Bulk density definition

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

For porous solids such as coal, there are five different density measurements true density, apparent density, particle density, bulk density, and in-place density. The true density of coal is the mass divided by the volume occupied by the actual, pore-free solid in coal. However, determining mass of coal may be deemed as being rather straightforward, but determining volume presents some difficulties. Volume, as the word pertains to a solid, cannot be expressed universally in a simple definition. Indeed, the method used to determine volume experimentally, and subsequently, the density, must be one that applies measurement rules consistent with the adopted definition. 

Example 10.9 used two different definitions of the catalyst density and at least two more definitions are in common usage. The value pc = 367 refers to the reactor average density. It is quite low in the example because so much of the reactor volume is empty. Normally, the reactor would be packed almost completely, and the reactor average density would approach the bulk density. The bulk density is what would be measured if the catalyst were dumped into a large container and gently shaken. The bulk density is not stated in the example, but it would be about 800 kg/m3 for the catalyst pellets prior to grinding. The catalyst will pack to something less than the bulk density in a small-diameter tube. The pellet density in the example is 1120 kg/m3. It is the mass of a catalyst pellet divided by the external volume of the pellet. The final density is the skeletal density of the pellet. It is the density of the solid support and equals 1120/(1 — 0.505) = 2260 kg/m3 for the example catalyst. The various densities fall in the order... 

In conclusion, definite information on the density of adsorbed interlayer water cannot be derived from the bulk density measurements. However, such measurements supplement adsorption isotherm data, and both will be helpful in the interpretation of x-ray structure analysis of the configuration of water molecules and exchange cations in the interlayer space. 

Based on the definition of density, two new terms are defined. Porosity is defined as the proportion of a powder bed or compact that is occupied by pores and is a measure of the packing efficiency of a powder and relative density is the ratio of the measured bulk density and the true density ... 

Particle behavior is a function of particle size, density, surface area, and shape. These interact in a complex manner to give the total particle behavior pattern [28], The shape of a particle is probably the most difficult characteristic to be determined because there is such diversity in relation to particle shape. However, particle shape is a fundamental factor in powder characterization that will influence important properties such as bulk density, permeability, flowability, coatablility, particle packing arrangements, attrition, and cohesion [33-36], Consequently it is pertinent to the successful manipulation of pharmaceutical powders that an accurate definition of particle shape is obtained prior to powder processing. 

When a liquid or a gas occupies a volume, it may be assumed to fill the volume completely. On the other hand, when solid particles occupy a volume, there are always spaces (voids) among the particles. The porosity or void fraction of a bed of particles is the ratio (void volume)/(totai bed volume). The bulk density of the solids is the ratio (mass of solids)/(iotaI bed volume), and the absolute density of the solids has the usual definition, (mass of solids)/(volume of solids). 

Determination of surface atom density on nanocrystals can be difficult, and imprecise, especially for very small particles that cannot be easily characterized microscopically. Nevertheless, reasonable accuracy can be obtained by using theoretical calculations informed by empirical data. In this work, the CdTe nanocrystals that were prepared (2.5-6 nm diameter) were found to be in the zinc blende crystal structure, allowing the use of the bulk density and interplanar distances of zinc blende CdTe in these calculations. It is likely that a variety of crystalline facets are exposed on individual nanocrystals, each with a range of planar densities of atoms. It is also likely that there is a distribution of different facets exposed across an assembly of nanocrystals. Therefore, one may obtain an effective average number of surface atoms per nanocrystal by averaging the surface densities of commonly exposed facets in zinc blende nanocrystals over the calculated surface area of the nanocrystal. In this work we chose to use the commonly observed (Iff), (100), and (110) zinc blende planes, which are representative of the lattice structure, with both polar and nonpolar surfaces. For this calculation, we defined a surface atom as an atom (either Cd or Te ) located on a nanocrystal facet with one or more unpassivated orbitals. Some facets, such as Cd -terminated 111 faces, have closely underlying Te atoms that are less than 1 A beneath the surface plane. These atoms reside in the voids between Cd atoms, and thus are likely to be sterically accessible from the surface, but because they are completely passivated, they were not included in this definition. 

The bulk density of a powder is obtained by dividing its mass by the bulk volume it occupies. The volume includes the spaces between particles as well as the envelope volumes of the particles themselves. The true density of a material (i.e., the density of the actual solid material) can be obtained with a gas pycnometer. The bulk density of a powder is not a definite number like true density or specific gravity but an indirect measurement of a number of factors, including particle size and size distribution, particle shape, true density, and especially the method of measurement. Although there is no direct linear relationship between the flowability of a powder and its bulk density, the latter is extremely important in determining the capacity of mixers and hoppers and providing an easily obtained valuable characterization of powders. 

Basis of comparison for solids and liquids. Basis of comparison for gases. For discussion of density vs. specific gravity, see specific gravity. Apparent density is the mass of a unit volume of powder, usually expressed in grams per cubic centimeter, determined by a specified method (MPA definition, MPA Standard 9-50T). Bulk density is an alternative term for apparent density. 

The fines content is arbitrarily defined as <10 mm material, instead of <6 mm as with coal. This conservative definition is more inclusive of flaky particles in d-RDF. A low fines content is desired for increased bulk density, improved material flow, and reduced dusting. However, as with coal, some fines are necessary to achieve a mix of suspension and on-the-grate combustion. Table II lists an average fines content somewhat lower than the 20 - 40 wt% range typical of stoker coal. Note that these measurements were taken on the as-produced pellets, and any abuse during transport, storage, and feeding will increase the fines in the fuel as fed to the boiler. However, the pellet mill output can be screened, and the screen underflow returned to the mill, as is done with animal feeds to reduce fines. 

In (F.2), we have used the definition of the singlet molecular distribution function. The last relation holds for a homogenous fluid, where V(S) is the volume of the region S, and p is the the bulk density p = N/V. 

In accordance with the soil properties considered in the case of Pu02 migration a bulk density p = 1.59 g/cm and a porosity p = 0.40 can be assumed. Some difficulty arises when choosing a value for the distribution coefficient Kplutonium exchange going on in soil/water system, the definition of Kh doesn t suit the description of plutonium distribution between soil and water. Assuming, however, that plutonium is tetravalent a distribution coefficient of Kd = 5 103 seems to be a reasonable one (5). Such conditions involve a relative migration velocity of r = 8.4 10 S... 

Kostelnik and Beddow47 suggested and tested a Ro-Tap method for determining tap densities. They argued that, when measuring the tap density to be used in the Hausner ratio (see next section for its definition), its measurement should be consistent with the measurement of aerated bulk density in that it should use the same test cup. They considered the measuring cylinder as inappropriate because the visual determination of volume not only makes it difficult to determine the epd point but makes it impossible to determine the volume accurately enough. 

Example 10.9 used two different definitions of the catalyst density and at least two more definitions are in common usage. The value Pc = 367 refers to the reactor average density. It is quite low in the example because so much of the reactor volume is empty. Normally, the reactor would be packed almost completely, and the reactor average density would approach the bulk density. The bulk density is what would be... 

Porosity and wet bulk density are typical bulk parameters which are directly associated with the relative amount of solid and fluid components in marine sediments. After definition of both parameters this section first describes their traditional analysis method and then focuses on recently developed techniques which determine porosities... 

The traditional way to determine porosity and wet bulk density is based on weight and volume measurements of small sediment samples. Usually they are taken from the centre of a split core by a syringe which has the end cut off and a definite volume of e.g. 10 ml. While weighing can be done very accurately in shore-based laboratories mea-... 

Boyce R.E., 1976. Definitions and laboratory techniques of compressional sound velocity parameters and wet-water content, wet-bulk density, and porosity parameters by gravity and gamma ray attenuation techniques. In Schlanger S.O., Jackson E.D. et al (eds) Initial Reports of the Deep Sea Drilling Project 33, Washington, US Government Printing Office, pp 931-958... 

Spray drying is by definition the transformation of feed from a fluid state into a dried particulate form by spraying the feed into a hot drying medium [Masters, 1985]. This is an ideal process where the end-product must comply with precise quality standards regarding particle size distribution, residual moisture content, bulk density, and particle shape. It involves the atomization of a liquid feedstock into a spray of droplets and contacting the droplets with hot air in a drying chamber. The sprays are produced by either rotary (wheel) or nozzle atomizers. Evaporation of solvent of matrix liquid from the droplets and formation of dry particles proceeds under controlled temperature and air flow conditions. 

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