Process Modelling for Amine-based Post-Combustion Capture Plant

78 Pages·2014·2.24 MB·English

CSIRO ENERGY TECHNOLOGY/ENERGY TRANSFORMED FLAGSHIP

Environmental Impacts of
amine-based CO Post
2
Combustion Capture (PCC)
Process

Task 3: Process Modelling for Amine-based Post-Combustion
Capture Plant

Narendra Dave, Thong Do, Merched Azzi, Paul Feron
15 July 2012
Prepared for Australian National Low Emissions Coal Research and Development
Project: 4-090-0067
Final Submission

Australian National Low Emissions Coal Research & Development
CSIRO Energy Technology/Energy Transformed Flagship
Citation
Dave N, Do T, Azzi M and Feron P (2013). Process Modelling for Amine-based Post-Combustion Capture
Plant. CSIRO, Australia.
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Process Modelling for Amine-based Post-Combustion Capture Plant
Contents
Acknowledgments .............................................................................................................................................. 4
Summary ............................................................................................................................................................ 5
Part I Current State of Post-Combustion Capture Knowledge 2
1 Introduction .......................................................................................................................................... 3
2 Current State of PCC knowledge .......................................................................................................... 4
Part II Atmospheric Emissions of Monoethanolamine (MEA) and Its degradation products 16
3 Summary of the Latest Existing Information Related to Emissions from PCC .................................... 17
3.1 Esbjergvaerket Pilot Plant Results ............................................................................................ 17
3.2 National Carbon Capture Centre Pilot Solvent Tests Unit Results ........................................... 23
3.3 SINTEF CO Capture Mongstad Technology Qualification Program Amine 6
2
Research Results – Pilot Plant ............................................................................................................ 26
3.4 SINTEF CO2 Capture Mongstad Technology Qualification Program Amine 6
Research Results – Laboratory Results ............................................................................................... 29
4 Atmospheric Emissions of 2-amino-2-methyl-1-propanol (AMP)/ piperazine Blend and its
Degradation Products ...................................................................................................................................... 38
4.1 Oxidative Degradation of 2-amino-2-methyl-1-propanol (AMP)/Piperazine Blend ................ 39
4.2 Thermal Degradation of 2-amino-2-methyl-1-propanol (AMP)/Piperazine Blend .................. 40
Part III ASPEN-Plus Simulation Results 42
5 Improved ASPEN-Plus Estimations of Atmospheric Emissions ........................................................... 43
5.1 Improving Emissions Estimates of Monoethanolamine and its Degradation
Products .............................................................................................................................................. 44
5.2 Methodology & Results ............................................................................................................ 44
5.3 Analysis of Aspen-Plus Generated Atmospheric Emission Estimates ...................................... 57
6 Significance of Pilot Plant Performance Data and ASPEN-Plus Emissions Estimates For
Australia ........................................................................................................................................................... 58
7 Conclusions ......................................................................................................................................... 60
8 Recommendations for future work .................................................................................................... 63
References ....................................................................................................................................................... 65

Process Modelling for Amine-based Post-Combustion Capture Plant 3
Acknowledgments
The authors wish to acknowledge financial assistance provided through Australian National Low
Emissions Coal Research and Development (ANLEC R&D). ANLEC R&D is supported by Australian Coal
Association Low Emissions Technology Limited and the Australian Government through the Clean
Energy Initiative.
The authors would like to thank the appointed ANLEC Reviewers Geoff Bongers and Peter Nelson for
their detailed comments.

Process Modelling for Amine-based Post-Combustion Capture Plant 4
Summary
This report is the final project deliverable of the Activity 3 entitled “Process modelling for amine-
based CO Post Combustion Capture plant”. This activity was carried out as one of the five activities
2
of the project funded by ANLEC R&D “Environmental Impacts of Amine-based CO Post Combustion
2
Capture (PCC) Process”. The model-based process simulation software ASPEN-Plus, was used to
simulate the anticipated atmospheric emissions from an amine-based CO2 PCC plant.
This report is an extension of the previous work reported to the ANLEC R&D as Tasks 3.1 and 3.2
Milestone Reports for the project. It includes additional public domain information on the oxidative
and thermal degradation of monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP),
piperazine (PZ) and their blends, as observed during laboratory experiments and pilot plant trials. It
also reports the likely emissions of these solvents and their degradation products to the
atmosphere, if they were to be used to reduce CO emissions from an Australian black coal-fired
2
power generation plant.
Amines are mainly lost in an amine-based absorption/stripping system due solvent vaporisation,
amine entrainment in the flue gas and amine degradation in the process. The two firsts occur at the
top of the absorber column causing amine emissions to the air. ASPEN simulation results showed
that a well designed water wash column can be used to recover most of the amine losses by
volatility.
Solvent degradation can also occur through irreversible side reactions with different constituents in
the flue gas such as O , NO and SO to produce volatile and non-volatile degradation products.
2 x x
These products affect the CO2 absorption capacity of the solvent, corrosion, increase viscosity and
provoke release of volatile degradation pollutants to the atmosphere. The process simulations
undertook in the current study considered the degradation behaviour and possible degradation
pathways for selected amines to predict the potential releases to the atmosphere of major
degradation products from the PCC plant for optimised operating conditions.
Due to limitations of the analytical and emission measurement techniques, the solvent degradation
products have not yet been fully identified and quantified. However, various pilot plant-performance
data point to mist and aerosols formation during CO capture, and their contribution to the total
2
emissions of parent amines and their degradation products from absorbers.
Particulate matter and fly ash present in coal-fired power plant flue gas are now known to act as
seeds for heterogeneous condensation or nucleation for aerosol formation. Similarly, SO present in
3
this gas stream at concentrations as low as 1 ppmv can potentially contribute to sulphuric acid mist
formation, which gives opacity to the CO lean gas stream. Sudden quenching of the water-saturated
2
gas within the absorber also causes homogeneous nuclei formation via condensation. These nuclei
grow by condensation and dissolution of amine vapours and its degradation products, forming
sub-micron size aerosols. Brink mist eliminator-type candle filters are only 65–90% effective against
aerosols of <0.8 µm, as reported by the Maasvlakte pilot plant operated at the EON power plant in
Europe. The pilot plant data also reveals that the use of such Brownian diffusion units causes the
pressure drop across the CO absorber to rise. This results in a 7% increase in electrical energy
2
demand for the gas blower that pumps flue gas through the gas absorption tower.
The atmospheric emissions resulting from using a 3 M AMP and 2 M PZ blend as a solvent have
been studied in Dong Energy’s Esbjergvaerket pilot plant and EON’s Maasvlakte pilot plant.
Unfortunately, the potential atmospheric emissions of oxidative and thermal degradation products
of AMP and PZ were not tracked or quantified in these trials. Nevertheless, the sensitivity of AMP/PZ
Process Modelling for Amine-based Post-Combustion Capture Plant 5
atmospheric emissions to the process operating parameters for the wash tower observed at the
pilot plant scale is in the same range as that predicted by the Aspen-Plus process simulation
software, and reported to ANLEC R&D in our Task 3.2 project report in 2012.
The atmospheric emissions of MEA and its degradation products have been studied with a greater
degree of clarity than the AMP/PZ blend. Studies undertaken at SINTEF (Scandinavia’s largest
independent research organisation), funded by Norway’s full-scale CO2 Capture Mongstad (CCM)
project, have provided more detailed and useful information on the topic. SINTEF has emulated
industry practice at the laboratory scale with their solvent degradation rig. They measured the rate
of formation and accumulation of various degradation products of MEA, including alkylamines,
nitrosamines and nitramines.
The results of the SINTEF study, though strictly valid for processing natural-gas-fired flue gas, were
used for estimating the atmospheric emissions of MEA degradation products at the industrial scale
when processing black coal-fired power plant flue gas using the Aspen-Plus process simulation
software. The results from these simulations are given in Table 1 and compared with Task 3.1’s
results.
Process Modelling for Amine-based Post-Combustion Capture Plant 6
Table 1 Comparison of latest predicted atmospheric emissions with those reported in Task 3.1 report at 40 °C

Compound New estimate of atmospheric emissions Atmospheric emissions (Task 3.1 report)
mg/Nm3 dry CO lean gas mg/tonne CO mg/Nm3 dry CO lean gas mg/tonne CO
2 2 2 2
Minimum Maximum Minimum Maximum Minimum Maximum Minimum Maximum
Monoethanolamine (MEA) 1.08E-01 1.08E-01 3.60E+02 3.60E+02 1.4E-01 1.4E-01 4.36E+02 4.43E+02
Diethanolamine (DEA) 2.02E-09 2.31E-06 6.77E-06 7.76E-03 0.00E+00 3.0E-05 0.00E+00 8.4E-02
2-oxazolidone (OZD) 9.51E-09 1.09E-08 3.19E-05 3.66E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00
N,N’-bis(2-hydroxyethyl)oxalamide (BHEOX) 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00
N-(2-hydroxyethyl)acetamide (HEA) 3.73E-12 4.27E-12 1.25E-08 1.43E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00
N-(2-hydroxyethyl)-glycine (HEGly) 6.67E-12 7.63E-12 2.24E-08 2.56E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00
4-(2-hydroxyethyl)piperazin-2-one (HEPO) 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00
N-(2-hydroxyethyl)formamide (HEF) 5.33E-13 6.10E-13 1.79E-09 2.05E-09 0.00E+00 0.00E+00 0.00E+00 0.00E+00
N-(2-hydroxyethyl)imidazole (HEI) 1.47E+01 1.52E+01 4.92E+04 5.11E+04 0.00E+00 0.00E+00 0.00E+00 0.00E+00
MEA-NO (Nitramine) 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00
2
Ammonia 1.08E-01 6.59E+00 3.63E+02 2.21E+04 1.0E-03 1.2E-01 2.8E+00 3.74E+02
Dimethylamine 1.04E+00 1.04E+00 3.47E+03 3.49E+03 0.00E+00 0.00E+00 0.00E+00 0.00E+00
Methylamine 1.00E+01 1.00E+01 3.36E+04 3.37E+04 2.1E-01 2.2E-01 6.68E+02 7.03E+02
Ethylamine 3.78E-01 3.80E-01 1.27E+03 1.28E+03 0.00E+00 0.00E+00 0.00E+00 0.00E+00
Diethylamine 1.32E-02 1.35E-02 4.42E+01 4.53E+01 0.00E+00 0.00E+00 0.00E+00 0.00E+00
Nitrosodiethylamine (NDEA) 5.02E-09 5.72E-09 1.68E-05 1.92E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00
Nitrosodimethylamine (NDMA) 7.29E-08 8.27E-08 2.44E-04 2.78E-04 0.00E+00 0.00E+00 0.00E+00 0.00E+00
Nitrosodiethanolamine (NDELA) 6.65E-02 6.72E-02 2.23E+02 2.26E+02 0.00E+00 0.00E+00 0.00E+00 0.00E+00
Process Modelling for Amine-based Post-Combustion Capture Plant 7
Nitrosomorpholine 1.95E-06 2.17E-06 6.54E-03 7.28E-03 0.00E+00 3.0E-06 8.9E-03 8.9E-03
Formaldehyde 2.69E-01 2.74E-01 9.02E+02 9.19E+02 2.6E-01 2.7E-01 8.48E+02 8.85E+02
Acetone 8.13E-02 1.00E-01 2.73E+02 3.37E+02 3.1E-01 3.3E-01 1.01E+03 1.08E+03
Acetaldehyde 1.56E-01 1.66E-01 5.22E+02 5.58E+02 3.0E-01 3.0E-01 9.34E+02 9.66E+02
Acetamide 2.08E-07 9.60E-05 6.98E-04 3.22E-01 0.00E+00 1.1E-03 0.00E+00 4.0E-01

Process Modelling for Amine-based Post-Combustion Capture Plant 8
The revised Aspen-Plus results confirm that:

(1) The extent of degradation of MEA, and the distribution of its degradation products occurring
when processing black coal-fired power plant flue gas, could be similar to that occurring when
processing a natural-gas-fired flue gas stream.

(2) Though a greater number of different thermal degradation products have been identified by the
55
solvent degradation rig study than in the work done by Davis (which was the basis for the
Task 3.1 work), these products are unlikely to be emitted to the atmosphere.

(3) Nitramines are unlikely to be an atmospheric emission issue, because their carryover with
CO -lean gas leaving the absorber section is below ppbv levels.
2

(4) The formation of nitrosamines is driven by the presence of the secondary amine DEA
produced as a by-product of the MEA degradation when the later is used as a solvent to
capture CO . The extent of emissions will depend upon what measures have been put in place
2
with regard to efficient working of the water wash tower.

(5) The wash water stream (WW1) leaving the wash tower has a noticeable level of alkylamines
and nitrosamines. Thus, the effective disposal of wash water should be assessed for a
full-scale capture plant. This also applies to the in-line activated carbon filters that are used
after the trim cooler to control the build-up of organic acids and phenolic compounds in the lean
solvent in an amine-solvent-based CO capture plant.
2

The pilot scale trials so far confirm that accuracy of emission quantification depends on the:
 sampling techniques employed
 frequency of calibration of on and off-line instruments
 type of filters, sorbents, water traps, etc. used in the sampling lines
 handling and storage condition of samples for any off-line analysis.

More research and standardisation work needs to be done to build confidence in the numerical
accuracy and reproducibility of these measurements.
In light of the above limitations, the following work program is proposed:

(1) Identify, evaluate and standardise various on and off-line techniques and instruments suited for
the CO capture environment of a demonstration plant to quantify the emissions of various
2
inorganic and organic species.
(2) Identify, evaluate and rank various solvent degradation and corrosion inhibitors, at bench and
pilot scales, which could minimise solvent degradation and atmospheric emissions in full-scale
amine-solvent-based post-combustion capture (PCC) technologies.
(3) Fully characterise and quantify degradation products of amine solvents, both in the gas and
liquid streams, in an Australian pilot scale PCC plant. The plant chosen should operate at
steady state in gas–liquid flow regimes representative of current industrial-scale PCC plants.
(4) Develop process improvements around the direct contact cooling (DCC) tower and the water
wash towers downstream of both absorber and stripper in an Australian pilot plant, to minimise
first, the adverse impact of flue gas impurities on amine solvents, and second, the atmospheric
emissions of amine solvents and their degradation products.
i Process Modelling for Amine-based Post-Combustion Capture Plant
Part I Current State of
Post-Combustion
Capture
Knowledge

Process Modelling for Amine-based Post-Combustion Capture Plant 2