Roller atomization mechanisms

Roller atomization is a mechanical atomization process. It was invented in the mid 1970 sJ188] In this process, as schematically depicted in Fig. 2.22, a stream of molten metal is fed into the gap between two counter-rotating rolls and forms a thin liquid sheet that subsequently disintegrates into droplets by the mechanical forces. In the original design, a pair of rollers of 100 mm in diameter are mounted in the same horizontal plane and rotate at speeds up to 1250 radians/s. The roll gap is about 50-100 pm, and the metal flow rate is up to 6 kg/min. 

When two layers of the substance are displaced relative to one another, the nuclei of phase A, located between them, can be regarded as kind of a roller about which oscillations are executed. - - - when the two layers of phase AB are displaced relative to one another, they transport past the nucleus, in its immediate vicinity, a multiplicity of atoms of both kinds. - - - it follows that all the atoms A passing in the immediate vicinity of the nucieus have sufficient time to combine with the latter and this in fact may be the mechanism of the growth of the nuclei of the new phase. ... 

The Keefer-Roller nitrosation is not such as case, however, if one includes the mechanistic role of the catalyst, as shown in the sequence given in (4-9, R = H for formaldehyde). The aldehyde reacts first with the amine, forming an iminium ion. The Hard and Soft Acid and Base principle of Pearson (1963, 1968 Parr and Pearson, 1983 see also Zollinger, 1994, Sect. 3.2) predicts that the reaction of one of the O-atoms of the nitrite ion with the aldehyde C-atom of the iminium ion is the most likely reaction. In the last step, this addition product rearranges through an NN bonded four-membered ring transition state or intermediate into the nitrosoamine and the aldehyde. This mechanism is consistent with Casado s kinetic results. 

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