Solid agglomerate

OB to C02 —9.1%, white monoclinic needles (from methanal), mp 145—46° (dec), bp (ignites at 246—48°), d 1.684g/cc insol in w, sol in acet, methanol and AcOH si sol in cold ale, sol in hot reduces Fehling s soln on warming May be prepd by stirring lactose with mixed nitric-sulfuric acids until the mass forms a solid agglomerate [lp lactose in 15p acid, consisting of 1 vol nitric (d 1.5) and 2 vols coned sulfuric]. The mixt is transferred to ice w and pulverized under w. The product may be purified by crystn from ale (Ref 1)... 

The liquid phase is added to the mix vessel before solids addition to minimize the formation of solid agglomerates. Various methods of adding the fine metal particles have been used varying from hand-scoop to elaborate hopper facilities. In many cases, these additions must be accomplished in an inert atmosphere to avoid deterioration of the resultant slurry. 

The most common example of dispersive mixing of particulate solid agglomerates is the dispersion and mixing of carbon black into a rubber compound. The dispersion of such a system is schematically represented in Fig. 3.22. However, the break up of particulate agglomerates is best explained using an ideal system of two small spherical particles that need to be separated and dispersed during a mixing process. 

Since the important parameters for developing the pilot operation were the stress (to disperse the solid agglomerates) and the viscous dissipation (to avoid overheating), we need to maintain r and the Brinkman number, Br, constant. If our scaling parameter is the diameter, we can say... 

The mechanisms of mixing of miscible and immiscible liquids and soft agglomerates are depicted in Fig. 7.5, and that of hard solid agglomerates in Fig. 7.6. In the former, elongational and shear stretching is the dominant mechanism, whereas, the latter is shear stress dominated. 

Fig. 7.6 Dispersive mixing of hard solid agglomerates and immiscible liquid droplets that, after breakup, are distributed throughout the volume.

The dispersion of carbon black into rubber is the classic example of dispersion of solid agglomerates. The mechanical and physical properties of the rubber (e.g., in tires) depend... 

As a result of the mechanical action of mixing tools, turbulent or high intensity mixers do create fast moving, aerated, particulate matter systems. Therefore, interparticle collision and coalescence take place in a very similar fashion to that in suspended solids agglomerators. The main difference between the two methods is that in mixers particle movement is caused by mechanical forces while in suspended solids agglomerators drag forces induced by a flow of gas are the principal reason for movement of the bed of particulate matter, coalescence of particles, and agglomeration. 

Although suspended solids agglomerators lend themselves easily to continuous granulation, many systems are designed for batch operation. In most... 

Batch suspended solids agglomerators While a large number of different industrial applications has been developed during the past two or three decades, batch operations has found the widest use in pharmaceutical processing (see... 

Batch suspended solids agglomerators allow accurate adjustment of residual moisture, even if the drying rate drops drastically at low liquid content, and result in better control of overall product quality. Therefore, outside pharmaceutical applications, their main use is for baby formulae, special food products such as powdered cocoa, tea and coffee, fruit juice extracts, egg and milk powder, etc., for detergents as well as other cleaning reagents and chemicals. 

Continuous suspended solids agglomerators Development of continuous fluidized bed granulators was triggered by the desire to increase the capacity per unit while maintaining product quality. From a process point of view the advantage of continuous operation is that stationary and optimized conditions do prevail. 

Table 15 is a partial list of materials processed in the Anhydro fluid bed agglomerator. It stands as an example for all suspended solids agglomerators. 

The major growth mechanisms in suspended solids agglomerators are layering and coalescence after collision of wetted particles with each other or of particulate solids with binder droplets. At the same time drying or cooling takes place to activate the permanent binding mechanism (solid bridges). Intensive contact of... 

The fust documented development of fertilizer granulation in suspended solids agglomerators was in the early 1960s using the spouted bed technique, and in 1970 Fisons Fertilizer Ltd, UK, introduced prilling , the granulation of fertilizers from a melt by solidification of droplets in a vertical cooling chamber. 

On the other hand, micro-turbulence is particularly crucial in processes, which proceed in multiple phase systems (Dispersion in /L systems, shear stressing of solid agglomerates, etc.). In such cases the eddy must be of the same order of magnitude as the dispersed phase. 

Products With Controlled High Reactivity High reactivity of particulate solids is connected with large specific surface area and, respectively, small primary particle size. Because reactions take place on the surface of solids, agglomerated products with high reactivity must feature voids which are interconnected with a continuous network of pores that is accessible from the outside. In this respect, their structure is similar to those that are easily wettable. The main difference is, that, in most cases, the chemicals reacting with the solid are gases. The most common reactions are oxidation and reduction. 

For all those separation cases, however, which attempt to separate a particle collective according to certain properties of the particulate solids, agglomeration is most often undesired. Techniques for which this statement is true include screening, sifting, classification, sorting, flotation, and, as a general analytical method, particle size characterization. It should also be realized that the respective separation property is not only size it could be density, shape, color, chemical composition, and others. 

When mixing dry or moist bulk solids, agglomerates may form which originate from the finest components of the mixture. They are held together by molecular and electrostatic as well as capillary forces. These undesired agglomerates should be broken up by shear or frictional stresses, generated by the motion of the bulk mass, or by special disintegration devices that are built into the blender (see Section 7.4.2). 

II. Apparatus producing movement while keeping solid particulate matter suspended or loosely dispersed in a suitable fluid - suspended solids agglomeration (Sections 7.4.4 and 7.4.5). 

Utilization of the inclined-pan granulator in the fertilizer industry was first reported in Germany in 195 3 for the granulation of ordinary superphosphate and the first documented application of suspended-solids agglomerators was in the early 1960s using a spouted bed [B.48]. 

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