Bilinear identification of a binary distillation column (1986)
Type of ContentTheses / Dissertations
Thesis DisciplineChemical Engineering
Degree NameDoctor of Philosophy
PublisherUniversity of Canterbury. Chemical and Process Engineering
AuthorsJanssen, P. W. M.show all
Low order bilinear models of chemical processes, suitable for control applications over a wide operating region, were identified. A case study on a simulated heated tank system showed that there was considerable potential for the use of bilinear models for chemical processes in which mass or energy balance equations have a bilinear structure. Bilinear models were more accurate than linear models at fitting the simulated system's behaviour over a wide range of operating points. The U-D identification algorithm used, proved to be both robust and reliable. Multi-input multi-output bilinear models of both a simulated and an experimental binary distillation column were identified using the U-D algorithm. Two factors affected the trend in the column parameters; the turn-down of the column and the shifting of the composition profile along the column. The bilinear models were good at following changes due to the turn-down, but not the large fluctuations due to changes in the composition profile. This limitation was due to the simplified liquid/vapour equilibrium relation inherent in the bilinear model, which was invalid if there were large fluctuations in composition on any of the plates.