Pressure drop in a packed bed

The pressure drop in a packed bed depends on the particle Reynolds number. When (Re)p is small, Equation (3.17) becomes... 

To calculate the pressure drop in a packed bed, the semi-empirical Ergun equation [54] may be used... 

The zeolite crystals are in the form of fine powders, which would cause a very high pressure drop in a packed bed. They have to be formed into granules of approximately 3 mm in diameter, by using clay binders, such as kaolinite and montmorillonite. The methods consist of pelletization with binders under pressure into short cylinders, wet extrusion with a fluid into continuous cylinders, and granulation by rolling with binders into spheres. They also need to be dehydrated and calcined to remove volatile components before use. 

Suppose we have measured the total pressure drop in a packed bed of known length. Then, one expressed the opinion that to calculate the pressure gradient, we have to only divide the pressure drop with the bed length. Do you agree ... 

The Ergun equation relates the pressure drop in a packed bed to the flow rate and the properties of particle and gas. However, the application of this equation has been extended beyond the limits of fixed bed systems since it was first formulated in 1951. Thus, a detailed account of the origin of this equation is necessary. 

The flow through the straight channels of the monolith matrix is subject to very low pressure drops in a packed bed with the same external geometric surface area the pressure drop may be greater by two or three orders of magnitude. 

Input Data and Computer Output for for Pressure Drop In a Packed Bed... 

Table 3-17 gives the Reynolds number, friction factor, and pressure drop of catalyst pellets of 0.25 inch and at different particle length. Table 3-18 shows a typical input data and computer output with PL = 0.25 inch. The simulation exercise gives a pressure drop of 68.603 Ib/in. The results show that the pressure drop in a packed bed depends on size and shape of the particles. 

C THIS PROGRAM CALCULATES THE TOTAL PRESSURE DROP IN A PACKED BED... 

Pressure drop in a packed bed reactor to niake alkylated cyclohexanols, [ Ed. P4-22I... 

In Figure 11.11, the pressure drop in a packed bed is compared with that in microchannel of different section geometries. It turns out that the pressure drop in a packed bed is two to three times higher compared to that in microchannels. 

Compression costs are significant in large-scale adsorption systems for gases thus, pressure drop is critically important since it controls compression costs. A resonable gas velocity is 100 ft/min tSeider et al.. 20091. Pressure drop can be calculated from well-known correlations for flow in packed beds. For example, the pressure drop in a packed bed of rigid particle in laminar flow is tBird et al.. 1960 ... 

Often we have irregular-shaped particles in the bed, and it is more convenient to use the particle size and shape factor in the equations. First we substitute for the efiective mean diameter the term (t>sDf where Dp now represents the particle size of a sphere having the same volume as the particle and 4>s the shape factor. Often, the value of Dp is approximated by using the nominal size from a sieve analysis. Then Eq. (3.1-20) for pressure drop in a packed bed becomes... 

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