Agglomeration particles properties

The model is able to predict the influence of mixing on particle properties and kinetic rates on different scales for a continuously operated reactor and a semibatch reactor with different types of impellers and under a wide range of operational conditions. From laboratory-scale experiments, the precipitation kinetics for nucleation, growth, agglomeration and disruption have to be determined (Zauner and Jones, 2000a). The fluid dynamic parameters, i.e. the local specific energy dissipation around the feed point, can be obtained either from CFD or from FDA measurements. In the compartmental SFM, the population balance is solved and the particle properties of the final product are predicted. As the model contains only physical and no phenomenological parameters, it can be used for scale-up. 

After an iPP particle reached the FBR, co-polymerization of ethylene-propylene starts preferrably inside the porous PP matrix. Depending on the individual residence time, the particle will be filled with a certain amount of ethylene-propylene rubber, EPR, that improves the impact properties of the HIPP. It is important to keep the sticky EPR inside the preformed iPP matrix to avoid particle agglomeration that could lead to wall sheeting and termination of the reactor operation. Ideally a "two phase" structure, see Fig.5.4-3, is produced. Finally, a "super-high impact" PP results that contains up to 70% EPR. How much EPR is formed per particle depends on three factors catalyst activity in the FBR, individual particle porosity, and individual particle residence time in the FBR. All particle properties are therefore influenced by the residence time distribution, and finally, a mix of particles with different relative amounts of EPR is produced - a so called "chemical distribution" see, for example, [6]. 

The presence of amorphous lactose in the excipient may have a negative effect on compactibility and product stability. Direct compression grades of lactose monohydrate are available as granulated/agglomerated particles from multiple vendors. These physical properties are listed in Table 7.4. Commercial products combine the good flowability of coarse lactose crystals and the good compressibility... 

Continuons emulsion polymerization is one of the few chemical processes in which major design considerations require the use of dynamic or unsteady-state models of the process. This need arises because of important problems associated with sustained oscillations or limit cycles in conversion, particle number and size, and molecular weight. These oscillations can occur in almost all commercial continuous emulsion polymerization processes such as styrene (Brooks et cl., 1978), styrene-butadiene and vinyl acetate (Greene et cl., 1976 Kiparissides et cl., 1980a), methyl methacrylate, and chloropene. In addition to the undesirable variations in the polymer and particle properties that will occur, these oscillations can lead to emulsifier concentrations too low to cover adequately the polymer particles, with the result that excessive agglomeration and fouling can occur. Furthermore, excursions to high conversions in polymer like vinyl acetate... 

FIGURE 10.12 Nitrogen adsorption isotherms and corresponding pore size distributions of a typical FSP-derived powder and the commercial reference catalyst E4759. Note that the particles of the flame-made catalyst are virtually nonporous. The indicated macropores originate from interstitial voids of the agglomerated particles. (From Strobel, R., Stark, W.J., Madler, L., Pratsinis, S.E., and Baiker, A., Flame-made platinum/alumma structural properties and catalytic behaviour in enantioselective hydrogenation, J. Catal., 213, 296, 2003.)... 

Kawashima, Y. Matsuda, K. Takenaka, H. Physicochemical properties of spray-dried agglomerated particles of salicylic acid and sodium salicylate. J. Pharm. Pharmacol. 1972, 24, 505-512. 

In the case of fumed powders, the results of particle size analysis depend veiy strongly on the characterization method. Each method measures a different particle property, from which sphere equivalent diameters are calculated. The underlying models assume homogeneous, spherical particles, which does not apply to the porous aggregates and agglomerates of these materials. 

As will be shown in Sections 5.2 and 5.3, particle size of the particulate solids plays an important role in agglomeration. While the surface area of particles, the interface at which all binding mechanisms act, decreases with the second power of particle size, volume and, therefore also, mass, the most important particle properties which result in forces that challenge adhesion and cause separation of bonds, diminish with the third power of the particle size. If the particle size reaches a few pm or is in the nm range, the natural adhesion forces dominate and particles which contact each other or come into close proximity adhere to one another. This phenomenon can not be economically eliminated so that very fine particles always adhere and form loose agglomerates which may be desirable or undesirable (see Section 5.5). 

From the experimental results in series 1, it was found that the particle properties of magnesium hydroxide depend on the type of alkali feed. To change the dominant particle sizes of primary and agglomerated particles, it may be effective to use the mixture of alkali feeds. In series 2, calcium hydroxide and sodium hydroxide were used as two kinds of alkali feed. Experimental conditions of series 2 are listed in Table n, where R means the mole fraction of sodium hydroxide in the mixture of calcium hydroxide and sodium hydroxide, that is, [OH... 

Table IV shows the solubilities of various alkali feeds. In general, smaller solubility means that the movement of OH is controlled by ion pair of solute. So it may be difficult for Mg to collide with OH in calcium hydroxide which has the smallest solubility. From SEM photographs of magnesium hydroxide in Figure 3, primary particles are formed in the system of calcium hydroxide, whereas larger primary particles are formed and agglomerated easily in other alkali feed systems which have larger solubility. Then dominant particle size of agglomerated particle becomes larger. Therefore, the solubility may be the key property among the above-mentioned properties. This tendency was also observed in the reactive crystallizations of other carbonates, that is, calcium carbonate(9) and lithium carbonate(lO).

Alkali feed influences the properties of magnesium hydroxide particles. In the system of calcium hydroxide primary particles are formed easily and the kinetic order i is less than 1. But, in other cases, that is, barium hydroxide, potassium hydroxide and sodium hydroide as alkali feeds, agglomerated particles are formed easily and kinetic order i is greater than 1. 

Less exfoliation and more agglomerated particles were observed when the ammonium cation contained a polar group V with properties resembling those of microcomposites. 

The fluidized bed process offers wide flexibility to adjust the particle properties according to the requirements. So it is possible to generate only slightly agglomerated granules with excellent dissolution properties, but also very spherical particles with an even particle surface and low risk of... 

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