Stirred columns

To this author s knowledge, no data on three-phase stirred columns are available. Preliminary observations indicate that the axial dispersion in the gas phase is considerably reduced by the presence of solid particles. Under certain conditions, even for a very low L/dc (where L is the length and dc the diameter of the stirred column) the gas phase may move essentially in plug flow. 

P. Todtenhaupt [547] investigated the homogenization characteristic of a stirred column with 5 stirrers on the same shaft and flow from bottom to the top. Turbine, cross-beam, MIG and propeller stirrers were used. The stirred column was provided with round baffles, but did not possess partition trays between the individual stirred sections. Turbine stirrers performed the best and propeller stirrers conveying downwards the worst. For these two stirrer types the following process relationships apply ... 

If the stirrer were only to mix radially and no axial back-mixing were to be caused, the exponent of Rcq would approach unity r = V/q cc LhD /q- Then Lh must be ccq. This situation is realized better with turbine stirrers than with propeller stirrers. If this assumption is the starting point for the scale-up of stirred columns, it follows from... 

Rautenbach and Machhamer [91] developed a correlation for prediction of drop sizes of emulsion globules in stirred column contactors as... 

Provision of a shaft through the extraction column allows for repeated redispersion of the drops via various impellers located along the shaft. A variety of industrial equipment is available, with the differences being in the design of the impellers on the shaft for dispersion, and stators in the column for baffling and coalescence. Stirred columns offer the operator increased flexibility in operation by independent control over the dispersion process. 

Other variations of stirred columns which are available include the asymmetric rotating disc (ARD) contactor, the Kuhni column, and two types of Scheibel columns. The rotor of the ARD is located off center, which permits more elaborate baffling for the necessary transport of flows with less backmixing. 

Apparatus A 100-mL round-bottom fiask, a 50-mL Erlenmeyer flask. Claisen adapter, gas trap, separatory funnei, separatory funnel with standard-taper glass joint, ice-water bath, reflux condenser, apparatus for magnetic stirring, column chromatography, simple distillation, and ffame/ess heating. 

Disconnect the column, and remove the flask from the oil-bath. Add 25 ml. of dilute hydrochloric acid to the flask, shake the contents vigorously, and chill in ice-water, when crystals of benzhydrol will separate. (Occasionally the hydrol will separate initially as an oil, which ciystallises on vigorous stirring.)... 

Tricarballylic acid. Place 228 g. (204 ml.) of ethyl propane-1 1 2 3-tetracarboxylate and 240 ml. of 1 1 hydrochloric acid in a 1-litre threenecked flask, fitted with a mechanical stirrer and a fractionating column with condenser set for downward distillation attach a receiver with side tube to the condenser and connect the side tube to a wash bottle containing water. Boil the mixture, with continual stirring, at such a rate that the... 

Cholestenone. Place a mixture of 1 0 g. of purified cholesterol and 0-2 g. of cupric oxide in a test-tube clamped securely at the top, add a fragment of Dry Ice in order to displace the air by carbon dioxide, and insert a plug of cotton wool in the mouth of the tube. Heat in a metal bath at 300-315° for 15 minutes and allow to cool rotate the test-tube occasionally in order to spread the melt on the sides. Warm with a few ml. of benzene and pour the black suspension directly into the top of a previously prepared chromatographic column (1) rinse the test-tube with a little more benzene and pour the rinsings into the column. With the aid of shght suction (> 3-4 cm. of mercury), draw the solution into the alumina column stir the top 0 -5 cm. or so with a stout copper wire to... 

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