gps technology for gas separations
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A Novel Gas Pressurized Stripping (GPS) Technology for CO2 Separation
Fei Yi, Ph.D. Senior Chemical Engineer
Carbon Capture Scientific, LLC.
June 9, 2015
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Company Background
A start-up company located in Pittsburgh, PA Two granted patents (US 8425655 B2, US 8512445 B2) Bench-scale development funded by the Department of
Energy / National Energy Technology Laboratory Chemical engineers/scientists with strong expertise in
process design, simulation and optimization Technology development pathway -- from thermodynamic
analysis, to process simulation, to bench scale prototyping
2
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An Generic Process for CO2 Separation
M+CO2! N
Ignore all the driving force for heat and mass transfer 3
N!M+CO2
40C
-H
120C
H
P1a=0.14 atm
P2=80 atmP1b=0.014 atm
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2CO2
RTH-
dTdlnP-
dTdlnK
=
HNCOM 2 +CO2 Capture/ Regeneration:
Vant Hoff Equation:
Equilibrium constant expression:
Thermodynamics of the Generic Process
2COMM
NN
P1
xxK
=
4
-
5
222
2
lnlnlnln
lnlnlnlnlnln
RTH
TP
TP
TPxx
dTKd
COCOMN
COMMNN
=
=
+=
For liquid solvent, equilibrium constant:
)11()ln()ln(12
12 TTRHPP =
Assuming constant H and integrate:
Integrated vant Hoff Equation
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6
According to the integrated vant Hoff Equation and ignore activity coefficient change with temperature:
)11()ln()ln(12
12 TTRHPP =
Minimum Heat of the Generic Process
And minimum heat requirement can be calculated for different temperature ranges.
12
2112 )]ln()[ln( TT
TTPPRH
=
We have:
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1
10
100
1000
10000
100000
40 60 80 100 120 140 160 180 200
P 2/P
1
T2 oC (T1=40 oC)
130
120
110
100
90
80
70
60
50
40
30
20
H=kJ/mol
7
)11()ln()ln(12
12 TTRHPP =
Required pressure ratio
)11()ln()ln(12
12 TTRHPP =
P2
Graphic Display of Integrated vant Hoff Equation
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( )
)kgCO/kJ(2060)molCO/kJ(655.90637.34018.56
)PP(P)Pln(P)Pln(PP1)Pln(
TTTTRH
22
a1b1a1a1b1b1a1b1
212
21average
==+=
=
Minimum Heat Requirement PC CO2 Capture
8
For coal fired power plant: Initial P: P1a= 0. 014, P1b = 0.14atm Product P: P2=80 atm
(90% of CO2 removal) Absorption T: T1=313K Stripping T: T2=393K
And the heat of reaction required:
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9
Strip
ping
C
olum
n
Raw Flue Gas
Clean Flue Gas Pure CO2
Steam
Cross Heat Exchanger
ReboilerRich Solution
Lean Solution
Hot Lean Solution
Hot Rich Solution
Abs
orpt
ion
Col
umn
Makeup MEA
Cooling
Qtotal
Hrich
Hlean
PH2O/PCO2 = ~0.8/1.1=0.8
P=~2 atm
T~120 C
T~95 C
Conventional Amine-Based Absorption/Stripping Processes
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strippingreactionsensibletotal QQQQ ++=
Heat Components of the Conventional Process
reactionreaction HQ =
OH
stripperthe
ofTopCO
OHstripping HP
PQ
2
2
2
=
LoadingTTC
Q hotrichhotleanpsensible
=)(
Little contribution to the process
All contributes to the process
Should be minimized
Should be minimized
Maximize its potential
No contribution to the process
10
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11
Issues with Conventional Stripper
Stripping Column
CO2 Product
Steam
Reboiler
Qtotal
P=~2 atmT=120 C
T=~95 C
Lean Solution
Rich Solution
q Water vapor is used as stripping gas, thus operating pressure is limited by the vapor pressure of the lean solution at the reboiler temperature
T=~95 C
T=120 C
P=~2 atm
PH2O/PCO2 = ~0.8/1.0=0.8
q Water vapor is also used as a heat carrier which leads to a temperature gradient along the column
q Low operating pressure results in a high ratio of PH2O /PCO2 at the top of the stripper
Consequences: Low thermal eciency High compression work
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The Novel Gas Pressurized Stripping (GPS) Column
12
q Adding a high pressure stripping gas stream into the column Eliminating water as stripping gas Enables high operating pressure
q Adding side heaters to provide heat Eliminates the necessity of using water
vapor as heat carrier Reduces temperature gradient in the
stripper
q Product gas is a mixture of stripping gas and CO2 along with water vapor Increased CO2 partial pressure
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GPS Based Absorption/Stripping Process
13
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Advantages of the GPS Based Processes
14 14 14
qUses commercial off-the-shelf technology Proven unit operations
Suitable for large scale applications such as power plants
qHigh stripping pressure Low stripping heat
qHigh thermal efficiency Reduced mechanical CO2 compression work
qFlexible Applicable to solvents with different heat of reaction
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GPS and Conventional Column Efficiencies
Items Conventional Stripper GPS Column
Reaction Heat kJ/kgCO2 1870 1400
Stripping Heat kJ/kgCO2 690 170
Stripping Column Total Heat kJ/kgCO2 2560 1570
Minimum Heat Required kJ/kgCO2 1047 1377
Average Pressure in Absorption Column (atm) 0.049 0.049
Average Pressure in Stripping Column (atm) 1.8 5.60
Stripping Column Efficiency (%) 41* 87*
15
* does not include sensible heat
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Current and Future Performance of GPS Processes
Process Baseline MEA Current
GPS Process Future
GPS Process
Operating Pressure (atm) 1.8 ~10 ~10 Reaction Heat (kJ/kgCO2) 1870 1680 1350
Sensible Heat (kJ/kgCO2) 990 220 200
Stripping Heat (kJ/kgCO2) 690 182 150 Total Heat (kJ/kgCO2) 3550 2082 1700 Electricity Equivalent (kWh/kgCO2) 0.29* 0.13 0.08 Other load (kWh/kgCO2) 0.04 0.04 0.03
Compression Work (kWh/kgCO2) 0.09 0.05 0.07
Electricity Equivalent (kWh/kgCO2) 0.42 0.22 0.18
Energy Penalty to SPC Plant (%) 30 16 15
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*No back pressure turbine was used
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Test at NCCC
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6 atm in stripper 90% removal in absorber 95% purity CO2 from stripper
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