Instability phenomenon in an external-loop three-phase gas-liquid-solid airlift reactor
- Imperial College, London (United Kingdom). Dept. of Chemical Engineering and Chemical Technology
Three-phase airlift (TPAL) reactors have applications ranging from biotechnology to catalytic hydrogenation. Circulation in a loop consisting of a riser and downcomer with top and bottom connections is induced by injecting gas at the bottom of the riser. The continuous liquid phase recirculates up the riser and down the downcomer, carrying the solid phase in suspension. A hydrodynamic model was developed for TPAL reactors which enables the prediction of main variables of a TPAL reactor (phase holdups and liquid recirculation velocity) as a function of the inlet gas superficial velocity and the solids loading. This model considers a TPAL reactor to comprise riser and downcomer sections alone; the difference in the effective densities between these regions gives rise to the recirculation. As part of a program of experimental work aimed at verifying this model, it was decided to carry out experiments on an external-loop reactor which would generate direct measurements of the required riser and downcomer hydrodynamic parameters. During the course of these experiments, however,a surprising and before now unreported instability phenomenon was observed. This behavior prevented the system from reaching a steady distribution of solids. In general, instabilities are undesirable since they could adversely affect the system control and performance. The objective of this article is to describe the observed phenomenon and attempt to explain why it occurs.
- OSTI ID:
- 131892
- Journal Information:
- AIChE Journal, Vol. 41, Issue 11; Other Information: PBD: Nov 1995
- Country of Publication:
- United States
- Language:
- English
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