Permeability, particle size distribution

All packing materials produced at PSS are tested for all relevant properties. This includes physical tests (e.g., pressure stability, temperature stability, permeability, particle size distribution, porosity) as well as chromatographic tests using packed columns (plate count, resolution, peak symmetry, calibration curves). PSS uses inverse SEC methodology (26,27) to determine chromatographic-active sorbent properties such as surface area, pore volume, average pore size, and pore size distribution. Table 9.10 shows details on inverse SEC tests on PSS SDV sorbent as an example. Pig. 9.10 shows the dependence... 

Deterrnination of the specific surface area can be made by a variety of adsorption measurements or by air-permeability deterrninations. It is customary to calculate average particle size from the values of specific surface by making assumptions regarding particle size distribution and particle shape, ie, assume it is spherical. 

Also, it seems that most of these properties are interdependent. For example, deaeration and permeability (Mainwaring and Reed, 1987) and perhaps the bulk density ratio (Jones and Mills, 1989) seem to provide an adequate mechanism to detect changes in material performance due to different particle size distribution, density and/or shape. However, possibly the greatest disadvantage or limitation of these empirical techniques is the need to standardize the experimental apparatus and techniques. For exam-... 

PK-Map and PK-Sim (Bayer Technology Services, Wuppertal, Germany), that are based on the models described by Willman et al. [54], In these software packages, the intestinal permeability coefficient can be calculated using a compound s lipophilicity and molecular weight [52,54] and hence, no experimental permeability data is needed. Different to the model described by Willman et al. [54], the commercial prediction tools model the dissolution rate taking the particle size distribution of the solid particles into account (www.pk-sim.com). 

In practice, we have a number of solid fuels, for example biofuels (forest or agricultural derived biofuels), coal, municipal solid waste (MSW) and many others [23]. A fuel bed is composed of varying sizes of solid-fuel particles, also called polydispersed solid-.fuels [15]. The fuel chemistry is different depending on whether it is coal, biofuel or MSW. The fuel bed can be dry or consist of moisture. The fuel physics are for example, particle size distribution, particle shape, particle density and bed permeability. 

The Biopharmaceutics Classification System (BCS)3 defines four classes of compounds based upon solubility and permeability. Particle size and size distribution... 

Particle Surface Area Determination Methods From the standard definitions of particle surface area, it can be seen that various determination methods are used for surface area measurement, such as adsorption (including Langmuir s equation for monolayer adsorption and the BET equation for multilayer adsorption), particle size distribution, and permeability methods. The different methods are rarely in agreement because the value obtained depends upon the procedures used and also on the assumptions made in the theory relating the surface area to the phenomena measured. The most common methods used for measuring particle surface area are described below. 

Bentonite rocks have many uses in the chemical and oil industries and also in agriculture and environmental protection. The usefulness of bentonite for each of these applications is based on its interfacial properties. These properties are determined by geological origin, chemical and mineral composition (especially montmorillonite content), and particle size distribution, and they include the specific surface area (internal and external), cation-exchange capacity (CEC), acid-base properties of the edge sites, viscosity, swelling, water permeability, adsorption of different substances, and migration rate of soluble substances in bentonite clay. 

This data collected for determination of the Knox parameters can also be used to establish the linearity of the pressure versus linear velocity curve to evaluate compression of the bed. Lastly, these data can be used to estimate the effective particle size from the pressure drop. The pressure drop data are aseful to assess the effective particle size with the vendors nominal particle size and particle size distribution data. Calculation of the effective particle size is given by Eq. (7.9), where dp is the particle size in cm, u is the linear velocity in cm/s, p is the viscosity in cP, L is the bed length in cm, k[) is the column permeability (e.g. 1 x 10 for irregular particles and 1.2 x 10 for spherical), and AP is the pressure in psi. 

Both porosity and permeability are influenced by the particle size distribution. A high porosity is secured... 

A more realistic model described above to predict the sorption properties in such systems is currently developed to predict also permeability, given the porosity and the spheroidal particle size distribution. 

If the particle-size distribution and particle shape remain the same, a change in absolute particle size does not affect porosity but influences the pore size substantially and thus also the permeability of the body for gases and liquids (cf. Chapter IV, Section 7.2). 

Geometry of the body of sulfidic material Particle-size distribution Permeability to water and gases Thermal conductivity and heat capacity... 

Mass Transfer Properties. The particle size distribution of Interest In medical devices Is extremely wide, ranging from urea and electrolytes (<1 nm diameter) In hemodialysis to platelets and red cells (3 to 8 ym diameter) In plasmapheresis. Between these extremes, molecular size ranges can be defined that roughly delineate filters suitable for hemodialysis and hemofiltration (that Is, Impermeable to albumin), protein separation (that Is, albumin permeable, IgM Impermeable) and microfiltration (that Is, retentive to platelets and red cells). The lower end of these size distributions Is Indicated In Figure 1. 

The particle size distribution should be as narrow as possible (with a ratio of diameters of the smallest and the largest particles of 1 1.5 or 1 2, as already mentioned). This is because the smallest particles determine the column permeability and the largest particles fix the plate number. Small particles produce a high flow resistance and large particles are responsible for a high degree of band broadening. For this reason, a particle size analysis accompanies many products. 

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