Agglomerated particles

Agglomeration. The process of treating dried products, particularly nonfat products, ia order to iacrease speed and abHity to reconstitute those products, is known as instantizing or agglomeration. Particles are agglomerated iato larger particles which dissolve more easHy than smaH particles. In... 

As the particles in a coUoidal dispersion diffuse, they coUide with one another. In the simplest case, every coUision between two particles results in the formation of one agglomerated particle,ie, there is no energy barrier to agglomeration. Applying Smoluchowski s theory to this system, the half-life, ie, the time for the number of particles to become halved, is expressed as foUows, where Tj is the viscosity of the medium, k Boltzmann s constant T temperature and A/q is the initial number of particles. 

For many applications, the main need is for agglomerated particles having an open particulate array which rapidly dissolves (as in some pharmaceuticals), while in others a more dense structure is required giving a slow release of its components (as in fertilizers). 

It is often observed that crystals do not exist as discrete entities but, especially when viewed under the optical microscope, appear to comprise agglomerated particles. Even a cursory glance at the literature quickly shows that the subject of agglomeration spans several disciplines including crystallography, materials... 

Both aggregation inefficiency (Adler, 1981) and particle disruption (Hartel and Randolph, 1986) increase with particle size. These dispersive processes can counteract the positive effect of aggregation thereby imposing agglomerate particle size limitations and may give rise to apparent size-independence. 

In a study of crystal precipitation of calcium carbonate during the batch carbon-ation of lime water, individual crystals and agglomerated particles were observed as shown in Figure 8.18(a), (b) and (c), respectively (Wachi and Jones, 1991b). 

Disruption of an agglomerated particle L, S), produces a single primary crystal (Ld, 1) and the residual particle (Ldd, —1). Conservation of crystal mass balance requires the following equations to be satisfied ... 

The equilibrium particle diameter in the case of non agglomerate particle systems or the enzyme activity of immobilised enzymes after a certain exposure of time is entirely due to the reactor-specific comminution process, and conclusions can therefore be drawn regarding the maximum intensity of hydrodynamic stress. 

Transmission electron microscopy for [Pd/l]coii reveals the presence of small spherical but in some cases agglomerated particles of ca. 4 nm mean size, and wide angle X-ray scattering analyses evidence the fee structure of bulk palladium [44] (Figure 1). 

Venturi and orifice scrubbers are simple forms of wet scrubbers. The turbulence created by the venturi or orifice is used to atomise water sprays and promote contact between the liquid droplets and dust particles. The agglomerated particles of dust and liquid are then collected in a centrifugal separator, usually a cyclone. 

Pharmaceutical scientists have developed improved suspension dosage forms to overcome problems of poor physical stability and patient-perceived discomfort attributed to some active ingredients. An important development aspect of any suspension is the ability to resuspend easily any settled particles prior to instillation in the eye and ensure that a uniform dose is delivered. It would be ideal to formulate a suspension that does not settle since the patient may not always follow the labeled instructions to shake well before using. However, this is usually not feasible or desirable since the viscosity required to retard settling of the insoluble particles completely would likely be excessive for a liquid eyedrop. The opposite extreme, of allowing complete settling between doses, usually leads to a dense layer of agglomerated particles that are difficult to resuspend. 

As reported in the literature by Heard et al. [156], the colour of the gold sol depended strongly on the size of the particles. The blue sol corresponded to 20-30 nm elongated agglomerated particles whereas pink sols corresponded to <20 nm particle size. 

The use of fluidized beds to coat and agglomerate particles dates back over forty (40) years. Currently, fluidized beds are used to coat a variety of particles in the size range of 50 pm - 1 cm, with a variety of functional and... 

Compo, P., Pfeffer, R., and Tardos, G. I., Minimum Sintering Temperatures and Defluidization Characteristics of Agglomerating Particles, Powder Technology, 51(1) 87-103 (1987)... 

F. Large sphere of ferromagnetic material (strongly agglomerated particles)... 

E Large Sphere of Ferromagnetic Material (Strongly Agglomerated Particles)... 

Alternative methods of assisting the fluidization of difficult materials include the use of impellers in the bed to break up agglomerated particles, particularly to help initial fluidization in plug flow driers (Reay and Baker, 1985), and the use of a pulsed gas flow (Butcher, 1988). Bahu... 

---