Available work distillation column

The analysis presented in this chapter is an example of how the principles of thermodynamics can be applied to establish efficiencies in separation units. We have shown how exergy analysis or, equivalently, lost work or availability analysis can be used to pinpoint inefficiencies in a distillation column, which in this case were the temperature-driving forces in the condenser and the reboiler. The data necessary for this analysis can easily be obtained from commonly used flow sheeters, and minimal extra effort is required to compute thermodynamic (exergetic) efficiencies of various process steps. The use of hybrid distillation has the potential to reduce column inefficiencies and reduce the number of trays. We note that for smaller propane-propene separation facilities (less than 5000bbl/day [10]), novel technologies such as adsorption and reactive distillation can be used. 

Most of the work in the estimating process relies on the application of well-established factors to a basic figure of the cost of all of the main items of the plant, as delivered to the site entrance. This figure has thus to be calculated as accurately as possible, based upon the plant design as available at the time of the estimate. It depends upon the identification and rough sizing of the key process plant items (such as reactors, distillation columns, heat exchangers, and so on), and the determination of approximate delivered prices for these items, from charts and other information published in textbooks, journals and on the internet. 

In a distillation column, we supply heat at a higher temperature somce in the reboiler, and then discharge at a lower temperature in the condenser (Figure 4.12). Assuming the column to be a reversible heat engine, the net work available from the thermal energy is (Ognisty, 1995)... 

We have tried to illustrate why chemical processes are thermally inefficient. First, the chemical work available in the reactants is dissipated as heat. Second, the work required for separation is usually supplied as heat to distillation columns, which have internal inefficiencies. Finally,... 

When initially running case studies using a process simulator, you should use any shortcut methods for simulating distillation columns that are available. Avoid the rigorous methods for this type of preliminary work. You may want to use the rigorous (tray-to-tray) methods at the end of your work for the optimized case. 

Available in metal only, usually used In batch and continuous distillation in small diameter columns not exceeding 24-inches dia. High fractionation ability per unit height, best suited for laboratory work. Conical and triangular types available. Not much industrial data available. 

Farnesol was obtained from Fluka AG (Buchs, CH9470, Switzerland) as a mixture of 65% (E), (E)- and 35% (Z), (E)- isomers. It is also available from the Aldrich Chemical Company, Inc. This procedure works equally well with pure (E), (F)-famesol, which may be obtained from the above mixture by careful distillation, at reduced pressure, through a Nester-Faust Teflon spinning-band column. 

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