MU-OPTIMAL LV-CONTROL OF DISTILLATION-COLUMNS

Two-point composition control using the LV-configuration is examined. In spite of high steady-state RGA-values it is shown for seven example columns that the LV-configuration may yield acceptable robust performance using single-loop controllers provided measurement delays are not too large. In order to investigate the level of modelling detail that is required for effective control, five process models of different complexity are studied. It is demonstrated that flow dynamics should be included in a column model which is to be used for controller design. The structured singular value (Mu or μ) is used as a robust performance index. To use this index one must define performance using the H∞ framework. The issue of selection of performance and uncertainty weights is critical in this procedure, and is discussed in detail in the paper. © 1990.