Countercurrent multistage fluidized bed reactor for immobilized biocatalysts: II. Operation of a laboratory‐scale reactor

Abstract

In Part I of this series,(1) we derived a model and made simulations for a multistage fluidized bed reactor (MFBR). It was concluded that the MFBR can be an attractive alternative for a fixed bed reactor when operated with a deactivating biocatalyst. In Part II of this series, the design of a laboratory-scale MFBR and its evaluation to investigate the practical feasibility of this reactor type, will be described. Experiments with a duration as long as 10 days were carried out successfully using immobilized glucose isomerase as a model reaction system. The results predicted by the model are in good agreement with the measured glucose concentration and biocatalyst activity gradients, indicating perfect mixing of the particles in the reactor compartments.The diameters of the biocatalyst particles used in the experiments showed a large spread, with the largest being 1.7 times the smallest. Therefore, an additional check was carried out, to make sure that the particles were not segregating according to size. Particles withdrawn from the reactor compartments were investigated using an image analyzer. Histograms of particle size distribution do not indicate segregation and it is concluded that the particles used have been mixed completely within the compartments. As a result, transport of biocatalyst is nearly plug flow.

Transient behavior of pulsed particulate fluidized beds

“…The contactor has two sections to facilitate the mounting of sieve plates. The system is equipped with a pulseless rotary gear pump, a magnetoinductive flowmeter, and a pulsation system as described by Vos et al (1990). The pulsation tube had a volume of 16 mL and contained a polypropylene float that was used to activate the two optical sensors determining the pulsation volume.…”

“…Depending on the frequency and magnitude of the flow-reversal and refluidization cycles, transient phenomena may play an important role in determining both the maximum flow rate and effective holdup of the solids. Applications of pulsed multistage liquid fluidized-bed contactors have been described for continuous ion exchange (Streat, 19801, continuous adsorption of biomolecules (Van der Wiel and Wesselingh, 1988), and as continuous reactor for deactivating biocatalysts (Vos, 1990). Recently, the application of this concept as countercurrent adsorptive reactor, in which selective countercurrent transport of dense adsorbent particles was combined with the retention of a lighter biocatalyst phase, was proposed (van der Wielen et al, 1990).…”