Es wird eine Ubersicht gegeben uber den Einsatz von Riihrkessel-Reaktoren und Kessel-Kaskaden bei technischen Substanz-, Losungs-, Fallungs-, Perl-und Emulsionspolymerisationen. Besonders eingegangen wird auf die vielfaltige Gestaltung der Ruhrorgane und der Kuhlvorrichtungen. Die unterschiedlichen prozefitechnischen Aufgaben des Ruhrwerks (Homogenisieren, Suspendieren, Dispergieren, Warmeubergang) und die daraus resultierende Scale-up-Problematik werden dargestellt und die diversen Arten der indirekten Kiihlung (Mantelkuhlung, Innenkuhler, AuDenkuhler) und der Siedekuhlung vergleichend bewertet. SchlieDlich werden sicherheitstechnische Maonahmen beim Betrieb von Polymerisationskesseln erlautert.Stirred tank reactors for polymerization. A general survey on stirred tank reactors and cascades of stirred tanks in industrial polymerization (bulk, solution, precipitation, grain and emulsion polymerization) is presented. Special consideration is given to the various designs of both agitator and cooling devices. Scale-up problems arising from the multitude of process functions (homogenisation, suspension, dispersion, promotion of heat transfer) carried out in a stirred vessel are explained and the divers methods of indirect cooling (jacketed tank, internal coil, external heat exchanger) as compared to evaporative cooling are assessed. Finally, safety measures in operating polymerization vessels are discussed. * Dr. H . Hachenberg, Hoechst Aktiengesellschaft, Postfach 800 320, 6230 Frankfurt/M. 80.
Two insecticides, carbaryl and chlorpyrifos, were evaluated at low concentrations as tracers to predict the behaviour of spray clouds of malathion at field strength. Aerial sprays were produced from a Cessna Ag Husky equipped with a dual liquid dispersal system, spraying simultaneously. Spray drift was measured at 90 or 30 m downwind using 1.6 mm polyester cord and 0.6 mm monofilament line suspended from a helium-filled blimp tethered 15.25 m above ground level.Recoveries of malathion averaged 87.3% and 85.2% of the amount predicted from the tracers on the monofilament and polyester, respectively. The coefficients of variation for 12 flights were 50.9% for the monofilament line, and 17.4% for the polyester cord.
During the development of the downflow bubble columni knowledge of the specific interfacial area was a precondition for assessing the mass transfer performance.A comparison with other gas/liquid contactors shows that, in the downflow bubble column, higher mass transfer areas can be obtained than, for example, in a bottom-sparged bubble column or in a loop-type reactor in the region of high liquid throughputs. Examples for practical performance of downflow bubble columns are given, based on the derived correlations.
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