Process control for energy efficient operation of reactive dividing wall columns

Abstract

Process integration offers great potential, both economically as well as ecologically, mainly due to high possible energy savings. However, the design and operation of integrated processes is impeded by complex process dynamics introduced by the integration of multiple unit steps in one apparatus. A prime example, the reactive dividing wall column combines a reaction and several separation steps in one column shell. The high degree of integration results in an especially challenging operation of this apparatus. Reliable design methods and efficient control structures need to be provided in order to enable the industrial application of reactive dividing wall columns. A key challenge is to ensure an energy efficient operation in case of disturbances. This study aims at understanding the underlying dependencies of the most important variables, i.e. the liquid split, the energy demand and the component distribution, regarding energy efficient control. Based on these findings a straightforward decentralized control structure is presented and analysed. The structure utilizes the liquid split as manipulated variable in order to control the component composition on the top stage of the prefractionator. The evaluation of the structure regarding energy efficient process control is carried out by comparison to a structure with fixed liquid split.