Characterisation of impeller driven and oscillatory mixing by spatial and temporal shear rate distributions

Chew, Chun M.; Ristić, R. I.; Reynolds, Gavin K.; Ooi, R.C.

doi:10.1016/j.ces.2004.01.019

Cited by 18 publications

(16 citation statements)

References 23 publications

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“…Therefore, it is reasonable to postulate that a moving particle in OBBC is much more frequently exposed to some kind of a local alternating change of solution direction than a particle in IDBC. In order to validate this proposition, CFD was used to model the hydrodynamic conditions, and evaluate the shear rate distributions in IDBC and OBBC 18. Our modeling analysis shows the following main findings.…”

Section: Summary Of Different Methods Used In the Assessment Of Partimentioning

confidence: 83%

Crystallization by oscillatory and conventional mixing at constant power density

Chew¹,

Ristić²

2005

AIChE Journal

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The influence of mixing on crystallization processes has long been recognized. 1,2 The significance of mixing in crystallization is attributed to its role in the development and distribution of supersaturation, as well as the shear forces associated with the velocity field imposed by the impeller motion. These aspects of mixing are paramount to the quality of the precipitates (particles), often characterized by their crystal size distribution (CSD), surface characteristics, chemical purity, and crystalline imperfections (defect contents).Impeller driven stirred vessel has always been the prevalent choice in industrial crystallization for the production of pharmaceutics and specialty chemicals. However, in recent years, there has been an increasing interest in oscillatory flow mixing (OFM) as an attractive alternative mixing method, where intense eddy mixing is achieved in a baffled column by fluid oscillations. The attractiveness of this method lies in its performance enhancements over the conventional impeller-driven stirred vessel. This has been reported for processes such as heat-and mass-transfer, 3, 4 gas-liquid mixing, 5 and solid-liquid suspension. 6 However, a comparatively little attention has been paid to studies of this type of mixing on a possible improvement of the quality of precipitated particles, particularly in crystallization of low output high added-value products, such as pharmaceuticals, dyestuffs, catalysts and proteins.This article reports, for the first time, on the feasibility of OFM to improve the quality of pharmaceutical particles. For this purpose, paracetamol (4-acetaminophenol, 99ϩ%, Merck) was used as a model system.Experiments were conducted in parallel using a specially designed oscillatory baffled batch crystallizer (OBBC) ( Figure 1a) and classical impeller driven batch crystallizer (IDBC) (Figure 1b). The experiments were performed in both crystallizers under the same conditions of residence time ( r ϭ 30 min), temperature of crystallization (T ϭ 20°C), initial supersaturation (20 -50%), volume (500 mL) and power density (1.5 kW/m 3 ), but at distinctly different hydrodynamic environment. Paracetamol solution was prepared using the method previously described. 7 In each experiment, the solution was cooled down to a desired supersaturation before the agitation was initiated. The constant power density applied to both crystallizers was used as the reference criteria in these comparative studies. As we shall see later, this criteria is quite informative, because under the same conditions of residence time, temperature, initial supersaturation and volume of the two crystallizers, it enables us to assess the effectiveness of both mixing methods, in terms of quality of precipitated particles, for a given power input.The power density of IDBC was estimated by the PowerReynolds numbers correlation, which is common for most impeller driven systems; 8 while the power density of OBBC was estimated by the eddy acoustic model suitable for oscillations with frequencies and amplitudes in th...

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Section: Summary Of Different Methods Used In the Assessment Of Partimentioning

confidence: 83%

Crystallization by oscillatory and conventional mixing at constant power density

Chew¹,

Ristić²

2005

AIChE Journal

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“…Mumtaz's work has found applications in industrial crystallisation (Braun et al, 2004;Brunsteiner et al, 2005;Chen et al, 2004;Chen et al, 2003;Chew et al, 2004;Falk et al, 2011;Hollander et al, 2003;Ilievski, 2001;Ilievski and Livk, 2006;Kramer and Jansens, 2003;Li et al, 2001;Livk and Ilievski, 2007;Rielly and Marquis, 2001;Wang et al, 2006;Yokota et al, 1999;Zauner and Jones, 2000), precipitation (Lakshminarayanan and Valiyaveettil, 2003;Lewis and Mangere, 2011;Lindenberg et al, 2008;Lawler, 2008, 2010;Wagterveld et al, 2012;Wan et al, 2011), nanoprecipitation (Jia et al, 2008;Pujol et al, 2004;Schwarzer and Peukert, 2005;Schwarzer et al, 2006), population balance modelling (Balakin et al, 2012;Briesen, 2006;Briesen, 2007;Derksen, 2002;Hollander et al, 2001a;Hollander et al, 2002;Hollander et al, 2001b;Mersmann et al, 2002;Reinhold and Briesen, 2012;Sgraja et al, 2010) and colloid science (Gruy, 2012;Kind, 2002).…”

Section: ¼ Strength Of the Neck Hydrodynamic Disruptive Force ð1þmentioning

confidence: 98%

Aggregation of growing crystals in suspension: I. Mumtaz revisited

Hounslow

Wynn

Kubo

et al. 2013

Chemical Engineering Science

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“…15,16 Crystal product quality can be particularly sensitive to the shear rate distribution during crystallisation. 17,18 Chew et al, 18 investigated the shear rate distribution and flow patterns in a stirred tank and in a moving baffle oscillatory crystalliser (MBOC) using computational fluid dynamics (CFD). They showed that in an MBOC, particles spend most of their time in the high shear regions whilst in the STC/MSMPR particles reside mainly in regions of low shear.…”

Section: Introductionmentioning

confidence: 99%

Development and characterisation of a cascade of moving baffle oscillatory crystallisers (CMBOC)

et al. 2020

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Characterisation of impeller driven and oscillatory mixing by spatial and temporal shear rate distributions

Cited by 18 publications

References 23 publications

Crystallization by oscillatory and conventional mixing at constant power density

Crystallization by oscillatory and conventional mixing at constant power density

Aggregation of growing crystals in suspension: I. Mumtaz revisited

Development and characterisation of a cascade of moving baffle oscillatory crystallisers (CMBOC)

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