fluidization

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fluidization

[‚flü·ə·də′zā·shən]
(chemical engineering)
A roasting process in which finely divided solids are suspended in a rising current of air (or other fluid), producing a fluidized bed; used in the calcination of various minerals, in Fischer-Tropsch synthesis, and in the coal industry.

Fluidization

The processing technique employing a suspension or fluidization of small solid particles in a vertically rising stream of fluid—usually gas—so that fluid and solid come into intimate contact. This is a tool with many applications in the petroleum and chemical process industries. Suspensions of solid particles by vertically rising liquid streams are of lesser interest in modern processing, but have been shown to be of use, particularly in liquid contacting of ion-exchange resins. However, they come in this same classification and their use involves techniques of liquid settling, both free and hindered (sedimentation), classification, and density flotation. See Mechanical classification

The interrelations of hydromechanics, heat transfer, and mass transfer in the gas-fluidized bed involve a very large number of factors. Because of the excellent contacting under these conditions, numerous chemical reactions are also possible—either between solid and gas, two fluidized solids with each other or with the gas, or most important, one or more gases in a mixture with the solid as a catalyst. In the usual case, the practical applications in plants have far outrun the exact understanding of the physical, and often chemical, interplay of variables within the minute ranges of each of the small particles and the surrounding gas phase.

With such excellent opportunities for heat and mass transfer to or from solids and fluids, fluidization has become a major tool in such fields as drying, roasting, and other processes involving chemical decomposition of solid particles by heat. An important application has been in the catalysis of gas reactions, wherein the excellent opportunity of heat transfer and mass transfer between the catalytic surface and the gas stream gives performance unequaled by any other system. See Fluidized-bed combustion, Gas absorption operations, Heat transfer, Unit operations

References in periodicals archive ?
Again, with the increase in initial static bed height ([H.sub.s]), the bed expansion and fluctuation ratios are observed to decrease because of more materials in the bed requires more flow of fluid to fluidize. It is also observed that the bed expansion and fluctuation ratios decrease with the increase with particle size ([d.sub.p]) for both the processes because of more void spaces among the bed materials which leads to decrease in the number of the bubble formation in the bed.
The aeration rate is set at a value high enough to fluidize the solids above the aeration point whilst the solids below are in packed bed mode.
Patterns continued to be made daily under the new conditions, and a continued reduction in scrap further validated the theory that the flow of steam through the vents was able to fluidize the beads and generate a void in locations where the pattern was thin.
The molding system utilizes the air impulse compaction process in which air pressure from 3-5 bar/sec is used during mold filling to fluidize the sand grains and allow each to slide over one another to ensure homogenized filling of all the free space on each pattern.
Homogeneous [N.sub.2]O chemistry at fluidized bed combustion conditions: a kinetic fluidize study // Combust.
In most designs, the water/oil carried in the compressed air collects on the heater's fluidizing membrane, reducing its permeability and ability to fluidize the sand.
The Dyna-Slide air activated gravity conveyor is said to efficiently combine low air pressure and gravity to fluidize and convey most types of fine dry granular materials such as carbon black, according to the manufacturer.
All equipment and systems covered emphasize complete dust containment and the ability to handle non-freeflowing, as well as free-flowing bulk solid materials ranging from large pellets to sub-micron powders, including difficult-to-handle products that can pack, cake, seize, fluidize, plug or smear, without the separation of blended products.
As the amplitude was increased, the material started to fluidize and actually fushed out of the hopper and over the sides of the tray.
It mechanically fluidizes the product, ensuring an efficient and gentle mixing process regardless of density, shape or size.
Superheated steam, at flow rates up to 250 lb/hr (113 kg/hr) and temperatures reaching 1,100 [degrees] F (870 [degrees] K), fluidizes the bed during the pyrolysis cycle phase.
A new retrofittable device for wood flour and other hard-to-feed additives fluidizes the material at the silo or bin discharge outlet.