In this paper, the operability of a high-purity distillation column is presented. This process is known to be difficult to control and operate due to the high degree of nonlinearity of the process. The analytical framework used to assess the process operability are the regions of steady-state attainability, recently developed by Rojas et al (2006). This framework is selected because it allows one to assess the viability of applying linear control to a nonlinear process solely based on the process nonlinear steady-state information. In this approach, two operating regions are defined in both input and output spaces, which provide an indication of the inherent difficulty of controlling the nonlinear process using linear output feedback. In order to integrate this operability analysis in process design practice, the analysis is based on a numerical steady-state simulation of the column using ASPEN PLUS®. By using ASPEN Sensitivity Analysis Tool that varies the column inputs across a pre-defined Available Input Space, the steady-state nonlinear map of the column outputs can be generated. Based on these simulation results, the regions of steady-state attainability can be obtained and used to provide insights to the operability properties of this highly non linear system.
©2011 Walter de Gruyter GmbH & Co. KG, Berlin/Boston