Fluidized process

During World War II, production of butadiene (qv) from ethanol was of great importance. About 60% of the butadiene produced in the United States during that time was obtained by a two-step process utilizing a 3 1 mixture of ethanol and acetaldehyde at atmospheric pressure and a catalyst of tantalum oxide and siHca gel at 325—350°C (393—397). Extensive catalytic studies were reported (398—401) including a fluidized process (402). However, because of later developments in the manufacture of butadiene by the dehydrogenation of butane and butenes, and by naphtha cracking, the use of ethanol as a raw material for this purpose has all but disappeared. 

The calcination of A1(0H),3 to AI2O3 in a circulating fluidized process produces a high-grade product. The process combines the use of circulating, bubbling, and transport beds to achieve high thermal efficiency. See Fig. 17-28. 

Several important applications of fluid beds exist outside the petroleum industry. Fluid bed roasting of pyritic ores is widely used in the metallurgical industry. Calcination of lime is a commercial process. There are also fluidization processes for various nuclear processing steps. 

Most of the simulation effort has been applied to fluidized bed combustors which use relatively large size particles. Simulation can also be used for other fluidization processes in the petrochemical industry. Research should be undertaken to identify the proper scaling parameters for beds fluidized with smaller particles. Similar simulations may also apply to components such as cyclones. 

The purpose of this section is to anticipate and consider risks inherent in fluidization and also to summarize the more thoroughly documented and well-understood risks associated with the kinds of peripheral systems and facilities likely to be found in manufacturing plants using fluidization processes. 

II. Idealization of the Fluidizing Process Empirical Deductions from... 

Description DCC is a fluidized process to selectively crack a wide variety of feedstocks into light olefins. Propylene yields over 24 wt% are achievable with paraffinic feeds. A traditional reactor/regenerator unit design uses a catalyst with physical properties similar to traditional FCC catalyst. The DCC unit may be operated in two operational modes maximum propylene (Type I) or maximum iso-olefins (Type II). Each operational mode utilizes unique catalyst as well as reaction conditions. DCC maximum propylene uses both riser and bed cracking at severe reactor conditions, while Type II utilizes only riser cracking like a modern FCC unit at milder conditions. 

Description DCC is a fluidized process to selectively crack a wide variety of feedstocks into light olefins. Propylene yields over 24 wt% are achievable with paraffinic feeds. A traditional reactor/regenerator unit design uses a catalyst with physical properties similar to tra-... 

Phosphate rock is calcined to remove carbonaceous material before being digested with sulfuric acid. Several different fluidization processes have been commercialized for the direct reduction of hematite to high-iron, low-oxide products. Foundry sand is also calcined to remove organic binders and release fines. 

The principles of fluidization processes are described in Richardson et al. (2002). The design of fluidized bed reactors is discussed by Rase (1977). 

This was the first application of a fluidized bed to a process that necessitates removal of large heat of reacticm (about 450 kcal/gm-mole naphthalene) and high yield. The fluidized process surpassed fixed-bed processes in safe operation at high ccmcentration, in yield, in reduced pollution, and in plant cost—probably because the reacticm was rather simple and the products were stable. Fluid bed catalysts currently in use... 

C. Jutka, R. Brusewitz, D. Hesse, Fluidized Processes, AIChE Symp. Ser No. 289,... 

The operating conditions of a fluid bed are to a high degree dictated by the properties of the material to be dried, as already indicated. One parameter can be chosen regardless of the fluidization process, namely, the fluidization air temperature. For most products, however, the temperature is of primary importance, since the fluidized state results in very high heat-transfer rates so that heat sensitivity may restrict temperature and thereby prolong process time. 

Grace, J.R. Agricola aground characterization and interpretation of fluidization phenomena. In Fluidized Processes Weimer, A.W., Ed. AIChE Symp. Ser. 88, 1992. 

Stirred tank and fluidized processes for stereoisomer resolution share the following characteristics ... 

The Namorado Sandstone is composed primarily of massive fine- to very fine-grained arenites. Sedimentary structures are rare, but occasional normal grading is observed. The fluidization process is identified by unusual dish and pillar structures. Rarely, individual beds present ripple cross-laminated divisions at the top. Individual beds have an average thickness of Im. Several individual beds may be amalgamated, resulting in sandy intervals up to 10 m thick. Individual beds or cycles are capped by thin beds of shales and calcilutites. 

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