Some aspects of integrated process operation

Abstract

Operation and control of integrated processes is considered. Thereby, the aspect of process integration is examined on two levels. On the lower level, different unit operations, like reaction and heat recovery or reaction and separation, are integrated into multifunctional processing units. On the flowsheet level, different processing units are integrated via mass and energy recycles, like the heat integration of distillation columns. On both levels, complex dynamics including periodic and aperiodic oscillations and multiple attractors can arise as a conseqience of strong interaction. For the lower level, nonlinear phenomena are illustrated with two examples. The first example is the so-called circulation loop reactor, which is intended to work as an autonomous periodic system. Second, dynamic operation of a reactive distillation column with multiple steady states is considered. To handle dynamics on the flowsheet level a hierarchical process control concept for plant-wide control is presented. The concept is based on a formal definition of product quality as an intensive state function in the thermodynamic sense. This quality function is evaluated for each product stream in a chemical plant and is employed as a plant-wide controlled variable. Further, such a plant-wide objective function can be used for the integration of process design and control.