetics
VI. Adsorption Column Dynamics
VII. Cyclic Batch Adsorption Processes
VIII. Chromatographic Processes
IX. Continuous Countercurrent Processes

GLOSSARY reflecting the difference in the flow pattern, but there is
a well-defined relationship between the two quantities.
Breakthrough curve Plot showing variation of outlet Knudsen diffusion Mechanism of diffusion, dominant in
concentration of one (or more) of the adsorbable smaller macropores at relatively low pressures, when
species with time. collisions between diffusing molecules and pore walls
Carbon molecular sieve Microporous carbon adsorbent occur more frequently than collisions between the
˚
that has very small micropores (typically ∼5.0-A di- molecules themselves.
ameter) with a very narrow distribution of pore size. Langmuir isotherm or model Simple mathematical rep-
Extract Product stream containing the more strongly ad- resentation of a favorable (type I) isotherm defined by
sorbed species. Eq. (2) for a single component and Eq. (4) for a binary
HETP Height equivalent to a theoretical plate. A measure mixture. The separation factor for a Langmuir system
of the combined effects of axial mixing and finite mass is independent of concentration. This makes the ex-
transfer resistance in causing deviations from ideal pression particularly useful for modeling adsorption
(equilibrium) behavior in a chromatographic column column dynamics in multicomponent systems.
or in a countercurrent contact system. The definitions LUB Length of unused bed. See Eq. (25) and Fig. 9 for a
of HETP in these two cases are somewhat different, precise definition.

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