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[vne]

Dear all,

I am doing blowdown calculation for a depropanizer using the Depressuring utility in Pro/II (DEPR). Purpose is to find the depressurization rate to size the RO. I have some querries which need your help:

1. My understanding is that 4 DEPRs should be built: 1 for the tower, 1 for the reboiler, 1 for the condenser, and 1 for the receiver. Depressurization rate from those 4 units will be summed up to find the total depressurization rate. Please confirm if my understanding is correct.

2. I understand that, to peform blowdown calculation for a vessel, the feed stream to the DEPR would be the feed stream to the vessel. But for the case of a distillation tower to be depressurized, which stream should be taken to be the feed stream to the DEPR utility? I'm thinking of the following options but not sure which one is correct:
a. Feed to the DEPR would be the feed to the tower.
b. Feed to the DERP would be the liquid stream from the middle tray of the tower (it is assumed that this liquid stream represents the composition of the fluid to be depressured)
c. Feed to the DERP would be the combination of: 1) liquid stream from the middle tray of the tower, and 2) vapor stream from the middle tray of the tower.
d. Feed to the DERP would be the combination of: 1) the OVHDS vapor, and 2) the BTMS liquid.

Thank you