Abordagem termodinâmica para avaliação da controlabilidade em processos integrados (Redes de trocadores de calor)

Abstract

Nowadays, the interaction between process design and control has become the focus of research and development, because not always the best process design features the best dynamic performance, with implications in the controllability of the plant. Can be noticed that a more integrated design (in terms of energy and mass) leads to a system with smaller gradients for being closest to reversibility. Thus a thermodynamic pre-analysis from the dissipative point of view at steady state, can assist in obtaining a good estimative of an optimal design which will not compromise controllability. The present thesis proposes a simultaneous approach for the economic goals and controllability in the early stages of the process design. The controllability and resiliency are first analyzed using a known heat exchanger network and the Relative gain array (RGA) and disturbance cost (DC), obtaining the control configurations of the proposed networks and their control performance. This results are compared with the proposed thermodynamic approach, where a response time is achieved, as a measure of controllability of the process system applied to a heat exchanger network (HEN), showing the relation between energy and entropy production and process controllability. This analysis showed consistency with the literature results. In addition, the network is synthesized and dynamic simulations are developed, showing that the dynamic response of the integrated heat exchanger network presents a poor response to disturbances, and the effect of adding a bypass stream in the unit closer to the outlet controlled temperature.