CBE40 F18 HW6 Solutions FINAL.pdf

# You may assume that liquid gas separations are

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You may assume that liquid-gas separations are perfect (100.% separation) if boiling points differ by more than 3ºC. Solid-liquid separators produce wet solids. You may add recycle streams Some properties at 1 atm. mol wt. melting pt, ºC boiling pt, ºC price (\$/mol) notes A 120 3 121 100 must not be heated above 250ºC B 133 3 122 35 P 120 3 123 1000 Q 120 18 147 20 suspected carcinogen Z 133 28 95 10 non-toxic b) Calculate your total product revenue in \$/hr. Analyze the process you designed. What do you need to know to decide if it is worth converting more A to P and less A to Q, for a higher product purity? a) The answer should be a PFD whose inputs are 90%/10% mixture of A and B and whose outputs include a stream mostly composed of P. The solution below meets the design challenge, but schemes that do not meet the challenge are also acceptable. Please see the points breakdown to better evaluate student answers.

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F18 HW6 CBE40 Solutions Revenue Calculation: Total revenue = output price = 80*(\$1000) + \$20 + 10*\$10 = \$80,120 Total profit = revenue input cost = 80*\$1000 + \$20 + 10*(\$10) 10*\$35 90 *\$100 = \$80,000/hr Point Breakdown : Part A: 3 points 0.5 points : all streams are labeled with flow rate and composition Give credit if less than 3 labels are missing. Otherwise, no credit. 0.5 points : Separators are labeled with viable temperatures of separation 0.5 points : Use a recycle stream. 1 point : Output of less than 5mol/hr Q 0.5 point: Output stream with at least 80%P Part B: 1 point 0.5 points: revenue calculated correctly according to the student’s PFD. 0.5 points: comment on some aspect of the process including revenue, number of reactors, reactor number, purity of product, amount of byproduct, recycle stream, etc. Notes to readers: Solutions may vary widely. Most important is that PFD is logically consistent. Note to readers: Another way to do it is to put Reactor 3 and the separator first, so the 10 mol of B/Z are gone earlier and other units are smaller. Then the recycle around reactor 1 has 1190 mol P and 70A. Note to readers: Give 2 extra credit points to any student whose process meets the design challenge. Total HW grade may exceed 100% as a result.