Multiscale characterization of nanoparticles in a magnetically assisted fluidized bed
Publication date: Available online 3 December 2019Source: ParticuologyAuthor(s): F. Karimi, M. Haghshenasfard, R. Sotudeh-Gharebagh, R. Zarghami, N. MostoufiAbstractPressure fluctuations of a fluidized bed of nanoparticles were measured during the fluidization of nanoparticles with and without a magnetic field at a frequency of 50 Hz. Recurrence quantification analysis (RQA) and wavelet transform were used to determine the frequency range of various flow structures in the bed at three scales. The frequency ranges of the macro-, meso-, and micro-structures were determined to be 0–49 Hz, 49–781 Hz, and 781...
Source: Particuology - December 4, 2019 Category: Science Source Type: research
Establishment and verification of a model for the movement of pulverized sweet sorghum stalks in a rotary drum bioreactor by discrete element method
In this study, a soft rod-shaped discrete particle model was established and verified to simulate the mixing behavior of sweet sorghum stalk particles in a rotary drum bioreactor. We were inspired by the particle shape and established a rod-shaped particle model by investigating the influence of the shape (length–diameter ratio) and size (diameter) on the particle packing (stack height and bed porosity). We used orthogonal simulations and extremum difference analysis to determine the main factors, optimum level, and groups of other parameters. Based on calibrated parameters, twelve sets of simulations of radial mixing in...
Source: Particuology - December 1, 2019 Category: Science Source Type: research
Particle formulation of hydroalcoholic rosemary (Rosmarinus officinalis L.) extracts using a spouted bed
In this study, spouted bed technology was applied to the protection and functionalization of polyphenolic rosemary extracts. First, solid–liquid extraction was performed at 25 °C with ethanol–water. The ethanol–water ratio was chosen to obtain high phenolic acid and diterpene concentrations in the extract. The selected solvent composition gave liquid extracts that could be directly added to a coating mixture for feeding into a spouted bed apparatus. Thus, no preliminary solvent exchange or evaporation of the extraction solvent to dryness was required. Food grade Paselli MD 6 maltodextrin and HiCap 100 modified ...
Source: Particuology - November 28, 2019 Category: Science Source Type: research
Evaluation of thermophoretic effects on graphite dust coagulation in high-temperature gas-cooled reactors
This study presents a theoretical and numerical analysis of the thermophoretic effects on aerosol coagulation within these reactors. The coagulation rates for Brownian versus thermophoretic coagulation are calculated and compared for various temperature gradients. Our results show that thermophoretic coagulation dominates over Brownian coagulation for large temperature gradients. We defined an enhancement factor to evaluate the role of thermophoretic coagulation under various reactor conditions. The enhancement factor increased dramatically with increasing temperature gradient, decreasing pressure and increasing particle d...
Source: Particuology - November 19, 2019 Category: Science Source Type: research
Simulations of sorbent regeneration in a circulating fluidized bed system for sorption enhanced steam reforming with dolomite
Publication date: Available online 11 November 2019Source: ParticuologyAuthor(s): Kiattikhoon Phuakpunk, Benjapon Chalermsinsuwan, Sompong Putivisutisak, Suttichai AssabumrungratAbstractIn this work, the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production, and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome. However, the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2. The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production, with both re...
Source: Particuology - November 12, 2019 Category: Science Source Type: research
Comparative analyses/evaluation of the textural properties of naproxen sodium tablets and powders prepared using microwave and other drying techniques
This study aimed to explore the correlation between the textural characteristics of the tablets and their respective powders for different drying methods. Although the morphologies of the dry particles were irregular, the prepared tablets were smooth and flat with few cracks. Drying increased the amorphous nature of the granules but decreased their crystallinity. The crystallinities of all tablets, except those prepared by VD, decreased after compression. In summary, the characteristics of the prepared tablets were acquired from their respective powders.Graphical abstract (Source: Particuology)
Source: Particuology - November 3, 2019 Category: Science Source Type: research
Phase field simulation of dendrite growth in gas atomized binary Al–Ni droplets
In this study, a phase field model for simulating single and multiple dendrite growth in a binary Al–Ni alloy was constructed and the microstructural evolutions occurring during a gas atomization process were evaluated. Temporal variations in the heat transfer coefficient and the boundary heat flux were taken into account. The results revealed that the heat transfer coefficient of the atomized droplet in flight is correlated with the droplet size and the relative velocity between the droplet and the atomizing gas. During the simulation, the competition between boundary heat flux extraction and latent heat release from ph...
Source: Particuology - October 25, 2019 Category: Science Source Type: research
CFD-DNS simulation of irregular-shaped particle dissolution
Publication date: Available online 24 October 2019Source: ParticuologyAuthor(s): Hui Cao, Xiaodong Jia, Yongliang Li, Carlos Amador, Yulong DingAbstractA coupled approach between the conventional computational fluid dynamics platform COMSOL and an in-house-developed direct numerical simulation code DigiDiss is presented to study the dissolution kinetics of an irregular-shaped particle in a stirred cuvette. The complex flow dynamics from COMSOL were imported into DigiDiss as an initial flow condition. A digitised 3D particle structure scanned and reconstructed by X-ray micro-tomography was used in the dissolution simulation...
Source: Particuology - October 25, 2019 Category: Science Source Type: research
Sensitivity analysis of mesoscale structural parameters for simulation of fluidized beds
This study presents new numerical drag models with which to analyze the sensitivity of mesoscale structural parameters in bubbling, turbulent, and circulating fluidized beds. The drag models are derived using the method of transfer-coefficient-based structural parameters (TC-SP). Analyzing the sensitivity of the structural parameters reveals that the coefficients associated with drag are more sensitive to parameters in the dense phase than to those in the dilute phase, especially the superficial slip velocity. On the basis of these results, the TC-SP drag model is simplified further. Interestingly, despite having half the ...
Source: Particuology - October 22, 2019 Category: Science Source Type: research
Improving circulating fluidized bed dehydrogenation technology through optimization of fluidization
This study provides insights into means of improving fluidization behavior and highlights the viability of employing a systematic approach to determine the underlying root causes of issues in a commercial CFB reactor unit.Graphical abstract (Source: Particuology)
Source: Particuology - October 12, 2019 Category: Science Source Type: research
Modeling the axial hydrodynamics of gas–solid counter-current downers
Publication date: Available online 5 October 2019Source: ParticuologyAuthor(s): Juanbo Liu, Xinhua Liu, Zhixin Zhang, Hui Zhao, Wei GeAbstractGas–solid counter-current downer reactors, in which particles move downward in an upward gas flow, can achieve high solid concentration for high heat and/or mass transfer rates. However, the particles may reverse their direction or even be carried out of the reactor as the gas flow rate increases. This is closely related to “flooding” in counter-current flows. The energy minimization multiscale (EMMS) model well describes multiscale heterogeneity in gas–solid cocurrent upward...
Source: Particuology - October 5, 2019 Category: Science Source Type: research
Simulation of aggregation effects on co-fired biomass-coal ash in an electrostatic precipitator
Publication date: Available online 26 September 2019Source: ParticuologyAuthor(s): Jianyi Lu, Zhe Yang, Bingyi Xu, Zhiyong Zhou, Chenxi SunAbstractAggregation of fine ash into larger particles benefits fly ash removal in an electrostatic precipitator. Thermal aggregation, turbulent aggregation, and electrical aggregation of fine ash (derived from co-firing of biomass fuel and anthracite coal) was simulated under different conditions in an electrostatic precipitator. A population balance model and user-defined function in Fluent were assumed to obtain aggregation kernel functions and calculate the aggregation effects on the...
Source: Particuology - September 27, 2019 Category: Science Source Type: research
Mineral dust resuspension under vibration: Onset conditions and the role of humidity
This study provides guidelines for managing resuspension of granular soils subjected to vibrations.Graphical abstract (Source: Particuology)
Source: Particuology - September 24, 2019 Category: Science Source Type: research
Pressure recovery characteristics for a dilute gas–particle suspension flowing vertically downward in a pipe with a sudden expansion: A two-fluid modeling approach
Publication date: Available online 10 September 2019Source: ParticuologyAuthor(s): Santosh Kumar Senapati, Sukanta Kumar DashAbstractThis work applies the Eulerian‒Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas–particle suspension flowing through a pipe with a sudden expansion at a relatively higher solid loading. To do so, the numerical procedure was validated against experimental results for relatively small dilute phase flows in a pipe with a sudden expansion; a satisfactory agreement was obtained...
Source: Particuology - September 11, 2019 Category: Science Source Type: research
Effect of impeller type on mixing of highly concentrated slurries of large particles
Publication date: Available online 6 September 2019Source: ParticuologyAuthor(s): Argang Kazemzadeh, Farhad Ein-Mozaffari, Ali LohiAbstractMany chemical engineering processes deal with dense suspensions of large solid particles in liquid. Behaviors of such systems are difficult to predict because the many solid particles strongly affect the hydrodynamics produced by the impeller. The main objective was to assess the performances of the PBT, A310, and PF3 impellers in agitating highly concentrated slurries of large particles. Electrical resistance tomography was used to determine the degree of homogeneity and solid particle...
Source: Particuology - September 7, 2019 Category: Science Source Type: research
