Time-dependent gas hold-up and bubble size distributions in a gas—highly viscous liquid—solid system

Generation of small bubbles and small bubble-liquid mass transfer in airlift reactors containing highly viscous liquids

“…Instead of this the large bubble hold-up (curve B) increases distinctly. These results are similar to those presented in the papers [6,11].…”

Generation of small bubbles and small bubble-liquid mass transfer in airlift reactors containing highly viscous liquids

“…Instead of this the large bubble hold-up (curve B) increases distinctly. These results are similar to those presented in the papers [6,11].…”

Influence of impeller type on hydrodynamics and gas‐liquid mass‐transfer in stirred airlift bioreactor

“…This could also confirm the accumulation of small bubbles on the wall of the bioreactor. According to Kawalec‐Pietrenko, the small bubbles relative contribution increases with the increase in the liquid viscosity; therefore, confirming our observations. In the center of the reactor, the region encompassed by the riser, there was the formation of coalescing bubbles caused primarily by the increased collision among the bubbles in this region, which is located in the gas sparger.…”

“…; Table ), the higher is the apparent viscosity, in other words, the gas holdup values decrease with an increase in degree of pseudoplasticity. The increase in the gas holdup fraction from the bioreactor column is directly related to the increase of the aeration and agitation imposed, the formation of small bubbles caused by aeration/agitation are usually generated by the following mechanisms: (1) during the coalescence process between the bubbles near the gas distributor plate, the trailing big bubble elongates causing its tail break up into small bubbles; (2) a large bubble breaking up at the surface of the liquid generates small bubbles; (3) small bubbles can be obtained by the creation of sufficient turbulence in the liquid to break up larger bubbles. This phenomenon also occurs when the gas flow rate is high; thus, causing a strong liquid circulation.…”

“…Experiments with CMC have also shown that a significant fraction of gas was retained in the bioreactor (Figure a); this retention is probably related to the fluid movement from the riser to the downcomer, aided mainly by the action of the impeller, which contributed, in part, for the bubbles to break up into smaller ones. Conversely, we also observed the formation of coalescing bubbles due to the partial restriction of bubbles movement caused by the high viscosity of the fluid, resulting in the decrease in the ascending rate of these bubbles, causing greater number of collisions between them, thus leading to their coalescence; these coalescing bubbles also contributed to the increase in gas holdup …”

Region-dependent oxygen transfer rate in the rectangular airlift reactor

“…This occurs because several of the relative big bubbles moving from the separator penetrated the downcomer still deeper. On the other hand a slight decrease of the downcomer mass transfer coef®cient with an increase of the liquid viscosity was observed (Table 2), because the number of the small bubbles of diameter smaller than 1 mm increased as the liquid viscosity increased [5]. Simultaneously with an increase of the liquid viscosity the large bubbles gas hold-up decreased.…”

Generation of small bubbles and small bubble-liquid mass transfer in airlift reactors containing highly viscous liquids

“…Instead of this the large bubble hold-up (curve B) increases distinctly. These results are similar to those presented in the papers [6,11].…”

Influence of impeller type on hydrodynamics and gas‐liquid mass‐transfer in stirred airlift bioreactor

“…This could also confirm the accumulation of small bubbles on the wall of the bioreactor. According to Kawalec‐Pietrenko, the small bubbles relative contribution increases with the increase in the liquid viscosity; therefore, confirming our observations. In the center of the reactor, the region encompassed by the riser, there was the formation of coalescing bubbles caused primarily by the increased collision among the bubbles in this region, which is located in the gas sparger.…”

“…; Table ), the higher is the apparent viscosity, in other words, the gas holdup values decrease with an increase in degree of pseudoplasticity. The increase in the gas holdup fraction from the bioreactor column is directly related to the increase of the aeration and agitation imposed, the formation of small bubbles caused by aeration/agitation are usually generated by the following mechanisms: (1) during the coalescence process between the bubbles near the gas distributor plate, the trailing big bubble elongates causing its tail break up into small bubbles; (2) a large bubble breaking up at the surface of the liquid generates small bubbles; (3) small bubbles can be obtained by the creation of sufficient turbulence in the liquid to break up larger bubbles. This phenomenon also occurs when the gas flow rate is high; thus, causing a strong liquid circulation.…”

“…Experiments with CMC have also shown that a significant fraction of gas was retained in the bioreactor (Figure a); this retention is probably related to the fluid movement from the riser to the downcomer, aided mainly by the action of the impeller, which contributed, in part, for the bubbles to break up into smaller ones. Conversely, we also observed the formation of coalescing bubbles due to the partial restriction of bubbles movement caused by the high viscosity of the fluid, resulting in the decrease in the ascending rate of these bubbles, causing greater number of collisions between them, thus leading to their coalescence; these coalescing bubbles also contributed to the increase in gas holdup …”

Region-dependent oxygen transfer rate in the rectangular airlift reactor

“…This occurs because several of the relative big bubbles moving from the separator penetrated the downcomer still deeper. On the other hand a slight decrease of the downcomer mass transfer coef®cient with an increase of the liquid viscosity was observed (Table 2), because the number of the small bubbles of diameter smaller than 1 mm increased as the liquid viscosity increased [5]. Simultaneously with an increase of the liquid viscosity the large bubbles gas hold-up decreased.…”

Generation of small bubbles and small bubble-liquid mass transfer in airlift reactors containing highly viscous liquids

“…Instead of this the large bubble hold-up (curve B) increases distinctly. These results are similar to those presented in the papers [6,11].…”

Influence of impeller type on hydrodynamics and gas‐liquid mass‐transfer in stirred airlift bioreactor

“…This could also confirm the accumulation of small bubbles on the wall of the bioreactor. According to Kawalec‐Pietrenko, the small bubbles relative contribution increases with the increase in the liquid viscosity; therefore, confirming our observations. In the center of the reactor, the region encompassed by the riser, there was the formation of coalescing bubbles caused primarily by the increased collision among the bubbles in this region, which is located in the gas sparger.…”

“…; Table ), the higher is the apparent viscosity, in other words, the gas holdup values decrease with an increase in degree of pseudoplasticity. The increase in the gas holdup fraction from the bioreactor column is directly related to the increase of the aeration and agitation imposed, the formation of small bubbles caused by aeration/agitation are usually generated by the following mechanisms: (1) during the coalescence process between the bubbles near the gas distributor plate, the trailing big bubble elongates causing its tail break up into small bubbles; (2) a large bubble breaking up at the surface of the liquid generates small bubbles; (3) small bubbles can be obtained by the creation of sufficient turbulence in the liquid to break up larger bubbles. This phenomenon also occurs when the gas flow rate is high; thus, causing a strong liquid circulation.…”

“…Experiments with CMC have also shown that a significant fraction of gas was retained in the bioreactor (Figure a); this retention is probably related to the fluid movement from the riser to the downcomer, aided mainly by the action of the impeller, which contributed, in part, for the bubbles to break up into smaller ones. Conversely, we also observed the formation of coalescing bubbles due to the partial restriction of bubbles movement caused by the high viscosity of the fluid, resulting in the decrease in the ascending rate of these bubbles, causing greater number of collisions between them, thus leading to their coalescence; these coalescing bubbles also contributed to the increase in gas holdup …”

Region-dependent oxygen transfer rate in the rectangular airlift reactor

“…This occurs because several of the relative big bubbles moving from the separator penetrated the downcomer still deeper. On the other hand a slight decrease of the downcomer mass transfer coef®cient with an increase of the liquid viscosity was observed (Table 2), because the number of the small bubbles of diameter smaller than 1 mm increased as the liquid viscosity increased [5]. Simultaneously with an increase of the liquid viscosity the large bubbles gas hold-up decreased.…”