Role of Column Design

Meehan, E., and O Donohue, S. J. (1992). The Role of Column and Media Design in the SEC Characterisation of High Molecular Weight Polymers. Presented at ISPAC 5, Inuyama, Japan. 

E. Meehan, S. O Donohue, The role of column and media design in the SEC characterisation of high molecular weight polymers, presented at ISP AC 5, Inuyama, Japan, 1992. 

Extraction, a unit operation, is a complex and rapidly developing subject area (1,2). The chemistry of extraction and extractants has been comprehensively described (3,4). The main advantage of solvent extraction as an industrial process Hes in its versatiHty because of the enormous potential choice of solvents and extractants. The industrial appHcation of solvent extraction, including equipment design and operation, is a subject in itself (5). The fundamentals and technology of metal extraction processes have been described (6,7), as has the role of solvent extraction in relation to the overall development and feasibiHty of processes (8). The control of extraction columns has also been discussed (9). 

Equation 4.38 is, of course, essential to design effective TG columns. However, it has a much wider use in aiding our understanding of the role of natural convection in other separation methods. 

The point to note here is the important role of thermodynamics, in that the schematic design of the process to separate the feed mixture into two strearns of specified purity was based completely on vapor-liquid equilibrium. The fact that an azeotrope occurred dictated that the desired separation could not be obtained with a single distillation column. Then how the azeotropic composition changed with temperature was the basis for whether a second column of higher or lower pressure should be used. This example is just one illustration of the very central role of thermodynamics in general, and vapor-liquid equilibrium in particular, in the design of separations processes in chemi-. cal engineering. 

The ethanol column (C-1) has practically only stripping zone. Fig. 9.31-left shows composition profile both for liquid and vapour phase. The examination of the composition profiles highlights the role of the entrainer. In the zone close to the top the benzene extracts the ethanol in the liquid phase, and as a result increases the volatility of water, so that on lower stages the water is completely removed. In the lower part practically only the binary ethanol/benzene remains. The distillation trajectory starts from the ternary azeotrope, goes along the ethanol/ benzene saddle and terminates in the ethanol vertex. Because the boiling point of the azeotrope ethanol-water is close to the pure ethanol, the profile could easily jump to the ethanol/water azeotrope. Consequently, the design and operation of the column (C-1) is very sensitive. 

With a saturated design of n runs we can study up to n-1 factors, but it is advisable to choose a smaller number. The columns not used to set the factor levels then play the roles of inert factors and can be used to estimate the error associated with the contrasts. For Plackett-Burman... 

There are several other contributions to this term. A fairly common one is associated with the distribution of the sample over the cross section of the column and the collection of the band at the column outlet. This may especially play a role with large-diameter columns or more specifically with columns of low aspect ratio (ratio of column length to column diameter). In this case, distributors are needed to distribute the flow and the sample evenly over the entire cross section. We will discuss column design in Chapter 3. 

Thorat BN, Kulkami AV, Joshi JB (2001) Design of sieve plate spargers for bubble columns role of weeping. Chem. Eng. TechnoL, 24 841-828. 

The appearance of Keuleman s book made the van Deemter equation (published by a physicist in a chemical engineering journal ) much better known to chemists. As a result this paper has been cited many times (more than 370 between 1961 and 1980 alone) the author himself attributed this to the fact that the equation describes in a simple and intuitive way (that nonetheless can be expressed mathematically to permit quantitative evaluation) the role of the main design parameters of the chromatographic column. In 1978 van Deemter was one of the scientists honored by the Academy of Sciences of the USSR by presentation of a memorial medal celebrating the 75th anniversary of the discovery of chromatography by M.S. TswetL... 

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