Oops, sorry I misread the word "stream" as "steam". You can still use Hysys to draw a kind of Mollier diagram at different T & P for whaever mixture of compunds "phase envelope" , it's called "Envelope Utility". Check the user guide of Hysys for how to use this utility, you may even find it in Help. After entering you mixture and selecting the right thermodynamic method go to Utilities then Envelope Utility.