(22e) A Dmcplus Tale of Two C3 Splitters

This presentation will describe the implementation of DMCplus controllers on two ?identical? Linde design C3 Splitters. The C3 Splitter setup is composed of two towers -- the first operating at high pressure and the second at lower pressure. Both towers produce overhead propylene polymer grade product and are highly integrated, making it a challenging control problem.

The projects were part of a large program where significant benefit was obtained from the sharing of experiences by the two project teams. Although the two units are in principle identical, regulatory control differences led to two different approaches in solving the control problem.

A curious occurrence during the execution of the projects was the discrepancy between the RTO models and the DMCplus empirical models on a particular MV/CV pair. This was a good example of exercising caution and making sure you compare ?apples to apples? when doing a RTO/DMC consistency check.

Results of the C3 Splitter controller objectives will be presented:

• Decrease propylene product loss in the bottoms.

• Improve overhead propylene composition control.

• Maintain MAPD at or below the high limit.