Greetings everyone!
I have one question concerning rectification process (countercurrent distillation).
For example; if you have a process in which a feed of water-methanol solution (F) (22%mol) with a flow of 6.5 kg/h enters a column. Inside a column a feed of vapours (V) has value of 7 kg/h with 95%mol. If reflux ratio is 2.5, what is the value of reflux going back into the column (L) and fraction of distillation residue (xw)?
If my knowledge is correct then you get reflux (L) from reflux ratio and mass balance of vapours:
R=L/D 2.5=L/D
V=L+D 7=L+D
From this you get: D=2 kg/h and L=5 kg/h
Then from the mass balance of feed you would eventually get a distillation residue:
F=W+D 6.5=W+2 W=4.5kg/h
F*xf=W*xw+D*xd 6.5*0.22=4.5*xw+2*0.95 xw=-0.104 (?????)
Question I want to ask is, why do I get negative value of distillation residue? Is my procedure correct? Do you in this case consider absolute value of xw?
Could someone please help me?
Regards,
Filip