Agitated

In this accident, the steam was isolated from the reactor containing the unfinished batch and the agitator was switched ofiF. The steam used to heat the reactor was the exhaust from a steam turbine at 190 C but which rose to about 300°C when the plant was shutdown. The reactor walls below the liquid level fell to the same temperature as the liquid, around 160°C. The reactor walls above the liquid level remained hotter because of the high-temperature steam at shutdown (but now isolated). Heat then passed by conduction and radiation from the walls to the top layer of the stagnant liquid, which became hot enough for a runaway reaction to start (see Fig. 9.3). Once started in the upper layer, the reaction then propagated throughout the reactor. If the steam had been cooler, say, 180 C, the runaway could not have occurred. ... 

TATTERSON Fluid Mixing and Gas Dispersion in Agitated Tanks TATTERSON Scale-up of Industrial Mixing Processes VVILLIG Environmental TQM... 

Before withdrawing a sample it is necessary to agitate it, even if it is a gas, and eventually heat the sample being careful to stay below temperatures which could cause evaporation of the lighter components. 

If agitation and heating are not practical as in the cases of large volumes, it is better to withdraw samples from various levels in order to get an average sample. 

The pour point is the lowest temperature at which an oil can still pour while it is cooled, without agitation, under standardized conditions. The pour point of paraffinic bases is linked to the crystallization of n-paraffins. The pour point of naphthenic bases is related to a significant viscosity increase at low temperatures. This property can be improved by additives. 

The pour point of crude oils is measured to give an approximate indication as to their pumpability . In fact, the agitation of the fluid brought on by pumping can stop, slow down or destroy the formation of crystals, conferring on the crude additional fluidity beyond that of the measured pour point temperature. 

Certain calibrated orifice instruments (Engler-type) provide viscosity measurements at temperature lower than pour point. This is possible because the apparatus agitates the material to the point where large crystals are prevented from forming whereas in other methods, the sample pour point is measured without agitation. 

The crankcase of a gasoline or diesel engine is in reality a hydrocarbon oxidation reactor oil is submitted to strong agitation in the presence of air at high temperature (120°C) furthermore, metals such as copper and iron, excellent catalysts for oxidation, are present in the surroundings. 

Antirust properties (inhibited mineral oils) NFT 60-151 ISO 7120 ASTM D 665 Spots on a test tube after agitation with oil water... 

If oil and water are mixed as an emulsion, dehydration becomes much more difficult. Emulsions can form as oil-in-water or water-in-oil if mixed production streams are subjected to severe turbulence, as might occur in front of perforations in the borehole. Emulsions can be encouraged to break (or destabilise) using chemicals, heat or just gentle agitation. Chemical destabilisation is the most common method and laboratory tests would normally be conducted to determine the most suitable combination of chemicals. 

Prior to about 1920, flotation procedures were rather crude and rested primarily on the observation that copper and lead-zinc ore pulps (crushed ore mixed with water) could be benefacted (improved in mineral content) by treatment with large amounts of fatty and oily materials. The mineral particles collected in the oily layer and thus could be separated from the gangue and the water. Since then, oil flotation has been largely replaced by froth or foam flotation. Here, only minor amounts of oil or surfactant are used and a froth is formed by agitating or bubbling air through the suspension. The oily froth or foam is concentrated in mineral particles and can be skimmed off as shown schematically in Fig. XIII-4. 

If two pure, immiscible liquids, such as benzene and water, are vigorously shaken together, they will form a dispersion, but it is doubtful that one phase or the other will be uniquely continuous or dispersed. On stopping the agitation, phase separation occurs so quickly that it is questionable whether the term emulsion really should be applied to the system. A surfactant component is generally needed to obtain a stable or reasonably stable emulsion. Thus, if a little soap is added to the benzene-water system, the result on shaking is a true emulsion that separates out only very slowly. Theories of... 

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

The diffusion layer widtli is very much dependent on tire degree of agitation of tire electrolyte. Thus, via tire parameter 5, tire hydrodynamics of tire solution can be considered. Experimentally, defined hydrodynamic conditions are achieved by a rotating cylinder, disc or ring-disc electrodes, for which analytical solutions for tire diffusion equation are available [37, 4T, 42 and 43]. 

A useful stirrer—sometimes termed a Hershberg stirrer— Fig. 11,7,5. for efficient agitation in round-bottomed vessels, even of... 

Mercury-sealed stirrers are used in the following operations (1) simultaneous stirring and refluxing of a reaction mixture (2) stirring the contents of a closed vessel (3) agitation with prevention of the escape of a gas or vapour and (4) stirring in an inert atmosphere, such as... 

Zinc cyanide. Solutions of the reactants are prepared by dis solving 100 g. of technical sodium cyanide (97-98 per cent. NaCN) in 125 ml. of water and 150 g. of anhydrous zinc chloride in the minimum volume of 50 per cent, alcohol (1). The sodium cyanide solution is added rapidly, with agitation, to the zinc chloride solution. The precipitated zinc cyanide is filtered off at the pump, drained well, washed with alcohol and then with ether. It is dried in a desiccator or in an air bath at 50°, and preserved in a tightly stoppered bottle. The yield is almost quantitative and the zinc cyanide has a purity of 95-98 per cent. (2). It has been stated that highly purified zinc cyanide does not react in the Adams modification of the Gattermann reaction (compare Section IV,12l). The product, prepared by the above method is, however, highly satisfactory. Commercial zinc cyanide may also be used. 

Triturate 20 g. of dry o-toluidine hydrochloride and 35 5 g. of powdered iodine in a mortar and then grind in 17 -5 g. of precipitated calcium carbonate. Transfer the mixture to a conical flask, and add 100 ml. of distilled water with vigorous shaking of the flask. Allow the mixture to stand for 45 minutes with occasional agitation, then heat gradually to 60-70° for 5 minutes, and cool. Transfer the contents of the flask to a separatory funnel, extract the base with three 80 ml. portions of ether, diy the extract with anhydrous calcium chloride or magnesium sulphate, and remove the excess of solvent. The crude 5-iodo-2-aminotoluene separates in dark crystals. The yield is 32 g. Recrystallise from 50 per cent, alcohol nearly white crystals, m.p. 87°, are obtained. 

Solubility in concentrated sulphuric acid. Place 3 0 ml. of pure concentrated sulphuric acid in a dry test-tube and add 0 -10 g. of a solid or 0 -20 ml. of a liquid. If the compound does not dissolve immediately, agitate for some time but do not heat. Observe any change in colour, charring, evolution of gaseous products, polymerisation accompanied by precipitation etc. 

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