NTNU
30.03.2012 T. Gundersen Slide no. 1
Thermodynamics and Innovative Design for Energy Efficiency and Carbon Capture
by
Truls Gundersen Department of Energy and Process Engineering
Norwegian University of Science and Technology (NTNU) Trondheim, Norway
with important contributions from
Audun Aspelund, PhD, 20 March 2012 Chao Fu, PhD, September 2012
Danahe Marmolejo Correa, PhD, Spring 2013
Chemical Engineering Department Seminar Carnegie Mellon University, Pittsburgh, 27 March 2012
NTNU
30.03.2012 T. Gundersen Slide no. 2
Comments from a “UK University” October 1988
Promoting Optimization (Math Programming) was quite challenging in those Days !
NTNU
30.03.2012 T. Gundersen Slide no. 3
Thermodynamics and Innovative Design for Energy Efficiency and Carbon Capture
is not about Architecture (the Stata Center at MIT)
NTNU
30.03.2012 T. Gundersen Slide no. 4
BIGCCS BIGCCS Director: Mona J. Mølnvik BIGCCS Board Chair: Nils A. Røkke
SINTEF Energy Research NTNU Coordinator: Truls Gundersen
International CCS Research Centre
Budget 80 MUSD over 8 years
> 20 PhDs and > 10 Post.docs
2009-2016 Objectives:
1. Reduce CCS Cost by 50% 2. CO2 Capture Rate of 90% 3. Fuel-to-Power Penalty ≤ 6 % pts
Innovations are required
NTNU
30.03.2012 T. Gundersen Slide no. 5
Ref.: IPCC, Climate change 2007: The physical science basis
Climate Change and CO2 Emissions
Mark Twain:
”Climate is what to expect, weather is what you get”
3 Main Options:
1. Energy Efficiency 2. CO2 Capture & Storage 3. Renewable Energies
NTNU
30.03.2012 T. Gundersen Slide no. 6
Thermodynamics and Innovative Design for Energy Efficiency and Carbon Capture
Obvious link: Thermodynamics & Energy Efficiency
Greek-to-English: Therme = Warm = Heat (Thermie = Calorie) Dynamis = Force = Power
Heat & Power
Physics
Chem. Engng.
Mech. Engng.
NTNU
30.03.2012 T. Gundersen Slide no. 7
Content of the Presentation 2 “subambient” Processes
♦ LNG and ASU (Air Separation Units) Scenario: 2 types of Power Stations
♦ Supercritical pulverized Coal based Plant ♦ Combined Cycle Natural Gas based Plant ♦ Both of the Oxy-combustion type for CO2 Capture
Design Methodologies ♦ Thermodynamics based (Pinch & Exergy Analyses) ♦ Optimization based (Math Programming & Superstructures)
Examples will focus on Energy Efficiency and CCS Innovations will be discussed
♦ Patent Application for new ASU cycles ♦ Liquefied Energy Chain with offshore LNG
Round up with a Summary
NTNU
30.03.2012 T. Gundersen Slide no. 8
Combined Transport of Natural Gas and CO2
Oxyfuel Power Plant
CO2 Liquefaction
Natural Gas Liquefaction
Air Separation ASU
NG
Air
LIN LNG
W
CO2
NG
LCO2
O2
LNG
H2O
Audun Aspelund: A Liquefied Energy Chain (LEC)
NTNU
30.03.2012 T. Gundersen Slide no. 9
Why is the PRICO Process so inefficient? Danahe Marmolejo Correa: Exergy Analysis & LNG
K-101
K-102
VLV-101
VLV-201
Mixed Refrigerant (1)@ 294 K & 4 bar
2a@ 346 K & 10 bar
2b@ 306 K & 9.8 bar
2@ 361 K
& 24.4 bar
3@ 305 K
& 24.2 bar
5@ 108 K & 4.2 bar
Natural Gas (6) @ 300 K & 50 bar
7 @ 113 K & 49.8 bar
LNG (8)@ 109 K & 1.2 bar
4@ 111 K & 24 bar
COND-101INTERC-101
HX-101
NTNU
30.03.2012 T. Gundersen Slide no. 10
Current State-of-the-Art:
Chao Fu: ASU Cycles with up to 20% Energy Savings
Linde’s Classical Coupled Column Design
NTNU
30.03.2012 T. Gundersen Slide no. 11
Recuperative Vapor Recompression Cycle - Patented
Chao Fu: ASU Cycles with up to 20% Energy Savings
NTNU
30.03.2012 T. Gundersen Slide no. 12
A short Tutorial on Exergy What is Exergy?
♦ ”The Maximum Amount of Work that can be produced if a “System” is brought to Equilibrium with its natural Environment through Reversible Processes”
♦ Equilibrium here refers to Composition, Pressure, Temperature, Velocity, Gravitational Level, etc.
Is Exergy related to Entropy? ♦ They are “inverse” properties ♦ Entropy is a measure of disorder (chaos) ♦ Entropy Production in processes due to Irreversibilities is
Equivalent to Exergy Losses (and Lost Work) Why use Exergy?
♦ Energy Forms have different Qualities, i.e. Exergy ♦ Subambient Refrigeration Compr. Work Exergy ♦ But: Exergy and Cost are often (not always) in Conflict
NTNU
30.03.2012 T. Gundersen Slide no. 13
The Exergy of Heat
ηmax as function of TH
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0 200 400 600 800
TC = 0ºC
TC = 15ºC
TC = 25ºC
Without 1st Law Losses:
Wcycle = QH – QC
Without 2nd Law Losses:
(QC /QH) = (QC /QH)rev = TC /TH Thermal Efficiency:
Carnot Efficiency:
Exergy of Heat:
NTNU
30.03.2012 T. Gundersen Slide no. 14
Using Exergy in Subambient Processes?
@ 298 K (25°C) & 50~70 bar
@ 109 K (-164°C)
& 1 bar
Work
&
Liquefaction
NTNU
30.03.2012 T. Gundersen Slide no. 15
Exer
gy
Flow Exergy
Carried by Matter
Disordered
Chemical
Reactional
Concentrational
Thermo-mechanical ETM
Temperature part ET
Pressure part Ep
Ordered
Mechanical
Kinetic
Potential
Electrical
Electrostatic
Electrodynamic
Nuclear
Carried by Energy
Disordered
Heat EQ
Radiation
Ordered Electrical
Non-flow Exergy
1st class: Open/Closed Systems
2nd class: Carrier
3rd class: Energy Randomness
4th class: Origin
Exergy Parts or Components Classification &
Decomposition of Exergy
D. Marmolejo-Correa, T. Gundersen, ”A Comparison of Exergy Efficiency Definitions with focus on Low Temperature Processes”, submitted to Energy, October 2011.
NTNU
30.03.2012 T. Gundersen Slide no. 16
Classification of Exergy Types
Exergy
Physical Chemical
MechanicalThermo-mechanical
Kinetic Potential Temperaturebased
Pressurebased
Mixing &Separation
ChemicalReaction
Kotas T.J., The exergy method of thermal plant analysis, Krieger Publishing Company, Florida, USA, 1995.
Bejan A., Tsatsaronis G. and Moran M., Thermal design and optimization, Wiley, New York City, 1996.
NTNU
30.03.2012 T. Gundersen Slide no. 17
Our Modest Contributions to Exergy Discussed the Various Classifications
♦ OK, it is only a matter of words, but?
Looked for Ways to Standardize Terms and Definitions Illustrated the importance of Decomposition
♦ Explains behavior of Compressors/Expanders above/below T0 ♦ Results in Exergy Efficiencies that measure Design Quality
Discussed various Exergy Efficiencies ♦ Compared existing ones applied to LNG Processes ♦ Proposed a new Exergy Efficiency based on Sources & Sinks
New “Exergetic” Temperatures (beyond Scope here) New Graphical Diagrams and Representations New Targeting Procedure for Exergy
NTNU
30.03.2012 T. Gundersen Slide no. 18
0.0
0.5
1.0
1.5
2.0
0 1 2 3 4 50Dimensionless Temperature, T T
Exer
gy ra
tio o
f Hea
t, EQ
/ Q
.
.
0.5
Special Behavior of Temperature based Exergy Exergy of Heat
0
p
0p
( ),T p
( )0 ,T p
( )0 0,T p
0T
0T T<
Exer
gy, E
.
Thermo-mechanical Exergy of a Stream
NTNU
30.03.2012 T. Gundersen Slide no. 19
Consider Expansion above/below Ambient
5 bar 223K
Assume Isentropic Expansion of Ideal Gas, with Cp = 1.0 kJ/kgK and k = Cp / Cv = 1.4
Ambient T0=298 K
Exp
Exp
5 bar 523K
1 bar 330.2K
1 bar 140.8K
NTNU
30.03.2012 T. Gundersen Slide no. 20
Consider Heat and Exergy Transfer above/below Ambient Temperature
-150
-100
-50
0
50
100
150
200
0 20 40 60 80 100 120
Tem
pera
ture
(°C
)
E (kW)
Hot Stream (exergy) Cold Stream (exergy)
1
2 3
4
2
1
4
3
Source
Sink
Source
Sink
Heat Transfer Exergy Transfer
NTNU
3/30/2012 T. Gundersen Slide no. 21
Process orUnit Operation
ExergyConsumed
ExergyProduced
(Internal)
What is Exergy Efficiency?
D. Marmolejo-Correa, T. Gundersen, ”Challenges in Low Temperature Process Design and Optimization – Using Exergy as the Objective?”, AIChE Mtg., Salt Lake City, November, 2010.
NTNU
3/30/2012 T. Gundersen Slide no. 22
Process orUnit Operation
ExergyConsumed
ExergyProduced
(Internal)
Exergy Efficiency Definitions
D. Marmolejo-Correa, T. Gundersen, ”Exergy Transfer Effectiveness for Low Temperature Processes”, to be submitted to Intl. Jl. of Thermodynamics, 2012.
Brodyansky et al. (1994)
”Exergy Efficiency”
Bejan et al. (1996)
”Exergetic Efficiency”
Kotas (1995)
”Rational Efficiency”
Marmolejo-Correa and Gundersen (2012)
”Exergy Transfer Effectiveness (ETE)”
NTNU
30.03.2012 T. Gundersen Slide no. 23
Applied to the simple PRICO Process
Brodyansky et al. (1994)
Bejan et al. (1996)
Kotas (1995)
Marmolejo-Correa and Gundersen (2012)
NTNU
30.03.2012 T. Gundersen Slide no. 24
Source: BP Statistical Review of World Energy 1990-2010
6.9% annual growth in the last 20 years
LNG as energy carrier: International Trade
NTNU
30.03.2012 T. Gundersen Slide no. 25
Liquefied Natural Gas Value Chain
NTNU
30.03.2012 T. Gundersen Slide no. 26
T. Shukri (Poster Wheeler, UK), ”LNG Technology Selection”, Hydrocarbon Engineering, February 2004
Liquefaction of Natural Gas
NTNU
30.03.2012 T. Gundersen Slide no. 27
Pure Refrigerant
Cycles
Optimized Cascade by Conoco-Phillips
Mixed Refrigerant
Cycles
PRICO by Black &Veatch
Mixed Fluid Cascade (MFC) by Linde-Statoil
Expansion Cycles
Reversed Brayton Cycle
by TGE
Some LNG Processes
Pre-cooled Mixed Refrigerant
(C3MR) by Shell
AP-X by APCI
NTNU
30.03.2012 T. Gundersen Slide no. 28
FV2001, U 14
Natural gas
LNG
Fuel gas
Propane
Ethene
Methane
-40°C
-93°C
-163°C
Cascade Liquefaction Process
NTNU
30.03.2012 T. Gundersen Slide no. 29
Liquefaction using Multicomponent Mixtures
NTNU
30.03.2012 T. Gundersen Slide no. 30
100
150
200
250
300T (K)
ΔH (kW)
R2
R1
R3
Linde and Statoil: Mixed Fluid Cascade
3 Mixed Refrigerants
NTNU
30.03.2012 T. Gundersen Slide no. 31
A new Process Synthesis Methodology utilizing Pressure based Exergy
in Subambient Processes
The Classical Heat Recovery Problem was redefined ”Given a Set of Process Streams with a Supply and Target State
(Temperature, Pressure and the resulting Phase), as well as Utilities for Heating and Cooling Design a System of Heat Exchangers, Expanders, Pumps and Compressors in such a way that the Irreversibilities (or Costs) are minimized”
10 Heuristic Rules were developed Automated by new Superstructure and Math Programming
Aspelund A., Berstad D.O. and Gundersen T. ”An Extended Pinch Analysis and Design Procedure utilizing Pressure based Exergy for Subambient Cooling”, Applied
Thermal Engineering, vol. 27, No. 16, pp. 2633-2649, November 2007.
ExPAnD = Extended Pinch Analysis and Design
NTNU
30.03.2012 T. Gundersen Slide no. 32
Application: A Liquefied Energy Chain (LEC)
Key Features of the “LEC” Concept ♦ Utilization of Stranded Natural Gas for Power Production ♦ High Exergy Efficiency of 46.4% (vs. 42.0% for traditional) ♦ Innovative and Cost Effective solution to the CCS Problem ♦ CO2 replaces Natural Gas injection for EOR ♦ Combined Transport Chain for Energy (LNG) and CO2
Aspelund A. and Gundersen T. ”A Liquefied Energy Chain for Transport and Utilization of Natural Gas for Power Production with CO2 Capture and Storage − Part 1”, Journal of Applied Energy, vol. 86, pp. 781-792, 2009.
NTNU
30.03.2012 T. Gundersen Slide no. 33
NG
0.4
%
CO
2 0.
4%
Combined process for Liquefaction of NG and heating of
LCO2
Combined ship
Combined process for heatin of LNG and liqiefaction of
CO2CCS power plant
NG 100% NG 99.6%NG 100%Power 47.1%
NG
5.4
%
C02
0.7
%
Power
New combined energy-chain: Loss NG during transport 5.8%, CO2 emissions 15.3%, Efficiency 47.1%
CO2 84.7%CO2 84.7%CO2 84.7%
NG 99.6%
CO2 84.7%
NG
94.
2 %
CO
2 14
.2%
LNGLNG LNG
LCO2 LCO2LN2
LNG production LNG ship LNG vaporization
CCS powerplant
LNG production LCO2 ship CO2 Liquefaction Pumping and heating of LCO2
NG 89.9% NG 89.1%
CO2 75.7% CO2 75.7%CO2 75.7%
NG 100%
NG
9.8
%
NG
0.4
%
Power 42.5%
LNG 89.1%
NG
3.6
%
NG
0.4
%
NG
0.3
%
CO
2 9.
8%
0.1
CO
2 %
CO
2 0.
4%
C02
0.4
%
CO
2 0.
3%
CO
2 12
.9%
Power
NG
0.4
%
CO
2 0.
4%
NG 0.4%NG 0.3%
”Conventional” ship-based energychain: Loss NG during transport 14%, CO2 emissions 24.3%, Efficiency 42.5%
CO2 75.7%
NG
85.
2
LNGLNG LNG
LCO2 LCO2LCO2
NTNU
30.03.2012 T. Gundersen Slide no. 34
Developing the Liquefied Energy Chain − Manual and Automated Design Procedures
The ExPAnD Methodology was used ♦ Original version uses 10 Heuristic Rules ♦ Combines Pinch Analysis & Exergy Analysis
Composite & Grand Composite Curves for Idea Generation related to Process Improvements
Exergy Efficiency to Quantify Improvements
♦ Optimization has also been included New Superstructure allows Simultaneous Optimization of Networks with Heat Exchangers, Pumps, Compressors and Expanders using Math Programming
E-2
C-1
E-1
C-3
E-3
C-2
TC1,in TC1,out
TC2,in TC2,out
TH1,inTC3,out
TC3,in
TH1,out
TH2,inTH2,out
TH3,inTH3,out
TC4,in TC4,out
TH4,in
TH4,out
E-2E-2
C-1C-1
E-1E-1
C-3C-3
E-3E-3
C-2C-2
TC1,in TC1,out
TC2,in TC2,out
TH1,inTC3,out
TC3,in
TH1,out
TH2,inTH2,out
TH3,inTH3,out
TC4,in TC4,out
TH4,in
TH4,out
A. Wechsung, A. Aspelund, T. Gundersen and P.I. Barton, ”Synthesis of Heat Exchanger Networks at Sub-Ambient Conditions with Compression and Expansion of Process Streams”, AIChE Jl., vol. 57, no. 8, pp. 2090-2108, 2011.
NTNU
30.03.2012 T. Gundersen Slide no. 35
NG-1
NG-2
LIQ-EXP-102
NG-3
LNG
P-101
N2-2N2-3
N2-1
CO2-1
CO2-2
N2-4
CO2-3
HX-101 HX-102K-100
Offshore Process without Pressure Manipulations
-180
-130
-80
-30
20
0 5 10 15 20 25 30Heat flow [MW]
Tem
pera
ture
[C]
Hot CC Cold CC
HX-101
HX-102
• LIN: 1.75 kg/kgLNG • LCO2: 0.41 kg/kgLNG • Power Deficit • Exergy Efficiency: 55.7%
NTNU
30.03.2012 T. Gundersen Slide no. 36
Offshore Process with Pressure Manipulations
• LIN: 1.25 kg/kgLNG • LCO2: 1.50 kg/kgLNG • Power Surplus • Exergy Efficiency: 84.1% • No Power Export: 76.3%
K-100
P-102NG-2
NG-1
NG-3
LIQ-EXP-102
NG-4
LNG
P-101
N2-2
N2-5N2-6
N2-3
EXP-101
N2-1
P-100
CO2-2
CO2-1
CO2-3
N2-4
CO2-4
HX-101 HX-102
N2-7
-180
-130
-80
-30
20
0 5 10 15 20 25 30Heat flow [MW]
Tem
pera
ture
[C]
Hot CC Cold CC
HX-101
HX-102
NTNU
30.03.2012 T. Gundersen Slide no. 37
Offshore Process in Balance with respect to Thermal and Mechanical Energy
• LIN: 1.0 kg/kgLNG • LCO2: 2.2 kg/kgLNG • Power Balance • Exergy Efficiency: 85.7%
-180
-130
-80
-30
20
0 5 10 15 20 25 30Heat flow [MW]
Tem
pera
ture
[C]
Hot CC Cold CC
HX-101
HX-102
NTNU
30.03.2012 T. Gundersen Slide no. 38
The Offshore Process in the LEC
K-100
P-102
V-101
NG-2
LIQ-EXP-101NG-1
NG-3 NG-4
LIQ-EXP-102
NG-5
NG-6
NG-PURGE
LNG
P-101
N2-2
N2-5
N2-10
N2-11
N2-6
N2-3
EXP-101
EXP-102
N2-1
P-100
CO2-2
CO2-1
N2-9K-101N2-8
CO2-3
N2-12
N2-4
N2-7
CO2-4
HX-101 HX-102
No flammable Refrigerants and no Gas Turbines !!
NTNU
30.03.2012 T. Gundersen Slide no. 39
Detailed Features of the Offshore Process
-200
-150
-100
-50
0
50
100
0 2 4 6 8Duty [MW]
Tem
pera
ture
[C]
Hot CCCold CC
Composite Curves - Offshore Process
Single Components (here CO2 and N2) exhibit Multi-component Behavior by Expansion and Compression
Aspelund A. and Gundersen T. ”A Liquefied Energy Chain for Transport and Utilization of Natural Gas for Power Production with CO2 Capture and Storage – Part 2, The Offshore and the Onshore Processes”, Journal of Applied Energy, vol. 86, pp. 793-804, 2009.
NTNU
30.03.2012 T. Gundersen Slide no. 40
Simulation-Optimization of the entire LEC
LIN LCO2 LCO2
LNGLNG
The field site
process
Storage
The market site
process
NG LNG LNG NG
P1 F1
LCO2CO2 P2
P3LINN2
N2
Powerprocess
with CO2 capture Water
Electricity
LNG
CO2
The simple chainThe complete chain
Storage
LNG
LCO2
LIN
LCO2F2
LIN
K-100
P-102
V-101
T1
LIQ-EXP-101NG-1
NG-4
LIQ-EXP-102
NG-5
NG-6
NG-PURGE
P3
P-101
N2-2
N2-10
N2-11
N2-6
N2-3
EXP-101
EXP-102
P2F2
P-100
CO2-2
F1
K-101
CO2-3
N2-12
T2
T4P6
CO2-4
HX-101 HX-102
P1
P5
P4
NG-2
T3
N2-1
CO2-1
LNG
N2-5
N2-8
NG-3
N2-4
N2-7
N2-9
NG-1HX-102
P3 P-101
NG-3
P-102
HX-101
N2-8N2-9
EXP-101
NG-4
NG-5
NG @ 25
V-101 CO2-4K-107
CO2-5CO2-6K-108
CO2-7
F4
CO2-8
CO2-11
CO2-9
CO2-13
CO2-Recycle
4 stage compressionK101-K104
N2-1
VF1
V-102
P2
N2-12
T5
P1
EXP-102
N2-14
T6
N2-16
F2
F32 stage compression
K105-K106
CO2-1
F1
CO2-0
N2-0
LCO2
LIN
LNG
CO2-12
CO2-10
N2-10
N2-13
T7N2-15
NG-2
N2-11
Offshore Onshore
NTNU
30.03.2012 T. Gundersen Slide no. 41
Optimization Variables Stream Type I Type II Name Unit Initial
value Lower bound
Upper bound
CO2-1 Global Pressure P1 kPa 600 550 1000
CO2-1 Global Flow rate F1 kg/h 80000 60000 150000
N2-1 Global Pressure P2 kPa 400 400 1000
N2-1 Global Flow rate F2 kg/h 65000 55000 65000
LNG Global Pressure P3 kPa 110 100 300
NG-2 Global Pressure P4 kPa 9000 8000 10000
NG-3 Local Temperature T1 °C -61 -70 -50
N2-4 Local Temperature T2 °C -40 -60 0
N2-5 Global Pressure P5 kPa 600 400 1000
N2-7 Local Temperature T3 °C -40 -60 20
N2-8 Gobal Pressure P6 kPa 2800 1500 3500
N2-9 Local Temperature T4 °C -40 -60 20
Field Site Process
(offshore)
Stream Type I Type II Name Unit Initial value
Lower bound
Upper bound
LCO2 Global Pressure P1 kPa 600 550 1000
CO2-0 Global Flow rate F1 kg/h 80000 60000 150000
LIN Global Pressure P2 kPa 400 400 1000
N2-0 Global Flow rate F2 kg/h 65000 55000 65000
LNG Global Pressure P3 kPa 110 100 300
CO2-12 Local Flow rate F3 kg/h 10500 9000 25000
CO2-6 Local Flow rate F4 kg/h 35000 30000 55000
N2-9 Local Temperature T7 °C -96 -115 -80
N2-11 Global Void fraction VF1 - 0.4 0.1 0.5
N2-13 Local Temperature T5 °C -101 -115 -80
N2-15 Local Temperature T6 °C -115 -132 -92
Market Site Process
(onshore)
NTNU
30.03.2012 T. Gundersen Slide no. 42
Progress of the Optimization
28
29
30
31
32
33
34
35
36
0 50 100 150 200 250 300 350 4000
1
Best known objective Current best Local search
Myklebust J., Aspelund A., Tomasgard, A., Nowak M. and Gundersen T., “An Optimization-Simulation Model of a Combined Liquefied Natural Gas and CO2 Value Chain”, INFORMS Annual Meeting, Seattle, November 2007.
NTNU
30.03.2012 T. Gundersen Slide no. 43
Supercritical Oxy-Combustion Pulverized Coal-based Power Plant
C. Fu and T. Gundersen, “Exergy Analysis of an Oxy-Combustion Process for Coal-fired Power Plants with CO2 Capture”, ECI, CO2 Summit: Technology and Opportunity, Vail, Colorado, USA, 6-10 June, 2010.
ASU
CPU
FGD
Power Cycle*
* Reference: DOE/NETL, Report NO.: 2007/1291
567 MW
NTNU
30.03.2012 T. Gundersen Slide no. 44
• Net power output: 567 MW
• Coal feed: 69 kg/s = 5 962 tons/day
• O2 feed: 161 kg/s (excess O2: 10%) = 13 910 tons/day
• Efficiency penalty related to CO2 capture: 10.3% points (ASU: 6.6% points)
• Power to produce O2 (95 mol%): 124 MW
Some key Production Figures
Air
Coal
Mill
HRSG
Steam Turbine
ElectricityGenerator
Condenser
Ash
ESP
Limestone Slurry
Gypsum
Fan Fan
Fan
CO2 For Storage
FGD CO2 Drier
CO2 Purification
TowerLP
Compressor
HP Compressor
Inerts
Air Separation
UnitCombustor
N2
O2
H2O
NTNU
30.03.2012 T. Gundersen Slide no. 45
Efficiency Penalties for CO2 Capture
Air
Coal
Mill
HRSG
Steam Turbine
ElectricityGenerator
Condenser
Ash
ESP
Limestone Slurry
Gypsum
Fan Fan
Fan
CO2 For Storage
FGD CO2 Drier
CO2 Purification
TowerLP
Compressor
HP Compressor
Inerts
Air Separation
UnitCombustor
N2
O2
H2O
ASU CPU
6,6
1,4
3,6
2,0
0
2
4
6
8
10
12
Base case Theoretical Case
Effic
ienc
y Pe
nalty
(%) CPU
ASU
Specs on Oxygen:
~ 95 mol%, 1.25 bar
3.7
Fu C. and Gundersen T., “Exergy Analysis of an Oxy-combustion Process for Coal-fired Power Plants with CO2 Capture”, submitted to Fuel, June 2011
NTNU
3/30/2012 T. Gundersen Slide no. 46
Our Research Motivation
Power Plant
Air Power
Coal 1393 MW (HHV)
560 MW
ASU Power Plant
CPU
Air O2
H2O
Exhaust
CO2
Coal 1879 MW (HHV)
Net Power
567 MW
69 MW
124 MW
without CCS560 40.2%
1393η = =
with CCS567 30.2%
1879η = =
total567 124 69 40.5%
1879η + +
= =
1ASU
1CPU
124 6.6% pts1879
69 3.7% pts1879
η
η
∆ = =
∆ = =
Improving the ASU by 20% gives 4.4% more Power !!
or 1.32% points
NTNU
30.03.2012 T. Gundersen Slide no. 47
Conventional ASU – here producing 95% O2
HP LP
Condenser
Reboiler
Air
A1-2
Impurities
A1-4
A1-5
A2-2 A2-3
A3-1 A3-2 A3-3
A5-1
A5-2
A7-1
A4-1A4-2
A4-3
A4-4
O2
N2 waste
Extracted N2
A0
A1-1A1-3
A2-1
A7-2
A7-3
PPU
MHE
MAC
Energy Consumption ♦ Actual: 0.193 kWh/kgO2 ♦ Ideal: 0.049 kWh/kgO2
Exergy Losses ♦ Air Compressor: 38% ♦ Distillation Cols.: 28%
Our Goal: ♦ Save 10-20%
Fu C. and Gundersen T., “Using Exergy Analysis to reduce Power Consumption in Air Separation Units for Oxy-combustion Processes, Energy, available on-line,
http://dx.doi.org/10.1016/j.energy.2012.01.065, February, 2012
NTNU
30.03.2012 T. Gundersen Slide no. 48
Compressor: 20.812.6
Coolers: 17.6
7.2
28.2
1.7
11.9
HP: 1.6
LP: 14.6
Condenser/reboiler: 6.3
Heat exchanger: 3.0Valves: 2.7
0
5
10
15
20
25
30
35
40
45
AU1 AU2 AU3 AU4 AU5 AU6
Exe
rgy
loss
es [%
]
38.4
AU1: The main air compressor
AU2: The pre-purification unit
AU3: The main heat exchanger
AU4:The air distillation system
AU5: The tail N2 turbine
AU6: The waste N2
Distribution of Exergy Losses
Largest Sources of Exergy Losses ♦ Distillation System (28.2%)
LP Column ♦ Main Air Compressor (38.4%)
Interstage Coolers Compression Process itself
NTNU
30.03.2012 T. Gundersen Slide no. 49
How to reduce Compressor Work?
Simplified Equation for Ideal Gas indicates: ♦ Increase Compressor Efficiency
Responsibility of the Manufacturers ♦ Reduce Inlet Temperature
Beyond CW requires Refrigeration, thus more Work ♦ Reduce Pressure Ratio
Limited by Condenser/Reboiler Match, but there are ways around it …. !!
♦ Reduce Mass Flowrate through the Compressor Do we really need to compress the Oxygen?
Our Inventions are based on the last two: ♦ Reducing Compressor Flowrate and Pressure Ratio
Fu C. and Gundersen T. “Power Reduction in Air Separation Units for Oxy-Combustion Processes based on Exergy Analysis”, in E.N. Pistikopoulos et al. (eds.), 21st European Symposium on Computer
Aided Process Engineering (ESCAPE 21), Elsevier B.V., vol. 29, Part B, pp. 1794-1798, June 2011.
NTNU
30.03.2012 T. Gundersen Slide no. 50
Specific Shaftwork for Separation: 0.178 kWh/kgO2
Recuperative Vapor Recompression Cycle
Fu C. and Gundersen T. “Innovative air separation processes for Oxy-Combustion plants”, 2nd International Oxy-fuel Combustion Conference, Yeppoon, Australia, September 2011.
NTNU
21
19
17
791113
15
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1x (N2)
y (N
2)
Feedline
Equilibriumline Operating
line
23
21
19
17
791113 15
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1x (N2)
y (N
2)
Feedline
Equilibriumline
Operatingline
30.03.2012 T. Gundersen Slide no. 51
Column Grand Composite Curve for Distributed Reboiling
McCabe-Thiele Diagram for Distributed Reboiling
NTNU
30.03.2012 T. Gundersen Slide no. 52
Vapor Recompression with Dual-Reboiler
Specific Shaftwork for Separation: 0.166 kWh/kgO2
Fu C. and Gundersen T., “Using PSE to develop Innovative Cryogenic Air Separation Processes”, accepted for the 11th Intl. Symp. on Process
Systems Engineering (PSE 2012), Singapore, 15-19 July, 2012
NTNU
30.03.2012 T. Gundersen Slide no. 53
Intermediate & Recuperative Vapor Compression Cycle
Specific Shaftwork for Separation: 0.159 kWh/kgO2
NTNU
30.03.2012 T. Gundersen Slide no. 54
Performance Comparison O2 purity,
% Specification Shaftwork
for Separation, kWh/kgO2 Power savings
Cycle 1 (reference) Conventional double column cycle
95.0 0.193 Ref. Case
Cycle 2 Vapor recompression cycle
95.4 0.178 -7.8 %
Cycle 3 Vapor recompression cycle with dual reboiler
95.5 0.166 -14.0 %
Cycle 4 Intermediate vapor recompression cycle
95.1 0.159 -17.6 %
OPEX is down; what about CAPEX ?? Fu C., Gundersen T. and Eimer D., “Air Separation”, GB Patent, Application number GB1112988.9, July 2011
NTNU
30.03.2012 T. Gundersen Slide no. 55
Is this the Optimum (Local or Global)?
NTNU
30.03.2012 T. Gundersen Slide no. 56
Summary of the Presentation Demonstrated the use of Thermodynamics in Design
♦ Pinch Analysis and Exergy Analysis ♦ McCabe-Thiele and Column Grand Composite Curve
Demonstrated Innovations ♦ The Liquefied Energy Chain (LEC) ♦ New Air Separation Cycles (ASUs)
Demonstrated Energy Efficiency ♦ LEC with 47.1% efficiency vs. 42.5% for Conventional ♦ New ASU cycles saving almost 20% on Energy
Applications relate to Carbon Capture & Storage ♦ Making environmentally friendly LNG even more friendly ♦ Elegant CCS solution for natural gas based Power Stations ♦ Making the Oxy-combustion route even more attractive
Hopefully demonstrated the Power of using PSE (Process Synthesis and Process Integration) in designing Energy and Production Systems