Grass–root petrochemical plant uses simulation-based engineering analysis approach to test safety control schemes, Reduce ﬂare load by 30%
After months of deliberations, the client asked its detailed engineering consultant to turn to dynamic simulation to help them reach a conclusion on the worst case ﬂare relief load thereby improving safety level and saving capital costs. The stakes were high and dynamic simulation was the only recourse leG for the engineering team.
The modeling team studied the problem and available data. Keeping the time constraint in mind, model scope boundary was drawn, along with a list of assumptions – to keep data requirement from the external sources as low as possible but yet to keep the rigor suﬃciently high to draw meaningful conclusions from the analysis.
Modeling the unit
The starting point was to build a sound steady-state model against the licensor’s design data. A few qualitative runs were taken to simulate situations such as reﬂux pump failure to assess the directional impact.
“….We felt really comfortable after we saw scenarios being conﬁgured by Equinox, on-the-ﬂy, predicting trends matching expected behavior from our own plant experience….”
Process Manager, E&C
Next, a dynamic model was constructed by specifying additional engineering details, including pressure-ﬂow relationships and equipment dimensions. All basic controllers were also built, along with safety and ESD interlocks.
Various emergency scenarios were conﬁgured, as a sequence of events, to simulate the pressure built-up, relief valve pop-up to calculate the vapor load through the relief valve. Some of the scenarios studied are listed below:
- Reﬂux pump failure case
- Raﬃnate column reboiler failure
- Extract and Finishing column reboiler failure
The analysis conﬁrmed that with SIL-III implementation, the worst-case relief load was ~30% lower than the original value as suggested by the licensor!
Design the ﬂare network for the load suggested by the Licensor or use SIL-III schemes to reduce the worst caseload.
Apply a model-based engineering analysis approach on the Xylene section that contributes maximum load to the ﬂare header.
A high ﬁdelity engineering model based on dynamic simulation was needed to quantify the relief loads under various scenarios.
- Licensor’s ﬂare load was validated
- Conﬁgured and tested SIL-III control schemes
- Various emergency scenarios of partial power failures were simulated
- Worst case relief load was ~30% lower than Licensor’s worst case, with SIL-III implementation