Absorber Performance with Piperazine: Importance of Physical Liquid Film Mass Transfer Darshan Sachde and Gary Rochelle Importance of Physical Liquid Film Mass Transfer Darshan Sachde and Gary Rochelle Texas Carbon Management Program The University of Texas at Austin The University of Texas at Austin PCCC3 Regina, Saskatchewan 9/8/2015 9/8/2015
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Absorber Performance with Piperazine:Importance of Physical Liquid Film Mass Transfer
Darshan Sachde and Gary Rochelle
Importance of Physical Liquid Film Mass Transfer
Darshan Sachde and Gary Rochelle
Texas Carbon Management Program
The University of Texas at AustinThe University of Texas at Austin
PCCC3 Regina, Saskatchewan
9/8/20159/8/2015
Overview Modeling Background
Theoretical Basis : Film TheoryTheoretical Basis : Film Theory
Rate-based Parameter Sensitivityl f k k Relative Resistance of kL, kg, reaction rates
Evaluating uncertainty in kLEvaluating uncertainty in kL
Conclusions2
Modeling Framework: Rate Based Absorber Solvent Model :Thermo & Kinetic PZ Model
(“Independence”, Frailie 2014, Aspen Plus® )( p , , p )1. Thermo: e-NRTL regressed to fit experimental data
(amine volatility, VLE, heat capacity, speciation/NMR) y p y p2. Kinetics/Mass Transfer: Rate constants and diffusion
coefficients from wetted wall column data
Packing Mass Transfer Model (Tsai, Wang, Song)1. Regress pilot scale air-water column data 1. Regress pilot scale air water column data kL = f(uL/ap, packing geometry, μ)k = f(u /a packing geometry)kg f(uG/ap, packing geometry) ae = f(uL/ap, ρL, σ)
Aspen Plus® RateSep
Rate Parameter Sensitivity Analysis
Mass Transfer with Fast Chemical Rxn (Film Theory)B lk V Bulk LiquidBulk Vapor Bulk Liquid
PCO2,Bulk[Am] Bulk
[CO2]B lkVapor Film Rxn Film Liquid Film
[CO2]Bulk
Represents reaction kinetics;
Influenced by kL,Reactants 5
Rate Parameters via Film Theory
Coupled with
kL,Reactants
6
Film Theory (Pseudo-First Order)
At Pseudo-First order conditions (fast reactions, not ( ,instantaneous): kg” = kg’ (Total liquid film resistance) kg = kg (Total liquid film resistance) kL,Reactants & kL,Products are not limiting
E b b d f f (MEA PZ) Expect over most absorber conditions for fast amines (MEA, PZ) Explicit calculation of liquid film resistance 7
Rate Parameter Sensitivity: GOALS Identify Controlling Resistance As a function of position in columnAs a function of position in column For a wide range of operating conditions (CO2
Conclusions Liquid side physical mass transfer resistance dominant Liquid-side physical mass transfer resistance dominant
across most of absorberH ld ti diti f 8 PZ (L di Holds across operating conditions for 8 m PZ (Loading,
Intercooling, CO2 concentration)Diminishing benefits of enhancing kinetics aloneDiminishing benefits of enhancing kinetics alone
Bounding Case (5 x k ) approaches PFO Bounding Case (5 x kL) approaches PFO 80% of absorber is reaction controlledRi h d till hibit i ifi t k i tRich end still exhibits significant kL resistance
P D l t O t iti ith PZ Process Development Opportunities with PZReduce solvent viscosity (5 m PZ) – Pilot Plant Results
N l d i (hi h i i l l )Novel contactor design (high intensity e.g., solvent recycle)21
7.5 0.220 RiConditionsCoal‐Fired Boiler (14 7% CO )
6.0 0.238
ich LoadCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.
CO2 Removal = 90%
4.5l/mol)
No Intercooling 0.267
ding (m
4.5
/G (m
o 0.267
mols CO
3.0L/ 0.326
2 /mols1.05*LMIN
1.5 Isothermal (40°C) 0.501
alk.)
0.00 25 50 75 100 125
Total Packing Metal Area/G ( m2/mol/s) 24
7.5 0.220 RiConditionsCoal‐Fired Boiler (14 7% CO )
6.0 0.238
ich LoadCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.
CO2 Removal = 90%
4.5l/mol)
No Intercooling 0.267
ding (m
4.5
/G (m
o 0.267
mols CO1.8*LMIN
3.0L/ 0.326
2 /mols
1.2*LMIN 1.05*LMIN
1.5 Isothermal (40°C) 0.501
alk.)
0.00 25 50 75 100 125
Total Packing Metal Area/G ( m2/mol/s) 25
1.00Conditions
Coal‐Fired Boiler (14.7% CO2)G 0 l CO / l lk
26
0.80
eter) kL 1.05*LMIN
LLDG = 0.15 mols CO2/mols alk.CO2 Removal = 90%
0.60parame
0 40x)/dln(
0.40
CO2Flux
0.20dln(C
1.05*LMIN
0.00
1.05 LMIN
0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM
1.00Conditions
Coal‐Fired Boiler (14.7% CO2)G 0 l CO / l lk
27
0.80
eter) kL 1.05*LMIN
LLDG = 0.15 mols CO2/mols alk.CO2 Removal = 90%
0.60parame
1.2*LMIN
0 40x)/dln(
0.40
CO2Flux
0.20dln(C
1.2*LMIN
1.05*LMIN
0.00
1.05 LMIN
0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM
1.00Conditions
Coal‐Fired Boiler (14.7% CO2)G 0 l CO / l lk
28
0.80
eter) kL 1.05*LMIN
LLDG = 0.15 mols CO2/mols alk.CO2 Removal = 90%
0.60parame
1.2*LMIN
0 40x)/dln(
1.8*LMIN
0.40
CO2Flux
1.8*LMIN
0.20dln(C
1.2*LMIN
1.05*LMIN
0.00
1.05 LMIN
0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM
Rate Parameters via Film Theory
kL,ReactantsRepresents
reaction “film”
29
Pilot Plant Results: Solvent Viscosity EffectsEffects
5 m PZ vs. 8 m PZ: Absorber Performance
T t RPZ
CSolvent R t
Gas R t
Lean Loading ( l
P*CO2@
Rich Loading ( l CO2Test Run Conc.
(molal)Rate(GPM)
Rate(ACFM)
(mol CO2/mol alk.)
@40°C(Pa)
(mol CO2/mol alk.)
2Removal
) )
19 5
14 5000.235 107 0.361 80%
14 8 0 236 85 0 342 75%14 8 0.236 85 0.342 75%
28 5
14 3500.238 114 0.352 96%
15 8 0.239 91 0.328 93%
33 5
10 2 3500.221 83 0.395 94%
3 10.2 35016 8 0.225 68 0.344 91%
5 PZ i ifi l f 8 PZ5 m PZ significantly outperforms 8 m PZ31
12Conditions
Coal Fired Boiler (14 7% CO )
9
Coal‐Fired Boiler (14.7% CO2)5 m PZ: LLDG = 0.18 mols CO2/mols alk.8 m PZ: LLDG = 0.20 mols CO2/mols alk
P*CO2 @ 40C = 0 04 kPa9
l/mol) P CO2 @ 40C = 0.04 kPa
CO2 Removal = 90%In‐and‐Out Intercooling
6
/G (m
oL/
5 m PZ
38 m PZ
00 20 40 60 80
Total Packing Metal Area/G ( m2/mol/s) 32
12
99
/mol)
6
G (m
ol/
l b dL/G
5 m PZEquilibrium Limited
Capacity
38 m PZ
00 20 40 60 80
Total Packing Metal Area/G ( m2/mol/s) 33
12
9Mass Transfer Limited
C it9
/mol) Capacity
6
G (m
ol/
L/G
5 m PZ
38 m PZ
00 20 40 60 80
Total Packing Metal Area/G ( m2/mol/s) 34
Conclusions: March 2015 Pilot Plant Campaign5 PZ i ifi l f d 8 PZ d i 5 m PZ significantly outperformed 8 m PZ during campaign Enhanced rates of 5 m PZ allowed for higher operating solvent
capacity despite inherently lower capacity of solvent
35
36
Rate Parameter Sensitivity: METHOD Base Case Conditions (8m PZ) : NGCC (4% CO ) Coal (13% CO ) Steel (27% NGCC (4% CO2), Coal (13% CO2), Steel (27%