Applications of Fluidization

The use of fluidization processing was developed mainly by the petroleum and chemical industries tor operations where the very high heat transter coefficients and the high degree ot uniformity ot temperature within the bed enabled the development ot processes, which would otherwise be impracticable. Fluidization technologies are nowadays used quite extensively in many industries where it is desirable to bring about intimate contact between small solid particles and a gas stream. 

Fluidized catalysts are also used in the synthesis of high-grade fuels from mixtures of carbon monoxide and hydrogen obtained either by coal carbonization or from partial oxidation of methane. An important application in the chemical industry is the oxidation of naphthalene to phthalic anhydride, which is an important reagent in the chemical industry used for large-scale production of plasticizers for plastics. It is also used in the chemical industry for the production of certain dyes. 

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TABLE 25-46 Full-Scale Commercial Applications of Fluidized Bed Process... 

Application of fluidized reactor in photocatalytic decomposition of gaseous acetic acid and ammonia... 

Squires, A. M., Applications of Fluidized Beds in Coal Technology, lecture, Intern. School on Heat and Mass Transfer Problems in Future Energy Production, Dubrovnik, Yugoslavia (1975a)... 

When a chemical reaction occurs in the system, each of these types of behavior gives rise to a corresponding type of reactor. These range from a fixed-bed reactor (Chapter 21-not a moving-particle reactor), to a fluidized-bed reactor without significant carryover of solid particles, to a fast-fluidized-bed reactor with significant carryover of particles, and ultimately a pneumatic-transport or transport-riser reactor in which solid particles are completely entrained in the rising fluid. The reactors are usually operated commercially with continuous flow of both fluid and solid phases. Kunii and Levenspiel (1991, Chapter 2) illustrate many industrial applications of fluidized beds. 

The effects of adsorption and desorption on the performance of fluidized beds are discussed elsewhere. Adsorption of carbon disulfide vapors from air streams as great as 300 nr/s (540,000 ft3/min) in a 17-m- (53-ft-) diameter unit has been reported by Avery and Tracey ( The Application of Fluidized Beds of Activated Carbon to Recover Solvent from Air or Gas Streams, Tripartate Chemical Engineering Conference, Montreal, Sept. 24, 1968). 

In considering heat transfer in gas-solid fluidization it is important to distinguish between, on the one hand, heat transfer between the bed and a heat transfer surface (be it heated bed walls or heat transfer coils in the bed) and, on the other hand, heat transfer between particles and the fluidizing gas. Much of the fluidization literature is concerned with the former because of its relevance to the use of fluidized beds as heterogeneous chemical reactors. Gas-particle heat transfer is rather more relevant to the food processing applications of fluidization such as drying, where the transfer of heat from the inlet gas to the wet food particle is crucial. 

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