The things given : Distillatio
No! you can not take XB = 0.02
- XF is the mole/wt fraction of more volatilecomponent in the feed stream.
- XD is the mole/wt fraction of more volatilecomponetn in the distillate.
- XB is the mole/wt fraction of more volatilecomponent in the bottom stream.
XD = 0.98 means 98 % of Distllate contains molevolatile component and rest 2 % other component. (if it is binarydistillation)
Assume basis: per unit time.
For example, if the distllate (D) is 80 mol and XD =98 mol %. Then the amount of more volatile component in thedistillate will be
- = (Xd x D)
- = 0.98 x 80 mol
- = 78.4 mol
The other component will be 2 mol %. i., the amount of othercomponent in the distillate will be
- = 0.02 x D
- = 0.02 x 80 mol
- = 1.6 mol
Note: This 0.02 mol fraction or 1.6 mol refers to thecomposition in the distillate not in the bottomstream.
XB refers to composition in bottom stream. Tocalculate the amount of XB one shoud know the value ofB.
To find unkonwn values. These two material balances veryimportant.
Feed = Distillate + Bottoms
F = D + B
FXF = DXD + BXB
You can even take material balance over the top of columncontaining Vapor stream (V) , Distillate (D) and some portion ofdistillate fed back to the column in liquid form (L).
V = L + D
Reflex ration R = L/D
Then, the above equation can further be modified to
V = (R+1)D
If you still have any doubt feel free to ask me.