Claudio Roberto Duarte

Effect of a Draft Tube on the Fluid Dynamics of a Spouted Bed: Experimental and CFD Studies

Knowledge about the gas and particle dynamics in spouted beds is important in the evaluation of particle circulation rates and the efficiency of gas-solid contacts. In this work, the mechanism of transition from a static bed to a spouted bed was numerically simulated using a Eulerian multiphase model. This model was applied to two distinct spouted bed geometries: a conventional device and a spouted bed with draft tube. The radial voidage and particle velocity profiles along the longitudinal position in the annular and spout regions were simulated for the geometries under study. The characteristic simulated curves were congruous with the experimental data.

A study of the fluid dynamics of the spouted bed using CFD

The spouted bed has been used in drying, granulation, catalytic polymerization, residue treatment and coating of several materials. Its success is attributed to its solids circulation characteristics and excellent gas-particle contact. In this work the pattern of solids and gas flows in a spouted bed was numerically simulated using a Eulerian multiphase model. The computational work was significantly reduced for axisymmetric gas-solids flows. The simulated velocity and voidage profiles were compared with results obtained in our laboratory (with a two-dimensional spouted bed using soybean seed) and by He et al. (1994) (with a cylindrical spouted bed and glass sphere). The simulated results showed good agreement with the experimental data for both geometries studied.

Modeling of Seed Coating in a Spouted Bed

In this work, a model based on population balance equations applied to perfect mixture domains has been employed to represent the coating of soybeans with fertilizer in a conical–cylindrical spouted bed. The results of the present model provided explicit equations for the coating mean and variance. The coating mass distribution function was validated against experimental data. The effect of operational time on the distributions was analyzed, showing that the coating uniformity can be improved by increasing the operating time.

Experimental study and simulation of mass distribution of the covering layer of soybean seeds coated in a spouted bed

In previous work, it was observed that the covering of soybean seeds with bacteria and micronutrients enhances vigorous growth of the plant thereby avoiding use of ammoniacal fertilizers. In the spouted bed covering can be done by pulverization of the coater slurry on the soybean seeds using a pneumatic atomizer. The optimum thickness of the cover allows the fundamental gaseous interchanges for germination and provides the ideal conditions for bacterium activity. The objective of this work was to study the influence of the process variables on thickness of the cover. A simulation of the mass distribution of seeds was obtained using a population balance model. Through the results obtained the operational conditions under which the coating layer distribution were determined has the greatest uniformity.

Spouting of Bidisperse Mixture of Particles: A CFD and Experimental Study

Many spouted bed applications involve mixtures of particles of different sizes, shapes, or densities. Depending on the characteristics of the particle mixture, undesirable phenomena such as particle segregation may occur, mainly due to differences in terminal velocities. Thus, a better understanding of the fluid dynamics of particle mixtures is still needed in this field. In this work, experiments and computational simulations were performed to analyze some aspects of the fluid dynamics of segregation patterns in conical spouted beds with binary mixtures. The simulated results are consistent with experimental data and can be used to predict regions of particle mixing or segregation in spouted beds.

Experimental and numerical study of spouted bed fluif dynamics

Spouted beds, originally invented in Canada by Mathur and Gishler (1955) as an alternative to fluidized beds for handling coarse particles, are now widely studied in a variety of physical operations, such as drying, coating and granulation. In this work the particle velocity, minimum spouting flow rate and characteristic fluid-dynamic curves of the spouted bed were obtained using a Eulerian granular multiphase model. The computational work was significantly reduced for axisymmetric gas-solid flows. The experimental data obtained in two spouted bed configurations, conical-cylindrical and two-dimensional, were compared with the simulated results, showing good agreement

Mixture of Particles' Influence in Computer Simulations of a Spouted Bed

This article aims to assess the influence of the way of simulating monoparticles as just monoparticles or as a mixture of particles, the latter, unlike the first, considering the effect of particle-particle interaction. The Eulerian–Eulerian multiphase model is used in the computational simulation of fluid dynamics of spouted beds and compared with experimental data. A half column of cylindrical spouted bed with a full plane glass attached to the front open surface of the bed as the transparent window was used for observation and photographing. Images of solid flows were recorded using a high speed camera (2000 frames per second). Glass beads with a diameter of 0.00368, 0.005 and 0.00252 mm are used as bed material. The simulated characteristic fluid dynamic curves of spouted bed for 0.15 m static bed heights (Ho) were obtained with good agreement with experimental data when the monoparticles was simulated as a mixture of particles with mixture’s percentage of 50%. The same occurred for the simulation of vertical velocities of particles profile, that is, when the monoparticles was simulated as a mixture of particles with mixture’s percentage of 50% we observed a more approach to the experimental data. It was also observed that the air concentration distribution seem to be independent of the changing of the composition.

Effects of dehydration methods on quality characteristics of yellow passion fruit co‐products

BACKGROUND The production and processing of fruits generate a large amount of residues, which are usually disposed of or under-used, representing losses of raw material and energy. The present paper investigates the effect of four dehydration techniques (convective, infrared, microwave and freeze-drying) on yellow passion fruit (Passiflora edulis f. flavicarpa) co-products and the influence of the main variables on moisture removal and bioactive compounds. The compounds analyzed were total phenolics, total flavonoids, ascorbic acid and pectin. RESULTS The content of phenolics and flavonoids increased after dehydration in all techniques investigated and the process temperatures directly affected the ascorbic acid content. Microwave dehydration showed the best results for most bioactive compounds analyzed, if performed in suitable process conditions. However, the highest levels of pectin content were obtained by freeze-drying and convective dehydration. CONCLUSION This study reinforces the importance of the adequate use of passion fruit co-products due to the high levels of bioactive compounds in this material. Microwave dehydration presented the best results, which indicates the potential use of this technique for a better exploitation of fruit co-products. Larger quantities of pectin were extracted from samples dehydrated through methodologies with long-time process and low temperatures, such as convective drying and freeze-drying.

Coating of Particles in Spouted Bed: Flow Regime and Stability

The coating and encapsulating of particles presents many applications in the chemical, pharmaceutical, food and agricultural products industries. Among the many applications of seeds coating, the enlargement of small seeds is included in order to facilitate the planting, the addition of herbicides, fungicides, fertilizers, micronutrients and inoculation. The spouted bed has often been used in studies related to the coating of particles, due to the cyclical motion of the material, which promotes a fast axial mixture of particles and an excellent gas-particle contact. In this work, the coating of soybean seeds with inoculum and micronutrients in spouted bed has been studied. The different flow regimes were investigated using the pressure fluctuations and power spectrum. The results of the present work showed that it was possible to identify the main flow regimes and to analyze the influence of the coating in the stability of those regimes.

Analysis of the design loading in a flighted rotating drum using high rotational speeds

ABSTRACT Although rotating dryers with flights have been extensively used in industrial applications, there is still a lack of universality in the literature models to estimate their design loading. The aim of the present paper was to study the design loading of a flighted rotating drum and its dependency on rotational speed. The use of high rotational speeds is a novelty of this paper, to operate at peripheral speeds like the ones in industrial equipment. The effect of the rotational speed on the last unloading flight was also studied. The results showed the limitations of the geometric models to predict the design loading. A new model was proposed to predict the Froude number for design-loaded equipment as a function of the drum filling degree. The results predicted were very close to the experimental data.