A new simple approach for the scale-up of aerated stirred tanks

Nauha, Elina K.; Visuri, Olli; Vermasvuori, Raisa; Alopaeus, Ville

doi:10.1016/j.cherd.2014.10.015

Cited by 30 publications

(23 citation statements)

References 44 publications

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“…Nowadays in several process industries, Computational Fluid Dynamics (CFD) is routinely used for the scale-up of equipment. Stirred tanks are a common example, such as those used as reactors and bioreactors (Nauha et al, 2015). However, despite the fact that the pulp zone in mechanical flotation cells is to some extent analogous to stirred tank systems, there are no publications on the use of CFD for flotation tank scale-up.…”

mentioning

confidence: 99%

“…In Chemical Engineering, the design and scale-up of continuous stirred-tank reactors (CSTR) is a problem that has been extensively studied (Evangelista et al, 1969;Nienow, 1997;Nauha et al, 2015). When designing a CSTR, the recommended engineering approach involves defining the process mixing requirements and then finding the appropriate impeller type to meet that requirement, depending on the fluid system (Paul et al, 2004).…”

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confidence: 99%

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Scale-up in froth flotation: A state-of-the-art review

Mesa

Brito-Parada

2019

Separation and Purification Technology

104

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Froth flotation has been one of the most important and widely used methods to concentrate minerals since its introduction over a hundred years ago. Over the last few decades, in order to process more mineral while reducing capital costs, flotation equipment has become exponentially larger. The increase in tank volume, however, has brought new challenges in the operation and design of industrial flotation tanks. This review analyses the literature on flotation tank scale-up for the first time, contrasting several techniques and approaches used in both historical and state-ofthe-art research. The study of flotation scale-up is crucial for the optimisation of industrial plant performance and the maximisation of laboratory-scale research impact. While important advances in our understanding of flotation have been achieved, large flotation tank design and scale-up has, to a large extent, remained in-house know-how of manufacturing companies. This review of the literature relevant to flotation tank scale-up has resulted in a new classification, dividing the scale-up literature into two main areas of study, namely "Kinetic scale-up" and "Machine design scale-up".This review indicates that current scale-up rules governing the design of flotation tanks focus mainly on pulp zone kinetic parameters and neglect the effects on the froth zone, despite the importance of froth stability and mobility in determining flotation performance. Froth stability and mobility are closely linked to the distance the froth needs to travel, which increases with tank diameter. Although including internal elements, such as launders and crowders, has been the industrial solution for enhancing froth transport and recovery in larger tanks, the design and scale-up of these elements have not been thoroughly studied. Gaps in our knowledge of flotation are discussed in the context of addressing the scale-up problem, considering froth transport and froth stability. Addressing these gaps will pave the way for the design and operation of large flotation tanks of enhanced performance.

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confidence: 99%

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confidence: 99%

Scale-up in froth flotation: A state-of-the-art review

Mesa

Brito-Parada

2019

Separation and Purification Technology

104

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“…In the current work cladribine scaling‐up biotransformation was evaluated using two prototypes (batch and packed‐bed) using previously optimized conditions for the immobilized biocatalyst. Batch configuration is, due to the simple setup, the equipment flexibility and the ease of operation, the most commonly used reactor set‐up . Packed‐bed reactors represent an alternative set‐up and among the advantages over a stirred tank, possible and problems of mechanical shear forces are eliminated and separation of the enzyme from the product is simplified.…”

Section: Resultsmentioning

confidence: 99%

Biotransformation of cladribine using a stabilized biocatalyst in calcium alginate beads

Lapponi

Britos

Rivero

et al. 2019

Biotechnology Progress

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Cladribine is a nucleoside analogue widely used in the pharmaceutical industry for the treatment of several neoplasms, including hairy‐cell leukemia among others. This compound has also shown efficacy in the treatment of autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. In this work, a green bioprocess for cladribine biosynthesis using immobilized Arthrobacter oxydans was developed. The microorganism was stabilized by entrapment immobilization in the natural matrix alginate. Different reaction parameters were optimized obtaining a biocatalyst able to achieve cladribine bioconversion values close to 85% after 1 hr, the shortest reaction times reported so far. The developed bioprocess was successfully scaled‐up reaching a productivity of 138 mg L−1 hr−1. Also, the biocatalyst was stable for 5 months in storage and in 96 hr at operational conditions.

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“…The value of b and c varies from 0.2 -0.7 (Moucha et al, 2003;Nienow et al, 1997) in literature, for example Table 1 shows some reported values for c with different . Nauha et al (2015) actually produce a double fit for the hold-up across superficial gas velocity, which defines clear difference between the two regimes. The rate of increase in hold-up reduces at the higher superficial gas velocities; however, even with this the hold-up is over predicted at the higher superficial gas velocities.…”

Section: Frmentioning

confidence: 99%

“…However this small-scale work does not reflect the increased energy input of the gas on the large scale and is only indicative of operation in the homogeneous (bubble regime) whereas large scale operation is generally in the heterogeneous (churn-turbulent) regime. In a recent study (Nauha et al, 2015), for the same reasons mentioned it was reported that scaling up by constant VVM will produce different hydrodynamic conditions in different scales and is therefore not recommended.…”

Section: Introductionmentioning

confidence: 99%

Gas–liquid mixing in dual agitated vessels in the heterogeneous regime

Jamshed

Cooke

Ren

et al. 2018

Chemical Engineering Research and Design

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Gas-liquid multi-phase processes are widely used for reactions such as oxidation and hydrogenation. There is a trend for such processes to increase the productivity of the reactions, one method of which is to increase the gas flow rate into the vessel. This means that it is important to understand how these reactors perform as high gas flow rates occurs well into the heterogeneous regime. This paper investigates the mixing performance for the dual axial radial agitated vessel of 0.61 m in diameter. 6 blade disk turbine (Rushton turbine) below a 6 Mixed flow Up-pumping and down-pumping have been studied at very high superficial gas velocities to understand the flow regimes operating at industrial conditions. Electrical Resistance Tomography have been used to produce the 3D images using Matlab, along with analysing the mixing parameters such as Power characteristics, gas holdup and dynamic gas disengagement. Minimal difference between the two configurations have been reported in terms of gas holdup , however with the choice of upward and downward pumping impeller power characteristics show significant difference at very high gas flow rates. Also at these high superficial gas velocities, this report introduces a 3rd bubble class, as seen in dynamic gas disengagement experiments, which corresponds to very large slugs of gas. Highlights  At high gas flow rates, a maximum holdup is observed  Power for 6MFD/6MFU problematic at high gas flow rates  The gas liquid holdup results show minimal difference between the two configurations  Large slugs observed as a third bubble classes at very high gas flow rates Keywords Gas-liquid mixing; Gas HoldUp ; Gassed Power; Heterogeneous regime; Axial-radial dual system; Electrical Resistance Tomography V Volume [m 3 ] Volume of dispersion [m 3 ] Volume of liquid [m 3 ] Volume of gas [m 3 ] Superficial gas velocity [m s-1 Greek symbols Gas Holdup [%] Specific total energy input per liquid mass [W kg-1 ] Σ Conductivity (normalised) [mS cm-1 ] Density of fluid [kg m 3 ] Dimensionless numbers

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A new simple approach for the scale-up of aerated stirred tanks

Cited by 30 publications

References 44 publications

Scale-up in froth flotation: A state-of-the-art review

Scale-up in froth flotation: A state-of-the-art review

Biotransformation of cladribine using a stabilized biocatalyst in calcium alginate beads

Gas–liquid mixing in dual agitated vessels in the heterogeneous regime

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