MEMORANDUM TO: FROM: DATE: SUBJECT:
Daniel Groom Clayton Gregory and Antonio Hernandez 08 June 2015 Distillation Operation Draft Report
Introduction:
The main objective for this experiment is for the students so gain experience operating and controlling industrial distillation equipment. Also, it is important for the students to learn how to perform field operational capacity tests of a column and understand the theory behind a column’s flood point and column flooding in general. The experiment will operate the column at a total reflux condition, obtain samples from the reboiler, each tray, and the accumulator, and analyze each sample in a gas chromatographer. McCabe-Thiele diagrams, Murphree efficiency equations, and tray compositions will be used to determine the efficiency of the column. Methods:
Distillations columns are used to separate different components of a mixture based on the differences in the boiling points of such species. The components used in the experiment, water and ethanol, have boiling points of 100 C and 78 C, respectively. The mixture of water and ethanol forms an azeotrope, meaning the composition of the vapor and the composition of the liquid are directly proportional. The use of an optimum number of trays in a separation column can increase efficiency and purity of the separated components. The methods and theory given in the experiment guide were used. °
°
Pre-Lab Questions:
1) The flooding velocities at the bottom of the column and at the top of the colmn were 3.01 m/s and 1.31 m/s, respectively. 2) Flooding Percentages Steam Flow Rates (kg/min)
0.5 0.4313
0.8 0.!"083!
1 0.8!354!
1.25 1.0"432
3) #$e %irst &art o% t$e col'mn to %lood will e towards t$e to& since *a&or entrains li+'id in its %low toward t$e to& o% t$e col'mn (Pless et al. 2002). From t$ere %looding will s&read. #$is answer was con%irmed , e-&erimental res'lts t$e %looding *elocit, (0."0 kg/min) is closer to t$e *al'e &redicted , calc'lating %or et$anol t$an t$e *al'e &redicted , calc'lating %or water.
4) s t$e steam rate is increased t$e *a&or *elocit, and %low '& t$e distillation col'mn increases restricting t$e %low o% li+'id down t$e col'mn. #$is res'lts in t$e increase o% &ress're dro& (P) across t$e col'mn. Flooding occ'rs w$en t$e internal *a&or rate is so $ig$ t$at t$e li+'id is 'nale to %low down t$e col'mn. $en %looding occ'rs in t$e distillation col'mn t$ere is a *er, large &ress're dro& (P) on t$e P c'r*e.
5) ntrainment is de%ined as t$e entra&ment o% one s'stance , anot$er s'stance. n t$e conte-t o% t$e e-&eriment *a&or at $ig$ rates entrains t$e downward%lowing li+'id. n com&arison downcomer %looding occ'rs w$en t$e li+'id acks '& into t$e downcomer d'e to a large &ress're dro& across t$e tra,. $en t$e ack'& li+'id in t$e downcomer e-ceeds t$e tra, s&acing li+'id acc'm'lates on t$e tra, ao*e. 8) McCabe Thiele Plots a. Total reflux- 4 theoretical stages b. Murphee efficiency of 0.82 – theoretical stages
c. Reflux Ratio of 1.8 – 6 theoretical stages
Total Refux 1.20
1.00
0.80 Equilibrium Line 45 degree line
0.60
0.40
0.20
0.00 0.00
0.20
0.40
0.60
0.80
1.00
1.20
Murphree Liquid Eciency o 0.82 1.20
1.00
0.80 Equilibrium Line 45 degree line
0.60
0.40
0.20
0.00 0.00
0.20
0.40
0.60
0.80
1.00
1.20
Refux Ratio o 1.8 1.20
1.00
Equilibrium Line
0.80
45 degree line Rectifying Line 0.60
Stripping Line q-Line
0.40
0.20
0.00 0.00
0.20
0.40
0.60
0.80
1.00
1.20
Appendices Appendix A: Safety Overall Hazard Analysis Description/ Details of steps in activities sage o% et$anol %or distillation e-&eriment
Hazards
Possible accidents/ consequences
Existing Risk ontrol
Fire/ e-&losi*e $a6ard
7a, res'lt in a %ire or e-&losion t$at ma, ca'se 'rns ot$er in'ries and e*en deat$.
1) 9onning o% PP s'c$ as sa%et, goggles la coats and $ard $ats. 2) :ooling water $a*e e %lowing e%ore t$e steam *al*e is o&ened. 3) ;oting location
o% man'al steam *al*es and main s$'to%%s in t$e e*ent o% an emergenc,.
7a, ca'se 'rns and ot$er in'ries. Proectiles %l,ing at $ig$ s&eed in t$e e*ent o% an e-&losion ma, $it o&erators.
9istillation col'mn -&losion or ma, e s'ected cracking o% t$e to o*er&ress're col'mn d'e to $ig$ (e-cessi*e &ress're &ress're. e,ond w$at t$e col'mn is designed %or).
7a, ca'se 'rns and ot$er in'ries. Proectiles %l,ing at $ig$ s&eed in t$e e*ent o% an e-&losion ma, $it o&erators.
=andling o% $ot *al*es or s'r%aces o% $ot oects. ccidental contact wit$ steam &i&es.
>'rn $a6ard
7a, ca'se *ar,ing degrees o% 'rn in'ries.
:liming t$e col'mn stairs
S$ar& edges
7a, ca'se c'ts or lacerations.
=andling o%
lectrical $a6ard
lectroc'tion and
1) 9onning o% PP s'c$ as sa%et, goggles la coats and $ard $ats. 2) ns'ring &ress're *al'es are a&&ro&riatel, monitored and wit$in t$e sa%e limits. 3) ns're c,linder is &ro&erl, mo'nted and c$ained. 1) :ol'mn is &rotected against o*er&ress're , &ress're relie% de*ices s'c$ as relie% *al*es. 2) 9onning o% PP s'c$ as sa%et, goggles la coats and $ard $ats. 9onning o% PP as well as t$ick glo*es. >e alert w$en in close &ro-imit, o% steam &i&es and ot$er $ot s'r%aces. se care w$en climing t$e col'mn stairs. >e care%'l not to ack into stairs w$en working 'nder t$em. :$eck %or an,
electrical $a6ard d'ring e-&eriment and data collection &'r&oses.
electric s$ocks.
damaged electrical e+'i&ment or wires and an, li+'id &ools near electrical connections.
!"D" #Et$anol% Description& :olorless clear li+'id wit$ a mild odor.
Flammale li+'id and *a&or. Flas$ &oint ? 1!.!@:. 7olec'lar weig$t ? 4!.0414 g/ mole >oiling &oint (1 atm) ? 8@: 7elting &oint ? 114.1@: Sol'ilit,A 7iscile Healt$ Effects& :a'ses se*ere e,e irritation and moderate skin irritation w$en coming in contact.
ngestion ma, ca'se gastrointestinal irritation wit$ na'sea *omiting and diarr$ea. 7a, ca'se central ner*o's s,stem (:;S) de&ression c$aracteri6ed , e-citement %ollowed , $eadac$e di66iness drowsiness and na'sea. :a'ses res&irator, tract irritation di66iness or s'%%ocation w$en in$aled. 7a, $a*e an ad*erse re&rod'cti*e and %etal e%%ects in $'mans. Prolonged e-&os're ma, also ca'se li*er kidne, and $eart damage. 'irst aid& For e,e contact remo*e an, contact lenses and immediatel, %l's$ e,es wit$ &lent,
o% water %or at least 15 min'tes.
Cee& awa, %rom so'rces o% ignition and contact wit$ o-idi6ing materials. Store in a cool dr, well*entilated area. !"D" #)ater% Description&
:olorless odorless li+'id 7olec'lar weig$t ? 18.02 g/ mole &= (1D soln/water) ? (;e'tral) >oiling &oint (1 atm) ? 100@: (212@F) Healt$ Effects& ;oncorrosi*e %or skin nonirritant %or skin. ;onsensiti*e %or skin. ;on&ermeator
, skin. ;onirritating to t$e e,es. ;on$a6ardo's in case o% ingestion. ;on $a6ardo's in case o% in$alation. ;onirritant %or l'ngs. ;onsensiti*e %or l'ngs. ;oncorrosi*e to t$e e,es. ;oncorrosi*e %or l'ngs. 'irst aid& ;ot a&&licale "torage ( Handling& ;ot a&&licale
Appendix B: References
Friedman, K. (2015, Summer). Distillation Operation Experiment . Lab Handout ChE 264, The University of Texas at Austin. ook :om&an, ;ew ork. 7c:ae . G. Smit$ H. :. I =arriott P. (2005). nit B&erations o% :$emical ngineering (t$ ed.). >ostonA 7coca Raton FG.
Appendix C: Sample Calculations Flooding Velocity:
Flooding velocity calculation at the bottom of the distillation column: Assumption: Pure Water Physical Properties
V F =C F
√
( ρ L− ρG ) ρG
Where:
VF = Flooding Velocity (m/s) CF = Empirical Constant (m/s) ρ L = Liquid Density (g/cm 3)
ρG
C F =0.075
= Vapor Density (g/cm 3)
m g ρ =0.95 3 s L cm
Vapor density calculation using the ideal gas law: Assumption: Pure Ethanol Physical Properties
P × MW ρG = R × T
( 1 atm ) ρG =
(
V F =
0.08206
(
m 0.075 s
(
18.02
L∙atm mol∙K
)√
)(
g mol
)
=0.5885
)
373.15 K
( 0.95−5.89 × 10 )
g g −4 =5.89 × 10 3 L cm
−4
−4
=3.01
5.89 × 10
m s
Flooding velocity calculation at the top of the distillation column:
( 1 atm ) ρG =
(
0.08206
(
46.07
L∙atm mol∙K
)(
g mol
)
=1.597
)
351.55 K
g g −3 =1.597 × 10 3 L cm
(
m V F = 0.059 s
)√
( 0.789−1.597 × 10 ) −3
−3
1.597 × 10
= 1.31
m s
Steam Flow Rates:
Steam flow rate calculation using an energy balance around the reboiler at 50% flooding:
H vap,ethanol V top m steam = H vap, steam Where:
V top =
fA ρ G V F MW
H vap,ethanol ×f × A× ρG × V F msteam = H vap, steam × MW
Therefore:
Where: f = Fraction of Flooding (unitless) A = Column Area (cm 2) ρG = Density of Ethanol Vapor (g/cm 3) VF = Flooding Velocity (cm/s) MW = Molecular Weight of Ethanol (g/mol)
9674
m steam =
cal g cm −3 2 2 × 0.5 × × 7.5 c m × 1.597 × 10 × 131 3 gmol s cm 9718
msteam =0.432
!g m"n
Average Molecular Weight:
cal g × 46.07 gmol mol
×
(
1.081
!g∙s mol∙m"n
)
Average Molecular Weight calculation of the feed stream:
# ¿ $
W " M ¿ ¿ ¿
M W fee% =∑ ¿
Where: $
# " = mass f&act"onof component " ∈ st&eam $
[|
M W fee% =
0.32 g ethanol
g fee%
|
mol ehtanol 46.07 g ethanol
|| +
0.68 g'ate&
gfee%
|
Average Molar Flow Rate:
Average Molar Flow Rate calculation of the feed stream:
n´ $=m´ $ ( M W
$
−1
)
Where: n´ $ =mola& flo' &ateof st&eam $ $
´ = mass flo' &ate of st&eam $ m
|
n ´fee%=
35 !g fee%
m"n
|
!gmo l fee% 22.38 !g fee%
|
=1.56
|]
−1
mol'ate& 18.02 g'ate&
!gmo l fee% m"n
Average Mole Fraction:
Average Mole Fraction calculation of the feed stream:
= 22.38
gfee% mo l fee%
# ¿ $
W " M ¿ $ −1 ¿ " ∙ ( ¿¿ " ] ¿
# ¿ $
W " M ¿ $ −1 ¿ " ∙ ( ¿¿ " ] ¿
# ¿ $
W " M ¿ ¿ ¿ ¿ ¿ $
( " =¿
F
( ) =
(|
0.32 ! g ethanol
! g fee%
|
!gmol ethanol 46.07
! g ethanol
|)(
22.38
! g fee% !gmo l fee%
)
=0.16
!gmol ethanol !gmol fee%
