Computer simulation of a separation

Figure 18.15 Optimization of gradient runtime and temperature [after J.W. Dolan etal., J. Chromatogr. A, 803,1 (1998)]. Conditions sample, algal pigments column, 25cm x 3.2 mm i.d. stationary phase, Vydac 201tp Ci8 5 j,m mobile phase, 0.65 ml min gradient from 70 to 100% methanol in 28 mM tetrabutylammonium acetate buffer pH 7.1. Top computer simulation of a separation at 57 C and 80 min gradient runtime middle computer simulation with three fused peak pairs at 55 °C and 54 min bottom experimental chromatogram underthese conditions.

Taylor, R., H.A. Kooijman, and J.S. Hung, A second generation nonequilibrium model for computer simulation of multicomponent separation processes. Computers Chemical Engineering, 1994, 18(3) 205 217. 

Guiochon, G and Ghodbane, S., Computer-simulation of the separation of a 2-component mixtme in preparative scale Uquid-chromatogiaphy, J. Phys. Chem., 92, 3682,1988. 

A computer simulation of a thermal cracker fractionator pumparound section based on equilibrium flash vaporization calculations shows that the heat-transfer coefficient for a theoretical separation stage was 1,600 BTU/hr/ft /°F. On this basis, the height equivalent to a theoretical stage of packing, such as the Flexipac type 4 in section 3 (see Table 8-3), is ... 

E. Barth, M. Mandziuk, and T. Schlick. A separating framework for increasing the timestep in molecular dynamics. In W. F. van Gunsteren, P. K. Weiner, and A. J. Wilkinson, editors. Computer Simulation of Biomolecular Systems Theoretical and Experimental Applications, volume III, chapter 4, pages 97-121. ESCOM, Leiden, The Netherlands, 1997. 

No additional hardware in the form of a separate simulation computer is necessary. 

L. M. Martiouchev, V. D. Seleznev, S. A. Skopinov. Computer simulation of nonequilibrium growth of crystals in a two-dimensional medium with a phase-separating impurity. J Stat Phys 90 1413, 1998. 

This review paper is restricted to stirred vessels operated in the turbulent-flow regime and exploited for various physical operations and chemical processes. The developments in the field of computational simulations of stirred vessels, however, are not separated from similar developments in the fields of, e.g., turbulent combustion, flames, jets and sprays, tubular reactors, and multiphase reactors and separators. Fortunately, there is a strong degree of synergy and mutual cross-fertilization between these various fields. This review paper focuses on aspects specific to stirred vessels (such as the revolving impeller, the resulting strong spatial variations in turbulence properties, and the macroinstabilities) and on the processes carried out in them. 

In addition, the measurements are rapid and simple, and are now even used in 100% inspection for quality control of multiple-layer semiconductors. An example is shown in Figure 1.6. This is a GaAs substrate with a ternary layer and a thin cap. The mismatch between the layer and the substrate is obtained immediately from the separation between the peaks, and more subtle details may be interpreted with the aid of computer simulation of the rocking curve. This curve can be obtained in a matter of minutes. Routine analysis of such curves gives the composition of ternary epilayers, periods of superlattices and thicknesses of layers, whilst more advanced analysis can give a complete strain and composition profile as a lunction of depth. 

Such a time scale separation between system and bath may often be appropriate when dealing with intramolecular vibrational motions of molecules but is likely never appropriate for electronic transitions in solution near room temperature. In the past 10 years much effort has been devoted to dynamical aspects of the solvation process in polar liquids utilizing experiments [2-4], theory [5, 6], and computer simulations of molecular dynamics [7-10]. The... 

In general, distillation columns should be operated at a low pressure. For example, Fig. 3.3 shows an isobutane-normal butane stripper. This fractionator is performing poorly. A computer simulation of the column has been built. The column has 50 actual trays. But in order to force the computer model to match existing operating parameters (reflux rate, product compositions), 10 theoretical separation stages (i.e., 10 trays, each 100 percent efficient) must be used in the model. This means that the trays are developing an actual tray efficiency of only 20 percent. 

R. C. Chloupek, W. S. Hancock, and L. R. Synder, Computer simulation as a tool for the rapid optimization of the HPLC separation of a tryptic digest of human growth hormone, J. Chromatogr., 594 65 (1992). 

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