Mass Transfer and Flooding in Wetted-Wall and Packed Columns

Abstract

Catalytic fixed-bed tubular reactors can undergo severe temperature excursions, particularly when there is a drop in feed temperature. Several control strategies have been studied which attenuate temperature peaks that would occur in an uncontrolled reactor, A practical strategy is recommended which requires feeding a fraction of the reactants at an intermediate point along the reactor bed. A control algorithm which enablés the calculation of the secondary flow is proposed and its performance characteristics are evaluated by dynamic simulations. The proposed method is very effective in attenuating the temperature peaks, thus preventing catalyst deactivation and structural damage to the reactor.

Packed column efficiency fundamentals

“…The prior paper (Hughmark, 1980) presented a model for vapor-phase mass transfer in packings. The model is applicable to packings when the flow in the vapor phase is turbulent and, therefore, is restricted to packing sizes of 2.54 cm and larger.…”

“…This model combines the interfacial area with the mass transfer coefficient for each phase. Hughmark (1980) attempted to separate interfacial areas and the mass transfer coefficients so as to apply fundamental models to the latter. This work indicated that the liquid-phase mass transfer could be represented by the behavior of a turbulent falling film.…”