PracticeFinalSpring07 - NAME Separations Processes May 12,...

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Unformatted text preview: NAME Separations Processes May 12, 2007 CHE 363 . FINAL EXAM You may refer to a text of your choice (including the Continuous Distillation Chapter 12 and Belter Drying and Crystallization printouts), but no class notes. Short answer (2 pts each) 1. Give the dimensions of the following in terms of length L, mass M, time tand temperature T a. population density n (dN/ d6} 5. overall mass transfer coefficient based on a partial pressure driving force, kp i c. adsorbent concentration at saturation qo d. crystal nucleation rate B e. diffusion coefficient D 2. Which separation technique is indicated for the following processes?,Choo'se from: ajgsorption/ stripping, agsorption, distillation, membranes, extraction, leaching, drying. c'rystaliization. , - a. Acid to recover copper from low-grade ore b. Purifying blackaaWaiian sea saitto sell for $9 a bag at Whole Foods ‘ 0.. Purifying bioCethanei from a liquid culture of yeast (an aqueous f‘beer’) yd. Chasing a Drano cocktail with activated charcoai Aeratingiyo'ur trepicai- fish tank with a bubbler 3. in distillation;weuid a feed cornposed‘of saturated vapor or saturated liquid likely require'ir’nore stages and why? Which would require more energy? ~, ,,~:.M,hmawm.__w~ “WWW. 7,,UAM.WA.L,,W: a...” “W. WW Problems: SHOW YOUR WORK 1. Mg(OH)2 can be made by continuously reacting MgClz and Ca(OH)2 in a 1 L stirred tank. The population density vs crystal size for an average time of 300 seconds is given below. ,1 f a. What is the growth rate? pts) ‘ b. What is the nucleation rate? (W) 3~< H O O O .A O O Illlllll-IIIIII I“ «:r l < E U V > :‘:.' m c a 1: C .2 +1 53 :1 o. a a. % i 2‘; t a t g ' 2. You want to scale up an adsorption process; your small-scale laboratory column (1 cm diameter, 20 cm long) showed a breakthrough time of 40 min and an exhaustion time of 52 minutes. Other experiments suggest that the unused bed length (LUB) is about equal to an HTU and you expect mass transfer coefficients in this bed to vary inversely with the square root of the flow rate. in your new column, you need 10,000 times greater capacity using a bed 130 cm long (to minimize the pressure drop). You plan to increase the flow 17 times. a. What is the LUB for the small-scale column? (5 pts) b. What is the LUB in smallascale column with the new flow-rate? (5 pts) 0. For the large column, what bed diameter should be used? (10 pts) E Q g z 3 E E 1 § E 4. You want to absorb 99% of the carbon dioxide in 4.2 kg/sec of nearly pure air by washing it with water in two countercurrent stages. The water enters pure. The equilibrium iine under these conditions is y* = 16 X. How much water is required? (10 pts) - I‘ l A. 5. You want to purify 99% trichllorosilane to produce a 99.999% distillate in a differential distillation cdlumn wi'th 9.6 transfer units. The equilibrium line under the operating conditions of this column is y* = 0.65 + 0.35x. You plan to feed the column at the bottom with a saturated vapor. The column has a total condenser but no reboiler. What is the highest purity trichlorosilane you canmake with this column? (20 pts) ' ’ - f ,3» ,‘ ...
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PracticeFinalSpring07 - NAME Separations Processes May 12,...

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