Porosity solid compressive pressure

The drag that is imposed on each particle is transmitted to adjacent particles. Therefore, the net solid compressive pressure increases as the filter plate is approached, resulting in a decrease in porosity. Referring to Figure 4A, it may be... 

Figure 15.10 Porosity as a function of solid compressive pressure in the fouling layer formed in the dead-end microfiltration under AP — 6 kPa for 0.5% cross-linked S. cerevisiae suspension.

Dead-ended filtration of fermentation broth is complicated by the problem of low porosity and compressibility of the accumulated solids, which results in gradually decreasing permeability during the filtration cycle. With compressible solids, an increase in the differential pressure across the membrane can actually lead to a reduced permeation rate. This problem can be reduced by the use of fitter aids added to the broth and onto the filter paper as a precoat. The two most widely used filter aids are the diatomaceous earths and the perlites. 

In most spectroscopic studies, the solids to be studied are usually compressed to form pellets under pressures around 1.5-2 kbar. From an academic point of view, the stability of MTS towards pressure is very important, since most spectroscopic studies of lattice groups or adsorbed probes might be affected by a degradation of MTS during compression. For industrial applications compaction is crucial to handle the powder. Thus the mechanical properties of MTS are a very sensitive topic if we think about the future of these materials. Solids with such high porosity and small wall thickness are very likely to be crushed. Previous studies point out a very weak mechanical strength of MTS [3,4J which can jeopardize further industrial development. It has been demonstrated that these materials have the lowest mechanical stability among the... 

For many gases such as methane the room temperature is well above their critical temperature, therefore they are in a supercritical state, i.e. they cannot be condensed into the liquid state at any pressure. While concentration for the storage and conveyance of natural gas (of which methane is the main constituent) at room temperature requires compression at high pressure (CNG method), the ANG method, which makes use of solid adsorbents, is viable even at low gas pressures (Fig. 3.4.7) Because high efficiency depends on a uniform microporous structure with high porosity, the designable, crystalline metal complex was considered to be a very promising exotic material. 

Cake compressibility is the ability of a cake to reduce its volume, i.e., porosity, when stress is applied. The resulting cake will display an increase in hydraulic resistance. This is not necessarily caused by an average change in porosity, as a porosity gradient can occur by the redistribution of the solid material. Rigid granular particles tend to be incompressible and filter well even with thick cakes. Materials that are easily deformed such as amorphous or thixotropic materials will respond well to mechanical pressure or operation with thin cakes. (See Ch. 6 on Cake Compressibility.)... 

Volume porosity. This is the ratio of the total void volume to the total apparent volume, expressed as a percentage. The apparent volume is obtained by multiplying the sample area by the thickness measured at a specified pressure. The void volume is that portion of the apparent volume which is not occupied by the solids used to make the separator, and is usually determined by subtracting the volume of the solids from the apparent volume. The volume porosity of the AGM in the compressed state limits the maximum amount of acid between the plates. Determination of the volume porosity requires knowledge of the thickness, basis weight, and average density of the solids in the sample. 

Unfortunately the use of such a relation other than illustrating first principles is extremely limited in industrial applications because both the specific area of the particles Sq and the porosity 8 are extremely difficult to characterize when dealing with agglomerated solids that are also compressible. A more useful analysis can be made to characterize the filterability of a slurry by the use of the filtration equation as defined by equation (2) below, that shows how the filtration rate is affected by the filter operating parameters (pressure drop AP, filtration area A, filter medium resistance and also slurry related parameters (viscosity p, solids concentration w, specific cake resistance rj ... 

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