HW 3 - p 4.52 - Leaching Oil from Soybeans Using Benzene as a Solvent - 4 pts
Repeat Example 4.9 for 200,000 kg/h of hexane.
posted by Dr. B at 2:28 PM
Wednesday, September 20, 2006
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12 Comments:
The graph you put in the hints is very different from the Figure 4.22 in the book. Which one should we use?
confused but... 3:13 PM:
Use the one in the book. They changed this problem on me from the last edition and I did not notice.
I was going to pass out a scanned version of figure 4.22 in class on Monday. If you want to solve it now, you can go to the course homepage or the Downloads page and get a big, printable PDF version of figure 4.22.
Thank you for pointing this out.
so does this mean that the answers you give for this problem are incorrect?
confused but... 8:29 PM:
DOH. Why, yes it does.
I think the correct answers are:
a.) 89% and b.) 68%
But I am trusting the author at this point.
I have not yet done this "new" problem myself.
The example problem that this HW problem is based on was pretty confusing. So, I made up a 1 page PDF to help you get started on the solution. I suggest you IGNORE all the author's nomenclature on this one (XA, YA etc) and just solve this like any other material balance problem with some equilibrium data thrown in to make it more interesting. I hope you find this page helpful. You can download it from the reminders section of the course homepage as well as the downloads page.
For both the analytical and graphical method I got 80% as the amount of oil extracted in the overflow. What is part b? And could you tell me if there is anything wrong with the method I used? Solved for XB(mass of solute/total liquid) = 0.085. used this to interpolate for Beta = .676. Used Beta to solve for total underflow with Underflow = mass of solid/Beta. found other unknowns with this information.
thanks,
kl
I concur with anonymous and I did it the mole balance way using your PDF. Do we still need to do part B and use the graph, or is it okay to just do it the mole balance way and call it good?
Anonymous 5:34 PM:
I got 79% by the graphical method and 80% by the analytical method. So, I suspect you did it correctly, but I cannot say for sure. Your value of XB(mass of solute/total liquid) = 0.085 is correct. I think the rest is correct too. Take the rest of the night off !
peter pan 5:46 PM:
Anon is right and so are you...at least as far as I can tell. Please do the graphical solution as well as the analytical. It is quick and easy once you understand the analytical solution. It just isn't as accurate.
dr. phil 8:04 PM:
I could not agree more with you about the author's choice of variable names in this problem. Please download my 1-page pdf and ignore the author's variable names. Just look at the UNITs on the axes in Fig 4.22. Based on my pdf, you will see that this is just an ordinary material balance problem...with one little equilibrium relationship. In my pdf, pay special attention to how to interpret the author's data table. Then, just solve the material balance equations and use the results to answer the questions.
Ok on the homework page you still have the link to the wrong figure about benzene. It was all very confusing, but I found the right figure underneath downloads. I know you don't care, but I somehow feel better bein able to complain about it at 12:20 in the morning.
dr. stuve 12:25 PM:
I am glad venting made you feel better. No problem.
You did not need my scanned copy of the figure in the book to complete the problem.
I just scanned it to be helpful.
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