Pressure drop, packings 706 Subject

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. 

For particles with very large pores, pore volume is sometimes sacrificed for mechanical stability. For example, when particles varying in pore size from 10 to 385 nm, but with nearly identical porosities, were subjected to pressure tests, those with the largest pore sizes collapsed at lower pressure drops (see Reference 23, p. 174). Thus, the mechanical stability of larger pore size particles can only be maintained by reducing the pore volume. Alternatively, larger pore size particles must be slurry packed at lower pressures, thereby decreasing the stability and lifetime of the packed bed. 

Manual injectors are operationally qualified for repeatability and carryover. Autosamplers are additionally checked for accuracy. Injection systems are qualified after the solvent dehvery system and the detector. To eliminate subjective effects, the chromatographic column is excluded from the setup for qualifying injectors. The column is replaced by a low internal diameter, significant length stainless steel tubing, generating a pressure drop similar to that in a packed column (about 100 bar). 

Darcy s Law Darcy. Darcy s Law states that the rate of flow of a fluid, subjected to a low pressure difference, through a packing of particles is very nearly proportional to the pressure drop per unit length of the packing. This Law forms the basis of methods for the determination of the permeability of ceramics. The darcy is the c.g.s. unit of permeability a material has a permeability of 1 darcy if in a section... 

Newton s law is applied in order to derive the linear momentum balance equation. Newton s law states that the sum of all forces equals the rate of change of linear momentum. The derivation/application of this law ultimately provides information critical to any meaningful analysis of most chemical reactors. Included in this information are such widely divergent topics as flow mechanisms, the Reynolds number, velocity profiles, two-phase flow, prime movers such as fans, pumps and compressors, pressure drop, flow measurement, valves and fittings, particle dynamics, flow through porous media and packed beds, fluidization— particularly as it applies to fluid-bed and fixed bed reactors, etc. Although much of this subject matter is beyond the scope of this text, all of these topics are treated in extensive detail by Abulencia and Theodore. ... 

A multichannel packed bed reactor was also produced (Figure 9.23) [68,69]. The gas flow is distributed by star-type manifolds to the 10 reaction units. However, to achieve commercial production, a complex arborescence structure is required, taking into account two phase flow distribution and a multitude of manifolds for gas and liquid inlets. Each packed bed channel is subject to a large pressure drop. Large pressure drop indicates high energy requirements and higher costs [95]. 

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