Flow of solids

G. Beilby, Aggregation and Flow of Solids, Macmillan, New York, 1921. 

A. W. Jen ike, Storage and Flow of Solids, Bulletin 123, Engineering Experiment Station, University of Utah, 1964, rev. 1980. 

A powder s strength increases significantly with increasing previous compaction. The relationship between the unconfined yield stress/, or a powder s strength, and compaction pressure is described by the powder s flow function FE The flow function is the paramount characterization of powder strength and flow properties, and it is calculated from the yield loci determined from shear cell measurements. [Jenike, Storage and Flow of Solids, Univ. of Utah, Eng. Exp. Station Bulletin, no. 123, November (1964). See also Sec. 21 on storage bins, silos, and hoppers.]... 

I he mixture clement shown in Fig. 14.15 contains the flowing gas and solid particles. The partial densities of these two elements are pg and p. respectively. The void fraction is and this can be interpreted as the partial cross-sectional area for gas flow (see Eq. (14.13)). This means that if the pressure of the gas is p, then the pressure force per unit area of the total mixture affecting the flow of gas is (pp and the pressure force affecting the flow of solids is 1 -

[Pg.1343]

The two-layer model is being progressively updated as fresh experimental results and correlations become available. The most satisfactory starting-point for anyone wishing to use the model to calculate pressure gradients for flow of solids-liquid mixtures in a pipeline is the text of SHOOK and Roc.o(52) which includes a worked example. However, there are many pitfalls to be avoided in this area, and there is no substitute for pracucal experience gained by working in the field. 

Figure 5.18. Pressure drop for flow of solids in pneumatic conveying...

STREAT, M. Hydrotransport 10 (BHRA, Fluid Engineering, Innsbruck, Austria), (Oct. 1986). Paper Bl. Dense phase flow of solid-water mixtures in pipelines A state of the arl review. 

Cijoete, F. L. D, Miller, A. I., and Streat, M. Trans. Inst. Chem. Eng. 45 (1967) T392. Dense phase flow of solid-water mixtures through vertical pipes. 

The bubbles play the role of the gas phase. The role of the liquid is played by an emulsion phase that consists of solid particles and suspending gas in a configuration similar to that at incipient fluidization. The quasi-phases are in cocurrent flow, with mass transfer between the phases and with a solid-catalyzed reaction occurring only in the emulsion phase. The downward flow of solids that occurs near the walls is not explicitly considered in this simplified model. 

It is well known that solid materials are characterized by lack of relative motion between the constituent atoms compared with liquids, which results in NMR linewidths much broader than for liquids. Also, it often happens that solids have much longer spin-lattice relaxation 7 than in liquid samples. Thus, studying NMR of solids is more difficult than liquids and studying flows of solid material would seem to be quite impractical. 

Screw conveyors, also called worm conveyors, are used for materials that are free flowing. The basic principle of the screw conveyor has been known since the time of Archimedes. The modem conveyor consists of a helical screw rotating in a U-shaped trough. They can be used horizontally or, with some loss of capacity, at an incline to lift materials. Screw conveyors are less efficient than belt conveyors, due to the friction between the solids and the flights of the screw and the trough, but are cheaper and easier to maintain. They are used to convey solids over short distances, and when some elevation (lift) is required. They can also be used for delivering a metered flow of solids. 

The science of the deformation and flow of matter the study of a range of phenomena extending from the plastic flow of solids to the behaviour of fluids under extreme conditions. Rheometer... 

A. W. Jenike, Storage and Flow of Solids, Bull, of the Univ. of Utah, Utah Engineering Expt. Station, 53 (1964). 

With fixed-bed updraft gasifiers, the air or oxygen passes upward through a hot reactive zone near the bottom of the gasifier in a direction countercurrent to the flow of solid material. Exothermic reactions between air/oxygen and the... 

Flow Measurements Measurement of flow rates of clean gases presents no problem. Flow measurement of gas streams containing solids is almost always avoided. The flow of solids is usually controlled but not measured except solids flows added to or taken from the system. Solids flows in the system are usually adjusted on an inferential basis (temperature, pressure level, catalyst activity, gas analysis, heat balance, etc.). In many roasting operations, the color of the calcine discharge material indicates whether the solids feed rate is too high or too low. 

In Step 8, accessed frozen agent is hydrolyzed with hot caustic (when processing GB and VX) or hot water (when processing HD), and agent-contaminated metal parts from the cryofracturing step are washed in one of two PRHs. The PRHs are smaller but similar in function and construction to the two ERHs (see Table 5-1). The liquid flow in the PRH is countercurrent to the flow of solids. The PRHs are externally steam heated to maintain the temperature at the desired level. 

The flow of solids through an orifice depends on the ability of the particles to dilate in the region of the aperture. Flow will occur if the shear force exerted by the superincumbent material exceeds the shear strength of the powder near the outlet. 

If uc is the superficial flowrate of the slurry, then the rate of flow of solids through the filter at depth Z is ucC per unit area. Thus the rate of accumulation of solids in a distance dZ = —uc(9C/dl) dZ. If o is the volume of solids deposited per unit volume of filter at a depth Z, the rate of accumulation may also be expressed as (do/dt) dZ. 

Figure 10.4. Flow of solids and liquids in Dorr classifier...

The principles of fluidisation, discussed in Chapter 6, are applied in this type of dryer, shown typically in Figure 16.25. Heated air, or hot gas from a burner, is passed by way of a plenum chamber and a diffuser plate, fitted with suitable nozzles to prevent any back-flow of solids, into the fluidised bed of material, from which it passes to a dust separator. Wet material is fed continuously into the bed through a rotary valve, and this mixes immediately with the dry charge. Dry material overflows through a downcomer to an integral after-cooler. An alternative design of this type of dryer is one in which a thin bed is used. 

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