Scale airlift reactor

No general correlations for kLa are available for EL airlift reactors. However, it has been suggested [28] that, before a production-scale airlift reactor is built, experiments are performed with an airlift which has been scaled-down from a production-scale airlift designed with presently available information. The final... 

The external-loop slurry airlift reactor was used in a pilot plant (3000 t/a) for one-step synthesis of dimethyl ether (DME) from syngas. Specially designed internals were used to intensify mass transfer and heat removal. This new technology is highly efficient and easy to scale-up to industrial. 

Eulerian two-fluid model coupled with dispersed itequations was applied to predict gas-liquid two-phase flow in cyclohexane oxidation airlift loop reactor. Simulation results have presented typical hydrodynamic characteristics, distribution of liquid velocity and gas hold-up in the riser and downcomer were presented. The draft-tube geometry not only affects the magnitude of liquid superficial velocity and gas hold-up, but also the detailed liquid velocity and gas hold-up distribution in the reactor, the final construction of the reactor lies on the industrial technical requirement. The investigation indicates that CFD of airlift reactors can be used to model, design and scale up airlift loop reactors efficiently. 

Biomass containment in continuously operated bioreactors is an essential prerequisite for the feasibility of practical industrial-scale dye biodegradation. Biofilm airlift reactors have demonstrated excellent performance for their ability to control mixing, interphase mass transfer and biofilm detachment rate. Further studies are required to further exploit the potential of this type of reactors with either aggregated cells or biofilm supported on granular carriers. 

Bubble columns and various modifications such as airlift reactors, impinging-jet-reactors, downflow bubble columns are frequently used in lab-scale ozonation experiments. Moderate /qa-values in the range of 0.005-0.01 s l can be achieved in simple bubble columns (Martin et al. 1994 Table 2-4 ). Due to the ease of operation they are mostly operated in a cocurrent mode. Countercurrent mode of operation, up-flow gas and down-flow liquid, has seldom been reported for lab-scale studies, but can easily be achieved by means of applying an internal recycle-flow of the liquid, pumping it from the bottom to the top of the reactor. The advantage is an increased level of the dissolved ozone concentration cL in the reactor (effluent), which is especially important in the case of low contaminant concentrations (c(M)) and/or low reaction rate constants, i. e. typical drinking water applications... 

M.H. Siegel, J.C. Merchuk, Hydrodynamics in rectangular airlift reactors scale-up and the influence of gas-liquid separator design, Can. J. Chem. Eng. 69 (1991) 465 173. 

A major study should be attempted to compare the different bioreactor performance characteristics. Comparisons between BCs and airlift reactors are available, but a wider array is lacking, but needed. Research towards this end, such as Bouaifi et al. (2001) who compared stirred-tank reactors and BCs, is sparse. Different bioreactor designs have quite unique scaling abilities and associated costs, and the economic benefits and decisions would be better understood if such studies would be more common. 

Blazej, M., Kisa, M., and Markos, J. (2004c), Scale influence on the hydrodynamics of an internal loop airlift reactor, Chemical Engineering and Processing, 43(12) 1519-1527. 

Cai, J., Nienwstad, T.J., and Kop, J.H. (1992), Flnidization and sedimentation of carrier material in a pilot-scale airlift internal-loop reactor, Water Science <6 Technology, 26(9-11) 2481-2484. 

A problem with in vitro cultured hybridomas is low antibody 5deld, typicalfy in the range 20-100 mg/litre compared to the ascites in vivo route of 5-10 g/litre. Regulation in the use of experimental animals in many countries now means that the ascitic route is not an option, but to put matters in perspective 1 g of mAb obtainable from 100 mice can be produced in 10-20 litres of culture. This difference can be dramatically reduced if perfusion systems with high ceU densities (over 5 X 10 /ml) are used. When mAbs are needed for research or diagnostic purposes then batches up to only 200 mg are needed and this can be achieved in 2-5 litres of culture. However for in vivo diagnostics and therapeutics where batch sizes of 10-100 g are required then the scale-up to fermenter/airlift reactor or perfusion systems is a necessity. 

Even though these special application examples demonstrate the scalability of the technology, and although airlift reactors have long been used for shear-sensitive cell-culture applications, the CSTR design has become the standard for microbial and mammalian cell suspension culture. Its design is versatile, and cultivations can be scaled from the laboratory to pilot scale and to up to 300 m in fully contained sterile fermenters. 

Tijhuis L, Hijman B, van Loosdrecht MCM, Heijnen JJ (1996) Influence of detachment, substrate loading and reactor scale on the formation of biofilms in airlift reactors. Appl Microbiol Biotechnol 45 7-17 Torsvik V, Goksoyr J, Daae FL (1990) High diversity in DNA of soil bacteria. Appl Environ Microbiol 56 782-787... 

Finally, according to Van der Roest, the project manager at the engineering firm DHV, the decision to opt for the bubble column reactor was made by DHV and DHV had to convince Van Loosdrecht to abandon the airlift reactor, who did so only reluctantly. From the point of view of Van der Roest, if it had not been for DHV to abandon the airlift reactor the aerobic GSBRs would never have come to the commercial market. According to Van der Roest, he had to challenge the scientists to adapt the process for practical purposes. He had to make the scientists aware that on real scale the oxygen concentration would be lower than in the laboratory because of restrictions on pump capacity. From the perspective of the Kluyver Lab it was... 

Airlift loop reactor (ALR), basically a specially structured bubble column, has been widely used in chemical industry, biotechnology and environmental protection, due to its high efficiency in mixing, mass transfer, heat transfer etc [1]. In these processes, multiple reactions are commonly involved, in addition to their complicated aspects of mixing, mass transfer, and heat transfer. The interaction of all these obviously affects selectivity of the desired products [2]. It is, therefore, essential to develop efficient computational flow models to reveal more about such a complicated process and to facilitate design and scale up tasks of the reactor. However, in the past decades, most involved studies were usually carried out in air-water system and the assumed reactor constructions were oversimplified which kept itself far away from the real industrial conditions [3] [4]. 

Roller bottle reactors have been widely used in the past and can generate cell densities upto 5.4 x 10 cells/ml.However, roller bottles are difficult to scale up and cannot meet the growing demand for therapeutic recombinant proteins. Their popularity is on the decline and are largely replaced by microcarriers, and stirred-tank or airlift bioreactors in process scale-up. Initially, industrial production of EPO by CHO cells is carried out in hundreds of roller bottles in incubation rooms equipped with robots for medium changes and product harvesting. The newer production plant for second-generation EPO employs state-of-the-art bioreactors and has three times the production capacity of the old EPO plant. 

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