Graz
Introduction of closed cycle gas
turbines with their capability of retaining combustion generated CO2
can offer a valuable contribution to the
Over the last years the authors have presented a design solution
for this oxy-fuel CO2 retaining gas turbine system which can by
acceptance of international gas turbine industry be put into operation within a
few years. The authors believe, that this system is equal in thermodynamic
performance to any other proposal in the field of Carbon Capture and Storage
(CCS) and is superior in applying gas turbine experience and research
accumulated to our day.
History and Continuous
Development
The basic principle of the so-called Graz Cycle has been
developed by H. Jericha and presented at the CIMAC conference in
ASME Turbo Expo 2004,
At the ASME IGTI conference 2004 in
ASME Turbo Expo 2005,
Reno-Tahoe, USA [15]:
Due to this favorable economic data the Norwegian oil and
gas company Statoil ASA initiated a
cooperation in order to conduct a feasibility study together with a major gas
turbine manufacturer with the goal of a technical and economic evaluation. In [15] the basic thermodynamic assumptions for component
losses and efficiencies agreed with Statoil for a 400 MW Graz Cycle plant are
shown and the resulting power cycle for natural gas firing is presented. Its
net efficiency of 52.6 % is below the first simulations, but is still above
most alternative CO2 capture technologies.
ASME Turbo Expo 2006,
In order to avoid the difficulties of
condensation of water out of a mixture of steam and incondensable gases at very
low pressures, at the ASME 2006 [17] a modified
cycle configuration was presented with condensation in the range of 1 bar. It
allows a separate bottoming steam cycle with reasonably high pressures and
efficiencies, so that a high net cycle efficiency above 53 % can be
expected. A design concept for a Graz Cycle plant of 400 MW net output is
presented with two shafts. A fast running compression shaft is driven by the
compressor turbine HTTC, whereas the power shaft comprises the power turbine HPT
and the LPST.
ASME
In
2008 the Graz Cycle turbomachinery were changed to
higher pressure and temperatures. A new pre-compressor for the working fluid
allows to maintain the volume flow for the succeeding compressors, so that they
remain nearly identical. The new turbomachinery
result in a Graz Cycle power plant of 600 MW power output. Due to the higher
cycle parameters of 50 bar and 1500°C, a net cycle efficiency above 55 % can be
expected.
ASME Turbo Expo 2010,
In
2010 the Graz Cycle was adopted for the use of syngas from coal gasification.
Syngas containing carbon monoxide, carbon dioxide and hydrogen is fed to the
Graz Cycle combustor, the carbon dioxide separation takes place by
condensation. Heat of the gasification process is used in the Graz Cycle plant.
The oxy-fuel technology of the Graz Cycle is then compared with a
pre-combustion plant, where the carbon monoxide is converted to carbon dioxide
by shift reaction and separation of the carbon dioxide from the syngas is done
by chemical absorption. The comparison shows a higher efficiency for the Graz
Cycle plant.
ASME Turbo Expo 2011, Vancouver,
Canada [24]:
In
order to In order to facilitate construction of a demonstration plant the
performance of a near-term Graz Cycle process design based on modest cycle data
and available turbomachinery components using a simplified flow scheme is presented
at the 2011 ASME conference. Two near-term Graz Cycle plants are presented
based on basic and advanced operating conditions of the proposed commercially
available turbine. The predicted optimum net efficiency achieved is 23.2 %
(HHV).
A near-term zero-emission power plant can only be
commercially attractive if it will be deployed in a niche market. Therefore an
economic analysis commensurate with an early pre-FEED conceptual study is
carried out for the U.S. Gulf Coast where revenue from multiple product streams
that could include power, steam, CO2 and water, as well as argon and
(potentially) nitrogen from the ASU is provided. The economic analysis suggests
that a capital investment of $94 million can secure construction of a
13.2 MWe zero emission oxyfuel power plant and yield a 14.5% (unlevered) return on
capital invested.
ASME Turbo Expo 2016, Seoul, South Korea [25]:
In
this work presented at the ASME IGTI Conference 2016 the Graz Cycle is proposed
for this role. The Graz Cycle is now adapted for hydrogen combustion with pure
oxygen so that a working fluid of nearly pure steam is available. The changes
in the thermodynamic layout are presented and discussed. The results show that
the cycle is able to reach a net cycle efficiency based on LHV of 68.5 % if the
oxygen is supplied “freely” from hydrogen generation by electrolysis.
An
additional parameter study shows the potential of the cycle for further improvements.
The high efficiency of the Graz Cycle is also achieved by a close interaction
of the components which makes part load operation more difficult. So in the
second part of the paper strategies for part load operation are presented and
investigated. The thermodynamic analysis predicts part load down to 30 % of the
base load at remarkably high efficiencies.
Economic Analysis
In an economical analysis the Graz Cycle power plant is
compared with a reference plant. The assumptions for capital costs, fuel costs
and O&M costs as well as the economical parameters are listed in [17]. The resulting mitigation costs are in the range
of 20 – 30 $/ton CO2 avoided depending on the costs of the air separation
unit (ASU) and thus are below a threshold value of 30 $/ton CO2
(assumed for future CO2 emission trading). This makes the Graz Cycle
an economically interesting solution for future CO2 capture.
CO2 mitigation costs vs. capital costs
Basic cycle configuration [15]
Basically the Graz Cycle consists of a high temperature Brayton cycle (compressors C1 and C2, combustion
chamber and High Temperature Turbine HTT) and a low temperature Rankine cycle (Low Pressure Turbine LPT, condenser,
Heat Recovery Steam Generator HRSG and High Pressure Turbine HPT).
The fuel (natural gas) together with the nearly stoichiometric mass flow of
oxygen is fed to the combustion chamber, which is operated at a pressure of 40
bar. Steam as well as a CO2/ H2O mixture is supplied
to cool the burners and the liner.
A mixture of about 74 % steam, 25.3 % CO2, 0.5
% O2 and 0.2 % N2 (mass fractions) leaves the combustion
chamber at a mean temperature of 1400 C. The fluid is expanded to a
pressure of 1.05 bar and 579 C in the HTT. Cooling is performed with steam
coming from the HPT, increasing the steam content to 77 % at the HTT
exit. The hot exhaust gas is cooled in the following HRSG to vaporize and
superheat steam for the HPT. But after the HRSG only 45 % of the cycle mass
flow are further expanded in the LPT. The LPT exit and thus condenser pressure
is 0.041 bar for a cooling water temperature of 8°C.
Principle flow scheme of basic S-Graz Cycle power
plant
Gaseous and liquid phase are separated in the condenser.
From there on the gaseous mass flow, which contains the combustion CO2 and
half of the combustion water, is compressed to atmosphere with intercooling and
extraction of condensed water. CO2 is supplied for further use or
storage.
After segregating the remaining combustion H2O,
the water from the condenser is preheated, vaporized and superheated in the
HRSG. The steam is then delivered to the HPT at 180 bar and 549 C. After the
expansion it is used to cool the burners and the HTT stages.
The major part of the cycle medium, which is separated
after the HRSG, is compressed using an intercooled compressor and fed to the
combustion chamber with a maximum temperature of 600 C.
The cycle arrangement of the
Modified cycle configuration with working fluid
condensation at 1 bar [17]
Recent research shows that difficulties in condensation
arise in the formation of water films on the cooling tubes and in concentration
of CO2 forming a heat transfer hindering layer so that only a low
heat transfer coefficient in condensation will be achieved. This results in
excessively large condenser heat transfer surface and related high costs.
Therefore it was suggested to condense this mass flow at atmosphere, separate
the combustion CO2 and re-vaporize the water at a reduced pressure
level using the condensation heat. The pure steam is then fed to a Low Pressure
Steam Turbine LPST, where it can be expanded to a condenser pressure lower than
that for the working fluid mixture.
In the novel configuration the process is now split into
the high-temperature cycle and a separate low temperature condensation process
as shown in the following simplified scheme. The high temperature part consists
of HTT, HRSG, C1/C2 compressors and HPT. Condensation of the working fluid in
the 1 bar range is proposed in order to avoid the problems of a working fluid
condenser at vacuum conditions as described above. The heat content in the flow
segregated after the HRSG for condensation is still quite high so
re-evaporation and expansion in a bottoming cycle is mandatory.
Principle
flow scheme of modified
This bottoming cycle operates by pure steam with
extensively cleaned feed water and thus allows together with the very low
cooling water temperatures of northern
For proper re-evaporation two sections of working fluid
condensations are provided, each following a compressor stage with reasonable
increase of flow pressure resulting in a higher partial condensation pressure
of the water content. At the first pressure level of 1.27 bar about 63 % of the
water content can be segregated, so that the power demand of the second
compression stage is considerably reduced. It compresses up to 1.95 bar, which
allows the segregation of further 25 % of the contained water. Further cooling
of the working fluid, also for water preheating, leads to the separation of
additional 11 %, so that the water content of the CO2 stream
supplied at 1.9 bar for further compression is below 1 %. After segregation of
the water stemming from the combustion process, the water flow is degassed in
the deaerator with steam extracted after the HPT and
fed to the HRSG for vaporization and superheating.
This two-step pre-compressed condensation counteracts the
effect of sinking H2O partial pressure due to condensed water
extraction from working fluid and thus allows a reasonably high constant
re-evaporation pressure of 0.75 bar for the bottoming steam cycle.
The Graz Cycle for Hydrogen-Oxygen Combustion [28]
A modern energy system based on renewable energy like wind and solar power inevitably
needs a storage system to provide energy on demand. Hydrogen is a promising candidate
for this task. For the re-conversion of the valuable fuel hydrogen to electricity the Graz Cycle is a promising candidate due to its high efficiency. It is now adapted for hydrogen combustion with pure oxygen
so that a working fluid of nearly pure steam is available. The results show that the cycle is able to reach a
net cycle efficiency based on LHV of 68.43% if the oxygen is supplied “freely” from hydrogen generation by electrolysis.
For this process strategies for part load operation are also investigated. The thermodynamic analysis predicts part load down to 30% of the base load at remarkably high efficiencies.
TTM
publications on the Graz Cycle
[2] Jericha, H., Fesharaki, M., 1995, "The Graz
Cycle 1500 C Max Temperature-CO2 Capture with CH4-O2 Firing", ASME
paper 95-CTP-79, ASME Cogen-Turbo Power Conference,
[3] Lukasser, A.,
1997, "Graz Cycle, eine Innovation zur CO2 Rückhaltung", Master thesis, Graz University of Technology.
[4] Tabesh, H.,
1997, "CH4-Graz-Cycle: Optimierung und Auslegung der Wärmetauscher",
Master thesis, Graz University of Technology.
[5] Jericha, H.,
Fesharaki, M., Lukasser,
A., Tabesh, H., 1998, "Graz Cycle – eine Innovation zur
CO2-Minderung", BWK Bd. 50 (1998), Nr. 10, Seiten 30-34.
[6] Jericha, H., Lukasser, A., Gatterbauer, W., 2000, "Der Graz Cycle für Industriekraftwerke
gefeuert mit Brenngasen aus Kohle- und Schwerölvergasung", VDI Berichte 1566, VDI Conference Essen,
Germany.
[7] Jericha, H., Göttlich, E., 2002, "Conceptual
Design for an Industrial Prototype Graz Cycle Power Plant", ASME Paper
2002-GT-30118, ASME Turbo Expo 2002,
[8] Jericha, H., Göttlich, E.,
Sanz, W., Heitmeir, F., 2003, "Design Optimisation of the Graz Cycle Prototype Plant",
ASME Paper 2003-GT-38120, ASME Turbo Expo 2003,
[9] Heitmeir, F., Sanz, W., Göttlich, E., Jericha H., 2003, "The Graz
Cycle – A Zero Emission Power Plant of Highest Efficiency", XXXV Kraftwerkstechnisches Kolloquium,
[10] Jericha, H., Sanz, W., Pieringer, P., Göttlich E., Erroi, P., 2004, "Konstruktion der ersten Stufe der HTT-Gasturbine
für den Graz Cycle Prototyp“ (in
German), VDI Conference Leverkusen, Germany.
[11] Sanz., W., Jericha, H., Moser, M., Heitmeir,
F., 2004, "Thermodynamic
and Economic Investigation of an Improved Graz Cycle Power Plant for CO2
Capture", ASME Paper GT2004-53722, ASME Turbo Expo 2004, Vienna,
Austria. (Conference
presentation)
[12] Moser, M., 2004, "Thermodynamische und wirtschaftliche
Optimierung des Graz Cycle", (in German), Master thesis,
Graz University of Technology. (nominated for best
TU-Graz Master thesis award
of 2004)
[13] Luckel, F.,
2004, "Weiterentwicklung des Graz Cycle und der Vergleich mit anderen
CO2-Rückhaltekonzepten", (in German), Master thesis,
Graz University of Technology.
[14] Erroi, P., 2004, "Strömungssimulation der ersten Stufe der
Hochtemperaturturbine des Graz-Cycles", (in
German), Master thesis, Graz University of
Technology. (nominated for best
TU-Graz Master thesis award of 2004)
[15] Sanz, W., Jericha, H., Luckel, F., Göttlich,
E., Heitmeir, F., 2005, "A Further
Step Towards a Graz Cycle Power Plant for CO2 Capture", ASME Paper
GT2005-68456, ASME Turbo Expo 2005, Reno-Tahoe, Nevada, USA. (Conference
presentation)
[16] Heitmeir, F., Jericha, H., 2005, "Turbomachinery design for the Graz cycle: an optimized
power plant concept for CO2 retention", Proceedings of the
Institution of Mechanical Engineers Part A: Journal of Power and Energy, Volume
219, Number 2, pp. 147-158(12). (DOI)
[17] Jericha, H., Sanz, W., Göttlich, E., 2006, "Design
Concept for Large Output Graz Cycle Gas Turbines", ASME Paper
GT2006-90032, ASME Turbo Expo 2006,
[18] Jericha,
H., Sanz, W., Göttlich E., 2006, "Gasturbine mit
CO2-Rückhaltung – 490 MW (Oxyfuel-System Graz Cycle)“ (in German),
VDI Conference Leverkusen, Germany (Conference
presentation)
[19] Jericha,
H., Sanz, W., Göttlich E., 2007, "Gas
Turbine with CO2 Retention – 400 MW Oxyfuel-System
Graz Cycle“, Paper No. 168, CIMAC Conference 2007, Vienna, Austria (Conference
presentation)
[20] Sanz,
W., Jericha, H., Bauer, B., Göttlich E., 2007, "Qualitative
and Quantitative Comparison of Two Promising Oxy-Fuel Power Cycles for CO2
Capture“, ASME Paper GT2007-27375, ASME Turbo Expo 2007, Montreal, Canada (Conference
presentation). Also published in: Journal of Engineering for Gas Turbines
and Power, Volume 130, Issue 3, May 2008. (DOI)
[21] Jericha,
H., Sanz, W., Göttlich E., Neumayer, F., 2008, "Design Details of a 600 MW Graz Cycle
Thermal Power Plant for CO2 Capture“, ASME Paper GT2008-50515, ASME Turbo Expo 2008,
Berlin, Germany (Conference
presentation)
[22] Jericha, H., Sanz, W., Göttlich
E., Neumayer, F., 2008, "Mit Überschallstufen und
ICS-Dampfkühlung zur 600 MW Oxyfuel-Graz-Cycle-Einheit“ (in German), VDI Conference Leverkusen, Germany (Conference presentation)
[23] Sanz,
W., Mayr M., Jericha, H., 2010, "Thermodynamic and Economic
Evaluation of an IGCC Plant Based on the Graz Cycle for CO2 Capture“, ASME Paper GT2010-22189, ASME Turbo Expo 2010,
Glasgow, UK (Conference
presentation)
[24] Jericha,
H., Hacker, V., Sanz, W., Zotter, G., 2010, "Thermal Steam
Power Plant fired by Hydrogen and Oxygen in stoichiometric Ratio, using Fuel
Cells and Gas Turbine Cycle Components", ASME Paper GT2010-22282, ASME
Turbo Expo 2010, Glasgow, UK
[25] Sanz,
W., Hustad, C.-W., Jericha, H., 2011,
"First
Generation Graz Cycle Plant for Near-Term Deployment“, ASME Paper GT2011-45135, ASME Turbo Expo 2011,
[26] Platzer,
M.F., Sanz, W., Jericha, H., 2014,
"Renewable
Power via Energy Ship and Graz Cycle“, 15th International Symposium on
Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC-15, Honolulu,
HI, USA (Conference
presentation)
[27]
Sanz,
W., Braun, M., Jericha, H., Platzer, M.F., 2016, "Adapting
the Zero-Emission Graz Cycle for Hydrogen Combustion and Investigation of its
Part Load Behaviour“, ASME Paper GT2016-57988,
ASME Turbo Expo 2016, Seoul, South Korea (Conference
presentation)
[28] Sanz, W., Braun, M., Jericha, H., Platzer,
M.F., 2018, "Adapting
the Zero-Emission Graz Cycle for Hydrogen Combustion and Investigation of its
Part Load Behaviour“, International
Journal of Hydrogen Energy 43 (2018), 5737-5746 (DOI)
[29] Wimmer, K., Sanz, W., 2020, "Optimization
and comparison of the two promising oxy-combustion cycles NET Power cycle and
Graz Cycle “,
International Journal of Greenhouse Gas Control 99 (2020), 103055 (DOI)
[30] Mitterrutzner, B., Sanz, W., Nord, L.O., 2022,
"A
part-load analysis and control strategies for the Graz Cycle “, International Journal
of Greenhouse Gas Control 113 (2022), 103521 (DOI)
[31] Gutierrez,
F.A., Garcia-Cuevas, L.M., Sanz, W., 2022, "Comparison
of cryogenic and membrane oxygen production implemented in the Graz cycle“,
Energy Conversion and Management 271 (2022), 116325 (DOI)
[32] Mitterrutzner,
B., Nord, L.O., Motamed, M.A., Sanz, W., 2024, “Dynamic modelling and
simulation of the Graz Cycle for a renewable energy system”, Applied Thermal
Engineering 242 (2024) 122400 (DOI)
Some
of the first third-party publications citing the Graz
The list below is "old" and by no far an exhaustive list of
publications mentioning the
-
Mori,
H., Sugishita, H., Uematsu,
K., 1998, "A Study
of 50MW Hydrogen Combustion Turbines", XII World Hydrogen Energy
Conference. (HTML)
-
Bolland, B., Kvamsdal, H.M., Boden, J.C., 2001, "A Thermodynamic Comparison of the Oxy-Fule Power Cycles, Water-cycle, Graz-Cycle and Matiant-Cycle", International Conference on Power
Generation and Sustainable Development,
-
Celano A., 2002, "Comparison of near Zero CO2 Emission
Power Plants on CO2/H2O Mixture", Doctoral Thesis,
-
Kail, C.,
Haberberger, G., 2002,
"Kohlendioxid-Rückhaltung und Wirkungsgraderhöhung durch interne
Zusatzfeuerung bei Dampfkraftwerken", (in German), VDI Berichte 1714. (PDF)
-
Miller,
A., Lewandowski, J., Badyda, K., Kiryk,
S., Milewski, J.,
-
Mathieu,
P., 2003, "Zero
Emission Technologies: An Option for Climate Change Mitigation", Third
Nordic Minisymposium on Carbon Dioxide Capture and
Storage,
-
Gupta,
M., Coyle,
-
Ito, S., Saeki, H., Inomata, A., Ootomo, F.,
Yamashita, K., Fukuyama, Y., Koda, E., Takehashi, T., Sato, M., Koyama, M., Ninomiya,
T., 2005, "Conceptual Design and Cooling Blade
Development of 1700°C Class High-Temperature Gas Turbine", Journal of
Engineering for Gas Turbines and Power, Volume 127, Issue 2, pp. 358-368. (DOI)
-
Anheden, M., Yan, J., De Smedt, G., 2005, "Denitrogenation
(or Oxyfuel Concepts)", Oil & Gas Science
and Technology – Rev. IFP, Vol. 60 (2005), No. 3, pp. 485-495. (PDF)
-
Gou, C., Cai, R., Hong, H., 2006, "An Advanced Oxy-Fuel Power Cycle with High
Efficiency", Proceedings of the Institution of Mechanical Engineers Part
A: Journal of Power and Energy, Volume 220, Number 4, pp. 315-325(11). (DOI)
-
ENCAP, 2006,
“Second Newsletter of ENCAP Project” (PDF)
-
Franco,
F., Mina, T., Woolatt, G., Rost, M., Bolland, O., 2006, “Characteristics of
Cycle Components for CO2 Capture”, Proceedings of 8th International Conference
on Greenhouse Gas Control Technologies, Trondheim, Norway. (PDF)
- Kvamsdal, H.M., Bolland, O., Maurstad, O., Jordal, K., 2006, "A Qualitative Comparison of Gas Turbine Cycles with CO2 Capture", Proceedings of 8th International Conference on Greenhouse Gas Control Technologies, Trondheim, Norway (PDF)
-
Zhang,
N., Lior, N., 2008, "Comparative Study of Two Low CO2 Emission
Power Generation System Options With Natural Gas
Reforming", Journal of Engineering for Gas Turbines and Power, Volume 130,
Issue 5, September 2008. (DOI)
-
Zero
Emissions Platform, 2011, “The Costs of CO2 Capture – Post-demonstration
CCS in EU”, Report by the European Technology Platform for Zero Emission Fossil
Fuel Power Plants (PDF)
-
Mancuso,
L., Ferrari, N., Chiesa, P., Martelli, E., Romano, M., 2015, “Oxy-combustion
turbine power plants”, IEAGHG report, 5. (PDF)
-
Ghoniem, A. F., 2021, “Energy Conversion Engineering: Towards Low
CO2 Power and Fuels”, Cambridge: Cambridge University Press (DOI)
This web page is maintained by Wolfgang Sanz,
Institute for Thermal
Turbomachinery and Machine Dynamics (TTM), Graz University of Technology.
Contact: wolfgang.sanz@TUGraz.at
Last updated: March 15, 2024