ChE 250

Spring 2000  

Problem Set #7

Due Thursday, March 23

[Reminder: Exam II is Thursday, March 23, at 7:15 pm in 1800 Engineering Hall]

 

Read Rudd, Chapter 4 (Separation Technology).  Some parts of F&R Chapter 6 (intro, 6.1, 6.4-6.6a) may also be useful, but do not be distracted by the heavy thermodynamic flavor of this chapter.

 

1.   Do F&R problem 6.89 - oleic acid extraction

 

2.   Penicillin recovery (parts a, b, and c from old Exam II)

 

Penicillin and other antibiotics are often recovered from aqueous fermentation broths by extraction with amyl acetate (also famous as banana flavoring).  The distribution coefficient is K = 9.0, where y = K x, with y = concentration of penicillin in amyl acetate (g/liter) and x = concentration of penicillin in aqueous stream (g/liter).  Both solvents are insoluble in the other, and the concentrations are low enough that volume changes are negligible.  A typical fermentation batch product is 5000 liters of aqueous solution, including 2 g/liter penicillin and many undesired compounds that are fortunately not soluble in amyl acetate.  We are going to build a plant in Wisconsin, and are evaluating extractor setups used in the company’s California and New Jersey facilities to decide which equipment will give the best product recovery.  For each strategy ((a) and (b)), determine the % penicillin recovery, total amyl acetate use, and concentration of penicillin in the amyl acetate streams produced.

 

a)   The California production engineers use a 10,000 liter tank to mix and settle the 5000 liters of broth with 5000 liters of amyl acetate. 

 

b)   The New Jersey process uses a 6000 liter tank and two sequential mix/settle steps, each using 1000 liters of fresh amyl acetate with the 5000 liters of broth.

 

c)   Point out advantages and disadvantages of each strategy.  When would each be preferred?  Can you suggest the “best” approach?  [Note that countercurrent extraction can’t be done on a single batch of broth.] 

 

d)   We want to obtain 96% penicillin recovery, and improve on the performance of the existing plants.  Calculate the amyl acetate flowrates required for multistage crosscurrent extraction in 1, 2, 3, and 5 stages.  Repeat for 1, 2, 3, and 5 countercurrent stages (now we’ll use several batches of broth if it helps the process).  Report the results in a table for convenience.

 

3.   Do F&R problem 6.73 - H₂S absorber/stripper