Bedding properties

Experiment HGR-13. A 2-ft bed of commercial catalyst was tested as a packed bed of 0.25-in. pellets (see Table I for bed properties). This test was similar to experiment HGR-14 in which the catalyst bed consisted of parallel plates sprayed with Raney nickel. The experiment was... 

The Bernoulli equation relates the pressure drop across the bed to the fluid flow rate and the bed properties ... 

The theory behind the method to measure the burning rate was not explicitly presented by Lamb et al. Obviously, the mathematical model must be based on the bed properties, such as packing ratio, loading density, bed height, as well as the trolley speed. No discussion is presented about the limitations and assumptions of the method. 

In this section we refer to the same industrial reactor as in 7.5.1, with its data given on p. 508. Further reactor specifications and catalyst-bed properties of this plant are as follows. 

It should be noted that the coefficient fi is not an independent parameter it depends on the bed properties. In a fluidized bed, particles are closely spaced it is assumed that the Ergun equation can be applied to account for the pressure drop in the bed. Thus, from Eq. (5.358), we have... 

Model I is based on the assumptions that the fluid flow rate, temperature, pressure, solvent density and bed properties are constant during extraction. 

Scientific approaches to improve bed fluidity are potentially important for fluidized bed technology. Also, further quantitative relations between bubble splitting and bed properties would be very helpful in planning and scaling-up fluidized catalyst beds. 

Gas-liquid distribution. Oil and hydrogen are fed into the top of the reactor and distributed uniformly over the catalyst bed. Further, down the catalyst bed, flow maldistribution (i.e., channeling, wall flow) may take place owing to non-uniform bed properties. 

A few of the early bubbling bed modeling approaches are assessed in the subsequent sub-sections. Reliable engineering models, at this simple level of complexity, can only be derived based on appropriate empirical information characterizing the important bed properties. The theory and typical param-eterizations used to determine the relevant behavior of the gas and solids in the bubble, cloud, emulsion and wake regions are outlined. 

In an ideal fixed-bed reactor, plug flow of gas is assumed. This is, however, not a good assumption for reactive solids, because the bed properties vary with position, mainly due to changing pellet properties (and dimensions in most cases), and hence the use of nonideal models is often necessary. The dispersion model, with all its limitations, is still the most practical one. The equations involved are cumbersome, but their asymptotic solutions are simple, particularly for systems... 

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