Hydrocarbon absorbers, optimization

This section is a companion to the section titled Fractionators-Optimization Techniques. In that section the Smith-Brinkley method is recommended for optimization calculations and its use is detailed. This section gives similar equations for simple and reboiled absorbers. 

For a simple absorber the Smith-Brinkley equation is for component i  

B = Bottoms total molar rate, or subscript for bottoms F = Feed total molar rate, or subscript for feed fi = Ratio of the molar rate of component i in the bottoms to that in the feed 

L = Effective total molar liquid rate in top section L = Effective total molar liquid rate in bottom section 

M = Total equilibrium stages below feed stage ineluding reboiler 

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IRRAS spectra of a monolayer of octadecylsiloxane (ODS) on a silicon substrate measured at several incidence angles are shown in Figure 13.18. Also shown in this figure are the spectra that are calculated by assuming that the ODS is present as an all-trans hydrocarbon chain tilted by 10°. Note that only when the spectrum is measured with p-polarized radiation above Brewster s angle is the absorbance positive, as it is for metallic substrates. Under all other conditions, the effect of the adsorbate is to cause the reflectance to increase above the value for the clean substrate. Thus, a knowledge of the optical constants of the substrate is vital if optimal IRRAS spectra of thin Aims on dielectric substrates are to be measured. 

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