Density skeletal

Note that the soHds density used ia this equation should be the tme soHds, ie, skeletal, density, because the gas ia the pores is also compressed. For Group A soHds the aeration gas should also be added evenly along the standpipe. 

The skeletal density p, of a particle (or crystalline density for a pure chemical compound) is given in terms of internal porosity p by... 

The skeletal density, p, also called the true density, is defined as the density of a single particle excluding the pores. That is, it is the density of the skeleton of the particle if the particle is porous. For nonporous materials, skeletal and particle densities are equivalent. For porous particles, skeletal densities are higher than the particle density. 

Particle and skeletal densities are related through the following expression ... 

The pore volume of a material is 30 % and its particle density is 1.3 g/cm Calculate the skeletal density of the material. 

Catalyst skeletal density Catalyst flowing density Stripper operating pressure Stripper operating temperature Catalyst circulation rate... 

Skeletal Density—SD. The actual density of the pure solid materials that make up the individual catalyst particles. For an FCC catalyst, the skeletal density can be calculated as follows ... 

Skeletal Density is the actual density of the pure solid materials that make up individual particles. 

Porosity Calculated from dimensions, basis wt., and skeletal density ... 

True or skeletal density, p. which is the mass, m, divided by the volume, V, of the solid excluding open and closed pores... 

P. B. Mack68 has made an extensive and very careful study which is related to the problem of variability in bone composition, and she has been kind enough to furnish me with some of the data previous to publication. A wide range of human subjects of various ages, 10,200 in number, were studied by a technique developed by her and her associates for determining skeletal density.69 These determinations are based upon microdensitometric traces which were made of X rays of a cross section 1 mm. wide of the os calcis (heel bone). 

Porosity of a separator is defined as the ratio of void volume to apparent geometric volume. It is usually calculated (eq 6) from the skeletal density, basis weight, and dimensions of the material and so may not reflect the accessible porosity of the material. 

The pore diameter on the abscissa is calculated by employing a particular pore model, usually to the intrusion branch. As a matter of convenience, a cylindrical pore model is traditionally applied. On the ordinate, steep changes in the cumulative diagram are reflected as peak maxima in the incremental curve. From several possible representations (incremental, differential, log differential), the log differential plot seems to be the most revealing, since the areas under the peaks are proportional to the pore volume [79]. Data that can easily derived from mercury intrusion are the pore size distribution, median or average pore size, pore volume, pore area, bulk and skeletal density, and porosity. 

A porous particle contains many interior voids known as open or closed pores. A pore is characterized as open when it is connected to the exterior surface of the particle, whereas a pore is closed (or blind) when it is inaccessible from the surface. So, a fluid flowing around a particle can see an open pore, but not a closed one. There are several densities used in the literature and therefore one has to know which density is being referred to (Table 3.15). True density may be defined as the mass of a powder or particle divided by its volume excluding all pores and voids. True density is also referred to as absolute density or crystalline density in the case of pure compounds. However, this density is very difficult to be determined and can be calculated only through X-ray or neutron diffraction analysis of single-crystal samples. Particle density is defined as the mass of a particle divided by its hydrodynamic volume. The hydrodynamic volume includes the volume of all the open and closed pores. Practically, the hydrodynamic volume is identified with the volume included by the outer surface of the particle. The particle density is also called apparent or envelope density. The term skeletal density is also used. The skeletal density of a porous particle is higher than the particle one, since it is the mass of the particle divided by the volume of solid material making up the particle. In this volume, the closed pores volume is included. The interrelationship between these two types of density is as follows (ASTM, 1994 BSI, 1991) ... 

To highlight the difference from the classical Stoke s equation, the density difference in the latter is (ps—pt), where ps is the skeletal density of the rigid particle. Now, it is easy to illustrate the analogy to a porous particle. A porous particle can be viewed as an aggregate,... 

One of the most important properties of a material is its density, for which there are several expressions, namely, bulk, particle, and skeletal densities. The bulk density of solids is the overall density of the material including the interparticle distance of separation. It is defined as the overall mass of the material per unit volume, which can be determined by simply pouring a preweighed sample of particles into a graduated cylinder and measuring the volume occupied. The material can become denser with time and settling, and its bulk density reaches a certain limiting value, known as the tapped or packed bulk density. 

Catalytic activity, assessed by cumene cracking on separated fractions and also by analysis of residual coke on catalyst fractions, shows a sharp decline with increasing density (age). This rapid loss of initial activity coincides with zeolite dealumination which is largely completed as a slow rate of zeolite destruction is established. Subsequent loss of crystallinity has little additional effect on activity. The associated loss of microporosity leads to an apparent increase in skeletal density with increasing age. 

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