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The performance of flighted rotary drums strongly depends on the distribution of the particles across the drum transverse and longitudinal sections. This work aims to determine the design and arrangement of flights that optimize the distribution of the particles in the active region. The prediction of the solids flow was investigated by DEM simulations. A multi-response optimization was performed, in which the obtained best configuration of three-segments flight presented the following internal angles: α1 = 95°, α2 = 130°, and α3 = 145°. The effect of the intercalated position of the flights on particles distribution in the active region was also evaluated. The configuration with the separation distance between flights of 15° promoted an increase of 24.6% in the area occupied by the particles in the active region, and a reduction of 38.5% in dispersion heterogeneity of solids when compared to that of the arrangement of aligned flights.

This paper aims to systematically investigate the cataracting-centrifuging transition in a rotary drum involving spherical and nonspherical particles by using the Multiphase Granular Eulerian Model (MGEM). The effects of drum length and particle shape on the cataracting-centrifuging transition behavior were analyzed. The results showed that drum length plays an important role in the cataracting-centrifuging transition, although most related works in the literature do not consider this. The particle shape also significantly affects the cataracting-centrifuging transition behavior. Nonspherical particles required lower rotation speeds than spherical particles to reach the centrifuging condition. The particle shape was shown to be related to the critical solid fraction (αsc) from Schaeffer’s model, although further investigations are required to completely correlate particle spherecity with critical solid volume fractions.

Biomass is a renewable energy source of increasing industrial interest. However, due to particle physical characteristics, operational problems are verified during its transport, which is usually associated with the control of the feeding process. In this context, a feeding system was designed, specifically for the control of biomass flow rate, in a positive pressure pneumatic conveying line, which made it possible to evaluate the feeding efficiency of a rotary valve, using materials with different physical properties and varying air velocity, valve rotational speed and the height of material in the feeding silo. The biomasses evaluated were milled corn, corn cob, corn straw, rice husk, and wheat bran, which were characterized by their density, size, angle of repose, shape, and moisture content. The study presented relevant results, such as biomasses of low bulk density obtained greater feeding efficiencies for the conditions of lower material height in the silo due to easier breaking of the mechanical/cohesive arches formed, while the material of higher density showed greater efficiencies in conditions of greater heights. Besides this, an empirical correlation was proposed to predict the pressure drop in the feeding tee, whose coefficient of determination was 99.11%, with a maximum deviation of 10% in relation to the experimental data. The differential of this correlation is the insertion of a shape factor in its equation, given the irregularity of the biomass particles.

The proper choice of the dryer configuration for seeds drying is essential to preserve their quality during this process. Drying of soybean seeds was studied in this work using a non-conventional c...

Predicting the flow behavior of particles is important for the equipment design and optimization of processes and operations involving granular materials. Simulations using the discrete element method (DEM) have been used to gain insights about the granular flow, but the correct use of this technique requires knowledge about the input parameters. However, reliable measurements of these parameters remain a challenge. The purpose of this study was to test and validate experimental methodologies for determining important DEM parameters, including the coefficients of restitution and static and rolling friction, for the particle–particle and particle–wall interactions. The experimental tests were reproduced using DEM simulation to enable the identification of the best procedure for measuring each parameter. The influence of the thickness of the material on which the particles are colliding on the experimental measurement of the coefficient of restitution were quantified. It was also performed a deep statistical analysis of the simulations results using experimental design techniques to identify the significant input parameter in each measurement technique, using loose and grouped particles.

Camu-Camu (Myrciaria dubia) is a native fruit from the Amazon region, which is still little known by most people, but that has been arousing great interest from the scientific community due to its ...

The particle dynamics in a flighted rotary drum operated with different numbers of flights and under different operating conditions was simulated by using both the Eulerian (computational fluid dynamics, CFD) and the Lagrangian (discrete element method, DEM) approaches. The simulated solid holdups in the flights as a function of the flights’ tip angular position were compared with experimental data. A systematic analysis of the computational demands of each approach was performed, as well as the impact of reducing the particle shear modulus in DEM simulations. Furthermore, the influence of the turbulence phenomenon on the particle behavior predicted by CFD simulations was also assessed. The choice of an appropriate numerical approach proved to be of great importance in the accuracy of particle dynamics prediction in a flighted rotary drum.

A low-cost and non-intrusive methodology using a solidification-slicing approach was proposed in this work for the investigation of radial and axial segregation phenomenon in a spouted bed. The effects of diameter, density, and shape of the particles, as well as the initial particle loading, and the inlet air velocity on segregation, were qualitatively and quantitatively assessed. Suitable radial and axial segregation indexes were used to quantify the segregation degree. The proposed approach contributed to understanding the particle mixture dynamic on the entire bed material.

The industrial processing of acerola (Malpighia emarginata D.C.) produces huge quantities of waste material that are badly discarded or undervalued. In spite of this, acerola wastes have a high content of antioxidant compounds. The aim of this work was to study the extraction of antioxidant compounds from acerola residues using ultrasound assisted extraction. Using multiple regression techniques, the effects of ethanol concentration in the hydroethanolic solution (C), extraction time (t), temperature (T), and liquid–solid ratio (R) on the total phenolic content, total flavonoid content and antioxidant potential were investigated. The best extraction conditions were identified using the desirability function, which is a multi-response optimization technique. The optimal processing parameters were 67.5% of ethanol concentration, temperature of 80.9 °C, liquid/solid ratio of 59.8 mL/g, and extraction time of 13.6 min. HPLC–UV has been used to identify the main antioxidant compounds obtained under these optimal condition. Based on the results, acerola waste has high potential for better use, such as in food and pharmaceutical applications.

In the rotary dryers with flights, the drying occurs mainly in the active region where the material comes into direct contact with the air stream. The design of these flights is a complex task and studies are necessary to gain an in-depth understanding of the particle dynamics. This work aims to investigate the effects caused by angulations in flights of two and three segments on the particle dynamics, especially in the active region. The prediction of the solids flow was investigated by simulation using a Discrete Element Method (DEM) approach in an open-source software LIGGGHTS®. The simulated results were compared with experimental data using glass beads, with the rotary drum operating with 12 flights. The active region characteristics were analyzed using the responses variables: mass of solids in active phase, percentage of active region area occupied by the particles and the dispersion of the particles in the active region.

In this work, we experimentally and numerically investigated the mixing/segregation behavior of particles in an unbaffled rotary drum. We analyzed different combinations of binary mixtures that varied in density and size. We also quantified the effect of filling degree and rotational speed of the drum on the mixing index of each binary mixture. We used the discrete element method (DEM) for the simulation study, in which we determined the input parameters by both experimental measurements and calibration. The results reveal that the simulations using experimentally measured DEM input parameters had the best agreement with the experimental responses (repose angle and radial mixture). The experimental and simulation results enabled us to analyze the significant effects of filling degree and rotational speed on the granular radial and axial segregation of different binary mixtures.

Hydrothermal carbonization (HTC) is a promising technique for the improved management and better use of agro-industrial wastes. In this study, the effects of temperature, reaction time, biomass/water ratio, feed-water pH, and agitation speed on the HTC of acerola wastes were investigated. The effects of these independent variables on process yield and on the total oxygenated functional groups of hydrochars were quantified. The best process conditions were obtained using the desirability function and the chemical-morphological properties of the hydrochar produced in these optimal conditions were investigated. The total number of oxygenated functional groups were found to be higher than those described in the literature for similar biomasses. The effects of temperature, solution pH, initial dye concentration, and adsorbent dosage on the adsorption of methylene blue using the obtained hydrochar were also investigated and the conditions necessary for the maximum removal and adsorption capacity were determined. Adsorption isotherms and thermodynamic studies have shown that methylene blue adsorption on the obtained hydrochar is endothermic and spontaneous. Thus, the HTC of acerola wastes may be a sustainable technology for the modification of underutilized wastes and their application as adsorbents of environmental contaminants.

The main objective of the present work was to investigate the microwave drying kinetics of drill cuttings contaminated with an olefin-based fluid in a bench-scale microwave oven. Drying tests were ...

Among the various species of microalgae, Spirulina platensis has recently attracted attention from food and pharmaceutical industries due to its high contents of protein and bioactive compounds. Due to its high moisture content, a major challenge in the use of this microalga is its perishability. In this work, we investigated the use of a non-conventional rotary dryer (with an inert bed) for drying microalga Spirulina platensis. We quantified the effects of air temperature, feed rate, rotation speed, and filling degree of the inert particles on process performance. We then performed an optimization study using the Differential Evolution algorithm to identify the operating conditions that maximize process yield. We also performed a DEM simulation to gain a better understanding of the fluid dynamics. The results prove that this non-conventional system offers an interesting alternative for expanding use of this biomass, when performed under appropriate operating conditions.

In the operation of drilling oil and gas wells, fragments of reservoir rocks generated by the action of the roundabout drill, generically denominated by drill cutting, are loaded to the surface by the drilling fluid. Most of the drilling fluids used in Brazil are not aqueous because they have an organic base and have been classified as synthetic base fluids. The drill cuttings contaminated by this organic compound must be separated from the drilling fluid for later disposal in the environment. Drying technology through microwaves has shown promise by reaching contaminant levels of below 1%. However, there is currently no device on an industrial scale which is both efficient and reliable in the treatment of drill cuttings with low energy consumption that is capable of reaching residual contaminant contents (

Acerola (Malpighia emarginata D.C.) industry generates a large quantity of residues, which are underused or incorrectly disposed. However, acerola residues are rich sources of bioactive compounds. Nevertheless, this fruit waste presents high values of angles of repose, as well as low density and high moisture content. These factors result in poor flowability making it difficult to use moving beds in its processing. This paper investigates the performance of a new system composed of a packed bed dryer assisted by infrared radiation (IR) for acerola residues drying, considering its reuse. We investigate the effect of main process variables on moisture removal and on the antioxidant properties of this coproduct. We propose prediction equations to evaluate the dehydration rate as a function of the independent variables for different axial bed positions. We also quantify the ascorbic acid, total phenolic, and flavonoids compounds contents. The main phenolic acids and flavonoids compounds were identified using High Performance Liquid Chromatography (HPLC). The results of this study show that the new technique used in this work proved to be a good alternative for processing this residue, reducing the heterogeneity of the product and keeping the bioactive compounds at high levels.

The material being fed to the pneumatic conveying systems with rotary valve presents some operational problems due to the pressure gradient between the pipeline and the storage silo of the material. A usual alternative to minimize this kind of problem is to operate the pneumatic conveying system with closed silo, mainly when it is desired to feed low density material such as biomass. A great part of literature reports that the rotary valve speed is the most relevant variable in the evaluation of filling efficiency of the feeding device. However, after evaluating the proposed feeding system, it is observed that the air velocity in the pipeline also considerably affects the materials' feeding rate, notably if the material to be conveyed has lower density. Considering the aspects highlighted previously, a 3k factorial design was performed to evaluate the influence of average air velocity and the rotation speed of valve in the feeding efficiency of two classes of polydisperse particles (powders and grains). The experimental results have allowed for obtaining a non-linear empirical correlation for each class of particle, capable of predicting the efficiency of the pneumatic conveying system's feeding rate. The correlations found in this study have presented coefficient of determination around 88.7% and 90.2% for powders and grains, respectively.

A systematic study upon the Eulerian approach capability in predicting irregular particle (non-spherical) dynamics inside an unbaffled rotary drum was carried out through the investigation of different particle-particle interaction models and wall boundary conditions. The drum length effect on particle dynamics was also analyzed. The frictional viscosity, the wall movement method, and the particle boundary condition at the wall were shown to be of fundamental importance for irregular particles modelling in rotary drums. The moving mesh method did not represent well the experimental observation, regardless of the solid boundary condition used at the drum wall. The moving wall method combined with a no-slip boundary condition for the solid phase at the drum wall, and the frictional viscosity model using a critical particle concentration (αsc) of 0.4, satisfactory agreed with experiments. For the end-caps analyses, the higher the ratio L/ds, the lower the bed material surface slope and the lower the particle velocity values in the active region. From L/ds of 40.7 no differences were observed in particle dynamics behavior anymore.

Fruit processing generates a large amount of waste that is generally discarded or underused. However the wastes of some fruits, such as acerola, contain bioactive substances with health promoting properties and potential technological applications. This paper evaluates the performance of a hybrid system composed of a microwave assisted rotary drum for the dehydration of acerola wastes and considers the efficiency of this new system and the product quality (bioactive compounds content). The mixture and segregation processes in the rotary drum induced by differences in moisture content, rotation speed, and filling degree were also evaluated. Good operating conditions for mixture were identified and they were related to the regimes of solids motion in the rotating drum. This study also analyzed the effects of power density and rotation speed on dehydration performance. Conditions with high moisture removal that lead to a product with high bioactive compounds content were also identified.

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...

Brazil is the largest producer and exporter of coffee in the world, one of the main global commodities. During the processing of coffee beans, rotary drums are used in the drying and roasting phases. This equipment is widely used in many industrial sectors. According to characteristics of the drum, particulate material, and operating conditions, different flow regimes may arise. Such regimes have a direct influence on the performance of these processes and therefore their characterization is of great importance. The present work developed an experimental study about the dynamics of coffee beans, under green and roasted conditions, in a rotary drum. Transitions between rolling, cascading, cataracting, and centrifuging regimes were evaluated, for both green and roasted coffee beans. For the centrifuging regime, a comparison between experimental critical rotation speeds and the ones obtained by correlations found in literature was performed. Additionally, a new expression to predict the centrifuging rotation speed was proposed by the authors. Further analyses regarding the rolling regime were also carried out. For this regime, velocity profiles of the particles were evaluated, as well as the thickness of the active layer for different filling degrees and drum rotation speeds. Great similarity was found between the behaviour of the active region for coffee beans before and after the roasting process.

This paper involves an experimental and numerical study on the grinding media dynamics inside a baffled ball mill under different solid flow regimes: cascading, cataracting and centrifuging. The Eulerian approach was used for all simulations and the boundary condition at the drum wall was investigated by means of the specularity coefficient parameter. This effort presents a meaningful temptation in representing the particle-wall interaction in a ball mill. The balls restitution coefficient was experimentally measured using a video camera, and its influence was evaluated by comparing the numerical and experimental outcome of flow patterns. The simulations results showed that the specularity and restitution coefficients effects at the drum wall were more evident at high rotation speeds.

Dynamic of particles in annular fluid flow is a very relevant subject for many industrial applications, especially for the oil and gas industry. Successful drilling is, to a large extent, dependent upon the ability of the drilling fluid to clean the hole by conveying the cuttings to the surface. The aim of this work was to evaluate experimentally and through numerical simulations, the helical path and the axial mean velocity developed by glass beads with diameter of 2.7 mm flowing with a non-Newtonian fluid through a partially obstructed annulus. Experimental data are reported for flow of 1 m3/h of an aqueous solution with 0.5% Xanthan gum through concentric annulus with partial obstruction of 6 mm and a 183 rpm rotation of the inner cylinder. Techniques of computational fluid dynamics (CFD) were applied to obtain detailed information about the flow field, allowing to estimate the radial position of launching of particles in the range of 35.5 mm to 39.1 mm. Comparisons between numerical calculations and the flow data indicated, in general, a very good agreement.

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.

Drill cuttings generated by oil and gas drilling process are incorporated into the drilling fluid to ensure an efficient drilling and solids removal. The drilling rigs have a separation system accountable for separating drill cuttings and drilling fluids. Microwave drying is a new technology of separation that has been studied as an alternative to the currently drill cuttings dryer used. The results obtained in preliminary studies showed that this microwave drying is sensitive to different oxides presents into the rock. Thus, this study aimed to describe the microwave heating kinetics of some rocks in order to verify the interaction of oxides with electromagnetic waves. For this, the oxide contents of the rocks were determined by X-ray Fluorescence and different rocks were heated in a microwave heating unit. The results showed that the relationship between the temperature and heating time is exponential and depends on the rock oxide contents. It was found that the iron oxides may be unstable at microwave and rocks with high levels of magnesium oxides and sulfates tend to be good absorbers of microwave. Rocks containing high levels of calcium, silicon, titanium, barium and chloride (NaCl) are not good absorbers of microwave. It was also noted that faster solid heating, lesser the efficiency of microwave drying.

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.

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. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

This study presents an experimental and numerical investigation of the particle dynamic flow in a rotary drum with one flight, under different boundary conditions. The Euler-Euler approach with the kinetic theory of granular flow was used for all CFD simulations. The influence of different specularity coefficient values and no-slip boundary condition was assessed varying the particle-particle restitution coefficient and the rotational speeds. The particle-particle restitution coefficient of glass beads was experimentally measured and the effect of this parameter on the particle dynamics was also investigated. A high-speed video camera was used to measure the flight unloading profile and the bed height of particles in rolling regime at the drum bottom. Quantitative and qualitative analysis were performed in order to compare the simulated results with the experimental data, and then to determine the appropriate parameters to represent the real particle flow. It was observed that the specularity coefficient value of 0.5 and the restitution coefficient of 0.9 represented well the particle flow behavior in the flight at the rolling regime for the different rotational speeds analyzed.

The high content of bioactive compounds in the microalga Spirulina platensis has recently attracted attention from food and pharmaceutical industries. However, for its application an effective preservation technique must be developed. In this paper, we investigated the use of a non-conventional rotary dryer (with an inert bed) for drying the microalga Spirulina biomass and the effects of the operational conditions (air temperature, intermittent feeding interval, filling degree of inert particles, and rotation speed) on its bioactive compounds. The results indicated that this non-conventional drying system offers an effective alternative for expanding the use of this biomass in an adequate form. We identified the conditions in which the dried material had maintained satisfactory contents of phenolics (air temperature of 70 °C and intermittent feeding interval of 10 min), flavonoids (intermittent feeding interval of 17.4 min), and phycocyanin compounds (air temperature of 40 °C), which were near to those present in fresh microalga.