Consideration Of Particle Size Distribution Research Articles

Comparison of CFD-DEM and TFM simulations of single bubble injection in 3D gas-fluidized beds with MRI results

Predictions for bubble and particle dynamics surrounding a single bubble injected into an incipiently cylindrical fluidized bed from CFD-DEM and TFM simulations using different drag laws were compared with prior MRI results. This comparison allows for quantitative assessment of the accuracy of simulations for deterministic behavior of a single bubble as compared to statistical comparisons of chaotic free bubbling behavior as conducted in several prior studies. The comparison shows that simulations capture bubble rise velocity and particle velocity data surrounding bubbles fairly well. However, simulations tend to predict bubble shapes which are taller and narrower with larger wake angles than those observed experimentally. Changing drag laws does not have a significant effect on results, and significant quantitative differences are observed in moving from CFD-DEM to TFM simulations, yet neither provides predictions which are definitively better across a wide range of metrics. Some recommendations, including the use of novel drag laws and frictional solids stress models in TFM as well as the consideration of particle size distribution that may improve the prediction performance, are provided.

Experimental study and CPFD simulation on circumferential flow heterogeneity in a disc-donut catalyst stripper

Abstract Disc-donut strippers are widely equipped in fluid catalytic cracking (FCC) units of petroleum refineries. In this study, circumferential gas-solids flow heterogeneity in a disc-donut catalyst stripper was investigated using both experimental and CFD simulation approaches. A four-channel fiber optical densitometry was used to measure the radial gas-solids profiles synchronously from four different circumferential angles. Computational particle fluid dynamics (CPFD) model was used to simulate the experimental stripper section. It was found in experiment that the circumferential gas-solids distribution is highly heterogeneous throughout the disc-donut stripper. Local gas bypassing existed under all the experimental conditions. The CPFD model successfully predicted gas bypassing and circumferential flow heterogeneity in the disc-donut stripper. However, previous two-fluid model (TFM) simulations on disc-donut strippers using a single mean particle size can only predict axially symmetrical flow distribution. According to a series of sensitivity analyses, it is shown that the consideration of particle size distribution (PSD) is a possible key reason leading to the successful prediction of the circumferential flow heterogeneous by the CPFD model.

Aggregation and Charging Behavior of Polydisperse and Monodisperse Colloidal Epoxy-Amine Adducts

An investigation is presented into the effect of particle size distribution on the aggregation behavior of colloidal dispersions and validity of the Derjaguin-Landau-Verwey-Overbeek(DLVO) theory. The colloidal dispersions of epoxy amine adducts were prepared with various particle size distributions (PSD) and surface charge densities. Moreover, the Fuchs stability ratios W were obtained in aqueous solution with and without consideration of the viscous effects. It was found that PSD of colloidal dispersions affect the reliability of the prediction of DLVO theory. In order to achieve a good agreement between experimental and theoretical critical coagulation concentration (CCC) values of the colloidal dispersions, a new expression with consideration of particle size distribution was introduced.

Modeling of transient permeate flux decline during crossflow microfiltration of non-alcoholic beer with consideration of particle size distribution

► Modeling of transient flux in crossflow MF of rough beer was performed. ► Predict the cake layer composition with different particle sizes at each time step. ► Effect of particle sizes on membrane fouling and cake layer formation studied. ► Better agreement of model with data considering particle size distribution (PSD). Crossflow microfiltration of non-alcoholic beer is investigated numerically and it has been verified by experimental data. Due to the presence of particles with different sizes in feed suspension, a modified combination of three mechanisms of particle back-diffusion is developed to predict particle deposition and cake layer buildup during the process. The simulation results show that smaller particles (about 1 μm) are the main contributor to the cake layer due to a minimum in back transport and are the main reason of the flux decline. On the other hand, larger particles ( a p > 20 μm) are swept away along the membrane during the filtration process and move toward the membrane exit due to the crossflow. Therefore, the cake enriches with finer particles as the permeate flux decreases. The specific cake resistance was determined experimentally and Carman–Kozeny equation fails to provide a complete theoretical perspective of specific resistance of irregular, non-uniformly sized particles that formed the cake layer. The results of numerical simulation are in good agreement with observed data.

Evaluation of the Degree of Mixing of Combinations of Dry Syrup, Powder, and Fine Granule Products in Consideration of Particle Size Distribution Using Near Infrared Spectrometry

We used near infrared (NIR) spectroscopy to evaluate the degree of mixing of blended dry syrup (DS) products whose particle sizes are not specified in the Revised 16th Edition of the Japanese Pharmacopoeia, and also evaluated the degree of mixing when powder products or fine granule products were added to DS products. The data obtained were used to investigate the relationship between the particle size distributions of the products studied and the degree of mixing. We found that the particle size distribution characteristics of the 15 DS products studied can be broadly classified into 5 types. Combinations of frequently prescribed products were selected to represent 4 of the 5 particle size distribution types and were blended with a mortar and pestle. The coefficient of variation (CV) decreased as the percent mass of Asverin® Dry Syrup 2% (Asverin-DS) increased in blends of Periactin® Powder 1% (Periactin) and Asverin-DS, indicating an improved degree of mixing (uniformity). In contrast, in blends of Periactin and Mucodyne® DS 33.3%, mixing a combination at a 1:1 mass ratio 40 times resulted in a CV of 20%. Other mixing frequencies and mass ratios resulted in a CV by 50% to 70%, indicating a very poor degree of mixing (poor uniformity). These results suggest that when combining different DSs, or a DS with a powder or fine granule product, the blending obtained with a mortar and pestle improves as the particle size distributions of the components approach each other and as the ranges of the distributions narrow.

Potassium in Atlantic Coastal Plain Soils: I. Soil Characterization and Distribution of Potassium

AbstractCorn (Zea mays L.) grown on sandy Atlantic Coastal Plain soils is often unresponsive to applications of K fertilizer. As part of a field study on the response of irrigated, intensively managed corn to K applications, we characterized four representative Hapludults from the Delaware Coastal Plain and evaluated their K status. The soils were generally quite sandy with maximum clay contents of 11.4 to 26.5%, had low (≤2.0%) organic matter contents, and had correspondingly low cation exchange capacities (1 to 4 cmolc kg−1 by summation). The clay fractions were dominated by kaolinite and hydroxy‐interlayered 2:1 expansible minerals; the latter may play a crucial role in the overall chemistry of K in these soils. The soils were quite high in total K, with means for the four soils (across horizons) ranging from 23.6 to 43.9 cmolc kg−1, and this was ascribed to the K‐rich parent material and relatively young age of these soils. Most (97–98%) of the total K was in mineral forms, and the majority (65–87%) was in the sand fractions, virtually all as K‐feldspars. Exchangeable and nonexchangeable (fixed) K levels were relatively low and were of comparable magnitude. Consideration of particle size distribution, K distributions, and published studies of weathering rates suggested that the sand fractions of these soils represent significant sources of plant‐available K.