Choosing control structures based on economics

Concerns the application of a method for choosing the objectives and structure of control systems for chemical processes to the gas-tail of an existing oil refinery. The method uses nonlinear models and linear analysis techniques and aims to quantify the economic effects of improved control. The objective of the process is to separate a mixture of light hydrocarbons, produced as one stream during rectification of crude oil into valuable products using a sequence of distillation columns. The plant exhibits operating characteristics which are typical of large scale petrochemical processing, both in terms of the dynamic behaviour of the equipment and in terms of the requirements imposed by operating methods. The procedure consisted of three parts; nonlinear physically-based modelling, derivation and analysis of linearized models to determine economic implications and improved control system structures, and dynamic simulation