Scale-up in Turbula® mixers based on the principle of similarities

Abstract

Many processes from a wide range of industries use powders as raw materials. In most of them, mixing of dry particles is a critical step. However, the complexity of granular materials leads to difficulties in predicting behavior of powders inside a blender. Cost and amount of raw materials needed to achieve these studies imply that such work is often performed at the laboratory scale. The main challenge then lies in the extrapolation of results from lab to pilot or industrial scale with minimum testing in order to optimize costs. Defining reliable scale-up laws for powder mixers remains one of the main industrial issues. The work presented here concerns the scalingup of TurbulaV R mixers that are commonly used both in industry and research. Mixtures obtained in different mixer sizes have been compared on the basis of kinematic and dynamic similarities and discussed according to the different flow regimes involved. The dynamic similarities appear to lead to mixture qualities at different scales closer to each other than those obtained on the basis of kinematic similarities probably because of similar flow regimes. However, some other parameters must be taken into consideration, such as the free surface of powder related to the filling ratio.

Investigating grinding mechanisms and scaling criteria in a ball mill by dimensional analysis

“…However, one can wonder if these principles could also be applied for extrapolations to larger scales. In a similar investigation, Mayer-Laigle [31,32] used the principle of similarities to establish scale-up laws for a powder mixing operation carried out in Turbula Ò mixers. The scaling criteria obtained allowed to get similar mixtures with vessels from 2 L to 17 L. However, signif-icant differences were observed when applying these criteria to an industrial vessel of 50 L, suggesting that other mechanisms must be considered when extrapolating at larger scales.…”

CFD Analysis of Mixing Process of Detergents in Rotational and Displacement Vessels

“…The mixing process consists of turning the canister 90 • around an axis a few centimeters below its bottom at 45 rpm. This movement is a simplification of that of the Turbula © mixer (Willy A. Bachofen AG, Muttenz, Switzerland), which is a powder mixer [1,2]. Nevertheless, the detergent mixing device must be capable of mixing both powder and liquid detergents, for the sake of development requirements of the DIY4U project.…”