TANDEM MIXER

The mechanism of the catalysis of ascorbate autoxidation by 6-OHDA, 6-ADA, DA, and other related compounds was studied in great detail (6) in double-mixer flow experiments coupled with ESR. These studies showed that the free radicals (QH ) generated by oxidation of the catalyst, for example, 6-OHDA in mixer No. 1 could be converted quantitatively to the ascorbate radical in the tandem mixer No. 2 by addition of excess ascorbate. A simplified version of this mechanism [see Ref. 6 for details] in neutral or alkaline solutions is ... 

FIG. 14.12 (a) Greerco A" two-stage sanitary tandem shear pipeline mixer, (b) Exploded... 

Chemineer Greerco offers a different rotor-stator geometry. In this case, as shown in Figure S-4a and b, the rotor is an axial impeller that pushes the fluid axially through holes bored into the stator. The rotating action of the impeller, however, creates some tangential shear flow inside the stator. There is a two-stage version called the tandem shear pipeline mixer. This consists of a primary disperser... 

Tandem seals are another seal arrangement for multiple seals. Tandem seals stack two or more seals together to handle portions of a high operating pressure. Much less common than double seals for mixer applications, tandem seals may be used with double seals to handle very high pressures. 

Choice of a mixer depends upon technical as well as economic requirements. Roll-mill is more labour intensive and often used for research and development. However, in many production lines the mixing is started in an internal mixer and finished in a roll-mill as the two types of mixers are installed in tandem. 

---