Studies on design and plant-wide control of chemical processes

Abstract

In order to deliver quality products with the lowest possible costs and energy consumption, the chemical process industry is constantly evolving. Recycling and energy integration are common place in an industrial plant. Moreover, new products and processes are being developed. The multiple challenges require an effective control system, from the perspective of the entire plant. In this thesis, two important issues of plant-wide control (PWC) are studied. Firstly, many PWC methodologies have emerged in recent years but systematic comparisons of them are scarce. In this study, the ammonia synthesis process is employed as a test bed to develop, and to compare the performance of two new and promising PWC methodologies ¿ the self-optimizing control (SOC) and integrated framework of heuristics and simulation (IFSH). Unbiased performance indicators are used, and the conclusions drawn will give some insights for the control engineer to select a suitable methodology for his/her applications. Secondly, decisions based on design perspective and control perspective can be conflicting. In order to have an overall optimal plant, one has to design and analyze from both these perspectives. To investigate this, biodiesel process is considered in this thesis for its interesting alternatives in plant design and contemporary importance. Several alternative process flow sheets are developed and compared based on economic profitability and dynamic control performance. This novel study provides insights to the process dynamics and recommendations for the optimal biodiesel plant.