THE EFFECTS OF EXTERNAL DISTURBANCES ON THE PERFORMANCE AND CHAOTIC BEHAVIOR OF INDUSTRIAL FCC UNITS

The dynamic behaviour of an industrial Type IV fluid catalytic crackin g for the production of gasoline unit is investigated for a case when the air feed temperature is periodically forced. The investigation con centrates on the behaviour of the system for a case of bistability for the autonomous system with special emphasis on the effect of forcing on the periodic attractor of the autonomous system. When the centre of forcing is very close to the homoclinical termination point of the au tonomous periodic attractor, period-doubling mechanism and Type 1 inte rmittency have been identified as the routes to chaos for this six-dim ensional (6D) system. Chaotic behaviour occurs at very low forcing amp litudes which simulate small disturbances that are unavoidable in the operation of any industrial unit. While in certain ranges of the value s of the forcing amplitudes the output amplitudes of the forced system are higher than their counterparts in the autonomous system, other re gions show the opposite behaviour. Average gasoline yield in the bista bility region for the attractor resulting from the forcing of the auto nomous periodic attractor is much higher than that resulting from forc ing the autonomous static attractor. This yield is very close to that obtained with the optimum steady state which is unstable and requires prohibitively high values of controller gains to be stabilized. (C) 19 97 Elsevier Science Ltd.