Mixing performance comparison of milliscale continuous high‐shear mixers

Abstract

Mixing performance of two continuous flow millilitre-scale reactors (volumes 9.5 mL and 2.5 mL) equipped with rotor-stator mixers was studied. Cumulative residence time distributions (RTD) were determined experimentally using a step response method. Distributions were measured for both reactors by varying impeller speed and feed flow rate. The mixing effect was determined by measured RTDs. Computational fluid dynamics (CFD) were used to verify that the residence time distribution in the measurement outlet agreed with the outlet flow. The mixing power of both reactors was determined using a calorimetric method. The reactor inlet flow rate was found to affect mixing performance at 1-13 s residence times but the effect of impeller speed could not be noted. Both milliscale reactors are close to an ideal continuous stirred-tank reactor (CSTR) at the studied impeller speed and flow rate ranges. The specific interfacial area was found to depend on the reactor inlet flow rate at constant impeller speed for the case of copper solvent extraction.

Structural Properties Change of Cassava Starch Granule Induced by High Shear Mixer

“…The theoretical shear rate at the gap between the rotor and stator (̇t heo ) can be estimated by Equation (1), which consist of the function rotor diameter (D, (m)), rotor speed (N (s −1 )), and gap width (h (m)). [13,31] theo = DN h (1) This experiment used the normal mixing process (NM) and native starch (Native) as a control variable. For NM, the suspension was stirred with a magnetic stirrer (Cimarec, Thermo Fisher Scientific, Massachusetts, USA) at moderate speed.…”

“…The theoretical shear rate at the gap between the rotor and stator () can be estimated by Equation (1), which consist of the function rotor diameter ( D , (m)), rotor speed ( N (s −1 )), and gap width ( h (m)). [ 13,31 ] …”

“…[12] It is agreed that the shear rate is one of the key parameters for determining HSM performance in the structural degradation of starch. [13] A typical HSM accommodates shear rates from 10 000 to 150 000 s −1 . [14] By varying the rotor speed and the rotor-stator dimensions, it is possible to control the shear rate of a HSM and create a better starch granule degradation process.…”

Automated robotic platforms in design and development of formulations

“…However, also in this case, the challenge of reaching similarly high mechanical stresses typical of a shaking process is still an issue, also considering that most formulated products are processed on a long time scale not easily achievable in continuous flow micro‐devices. Some continuous flow high‐shear mixers have been proposed, 85‐87 also for formulated products.…”

“…However, also in this case, the challenge of reaching similarly high mechanical stresses typical of a shaking process is still an issue, also considering that most formulated products are processed on a long time scale not easily achievable in continuous flow micro-devices. Some continuous flow highshear mixers have been proposed,[85][86][87] also for formulated products.To the best of our knowledge, the only reported example in the literature of closed-loop robotic optimization for formulated products involves the use of an off-line non-automated incubator to efficiently process samples,88,89 once again demonstrating that this remains an open challenge in academia. Integration of all the main aspects of sample preparation, that is, liquid and solid dispensing, mixing, heating, and weighing, in the same platform has been achieved in some commercial systems, the most notable platforms being Chemspeed and Symyx,90 GEOFF automated formulation robot by LABMAN.…”