Solid granular

Fig. 4.12 (a) Adsorption isotherm for (i) a solid made up of mesoporous grains (ii) a solid which is wholly microporous (iii) a granular solid with the same mesoporous system as in (i) but containing also micropores having a total micropore volume given by the plateau of isotherm (ii). The adsorption is expressed in arbitrary units, (h) t-plots corresponding to isotherms (i) and (iii). The a,-plots are similar except for the scale of... 

The stationary phase in LC is a fine granular solid such as silica gel. It can be used as such (mainly for nonpolar compounds), or the granules can be modified by a surface-bonded coating that changes (reverses) the polarity of the gel. A very small selection of stationary phases is listed in Table 35.2. 

Porous Media Packed beds of granular solids are one type of the general class referred to as porous media, which include geological formations such as petroleum reservoirs and aquifers, manufactured materials such as sintered metals and porous catalysts, burning coal or char particles, and textile fabrics, to name a few. Pressure drop for incompressible flow across a porous medium has the same quahtative behavior as that given by Leva s correlation in the preceding. At low Reynolds numbers, viscous forces dominate and pressure drop is proportional to fluid viscosity and superficial velocity, and at high Reynolds numbers, pressure drop is proportional to fluid density and to the square of superficial velocity. 

For granular solids of mixed sizes the average particle diameter may be calculated as... 

For isothermal compressible flow of a gas with constant compressibility factor Z through a packed bed of granular solids, an equation similar to Eq. (6-114) for pipe flow may be derived ... 

Capillary Flow Moisture which is held in the interstices of solids, as liquid on the surface, or as free moisture in cell cavities, moves by gravity and capiUarity, provided that passageways for continuous flow are present. In diying, liquid flow resulting from capiUarity appUes to liquids not held in solution and to aU moisture above the fiber-saturation point, as in textiles, paper, and leather, and to all moisture above the equiUbrium moisture content at atmospheric saturations, as in fine powders and granular solids, such as paint pigments, minerals, clays, soU, and sand. 

Indirect type, batch or continuous operation for pharmaceuticals such as peniciUin and blood plasma. Expensive. Used on beat-sensitive and readily oxidized materials under Liquids under Liquids under Liquids used on pharmaceuticals and related products which cannot be dried successfuby by other means. Applicable to fine chemicals under Granular solids cial cases such as emulsion-coated films under Granular solids... 

Suited to batch operation. At large capacities, investment and operating costs are high. Long drying times See comments under Granular solids Not apphcahle See comments under Granular solids... 

Roto-Louvre diyers are suitable for processing coarse granular solids which do not offer high resistance to air flow, require intimate gas contacting, and do not contain significant quantities of dust. 

When the solid is one of the reactants, such as in ore roasting, the flow must be continuous and precise in order to maintain constant conditions in the reactor. Feeding of free-flowing granular solids into a fluidized bed is not difficult. Standard commercially available sohds-weighiug and -conveying equipment can be used to control the rate and dehver the solids to the feeder. Screw conveyors, dip pipes, seal legs, and injectors are used to introduce the solids into the reactor... 

The following equations, which have been tested in centrifugal dewatering of granular solids, prove useful ... 

Figure 3. Shows angle of repose for granular solids.

AP equation arising from simultaneous turbulent kinetie and viseous energy losses that is applieable to all flow types. Ergun s equation relates the pressure drop per unit depth of paeked bed to eharaeteristies sueh as veloeity, fluid density, viseosity, size, shape, surfaee of the granular solids, and void fraetion. The original Ergun equation is ... 

But how can we estimate the pressure-loss coefficient A Stegmaier - has summarized horizontal transport for several fine-granular solids by a correla tion which contains some characteristics of the material. The same idea has been used by Weber, who has found a correlation of the pressure-loss coefficient for vertical pneumatic conveyance based on data measured by Flatow. In order to express these models, we first introduce two dimensiitnless numbers... 

The o-aminophenylpropiolic acid 4 (20 g) in water (60 mL) and aqueous ammonia (9 mL, d = 0.88) was added with shaking during 15 minutes to a mixture prepared from ferrous sulfate (220 g), water (440 mL), and aqueous ammonia (110 mL, d = 0.88). After 45 minutes, with occasional shaking but no external cooling, the suspension was filtered. The residue was washed with water, and the combined filtrates were treated with ammonium acetate (60 g) and made weakly acidic with acetic acid. The solution was then cooled to 0°C by addition of crushed ice, and then made acidic to Congo-red with concentrated hydrochloric acid (70-80 mL). Additional hydrochloric acid (20 mL, 2 N) was immediately added, and the turbid solution which resulted was diazotized with 20% aqueous sodium nitrite, after which the mixture was kept at 70°C. The cinnoline acid 6 was separated over 45 minutes as a dark brown, granular solid (12.5 g), m.p. 260-265°C. ... 

Handling Slurries and Granular Solids Using steam as the motive fluid... 

Gamson et a/.t49) have successfully used the. /-factor method to correlate their experimental results for heat and mass transfer between a bed of granular solids and a gas stream. 

Gamso.v B.W., Thodos. G. and Hougfn. O.A. Trans Am. Inst. Chem. Eng. 39 (1943) 1. Heat mass and momentum transfer in the flow of gases through granular solids. 

Heywood, N. (1991) The Storage and Conveying of Wet Granular Solids in the Process Industries (Royal Society of Chemistry). 

Granular solid filters (see Fig. 16-4) are cleaned by backwashing with water. The backwashing is usually preceded by an air scouring to assure better cleaning.30 The backflow water rate should be fast enough to fluidize the bed. 

You have a granular solid with SG = 4, which has particle sizes of 300 pm and smaller. You want to separate out all of the particles with a diameter of 20 pm and smaller by pumping water upward through a slurry of the particles in a column with a diameter of 10 cm. What flow rate is required to ensure that all particles less than 20 pm are swept out of the top of the column If the slurry is pumped upward into the bottom of the column through a vertical tube, what should the diameter of this tube be to ensure that none of the particles settle out in it ... 

Yuregir, K. R., Ghadiri, M., and Clift, R., Observation of Impact Attrition of Granular Solids, Powder Tech., 49 53 (1986)... 

Granular solids and powders charge more readily than any other commercially or industrially important form of material. It is fair to say that, when such materials are handled or processed, particle charging is virtually inevitable. In this section, the important qualitative and quantita-... 

Triboelectric Series. Prediction of triboelectric behavior in granular solids is hampered by difficult-to-control factors such as particle shape, prior mechanical contacts, material purity, and particle moisture content (which is usually related to airborne humidity). In the absence of any reliable predictive model for powder electrification, the practical requirements of industry necessitate an empirical approach (Taylor and Seeker,... 

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