Radial centrifuges

Centrifugal casting allows for greater control of the distribution of phases, by controlling the time of separation. The two types of centrifugal casting equipment are shown in Fig. 9. For radial centrifuges (Fig. 9a), the sample is placed at a... 

Fig. 9. Scheme of SHS+centrifiigal casting (a) radial centrifuge (b) axial centrifuge. 1-sample container 2-reactant mixture 3-4gnitor 4-axle 5-ieactxx (Adapted from Merzhanov and Yukhvid, 1990)... 

External rotary gear pumps are particularly suitable for moderate-to-very high-kinematic viscosity liquids in the range of 100 to 500,000 centistokes for flow capacities to at least 1,500 gpm (0.252 mVs) and heads to at least 3,000 ft (914.4 m). They are moderately priced, but usually more expensive than radial centrifugal pumps. They cannot be used with liquids containing particles and do not give as smooth a flow rate as do radial centrifugal pumps. 

Many other specialized pumps are available for services that cannot be handled by radial centrifugal, external rotary gear, and plunger and piston reciprocating pumps. Specialized pumps are not considered here. Purchase-cost data are given next only for the three most commonly used types of pumps. 

Table 16.20 Typical Types of Radial Centrifugal Pumps and Fj Factors...

Figure 163 Base f.o.b. purchase cost for radial centrifugal pumps.

Assume we can purchase a radial centrifugal pump with a required NPSH > 5. 

A cyclone is a device that separates particulate solids from a fluid stream by a radial centrifugal force exerted on the particles. This force separates the solids from the gas by driving the solids to the cyclone wall, where they slide to the bottom solids outlet and are collected. Cyclones are used with almost all fluidized beds to remove solids from exit gas streams. 

The calculated values of temperature and ammonia concentration in the bulk gas and at the catalyst external surface are reported in Table 6.7 for the first catalyst bed of Fig. 6.2 in both axial and radial centrifugal flow. Since radial flow converters are usually filled with smaller-size catalyst particles than the catalyst considered here, from this point of view they are equivalent to axial converters, which are always filled with large-size catalysts to contain pressure drops. It also appears that the effects of mass and heat transfer at the external surface of the catalyst particle are oppositely directed so that they partly compensate for each other. We may conclude that in industrial converters their combined influence on the reaction rate is negligible compared to the inaccuracies inherent in the experimental determination of the intrinsic activity of the catalyst. In any case, interparticle phenomena can be readily incorporated as boundary conditions in the intraparticle problem ... 

Note In each region the radial particle flux due to the radial centrifugal force is perpendicular to the bulk flow of the fluid and the particles in the main flow (z) direction. 

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