Piloting of Siemens PostCap™
Technology, 9,000 hours of Operational
Experience including Mongstad
Technology Qualification Program
Michael Horn, Albert Reichl,
Torsten Schliepdiek, Henning
Schramm
Siemens AG
Germany
1/19
Table of Contents
1
Executive summary ............................................................................................................ 3
2
Introduction ........................................................................................................................ 3
2.1
Next step in CCS deployment: Scale up to full scale.................................................. 3
2.2
Requirement for technical qualification and verification ............................................ 3
3
The Siemens PostCap™ technology .................................................................................. 4
4
PostCapTM pilot plant location and set-up .......................................................................... 5
5
4.1
Pilot plant design ......................................................................................................... 6
4.2
Operational conditions of the pilot plant ..................................................................... 8
Pilot plant operation.......................................................................................................... 10
5.1
Test program ............................................................................................................. 10
5.2
Results ....................................................................................................................... 11
5.2.1
Functional performance ..................................................................................... 11
5.2.2
Operability ......................................................................................................... 13
5.2.3
Process model validation ................................................................................... 13
5.2.4
Material tests ...................................................................................................... 14
5.2.5
Emission measurements & liquid analysis ........................................................ 14
5.2.6
Verification of reclaiming technology ............................................................... 15
5.3
Summary ................................................................................................................... 16
5.3.1
Pilot plant operation with coal and gas fired flue gas ........................................ 16
5.3.2
Technology Qualification Program (TQP) for CCM project (gas fired) ........... 16
6
Scalability and constructability ........................................................................................ 17
7
References ........................................................................................................................ 17
8
Acknowledgements .......................................................................................................... 18
Permission for use .................................................................................................................... 19
Disclaimer ................................................................................................................................ 19
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1 Executive summary
The paper summarizes the more than 9,000 hours of operational experiences at the PostCap™
carbon capture pilot plant at E.ON’s Staudinger power plant near Hanau/Germany. The pilot
plant started operation in 2009. During the first three years of operation the process was
tested and its technical features were proven and further optimized, e.g. with respect to
operability and energy demand, by using a slip stream from the flue gas of a coal fired power
plant. In 2012 a gas burner was installed as an alternative source for CO2, and the pilot plant
was operated for approx. 3.500 h on a flue gas composition equal to a gas turbine power
plant. In this period of time a Technology Qualification Program (TQP) for the Carbon
Capture Mongstad project in Norway was completed together with Statoil/Gassnova to prove
the maturity for a full scale implementation. Key criteria for the TQP were the validation of
the process model, verification of specific thermal optimization concepts and supporting
technologies, reclaiming technology, materials performance and the effectiveness of the
demisting technology.
With the help of the results from the pilot plant operation a scale-up of the technology into a
full scale application is possible. Front End Engineering Design (FEED) and concept studies
were already executed for several projects.
2 Introduction
2.1 Next step in CCS deployment: Scale up to full scale
While fossil power is still one of the main sources for electrical energy generation for the
coming decades, one of the biggest challenges to the fossil energy industry in the 21st century
is the development of economically feasible carbon capture technologies to mitigate climate
change and also co-generate CO2 for usage e.g. in enhanced oil recovery (EOR).
Several technologies for CO2 reduction have been developed – pre-combustion, oxyfuel and
post combustion. The latter usually employs a chemical absorption – desorption process, but
with different solvents. Siemens has chosen amino acid salt as solvent for the development of
a post combustion capture process (details see chapter 3). Regardless of the specific
technology, transfer to full scale is challenging, since the dimensions are huge. A step in
between (demonstration plant) would be feasible, but these projects are also capital intensive.
Thus transfer from pilot to full scale is one alternative, meaning that pilot experiments have
to be thoroughly executed, monitored and evaluated [1] [2] [3].
2.2 Requirement for technical qualification and verification
To gain security for the scale up of the carbon capture technology to full scale and resulting
operational requirements it is necessary to validate the technology in pilot scale projects in an
industrial environment.
Laboratory experiments have to be performed beforehand and also as parallel supporting
activities but they are limited in their significance, mainly with regards to size and synthetic
conditions.
The resulting focus during pilot plant operation can be summarized as follows:
-
Prove of concept: the selected process of carbon capture is validated with authentic
industrial flue gas in a stable operation mode
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-
Prove of performance: the performance of the carbon capture process is measured
(e.g. capture rate, long-term solvent stability and degradation, heat rate, power
consumption, emissions)
-
Prove of operability (e.g. plugging, foaming)
-
Prove of construction material concept
-
Optimization of function and design of mechanical equipment
-
Validation of simulation models to ensure reliable process design results for upscaling
-
Validation of control concept
3 The Siemens PostCap™ technology
Siemens has developed a post combustion carbon capture process, the Siemens PostCap™
process based on an amino acid salt (AAS) solvent (aqueous solution). The process is capable
of separating at least 90% of the CO2 contained in the flue gas from coal, oil or gas fired
power plants as well as from industrial sources. Figure 1 shows the PostCapTM process
configuration in general.
Decarbonized
flue gas
Solvent reclaiming
CO2 compression
CO2 absorption
CO2 desorption
Flue gas inlet
Figure 1: Siemens PostCapTM process configuration
The raw flue gas is cooled in a flue gas cooler and then conveyed by a blower through the
absorber. The gas leaves the top of the absorber as decarbonized flue gas. The solvent meets
the flue gas in the countercurrent absorber, where CO2 is selectively absorbed by a chemical
reaction. The “rich” solvent (loaded with CO2) is pumped from the absorber bottom and
heated up in a “rich/lean solvent heat exchanger”, before it enters the top of the desorber
column. At the desorber bottom, the chemical bonding of CO2 is reversed at a higher
temperature (which is provided by steam in a reboiler). Thus a mixture of CO2 and water is
stripped out. The water is condensed at the desorber top condensor, whereas the remaining
CO2 is compressed (and if applicable purified) for transport, such as by pipeline, and further
use. The “lean” solvent (which has been relieved of most of its CO2) is pumped from the
desorber bottom, cooled in two steps (“rich/lean solvent heat exchanger” and “lean solvent
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cooler”) and then fed to the absorber top. A small slipstream of cold solvent is taken
downstream of the lean solvent cooler for reclaiming. The purified solvent is fed back
upstream of the lean solvent cooler.
The particular advantages of using an Amino Acid Salt as solvent are:
 Application of an environmentally friendly, biodegradable, non-toxic solvent
 Minimal solvent emissions due to a very low vapor pressure
 Good solvent stability against various degradation mechanisms, particularly against
oxidation and - as a result - low solvent refill need
 Ease of handling by power station operators and personnel (inflammable, nonexplosive, no inhalation risk).
During process operation amino acid salt solvents (as well as amines) form degradation
products by thermal stress or reactions with SOx, NOx and oxygen contained in the flue gas.
To offset this degradation, the Siemens PostCapTM process applies a proprietary two-step
reclaiming process to minimize solvent losses, hence operation costs. SOx contaminated
solvent is fully recovered, the blocking of the solvent is fully reversed, and a sellable sulfur
product is generated. In principle any SOx content in the flue gas is feasible for PostCapTM,
however in practice a reasonable level has to be determined based on economic
considerations (cost of conventional flue gas desulphurization vs. cost of reclaiming).
Furthermore a highly selective separation of the amino acid salt solvent from other byproducts is applied in the second reclaiming step and thus a high recyclability assured. Each
step of the reclaimer can be operated independently (either continuously or batch-wise),
which allows tailor-made solutions for client’s needs.
4 PostCapTM pilot plant location and set-up
During the process development for PostCap™, Siemens got the opportunity to build a pilot
plant with a CO2 capacity of up to 40 kg/h at E.ON’s coal fired power plant Staudinger near
Frankfurt/Main in Germany. The location close to the Siemens R&D and chemical
engineering group in Frankfurt Industrial Park Hoechst is of great advantage because a
transfer of people and material between both sites is possible on short notice, and the
knowledge and experience of the Siemens PostCap™ and chemical process experts can be
used to a maximum extent. Also the laboratory scale carbon capture plant and the reclaimer
designed for the Pilot Plant operation are located at the Siemens premises in Frankfurt.
Figure 2: Location of the pilot plant at E.ON’s Staudinger Power Plant (red marker)
and Siemens laboratory in Frankfurt/Hoechst (blue marker) (Source: OpenStreetMap)
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4.1 Pilot plant design
The predominant target for the design of a pilot plant is to choose the dimensions in a way
that the achieved results are reproducible and can be used to set up and verify a process
calculation model. On the other hand, the pilot plant should not be too large in order to save
cost and construction time. Examples for the main equipment are given below. A simplified
process flow diagram (PFD) is shown in Figure 3. The pilot plant features more than 150
measuring points for monitoring, control and optimization. Furthermore, gas samples (both
online and isokinetic) and liquid samples can be drawn from several locations.
Since compression is a well-known technology, it does not have to be studied, thus the CO2
from downstream the desorber condenser is fed back to the power plant.
Condensate
Separator
Decarbonized
Flue Gas
CO2
Gas
Lean Solvent Cooler
Solvent for
Reclaimer
treatment
Desorber
Absorber
Desorber
Top
Condenser
Fresh Solvent
Rich/Lean Solvent
Heat Exchanger
Flue Gas
FG
cooler
Make-Up Water
Flue Gas Blower
Gas Return to
Power Plant
FG Cooler
Water Cycle
Solvent
Buffer
Tank
LSF Compressor
Flash Vessel
Rich Solvent Pump
Reboiler
Steam
Condensate
Lean Solvent Pump
Cooling Water
Cooling Water
Return to
Power Plant
Figure 3: Simplified process flow diagram (PFD) for the pilot plant configuration
Another design target was the operation of the pilot plant by remote control, which is possible
from the computers of the process experts via Internet, e.g. from their offices in Frankfurt.
Flue gas cooler
The flue gas cooler is designed to cool the flue gas from approx. 100 °C to approx. 40 °C. In
addition the flue gas cooler washes out some particulate matter and other contaminants in the
flue gas, and it can also be operated with potassium hydroxide in order to reduce SOx. At the
pilot plant the cooler is integrated in the lower part of the absorber column. The cooling
section has a height of 2.6 m and is equipped with a structured packing.
Absorber column design
To reflect the above mentioned targets of pilot plant operation the main design parameters of
the absorber are the diameter and the height. The diameter has to be chosen to achieve
reliable results for up-scaling. Under this aspect wall effects have to be considered, however
they will be of less influence in full scale. In addition literature [4] considers a scale-up factor
in the range of 1,000 to 50,000 as feasible for absorbers. As shown in table 1 the chosen
diameter of 200 mm is in a conservative range of the tolerable scale-up factors. To investigate
the flow and reaction behavior the height of the structured packing beds has to be set similar
to a full scale application. Thus the full height of 25 m was chosen for the sum of the beds of
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the structured packing. Injection points for lean solvent were placed at different heights of
the absorber, so that the impact of packing heights could be investigated.
Flue gas
Absorber
Laboratory
scale
Pilot-scale
Staudinger
Full-scale (gas
fired)
Nm³/h
3
230
2.3 Mio.
kg/h
4
300
3 Mio.
50 mm
DN 200
2 x > 15 m
Structured
(gauze)
Structured
(metal
sheet)
Structured (metal
sheet)
0.01
0.4
4 000
-
16 x
5 625 x pilot scale
Staudinger (for
one absorber)
Diameter
Packing type
Solvent
holdup
Scale-up
factor
m³
Cross-section
area absorber
lab scale
Table 1: Scale-up factors from Siemens laboratory plant to Staudinger pilot plant and
to a possible full scale application
In amine-based Post Carbon Capture processes there is normally an additional washing step
installed on top of the absorber column to clean the emitted flue gas from solvent vapor and
by-products. This step was not considered necessary for the AAS solution used by Siemens
based on the fact that salts have very low vapor pressure. For possible droplet emissions a
demister was implemented and successfully verified during the pilot plant operation.
Desorber column design
The selection criteria for the dimensional requirements of the desorber were similar as for the
absorber. The desorber diameter was chosen with 200 mm at the bottom part and 150 mm at
the main section and the top part. The chosen height of the structured packing beds is 15 m
which is assumed to be conservative. This packing height would in a first approach be
transferred to full-scale plants, but could be further optimized. In addition the pilot plant
desorber was designed for pressurized operation up to 3 bar(a) to increase the flexibility in
operation.
Layout
The pilot plant equipment is arranged on two floors installed in a steel structure based
container building with cladding (see Figure 4).
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Figure 4: Equipment arrangement on two levels and outside view of the PostCap™ pilot plant
Reclaimer
The reclaimer was constructed and commissioned for semi-continuous operation in the
Siemens laboratory in Frankfurt/Main for solvent loaded with by-products, which was taken
batch-wise from the pilot plant and re-fed into the pilot plant after treatment (see Figure 5). A
detailed description of the reclaiming process and steps was published in 2014 [5]
Figure 5: Reclaimer view in the laboratory in Frankfurt/Main.
4.2 Operational conditions of the pilot plant
The original design of the pilot plant was based on a slip stream from the flue gas of the
Staudinger coal fired power plant. The pilot plant was operated on this basis until summer
2010. During this period of time flue gas compositions in a range as shown in Table 2
occurred.
Composition
vol %
CO2
N2
O2
Ar
H2O
11.6-14.3
Not measured
4.9-6.7
Not measured
Not measured
3
mg/Nm
(dry)
at
6%
O
by-products
2 concentration
120-200
NOx
0.5 – 1,5 %
NO2/NOx
20-60
SOx
Table 2: Composition of flue gas at pilot plant inlet (coal fired operation)
In 2012 the Staudinger CCS Pilot Plant was nominated as Verification Plant (VP) for the
PostCap™ process within the Carbon Capture Mongstad (CCM) project of Statoil and
Gassnova. The goal of this project was the CO2 capture from a gas fired combined heat and
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power plant (CHP). For simulation of the CHP flue gas a gas burner was installed as a new
flue gas source (see Figures 6 and 7)
Figure 6: Gas burner (in container) for simulation of gas fired power plant flue gas conditions.
Stack close to
desulfurisation
system of
power plant
Flue gas to
stack
Emission source 2
pilot plant
Flue gas back to
power plant
CO2-product
Power Plant
Treated flue
gas
Flue gas feed from
power plant
Rich solvent
Flue gas
Flue gas
blower
Flue gas
Flue gas
cooler
Flue gas
Desorption
Absorption
(incl. condensation)
Lean solvent
Flue gas feed from
gas burner
New
gas burner
Flue gas to
stack
New natural gas
feed to
gas burner
new
existing
Existing natural
gas pipeline
Figure 7: Adaption of pilot plant to gas fired application.
During the gas fired application the flue gas was specified as shown in Table 3.
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Stack close to
gas burner
Emission source 1
pilot plant
Table 3: Composition of flue gas at carbon capture plant inlet (gas fired operation,
reference case taken from CCM project, simulated by gas burner operation in
verification plant)
5 Pilot plant operation
5.1 Test program
After two months of commissioning the Siemens PostCap™ pilot plant was taken into
operation in October 2009. A very short duration of installation and commissioning was
achieved by successfully using fast track engineering. As described in the following, pilot
plant operation involved several test and reconstruction phases.
Most important parameter variations comprised:
• Lean solvent inlet temperature to absorber
• Solvent pump-around
• Flue gas inlet
• Heat duty
• Amino acid salt concentration in solvent (aqueous solution)
October 2009 – July 2010
The pilot plant was adjusted and optimized to operate at the given environmental conditions
and with the defined interfaces to the power plant. Process parameter variations were
executed and respective operational data was obtained to validate the process model. Solvent
stability evaluation including SOx long-term experiments was executed as well as tests on
construction materials. Results of this first operational period were also shown in [6] and [7].
The first pilot plant operation phase was followed by a reconstruction period in July 2010.
The lean solvent flash equipment and some features for pressurized desorber mode were
installed, before the pilot plant was taken into operation again.
August 2010 – December 2010
After the pilot plant upgrade, experiments focused on pilot plant operation including the lean
solvent flash approach and other advanced process features. The target of the operation was
to confirm the expected reduction of energy demand due to the lean solvent flash and to revalidate the process model in accordance. The solvent stability evaluation and construction
material tests were extended.
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January 2011 – September 2011
Within the first three quarters of 2011, activities focused on the reclaimer development. In
order to ensure realistic boundary conditions, reclaimer tests had to be carried out with used
solvent. Therefore, the Staudinger pilot plant was operated under standard conditions in order
to produce several batches of used solvent. The solvent was then transported to
Frankfurt/Hoechst and treated within the pilot reclaimer in order to verify the solvent
regeneration process.
October 2011 – March 2012
During the first years of PostCap™ process development, laboratory and pilot plant
experiments had been carried out with an amino acid salt solution which is referred to as
“solvent type I”. In order to enlarge delivery options, the qualification of an alternative
solvent which is based on the same amino acid salt, but supplied by a different manufacturer
was carried out. “Solvent type II” qualification was successfully finalized by means of
experiments in the Staudinger pilot plant.
April 2012 – September 2012
From April to September 2012 the Staudinger pilot plant was reconstructed in order to
demonstrate PostCap™ process applicability to flue gases emitted from gas-fired power
plants by use of a gas burner.
October 2012 – November 2012
Restart of Carbon Capture plant after adjustment to gas burner operation. Start of the
technical qualification program (TQP) as agreed with Statoil/Gassnova. The first phase of the
heat and mass balance verification was conducted. Several measurement campaigns took
place where solvent and emissions behavior was analyzed.
December 2012 – March 2013
During that period of time the second phase of the heat and mass balance evaluation took
place. The configuration and function of the absorber and desorber demisters were tested and
validated. Further measurement campaigns were conducted. In parallel the operation and
verification of the reclaimer was executed. In March 2013 the 3,000 h test phase of the CCM
TQP was concluded successfully.
August 2013 – September 2013
An additional measuring campaign with the gas burner as flue gas source was conducted to
get a broader data base with regards to emissions and to evaluate the influence of Fe-Ions on
solvent degradation, especially on the creation of ammonia (NH3). Further detailed
investigations on the topic took place in the laboratory plant in Frankfurt Hoechst from April
to August 2014.
5.2 Results
5.2.1
Functional performance
The Capture Rate of 90% within the defined ranges was maintained at a constant steam input.
The overall and component mass balances could be closed for the whole operation period. No
shut downs related to solvent or process specific issues (e.g. plugging, precipitation)
occurred. Occasional unplanned shut downs were caused e.g. by external reasons such as
missing power, cooling water supply or flue gas from the coal fired boiler as well as
problems with the gas burner package unit used to synthesize flue gas.
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During the gas burner operation the “in-spec” availability was monitored as part of the
technical qualification program (TQP). An overall result of > 93 % was achieved (Figure 8).
The process parameters - like flue gas amount and composition (including SOx and NOx byproducts), capture rate, steam input, solvent pump-around, temperature and pressure at
desorber - were kept within the comparably narrow pre-agreed ranges.
32
40
96
36
60
33
24
30
88
26
52
23
16
20
80
16
44
13
08
10
2
67
33
6
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
In-Spec Availability %
% Total "in Spec" VP Availability relative to operating hours with flue gas
Calendar Hours
Figure 8: “In-spec” availability of the pilot plant with gas burner during TQP
The lean solvent flash (LSF) gas compression approach was successfully validated. Based on
process information derived from recorded data a conclusion about the use of LSF approach
can be drawn. By applying the LSF approach the thermal energy demand in the pilot plant
can be reduced by more than 40 % related to steam input, thus a level of < 2.7 GJ/t of
captured CO2 could be achieved under the conditions given at the pilot plant. This value was
confirmed in several testing phases and different set ups also with both flue gas types.
The quality of the CO2 product was specified for the gas based flue gas operation related to
possible storage requirements. Excluding a very short period with LSF compressor air
leakages, the O2 concentration in the CO2 product was considerably lower than the
requirement specification. Hence it was possible to conclude that the originally planned deoxygenation unit is not required in the full-scale plant. It has to be stated that the reason for
the LSF compressor leakage could not occur in a full scale plant based on constructional and
control differences between pilot scale and full scale equipment. Project specific discussions
of the N2 limit showed that values of < 0.2 mole % are expected for full scale projects, see
Table 4 as an example. In analogy to O2, the measured values were considerably lower.
Sulphur components were below detection limit. Thus it can be concluded that the required
CO2 purity was outbalanced in the pilot plant.
Specification / Product CO2
CO2 Purity [mole %]
O2 [ppmwt] (max)
N2 [mole %]
H2O [ppmwt] (max)
H2S [ppmwt] (max)
Others
> 99.6 (balance)
< 200
< 0.2
to be agreed prior to contract award
< 100
to be agreed prior to contract award
Table 4: CO2 product quality specified for CCM project, license package agreement
The installed measuring devices for steam and electrical power consumption posed some
challenges during operation. For steam measurement an equivalent alternative was found and
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witnessed by an independent third party to provide accurate information about steam input.
As a countermeasure for the recording approach of electrical power consumption, measured
data taken from frequency converters were extracted manually.
The investigation on performance of PostCapTM solvent from different suppliers (referred to
as solvent type I and type II) showed following results:
• Absorption-desorption experiments gave similar results for both solvents. No
significant difference in carbon capture performance could be detected.
• Emission measurements showed that there are no relevant differences in solvent
emission behavior.
• The results of further analyses, especially on solvent composition, indicate similar
degradation behavior for both solvents.
5.2.2
Operability
Several operation modes were successfully tested, such as start-up, shut-down and automatic
stand-by (with minimum solvent circulation at a well-defined heat input). The latter is
advantageous with respect to short reaction times to process interruptions upstream of the
capture plant.
Solvent behaviour with regards to foaming and plugging was no issue at all. Foaming, which
was observed at the desorber only, could be easily handled by respective counter-measures.
An antifoam agent was identified and tested successfully.
5.2.3
Process model validation
Coal fired: Several parameter variations have been performed and the simulation model was
successfully validated. Good accordance between the measured and predicted temperature
profiles in the absorber and desorber was obtained by adjusting the interfacial area factor
(IAF) and the heat transfer factor (HTF) in the simulation model. The IAF expresses the ratio
of the effective and the geometric mass transfer area and has to be adjusted, since the
hydrodynamic correlations within the used process simulation software Aspen Plus ® are
based on the reference system CO2 ↔ NaOH. With respect to the HTF, Aspen Plus ® advises
to set it to be reciprocal to the IAF.
Gas fired: The validated process model for coal fired operation was used as starting point for
the investigations of CCM Full Scale Design. Based on the comparison of selected pilot plant
operational data during 3000 hrs operation and the simulation results it was confirmed that a
further adaption / tuning of the process model was not necessary to reliably model the real
process behaviour. For comparison of measured and simulated temperature profiles and mass
balance an acceptable good accordance has been achieved for all evaluated operation periods.
Comparison of measured and simulated solvent cycle capacities (ΔRich/Lean CO2 Loading)
led to good conformity.
Pilot plant process data were used to validate the process model energy balance. Besides
considering the pure energy balance, the process model further considers mass balance as
well as temperature profiles, solvent concentration and loadings. By comparison of measured
and simulated specific energy demand it can be seen that a good accordance has been
achieved. This additionally confirms the process model validation. A further process model
adaption was not necessary to reliably model the real process behaviour. For a design capture
rate of 90 % the measured specific energy demand was below the simulated energy demand,
hence process model results can be understood to be conservative (Figure 9).
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05
.0
2.
20
13
13
.1
2.
20
12
29
.0
1.
20
13
04
.1
2.
20
12
09
.1
2.
20
12
20
.1
1.
20
12
26
.1
1.
20
12
06
.1
1.
20
12
14
.1
1.
20
12
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
24
.1
0.
20
12
01
.1
1.
20
12
GJ/ t CO2
Measured and Simulated specific energy demand excluding heat loss
Specific Energy Demand Desorption excl. Experimental Heat Losses of 2.4. KW
Simulated Specific Energy Demand Desorption excl. Heat Losses
Figure 9: Measured energy demand versa simulated energy demand during TQP
5.2.4
Material tests
Coal based flue gas: AISI 316Ti (AISI = American Iron and Steel Institute) is used as main
construction material in the pilot plant. Corrosion tests showed that AISI 316Ti as well as
AISI 316L can be used as construction material for parts in contact with solvent under the
typical process conditions. Based on these results AISI 316L is now selected as the standard
material for PostCap™ plants with flue gas from coal fired power plants due to expected
better availability on the world market and lower costs.
Natural gas based flue gas: Long term tests (1000 h + 2000 h) were executed. All tested
materials were confirmed to be corrosion resistant (see Figure 10). Both AISI316L and
AISI304L showed a uniform attack, which is however very minimal. Quantification figures
would in the worst case lead to 17 µm loss after the design lifetime of 25 years. This is
tolerable even for the structured packing, which consists of metal sheets of 100 µm. For FG
cooler condensate section (acidic CO2 Product condensate), both AISI 904L and titanium can
be used; no corrosion is detected.
Originally AISI 316L was foreseen as construction material for full-scale plants with gas
based flue gas as well. As AISI 304L showed comparable stability in all tests, it is now
selected as the standard material for PostCap™ plants with flue gas from natural gas
combustion. This results in a considerable saving in capital expenses (CAPEX).
Figure 10: Material test samples before and after test
5.2.5
Emission measurements & liquid analysis
Nine high standard campaigns for emission measurements, nine liquid analyses of solvent
and five reclaimer analyses were successfully executed by Siemens during TQP. Furthermore
five measurement campaigns were conducted by third parties. The degradation products in
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the solvent and their behaviour were observed, and the main reaction pathways are well
understood.
The main degradation compounds accumulated in the solvent were formates/acetate, oxalate
and – to a smaller extent – alkyl amines, as well as the non-volatile nitrosamines. After
starting the reclaimer operation the concentration of non-volatile nitrosamine in the liquid
solvent pump around was successfully kept constant at a desired level (see Chapter 5.2.6,
Figure 11).
Amines, ammonia and aldehydes originating from decomposed solvent were emitted to the
atmosphere as volatile compounds. The concentration of amines and acetaldehyde at the
absorber outlet were approximately constant after starting the reclaiming. The detected values
were within the limits that are expected for full scale applications. During the additional
measurements in August/September 2013 the level of ammonia concentration could be linked
to the concentration of metals which act as a catalyst for the degradation. During the
laboratory tests between April and August 2014 this relation could be further quantified.
The emission of droplets was in all but two campaigns, even during the verification of
demisting technology with increased gas load, below the very low detection limit. In the two
campaigns where droplets were detected, the concentration of the solvent in the droplets was
very low, resulting in a solvent content in decarbonized flue gas of 20 to 50 µg/m3. As a
consequence the demisting technology can be seen as sufficient to avoid droplet emissions.
5.2.6
Verification of reclaiming technology
During the coal fired operation of the pilot plant the reclaimer technology was thoroughly
tested for both modules (SOx and NOx). The functionality was successfully proven and the
performance was validated. As a result of these tests the reclaimer design could be further
optimised, e.g. the crystallization process in both modules was reduced from two steps to one
step.
The Siemens reclaiming technology at gas fired operation of the pilot plant was successfully
verified by operation of the reclaimer pilot plant as shown in Figure 11. No unexpected
deviation compared to the full scale reclaiming concept appeared. Operability was satisfying.
No blocking by solid particles, no reclaimer pilot plant shut down and no malfunctions
occurred within reclaimer pilot plant operation. The scale-up tests for the full scale use of a
belt filter and a centrifuge within the Reclaimer were successfully executed together with
corresponding suppliers. The suppliers stated the suitability of their equipment for the desired
solid-liquid separation and they determined the necessary process and product property data
for a reliable equipment design. The reclaimer operation and the scale up test during the TQP
were witnessed by the Customer and a third party.
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Figure 11: Reclaimer effect on non-volatile nitrosamine concentration in solvent
A robust performance of the NOx reclaimer based on conservative assumptions was
confirmed. It should be emphasized that the NO2 input at the pilot plant flue gas at gas fired
operation was much higher than given by the design base, however the observed waste
stream was even lower than expected.
The very low (but in-spec) SOx-concentrations in the flue gas of the pilot plant under gas
fired operation lead to a very low accumulation of potassium sulphate in the solvent.
Nevertheless this low uptake was separated by the SOx-reclaimer and the sulphate level in the
solvent was also kept constant. Applying the washing step in the centrifuge a clean potassium
sulphate product was gained, that meets the specifications of e.g. fertilizer manufactures for a
further utilization.
5.3 Summary
5.3.1 Pilot plant operation with coal and gas fired flue gas
A total of more than 9,000 hours of operation was successfully conducted at the PostCap™
pilot plant located at the Staudinger power plant :
-
-
5.3.2
The targets in focus as listed in chapter 2.2 of this paper were achieved for both flue
gas sources - coal fired and gas fired.
The performance of the amino acid salt based solvent and the chosen process and
mechanical features as well as the simulation model and the control concept were
validated under realistic industrial conditions.
The Reclaimer operation was successfully tested for both modules (SOx and NOx)
with different flue gas compositions/by-products as they are specific for coal fired and
gas turbine power plants.
Technology Qualification Program (TQP) for CCM project (gas fired)
The proposed TQP was executed as agreed with Statoil/Gassnova. More than 3000 hours of
“in-spec” operation were successfully accomplished on 2013-03-27 by 24/7 operation. The
total "in-spec" availability of the carbon capture plant relative to operating hours with flue
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gas, results in 93 %. Pilot plant operation in combination with the Reclaimer was very stable.
All performance parameters such as liquid hold ups, temperature profiles, capture rate, steam
input, flue gas composition (with regards to O2 and CO2) showed stable behaviour during the
3000 “in-spec” operating hours.
6 Scalability and constructability
Based on the results of the pilot plant operation, a scale-up of the PostCap™ technology to
large-scale demonstration and full-scale projects is possible. The technology had been chosen
as a basis of project development by several large-scale projects globally for the design of
CO2 capture plants to be optimally integrated into either new-build power plants or to be
retrofitted to existing ones. Figure 12 shows the layout of a full scale plant that was
developed during the concept study for the Carbon Capture Mongstad (CCM) project. Details
on the scale-up procedure and results can be found in [8].
In addition a detailed constructability study was conducted by Siemens for the CCM project
to prove that a full scale plant and the respective large and heavy equipment can be
manufactured, transported and assembled on site.
Figure 12: PostCap™ full scale plant, layout for CCM project
7 References
[1]
Stoffregen, Torsten, et al: Pilot-scale demonstration of an advanced aqueous aminebased post-combustion capture technology for CO2 capture from power plant flue gases,
Energy Procedia 63 ( 2014 ) 1456 – 1469
[2]
Radgen, Peter, et al: Lessons Learned from the Operation of a 70 Tonne per Day Post
Combustion Pilot Plant at the Coal Fired Power Plant in Wilhelmshaven, Germany, Energy
Procedia 63 ( 2014 ) 1585 – 1594
[3]
Kay, John P., et al: Pilot-scale evaluations of advanced solvents for post combustion
CO2 capture, Energy Procedia 63 ( 2014 ) 1903 – 1910
[4]
Goedecke, Ralf: Fluidverfahrenstechnik, Wiley-VCH Verlag GmbH & Co. KGaA;
Auflage: 1. Auflage (2006)
[5]
Melcher, Berthold, et al: Validation, operation and smart full-scale design of an
efficient reclaiming system for carbon capture solvents based on amino acid salt, Energy
Procedia 63 ( 2014 ) 676 – 686
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[6]
Jockenhövel, Tobias, et al: Validation of a second-generation post-combustion
capture technology – Results from POSTCAP pilot plant operation, PowerGen Europe 2010
[7]
Jockenhövel, Tobias, et al: Towards Commercial Application of a Second-Generation
Post-Combustion Capture Technology – Pilot Plant Validation of the Siemens Capture
Process and Implementation of First Demonstration Case, Energy Procedia 4 (2011) 1451–
1458
[8]
Reichl, Albert, et al: Process development and scale-up for post combustion carbon
capture - validation with pilot plant operation, Energy Procedia 63 ( 2014 ) 6379 – 6392
8 Acknowledgements
Siemens gratefully acknowledges the following for their support and collaborative
development of projects mentioned in this paper. In chronological order:
• The BMWi (Bundesministerium für Wirtschaft und Energie – German Federal
Ministry for Economic Affairs and Energy) for funding of the Siemens POSTCAP
development project
• E.ON SE for co-funding of the Siemens POSTCAP development project and
providing facilities for erection and operation of the pilot plant
• The Norwegian Government and Gassnova, funders of the carbon capture project
Mongstad (CCM)
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