Agglomeration study

Sedimentation analysis is suitable for a wide variety of materials and is used for both quaHty control and research work, such as agglomeration studies (56), and gives well-defined, relatively high resolution results. The technique has been employed in the evaluation of soils, sediments, pigments, fillers, phosphors, clays (qv), minerals, photographic haHdes, and organic particles (57,58). 

Ramos, M.J., et al., 2008. Transesterification of sunflower oil over zeolites using different metal loading a case of leaching and agglomeration studies. Applied Catalysis A General 346 (1—2), 79—85. Available at http //www.sciencediiect.com/science/article/pii/... 

Several laboratory tests (3,6) are used to determine the desirabiHty of a coal or blend of coals for making coke. These are empirical and are carried out under conditions that approach the coking process. The three properties that have been studied are swelling, plasticity, and agglomeration. 

If the sample is an insulator there are still methods by which it can be studied in the instrument. The simplest approach is to coat it with a thin (10-nm) conducting film of carbon, gold, or some other metal. In following this approach, care must be taken to avoid artifacts and distortions that could be produced by nonuniform coatings or by agglomeration of the coating material. If an X-ray analysis is to be... 

Davey and Rutti (1976) studied the effeet of polyerystals growth on agglomeration of hexamethylene tetramine (HMT). Regular six member elusters were... 

For stirrer speeds of 4.2, 8.4, 16.7, 25 and 33.4Fiz, agglomeration kernels obtained in this study vary from 0.01 to 183 s . Unfortunately, no other measured data for agglomeration of calcium oxalate analysed using Smoluchowski s kernel were found in the literature. The corresponding values reported by Wojcik and Jones (1997) for calcium carbonate, however, cover a range from 0.4 to 16.8s-. ... 

It is plain from the above review of the literature that agglomeration ean be a very eomplieated phenomenon in whieh eontrary behaviour is often observed, and despite mueh work the theoretieal basis is yet to be fully developed, partieular problems tending to require speeifie solutions. Nevertheless, faeed with a given problem there is some guidanee that ean be offered for systematie study, caveat emptor. 

In all such laboratory studies, plant conditions and compositions should be employed as far as possible. Agglomeration rates tend to increase with the level of supersaturation, suspension density and particle size (each of which will, of course, be related but the effects may exhibit maxima). Thus, agglomeration may often be reduced by operation at low levels of supersaturation e.g. by controlled operation of a batch crystallization or precipitation, and the prudent use of seeding. Agglomeration is generally more predominant in precipitation in which supersaturation levels are often very high rather than in crystallization in which the supersaturation levels are comparatively low. 

Several reported chemical systems of gas-liquid precipitation are first reviewed from the viewpoints of both experimental study and industrial application. The characteristic feature of gas-liquid mass transfer in terms of its effects on the crystallization process is then discussed theoretically together with a summary of experimental results. The secondary processes of particle agglomeration and disruption are then modelled and discussed in respect of the effect of reactor fluid dynamics. Finally, different types of gas-liquid contacting reactor and their respective design considerations are overviewed for application to controlled precipitate particle formation. 

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). 

In a polymeric matrix the filler, even if present in minimum quantities) is always more or less agglomerated [212]. Microscopic studies have confirmed the existence of two types of primary structures in composites [213], i.e., filler aggregates with particles bound together firmly enough, and agglomerates — systems of weakly interrelated aggregates. 

The instrument has been evaluated by Luster, Whitman, and Fauth (Ref 20). They selected atomized Al, AP and NGu as materials for study that would be representative of proplnt ingredients. They found that only 2000 particles could be counted in 2 hours, a time arbitrarily chosen as feasible for control work. This number is not considered sufficient, as 18,000 particles are required for a 95% confidence level. Statistical analysis of results obtained for AP was impossible because of discrepancies In the data resulting from crystal growth and particle agglomeration. The sample of NGu could not be handled by the instrument because it consisted of a mixt of needles and chunky particles. They concluded that for dimensionally stable materials such as Al or carborundum, excellent agreement was found with other methods such as the Micromerograph or visual microscopic count. But because of the properties peculiar to AP and NGu, the Flying Spot Particle Resolver was not believed suitable for process control of these materials... 

Particle Formation, Electron microscopy and optical microscopy are the diagnostic tools most often used to study particle formation and growth in precipitation polymerizations (7 8). However, in typical polymerizations of this type, the particle formation is normally completed in a few seconds or tens of seconds after the start of the reaction (9 ), and the physical processes which are involved are difficult to measure in a real time manner. As a result, the actual particle formation mechanism is open to a variety of interpretations and the results could fit more than one theoretical model. Barrett and Thomas (10) have presented an excellent review of the four physical processes involved in the particle formation oligomer growth in the diluent oligomer precipitation to form particle nuclei capture of oligomers by particle nuclei, and coalescence or agglomeration of primary particles. 

A LCA on treatment options of MPW was performed by the Dutch Centrum voor Energiebesparing en Schone Technologie (CE, Delft) in 1994. This LCA used the VEBA process as an example for feedstock recycling (a.ll). Another LCA was performed by Heyde and Kremer (a.6). Particularly the CE studies suggested that the VEBA process was a bit less advantageous than the Texaco process, mainly due to the fact that the Texaco process does not need agglomeration of MPW as pre-treatment, whereas the VEBA process apparently does. 

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