Normal separation principles

Separation in these devices known as winnowing machines [3], is achieved due to the difference between trajectories of coarse and fine particles in the separation zone (Fig. lb). Their operation and efficiency are strongly affected by the stochastic factors of the process, in particular by uncertainties in feeding and particles aerodynamic interactions. In most cases coarse particles prevent proper classification of fines. Separation efficiency of these devices is usually low. They are normally used for separation of solid particles according to densities (e.g. grain from peel), rather than by size. Sometimes crossflow separation in horizontal streams is used in combination with other separation principles. 

There are two ways to classify liquid chromatographic methods. The first and more common classification is based on the mechanism of retention, and from this the chromatographic modes discussed in Chapter 2 are derived. For example, the normal-phase mode can be performed by taking advantage of either the adsorption mechanism or the partition mechanism. The gel-filtration mode is performed using the mechanism of size exclusion. The second classification discussed below is based on the separation principle and is found mostly in the literature published before the 1990s. 

A depropanizer example is provided to illustrate the use of Aspen IPE. The depropanizer is a distillation tower to recover propane and lighter species from a normal-paraffins stream, as shown in Figure 1. The simulation flowsheet and selected results are shown in Appendix I and in the multimedia tutorial on the CD-ROM that contains these course notes ASPEN Tutorials —> Separation Principles -> Flash and Distillation). Also, a copy of the file, RADFRAC.bkp, is provided on the CD-ROM. 

We can immediately discern from Figure 5.11 that the molecule is divided into two clearly separated domains that seem to be of similar size. For the next step we would need a stereopicture of the model or, much better, a graphics display where we could manipulate the model and look at it from different viewpoints. Here instead we have made a schematic diagram of one domain (Figure 5.12), which is normally not done until the analysis is completed and the structural principles are clear. 

In X-Ray Fluorescence (XRF), an X-ray beam is used to irradiate a specimen, and the emitted fluorescent X rays are analyzed with a crystal spectrometer and scintillation or proportional counter. The fluorescent radiation normally is diffracted by a crystal at different angles to separate the X-ray wavelengths and therefore to identify the elements concentrations are determined from the peak intensities. For thin films XRF intensity-composition-thickness equations derived from first principles are used for the precision determination of composition and thickness. This can be done also for each individual layer of multiple-layer films. 

EN 779 1993 in principle contains two different test methods. The filter is tested both with untreated outdoor air and with the addition of synthetic dust. In the first case, the filter s dust spot efficiency is determined, i.e., its capacity to clean normal outdoor air. In the second case, the filter s arrestance is measured, i.e., its capacity to separate synthetic dust. The average value for dust spot efficiency or arrestance during the course of the test is used for classification of the filter. 

On the basis of the principle of grafted TLC, reversed-phase (RP) and normal-phase (NP) stationary phases can also be coupled. The sample to be separated must be applied to the first (2.5 cm X 20 cm) reversed-phase plate (Figure 8.16(a)). After development with the appropriate (5ti 5yi) mobile phase (Figure 8.16(b)), the first plate must be dried. The second (20 cm X 20 cm) (silica gel) plate (Figure 8.16(c)) must be clamped to the first (reversed-phase) plate in such a way that by use of a strong solvent system (Sj/, SyJ the separated compounds can be transferred to the second plate (Figure 8.16(d)). Figure 8.16(e) illustrates the applied, re-concentrated... 

An alternative method of purifying water is by reverse osmosis. Under normal conditions, if an aqueous solution is separated by a semi-permeable membrane from pure water, osmosis will lead to water entering the solution to dilute it. If, however, sufficient pressure is applied to the solution, i.e. a pressure in excess of its osmotic pressure, then water will flow through the membrane from the solution the process of reverse osmosis is taking place. This principle has been... 

Principles and Characteristics Mass-spectral analysis methods may be either indirect or direct. Indirect mass-spectral analysis usually requires some pretreatment (normally extraction and separation) of the material, to separate the organic additives from the polymers and inorganic fillers. The mass spectrometer is then used as a detector. Direct mass-spectrometric methods have to compete with separation techniques such as GC, LC and SFC that are more commonly used for quantitative analysis of polymer additives. The principal advantage of direct mass-spectrometric examination of compounded polymers (or their extracts) is speed of analysis. However, quite often more information can be... 

An optical flame sensor installed at the beginning of the pipeline is the most suitable device for such an isolation system, since the propagating flame from the explosion has to be detected and extinguished. Pressure detectors alone are, in principle, not suited to the case on hand because there is no distinct separation between the pressure and flame fronts for explosion in pipelines. Optical ir sensors that have a relatively low sensitivity to daylight are normally chosen and have proved themselves amply in industrial practice. Therefore, daylight into the pipe in the vicinity of the sensor must be avoided. It is necessary to flush the optical lens with gas (e.g., nitrogen, air) to keep it dust-free. 

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