Distillation Column Flooding Predictor U. S. Patent 5,784,538

Technology Brief

The Flooding Predictor is an advanced process control strategy comprising a patented pattern-recognition methodology that identifies pre-flood patterns discovered to precede flooding events in distillation columns. The grantee holds a U.S. patent on the modeling system. The current project, Distillation Column Flooding Predictor is funded in part by the U.S. Department of Energy. Forty-nine percent of the project will be financed by federal funds, totaling $444,037. The technology was validated at the Separations Research Program, The University of Texas at Austin under a previous grant from the U. S. Department of Energy, Inventions & Innovation Program.

Distillation tower flooding occurs at abnormally high vapor and/or liquid rates. The loss in tray efficiencies is attributed to unusual behavior of liquid inventories inside the column leading to conditions of flooding of the space in between trays with liquid. Depending on the severity of the flood condition, consequences range from offspec products to equipment damage and tower shutdown.

The discovery illustrates that anywhere from 5 to over 60 minutes in advance of every flood event the column experiences a subtle, identifiable oscillation. The oscillation occurs among column variables such as pressure, temperature and flow.

This non-intrusive pattern recognition methodology, processes signal data obtained from existing column instrumentation. Once the pattern is identified empirically, it is modeled and coded into the plant's distributed control system. The control system is programmed to briefly "unload" the tower each time the pattern appears. The unloading takes the form of a momentary reduction in column severity, e.g., decrease bottom temperature, reflux or tower throughput.

Unloading the tower briefly at the pre-flood state causes long-term column operation to become significantly more stable - allowing an increase in throughput and/or product purity. The technology provides a wide range of value between optimization and flooding. When a distillation column is not running at capacity, it should be run in such a way ("pushed") that optimal product purity is achieved.

Additional benefits include low implementation and maintenance costs, and a high level of console operator acceptance. The previous commercial applications experienced 98% uptime over a four-year period. Further, the technology is unique in its ability to distinguish between different flooding mechanisms within the same tower, e.g., liquid and jet flooding.

From the Report on the Distillation Column Flooding Predictor at the Separations Research Program, The University of Texas at Austin.

• The Flooding Predictor works well with both packed and trayed columns.

• The Flooding Predictor maintained an average duty 99% of flood for the packed column tests and 99% of flood for the trayed column with relatively few difficulties.

• One major benefit of the Flooding Predictor control strategy is having the capability to run very close to the flood point, where the highest efficiently and highest capacity occur.

• The Flooding Predictor can be installed on nearly any process control computer.