CACE-1995: BACK-OFF CALCULATIONS IN OPTIMISING CONTROL: A DYNAMIC APPROACH

P. BAHRI; A. BANDONI; P. BARTON; J. ROMAGNOLI

COMPUTERS AND CHEMICAL ENGINEERING

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1995 vol. 19 p. 699 - 708

0098-1354

The ultimate goal in the operation of chemical plants is to work at the possible optimal conditions. However, most of the time, a plant is faced with uncertain conditions during its operation. To efficiently handIe these uncertaintics, chemical plants must have the flexibility to achieve feasible operation over a range of uncertain conditions. One way to accomplish this, is by moving the nominal optimum to some permanently feasible operating point inside the feasible region (back-off point). In a previous study (Bahri et al. , 1994). an itcrativc approach to solve this problem at steady-state has been proposed (Steady State Open-Loop Back-Off Calculation). In order lo consider the transient behaviour of a system responding lo disturbances, the back-off calculation should be based upon a dynamic model of the system. Having determined the economic penalty associated with the dynamic open-loop back-off, the next step is to estimate the polential recovery that various control schemes of varying complexity might provide. The methodology to solve the Dynamic Back-Off problem and a flowsheet example are presented in this paper.