Avaliação de alterações na seção transversal do duto de alimentação de um hidrociclone

Abstract

Hydrocyclones are part of an important group of equipment used for separation of particles in centrifugal field. The flowfield prediction inside this equipment can be obtained by computational fluid dynamics (CFD) simulation. Some studies indicate that the operational and geometric parameters can directly influence the separation performance of a hydrocyclone. Therefore, an alternative to this improvement, according to the literature, is a possibility to change the cross section of the circular feed duct to rectangular. The objective of the present work was to evaluate, using CFD techniques, the modification of the cross section of the duct feed from circular to square (7x7 mm) and rectangular (8x6 mm and 9x5,3 mm) of an optimized hydrocyclone (HCOT1), keeping the same transversal area (around 47,78 mm²). In addition, it was simulated the coupling of another feed duct, both with rectangular transversal section (8x3 mm), this modification was performed considering a study available in the literature, which reports the possibility of improvement in particle separation efficiency by increasing the number of entrances and reducing their widths. All meshes were made with the aid of GAMBIT® software, using mesh elements of the hexahedral type. The three-dimensional single-phase flow simulations were conducted using the FLUENT® Academic numerical solver applying the RSM turbulence model, in transient regime, adopting a maximum residue of 1.10- 4 as convergence criteria, being considered stable from 2 s. Thereafter, experimental tests were performed on one of the proposed hydrocyclones, denominated STQ (7x7), using an aqueous suspension of quartzite in four different pressure drops. It is emphasized that the choice of this hydrocyclone was made based on the descriptions of the fluid dynamics profiles, in which it was possible to observe higher values of axial and tangential velocities for this equipment in comparison to HCOT1. Through the carried out of simulations, was possible to analyze the differences and similarit of the evaluated equipment, using the predictions of Euler number (Eu) and liquid-to-throughput ratio (RL). Despite the simulations indicate RL being similar for all hydrocyclones, it was superior for the new configurations, but the geometry called HCOT1 presented the lowest energy consumption (Eu = 2604). It should be noted that the hydrocyclone HCOT1 is an already optimized geometry, obtained by researchers of the School of Chemical Engineering of UFU, and any small improvement is important. In fact, in view of the experimental results, one of the geometries proposed in this study, called STQ (7x7), compared to HCOT1 presented, in general: RL values 3,19 percentual dots higher (in average); cut size diameter 32% smaller in average; and Euler number 12,49% higher in average, that is, a higher energy consumption. Therefore, depending on the purpose of the use of the STQ (7x7) equipment, if this increase in energy consumption is not significant, a smaller cut size diameter in the operation of this equipment can be an interesting alternative.