Characterization of a pilot plant airlift tower loop bioreactor. I: Evaluation of the phase properties with model media

Abstract

Investigations were carried out in a 9 m high, 4 m(3) volume, pilot plant airlift tower loop bioreactor with a draft tube. The reactor was characterized by measuring residence time distributions of the gas phase using pseudostochastic tracer signals and a mass spectrometer and by evaluating the mixing in the liquid phase with single-pulse tracer inputs. The local gas holdup and the bubble size (piercing length) were measured with two-channel electrical conductivity probes. The mean residence times and the intensities of the axial mixing in the riser and downcomer and the circulation times of the phases as well as the fraction of the recirculated gas phase were evaluated. The gas holdup in the riser is nearly uniform along the reactor. In the downcomer, it diminishes from top to bottom. The liquid phase dispersion coefficients, D(L), are smaller than those measured in the corresponding bubble columns. In the pilot plant with tap water the following relationship was found: D(Lr) = cw(SG) (n); with c = 203.4; n = 0.5;D(Lr)(cm(2) s(-1);) and W(SG)(cm s(-1)) where D(Lr) is the longitudinal dispersion coefficient in the riser and W(SG) is the superficial gas velocity. The gas phase dispersion coefficients in the riser of the pilot plant, D(Gr), are also enlarged with increasing superficial gas velocity, W(SG), however, no simple relationship exists. Parameter D(Gr) is the highest in the presence of antifoam agents, intermediate in tap water, and the smallest in ethanol solution.

Mass transfer and mixing characteristics in an airlift‐driven fibrous‐bed bioreactor

“…At gas velocities >0.20 m s −1 , the influence of the gas velocity diminished. Similar results were also reported by Fröhlich et al (1991).…”

“…It is however interesting to see from Figure 8 that the Bo number for air–water system in the ILALB without packing increases consistently with increasing superficial gas velocity. Fröhlich et al (1991) have reported opposite effect of gas velocity on Bo number for air–tap water in 4 m 3 pilot plant airlift tower loop bioreactor without packing.…”

Concentric‐tube airlift reactors: Effects of geometrical design on performance

“…This correlation fits those data satisfactorily. The data by Frohlich et al (1991) are also well represented by Eq. 17.…”

Bioreactors: Airlift Reactors

“…Thus, this modification is especially suited to processes operating with cells immobilized on a solid. The minimal gas flow rate for complete fluidization of solids in an ALR may be reduced drastically by the use of a HFP (187). In addition, the mass transfer rate to suspended solids may be enhanced up to 50%, because of the higher relative velocity between the particles and solids.…”