The stage efficiency in dynamic models of phase separation processes

• Published in: Chemical engineering science 1973-01, Vol.28 (12), p.2223-2229
• Main Author: Asbjørnsen, O.A.
• Format: Article
• Language: English
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/0009-2509(73)85011-0

In chemical engineering practice, deviation from a perfectly mixed equilibrium stage in phase separation processes is described by a stage efficiency. In dynamic models this parameter is in most cases meaningless, except when the deviation from equilibrium is caused by interfacial transport resistance. The present paper shows that when this resistance approaches zero, there is an eigenvalue related to the interfacial transport that goes to − ∞. The response mode attached to this eigenvalue expresses the deviation from equilibrium. Approximationg this mode by zero, may be defined as a “pseudo-equilibrium”. In a dynamic sense, the stage efficiency has a proper meaning only in this case, but it should be emphasized that this state space reduction is an approximation valid only for moderate deviations from true equilibrium. Hence, the stage efficiency has a much more narrow range of sound application than is usually considered in the chemical engineering literature.