Showing papers on "Breakage published in 2011"
TL;DR: In this article, the effect of initial grading and density on the sample behavior during one-dimensional compression for three sands with distinct mineralogies was examined, and it was found that a unique normal compression line is the outcome of a large amount of breakage in poorly graded samples and that by changing the initial grading to a better graded sample a significant reduction in particle breakage is observed, until for very well-graded samples no significant particle breakages can be measured.
Abstract: It is commonly accepted that the onset of particle breakage in sands during compression marks the start of yielding. Although particle breakage is strongly associated with the tensile strength of a single soil grain, initial density and initial sample grading have great influence on the probability of particle breakage. This paper examines the effect of initial grading and density on the sample behaviour during one-dimensional compression for three sands with distinct mineralogies. It was found that a unique normal compression line is the outcome of a large amount of breakage in poorly graded samples and that by changing the initial grading to a better graded sample a significant reduction in particle breakage is observed, until for very well-graded samples no significant particle breakage can be measured. At this point a difficulty in defining a unique normal compression line for the sample was found and a transitional behaviour was identified. In addition to particle size, the paper examines the changes...
352 citations
TL;DR: In this article, a series of triaxial tests were conducted to investigate the effect of particle breakage on the current location of the critical state line in the void ratio: logarithm of the mean effective stress plane as the grading changes.
242 citations
TL;DR: In this paper, the effect of different mixing times and slow stirring speeds on coagulation and floc properties, using aluminum sulfate as coagulant, under conditions where significant precipitation of an amorphous hydroxide precipitate occurs.
139 citations
TL;DR: In this paper, an elasto-plastic model with two yield surfaces to model the influence of particle breakage has been introduced, which can reproduce with good accuracy the mechanical behavior of crushable granular materials and predict the evolution of the grain size distribution during loading.
Abstract: A particle breakage has a significant impact on the mechanical behavior of granular materials. In this paper, we present an elasto-plastic model with two yield surfaces to which the influence of particle breakage has been introduced. The main feature of this model is to incorporate the change in the critical state line (CSL) consequent to the grain breakage induced by isotropic and deviatoric stresses during loading. For this purpose we propose a breakage function which connects the evolution of the CSL to the energy consumed. Results from earlier studies on drained and undrained compression and extension triaxial tests were used to calibrate and validate the model. Comparison between earlier results and our simulations indicates that the model can reproduce with good accuracy the mechanical behavior of crushable granular materials and predict the evolution of the grain size distribution during loading.
110 citations
TL;DR: The results of this study show that the process of cluster breakup is very complex and strongly depends on the initial aggregate structure and flow-field conditions.
Abstract: In this work we present experimental and simulation analysis of the breakage and restructuring of colloidal aggregates in dilute conditions under shear. In order to cover a broad range of hydrodyna...
101 citations
TL;DR: In this paper, the effect of the powder fill level on the energy efficiency of a ball and stirred mill is investigated, and the authors compare the results with experimental results from a test at similar ball loading and rotation rate and for several size fractions of ore at a range of powder fill fractions.
75 citations
TL;DR: In this article, the breakage behavior of needle-shaped particles as L -threonine crystals and cylindrical Al 2 O 3 agglomerates is studied by compression tests.
67 citations
TL;DR: In this paper, the particle breakage versus energy data are converted into breakage rates via impact energy spectra of the grinding mill computed by a DEM code, and the fundamental material breakage information is converted into energy based breakage distribution function.
61 citations
TL;DR: In this paper, a discrete element method (DFM) for spherical brittle particles is proposed to study the trajectories of individual fragments from the moment of breakage to the cloud formation after breakage.
61 citations
TL;DR: In this article, a general constitutive model of crushable granular materials is developed within the context of large deformations, where the time evolution equations for breakage, inelastic porous compaction and dilation, and distortional deformations are coupled by a yield surface.
60 citations
TL;DR: In this paper, the effect of microwave treatment on the processing of mineral ores was investigated through simulations of microwave heating, thermal damage and confined particle bed breakage test on bonded-particle models.
TL;DR: It is shown that the successive breakage of peripheral branches allows the plant to sustain higher flow forces, and can be seen as a second strategy to overcome critical events, possibly a widespread solution in plants and benthic organisms.
TL;DR: In this article, a method of predicting the extent of breakage occurring due to agitation is described and applied for Paracetamol in a small-scale dryer, where the distributions of stresses and strains in the bed are estimated using the Distinct Element Method (DEM).
TL;DR: In this article, the influence of modulated microwave power on copper ore breakage has been investigated, and it has been shown that very short exposures to a high level of microwave power lead to reductions in ore strength.
TL;DR: In this article, Baldyga et al. used an in situ video probe with automated image analysis to develop a population balance model for a breakage-dominated liquid liquid emulsification system.
Abstract: A novel in situ video probe with automated image analysis was used to develop a population balance model for a breakage-dominated liquidliquid emulsification system. Experiments were performed in a 2 L tank, agitated by an axial flow propeller. The dispersed phase (ethylene glycol distearate) concentration was varied from 0.2 to 1.0% (w/w), and agitation rates werevariedfrom0.2to0.5W/kg,inthepresenceofexcesssurfactant.Threenumericaldiscretizationmethodswerecompared: fixed pivot, cell average, and finite volumes. The latter was then chosen for the subsequent simulations due to its rapidity and higher precision. An investigation of the different theories for bubble/droplet breakage was done and the frequencies (or breakage rate kernels) were compared. Four models were found applicable: the models developed by Coulaloglou and Tavlarides (Coulaloglou, C.A.; Tavlarides,L. L.Chem. Eng. Sci.1977,32,1289);Sathyagal and Ramkrishna (Sathyagal,A. N.; Ramkrishna, D.Chem. Eng. Sci. 1996,51,1377);Alopaeus,Koskinen,andKeskinen(Alopaeus,V.;Koskinen,J.;Keskinen,K.I.Chem.Eng.Sci.1999,54,5887);and BaldygaandPodgorska(Baldyga,J.;Podgorska,W.Can.J.Chem.Eng.1998,76,456).TheonebySathygalandRamkrishnaincluded thedaughtersizedistribution.Alog-normaldaughtersizedistributionwaschosenforthemodelsbyCoulaloglouandTavlaridesand Alopeus et al. Also, a normal distribution was used in the model by Baldyga and Podgorska. These models were compared with the experimental data to allow parameter identification. The model by Baldyga and Podgorska was found to give the best prediction of the shape of the distribution, its mean diameter, and standard deviation.
TL;DR: In this article, a theoretical investigation of the effect of ball diameter on milling kinetics using the attainable region methodology is presented, under a predefined fineness of the grind in the product, reachable region plots are produced and results qualitatively interpreted.
TL;DR: In this paper, a mathematical model for predicting breakage in monolayer unconfined particle beds with a combination of single-particle breakage data and functions that describe energy partition and volume of material captured in the bed was proposed.
TL;DR: In this article, a population balance equation (PBE) model for emulsion drop breakage in a high-pressure homogenizer was developed to predict the effects of formulation variables on the drop size distribution, but the model was not extensible to a range of homogenization pressures.
Abstract: We have previously developed a population balance equation (PBE) model for emulsion drop breakage in a high-pressure homogenizer that incorporated multiple-drop formation within two mechanisms of turbulent drop breakage. The model was found to satisfactorily predict the effects of formulation variables on the drop-size distribution, but the model was not extensible to a range of homogenization pressures. The objective of this paper is to determine the additional model elements necessary to obtain acceptable predictions over a wide range of pressures. The most significant improvements were obtained by increasing the number of daughter drops formed upon breakage from 20 to 150 drops and by introducing a maximum stable diameter, below which drops could not break. Smaller improvements were obtained by introducing terms that describe the loss of energy available for drop breakage due to thermal heating of the sample and homogenizer and by extending the model to account for the effects of surfactant adsorption ...
TL;DR: This contribution presents a combined computational and experimental methodology for determining the breakage kernel and the daughter distribution functions of needle-shaped crystals, and for population balance modeling of their breakage.
TL;DR: In this paper, two mechanisms of nanoparticle breakage are proposed based on these findings, and the authors show that the breakage kinetics strongly depend on the process parameters and suspension conditions as long as the grinding limit is not reached, which leads to a higher product quality in terms of crystallinity and less milling bead wear.
Abstract: In long-term milling experiments, in a stirred media mill, a grinding limit where no further particle breakage occurs was identified. During mechanical stressing of the particles, defects are generated in the crystalline lattice, which allows real fracture of nanoparticles. Below a critical size, defects cannot be stored or generated in the crystallites and the overall limit of grinding is reached. This limit is strongly influenced by material properties and hardly affected by most of the process conditions. However, the breakage kinetics strongly depend on the process parameters and suspension conditions as long as the grinding limit is not reached. Based on these findings, two mechanisms of nanoparticle breakage are proposed. Proper choice of process parameters saves not only up to 90% of the energy input to reach the grinding limit but also leads to a higher product quality in terms of crystallinity and less milling bead wear. © 2010 American Institute of Chemical Engineers AIChE J, 2011
TL;DR: A model of fatigue breakage due to wave-induced forces for the macroalga Mazzaella flaccida strongly suggests that, in addition to occurring predictably in the laboratory, fatigue-induced breakage of M.flaccida occurs on wave-swept shores.
Abstract: SUMMARY Seaweeds inhabiting the extreme hydrodynamic environment of wave-swept shores break frequently. However, traditional biomechanical analyses, evaluating breakage due to the largest individual waves, have perennially underestimated rates of macroalgal breakage. Recent laboratory testing has established that some seaweeds fail by fatigue, accumulating damage over a series of force impositions. Failure by fatigue may thus account, in part, for the discrepancy between prior breakage predictions, based on individual not repeated wave forces, and reality. Nonetheless, the degree to which fatigue breaks seaweeds on wave-swept shores remains unknown. Here, we developed a model of fatigue breakage due to wave-induced forces for the macroalga Mazzaella flaccida . To test model performance, we made extensive measurements of M. flaccida breakage and of wave-induced velocities experienced by the macroalga. The fatigue-breakage model accounted for significantly more breakage than traditional prediction methods. For life history phases modeled most accurately, 105% (for female gametophytes) and 79% (for tetrasporophytes) of field-observed breakage was predicted, on average. When M. flaccida fronds displayed attributes such as temperature stress and substantial tattering, the fatigue-breakage model underestimated breakage, suggesting that these attributes weaken fronds and lead to more rapid breakage. Exposure to waves had the greatest influence on model performance. At the most wave-protected sites, the model underpredicted breakage, and at the most wave-exposed sites, it overpredicted breakage. Overall, our fatigue-breakage model strongly suggests that, in addition to occurring predictably in the laboratory, fatigue-induced breakage of M. flaccida occurs on wave-swept shores.
TL;DR: In this article, the attrition of granules inside a rotary drum at 18, 35 and 52rpm drum rotation speeds for 4000 cycles was studied and the extent of breakage was quantified by sieving out fine debris which is two sieve sizes smaller than the feed particles.
TL;DR: In this paper, the authors explore the influence of floc characteristics on membrane fouling, flocs after breakage and re-growth were compared with those formed by conventional coagulation process when alum was used as coagulant.
TL;DR: The general trends observed in this study are comparable to various applications in multiphase bioreactors and can be applied to simulate transientMultiphase systems at different scales.
Abstract: Understanding of particle strain and drop breakage is relevant for various technical applications. To analyze it, single drop experiments in a breakage cell and evolving drop size distributions in an agitated system are studied. The mechanisms for particle strain and drop breakage are assumed to be comparable for the investigated turbulent flow regime. The agitation process is simulated using a population balance model. This model provides transient prediction capacities at different scales and can be used for scale-up/down projects. The number and the size distributions of daughter fragments for single drops have been studied. The results clearly support the assumption of binary breakage. The most common assumption of a Gaussian distribution for the daughter drop size distribution could not be supported. The evolution of a breakage-dominated toluene/water system was then simulated using different daughter drop size distributions from literature. The computational results were compared with experimental values. All simulations were able to predict the transient Sauter mean diameter excellently but varied strongly in the results on the shape of the distribution. In agreement with the experimental single drop results, the use of a bimodal or a very broad bell-shaped distribution of the daughter drops is proposed for the simulations. Although these results were obtained in a particular vessel for a specific phase system, it can be applied to simulate transient multiphase systems at different scales. We would expect that the general trends observed in this study are comparable to various applications in multiphase bioreactors.
TL;DR: The growth, breakage and regrowth nature of flocs formed by Titanium tetrachloride and polyaluminum chloride was comparatively evaluated with surface water treatment and indicated that the responses ofFlocs to different operating parameters depend on the coagulant used.
TL;DR: In this paper, the grindability of a diasporic ores was studied by wet grinding in a laboratory ball mill and its breakage parameters were determined based on the population balance model (PBM).
TL;DR: In this paper, a non-linear population balance model for rate-based comminution processes is proposed to analyze and model the multi-particle interactions, and the practical applicability, accuracy, and stability aspects of the model are discussed.
TL;DR: In this article, a simplified model for wheat breakage during roller milling is presented, which simplifies the breakage function by normalising the output particle size distribution against the milling ratio raised to a power.
TL;DR: In this article, a series of experiments have been performed to study the breakage behavior of float glass, and the critical time and temperature difference at the 1 breakage are the most important parameters to character the glazing behaviors.
TL;DR: In this paper, the experimental results on dry fine pulverization of alumina particles in a fluidized bed opposed jet mill were investigated in detail and the effect of operating parameters (i.e., feed load, inlet air pressure and the distance between nozzle outlet and jet meeting point) on the grinding results was investigated.