Ivan,
A couple of things that might get you on your way.
1) column type, you have shown a full distillation column, with reboiler and condenser - Change to a Reboiled Absorber, you don't have a condeser, the feed stream from the expander is providing reflux for the column (this will remove one of the column specs that you have to define)
2) the feed streams to the column need to be fully specified, i.e. PA1 and PA2. insert a recycle into both streams, so that PA1 and PA2 can be specified (with an initial guess) as the simulation runs it will update the result.
3a) Column Specs, PA1 and PA2 rates. as these are acting as reboilers, these can be considered to be taking a high liquid rate. One way to help specify this flow rate, is to specify the residual liquid from that tray going down the column, you specify this as a small number, so the rest will go to the side reboilers... and as the liquid rate varies so much when its solving, it helps stabilize the simulation
3b) I think i often start with a temperature in the reboiler, as this is a soft spec to get it running and then fine tune later with methane spec in the bottoms.
4) Start relaxed, its best to try and not achieve the targeted recoveries of LPGs straight off, get the column to solve and then dial down the specs (e.g. Ethane in the ovheads) and other parameters etc.
I often use the LNG Exchanger instead of a shell and tube, the setup is easier as the streams and specs are all together and you can do the multiple pass i.e. E-100 and E-104 could be shown as a single unit, Your sales gas stream goes the full distance and the two feed streams 2 and 8 are come in and out. You then can use the combined composite curve to see your pinch points and how you can push more of less flow through the unit (i.e. specify your split from your tees)
Its been a while since i have done one, sorry if some of this information is a bit off, its just what has come back to me.
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NGL HYSYS.pdf 2.08MB
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