摘要 :
Numerous companies working in the field of agglomeration exhibited at the ACHEMA 2018. The presented technologies range from tumble agglomeration to extrusion and press agglomeration in the fields of mineral, renewable and biogeni...
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Numerous companies working in the field of agglomeration exhibited at the ACHEMA 2018. The presented technologies range from tumble agglomeration to extrusion and press agglomeration in the fields of mineral, renewable and biogenic resources as well as pharmaceutical, chemical and food industry. The article gives an overview on current trends as innovations in the area of measurement technology, merged processes and enhancement of existing apparatuses towards new areas of application.
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Particle design via spherical agglomeration is a size enlargement technique used in various bulk and fine chemical industries, with recent interest extending into pharmaceuticals, in which an immiscible bridging liquid is added to...
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Particle design via spherical agglomeration is a size enlargement technique used in various bulk and fine chemical industries, with recent interest extending into pharmaceuticals, in which an immiscible bridging liquid is added to agglomerate crystals prior to deliquoring. Spherical agglomeration has the potential to dramatically simplify downstream processing, and improves the handling of difficult, needle-shaped crystals. This review consolidates the understanding of the controlling process parameters, identifies the rate processes that control agglomerate attributes, and examines the modelling approaches taken in the literature to optimise the design of such systems. The most important controlling parameters are solvent system composition (requiring knowledge of the ternary phase diagram) and bridging liquid to solid ratio (BSR). Agglomerate size is a highly non-linear function of BSR with many literature systems showing qualitatively similar behaviour. However, there is no method to predict the optimum BSR. Other important process parameters are temperature, constituent particle properties, agitation rate and batch/residence time. Each parameter can have significant effects on the final agglomerate properties including agglomerate size, porosity, strength and dissolution profile.
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In fluid coking, agglomeration is undesirable because it causes heat and mass transfer limitations which increase reactor fouling and increase coke formation. Fluid coking efficiency is reduced because valuable product yields decr...
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In fluid coking, agglomeration is undesirable because it causes heat and mass transfer limitations which increase reactor fouling and increase coke formation. Fluid coking efficiency is reduced because valuable product yields decrease. Agglomeration is desirable in some industries where it is used to reduce dust problems and stabilize mixtures of various particulate components. This technology is used for the commercial production of pharmaceuticals, detergents, specialty chemicals, fertilizers and food. In both cases, it is important to know whether agglomerates and granules that form during fluidization fragment or remain intact and whether they increase or decrease in size. The objective of this study was to determine methods to predict agglomerate behavior during fluidization. Breakage behavior was predicted using the Stokes deformation number, fluidized bed shear rate, and agglomerate strength. After the properties of the breakage product were estimated, the growth/reduction behavior was estimated using two approaches: polynomial approximation and non-dimensionalization. The predictions were compared with experimental data obtained from previous studies conducted in the absence of reaction. The experimental results were predicted fairly well and the correlations can be used as a predictive tool for agglomerate behavior.
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Fluidized bed agglomeration is used to reduce dust problems and stabilize mixtures of various particulate components. Agglomeration in fluid coking, however, can create heat and mass transfer limitations which increase reactor fou...
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Fluidized bed agglomeration is used to reduce dust problems and stabilize mixtures of various particulate components. Agglomeration in fluid coking, however, can create heat and mass transfer limitations which increase reactor fouling and decrease process efficiency. The objective of this study was to investigate agglomerate survival in fluidized beds in the absence of reaction using materials that have similar properties to those used in the industrial fluid coking process. Agglomerates consisting of fluid coke and oils were made artificially outside of the fluidized bed, fluidized, and then recovered to determine whether agglomerate breakage, erosion, or growth occurred. This study investigated the effects of agglomerate liquid content, liquid binder viscosity, and fluidizing gas velocity on agglomerate stability. It was found that the onset of complete fragmentation occurred at 0.25 m/s (U/U_(mf) = 26) when the liquid binder viscosity was 6.44 cP and 0.34 m/s (U/ U_(mf)=35) when it was 64.7 cP. During fragmentation, more agglomerate material was recovered from the fluidized bed when the initial agglomerate diameter was 0.007 m compared with larger agglomerates (initial diameters of 0.012 m and 0.0167 m). This was due to the effects of secondary erosion on the fragmentation product.
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The viscosity and elasticity of particles influence their agglomeration behaviour. Such mechanical particle properties are determined by the supra-molecular and microscopic structure of the particles and process conditions such as...
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The viscosity and elasticity of particles influence their agglomeration behaviour. Such mechanical particle properties are determined by the supra-molecular and microscopic structure of the particles and process conditions such as temperature, humidity and strain rate or frequency. Most food powders are composed of amorphous water soluble substances. Accordingly spray dried dextrose syrup is used as a model substance for the current study. Such amorphous water-soluble substances show visco-elastic behaviour and depending on strain rate, temperature and moisture content, either the viscous or the elastic properties dominate their material behaviour. The viscous behaviour of a material can be characterised through its shear or its complex viscosity. The materials viscosity affects all types of agglomeration processes. The complex viscosity can be measured by Dynamic Mechanical Thermal Analysis (DMTA) while the shear viscosity is typically determined using a rotational viscometer. Alternatively it is possible to estimate the viscosity based on the difference between glass transition and process temperature. In the current study the glass transition temperature of spray dried dextrose syrup (DE21) is measured for different moisture contents and the obtained data are used for estimating the viscosity. In addition, the viscosity of the dextrose syrup powder at different temperature/moisture/frequency combinations is determined for higher viscosities by DMTA or measured for the lower viscosity range using a rotational viscometer. The obtained data are used to predict growth and pressure agglomeration processes such as fluid bed agglomeration and tabletting.
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This paper deals with assessing the impact of oak sawdust fuel substitution on the quality of agglomerate. Agglomerate quality is determined by its chemical composition, and further by its physical and metallurgical properties. An...
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This paper deals with assessing the impact of oak sawdust fuel substitution on the quality of agglomerate. Agglomerate quality is determined by its chemical composition, and further by its physical and metallurgical properties. An important physical property of agglomerate is porosi ty. When replacing sintering fuel by biofuel an important parameter is the amount of volatile substances that influence the process of pore for mation in agglomerate. It was confirmed that the substitution by oak sawdust in the agglomeration fuel is only possible to a certain percentage.
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Fluidized bed agglomeration is used to stabilize particulate mixtures and reduce dust emissions. This technology is applied to a variety of production processes for the pharmaceutical, chemical, fertilizer and food industries. In ...
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Fluidized bed agglomeration is used to stabilize particulate mixtures and reduce dust emissions. This technology is applied to a variety of production processes for the pharmaceutical, chemical, fertilizer and food industries. In most of these applications, agglomerate stability is an essential criterion. Agglomerates and granules that do not conform to size and shape specifications may create problems in downstream processes, such as tableting, thus compromising process efficiency and product quality. When an agglomerate is formed in a fluidized bed, it can grow by incorporating other bed particles, split into smaller fragments, or be eroded by fluidized bed solids. The objective of the present study is to determine the critical agglomerate liquid content at which the rates of agglomerate growth and shrinkage are balanced when artificial agglomerates made from glass beads and water are introduced into a fluidized bed. This study examined the effects of agglomerate size, agglomerate density, liquid viscosity, binder concentration, and fluidizing gas velocity on the critical initial liquid content. This study found that small agglomerates and low density agglomerates displayed higher critical initial moisture contents. When the viscosity was increased by using sugar solutions, agglomerates were very stable and had very low critical initial moisture contents. The study also found that as the superficial gas velocity increased, the agglomerates started to fragment, rather than erode.
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Aluminum agglomeration and agglomerate sizes of NEPE propellants were studied by cinephotomicrography at pressures of 3 and 5 MPa. Accumulation, aggregation, and agglomeration of aluminum particles similar to that at pressures bel...
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Aluminum agglomeration and agglomerate sizes of NEPE propellants were studied by cinephotomicrography at pressures of 3 and 5 MPa. Accumulation, aggregation, and agglomeration of aluminum particles similar to that at pressures below 1 MPa were observed. Coalescence of two agglomerates on the burning surface is obtained for the first time. A decrease in the burning rate from 8 to 5 mms(-1) leads to about 20% increase in the agglomerate diameter. The pressure is found to have no direct influence on the agglomerate diameter when the burning rate is kept constant. The evolution of the agglomerate diameter according to the increase of the virgin aluminum size from 16 to 36 mm is convex in shape and reached its maximum at a particle diameter of 29 mm. Increasing the amount of RDX crystals added in the propellants causes a larger agglomerate diameter. The experimental mass average agglomerate diameters were compared with various agglomeration models. It is found that Hermsen and Salita empirical models have a higher accuracy for NEPE propellants rather than Becksted, Liu, or pocket models.
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The explosion of multinational activities in recent decades is rapidly transforming the global landscape of industrial production. But are the emerging clusters of multinational production the rule or the exception? What drives th...
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The explosion of multinational activities in recent decades is rapidly transforming the global landscape of industrial production. But are the emerging clusters of multinational production the rule or the exception? What drives the offshore agglomeration of multinational firms in comparison to the agglomeration of domestic firms? Using a unique worldwide plant-level dataset that reports detailed location, ownership, and operation information for plants in over 100 countries, we construct a spatially continuous index of agglomeration and analyze the different patterns underlying the global economic geography of multinational and non-multinational firms. We present new stylized facts that suggest that the offshore clusters of multinationals are not a simple reflection of domestic industrial clusters. Agglomeration economies including technology diffusion and capital-good market externality play a more important role in the offshore agglomeration of multinationals than the agglomeration of domestic firms. These findings remain robust when we explore the process of agglomeration.
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A population balance model is developed for the growth of pre-formed agglomerates in a fluidized bed with several agglomeration mechanisms considered. Primary agglomeration takes place when dry particles collide with the wet surfa...
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A population balance model is developed for the growth of pre-formed agglomerates in a fluidized bed with several agglomeration mechanisms considered. Primary agglomeration takes place when dry particles collide with the wet surface of the original agglomerate. Secondary agglomeration occurs either by wet particles colliding with the dry surface of agglomerates, or by liquid migration to the top layer of an agglomerate and subsequent collisions with dry particles. The properties of the liquid binder determine the dominant mechanism. The new agglomeration model for high-and low-viscosity liquid binders is implemented in ANSYS FLUENT commercial software. Model predictions agree reasonably well with available experimental results without altering the previously published parameters of the sub-models employed. It is found that the viscosity of the liquid binder and surface asperities play notable roles in the agglomeration. Surface asperities are especially important when asperity heights are of the same order as the thickness of the liquid film. (C) 2017 Published by Elsevier B.V.
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