2 replies to this topic

Hello, I want to have my distillate in vapour phase and hysys guides are telling me to put choose the "full reflux" option. My understanding of this is that all the condensed liquid is returned to the column hence im a bit unsure.

Ive drawn a very rough diagram below as to how i understand it, a. is a total condenser b. full reflux condenser
 Cond.jpg   7.99KB   87 downloads

I also assume the vapour distillate and the reflux compositions are going to be the same, or am i wrong? Thanks!

[Zauberberg]

You are right about the concept of total reflux. All liquid from the overhead receiver is refluxed back to the tower - there is only vapor product from the reflux drum. A common example of total-reflux system is Sour Water Stripper (SWS). That corresponds to the sketch "b" in your attachment.

Answer on your second question is: NO, because vapor and liquid composition will depend on the overhead stream composition and vapor-liquid equilibrium (ideally: Raoult and Dalton law) at overhead receiver conditions (p, T). Again, you can refer to the SWS example where liquid phase is mainly water (saturated with acid gas at vessel conditions), while vapor stream is acid gas saturated with water at the same conditions. In reality, these two compositions will never be identical unless you are condensing 100% pure component as overhead stream.

Edited by Zauberberg, 22 March 2010 - 11:32 AM.

You are right about the concept of total reflux. All liquid from the overhead receiver is refluxed back to the tower - there is only vapor product from the reflux drum. A common example of total-reflux system is Sour Water Stripper (SWS). That corresponds to the sketch "b" in your attachment.

Answer on your second question is: NO, because vapor and liquid composition will depend on the overhead stream composition and vapor-liquid equilibrium (ideally: Raoult and Dalton law) at overhead receiver conditions (p, T). Again, you can refer to the SWS example where liquid phase is mainly water (saturated with acid gas at vessel conditions), while vapor stream is acid gas saturated with water at the same conditions. In reality, these two compositions will never be identical unless you are condensing 100% pure component as overhead stream.

cheers for the help! The top stream is 98% pure of the desired product, but yeah, ill have a good look into this. Thanks again!