(486n) Design Methodology for the Fully Thermally Coupled Distillation System with Postfractionator

A thermally coupled distillation column with postfractionator (FTCDCP) has been studied in recent years(1) as an alternative to solve the mismatch in composition of the interlinking trays of the Petlyuk column, and to improve its thermodynamic efficiency. In a previous work(2), the Underwood′s equation was developed to calculate the minimum vapor flowrate for FTCDCP systems, using a McCabe-Thiele analysis to fix flowrates and composition values for the postfractionator interlinking streams. However, because the extra degrees of freedom, there are several variables (interlinking streams between the Prefractionator and the main column, interlinking streams between the Postfractionator and the main column, and compositions or recoveries of such interlinking streams) that can be used to formulate an optimization problem. This work presents a design methodology for the FTCDCP structure, using the Boundary Value Design Method(3) to compute the number and distribution of stages, and a preliminary optimization procedure to minimize the energy duty. An application of the design method to a case study is presented. The results are compared to the behavior of the original Petlyuk system.

1. Kim, Y. H., (2006). A New Fully Thermally Coupled Distillation Column with Postfractionator, Chemical Engineering and Processing, 45, 254-263.

2. Ruíz,M. L. E., Castro, A. A., Ramírez,C. N., Jiménez,G. A., (2008). Analysis of Minimum Vapor Flowrate Requirements for the Fully Thermally Coupled Distillation System with Postfractionator, Presented at 2008 AIChE Annual Meeting, paper 578n.

3. Doherty, M.F., Malone, M.F, (2001). Conceptual Design of Distillation System, McGraw-Hill.