Week 9 Challenge

Week 9 - Depressurization

Question-1

Answer:

The required restriction orifice size for emergency depressurization of the vessel for the given conditions is 78.54 mm2.

Calculated final pressure is 119 kPa at a depressurization time of 15 minutes with a 0.25 seconds step change.

The Aspen HYSYS file is uploaded (week 9 challenge Question-1) for the review.

Question-2

Answer:

An error of step size too large and/or other possible errors appearing while performing simulation using the specified conditions.

So pressure is reduced to 7 barg and calculations were performed.

The duration required to reduce the system pressure down to 103.3 kPa from 7 barg (1101 kPa) using restriction orifice size of 15mm diameter is 20 minutes.

Suitable iterations have been performed to reduce the calculated final pressure to 0.1 barg. But after certain iterations the simulations are being crashed. So the simulation has stopped after reaching 103.3 kPa which was the minimum pressure after depressurization is performed.

Vapour phase molecular weight – 60.34

Vapour phase compressibility factor – 0.9677

The Aspen HYSYS file is uploaded (week 9 depressurization Q2) for the review.