HW 5 - p 6.10 - Graphical Analysis of Steam Stripping Benzene from Straw Oil in a Tray Tower - 7 pts
A straw oil used to absorb benzene from coke-oven gas is to be steam stripped in a sieve-plate column at atmospheric pressure to recover the dissolved benzene. Equilibrium conditions at the operating temperature are approximated by Henry’s law such that, when the oil phase contains 10 mol% C6H6, the C6H6 partial pressure above the oil is 5.07 kPa. The oil may be considered non-volatile. The oil enters containing 8 mol% benzene, 75% of which is to be recovered. The steam leaving contains 3 mol% C6H6. (a) How many theoretical stages are required? (b) How many moles of steam are required per 100 mol of oil-benzene mixture? (c) If 85% of the benzene is to be recovered with the same oil and steam rates, how many theoretical stages are required?
posted by Dr. B at 2:41 PM
7 Comments:
On Xn+1 for part a some people i've checked with get 8% or .08. Is this correct? isn't Xn+1 supposed to be mols of solute divided by mols of benzene. Shouldn't the answer in the HW hints have 8/92 which leads to a vapor flow rate around 210?
Anon:
You lost me.X = x/(1-x) where x = 0.08 mole Ben/mole liquid. Plug in values and get a X just a bit greater than 0.08 mol ben/mol oil.
I don't know how to find the K-value to plot the equilibrium curve. Can I use the Rault's law, which is 5.07/101.3?
Does the theretical stages require is the stage at the minimum solvent require? If not, How can i know the mole fraction of the gas input?
Anon:
Use Henry's Law: yi P = xi H
The value of H is given in the problem statement.
a:
This is a stripper. L = 100 moles. There is no Lmin for this problem. You know L and you compute L'. Then, in part (b), you compute G' by material balances. Use L' and G' to construct an operating line. Use Henry's Law to develop and equation for the equilibrium curve in the form Y = mX + b. Finally, step-off the stages on an XY Diagram.
can i get answer for distillation problem
Post a Comment
<< Home