Agglomeration of particles

Solid-Liquid Mass Transfer There is potentially a major effect of both shear rate and circulation time in these processes. The sohds can either be fragile or rugged. We are looking at the slip velocity of the particle and also whether we can break up agglomerates of particles which may enhance the mass transfer. When the particles become small enough, they tend to follow the flow pattern, so the slip velocity necessary to affect the mass transfer becomes less and less available. 

Diffusion filtration is another contributor to the process of sand filtration. Diffusion in this case is that of Brownian motion obtained by thermal agitation forces. This compliments the mechanism in sand filtration. Diffusion increases the contact probability between the particles themselves as well as between the latter and the filter mass. This effect occurs both in water in motion and in stagnant water, and is quite important in the mechanisms of agglomeration of particles (e.g., flocculation). 

Chemical engineers could also work to devise processes to improve the flow characteristics of powders after they are formed. Such research would help control agglomeration of particles in subsequent processing steps as well as facilitate the production of compacted ceramic preforms. For example, gas-solid chemical reactions might be used to tailor the chemical composition of powders. As another example, better methods of componnding powders with binders might be achieved by processes that mix powders with suitable binders in a liquid and then spray dry the resulting suspension. 

Consider a conductive solution consisting of water with a soluble salt, i.e.-1% NaCl, and a dispersing agent used to prevent agglomeration of particles in suspension. Two electrodes are placed in solution with a non-conducting orifice between them, as shown in 5.10.14, given on the next page ... 

When colloids are involved in catalysis, the separation of catalyst by means of solvent evaporation becomes inappropriate because the agglomeration of particles is then favoured [3]. Soft methods like filtration or centrifugation turn out to be more convenient. 

The polymer/additive system in combination with the proposed extraction technique determines the preferred solvent. In ASE the solvent must swell but not dissolve the polymer, whereas MAE requires a high dielectric solvent or solvent component. This makes solvent selection for MAE more problematical than for ASE . Therefore, MAE may be the preferred method for a plant laboratory analysing large numbers of similar samples (e.g. nonpolar or polar additives in polyolefins [210]). At variance to ASE , in MAE dissolution of the polymer will not block any transfer lines. Complete dissolution of the sample leads to rapid extractions, the polymer precipitating when the solvent cools. However, partial dissolution and softening of the polymer will result in agglomeration of particles and a reduction in extraction rate. 

Shapes and sizes of agglomerates of particles for example, pellets, granules, and extrudates. 

There are essentially two types of processes that can cause agglomeration of particles when they are suspended in a fluid ... 

Over the centuries, many other concepts were proposed to explain the nature of matter— many of them extensions of the Greek concept of an ultimately indivisible and indestructible elementary bit of matter. But it was not until J. J. Thomson proposed his model of the atom, consisting of a sphere with an agglomeration of particles with negative electric charges somehow positioned randomly inside a very small ball of matter, that the modern structure of the atom began to take shape. 

Evolution of the longitudinal NMRD profile during the agglomeration of particles coated by a polyelectrolyte. 

Fig. 6. Particle size distribution curve with an additional peak due to large agglomerates of particles.

Additional amounts of the suspended agent solution should only be used to counteract agglomeration of particles that may occasionally occur. 

Agglomeration of particles by stochastic movement on the soot particles... 

Vacuum and pressure laboratory filtration assemblies are shown in Figure 11.7. Mild agitation with air sometimes may be preferable to the mechanical stirrer shown, but it is important that any agglomerates of particles be kept merely in suspension and not broken up. The test record sheet of Figure 11.8 shows the kind of data that normally are of interest. Besides measurements of filtrate and cake amounts as functions of time and pressure, it is desirable... 

DISPERSANTS. Dispersants are materials that help maintain fine solid particles in a state of suspension, and inhibit their agglomeration or settling in a fluid medium. With the help of mechanical agitation, dispersants can also hit-.tk up agglomerates of particles to form particle suspensions. Another use of dispersants is to inhibit the growth of crystallites in a supersaturated solution. This characteristic is also known us precipitation... 

The destabilization of repulsive electrical charges to permit some agglomeration of particles. 

Organic matter deposited onto the suspended sediment has a large influence on the specific surface area. On one hand, it appears that organic matter blocks some sites available for physical adsorption of inert gas (BET adsorption) and, on the other hand, it probably partly causes flocculation and agglomeration of particles in the upper estuary, such floes and agregates being destroyed downstream in the salinity intrusion zone. 

Twin-screw extruders or high-speed stirrers may be used to obtain good dispersions in the thermoset precursors. The main drawback is the possibility of producing agglomerates of particles during storage or processing. 

Solubilization of insoluble oxidation products and soot particles. Reverse micelles (RMs) formations manage the prevention of agglomeration and the contamination process of insoluble oxidation particles and soot particles by both steric stabilization (Fig.2.1) and electrostatic stabilization mechanisms (Fig.2.2). The steric stabilization mechanism provides a physical barrier to agglomeration of particles by adsorption on particle surfaces. Adsorbed dispersant acts as a physical barrier to attraction between particles. 

Additive interactions take place in lubricating oil formulation and at surfaces (Kajdas, 2001 Spikes, 1989). At surfaces, additive interactions should protect metallic engine surfaces from corrosion, prevent rusting, build-up of varnishes, agglomeration of particles, and form low friction and protective films. In the base... 

Another class of applications is the high shear mixers used to break up agglomerates of particles as well as to cause rapid dissolving of solids into solvents. A further type includes the catalytic processes such as hydrogenation, in which there is a basic gas-liquid mass transfer to be satisfied, but in addition, effective mixing and shear rate on the catalyst particle fluid film as well as degradation must be considered. 

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