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University of Leeds Paper on ATR Mixing Efficiency Characterisation

AM Technology are pleased to share news of a publication in "Chemical Engineering and Processing - Process Intensification" describing work performed collaboratively between the University of Leeds and AM Technology as part of an IbD project, entitled: Physical and numerical characterisation of an agitated tubular reactor (ATR) for intensification of chemical processes.

Please find a link to the publication here:

Logos for the University of Leeds, IbD and AM Technology

The abstract of the paper states:

"This study investigates the dynamics of a novel, oscillatory, intensified plug-flow reactor – an agitated tubular reactor (ATR) – designed for efficient flow processing of solid-liquid mixtures. The relative movement of the reactor and agitator bar, and associated effects on fluid mixing were characterised physically with a suite of experimental instruments – utilising laser-based, video-based and acoustic techniques – and numerically via a Lattice Boltzmann method (LBM) computational fluid dynamic simulation. The reactor volume consisted of a cylindrical outer tube containing a free-moving, perforated agitator tube. The position, velocity and angular velocity of the inner agitator relative to the outer tube were measured experimentally and computationally under a range of realistic operating conditions, in terms of applied agitation frequency and displacement distance, along with their effect on the associated fluid velocity and turbulence levels. Additionally, simulations were used to validate a model for the reactor power input. The agreement between experimental and simulation data were very good in all cases, leading to clear recommendations for optimal operating conditions, while an experimentally derived regime map of the types and magnitudes of ATR motion is also presented."

Active mixing is a vital component of Coflore flow reactors and is key to offering a viable continuous alternative to traditional batch reactors with regard to versatility and simplicity of operation. The unique mixing characteristics of the Coflore ATR stem from the use of radial mechanical stirring rather than passive or diffusive mixing. This approach decouples plug flow and mixing from residence time, to give very low dispersion numbers, fast blending, and high shear across a large range of residence times from seconds to hours.

Figure 1, reprinted from the publication, shows an example of the agitator motion within an ATR reactor tube at an agitation frequency of 3 Hz, with the three 2D slices displaying the velocity field at different relative positions of the agitator. The researchers concluded that the process fluid is well coupled to the ATR agitator and that the agitator motion generates fluid wakes within the perforated holes located along the length of the agitator, creating small regions of high fluctuating velocities where shear mixing will be enhanced. The researchers went on to state that the regions "are expected to cause higher levels of micro-mixing, despite relatively low peak Reynolds numbers."

Figure 1: Reprinted from the publication. Simulation of ATR fluid velocity as a 2D slice, in reference frame of outer (i.e. mechanically driven) tube, in which inner agitator is (a) to left, (b) at middle and (c) to right of extremities of its movement. Amplitude a = 11.2 mm, frequency f = 3.13 Hz. Velocity scale is m/s.

Further work performed by the group investigated the effect of suspended solid particles on fluid and agitator dynamics (section 3.3 in the publication), which will be of particular interest to many existing and future Coflore users, due to the Coflore range of flow reactors being the market leader for heterogenous multiphasic chemistry in flow thanks to their exceptional slurry handling capabilities. Real-World examples of slurry handling in Coflore systems can be found in the literature here, here and here.

We extend our gratitude to the team at the University of Leeds for their excellent work characterising the mixing efficiency of the ATR and look forward to future collaboration. We also wish to mention AMT's own Andrew Karras for being named as an author on the publication, congratulations Andrew!!


“One of today's most important tools for modernizing the pharmaceutical industry is a process known as continuous manufacturing”

Director of the FDA’s Centre for Drug Evaluation and Research,

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