University of Alabama Chemical & Biological Engineering - CHE Spring 2017 Name: March 31, 2017 EXAM 2 P a g e I 1

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1 University of Alabama Chemical & Biological Engineering - CHE Spring 2017 Name: March 31, 2017 EXAM 2 P a g e I 1 e Multiple Choice Questions (SO Points: 25 Questions, 2 pts each) Before a vapor feed enters a flash drum, it must first pass through a a) Heater and Expansion Valve b) Compressor and Membrane <[ Condense!) d) Chemical Reactor and Flare Which of these is not one of the possible calculation methods for flash drums that was discussed in class? a) Adiabatic Flash b) Isothermal Flash (Cf Supercritical Flasti) d) Bubble Point An adiabatic flash implies that the energy balance for the flash unit is: a} Q= HvV + Htl-HFF > 0 b} Q = HvV + Htl - HFF < 0 (? 0 - AvV + H1 L - HEE =]) d) Q = HvV + Htl- HFE + Ws =\If In addition to specifying Q, the other variable specified for an adiabatic flash is: a) Temperature b) Gas Phase Mole Fractions c) Liquid Phase Mole Before a liquid feed enters a flash drum, it must first pass through a a) Liquid-Liquid Valv"D c) Partial Condenser d) Reboiler

2 University of Alabama Chemical & Biological Engineering- CHE Spring2017 The expected outputs of a flash drum are typically: a) One or more supercritical fluid streams GI?eparate vapor and liquid stream"s) c) Just vapor streams d) Just liquid streams '11 is defined as the ratio of: G[ Vapor to Fee<b b) Feed to Vapor c) Vapor to Liquid d) Liquid to Feed The feasible range of values for \If is: a) Os \If< oo b) -00 < '11 < d) -1<'11<1 In a liquid-liquid extraction, the entering liquid containing the solute is known as: a) c) Extractant d) Electrolyte In a liquid-liquid extraction, the two phases created after mixing are known as: a) Permeate and Retentate b) Distillate and Extract and Raffinate') d) Stationary and Mobile Phases

3 University of Alabama Chemical & Biological Engineering - CHE Spring2017 On a ternary (triangle) phase diagram, each corner of the triangle represents: G[: Pure com po~ b) Equimolar mixtures of 2 components c) Miscibility boundary d) Minimum solvent needed to create phase separation On a ternary (triangle) phase diagram, the "center" point (0.333, 0.333, 0.333) of the triangle is located at Cartesian (x,y not triangular!) coordinates: a) 0.5, 0.5, VJ/6 ") c) 0.5, VJ/2 d) VJ/6, 0.5 Suppose a liquid-liquid extraction is carried out in a vertical column with two immiscible solvents. Solvent 2 is denser than Solvent 1... how should each solvent flow into the column to promote good mixing/contact? a) Both enter at middle of column b) Solvent 1 enters at top and Solvent 2 enters at bottom o ven enters at bottom and Solvent 2 enters at top d) Both solvents enter at ottom or top The ratio relating the mole/mass fraction of a solute in two liquid phases is called: a Selectivity b Distribution Coefficie c) K-value d) Partition Factor Adsorption is useful when the concentration of the species to be removed is: a Moderate Low c) High d) Any of the above

4 University of Alabama Chemical & Biological Engineering- CHE Spring2017 Which of these methods can be used to quickly find iterative solutions? G[NewtO!}) b) Einstein c) degrasse Tyson d) Gaussian Crystallization is typically 3 unit operations in series. Which of these unit operations is not part of the process? a) Crystallizer b) Filter < [ Coalescer o:) d) Evaporator The point on an LLE ternary phase diagram where the tie lines converge is called? a) Singularity b) Event Horizon c) Plait PoinJ) Which of these mixtures is probably a good candidate for a flash separation? Ethanol - Water Benzene-Toluene Butane - Decane Propane - Propylene For adiabatic flash, the stream with the largest specific enthalpy value (e.g., kj/mol) is? a) Feed - if it's a liquid b) Feed - if it's a yap""qd d) Exiting Liquid

5 University of Alabama Chemical & Biological Engineering - CHE Spring2017 C» Name: March 31, 2017 EXAM 2 P a g e I 5 The relationship between the quantity adsorbed (q*) and equilibrium concentration is solution (c) is best described by (where A, bare constants): df" q*= Acb (power functio}ij) b) q*= Abe (exponential) c) q*= A+bc (linear, positive slope) d) q*= A-be (linear, negative slope) Adsorption can occur via physical interactions (reversible) or chemical reactions (irreversible). (fiffi0 FALSE K-values can be negative. TRUE ~ For a flash separation to be effective, <li,j should be close to 1. In industry, liquid-liquid extraction is performed in giant separatory funnels. TRUE ~

6 University of Alabama Chemical & Biological Engineering - CHE Spring2017 Name: March 31, 2017 EXAM 2 P a g e I 6 fj Short Answer Questions (20 Points: 4 Questions, 5 pts each) Other than making coffee/tea or extracting soybean oil, give an example of leaching (creative answers accepted!): asr~~~~! MA1 1r:h ~1',0t.lS ~Cbl lm..) 'DI ~1N6 (~c.o) WAie" +a'-"5 <.44"{0A) Cc:c.oA ~ + Mtt...w!. ~ v~lua e;;ttb1c1' ~ f1se,.. '8<..all> lo» 0 ~ 8/lCt".ff. 6MMt ~ l>el~. Why is a recycle loop important to crystallization processes? ~ ~l/j6- "1b'-( ea> I.SS"~~ "CoCA ~.. ''~~~ ia:;:: ~ ~ ~,J OAl.SMf tt '"\'tump's MAI 12.. COCA~ t{c Yeo 1"ff'I cau..:1 &U'l"J '1 C2..~ 1::E" 4-t:> ~ ""-'-- ()/:.. ~ 1)~\l@ f>e.o?>ucr 1~ :1 P4:ss. 1l h6 ~I EiW Mt AAfl.:(ES t.c.a'sle" /'SS<Je:;s List three factors which might make an adsorbent effective for a given solute: Ht&-\--.svef'~ N.eA '~~ ~~'4 w/ ~ ~ /\.CT",~.,.. v.;/ :sou,ejt l..()w 10 e,e.1()~ ~~ In the lab, why are most liquid-liquid extractions done in 3 (or more) steps with smaller amounts of solvent rather than just 1 step with a lot of solvent? sfc.- '/e0 tx>n'r l)s~lv{ ~ fle '""'5E" btaoem ~ 1t> Aa:>l:> ~ ~ JS;r 8"Cf( ~ef:j ltjst~ Dr=- LI/!(; ~JJr:- J.-4t6MT CAJSE j ~

7 University of Alabama Chemical & Biological Engineering - CHE Spring 2017 Sketch and label a liquid-liquid extraction (LLEx) process coupled to a distillation column including a recycle loop. The feed to the LLEx is water + acetic acid (AA) which is contacted with pure ethyl acetate (EA). AA is the desired product. (15 points)

8 University of Alabama Chemical & Biological Engineering-CHE Spring2017 Liquid - Liquid Extraction (15 points) Using the diagram below, answer the following questions: What is the maximum wt% of W in EG that when mixed with pure F would not create 2 phases? What are the compositions of F + EG and W + EG streams that when mixed would create a line tangent to miscibility boundary at the plait point? ~ F; o.9 w: 0 '23 l.31 as: o.z.. e&= 0.1; What are the maximum wt% of F in EG and W in EG that when mixed would not create 2 phases? What are the wt% of F, Wand EG in the final f': O.c.rl w. 0."(1 fi"'a'- :: 66 O. -S3 e,; O t>3 E"G to ~3 ';/ ~~ 'ft>ep9'.l:>as_~~ MJ't:5.SCS Ethylene Glyeol ~~

9 University of Alabama Chemical & Biological Engineering- CHE Spring 2017 Name: March 31, 2017 EXAM 2 P a g e I 9 Extra Credit (up to +3) Suppose we connected flash drums in a cascade like this: ~~b-l /..fab\>ess... 'S&AtA=t<.:::S He:~ ~ eo.,s. What other separation process does this start to resemble? D1sT1LLA-rlo0 cnw40 o 'WO \~Ail()\)At ~ c> ~ Ptes a-r ~"'"'t't oa Pree~ (~ l'<m1).:.; i+l6h-~<.. ~ l>pe$5ep Li~Pt&ff;5 Do you like Pi Day? Why or why not? l'to'a~ 'B~'f v - ~ "' It a 8~ ~ 8bA'1 ~ 0<1'~a..""< int>l~ - L, "lta=p'~ B"l>Ac"f v &-G,eu:te1 )...f-:> 7J:;:JltJoN 31n ~...C'1 Bl>A'-f v (>c'2) Lc>.E e>f=-.p1 v M\&14 ~ ret~ ~ ~ lb ~15~l>16n'$ ;( WC>J Pet!E; ~ HeJ'd.t~~ rt a Survey of electronic devices (make and model): t-\-6 ~~ ~ Res~ Smartphone: lr~: JO't ~ b-; 2.3 Tablet: f>abt "'lb ~" 1~ Laptop: MAC.~-' ~a pc; 1-'t Desktop: M~C. 5 pc;;; 10 ~ ~.S