Processing of high solids content pastes with evolving rheology

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Within the Unilever Beauty and Personal Care (BPC) portfolio, products with a wide range of rheological properties can be found which can be defined by their specific microstructure which includes isotropic solutions, lamellar structured liquids and high solids content pastes. Much research is actively being conducted to gain better understanding in the area of processing of isotropic fluids, yet comparatively limited research is dedicated to the field of high solids content pastes. The proposed research project aims to gain better understanding of the processing challenges for this system.The manufacture of BPC products is achieved through the sequential addition of raw materials in a defined order, specified rates of addition and controlled temperature profiles. Thus, there are two attributes which vary throughout the manufacturing process of BPC products: (1) increasing fluid level within the batch vessel and (2) variations in rheological properties for each of the intermediate stages, affected by the composition, temperature and processing conditions. These two attributes will impact the achievable mixing inten sity and efficiency, as well as flow characteristics within the vessel and any associated pipework. This, in turn, affects product quality, energy requirements and overall process optimisation. Furthermore, many processes for the manufacture of BPC products involve utilisation of recirculation loops to achieve both top-to-bottom homogeneity within the main vessel and/or efficient incorporation of raw materials within the product (powder additions under vacuum).The proposed research project aims to explore these three effects (increasing fluid level, variations in rheological properties and microstructure evolution ) for high solids content pastes, achieved through use of dynamic torque measurements, the development of power draw expressions as a function of fluid level in-vessel and flow characterisation techniques, such as positron emission particle tracking (PEPT) and particle image velocimetry (PIV). In addition, the project will explore the computational fluid dynamics (CFD) space to identify an approach that would allow tracking the evolution of the vessel level and product rheology throughout the process, using experimental results for validation .