Reversal of gulf stream circulation in a vertically vibrated triangular fluidized bed

Vibrated fluidized beds are a process intensification technique consisting in introducing vibratory kinetic energy in a fluidized bed (1). In this work we assess experimentally the effect of vibration on the gulf-stream circulation pattern of particles in a fluidized bed that is of triangular shape. The bed has 0.206 m span and 0.01 m thickness. The base of the bed is composed of two inclined walls, each one forming an angle of 45º with the horizontal. Air was injected through the inclined bed walls to fluidize the bed (see Figure 1a). This gas injection, together with vibration, can make the dynamics of this bed different to that found in a spouted fluidized bed (2). The bed is filled with ballotini particles with a mean diameter of 1.15 mm up to the top of the inclined walls. The bed vessel is made of antistatic PMMA to allow optical access with a high-speed camera. The bed was mounted on an electrodynamic shaker which produces the vibration. A high speed camera is used to record the motion of particles. The particle velocity was obtained via Particle Image Velocimetry (PIV). As a function of vibration amplitude and frequency, we observe several circulation patterns when the fluidization velocity is just below and above the minimum fluidization velocity. Noticeably, for zero gas velocity, particles ascend close to the side walls descend in the center of the bed. By injecting fluidization gas, the circulation pattern of the bed could be reversed (i.e. particles descending near the side walls ascend in the center of the bed) for certain conditions. For example, reversal of the gulf stream circulation of particles appeared in the triangular bed for gas superficial velocities higher than the minimum fluidization velocity and sufficiently high values of the vibration strength. This phenomenon is illustrated in Figure 1b in which, for the same vibrating conditions, the injection of gas superficial velocity through the walls reverses the gulf stream motion of particles in the bed. REFERENCES R. Gupta, A.S. Mujumdar, Hydrodynamic of vibrated fluidized bed, Can. J. Chem. Eng., 58:332-338, 1980. Vinayak S. Sutkar, Niels G. Deen, J.A.M. Kuipers, Spout fluidized beds: Recent advances in experimental and numerical studies, Chem. Eng. Sci., 86:124:136, 2013. Please click Additional Files below to see the full abstract

Estudio de la transferencia de calor en la etapa de cocido en la elaboración de aceitunas verdes al estilo sevillano

En este artículo se describe por primera vez a nivel industrial el aumento de temperatura que se produce en el interior de los tanques de elaboración durante la etapa de cocido. A partir del estudio de las características térmicas de la etapa de cocido se han podido determinar relaciones entre las variables que definen el proceso. Se ha demostrado que la temperatura al inicio del tratamiento de cocido influye en otras de las características del proceso como la duración de éste o la pendiente del aumento lineal de temperatura durante la etapa. El estudio establece que esta generación de calor puede provenir principalmente de las reacciones de hidrólisis alcalina que ocurren en el interior del fruto y, en menor proporción, de la dilución de la solución de hidróxido de sodio con el agua presente en la pulpa de las aceitunas

Reversal of gulf stream circulation in a vertically vibrated triangular fluidized bed

Proceeding of: Fifteenth International Conference on Fluidization, Fluidization XV, Fluidization for Emerging Green Technologies, Montebello, Canada, May 22nd to 27th, 2016The present work experimentally assesses the effect of vibration on the dynamics of particles in a fluidized bed of triangular shape. The base of the bed is composed of two inclined walls, each one forming an angle of 45 with the horizontal. The bed has 0.206 m span and 0.01 m thickness. The bed vessel is made of antistatic PMMA in order to allow optical access with a high-speed camera. The bed is mounted on an electrodynamic shaker which produces vertical vibration. The bed material is ballotini particles with a mean diameter of 1.15 mm up to the top of the inclined walls. Air was injected through the inclined bed walls to fluidize the bed to explore whether vibration of the bed vessel together with gas injection can make the dynamics of this bed different to that found when no gas is injected. A high speed camera was used to record the motion of particles in the bed. The velocity of the particles in the bed was obtained via Particle Image Velocimetry (PIV). The results show that several circulation patterns are observed as a function of vibration amplitude and frequency when the fluidization velocity is just below and above the minimum fluidization velocity. Noticeably, for zero gas velocity, particles ascend close to the side walls and descend in the center of the bed. By injecting fluidization gas, the circulation pattern of the bed can be reversed (i.e. particles descending near the inclined walls and ascending in the center of the bed). Conditions for which this reversal of the gulf stream circulation of particles appears in the triangular bed are explored in this work and these include gas superficial velocities higher than the minimum fluidization velocity and sufficiently high values of the vibration strength.This work has been partially funded by the Universidad Carlos IIIde Madrid (Ayudas a la movilidad 2015) and by the Spanish Ministry of Economy and Competitiveness (project ENE2015/00188/001)

Segregation of equal-sized particles of different densities in a vertically vibrated fluidized bed

Many operations in the chemical and energy-conversion industries rely on the fluidization of heterogeneous materials. During fluidization, particles of different densities can segregate, even if they are of the same size. Segregation is typically an undesired phenomenon, especially in fluidized bed reactors (1). Thus, an understanding of segregation on a fundamental level is paramount to identify effective measures to control it. One approach to control segregation could be the vibration of the bed vessel. However, there is very little literature available concerning the effect of vibration on density-induced segregation dynamics (2). Thus, this work studies the influence of vibration on density-induced segregation dynamics in a gas fluidized bed. Experiments were carried out in a pseudo-2D bed of 0.2 m width, 0.5 m height and 0.01 m thickness. The bed was filled with black, ballotini spheres (density 2500 kg/m3) mixed with heavier, white, ceramic particles (density 4100 kg/m3 and 6000 kg/m3). All particles have an average diameter of 1.1 mm. The bed was fluidized by air and vibrated by an electrodynamic shaker. High-speed images were recorded through the transparent front wall of the bed. Digital Image Analysis (DIA) was used to characterize the rate and extent of particle mixing with time (see Figure 1). At the start of the experiments the particles were mixed. The results obtained indicate that both the vibration strength and the gas velocity have an important effect on both the rate and the maximum degree of segregation of particles. We observed that particles become segregated for fluidization velocities greater than the minimum fluidization velocity of the denser particles. Adding vertical vibration to this system tended to enhance density-induced segregation. Interestingly, we found that, for sufficiently high vibration strengths, the degree of segregation decreased with vibration. These results indicate that by a judicious choice of the vibration strength and the fluidization velocity density-induced segregation can be controlled. REFERENCES W-C. Yang, Handbook of fluidization and fluid-particle systems, CRC Press, 2003. L. Sun, F. Zhao, Q. Zhang, D. Li, H. Lu, Numerical simulation of particle segregation in vibration fluidized bed, Chem. Eng. Technol., 37(12):2109-2115, 2014. Please click Additional Files below to see the full abstract

Segregation of equal-sized particles of different densities in a vertically vibrated fluidized bed

Proceeding of: Fifteenth International Conference on Fluidization, Fluidization XV, Fluidization for Emerging Green Technologies, Montebello, Canada, May 22nd to 27th, 2016The present work experimentally studies the influence of vibration and gas velocity on the density-induced segregation of particles in a pseudo-2D vibrated fluidized bed. One half of the particles of the bed are ballotini spheres of density 2500 kg/m(3) and the other half are heavier ceramic particles of density 4100 kg/m(3) or 6000 kg/m(3). Digital Image Analysis is used to characterize the rate and extent of particle mixing with time for different gas velocities, vibration amplitudes and frequencies. The results of the experiments indicate that the vibration strength and the gas velocity have an important effect on both the evolution and the final extent of density-induced particle segregation. It was observed that by introducing vertical vibration to a bed that is fluidized close to minimum fluidization conditions the rate of segregation and the final segregation index of a mixture of light and dense particles is enhanced. However, for vibration strengths greater than a critical value around 3-4, the degree of segregation decreases due to a more vigorous three dimensional mixing of particles in the bed.This work has been partially funded by the Universidad Carlos III de Madrid (Ayudas a la movilidad 2015) and by the Spanish Ministry of Economy and Competiveness (project ENE2015/00188/001)

The onset and dynamics of avalanches in a rotating cylinder: From experimental data to a new geometric model

Particle image velocimetry has been applied to measure particle velocities on the free surface of a bed of particles within a rotating cylinder during avalanching. The particle velocities were used to examine the validity of existing avalanche models and to propose an alternative model. The movement of particles depends on their location on the surface of the bed: particles located near the center of the bed travel the farthest, while the distance travelled decreases at an increasing rate for particles located farther from the center. The start of an avalanche can be determined to a single initiation point, that can also be located on the bottom half of the bed; the avalanche quickly propagates through the entire free surface, with 90% of the surface in motion within 257 ms. The experimental insight is used to formulate a new geometric model, in which three equal sized sections flow down the bed during an avalanche. The predictions of the model are confirmed by experimental mixing measurements

Study of the heat transfer during the alkaline treatment in the processing of Spanish Style green table olives

En este artículo se describe por primera vez a nivel industrial el aumento de temperatura que se produce en el interior de los tanques de elaboración durante la etapa de cocido. A partir del estudio de las características térmicas de la etapa de cocido se han podido determinar relaciones entre las variables que definen el proceso. Se ha demostrado que la temperatura al inicio del tratamiento de cocido influye en otras de las características del proceso como la duración de éste o la pendiente del aumento lineal de temperatura durante la etapa. El estudio establece que esta generación de calor puede provenir principalmente de las reacciones de hidrólisis alcalina que ocurren en el interior del fruto y, en menor proporción, de la dilución de la solución de hidróxido de sodio con el agua presente en la pulpa de las aceitunas

Quality attributes of table olives as affected by regulated deficit irrigation

8 páginas.-- 1 figuras.-- 6 tablas.-- 31 referencias© 2015 Elsevier Ltd. Regulated deficit irrigation (RDI) allows us to decrease the amount of water to apply without significantly affecting yield and fruit quality. The influence of 3 irrigation treatments [T0: control (no stress); T1: moderate stress during pit hardening; and, T2: low stress at the end of flowering stage and moderate during pit hardening) on the quality of table olives, cv. '. Manzanilla', was evaluated. The parameters evaluated in table olives (after processing) were: weight, size, texture, color, fatty acids, volatile compounds and sensory quality. T1 olives had the highest weight and size, and were rounded. Color coordinates L* and b* had the highest values in T2 olives. Aldehydes and monounsaturated fatty acids predominated in T0 olive fruits, while terpenes and polyunsaturated fatty acids predominated in T1 fruits, and finally saturated fatty acids were abundant in T2 olives. Finally, the results of sensory studies indicated that global acceptance was higher for T1 olive, obtaining better satisfaction degrees for fresh olive flavor, crunchiness, and global satisfaction. Deficit irrigation is effective and can be a good alternative for this type of crop, '. Manzanilla' table olives.The authors are grateful to the projects AGL2013-45922-C2-1-R yAGL2013-45922-C2-2-R (Ministerio de Economía y Competitividad, Spain). Besides, Marina Cano-Lamadrid was funded by the Universidad Miguel Hernández de Elche through an “introduction to research” scholarship.Peer Reviewe