Scale-up of airlift-loop bioreactors based on modelling the oxygen mass transfer

Oxygen mass transfer and hydrodynamics in a multi-phase airlift bioscrubber system

“…This is an interesting result, as Nylon 6,6 was previously used as an inert control in a mechanically agitated TPPB to demonstrate that the addition of polymers into the bioreactor can result in the physical enhancement of gas-liquid mass transfer by increasing k L a eff (Littlejohns and Daugulis, 2007). However, the results of the current study are in agreement with Lindert et al (1992) who determined that the addition of polycarbonate beads of density 1241 kg m −3 and diameter 2.7 mm, which have a low affinity for oxygen, to an external loop airlift bioreactor had no significant impact on k L a eff relative to a bioreactor without polymers. It is speculated that this can be attributed to the high shear environment of the stirred tank relative to the airlift, resulting in physical enhancement due to the Nylon 6,6.…”

“…This assumption is consistent with other authors who have used a well-mixed model (Eq. (1)) to determine k L a in airlift vessels larger than the one in the current study (Lindert et al, 1992;Freitas and Teixeira, 2001;Guo et al, 1997).…”

“…In contrast to stirred tank vessels that are assumed to be well-mixed, airlift bioreactors can often have an axial variation of composition, particularly in the downcomer (Chisti, 1989). Hydrodynamic studies have shown that the presence of solids in threephase systems can have a neutral (Sánchez et al, 2005;Lindert et al, 1992) and positive (Comte et al, 1997;Lu et al, 1995) impact on mixing depending on the reactor geometry, solid size, solid density and solid loading.…”

Biomass Characteristics, Aeration and Oxygen Transfer in Membrane Bioreactors: Their Interrelations Explained by a Review of Aerobic Biological Processes

“…With fine particles, up to 0.01 mm, k L a increased with increasing solids concentration up to a certain level and remained stable before decreasing with further solids loading (Saba et al 1987;Smith & Skidmore 1990). With large particles, around 1-3 mm, an increase in the solids concentration led directly to a decrease in the k L a (Koide et al 1992;Lindert et al 1992;Komaromy & Sisak 1994;Hwang & Lu 1997;Nakao et al 1999). The behaviour of the mass transfer coefficient may also change when very large particles are used.…”

Design and Scale-up of External-Loop Airlift Bioreactor

“…Table 1 In order to avoid solids settling, the connection pipes between riser and downconer were inclined. This connection pipe configuration has been used previously by other investigators [2,3].…”