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Studies on hydrocyclones have evolved over recent years and various configurations of this device have been proposed in the literature for different purposes. Herein, an innovative geometrical configuration of hydrocyclones was developed by means of the response surface technique, combined with an optimization algorithm and supported by a computational fluid dynamics complementary study. The results obtained with these optimization techniques were validated by experimental data. The optimized hydrocyclone configuration is characterized by low energy consumption, i.e., low Euler number, with a small underflow‐to‐throughput ratio and can be used as a thickener hydrocyclone.

Hydrocyclones are separators used in several industry fields, such as mining, food and petrochemical. Our research group designed a new hydrocyclone, in which a conical filtering wall replaces the conical section, producing another liquid stream leaving the equipment, besides underflow and overflow streams. In the present work, the influence of inlet diameter (Di) of a filtering hydrocyclone was analyzed by an experimental and CFD study. Data from conventional hydrocyclones of the same configurations were also obtained. Under the same operating conditions and geometry, the filtering hydrocyclone presented a better performance than the conventional device. Under the experimental conditions evaluated, an increase in inlet diameter by a factor of 2.2 reduces the Euler number by 84%. Keywords: Hydrocyclones, solid-liquid separation, unit operations IntroductionHydrocyclones are very simple devices, that consist of a conical section, open at its apex (underflow), joined to a cylindrical section, which has a tangential feed inlet [1]. The top of the cylindrical section is closed with a plate with an axially mounted overflow pipe. Despite the apparent simplicity, hydrocyclones are very efficient to promote solid-liquid and liquid-liquid separations. These devices convert pressure generated by a centrifugal pump into centrifugal force, causing suspended solids in the mud to be separated from the fluid. This separation is actually accelerated settling due to the increased gravitational force cause by the centrifugal action inside the cone. The action inside the hydrocyclone can multiply gravitational force by as much as 200 times [2].Application of hydrocyclone for particles separation is widespread due to advantages such as low cost, simple structure, large capacity and low volume [3]. Despite its simplicity, the flow behavior in a hydrocyclone is quite complex. The internal flow in these devices is totally turbulent and presents high vorticity preservation, vortex breakdown, flow inversion, air core etc. However, advances in computational technology, over recent years, have led to models based on fundamental fluid flow to predict the performance of the equipment. Computational Fluid Dynamics (CFD) is an important www.cet-journal.com Page 2 Chemical Engineering & TechnologyThis article is protected by copyright. All rights reserved.technique to study the fluid dynamics of many physical systems and it has been used widely in several engineering applications [4,5], including modelling flow in hydrocyclones [6][7][8][9][10][11][12][13][14][15].The literature presents some classic designs of hydrocyclones (also called families), in which the main design variable is the cylindrical diameter (Dc), and the other geometric dimensions are related to this one. The use of a certain family of hydrocyclones is generally restricted to the demand for a specific application [16].For improving the performance of hydrocyclones, many modifications in the conventional configurations of this device have been proposed in the literatur...

The industry of açai-based products has been growing in the last few years. Knowledge about the physical properties of açai pulp, including its rheology, is essential to the optimization of industrial processes. This work presents the rheological behavior of açai berry pulp in relation to the effects of shear rate, temperature, and time of shearing. The entire study was carried out in the temperature range of 10-70 °C. Açai pulp showed a non-Newtonian, pseudoplastic, and time-dependent behavior. Four upward and backward shear rate cycles were evaluated, resulting in complex hysteresis loops, in which thixotropy and anti-thixotropy zones were observed. Downward flow curves could be satisfactorily represented by the Power-Law rheological model. The stress profiles as a function of shear rate obtained in the first upward curves suggest a breakdown of the initial fluid structure at low shear rates. Tests were also carried out at a constant shear rate of 20 s and, in this case, the Weltman model of thixotropy satisfactorily fit the experimental data. The activation energy, which was calculated by the Arrhenius equation, was 29.0 kJ/mol. The achievements of this work may be useful to further studies about açai pulp rheology and may contribute to process design in the açai industry.