Agglomerated hollow particles

Figure 8 - a) Bulk density at different end-pressures, b) Exp. nr. 5, agglomerated hollow particles... 

In the discussion of the results a distinction is made, with help of the scanning electron microscopy (SEM), between spheres (solid or hollow), distorted and sponge-like 6) particles. All the other morphologies are defined by the combination of these three basic shapes e.g. distorted agglomerated hollow spheres. The three shapes are shown in Figure 7. 

Figure 12 shows possible mechanisms of particle formation during PGSS operation. Under the influence of CO2 concentration, melt temperature, atomization pressure and feed rate, these mechanisms predict the formation of completely solid spherical particles, a hollow spherical particles, agglomerated distorted particles or sponge like particles. 

Spherical CaHAP panicles are synthesized by spray pyrolysis. The spherical particles are suitable for high-performance liquid chromatography (HPLC) adsorbents. The atomized solutions dissolving Ca(N03)2 and (NH4)2HP04 are evaporated into the hot part of a furnace, to be decomposed at 600°C (13). The CaHAP particles formed are hollow agglomerates of tine particles. 

Particle shape Hollow agglomerates Inhomogeneities Non-uniform grain... 

Other recent work (Hess and Herd, 1993) on the microstructure of carbon blac] confirmed earlier findings (Medalia and Rivin, 1976) that the particles of some pa graphitized blacks are composed of hollow graphitic shells. Thus, voids are fom the interior of the particles and agglomerates as a result of localized densificatioi... 

Therefore, while during the spray drying of solutions and emulsions, mostly hollow spherical particles are produced by a process which is not directly defined as agglomeration, the production of dry particles from suspensions and slurries uses the binding mechanisms of agglomeration to yield true agglomerates. 

In Table 5 the effect of the melt temperature on the particle morphology is shown. In all experiments hollow spheres were formed. At 60-65 C melt temperature distorted particles were formed. At 80 C and 140 bar atomization pressure agglomeration occurred. Whereby at 80 C and 70 bar atomization pressure. Figure 10, hollow and spherical particles are formed. 

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