Column construction

One of the most important advances in column construction has been the development of open tubular, or capillary columns that contain no packing material (dp = 0). Instead, the interior wall of a capillary column is coated with a thin film of the stationary phase. The absence of packing material means that the mobile phase... 

A third parameter to consider is the column construction. Thus the sample applicator should provide optimal sample application to give the most performance possible out of the packed bed. Constructions should also allow simple, fast, and reproducible packing of the column. Because costs for repacking of columns are a substantial operating cost item in industrial chromatography, the selection of column construction from this point of view is also important. Some novel column constructions allow very simple procedures both for laboratory and for industrial scale (e.g., INdEX columns, see Section V). 

In some cases the column construction used does not support a movable adapter, e.g., the popular stack column (see Section V) where a stable bed is achieved by shrinking the gel slightly in an ethanol-water mixture prior to packing. After the column is packed and the column has been closed the gel is allowed to expand by equilibrating the column in distilled water. 

The exact treatment yields expressions which have the same form as the expressions given above only the numerical factors are different. The more detailed theory for the diffusion-convection problem between plane walls was developed by Furry, Jones, and Onsager (F10) and that for the column constructed from two concentric cylinders by Furry and Jones (Fll). Recently more attention has been given to the r61e of the temperature dependence of the transport coefficients in column operation (B9, S15). 

Both modes usually are conducted with constant vaporization rate at an optimum value for the particular type of column construction. Figure 13.10 represents these modes on McCabe-Thiele diagrams. Small scale distillations often are controlled... 

Butanol, used as a solvent in an autoclave preparation at around 100°C, severely attacked the aluminium gasket, liberating hydrogen which caused a sharp rise in pressure. Other alcohols would behave similarly, forming the aluminium alkoxide [1]. On a larger scale, a distillation column, constructed in aluminium by chemical engineers who neglected chemistry, fell apart within 24 hours of start-up [2]. 

Because diffusion dominates the transport of contaminants in barriers and columns constructed of low-permeability materials, model calibrations and predictions are extremely sensitive to the form of the specified boundary conditions. Two issues are of particular importance 1) treatment of the entrance mixing zone in laboratory columns, and 2) specification of appropriate BCs to represent a slurry wall under field conditions. 

Using the following input summary for RADFRAC columns, construct the temperature-enthalpy, stage-enthalpy curves, and the stage-exergy loss profiles for each columns and assess the thermodynamic performance of the columns ... 

The density was measured at room temperature using a density gradient column constructed from toluene and carbon tetrachloride. The column was prepared according to ASTM-D 1505 Method B. The column was calibrated with glass floats of known density. The accuracy of density measurements was estimated to be 0.001 g/cm Small pieces ( 25 mm ) were placed in the column and allowed to equilibrate before the measurements were taken. 

Both modes usually are conducted with constant vaporization rate at an optimum value for the particular type of column construction. Figure 13.9 represents these modes on McCabe-Thiele diagrams. Small scale distillations often are controlled manually, but an automatic control scheme is shown in Figure 13.9(c). Constant overhead composition can be assured by control of temperature or directly of composition at the top of the column. Constant reflux is assured by flow control on that stream. Sometimes there is an advantage in operating at several different reflux rates at different times during the process, particularly with multicomponent mixtures as on Figure 13.10. 

In chap 8 the basic bubble column constructions and the principles of operation of these reactors are described. The classical models for two- and three phase simple bubble column reactors are defined based on heat and species mass balances. The state of the art on fluid djmamic modeling of bubble column reactors is then summarized including a few simulations of reactive flows. 

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