Hi there, new to the forum and still a student. Doing a design project for a separations class, and I'm trying to see if it's possible to something a little weird in Aspen plus.

The setup: we have a hypothetical feed stream (1ton/hr) coming from a shale gas *****er composed of methane, propane, butane, and benzene. We're given several scenarios for the separation equipment setup, and have to meet 95% overall recovery of each component, purity for an LPG stream (95%), and for a benzene stream (99%).

I have all these specs met for one of the scenarios (flash drum, vapor to 2nd flash, liquid to column), and I'm going to mix the liquid stream from the 2nd flash drum (c3 enriched) with the distillate from the column (c4 enriched) for the LPG stream. The distillate stream is coming out at about 5 deg C (~5.1 kmol/hr), and the liquid from the 2nd flash is about -87 deg C (~4.9 kmol/hr).

What I'm wondering is, can I use the liquid from the 2nd flash as the condenser fluid in Aspen (or part of it, eg. water as initial coolant, this stream as 2nd), rather than a refrigerant? How would I go about this?

Thanks in advance