|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | Spouting behaviour of binary mixtures in square-based spouted beds显示文摘From experime nts, the influe nee of the physical characteristics of different bin ary mixtures of solids on the spouting regime of a pyramidal square-based spouted bed reactor is assessed. The applied methodology permits a more precise evaluation of the effects of the tested variables (diameter, density, sphericity) on the response variables (minimum air flows at which spouting begins and at which to maintain spouting con ditions). The associated pressure drops along the bed of particles a nd the height of the formed fountai n are analysed in each case. During the initial stages of fluidisation, binary mixtures containing different density ratios show dead zones. Segregation becomes more evident at large-size and high-density ratios. The lack of sphericity was found to be the main reason leading to blocking, channelling, and start-up problems when system failures occur. Nevertheless, the extent of segregation in all cases decreases with increasing the spouting velocity. In addition, a computational fluid dynamic model based on the discrete element method, previously validated for a single solid bed, is proposed as a tool to predict and evaluate potential segregation phenomena in binary mixtures. This model reproduced with high accuracy the encountered segregation phenomena. Its use may help define the technical limts inherent in the pyramidal spouted bed reactor. | Cristina Moliner Filippo Marchelli Massimo Curti Barbara Bosio Giorgio Rovero Elisabetta Arato | 2019 | Particuology2019，17，2： | 4 |
| 2 | Simulation of spray coating in a spouted bed using recurrence CFD显示文摘Although numerical models such as the computational fluid dynamics–discrete element method (CFD–DEM) have enabled the accurate simulation of laboratory-scale apparatuses, the application of these methods to large-scale apparatuses with many particles and time scales ranging from minutes to hours remains a challenge. The recently developed recurrence CFD (rCFD) method seeks to overcome these issues in pseudo-periodic processes by extrapolating globally recurring patterns in a physically meaningful way and describing the transport and interaction of passive scalars using Lagrangian tracers. Spouted beds represent an interesting target because of the associated variety of flow regimes. They can be effectively described by CFD–DEM on the time scale of tens of seconds, whereas industrially relevant processes typically take hours. In this contribution, we established the validity of applying the Lagrangian rCFD method to spouted beds by demonstrating the accurate reproduction of the particle residence time distribution in a fictitious spray zone. The deposition of spray droplets onto tracer particles was simulated for 1 h, and the particle surface coverage distribution was estimated using a statistical approach for both an unstabilized prismatic spouted bed and one stabilized by draft plates. | Paul Kieckhefena Thomas Lichtenegger Swantje Pietsch Stefan Pirker Stefan Heinrich | 2019 | Particuology2019，17，1： | 2 |
| 3 | Novel technique for measurement of coating layer thickness of fine and porous particles using focused ion beam显示文摘A novel technique for the measurement of the coating layer thickness of fine particles was developed in this work based on cross-sectioning of micrometre-sized single coated particles using focused ion beam (FIB) milling. This technique was tested on two batches of aerogel particles coated with thin coatings in a spouted bed. The FIB milling procedure consisted of two steps. First, the desired part of the coated particle was removed using a high ion beam current. The resulting cross-sectioned area was then polished using a lower ion beam current to make the cross-section clearly visible. The FIB milling process was controlled with simultaneous scanning electron microscopy (SEM). Afterwards, the coating layer thickness was evaluated using the SEM images. The coating layer was successfully applied on the porous aerogel microparticles in the spouted bed. The coating uniformity of the highly porous particles increased with increasing sprayed coating solution amount, with up to 91% of the particle pores being covered. The FIB-cross-sectioning technique using an ion beam of 2.50 nA for the first milling and 0.43 nA for polishing of the surface resulted in successful generation of cross-sections of representative particles with a visible particle core and coating layer. A coating layer thickness of approximately 700 nm was achieved on particles with sizes of below 45 μm. | M. Goslinska I. Selmer C. Kleemann U.Kulozik I. Smirnova S. Heinrich | 2019 | Particuology2019，17，1： | 1 |
| 4 | A novel approach to correlate heat transfer and pressure fluctuation in gas-solid spouted bed显示文摘Statistical analysis of pressure fluctuations in spouted beds has been used as a well-established diagnostic tool to determine bed and flow characteristics because of its smooth operation. However, in many recent and conventional applications of spouted beds such as drying, coal gasification, catalytic conversion, biomass treatment, and chemical vapor deposition, direct estimation of the heat transfer rate from the solid bed to the gas or vice versa has proven to be difficult. A variance and spectral analysis of pressure fluctuation is extended here to characterize the heat transfer phenomena in a spouted bed. In the present study, zirconia and alumina were used as the bed materials, and argon and nitrogen were used as the spouting gases. Experiments were conducted at various heating rates for different superficial gas velocities for a range of temperatures up to 300 °C. Significant changes in the gas density and viscosity with different extents of heat transfer were observed to affect the momentum diffusivity and gas–particle interaction, which in turn led to local pressure fluctuations, causing the bed to behave differently. In the present work, a novel approach is proposed to establish a link between local pressure fluctuation and the extent of heat transfer in the bed. This method shows potential for correlation of the statistics of pressure fluctuation with the thermal properties of individual solids and gases. Thus, the technique can be extended to many industrial applications for the indirect estimation of the extent of heat transfer and prediction of unknown thermal properties of products in solids or gases. | P.K. Mollick P.S. Goswamib M. Krishnana P.K. Vijayanc A.B. Panditd | 2019 | Particuology2019，17，1： | 1 |
| 5 | Surface-to-bed heat transfer for high-density particles in conical spouted and spout–fluid beds显示文摘Bed-to-surface heat transfer experiments from a vertically submerged cylindrical surface were conducted in laboratory-scale (Dc = 25 cm) conical spouted and spout–fluid beds at two different conical angles (31° and 66°) in the high particle density range (2500 kg/m3 ≤ρp ≤ 6000 kg/m3). The effects of the bed design parameters (conical angle and inlet diameter of spouting gas entrance) and operating conditions (static bed height, particle size, density, and spouting and fluidization gas flow rates) on the heat transfer characteristics were investigated in detail. The heat transfer coefficients were shown to be dependent on the density and size of the particles. The minimum stable spouting velocities of the denser and larger particles were higher, which led to higher operational spouting velocities and thereby resulted in higher heat transfer coefficients. The positive effect of increasing the particle diameter on heat transfer was more pronounced in the spout and at the spout–annulus interface, whereas this effect was diminished in the annulus region. The heat transfer coefficient increased with increasing spouting gas velocity up to 1.0Ums–1.1Ums, beyond which no significant change was observed regardless of the particle type. The heat transfer coefficient in the annulus decreased with increasing conical angle because of reduced particle circulation. The spout–fluid operation increased the heat transfer coefficient by a maximum of 10% at the expense of a significant increase of the total gas flow rate. This result was attributed to the inability of the fluidizing gas to penetrate the annulus. An empirical correlation for the average heat transfer coefficient in the annulus was also proposed based on the data obtained in this work. | Onur Yaman Gorkem Kulaha Murat Koksalb | 2019 | Particuology2019，17，1： | 1 |
| 6 | Comparison of artificial neural networks with empirical correlations for estimating the average cycle time in conical spouted beds显示文摘Conventional spouted beds have been extensively used in many real-life applications but are not suited for all types of materials, especially fine particles, which require internal devices to improve their motion in the spouted bed. However, unlike conventional spouted beds, there are almost no mechanistic or empirical models available for the design of spouted beds with internals. Given the availability of an extensive but not experimentally designed database, the main purpose of this study is to present an analysis of neural networks and empirical models in terms of their suitability to fit and predict average cycle times in conical spouted beds with and without draft tubes. The parameters investigated are particle size, density, contactor angle, gas inlet diameter, static bed height, and draft tube features. Although the amount of information is always a key factor when fitting models, the size of the database used in this study strongly affects the fitting performance of empirical models, whereas artificial neural networks are more influenced by how the data are scaled. Results of model verification show that both techniques are suitable for predicting average cycle times for data outside the range covered by the database. | I. Estiatia M. Tellabidea J.F. Saldarriaga H. Altzibara F.B. Freirec J.T. Freirec M. Olazara | 2019 | Particuology2019，17，1： | 1 |
| 7 | Spouting behavior of binary particle mixtures of different densities: Fluid dynamics and particle segregation显示文摘Numerous industrial applications of spouted beds involve a mixture of granular particles, where differences in particle size, density, and shape can cause particle segregation, affecting the quality of flow and decreasing product homogeneity. The aim of this study was to investigate the particle segregation and fluid dynamics of a conical spouted bed operating with a binary mixture of particles of different densities. Using glass beads and polyethylene particles with a diameter of 4 mm, we determined the effects of the mass fraction of denser particles and static bed height on the minimum spouting condition and mixture index. The pressure drop and airflow in the minimum spouting condition increased with an increase in bed height or jetsam concentration. Regarding particle segregation, the jetsam particles tended to concentrate near the bottom, at the spout–annulus interface because they have a shorter trajectory than the lighter particles in the fountain region. Jetsam-rich mixtures with high initial static bed heights exhibited more efficient particle mixing, excluding those at the bottom of the bed. | K.G. Santos R.C. Santana D.L. Souza V.V. Murata M.A.S. Barrozo | 2019 | Particuology2019，17，1： | 1 |
| 8 | CFD–DEM simulation of fine particles in a spouted bed apparatus with a Wurster tube显示文摘In this work, a coupled computational fluid dynamics–discrete element method (CFD–DEM) approach was employed to evaluate the spouting behavior of fine, cohesive powders in a cylindrical spouted bed with a conical base and equipped with a Wurster tube. The particle and gas dynamics inside the apparatus were simulated with 1.7 million spherical ZrO2 particles with a particle size of 100 μm. For an accurate prediction of the interactions of cohesive particles in the spouted bed, the adhesion forces according to JKR theory were included in the Hertz–Tsuji contact model. The surface energy of the particles was varied over a wide range to determine the effect of the adhesion on the spouting (the fountain shape and maximum height as well as the distribution of the concentrations and velocities of particles in different zones of the apparatus). A detailed analysis of the collision dynamics was conducted. The spouting behavior of a spouted bed with the same dimensions, particles, and processing parameters was recorded with a high-speed camera. The CFD–DEM simulations showed good agreement with the experimentally captured spouting behavior. | Paul Breuninger Dominik Weis Isabell Behrendt Philipp Grohn Fabian Krull Sergiy Antonyuk | 2019 | Particuology2019，17，1： | 1 |
| 9 | A novel method of quantifying the coating progress in a three-dimensional prismatic spouted bed显示文摘An optical method of experimentally quantifying the coating progress in a laboratory prismatic spouted bed is presented. Microcrystalline cellulose particles with size dp = 0.57 mm are used as core material. Waterborne coating suspensions with methylene blue as a dye are used and sprayed via a two-fluid nozzle in bottom-spray configuration. A high-speed camera with a color filter is positioned in front of the observation window of the three-dimensional plant and records the flow pattern in the process chamber with a certain frequency. With increasing surface coverage, the particles become bluer and darker. The change in brightness is detected by digital image analysis. In the implemented algorithm, the spherical particles are detected, cut from the background and normalized regarding their lighting and area. The detection of coated pixels on the single particles allows the calculation of the coating fraction and coating uniformity after a Kalman filter has been applied to reduce noise. It is shown that the method can be used to determine the time needed to reach the maximum blue value indicating a complete coating of the particle bed. Besides the minimum coating duration, information on the spraying performance (e.g., the time point of a possibly occurring blockage of the nozzle) can be obtained from the data. Two exemplary experiments are presented, showing a connection of the slope of the coating fraction and the uniformity of the coating of the particles in the apparatus that results in the recommendation of a slow liquid injection for obtaining consistent coating layers as desired in many applications. | Swantje Pietscha Finn Ole Poppinga Stefan Heinrich Michael Müller Michael Schonherr Frank Kleine Jager | 2019 | Particuology2019，17，1： | 0 |
| 10 | Biomass torrefaction in a slot-rectangular spouted bed reactor显示文摘Sawdust was subjected to torrefaction in a 'semi-batch' slot-rectangular spouted bed (SRSB) reactor at temperatures from 240 to 330℃ and biomass feed rates from 220 to 710g/h.Stable spouting of the sawdust was achieved in the slot-rectangular spouted bed,although the pressure drop across the reactor was observed to oscillate.Compared to the biomass feed rate,the temperature had a greater effect on the biomass weight loss and energy yield.Increases in temperature were found to promote weight loss of the sawdust while decreasing the energy yield.The main solid product was the torrefied sawdust,which remained in the SRSB reactor and was captured by a cyclone.The ratio of the torrefied biomass removed by the cyclone to the total torrefied biomass increased along with both the feed rate and temperature.After undergoing torrefaction,6.7%-39.2% of the original sawdust mass was lost while 67.4%-98.7% of its energy was retained.The torrefied sawdust had a higher carbon content but less oxygen,hydrogen and volatiles,along with a greater higher heating value and increased density compared to the raw sawdust.The size of the sawdust particles also decreased markedly during the torrefaction process. | Ziliang Wang C. Jim Lim John R. Grace | 2019 | Particuology2019，17，1： | 0 |
| 11 | Production of composites with high relative permittivity using the spouted bed technique显示文摘This contribution presents a new application of the spouted bed technique. The developed production process involves coating fine copper particles with a polymer in a spouted bed plant and then hot pressing the produced granules to form a compact consisting of a copper–polymer composite with a high filling degree. The fabricated composites possess high relative permittivity, which is advantageous for the production of effective capacitors. With increasing filling degree of copper, the relative permittivity of the composites increased, with a maximum relative permittivity of 214 obtained for the composite containing 78.1 vol% copper. Such a high filling degree can be achieved with conductive particles without obtaining a conductive composite by using the spouted bed technology in the production process. The high relative permittivity results from the high filling degree of particles isolated by a polymer coating. | E. Eichner P.-K. Fischer S. Heinrich GA Schneider | 2019 | Particuology2019，17，1： | 0 |
| 12 | Fluid dynamics analysis and pyrolysis of brewer’s spent grain in a spouted bed reactor显示文摘Brewer’s spent grain (BSG) is a large-scale agroindustrial waste that could be more efficiently utilized. This waste is composed of lignocellulosic material and so may serve as a good source of biomass for thermochemical conversion. The present study investigated the fluid dynamics behavior of mixtures of sand and BSG in a spouted bed to assess the viability of the thermochemical conversion of this biomass via fast pyrolysis. Fluid dynamics analyses were performed while varying the mass fraction of BSG (6–80%) and the static bed height (6.6–13.4 cm). Empirical equations for predicting the minimum spouting conditions and the mixing index were obtained using a regression technique, and the selected fluid dynamics parameters were employed in the spouted bed pyrolysis. The bio-oil resulting from this process was rich in phenolic compounds, various nitrogenated compounds (representing precursors for pharmaceuticals) and long-chain hydrocarbons. The products obtained from the analytical and spouted bed pyrolysis processes were also compared. | Marcos A.S. Barrozo Lidja D.M.S. Borel Taísa S. Lira Carlos H. Ataíde | 2019 | Particuology2019，17，1： | 0 |
| 13 | CFD-DEM simulation of a pseudo-two-dimensional spouted bed comprising coarse particles显示文摘In the present study, computational fluid dynamics (CFD) and the discrete element method (DEM) are used in conjunction with the Eulerian-Lagrangian method to simulate a pseudo-two-dimensional spouted bed comprising coarse 6-mm particles. The open-source OpenFOAM code is used to solve the governing equations. The predicted vertical particle velocity along the bed axis, particle velocity profiles in the radial directi on, power spectral den sity, time-averaged particle velocity vectors, bed pressure drop, and solid flow pattern are evaluated and compared with existing experimental data. Good agreement is found between the CFD-DEM results and the measured data. It is also shown that the present CFD-DEM model accurately predicts the particle flow pattern throughout the bed. It is found that the drag force, solid stresses, and gravity play important roles in the CFD-DEM simulation of a spouted bed comprising coarse particles. | B. Mahmoodi S.H. Hosseini G. Ahmadi | 2019 | Particuology2019，17，2： | 0 |
| 14 | Visualization of flow structures inside a conical spouted bed by electrical capacitance volume tomography显示文摘Electrical capacitance volume tomography (ECVT) was conducted to measure instantaneous gas–solid flow structures in a conical spouted bed. The sensor has 24 electrodes/channels and was used to make three-dimensional measurements of the solid volume fraction. Flow structures in the conical spouted bed were analyzed using quantitative ECVT images. Three-dimensional images of gas–solid flow structures and time-averaged vertical and radial solid volume fraction profiles are presented. Different fluidization regimes in spouted beds were characterized by analyzing pressure fluctuation signals and ECVT images. ECVT was shown to be robust and powerful for the three-dimensional visualization and quantitative measurement of a gas–solid fluidization system. | Hoon Chae Park Hang Seok Choi | 2019 | Particuology2019，17，1： | 0 |
| 15 | A hybrid deterministic-stochastic model for spouted beds显示文摘A new hybrid deterministic-stochastic model is developed and used to simulate a slot-rectangular spouted bed.The model includes deterministic and stochastic steps that are executed in turn.The simulation starts with the deterministic part of the model,in which the computational fluid dynamics-discrete element method (CFD-DEM) equations are solved for 1 s to give the initial velocity distribution of the particles.The stochastic part is then executed,with the hydrodynamics of the bed taken from the velocity distributions acquired in the first step through Monte Carlo sampling.A full deterministic (CFD-DEM) simulation of the bed is also conducted for comparison with the proposed hybrid model.Additionally,the proposed hybrid is validated using experimental data from the literature.These validations are based on the axial and lateral velocity distributions of the particles and the bed voidage.The effects of the cell size and number of sampling steps on the accuracy of the model are also investigated.The performance of the proposed model is compared with the CFD-DEM results in terms of the computation time and the rate of solid circulation in the bed.The hybrid model is found to have shorter runtimes than the CFD-DEM approach. | Shahab Golshan Reza Zarghami Navid Mostoufi | 2019 | Particuology2019，17，1： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员