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Midterm# 1 CHEN 4520 2011 Solution

Midterm# 1 CHEN 4520 2011 Solution - CHEN 4520 Fall...

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Unformatted text preview: CHEN 4520 Fall Semester 2011 Midterm #1 Printed Name: l agree to abide by the CHEN 4520 Honor Code Signature Please print your name on this cover and all exam problem sheets NOW! Sign this cover sheet, tear off from the staple, and pass it to your left NOW. Take a deep breath, settle down and think straight; this is not a tricky or extremely difficult exam! Good Luck! Heuristics Safet and Current 7 , (1)(2% total) (a)What product was being producedby u had an explosion at theirfactory? (1%) Apple l—pad (b) What caused the explosion? (1%) Dust explosion of aluminum powder (2) (1%) The CEMEX plant in Lyons, CO had issues with the EPA concerning what environmental hazard? Fugitive dust emission of cement powder (3) (1%) The primary blame for the BP refinery explosion in Texas was? Management thosophy (4) (2%) The meltdown of the Fukushima nuclear reactors in Japan that occurred from the earthquake/tsunami in the Pacific was the direct result of what plant design mistake? The backup pumps/pumping system — backup power, etc. for cooling water was not properly designed for this size tidal wave (5) (2% total) How and where are spent nuclear fuel rods stored today in the United States? in pools of water (1%) at each nuclear plant onsite (1%) (6) (2% total) Give two reasons why a water—jet cutting nozzle made of WC and selling for $10 apiece is more expensive to the end user on a cost/performance basis than a composite carbide nozzle selling for $1500 apiece? (1) (1 %) operator down time, not producing product, since they are replacing WC nozzles every 30 minutes; (2) (1%) cost of scrap parts being disposed of because they are out of spec due to wear of the WC nozzle and operators tired of replacing nozzles (7) (1%) Name three types of species that are NOT purged in a process? expensive, toxic/hazardous, byproducts produced in reversible reactions (any 2 of the three) (8) (1%) When using cooling water to cool or condense a process stream, what maximum outlet water temperature in °F is assumed? 120°F (9) (2%) if you are compressing a gas from 15 psia to 300 psia, how many compression stages would you design the compressor for? 3, compression ratio is 20, use heuristic 36 (10) (1%) Typically, it is lower cost to condense a vapor to a liquid, pump it to the required pressure, and then vaporize it to obtain a compressed gas than it is to compress the gas; except in what case? if refrigeration (and compression) is needed to condense before pumping § (201.1355 3101011”? I? Exchange: specification Specification: ; V5355: Minknum temperature 3339105511: From To 5553125551: 55125 Phase: 05515555111 Mole F1551 WATER 5155112501 111018 Fbw Mass flow 515111518 How Temperature Wessure Vapor Fraction Liquid Fraction ._...u._. _...._.,__.... ,1 fl? V , L555” f‘ WW P105555 type: Base method Cold stream outlet vapor 1155110114 :1 3W 3 3 7122959510 I l 5 5 555555 2555555 . 1 1555555” 3553555 3553555 32 51215 7 5575555 2225152 "15154217 25 55555“? .1 . 355 5555”? - 25 55555 "5 25555557 ’75 5555512 ’ 55 27"”1555555 11555555 «’1 115111.525 .11, co 1 ,. (1) (2%) What process simulator is being used? Aspen (2) (2%) What unit operation is being simulated? Heat Exchanger 1 8098013 "1 555555 22. 54215“ ' ’ 155 5321 ” 551 5252 75 55555 '1 555555; 130 (3) (2%) For the property package being used, What most likely is the type of chemical compounds being simulated? hydrocarbons (4) (2%) What is specified in the problem as the basis for this simulation? A cold stream outlet vapor fraction of 1 (5) (2%) Does this process unit operation, as shown, meet the base heuristic for minimum temperature approach? No ii Problem # 3 (12% total) ‘ X E Use the PFD shown 0 e next page to answer the following questions. 1. (2%) What does PFD stand for? Briefly describe what a PFD is and why they are useful. Process flow diagram A simple description is fine. 2. (1%) What software program used in this class is most useful for drawing a PFD? Visio 3. (6% total, 1% each) The unit operations are labeled A-F. Fill in the blanks below with the name of each unit operation (i.e. reactor, pump, etc.). A. wvalve B. _reactor C. _condenser D. _pump E. wdistillation column F. wreboiler or heat exchanger 4. 53%) The combination of unit operations labeled C-F describes a common process in chemical engineering, what is that process? Distillation 836E 6:39.“. DU m< Um <EdJUC3 Um< Dom <ECDUD <mUQ Um DU mAnI Um< Gum <EmUD <mUD (a) (9% total)Determine the true ”mean temperature—driving force”, ATm, in 0F, for a 1-2 shell—and—tube exchanger? (b) (3%) Is a 1—2 design suitable, or should a 2—4 design be evaluated? Why, or why not? The following information may be useful: R _ Thotin‘Thot out 5 _ Tcold out‘Tcold in Tcold out‘Tcold in That in ‘Tcold in ln(2)20.7 ln(0.25)§-1.4 ln(4)21.4 30/ 1.4220 20/ 145-14 20/072530 My“) (Torrectimi Factor. 1‘ 0.7 {is 0.9 U) (a) Solution: ATm=FTATLM AT -AT ATLM = -—-1-—-L Where: AT1 = (90 — 50)°F = 4001: (1%) 111(AT1/AT2) ATZ = (50 - 40)°F = 10°F (1%) . 40°F— 10°F 30 _ 30 ___ o _ ~ 0 0 50' ATLM=1n(40°1=/10°F)= 1n(4)_ 1386 21'6 F: 20 F(1A)) Th - -T 90*50 °F 40 otm hotout _( ) __= 4 (1%) R = _ _ Tcold out‘Tcold in (50‘40)°F 10 T -T ' 50—40 °F 10 S = cold out cold m = ( )0 = _ = 02 (10/0) That in‘Tcold in (90‘40) F 50 Find on the graph that when R = 4 and S = 0.2, FT = 0.8 (2%) ATm = ATLM >< FT = 21.6°F X 0.8 = 17.28°F 5 20°F X 0.8 5 16°F (2%) (b) A 2-4 exchanger is a better choice, since FT = 0.8 for a 1-2 exchanger; it is less than 0.85 (3%) azisiiaaigsiiggg fl/ corsfimy 5.; Xxx atmto. :m 8 Axum m c ”U ,gfzde m cm. ”m 3 v m ow- ”m 3 m S cm. ”Q S o a ow- ”U 3 fl co co H - ”m S m oi cm H - ”< 3 :20 mg 63qu ancmaoo ESE 3% Ilsa: : #59 £th Sign om £535me .3.“ to 2969 3an Stream: TS(°C) lT Teo‘ me(kW/°C) l H1131 100 2 { H2 60 i 5 C1 i 220 l 120 t 3 1 C2 [ 65 I 250 l 1 l a. Determine the heat integration adjusted temperatures and temperature rankings (i.e. To through Tx). Fill in the table below. (3%) H1 H2 C1 C2 T5(°C) 300 240 20 65 T‘(°C) 100 60 120 250 Adjusted Temps S 23o // ~ kw T(°C)// Ranking , 290 iTo T4 b. Complete the stream diagram below. Label the streams and heat capacities. (6%) o /, A”! /° H1 H2 300/ 290 c1 c2 25Q 230 ( l :0.- /0 50 ~274 I 20 c. Determine all of the enthalpy differences associated with this sys em (7%). M? (Zmpbm Ema? mgmslilTi-lg- OTi) AH1= (290- 250)(2)= (40)(2)= AH2= 250- H230)(2 1): (2 o)(1)=020 AHB ( (23o-120)(2+5-1)= (110)(6)=660 ff / o (120- 90)(2+5- -3- -=1) (30)(3) = 90 0’ ‘ AH5= (90 65)(5—-3 1): (2 51)( )= 25 =(65- 50)(5- 3): (15)(2 )= 30 =(5o- 20)(- 3): (30)(-3)= -90 , 32 Hi: i Molar Path2. " + 2F 9 D + 2G Chemical Costs and Molecular Weights Chemical §lkg chemical Mw (kg/kgmole chemical) A $0.20/kg 30 D $0.30/kg 60 E $0.05/kg 60 F $0.10/kg 30 B, C, and G have no cost or value (1) (9% total, see below) Carry out a “gross profit” analysis for both paths to produce D, based on these calculations which path is preferred purely on “gross profit”? Path 1 is preferred based on calculations below. Molar Path 1: A + 0.5 B+c9r D kgmole: 1 0.5 1 1 Mw: 30 ——— —— 60 kg: 30 —— ~— 60 kg/ kg D: 0. 5 —~ -— 1 $lkg “fly/”WW 1% Gross Profit: $0. 30/kg D) ,4 MW?($OW D) - $0. 30— $0 1%»: Molar Path 2: A + E + 2F 9 D + ZG kgmole 1 1 2 1 2 MW: 30 60 30 60 —- kg: 30 60 60 60 —- kg/kg D: 0.5 1 1 1 -- $/kg 2 woos Q, ~ 1° ...
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