Controle do processo de destilação por mudança de pressão utilizando colunas com diâmetro variável.

Abstract

Distillation is the most important industrial process for separating mixtures. An azeotropic mixture needs specific distillation methods to separate its components and one of these methods is pressure-swing distillation (PSD), which uses two distillation columns operating at different pressures. The azeotropic point can be shifted due pressure variation and obtain the substances practically pure. However, pressure-swing distillation in its simplest form can present a high energy consumption, when compared to other separation methods. Some design modifications can be made in the process to make it more economically attractive. Among these changes, we can mention the use of columns with varied diameter (VDC), which can significantly reduce the capital costs. In addition to design changes, determining a process control structure is also indispensable. Control is necessary for a process to operate safely and for the top and bottom products to remain within the desired specifications after disturbances that normally occur in the process. Within this context, this work appeared in order to evaluate the performance of the control of the pressure-swing separation process using columns with varied diameter (VDC). The performance of the process control using VDC was compared with that of the process using columns with uniform diameter (UDC), in face of disturbances in the feeding through PRBS signals (Binary Sequence Pseudo-Random). The Integral Square Error (ISE) was the criterion used to compare the performance of both cases. According to the results obtained, the simulated system with columns with uniform diameter showed lower ISE values for the composition of the products for most of the tested disturbances.