Fluid-bed technique

Extrusion with the aid of a vacuum applied to the screw. The process is applied particularly in the preparation of extrudates to be vulcanised by either the liquid curing medium or fluid bed techniques. It assists in removing the volatiles from the compound and thus improves the quality of the extrudate. 

The catalyst widely used is based on copper(II) chloride impregnated on alumina. The highly exothermal reaction is carried out at temperatures around 200 °C and pressures of 1.5-5 bar, in fixed-bed or fluid-bed reactors. The fluid-bed technique offers more intensive heat transfer, prevents the occurrence of hot spots and allows more efficient catalyst regeneration. Ethylene conversion of 93-97% can be achieved with selectivity in EDC of 91-96%. 

In a modification of the fluid bed technique, the product to be coated, instead of being preheated, is passed over the bed, and the powder is attracted to it by a static charge. Then it is passed through a heating oven to fuse it into a finished coating. This process can be used for either discrete or continuous products. 

Globulation is the formation of droplets of solution, slurry, or melt followed by solidification by prilling, spray drying, or fluid bed techniques. Control of particle size is best achieved in fluidized beds. 

Prinderre P, Cauture E, Piccerelle P, et al. Evaluation of some protective agents on stability and controlled release of oral pharmaceutical forms by fluid bed technique. Drug Dev Ind Pharm 1997 23 817-826. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Process Va.ria.tlons. The conventional techniques for tea manufacture have been replaced in part by newer processing methods adopted for a greater degree of automation and control. These newer methods include withering modification (78), different types of maceration equipment (79), closed systems for fermentation (80), and fluid-bed dryers (81). A thermal process has been described which utilizes decreased time periods for enzymatic reactions but depends on heat treatment at 50—65°C to develop black tea character (82). It is claimed that tannin—protein complex formation is decreased and, therefore, greater tannin extractabiUty is achieved. Tea value is beheved to be increased through use of this process. 

Employing wood chips, Cowan s drying studies indicated that the volumetric heat-transfer coefficient obtainable in a spouted bed is at least twice that in a direct-heat rotaiy diyer. By using 20- to 30-mesh Ottawa sand, fluidized and spouted beds were compared. The volumetric coefficients in the fluid bed were 4 times those obtained in a spouted bed. Mathur dried wheat continuously in a 12-in-diameter spouted bed, followed by a 9-in-diameter spouted-bed cooler. A diy-ing rate of roughly 100 Ib/h of water was obtained by using 450 K inlet air. Six hundred pounds per hour of wheat was reduced from 16 to 26 percent to 4 percent moisture. Evaporation occurred also in the cooler by using sensible heat present in the wheat. The maximum diy-ing-bed temperature was 118°F, and the overall thermal efficiency of the system was roughly 65 percent. Some aspec ts of the spouted-bed technique are covered by patent (U.S. Patent 2,786,280). 

Several processes based on non-precious metal also exist. Because of high catalyst deactivation rates with these catalyst systems, they all require some form of continuous regeneration. The Fluid Hydroforming process uses fluid solids techniques to move catalyst between reactor and regenerator TCR and Hyperforming use some form of a moving bed system. 

Avidan and Edwards (1986) successfully scaled up from bench scale to demonstration plant from 0.04 m to 0.6 m diameter while maintaining nearly 100% conversion for a fluid bed methanol to gasoline process. In this case, they ran at a superficial gas velocity which was high enough to be in the turbulent flow regime suppressing bubbles. By this technique they eliminated the losses associated with gas bypassing in bubbles. 

Reh, L., Calcining Aluminum Trihydrate in a Circulating Fluid Bed, a New Technique of High Thermal Efficiency, Metallurges, Rev. Activ., 1972(15) 58-60 (1972)... 

Any method of vulcanising rubber products which proceeds without interruption from start to finish as compared to the method of vulcanising separate batches of products or sections of a product. Continuous vulcanisation processes include the cold curing of proofed cloth, the vulcanisation of belting and flooring, of cables and certain extruded products by either the Liquid Curing Medium, Fluid Bed, Microwave, or Hot Air techniques. 

The technique of passing a gas into a solid which is in the form of tiny granules and thus making the solid behave as if it were a dense, viscous liquid. Fluidised materials may be easily piped from place to place, but a particular application in the rubber industry is the vulcanisation of extruded sections. See Fluid Bed Vulcanisation. Fluorinated Elastomers... 

In the fluid-bed granulation process, moisture control is the key parameter that needs to be controlled. Faure et al. (133) have used process control for scale-up of a fluidized bed process. They used infra-red probes to monitor moisture. As there are normally large numbers of inter-related variables, they used computerized techniques for process control, such as fuzzy logic, neural networks, and models based on experimental techniques. 

Scale-up is normally identified with an incremental increase in batch size until a desired level of production is obtained. The fluid-bed process, similar to other granulation techniques, requires an understanding of the importance of characterization of the raw materials, especially of an active... 

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