Fluidization chemical processes

Fluidized-Bed Combustion The principles of gas-solid fluidization and their application to the chemical process industry are treated in Sec tion 17. Their general application to combustion is reviewed briefly here, and their more specific application to fluidized-bed boilers is discussed later in this section. 

Heterogeneous catalysts can be divided into two types those for use in fixed-bed processing wherein the catalyst is stationary and the reactants pass upward (flooded-bed) or downward (trickle-bed) over it, and those for use it slurry or fluidized-bed processing. Fixed-bed catalysts are relatively large particles, I/32 to 1 /4 inch, in the form of cylinders, spheres, or granules. Slurry or fluidized-bed catalysts are fine powders, which can be suspended readily in a liquid or gas, respectively. Fixed-bed processing is especially suited to large-scale production, and many important bulk chemicals are made in this mode. 

Matsen, J. M., Fluidized Beds, Scaleup of Chemical Processes Conversion from Laboratory Scale Tests to Successful Commercial Size Design, (A. Bisio, and R. L. Kabel, eds.) p. 347, John Wiley Sons, New York (1985)... 

This section covers recent advances in the application of three-phase fluidization systems in the petroleum and chemical process industries. These areas encompass many of the important commercial applications of three-phase fluidized beds. The technology for such applications as petroleum resid processing and Fischer-Tropsch synthesis have been successfully demonstrated in plants throughout the world. Overviews and operational considerations for recent improvements in the hydrotreating of petroleum resids, applications in the hydrotreating of light gas-oil, and improvements and new applications in hydrocarbon synthesis will be discussed. 

UNIPOL [Union Carbide Polymerization] A process for polymerizing ethylene to polyethylene, and propylene to polypropylene. It is a low-pressure, gas-phase, fluidized-bed process, in contrast to the Ziegler-Natta process, which is conducted in the liquid phase. The catalyst powder is continuously added to the bed and the granular product is continuously withdrawn. A co-monomer such as 1-butene is normally used. The polyethylene process was developed by F. J. Karol and his colleagues at Union Carbide Corporation the polypropylene process was developed jointly with the Shell Chemical Company. The development of the ethylene process started in the mid 1960s, the propylene process was first commercialized in 1983. It is currently used under license by 75 producers in 26 countries, in a total of 96 reactors with a combined capacity of over 12 million tonnes/y. It is now available through Univation, the joint licensing subsidiary of Union Carbide and Exxon Chemical. A supported metallocene catalyst is used today. 

More recent processes involving the oxidation of butane to a maleic anhydride intermediate, using both fixed-bed and fluidized-bed processes, have been commercialized. The maleic anhydride is subsequently hydrolyzed to maleic acid or esterified in the presence of methanol to dimethyl maleate, which can be reduced to BDO in the presence of hydrogen and catalyst. These processes are attractive due to the low cost of the butane feedstock. The method of choice to make BDO is often dictated by the local availability of the desired chemical feedstock. 

Yates, J.G., Fundamentals of fluidized-bed chemical processes, Butterworth, London, 1983. 

J. G. Yates, Fundamentals of Fluidized-Bed Chemical Processes, Butterworths, London,1983. 

Fluidized beds are beds of solid particles supported by upward flow of a gas or liquid. Because of their temperature uniformity, excellent heat transfer characteristics, and solids handling possibilities, fluidized beds have found wide application for physical and chemical processes. 

Matsen, J. M., Rossetti, S. J. and Halow, J. S. (1986). Fluidized Beds and Gas Particle Systems. In Encyclopedia of Chemical Processing and Design. Ed. J. J. McKetta. New York Marcel Dekker. 

Knowledge of these types of reactors is important because some industrial reactors approach the idealized types or may be simulated by a number of ideal reactors. In this chapter, we will review the above reactors and their applications in the chemical process industries. Additionally, multiphase reactors such as the fixed and fluidized beds are reviewed. In Chapter 5, the numerical method of analysis will be used to model the concentration-time profiles of various reactions in a batch reactor, and provide sizing of the batch, semi-batch, continuous flow stirred tank, and plug flow reactors for both isothermal and adiabatic conditions. 

A further example of using chemical fluidized-bed processes is that of plants where fluidizable solids are used as a heat transfer medium. Willing [98] describes the use of this process for the cracking of oil arrears, but fluidized-bed plants are also suitable for catalytic or gas-solid reactions. The easy controllability of the reactor temperature is emphasized by Baranek et al. [7], wherein the heat of reaction can be used by immersed coolers to generate steam. The isothermal behavior, and the possibility of both supplying and removing heat, are further advantages. 

Examples of the application of the Grashof number in heat transfer problems can be found, for example, in [14]. For examples where the Archimedes number is applied in solid/liquid systems (suspensions) see [22] and for sedimentation as well as fluidization examples please refer to textbooks dealing with unit operations in chemical process engineering. 

These attractive features bespeak the high efficienty of fast fluidized beds for both physical and chemical processing. 

Yates, J. G., Fundamentals cf Fluidized-Bed Chemical Processes, 3rd ed. London Butterworth, 1983. 

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