Characterization of a pilot plant airlift tower loop bioreactor: II. Evaluation of global mixing properties of the gas phase during yeast cultivation

Fröhlich, S.; Lotz, Martin; Korte, Thomas; Lübbert, Α.; Schügerl, K.; Seekamp, M.

doi:10.1002/bit.260371003

Cited by 11 publications

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“…Many studies of laboratory and pilot scale [7,10,22,30] airlift reactors have considered the hydrodynamics and oxygen transfer but few have examined the impact of the circulatory flow on the metabolism of fermentation cultures. For airlift operation air is introduced into one section of the vessel and bubbles are entrained into the downcomer when the superficial liquid velocity of the downcomer exceeds the rise velocity of the bubbles [27,30].…”

Section: Introductionmentioning

confidence: 99%

Influence of a propeller on Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor

Pollard

Ison

Shamlou

et al. 1997

Bioprocess Engineering

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The hydrodynamics (sectional gas holdup and liquid velocities) and oxygen transfer performance of a conventionally operated multiconfigurable pilot scale (0.25 m 3 ) concentric airlift bioreactor containing baker's yeast were significantly improved by operating a marine propeller to draw liquid down the draft tube and aid recirculation at the base of the vessel. Propeller operation reduced the severe DOT heterogeneity of the reactor, which gave DOT values below 1% air saturation in the riser, by producing DOTs above 40% around the vessel at maximum energy dissipation rate. As a consequence the overall oxygen uptake rate (OUR) of the baker's yeast increased up to 3 fold with the total energy dissipation rate into the reactor until the lowest DOTs of the vessel were at or above 10%. The different degrees of heterogeneity generated by the two reactor configurations enabled the reactor to be used as a scale down tool to study the impact of heterogeneity on the physiology of fermentation broths. Comparison of the hydrodynamics and oxygen transfer between tall and short reactor heights revealed that the faster circulation times of the short reactor produced a greater improvement in the OUR with propeller operation even though similar DOT changes occurred around both sizes of reactor. This indicated that the yeast cells were responding to the rapid DOT changes around the vessel. List of symbolsA D cross sectional area of the downcomer m 2 A R cross sectional area of the riser m 2 D p propeller diameter m DCW dry cell weight g/l DOT dissolved oxygen tension % air saturation g acceleration due to gravity m/s 2 H D height of the gas -liquid dispersion from the vessel base m H DT height of the top of the draft tube from the vessel base m k L a volumetric mass transfer coefficient s -1 L clearance between the bottom of the draft tube and vessel base m N propeller speed s )1 OUR oxygen uptake rate mmol/l.h P A energy dissipation rate for airlift aeration only operation W/m 3 P g energy dissipation for airlift operation W P IN pressure at the point of gas inlet to the vessel Pa P P energy dissipation rate for propeller only operation W/m 3 P O propeller power number -P T total energy dissipation rate for combined airlift and propeller operation W/m 3 t c liquid circulation time s t m mean mixing time to achieve 90% homogeneity s U LD mean liquid linear velocity in the downcomer m/s U LR mean liquid linear velocity in the riser m/s U sg superficial gas velocity in riser m/s V L liquid volume m 3 L density of liquid kg/m 3 w density of water kg/m 3 gas holdup -D mean downcomer gas holdup -O mean overall gas holdup -R mean riser gas holdup -TS mean top section gas holdup -1 Introduction Many studies of laboratory and pilot scale [7, 10, 22, 30] airlift reactors have considered the hydrodynamics and oxygen transfer but few have examined the impact of the circulatory flow on the metabolism of fermentation cultures. For airlift operation air is introduced into one section of the vessel and bubbles are entrained into the downcomer wh...

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Section: Introductionmentioning

confidence: 99%

Influence of a propeller on Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor

Pollard

Ison

Shamlou

et al. 1997

Bioprocess Engineering

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“…The study of transport phenomena at pilot plant scale may aid the translation of scale up for airlift reactors as a large number of publications involved bench scale studies [25]. Frohlich et al [9] provided information on mixing and gas distribution at pilot scale (4 m3). They showed with baker's yeast broths that local gas holdup, bubble size, and bubble velocity changed only slightly along the length of the riser but, no information on oxygen transfer was given.…”

Section: List Of Symbolsmentioning

confidence: 99%

“…For both sparger configuration the difference of the riser and downcomer gas holdups was small. Frohlich et al [9] used helium pulse techniques to study the gas distribution in a 6.8 m tall reactor with a A D /A R of 0.535 and perforated ring sparger. Lubbert et al [12] showed that during baker's yeast fermentations there was only a few percent difference between the riser and downcomer gas holdup of a pilot scale concentric airlift reactor and a DOT of 70% in the middle downcomer position compared to below 1% in the riser.…”

Section: Oxygen Transfer Ratementioning

confidence: 99%

“…As k L a is strongly influenced by the specific interfacial area [33] then the smaller bubbles in the downcomer, as observed by Frohlich et al [9] and Bukur and Patel [5], would enhance oxygen transfer. As k L a is strongly influenced by the specific interfacial area [33] then the smaller bubbles in the downcomer, as observed by Frohlich et al [9] and Bukur and Patel [5], would enhance oxygen transfer.…”

Section: Oxygen Transfer Ratementioning

confidence: 99%

“…w density of water (kg · m\3) solubility in fermentation medium compared with that in water at same conditions (9) gas holdup (9) D means downcomer gas holdup (9) 0 mean overall gas holdup (9) R mean riser gas holdup (9) TS mean top section gas holdup (9) 1 Introduction The position of greatest oxygen transfer rate in the downcomer was shown to be affected by the reactor from the influence on downcomer liquid linear velocity.…”

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Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor: Comparison of air sparger configurations

Pollard¹,

Shamlou²,

Lilly³

et al. 1996

Bioprocess Engineering

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Hydrodynamic and oxygen transfer comparisons were made between two ring sparger locations, draft tube and annulus, in a concentric pilot scale airlift reactor with a baker's yeast suspension. Sectional hydrodynamic measurements were made and a mobile DOT probe was used to characterise the oxygen transfer performance through the individual sections of the reactor.The hydrodynamic performance of the reactor was improved by using a draft tube ring sparger rather than the annulus ring sparger. This was due to the influence of the ratio of the cross sectional area of the downcomer and riser (A D /A R ) in conjunction with the effect of liquid velocity and a parameter, C 0 , describing the distribution of the liquid velocity and gas holdup across the riser on the bubble coalescence rates.The mixing performance of the reactor was dominated by the frequency of the passage of the broth through the end sections of the reactor. An optimum liquid height above the draft tube for liquid mixing was demonstrated, above which no further improvement in mixing occurred. The liquid velocity and degree of gas entrainment showed little dependency on top section size for both sparger configurations.Extreme dissolved oxygen heterogeneity was demonstrated around the vessel with both sparger configurations and was shown to be detrimental to the oxygen uptake rate of the baker's yeast. Dissolved oxygen tensions below 1% air saturation occurred along the length of the riser and then rose in the downcomer. The greater oxygen transfer rate in the downcomer than in the riser was caused by the combined effects of a larger slip velocity in the downcomer which enhanced k L a and gas residence time, high downcomer gas holdup, and the change in bubble size distribution between the

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Agriculture wastes. A source of bulk products?

Schügerl

1994

Chem Eng & Technol

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Biotechnological production processes for low-molecular bulk chemicals can only compete with their petrochemical counterparts on using inexpensive raw materials, e.g., agricultural by-products or wastes, otherwise requiring disposal. The upgrading of by-products/wastes of potato starch production and the use of potato protein liquor and potato pulp for the production of bulk chemicals were investigated. It transpired that the economy of these processes depends on the waste disposal costs of the upgrading processes. In addition, it is shown that specialty chemicals can be produced economically from wastes. However, since they are produced in a large quantities, the upgraded product cannot be put on the market without ruining existing prices.

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Characterization of a pilot plant airlift tower loop bioreactor: II. Evaluation of global mixing properties of the gas phase during yeast cultivation

Cited by 11 publications

References 0 publications

Influence of a propeller on Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor

Influence of a propeller on Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor

Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor: Comparison of air sparger configurations

Agriculture wastes. A source of bulk products?

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