ISSN:
0178-515X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract The gas-residence time distribution (RTD) response curves measured in a 23 m high pilot plant airlift tower loop reactor, which consisted of a riser, a special downcomer construction and at the top of the riser a large head. The measurements were evaluated by means of a deterministic dispersion model, which yielded the following particular parameters for the riser, downcomer and the head: Gas–Bo numbers, gas-mean residence times, gas holdups, liquid velocities, gas and liquid circulation times as well as a fraction of the large and small bubbles in a model medium (water) and during cultivation of baker’s yeast. List of symbols A cross section Bo Bodenstein number Bo d (=l d w G,d/D d) Bo h (=l h w G,h/D h) Bo r (=l r w G,r/D r) D longitudinal dispersion coefficient E gas holdup E(t) RTD-density function L, l length parameter q fraction of the gas throughput which is not recirculated (approximately equal to fraction of the large bubbles) r fraction of the throughput which is recirculated (approximately equal to the fraction of the small bubbles) t c circulation time t cL liquid circulation time t * c,L liquid circulation time calculated from the measured w Ld in the downcomer V h hydrodynamical calculated gas–liquid volume V h d (=V d+0.75/2V k) V h k =(0.25V k) V h r =(V r+0.75/2V k) V L liquid volume V G dispersed gas volume V * G gas throughput at the gas distributor (given in m3/h) under standard conditions, 1 bar and 25°C) V * G,d gas throughput in downcomer (=V * Gα) V * G,h gas throughput in head (=V * G) V * G,r gas throughput in riser (V * G (1+α) w G gas velocity w G,rel relative gas velocity with respect to the liquid velocity w L w G,d gas velocity in the downcomer (=w G,rel−w Ld) w G,h gas velocity in the head (=w G,rel) (since w Lh=0) w G,r gas velocity in the riser (=w G,rel+w Lr) w L liquid velocity w L,d liquid velocity in the downcomer measured with mass flow meter w SG ⋅ w SL superficial gas and liquid velocities μ first moment of the response curve τ mean residence time Indices d downcomer G gas phase h head L liquid phase r riser h hydrodynamic (upper position)
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00518737
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