Separation density variation

Variations in Properties of Coal Macerals Elucidated by Density Gradient Separation... 

The observed changes in density are related in a complex way to the chemical structure of the coal or maceral (3). In order to better understand the chemical variations occurring in coal macerals we have examined the ultimate analysis of selected density fractions separated from the same coal. 

Here, a is the lattice unit dimension, M is the number of lattice units per clay platelet (so that the product Ma2 = A is the total area of the platelet), a is the grafting density of "surfactants," Xa/3 are the Flory-Huggins parameters between species a and (3, //, is the chemical potential of the zth component, and 0, is the excess amount of the zth component in the system. The density profiles of various species, a(z), and conjugate fields, ua(z), are calculated as described below. Note that we introduce a separate species and component—voids (denoted as subscript v)—to account for density variation within the gallery. 

Other physical properties of the sulfur-polysulfide melt influence cell performance and have been studied. Density is perhaps foremost among these since density variation during discharge will dictate cathode void volume requirements. Furthermore since the sulfur-polysulfide melt is a two-phase system (see Figure 2) over much of the discharge range, density in conjunction with viscosity and surface tension establish the nature of the phase separation. Measurements of density (19, 23) demonstrate that the reaction proceeds at 360°C according to ... 

In pressure agglomeration, lubricants also reduce the coefficient of friction between the material to be compacted and the tooling. This results in a more uniform structure of the compact and in less density variation (see also Section 8.2). During ejection from a die or release from a mold lower forces are required for separation and, therefore, higher survival rates are obtained. 

Fig. 1. Schematic representation of (a) nematic, (b) smectic and (c) cholesteric (or chiral nematic) liquid crystalline phases. In the nematic phase only orientational correlations are present with a mean alignment in the direction of the director n. In the smectic phase there are additional layer-like correlations between the molecules in planes perpendicular to the director. The planes, drawn as broken lines, are in reality due to density variations in the direction of the director. The interplane separation then corresponds to the period of these density waves. In the cholesteric phase the molecules lie in planes (defined by broken lines) twisted with respect to each other. Since the molecules in one plane exhibit nematic-like order with a mean alignment defined by the director n, the director traces out a right- or left-handed helix on translation through the cholesteric medium in a direction perpendicular to the planes. When the period of this helix is of the order of the wavelength of light, the cholesteric phase exhibits bright Bragg-like reflections. In these illustrations the space between the molecules (drawn as ellipsoids for simplicity) will be filled with the alkyl chains, etc., to give a fairly high packing...

In a fluid containing dispersed colloids, there will be competing forces acting on the particles. Gravity promotes separation of the particles from the solution by density variation, and interparticle forces promote either aggregation or dispersion. 

Hot-Water Process. The hot-water process is the only successflil commercial process to be appHed to bitumen recovery from mined tar sands in North America as of 1997 (2). The process utilizes linear and nonlinear variations of bitumen density and water density, respectively, with temperature so that the bitumen that is heavier than water at room temperature becomes lighter than water at 80°C. Surface-active materials in tar sand also contribute to the process (2). The essentials of the hot-water process involve conditioning, separation, and scavenging (Fig. 9). 

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