Particles void volume

All commercial carbons have been made for uses other than natural gas storage. They are for the most part granular materials and pack into vessels with a substantial inter-particle void volume which results in low bulk densities. Some... 

For large amounts of fillers, the maximum theoretical loading with known filler particle size distributions can be estimated. This method (8) assumes efficient packing, ie, the voids between particles are occupied by smaller particles and the voids between the smaller particles are occupied by stiH smaller particles. Thus a very wide filler psd results in a minimum void volume or maximum packing. To get from maximum packing to maximum loading, it is only necessary to express the maximum loading in terms of the minimum amount of binder that fills the interstitial voids and becomes adsorbed on the surface of the filler. 

Bulk Density. Bulk density, or the apparent density, refers to the total amount of space or volume occupied by a given mass of dry powder. It includes the volume taken up by the filler particles themselves and the void volume between the particles. A functional property of fillers in one sense, bulk density is also a key factor in the economics of shipping and storing fillers. 

Specific gravity is the most critical of the characteristics in Table 3. It is governed by ash content of the material, is the primary deterrninant of bulk density, along with particle size and shape, and is related to specific heat and other thermal properties. Specific gravity governs the porosity or fractional void volume of the waste material, ie. 

Rapid heating of either borax decahydrate or pentahydrate causes the crystal to dissolve before significant dehydration, and at about 140°C, puffing occurs from rapid vaporisation of water to form particles having as high as 90% void volume and very low bulk density (78). 

Dp = average particle diameter, defined as the diameter of a sphere of the same volume as the particle = void fraclion... 

With closely screened material, the percentage of voids (usually 37 percent) is independent of particle size. With unscreened particles showing a wide variation in size, the void volume is decreaseci irregularity in gas flow results. 

Fig. 12-88. Curve A shows the calculated surface based on an assumed 50 percent void volume and cubical-shaped particles. The B set of cui ves applies to such unscreened irregularly shaped particles as are usually encountered in practice.

A macroporous polystyrene-divinylbenzene copolymer is produced by a suspension polymerization of a mixture of monomers in the presence of water as a precipitant. This is substantially immiscible with the monomer mixture but is solubilized with a monomer mixture by micelle-forming mechanisms in the presence of the surfactant sodium bis(2-ethylhexylsulfosuccinate) (22). The porosity of percentage void volume of macroporous resin particles is related to percentage weight of the composite (50% precipitant, 50% solvent) in the monomer mixture. 

A considerable amount of information has been reported regarding mass transfer between a single fluid phase and solid particles (such as those of spherical and cylindrical shape) forming a fixed bed. A recent review has been presented by Norman (N2). The applicability of such data to calculations regarding trickle-flow processes is, however, questionable, due to the fundamental difference between the liquid flow pattern of a fixed bed with trickle flow and that of a fixed bed in which the entire void volume is occupied by one fluid. 

As noted before, the whole spectrum of particle sizes between 38 and 357 nm is encompassed with a AV of U.O ml or about 6% of the total column void volume. This low capacity of the HDC system is counterbalanced by its excellent resolution both of itself and in comparison to porous packing systems. The latter point is addressed in the next section. 

In exclusion chromatography, the total volume of mobile phase in the column is the sum of the volume external to the stationary phase particles (the void volume, V0) and the volume within the pores of the particles (the interstitial volume, Vj). Large molecules that are excluded from the pores must have a retention volume VQ, small molecules that can completely permeate the porous network will have a retention volume of (Vo + Fj). Molecules of intermediate size that can enter some, but not all of the pore space will have a retention volume between VQ and (V0 + Fj). Provided that exclusion is the only separation mechanism (ie no adsorption, partition or ion-exchange), the entire sample must elute between these two volume limits. 

To develop analytical models for processes employing porous catalysts it is necessary to make certain assumptions about the geometry of the catalyst pores. A variety of assumptions are possible, and Thomas and Thomas (15) have discussed some of these. The simplest model assumes that the pores are cylindrical and are not interconnected. Develop expressions for the average pore radius (r), the average pore length (L), and the number of pores per particle (np) in terms of parameters that can be measured in the laboratory [i.e., the apparent particle dimensions, the void volume per gram (Vg), and the surface area per gram (Sg). ... 

We will start by developing an expression for the average pore radius T. If we denote the mass of an individual catalyst particle by raP, simple geometric considerations indicate that the void volume per particle is given by... 

Vq is the void volume per gram of catalyst Sq is the surface area per gram of catalyst Vp is the gross volume of the catalyst particle Sx is the gross exterior surface area of the particle ... 

Geometrical factors - structure, void volume and porosity will affect the filler s ability to be wetted by the rubber into which it is incorporated. The shape of the particle will depend on the crystal structure of the mineral being used. 

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