Practical distillation control

The presentation highlights the practical experiences gained in adapting predictive control technology to solve a difficult distillation control problem. Control of product impurity and product losses using off-line 8-hourly laboratory measurements combined with predictive inferential techniques avoids the need for online analysers and enables more consistent column performance. Introduction of complex control technology offers benefits in terms of solution flexibility, but may pose potential operating and system management problems. Developing a hierarchical control strategy plus a simple operator interface helps to minimise operator complexity. Implementing a structured control engineering tool with a reliable communication interface minimises support costs. The experience highlights that process inconsistencies are a major cause of performance problems and continuous control engineering support is needed. It is therefore essential that the support control engineer be fully familiar with the process application, interactions and data inconsistencies