Post on 19-Oct-2020
Modeling Mass Transfer Performance of Packings
Di Song
Gary Rochelle & Frank Seibert
University of Texas at Austin
Contents
Introduction
Model of ae
Model of kL
Model of kG
Conclusions
2
• Mass transfer & Packings
• Why is µL important
• Methods & SRP database
• Scale-up: secondary area
• Effect of µL
• Scale up: packing height
• Effect of µL
• Significance of this work
• Recommendations
Contents
Introduction
Model of ae
Model of kL
Model of kG
Conclusions
3
• Mass transfer & Packings
• Why is µL important
• Methods & SRP database
• Scale-up: secondary area
• Effect of µL
• Scale up: packing height
• Effect of µL
• Significance of this work
• Recommendations
Two-film theory 4
CO2
Bulk liquidLiquid filmGas filmBulk gas
PCO2Pi
CO2
[CO2]i
[CO2] or P*CO2
Rxn. film
5Two-film theory
6Two-film theory
7Two-film theory
8Two-film theory
9Two-film theory
Packings 10
Random Structured Hybrid
Since 1890s 1960s >2000
Cost Low High High
Efficiency Moderate High High
Capacity Moderate High Medium
Shape
Mass transfer in amine capture process
11
Flue Gas
DCC (kGae)Absorber(kL & ae)
WW(kGae)
Stripper (kLae)
C Free Gas
CO2 for Compr.
Amine
Mass transfer in amine capture process
12
Flue Gas
DCC (kGae)Absorber(kL & ae)
WW(kGae)
Stripper (kLae)
C Free Gas
CO2 for Compr.
Amine
Reliable packing model is critical for design
μL is critical to solvent selection
• Heat transfer
• h Q
• Mass transfer
• Diffusion of CO2 through reactive layer
• Diffusion of free amine to L-G interface (surface depletion)
• Diffusion of loaded amine back to bulk liquid (P*CO2)
• Liquid turbulence
13
µSolvent ≫ µH2O
14
Amine soln.(α = 0.4) H2O 7m MEA 11m MEA 5m PZ 8m PZ
μ @ 40 ̊C(cP) 0.65 2.4 4.0 3.6 11.4
Water lean solvent.
Alkylcarbonates: IPADM-BOL
Switchable Carbamates:
TESA
Aminosilicones: GAP-0/TEG
Nonaqueous organic amine blends: AMP/PZ + EGME + 15 wt % H2O
μ @ 40 ̊C(cP) ~ 130 cP ~800 cP ~1300 cP ~30 cP
μL affects kL in two ways (how much?)15
• α – Direct influence via the turbulence of liquid
• βγ – Indirect influence via D of mass transfer species
kL = C1· μα·Dβ
D = C2· μγkL (kLa) = C3· μα+βγ
μL affects ae?
Pilot packed column16
Blower180-450 ACFM
Storage Tank250 gal
Pump 2.5-30 gpm/ft2
Liquid Outlet
Liquid Inlet
Bypass
Air Inlet
Air Outlet
H: 25 ftZmax: 10 ft
I.D.: 16.8 in
F40 DistributorTrutna Collector
Chemical systems17
• kG: Trace SO2/NaOH/H2O
• kL: Air/Toluene/H2O
• ae: Ambient CO2/NaOH/H2O
Chemical systems18
• kG: Trace SO2/NaOH/H2O
• kL: Air/Toluene/H2O
• ae: Ambient CO2/NaOH/H2O + glycerol
+ glycerol (1–70 cP)
Chemical systems19
• kG: Trace SO2/NaOH/H2O
• kL: Air/Toluene/H2O
• ae: Ambient CO2/NaOH/H2O
Kinetic model based on WWC exp.
+ glycerol
+ glycerol (1–70 cP)
SRP database20
• 21 Structured Packings
MellaPak®, Montz-Pak®, GT-Pak®, Flexipac®, etc
• 12 Random Packings
Pall Ring, IMTP®, Raschig-SuperRing®, etc
• 4 Hybrid Packings
Raschig-SuperPak®, Hiflow Plus®
• 1 Gauze Packing
Contents
Introduction
Model of ae
Model of kL
Model of kG
Conclusions
21
• Mass transfer & Packings
• Why is µL important
• Methods & SRP database
• Scale-up: secondary area
• Effect of µL
• Scale up: packing height
• Effect of µL
• Significance of this work
• Recommendations
Effective mass transfer area: ae22
0
100
200
300
400
500
0 100 200 300 400 500
a e,to
tal(
m2 /
m3 )
aP (m2/m3)
Plastic
Fractional area Φ = 1
M 252Y
M 250YS
Gauze
Structured YStructured X/ZRandomHybrid
Secondary ae
23
Gas
Liquid
5 in.
10 ft.
6 ft.
Secondary ae
24
aWall
aTop
Gas
Liquid
5 in.
10 ft.
6 ft.
aBot
aSecondary = aTop + aWall + aBot
aTotal = ae,packing + aSecondary
Sec. ae is critical to scaling up25
0%
5%
10%
15%
20%
5 10 20 40 80 160
Ratio
to to
tal a
rea
DColumn (in)
Wall area
Bottom area
Top area
Avg. value @ G = 300 ACFM, L = 10, 15, 20 gpm/ft2
M 250Y (10 ft)
M 250Y
ae Model26
𝑎𝑎𝑒𝑒,𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝
𝑎𝑎𝑃𝑃= 1.16 � 𝜂𝜂 � 𝑊𝑊𝑊𝑊 � 𝐹𝐹𝐹𝐹−
120.138
= 1.16 � 𝜂𝜂𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 � 𝜂𝜂𝑚𝑚𝑎𝑎𝑡𝑡𝑡𝑡𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚 � 𝜂𝜂𝑚𝑚𝑙𝑙𝑎𝑎𝑙𝑙𝑚𝑚𝑙𝑙𝑙𝑙 �𝜌𝜌𝐿𝐿𝜎𝜎
� 𝑔𝑔 ⁄1 2 � 𝑢𝑢𝐿𝐿 � 𝑎𝑎𝑃𝑃⁄−3 2
0.138� 𝜇𝜇𝐿𝐿0
ae Model27
𝑎𝑎𝑒𝑒,𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝
𝑎𝑎𝑃𝑃= 1.16 � 𝜂𝜂 � 𝑊𝑊𝑊𝑊 � 𝐹𝐹𝐹𝐹−
120.138
= 1.16 � 𝜂𝜂𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 � 𝜂𝜂𝑚𝑚𝑎𝑎𝑡𝑡𝑡𝑡𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚 � 𝜂𝜂𝑚𝑚𝑙𝑙𝑎𝑎𝑙𝑙𝑚𝑚𝑙𝑙𝑙𝑙 �𝜌𝜌𝐿𝐿𝜎𝜎
� 𝑔𝑔 ⁄1 2 � 𝑢𝑢𝐿𝐿 � 𝑎𝑎𝑃𝑃⁄−3 2
0.138� 𝜇𝜇𝐿𝐿0
Random/hybrid:
𝜂𝜂𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 = 1.34 − 0.26𝑎𝑎𝑃𝑃
250 Plastic:𝜂𝜂𝑚𝑚𝑎𝑎𝑡𝑡𝑡𝑡𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚 = 0.62
Loading zone (ΔP ≥ 400 Pa/m):𝜂𝜂𝑚𝑚𝑙𝑙𝑎𝑎𝑙𝑙𝑚𝑚𝑙𝑙𝑙𝑙 = 1.15
28
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
50 100 150 200 250 300 350 400
Calc
ulat
ed/m
easu
red
a e,to
tal
Measured ae,total (m2/m3)
-20%
+20%
σ~72 mN/m, µ~1 cP
G = 300 ACFM
AAD = 8.9%
ae Model
ae model w/ viscosity 29
-20%
-10%
0%
10%
20%
0.5 2 8 32
Rela
tive
erro
r
µL (cp)
Avg. value @ G = 300 ACFM, L = 10, 15, 20 gpm/ft2
PEG (Tsai)
Glycerol
Contents
Introduction
Model of ae
Model of kL
Model of kG
Conclusions
30
• Mass transfer & Packings
• Why is µL important
• Methods & SRP database
• Scale-up: secondary area
• Effect of µL
• Scale up: packing height
• Effect of µL
• Significance of this work
• Recommendations
Liquid film mass transfer coefficient: kL31
1
2
3
4
5
0 100 200 300 400 500
avg.
k L·µ0.
4 /D0.
5
aP (m2/m3)
Avg. value @ G = 300 ACFM, L = 10, 15, 20 gpm/ft2
Structured YStructured X/ZRandomHybrid
Liquid film mass transfer coefficient: kL32
1
2
3
4
5
0 100 200 300 400 500
avg.
k L·µ0.
4 /D0.
5
aP (m2/m3)
Avg. value @ G = 300 ACFM, L = 10, 15, 20 gpm/ft2
Structured YStructured X/ZRandomHybrid
GTP 350 Y/Z
M 250 X/Y
Scaling packing height (kL)33
0
1
2
3
4
5
0 1 2 3 4 5
k L·µL0.
4 /D0.
5(6
ftpa
ckin
g)
kL·µL0.4/D0.5 (10 ft packing)
Scaling packing height (kL)34
0
1
2
3
4
5
0 1 2 3 4 5
k L·µL0.
4 /D0.
5(6
ftpa
ckin
g)
kL·µL0.4/D0.5 (10 ft packing)
6-10 ft Ratio
Structured 1.29
Hybrid 1.39
Random 1.54
Overall 1.32
Scaling packing height (kL)35
0
1
2
3
4
5
0 1 2 3 4 5
k L·µL0.
4 /D0.
5(6
ftpa
ckin
g)
kL·µL0.4/D0.5 (10 ft packing)
6-10 ft Ratio
Structured 1.29
Hybrid 1.39
Random 1.54
Overall 1.32
Maldistribution is worse for taller bed
Correction = ln ⁄1.32 1ln ⁄6 10
= −0.54
kL Model36
𝑆𝑆𝑆𝐿𝐿 = 0.12 � 𝑆𝑆𝑆𝑆𝐿𝐿0.5 � 𝑅𝑅𝑊𝑊𝐿𝐿0.565 � 𝐺𝐺𝑎𝑎𝐿𝐿⁄1 6 �
𝑍𝑍1.8
−0.54
𝑘𝑘𝐿𝐿 = 0.12 � 𝑢𝑢𝐿𝐿0.565 �𝜇𝜇𝐿𝐿𝜌𝜌𝐿𝐿
−0.4
� 𝐷𝐷𝐿𝐿0.5 � 𝑔𝑔 ⁄1 6 � 𝑎𝑎𝑃𝑃−0.065 �𝑍𝑍
1.8
−0.54
Dependence on µL of kL37
1.E-06
1.E-05
1.E-04
0.5 5 50
k L·aP0.
065 /
(uL0.
565 ·g
1/6 ·ρ
L0.4 )
µL (cP)
Hybrid
Structured
Random
-0.75 predicted in model
G = 300 ACFM
Dependence on µL of kL38
1.E-06
1.E-05
1.E-04
0.5 5 50
k L·aP0.
065 /
(uL0.
565 ·g
1/6 ·ρ
L0.4 )
µL (cP)
Hybrid
Structured
Random
-0.75 predicted in model
G = 300 ACFM
Direct = -0.40
Indirect = -0.35
Universally applicable
System-specific based on D-µ relationship
Comparison to other work: µL39
-100%
0%
100%
200%
300%
400%
500%
0.5 1 2 4 8 16 32 64
Rela
tive
erro
r = (k
Lam
odel
-kLa
exp)
/kLa
exp
µL (cP)
This work
Billet
Rocha
DelftValenz
M 250Y
Contents
Introduction
Model of ae
Model of kL
Model of kG
Conclusions
40
• Mass transfer & Packings
• Why is µL important
• Methods & SRP database
• Scale-up: secondary area
• Effect of µL
• Scale up: packing height
• Effect of µL
• Significance of this work
• Recommendations
Gas film mass transfer coefficient: kG41
0
4
8
12
0 100 200 300 400 500
avg.
k G/D0.
5
aP (m2/m3)
Avg. value @ L = 15 gpm/ft2, G = 180, 300, 450 ACFM
Structured YStructured X/ZRandomHybrid
Gas film mass transfer coefficient: kG42
0
4
8
12
0 100 200 300 400 500
avg.
k G/D0.
5
aP (m2/m3)
Avg. value @ L = 15 gpm/ft2, G = 180, 300, 450 ACFM
Structured YStructured X/ZRandomHybrid
GTP 350 Y/Z
M 250 X/Y
Model of kG43
𝑆𝑆𝑆𝐺𝐺 = 0.28 � 𝑆𝑆𝑆𝑆𝐺𝐺0.5 � 𝑅𝑅𝑊𝑊𝐺𝐺0.62 �sin 2𝛼𝛼
sin 2 × 45°
0.65
𝑘𝑘𝐺𝐺 = 0.28 � 𝑢𝑢𝐺𝐺0.62 �𝜇𝜇𝐺𝐺𝜌𝜌𝐺𝐺
−0.12
� 𝐷𝐷𝐺𝐺0.5 � 𝑎𝑎𝑃𝑃0.38 � sin 2𝛼𝛼 0.65
aeffective = 45° (for random/hybrid packings)
Finer packings are more controlled by kL44
0.001
0.002
0.004
0.008
50 100 200 400
Avg.
kL/
k G@
25
°C
aP (m2/m3)
Baseline: σ ~ 72 mN/m, µ ~ 1 cP
Structured YStructured X/ZRandomHybrid
Contents
Introduction
Model of ae
Model of kL
Model of kG
Conclusions
45
• Mass transfer & Packings
• Why is µL important
• Methods & SRP database
• Scale-up: secondary area
• Effect of µL
• Scale up: packing height
• Effect of µL
• Significance of this work
• Recommendations
Significance of this work46
• Reliable & simple mass transfer models
• Large database & column size, variance of µL
• No packing-specific parameter
•
•
•
𝑎𝑎𝑡𝑡,𝑡𝑡𝑎𝑎𝑝𝑝𝑝𝑝𝑚𝑚𝑙𝑙𝑙𝑙
𝑎𝑎𝑃𝑃= 1.16 � 𝜂𝜂 � 𝑊𝑊𝑊𝑊 � 𝐹𝐹𝐹𝐹−
120.138
𝑆𝑆𝑆𝐿𝐿 = 0.12 � 𝑆𝑆𝑆𝑆𝐿𝐿0.5 � 𝑅𝑅𝑊𝑊𝐿𝐿0.565 � 𝐺𝐺𝑎𝑎𝐿𝐿⁄1 6 �
𝑍𝑍1.8
−0.54
𝑆𝑆𝑆𝐺𝐺 = 0.28 � 𝑆𝑆𝑆𝑆𝐺𝐺0.5 � 𝑅𝑅𝑊𝑊𝐺𝐺0.62 � sin 2𝛼𝛼 0.65
• Selection of packing
• aP, α, material, type
• Selection of solvent
• µL, σ, ρL
• Selection of operating condition
• L, G
• Scale-up of column design
• Secondary effect, liquid maldistribution
Conclusions
kL ∝ µL-0.75 (-0.4 & -0.35)
ae ≠ f (µL)
All types of packings have similar behavior in ΔµL
Z (or L/D) may strongly affect mass transfer
47
Recommendations
Avoid finest packings
Use low µL solvent
Use reliable models (developed in this work)
Thanks!
48
University of Texas at Austin
Di Song (Graduating 10/2017)
dsong@utexas.edu
512-750-1480