Date of Award
Master of Science in Chemical Engineering - (M.S.)
Chemical Engineering and Chemistry
Edward Charles Roche, Jr.
John E. McCormick
A short-cut procedure has been developed for making calculations on a complex fractionation tower. A Simplification of the Thiele-Geddes plate-to-plate procedure provided the basis for the short-cut procedure. The application discussed in this paper is for a tower with a liquid sidestream drawoff in the rectifying section.
The tower was broken at the feed point and sidestream drawoff locations into three calculation sections. The fractionation in each tower section can then be represented by a rigorous series solution expressed in terms of absorption or stripping factors. These rigorous equations can then be simplified by the use of average absorption or stripping factors.
The short-cut procedure has two methods of determining the average stripping or absorption factors for each tower section. The one method uses the assumption of a linear profile of absorption or stripping factors based on end values in each section and is called the Stand-Alone Simplified Thiele-Geddes Method. The other method determines average absorption or stripping factor for each tower section from a force-fit to a rigorous plate-to-plate solution. This method is called the Force-Fit Thiele-Geddes Method and is suitable for accurate parametric studies around a base case rigorous solution.
Computer programs were prepared for the Thiele-Geddes plate-to-plate method and the stand-alone short-cut procedure. In addition, a computer program was written to obtain the force-fit fractions required for the Force-Fit Thiele-Geddes Method. Parametric cases were then run for a five-component debutanizer column, and the results of the short-cut method were compared with the rigorous solution for each case.
The results of these comparisons show the Stand-Alone Simplified Thiele-Geddes Method to be of suitable accuracy for preliminary design calculations. The Force-Fit Thiele-Geddes Method results in a higher degree of accuracy in most cases and is suitable for parametric studies on a final design. The degree of accuracy obtained from the Force-Fit Method is believed to be the highest available from a short-cut procedure.
Prickett, Richard David, "Sidestream tower fractionation : a short-cut calculation method" (1973). Theses. 2025.