Papers by Author: Marcos A.S. Barrozo

Abstract: In industrial applications, it is very common to use multiple hydrocyclones in parallel to improve the separation. This equipment employs the centrifugal field to promote solid-liquid or liquid-liquid separation. In cases where there is interest in recovering the liquid phase by removing the maximum amount of dispersed phase (waste), such as in oil well drilling units and in water treatment systems, the employment of a hydrocyclone able to promote both the recovering liquid and the concentration of suspension is viable. This paper presents a comparison between two hydrocyclones considered concentrators, called H13 and HCOT3. The results obtained showed that both separators have a satisfactory capacity to concentrate aqueous suspensions, with the underflow-to-throughput ratio equivalent. The Euler number of HCOT3 hydrocyclone was 19% lower than that obtained for the H13 hydrocyclone. Moreover, the results showed that the HCOT3 has a total efficiency of separation 34% greater compared to H13.

Abstract: Hydrocyclones are equipment typically used in solid-liquid separation. Such equipment can be used with the purpose of classifying particles or concentrating suspensions. In this context, a new filtering hydrocyclone was conceived through Surface Response and Differential Evolution Algorithm techniques in order to optimize the Euler’s number. Based on this optimized geometry, the aim of the present paper was to verify the influence of the underflow diameter on the overall separation process at 147 kPa on the same optimized hydrocyclone geometry, but without the filtration effect, by performing laboratory experiments and CFD simulations using the commercial software Fluent®. The results showed that the use of the smallest underflow diameter increased up to 44% (v/v) the concentration of the underflow stream, compared to the suspension initially fed, with an Euler’s number of 862. Despite a small decrease (14%) in the total efficiency and an increase from 12.01 to 16.05 of the reduced cut size diameter, compared to the underflow diameter originally used in the optimization procedure, the benefits of recovering liquid by reducing the underflow diameter outweigh these disadvantages.

Abstract: Tumbling ball mills are a common comminution device in the mineral industry processing, wherein the particle size reduction is performed by action of the grinding media. Different forms of transverse motion in a rotating cylinder have been studied by many researchers. The aim of this paper was to study the transitional phenomena between cascading, cataracting and centrifuging motion. In order to observe these transitions, experiments were carried out in a tumbling mill of 300 mm diameter, and three sizes of chrome steel balls were used as grinding media. Each size of ball was employed in three different lengths of the mill with the purpose to investigate the end-walls effect in the behavior ball charge. The image analysis technique was employed to identify the transition regions. A high-speed camera with maximum speed of 2000 frames/s was used to record images. Experimental data showed it was not found the end-wall effects on the transitional behavior, and this effect can be assessed in numerical studies by analyze of the specularity coefficient.

Abstract: In this work, it was done a series of analysis in different conditions of the pyrolysis process to verify the difference of the composition in each one of the final products. In the case of the slow pyrolysis the heating ratio varied among 1.5, 20, 40 e 50 °C/min, and analyzed for each of these rates the composition of the final product. For the case of the fast pyrolysis, the temperature varied among 350, 400, 450, 500, 550 °C, maintaining the other conditions of the process constant, in the end of the process analyzed the composition of the final product for each temperature. For the verification of the composition of these products, they were classified and separate in categories according to the functional group, and after that, the ones who had the most relevant quantities were more deeply analyses to verify some important characteristics and the main industry applications. After this, it was determined the ideals conditions of slow and fast pyrolysis. The resulting products were analyzed by gas chromatography/mass spectrometry. For slow pyrolysis, the heating rate of 40°C/min produced a diversified product, composed by the heterocyclics, levoglucosan, phenols and hydrocarbons. The fast pyrolysis produced mainly the heterocyclic compounds, levoglucosan, phenols and carboxylic acids, in temperatures between 450°C and 500°C.

Abstract: Spouted bed simulations are usually performed using only one granular phase with a mean particle diameter representing the entire particle mixture, instead of a particle size distribution. In this study, the effect of the particle size distribution is accounted through the simulation of a mixture with five granular phases. The results showed that the particle segregation occurs. Larger particles are more concentrated in the upper region, while the smaller particles are preferably positioned in the lower region of the bed. Computational simulation using CFD method reproduced well the segregation experiments with different participle sizes of sand.

Abstract: Flotation is a complex process in which is present physicochemical and hydrodynamic phenomena. The flotation performance is related to the probability of bubble-particle collisions and stability of aggregate formed. The collision efficiency is a function of particle and bubble diameters. Currently one of the biggest challenges of the mining industry is the flotation of fine and ultrafine particles and a possible solution to increase the recovery of these fine particles is the use of bubbles with intermediate size (100-1000μm). Therefore, determining and controlling the bubble size is very important for further recoveries in the flotation of fine particles. It is known that the bubble size and air holdup are influenced by variations on the superficial gas velocity and by addition of surfactants. Thus this work aimed to study the effect of adding surfactants on bubbles formation. The results showed that the addition of surfactant was a good alternative to decrease bubble size and increase the air holdup in a bubble column. Three different surfactants had similar behavior on bubble size and holdup. It was possible to define the range of concentration values which are sufficient for forming bubbles with intermediate size and holdup within the range recommended for mineral flotation.

Abstract: Rotary dryers are widely used in various industries. Although numerous research efforts have focused on characterizing the dynamics of these equipments, the design of rotating dryers is complex, and theoretical studies are necessary to gain an in-depth understanding of the dynamics of particles in these dryers. This paper aims to investigate the particle dynamic behavior in a rotating drum with flights, based on CFD and experimental results. In the numerical study it was used the Eulerian-Eulerian multiphase model along with the kinetic theory of granular flow. The holdups of solids in the flights were compared with experimental data, using a methodology created specifically for this purpose. The simulated results were in good agreement with the experimental data and the present work has shown that the Eulerian approach has been able to predict the fluid dynamics behavior in different operating conditions.

Abstract: Hydrocyclones are equipments widely used in solid-liquid separation, as in mineral, chemical, petrochemical, textile, and metallurgical industries. The suitable choice of its dimensions depends on the process main objective. There is the case that the major interest is to concentrate a suspension, either to discard the dispersed phase (solids) or to use it. The objective of this work was to study, experimentally, a filtering hydrocyclone with a suitable geometry that provides a low underflow-to-throughput ratio, i.e., that produces a thick underflow. The effect of the underflow orifice diameter in the equipment performance was evaluated. The results showed that the smallest orifice size produced an underflow stream with concentration upper than 45% in volume.

Abstract: The use of recycled water in the apatite flotation may result in losses to the process performance due to the presence of ions, residual reagents, finely particulate material, etc. The dissolved air flotation (DAF) has been shown an efficient technique in the wastewater treatment in the removal of these pollutants. The use of anionic collector in DAF process is based on the reaction that occurs between the soybean oil soap (apatite collector) with the calcium present in the apatite lattice making its surface hydrophobic. Therefore, the collector can be an auxiliary in the water softening besides improving the hydrophobicity of the particles to be collected. Thus, this study was aimed at evaluating the effect of an anionic collector used as an auxiliary in the dissolved air flotation process. A central composite design (CCD) was proposed to evaluate the concentration of collector and the effect of pH value on the removal efficiency of calcium, magnesium, fluoride, phosphorous and turbidity present in a wastewater from a fertilizer industry. The results showed a good removal of the contaminants which guaranteed a better quality of water to the process of phosphate rock concentration.

Abstract: This paper aims to investigate the particle dynamic behavior in a rotating drum operating in a rolling regime under different rotating velocity, based on experimental results and simulations. Simple superphosphate fertilizer (SSP) was used as particulate matter in the current study. The Eulerian–Eulerian multiphase model along with the kinetic theory of granular flow was used in the simulations. In order to evaluate the simulation results, velocity distributions of the particulate phase were compared with experimental data. The experimental particle velocity distribution was obtained by using a high speed video camera. The numerical simulation results showed significant insights towards understanding of the particle dynamic in a rotating drum. The simulated results of particle velocity were in good agreement with the experimental data.