HW 7 - p 13.1 - Rayleigh Distillation of nC7 in Toluene - 8 pts
Please post all of your questions about this problem as comments on this post. I will respond with my own comments.
posted by Dr. B at 5:48 PM
Wednesday, November 15, 2006
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8 Comments:
Can you assume that K is constant, and then use equation 13-4 from the book to find Wf?
madagascar:
You must assume K is constant in order to use 13.4. But in this problem, do not assume K is constant. Just assume that alpha is constant.
By assuming that alpha is constant, does this mean to use Eqn. 13-5 to find Wf (given as W in the book)?
What exactly are we supposed to plot? I found the ratio of Wo/WD (ratio of mass initially in the pot to mass distilled) and the curve looks crazy. What goes on the y-axis and what goes on the x-axis? I was putting the values that I choose for zc7 on the y-axis and Wo/Wd on the x-axis. In your hints it says that you also claculated a whole bunch other values, ie average mass frac of nC7 in distillate, etc. Why? Also, when the question asks for "composition of residue when 50wt% of mass has been distilled" what is the residue? What's in the pot still?
igor:
Yes, use Eqn 13-5.
igor again:
PLot the fraction of the mass distilled (boiled off as distillate) as a function of the mole fraction of C7 in the residue. The residue is the pot.
Amm... How can i find the W
anon:
Use eqn 13.5. Calculate alpha from the 1st data point at 2.5 mol%. That is as close as we can get since our process operates at or below 2 mol%. The other data is not relevant.
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