COORDINATED CONTROL OF BLENDING SYSTEMS

Blending is an important unit operation in chemical process industries . Based on Luyben's work, a coordinated control is proposed to overcom e the system interaction and process nonlinearity in blending processe s. Blending systems with ideal and nonideal mixing (by nonideal mixing we mean the blended property is not a linear function of the inlet pr operties) are explored. Furthermore, unusual dynamic behavior is obser ved for blending systems coupled with complex dynamics arisen from the process side. Controlling the blending of streams from different side stream locations of a distillation column is studied and, based on phy sical insight, a simple procedure is proposed for the selection of sid edraw locations. Since, the properties of the inlet streams are often subject to changes and disturbance rejection aspects of blending contr ol are discussed and practically important issues such as model uncert ainties and measurement noise are also treated in a rigorous manner. S imulation results show that the control of blending systems is not as trivial as it was thought and, more importantly, improvement in the pe rformance can be achieved using the proposed coordinated control.