Mixing devices

The materials of constmction for the mixing device and storage vessels must be selected carefully. Glass (qv), polytetrafluoroethylene, or certain kiads of stainless steels are usually used. Glass must be pickled with nitric acid before use. 

Kneading Devices These are closely related to the agitated pan but differ as being primarily mixing devices with heat transfer a secondary consideration. Heat transfer is provided by jacketed construction of the main body and is effected by a coolant, hot water, or steam. These devices are applicable for the compounding of divided solids by mechanical rather than chemical action. Apphcation is largely in the pharmaceutical and food-processing industries. For a more complete description, illustrations, performance, and power requirements, refer to Sec. 19. 

Conveyor-Belt Devices The metal-belt type (Fig. 11. 55) is the only device in this classification of material-haudhug equipment that has had serious effort expended on it to adapt it to indirecl heat-transfer seiwice with divided solids. It features a lightweight construction of a large area with a thin metal wall. ludirect-coohiig applications have been made with poor thermal performance, as could be expected with a static layer. Auxihaiy plowlike mixing devices, which are considered an absolute necessity to secure any worthwhile results for this seiwice, restrict applications. 

Stationaiy. shell or trough. There are a number of different types of mixers in which the container is stationary and material displacement is accomplished by single or multiple rotating inner mixing devices. 

In the previous section, a description of the various types of equipment commonly used for carrying out mixing operations was provided. Emphasis was placed on mechanical agitators since these have the broadest range of application, however there are other important devices worth noting, such as jet, pump, eductor, orifice, and inline mixing devices. Some of these important pieces of equipment are briefly described below. 

Mixing Valve This type of mixing device is normally a manually operated globe valve operated at 20 to 350 kPa pressure drop. Common use of this device in refinery operations is for water and crude oil mixing before a desalter and in caustic scrubbing operations. 

The performance equation of a mixer relates mixer size or mixing time to the input and output of the mixing device. The rate of transfer, r, incorporates the mass transfer coefficient, kL, and interfacial area, a, as calculated above. This rate can be used in conjunction with a material balance to relate concentrations of interest to time or size variables. 

Mercaptan extraction is used to reduce the total sulfur content of the fuel. When potassium isobutyrate and sodium cresylate are added to caustic soda, the solubility of the higher mercaptans is increased and they can be extracted from the oil. To remove traces of hydrogen sulfide and alkyl phenols, the oil is pretreated with caustic soda in a packed column or other mixing device. The mixture is allowed to settle and the product water washed before storage. 

Calculation of the induction time is crucial, since gaining a stable and continuous process requires residence times in the mixer < precipitation induction times in order to prevent incrustation in the mixing device. The induction... 

This oil is heated at 110° C. with a solution of bisulphate of sodium of 11° Beaume (42 kg. for 360 litres of water) in a vessel with a mixing device until the samples distilled every day show that the first running, which has an unpleasant smell, has reached the density of 0 936. This happens after about eight days (the first itinnine being about 8 kg.). 

Mixing Device 10 10 10 10 Plastic Stote Solid State... 

This mixing device contains no rnoMng parts, is relatively simple, and its cost can be quite reasonable when compared to mechanical driven mixers. 

Mixing Device I02 I03 I04 I05 Plastic State Solid State... 

The concept of the internal mixer is well accepted in the rubber industry, especially for the production of masterbatch compounds. Within a variety of materials the deformation of rubber compounds is relatively difficult due to the very high viscosity. Mixing devices have to be strongly powered and have to be designed in a very robust way in order to withstand the very high forces and momentum acting on the device. The most important benefits of an internal mixer are... 

In the last 20 years several attempts have been made to apply continuous mixing devices for the production of rubber compounds. The following devices have been applied with more or less success ... 

In conforming to an expected linear free energy relationship, the Ce(lV) oxidation of various 1,10-phenanthroline and bipyridyl complexes of Ru(II) in 0.5 M sulphuric acid are consistent with the requirements of the Marcus treatment . The results for the oxidation of the 3- and 5-sulphonic-substituted ferroin complexes by Ce(IV) suggest that the ligand does not function as an electron mediator, and that the mechanism is outer-sphere in type. Second-order rate coefficients for the oxidation of Ru(phen)j, Ru(bipy)3, and Ru(terpy)3 are 5.8x10, 8,8 X 10, and 7.0 x 10 l.mole . sec, respectively, in 0.5 M H2SO4 at 25 °C a rapid-mixing device was employed. 

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