Reactor ball mill

The oxide exiting either the Barton or ball mill reactor is conveyed by an air stream to separating equipment, ie, settling tank, cyclone, and baghouse, after which it is stored in large hoppers or dmmmed for use in paste mixing. Purity of the lead feed stock is extremely critical because minute quantities of some impurities can either accelerate or slow the oxidation reaction markedly. Detailed discussions of the oxide-making process and product are contained in references 55—57. 

Beside continuous horizontal kilns, numerous other methods for dry pyrolysis of urea have been described, eg, use of stirred batch or continuous reactors, ribbon mixers, ball mills, etc (109), heated metal surfaces such as moving belts, screws, rotating dmms, etc (110), molten tin or its alloys (111), dielectric heating (112), and fluidized beds (with performed urea cyanurate) (113). AH of these modifications yield impure CA. 

There are other advantages of employing magnetic ball mills besides the control of mechanical milling modes. Since the centrifugal force becomes a secondary factor in milling, and the reactor shell rotates at low RPM, contamination from balls and shell wear is lower than in a vibrational or a planetary mill there is less ball wear involved and contaminations with Fe from steel become less of the problem. Also lower rotations and uniaxial movement of reactors paced on horizontal axle allow... 

Figure 17.10. Several modes of mixing in commercial tank reactors, (a) Steam-jacketed autoclave, 120 gal, 200psig, 300°F (courtesy Blaw-Knox Co.), (b) Horizontal autoclave, 650gal, lOOpsig (courtesy Blaw-Knox Co.), (c) Ball-mill sulfonator [Groggins. Courtesy McGraw-Hill, New York]. (d) Horizontal heat-exchange reactor (courtesy Stratford Engineering Corp. patents issued and pending).

Comment. The classical industrial process comprises cyclizing o-bcnzoylbenzoic acid (from reaction of phthalic anhydride with benzene) with acid using a solvent or a ball mill process. It is difficult to see how the Bram process could be made competitive. All solid support processes would seem to require pumping a solid slurry through a tubular microwave reactor. 

FIGURE 9.21 Kinetics of the ball milling process with rutile incorporated in the reactor. 

Mechanical activation was performed in a high energy (acceleration up to 70 g) planetary ball mill with stainless steel reactor and balls under an argon atmosphere during 1 h. All the sample handling has been operated in Ar-filled glow box (MBraun), in which the water/oxygen levels were below 1 ppm. 

Several reactors are presently used for studying gas-solid reactions. These reactors should, in principle, be useful for studying gas-liquid-solid catalytic reactions. The reactors are the ball-mill reactor (Fig. 5-10), a fluidized-bed reactor with an agitator (Fig. 5-11), a stirred reactor with catalyst impregnated on the reactor walls or placed in an annular basket (Fig. 5-12), a reactor with catalyst placed in a stationary cylindrical basket (Fig. 5-13), an internal recirculation reactor (Fig. 5-14), microreactors (Fig. 5-16), a single-pellet pulse reactor (Fig. 5-17), and a chromatographic-column pulse reactor (Fig. 5-18). The key features of these reactors are listed in Tables 5-3 through 5-9. The pertinent references for these reactors are listed at the end of the chapter. 

Another advantage of using no solvent (or less solvent), is that reaction times are often shorter, especially when a ball mill or microwave reactor is used. It is likely that solvent free methods will become more widespread as the number of microwave reactors and ball mills in research laboratories increases. For the green chemist, it is also worth noting that significant efforts need to be made in greening the work up of many of the reactions presented here and elsewhere. In most cases, any VOC solvent readily available is used, when a less hazardous or bio-sourced VOC would be a better option. 

---