The Calculation and Interpretation of Parametric Transfer Functions for Binary Distillation Columns of the Tray Type.

Starting from familiar assumptions for dynamic analysis, a transfer-function-matrix (T.F.M.) model for long, symmetrical, binary distillation columns is derived completely analytically. The model relates twin output composition changes to perturbations in the internal liquid and vapour flow rates. The model is intended for use in controller design and being expressed in terms of "plant parameters" and "operating conditions", should provide useful common ground between control engineer and plant designer. Though derived precisely for a symmetrical plant, it is expected that the model should apply more generally as a good approximation. Experimental data is given supporting this claim. Inverse Nyquist loci are generated in precise and approximate form and shown to compare favourably with computed step responses. The responses accord broadly with previous, part empirical, part numerical research results. The paper is the first of a common pair, the second being devoted to packed-common analysis.