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Polycrystalline particles with a roughly spherical shape (spherulites) have been identified in the industrial production of an aromatic amine derivative, where powder handling is one of the downstream processes following crystallization. This comparative study focuses on how uniaxial flow functions as measures of flowability of dry material of L-glutamic acid and an aromatic amine are affected by the crystal morphology and size, as analyzed by the chord length distribution measurements (FBRM) and scanning electron microscopy (SEM). L-glutamic acid was chosen as a model substance since it can be crystallized as spherulites as well as needle-shaped and polyhedral particles. Failure strength values were measured as a function of consolidation stress using the uniaxial tester. The failure strength values of L-glutamic acid were found to be lower for polyhedral particles than for needle-shaped particles with approximately the same mean chord length. Needle-shaped particles were found to have lower values for failure strength than L-glutamic acid spherulites with smaller chord lengths. It has been shown that spherulites are more unstable with respect to particle breakage than the other morphologies. Although the chord length distributions of the L-glutamic acid spherulites were shifted towards smaller values than those of the aromatic amine spherulites, the failure strength of the aromatic amine particles is more than four times as large. This can be explained by more extensive particle breakage during filtration, sample storage, and consolidation of the aromatic amine.  相似文献   
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The purpose of this study was to investigate the effect of solvent type on the solidification rate of ethyl cellulose (EC) microparticles and particle size/distribution of emulsion droplets/hardened microparticles during the solvent evaporation process using focused beam reflectance measurement (FBRM). EC microparticles were prepared with a water‐in‐oil‐in‐water solvent evaporation method using various solvents, including dichloromethane, dichloromethane–methanol (1:1), ethyl acetate and chloroform. The particle size/distribution of the emulsion droplets/hardened microparticles was monitored using FBRM. The morphology of EC microparticles was characterized using scanning electron microscopy (SEM). The transformation of the emulsion droplets into solid microparticles for all solvents occurred within the first 10–90 min. The square weighted mean chord length of EC microparticles prepared using chloroform was smallest, but the chord count was not the highest. The chord length distribution (CLD) measured by FBRM showed that a larger mean particle size gave longer CLD and a lower peak of particle number. SEM data revealed that the morphology of microparticles was influenced by the type of solvent. FBRM can be employed for online monitoring of the shift in the microparticle CLD and detect transformation of emulsion droplets into solid microparticles during the solvent evaporation process. The microparticle CLD and transformation process were strongly influenced by solvent type. © 2017 Society of Chemical Industry  相似文献   
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Precipitation of concentrated titanyl sulphate is an important step in the Sulphate Process used for manufacturing titanium white in which titanium dioxide particles are formed and the particles size as well as its distribution is determined. This study investigated the transient changes of TiO2 precipitation process by using two on-line particle measurement techniques, turbidimeter and focused beam reflectance measurement (FBRM), in order to explore the mechanism of particles formation. Induction period as well as primary nuclei formation of the precipitation process was calculated by turbidity value changes and the influence of feeding rate on primary nucleation, primary crystal sizes and final product particle size distribution (PSD) were also investigated. FBRM was employed for detecting the transient variations of PSD during the process. It was found that the process was divided into four stages: induction, rapid hydrolysis and aggregation, aggregation balance with further reaction, and ripening. The Sigmoidal–Boltzmann model is used to describe these transient phenomena and describes well the formation of TiO2 particles.  相似文献   
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《分离科学与技术》2012,47(14):3732-3754
Abstract

The effect of charge density of 5 cationic polyacrylamides (C-PAMs) and 3 anionic polyacrylamides (A-PAMs) in single and in dual treatments with a coagulant on the flocculation and removal of dissolved and colloidal material by dissolved air flotation (DAF) in papermaking has been studied. In single systems, good results were achieved both with low and high charge C-PAMs (1.0 and 3.0–3.5 meq/g). In dual systems, high charge C-PAMs (3.0–3.5 meq/g) and A-PAMs (1.5 meq/g), were the most efficient. Results show that monitoring flocculation by a focused beam reflectance measurement (FBRM) allows papermakers to optimize the chemical dosages to maximize the separation efficiency of DAF units either with single or dual systems, which is not always possible with traditional methods as charge titration.  相似文献   
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In ice cream and sorbet manufacturing small ice crystals are desired to deliver a product with a smooth texture and good palatability. This research studied the influence of the operating conditions on the ice crystal size and the draw temperature of the sorbet during the freezing process. The evolution of ice crystal size was tracked with the focused beam reflectance measurement (FBRM) technique, which uses an in situ sensor that makes it possible to monitor online the chord length distribution (CLD) of ice crystals in sorbets containing up to 40% of ice. The refrigerant fluid temperature had the most significant influence on the mean ice crystal chord length, followed by the dasher speed, whereas the mix flow rate had no significant influence. A decrease in the refrigerant fluid temperature led to a reduction in ice crystal size, due to the growth of more small ice crystals left behind on the scraped wall from previous scrapings. Increasing the dasher speed slightly reduced the mean ice crystal chord length, due to the production of new small ice nuclei by secondary nucleation. For a given refrigerant fluid temperature and dasher speed, low mix flow rates resulted in lower draw temperatures, due to the fact that the product remains in contact with the freezer wall longer. High dasher speeds warmed the product slightly, due to the dissipation of frictional energy in the product, the effect of which was in part moderated by the improvement in the heat transfer coefficient between the product and the freezer wall.  相似文献   
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In this paper, the theory on the translation of a measured chord length distribution (CLD) into its particle size distribution (PSD), which was developed in the first part of this study [Li and Wilkinson, 2005. Determination of non-spherical particle size distribution from chord length measurements. Part 1: theoretical analysis. Chemical Engineering Science 60, 3251-3265], has been validated using experimental results. CLDs were measured using the Lasentec focused beam reflectance measurement (FBRM) with three different materials, spherical ceramic beads and non-spherical plasma aluminium and zinc dust particles. Meanwhile, the particle shape and PSD of each material were also investigated by image analysis (IA). Comparison of the retrieved PSDs with the measured PSDs by IA shows that the PSD can be retrieved from a measured CLD successfully using the proposed iterative nonnegative least squares (NNLS) method based on the PSD-CLD model.  相似文献   
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A procedure for the calculation of chord length distributions (CLD) of populations of rigid and opaque particles of any size and shape distribution is given. It combines the capabilities of a virtual reality renderer to create 2D projections of particles and of an image analysis software which determine their chord lengths. The procedure has been validated on simple shapes (spheres, ellipsoids, parallelepipeds, cuboids, uniform polyhedra) that can be combined to simulate agglomerates or twinned crystals. The procedure has been used to discuss the experimental results obtained on gibbsite particles in different size ranges and to compare the mean chord length to the average particle size.  相似文献   
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In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.  相似文献   
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