Effects of Process Variables on Dynamic Relief Load Estimates for a Depropanizer and Debutanizer

Recently, emphasis on increasing process throughput has generated an incentive to refine relief systems calculations in lieu of costly (on often unjustified) facility modifications. One method that is currently being used to refine relief systems calculations is dynamic modeling of the process upset. This paper analyzes the relief requirements for Depropanizer and Debutanizer Tower based on dynamic simulations. The paper focuses on showing the differences in input assumptions (liquid levels, column pressure, control status manual/automatic).

In addition to showing the reader how dynamic simulation modeling can be used to refine the expected relief loads to a more realistic value, the process will show the effects of the initial assumptions on the final relief rate and the time it takes to reach peak relief rates. The use of dynamic modeling for flare relief loads will be reviewed.