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Oxy-coal combustion and its integration with power systems for CO2 capture
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Oxy-fuel combustion is one of the technologies for carbon dioxide (CO2) capture and storage (CCS) in fossil fuel based power systems to mitigate global greenhouse gases (GHGs) emissions. When introducing oxy-fuel combustion into the power systems, energy penalty for CCS has significant impacts on the system performance. The heat and mass balance of the oxy-fuel combustion power system need to be investigated due to the change of combustion environment.

 

This study investigated oxy-fuel combustion with coal as the fuel, so called oxy-coal combustion, and its integration with power systems for CO2 capture. First, mass balance was formulated for the oxy-coal combustion considering flue gas recycle (FGR). Then, computational fluid dynamic (CFD) modelling was conducted on the oxy-coal combustion to identify its characteristics in terms of flame profile and radiation heat transfer. Finally, process simulation was performed on the oxy-coal combustion power system to evaluate its technical and economic performance including the subsystems of air separation unit (ASU), furnace/boiler, and cryogenic CO2 purification. In addition, a new peak and off-peak (POP) operation mode of ASU to shift the energy penalty for CCS and improve the performance of the whole system was addressed and analysed by net present value method.

 

The results show that oxy-coal combustion can match well to conventional (air-coal) combustion under specific operating conditions, and results in a minimal change of existing boilers under conventional technology. The increase of moisture content in the flue gas has little impact on the flame temperature, but results in a higher surface incident radiation on boiler side walls. Compared with air-coal combustion power systems, oxy-coal combustion power systems have much lower flow rate of flue gas, lower NO and SO2 emissions, higher boiler efficiency, but a higher flue gas dew point. Furthermore, various FGR options in the oxy-coal combustion power system have no clear effect on recycle ratio, flow rate of flue gas, and electrical efficiency of the whole system, but cause much different flue gas compositions at the exit of the boiler. Energy penalty for ASU in the oxy-coal combustion power system accounts for about 7% based on low heating value. Comparatively, ASU has a larger effect than cryogenic CO2 purification on energy consumption in the oxy-coal combustion power system. The new POP operation mode of ASU is technically and economically feasible for shifting the energy use of ASU in the peak and off-peak periods, and more electricity could be generated at a higher price.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xiv, 60 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:4
Keyword [en]
oxy-coal combustion; flue gas recycle; radiation; peak and off-peak operations; cryogenic CO2 purification
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-116575ISBN: 987-91-7501-612-2 OAI: oai:DiVA.org:kth-116575DiVA: diva2:591653
Public defence
2013-02-08, K1, Teknikringen 56, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130122

Available from: 2013-01-22 Created: 2013-01-21 Last updated: 2013-01-22Bibliographically approved
List of papers
1. Numerical study of radiative heat transfer in oxy-coal combustion with flue gas recirculation
Open this publication in new window or tab >>Numerical study of radiative heat transfer in oxy-coal combustion with flue gas recirculation
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-116572 (URN)
Note

QS 2013

Available from: 2013-01-21 Created: 2013-01-21 Last updated: 2013-01-22Bibliographically approved
2. Characteristics of radiation heat transfer in utility boilers under oxy-coal combustion condition
Open this publication in new window or tab >>Characteristics of radiation heat transfer in utility boilers under oxy-coal combustion condition
2013 (English)Conference paper, Published paper (Refereed)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-116571 (URN)
Conference
International Conference on Applied Energy, Pretoria, South Africa, July 1-4.
Note

QC 20130121

Available from: 2013-01-21 Created: 2013-01-21 Last updated: 2013-01-22Bibliographically approved
3. Characterization of flue gas in oxy-coal combustion processes for CO2 capture
Open this publication in new window or tab >>Characterization of flue gas in oxy-coal combustion processes for CO2 capture
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 90, no 1, 113-121 p.Article in journal (Refereed) Published
Abstract [en]

Oxy-coal combustion is one of the technical solutions for mitigating CO2 in thermal power plants. For designing a technically viable and economically effective CO2 capture process, effects by coals and configurations of flue gas cleaning steps are of importance. In this paper, characterization of the flue gas recycle (FGR) is conducted for an oxy-coal combustion process. Different configurations of FGR as well as cleaning units including electrostatic precipitators (ESP), flue gas desulfurization (FGD), selective catalytic reduction (SCR) deNOx and flue gas condensation (FGC) are studied for the oxy-coal combustion process. In addition, other important parameters such as FGR rate and FGR ratio, flue gas compositions, and load of flue gas cleaning units are analyzed based on coal properties and plant operational conditions.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Oxy-coal combustion; Mass balance; CO2 capture; Flue gas cleaning
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-48631 (URN)10.1016/j.apenergy.2011.03.005 (DOI)000297426100018 ()2-s2.0-80055036207 (Scopus ID)
Note
QC 20111122, QC 20120109Available from: 2011-11-22 Created: 2011-11-22 Last updated: 2017-12-08Bibliographically approved
4. Effects of flue gas recycle on oxy-coal power generation systems
Open this publication in new window or tab >>Effects of flue gas recycle on oxy-coal power generation systems
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, 255-263 p.Article in journal (Refereed) Published
Abstract [en]

This paper examined and assessed various configuration options about emission removal including particles, SO x and NO x in an oxy-coal combustion system for CO 2 capture. A performance analysis was conducted in order to understand the impacts of those options concerning process design, process operation and system efficiency. Results show that different flue gas recycle options have clear effects on the emissivity and absorptivity of radiating gases in boiler due to the change of flue gas compositions. The maximum difference amongst various options can be up to 15% and 20% for emissivity and absorptivity respectively. As a result, the heat transfer by radiation can vary about 20%. The recycle options also have impacts on the design of air heater and selective-catalytic-reduction (SCR) preheater. This is due to that the largely varied operating temperatures in different options may result in different required areas of heat exchangers. In addition, the dew point of flue gas and the boiler efficiency are affected by the configurations of flue gas recycle as well.

Keyword
CO 2 capture, Dew point of flue gas, Flue gas recycle, Oxy-coal combustion, Radiation
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-100282 (URN)10.1016/j.apenergy.2011.12.096 (DOI)000307196000030 ()2-s2.0-84862777767 (Scopus ID)
Note

QC 20120807

Available from: 2012-08-07 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
5. Optimization of cryogenic CO2 purification for oxy-coal combustion
Open this publication in new window or tab >>Optimization of cryogenic CO2 purification for oxy-coal combustion
Show others...
2013 (English)In: Energy Procedia, Elsevier, 2013, 1341-1347 p.Conference paper, Published paper (Refereed)
Abstract [en]

Oxyfuel combustion is a leading potential CO2 capture technology for power plants. As the flue gas (FG) consists of mainly H2O and CO2, a simpler and more energy-efficient CO2 purification method can be used instead of the standard amine-based chemical absorption approach. For the system of oxyfuel combustion with cryogenic CO2 purification, decreasing the oxygen purity reduces the energy consumption of the Air Separation Unit (ASU) but increases the energy consumption for the downstream cryogenic purification. Thus there exists a trade-off between the energy consumption of the ASU and that for cryogenic purification. This paper investigates the potential efficiency improvement by optimizing this trade-off. The simulated results show that there exists an optimum flue gas condensing pressure for the cryogenic purification, which is affected by the flue gas composition. In addition, decreasing the oxygen purity reduces the combined energy consumption of the ASU and the cryogenic purification, and therefore can improve the electrical efficiency. In summary, prior oxyfuel combustion analyses have assumed a high oxygen purity level of 95 mol% or 99 mol% for the combustion air, which achieves a high CO2 concentration in the flue gases. In this Paper, we demonstrate that a lower level of oxygen purity, such as 80 mol%, in conjunction with a more extensive cryogenic purification of the flue gases can lower the total energy consumption, thereby yielding a significant benefit. However, for oxygen purity levels lower than 75 mol%, it may not be possible to still use the two-stage flash system shown here to achieve a CO2 purity of 95 mol% and a CO2 recovery rate of 90% simultaneously.

Place, publisher, year, edition, pages
Elsevier, 2013
Series
Energy Procedia, ISSN 1876-6102 ; 37
Keyword
CO2 capture and storage (CCS), CO2 purity, CO2 recovery rate, Cryogenicpurification, Energy consumption, Oxy-coal combustion, Oxygen purity
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-116576 (URN)10.1016/j.egypro.2013.06.009 (DOI)000345500501065 ()2-s2.0-84898754949 (Scopus ID)
Conference
11th International Conference on Greenhouse Gas Control Technologies, GHGT 2012; Kyoto; Japan; 18 November 2012 through 22 November 2012
Note

QC 20140627. Updated from submitted to published.

Available from: 2013-01-22 Created: 2013-01-21 Last updated: 2015-10-06Bibliographically approved
6. Peak and off-peak operations of the air separatino unit in oxy-fuel combustion power generation systems
Open this publication in new window or tab >>Peak and off-peak operations of the air separatino unit in oxy-fuel combustion power generation systems
2013 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 112, no SI, 747-754 p.Article in journal (Refereed) Published
Abstract [en]

Introducing CO2 capture and storage (CCS) into the power systems requires the re-investigation of the load balance for the electrical grid. For the oxy-coal combustion capture technology, the energy use of ASU can be shifted between the peak-load and off-peak-load periods, which may bring more benefits. In this paper, peak and off-peak (POP) operations for the air separation unit (ASU) with liquid oxygen storage were studied based on a 530 MW coal-fired power system. According to the simulation results, the oxy-coal combustion power system running POP is technically feasible that it can provide a base load of 496 MW during the off-peak period and a peak load of 613 MW during the peak period. And the equivalent efficiency of the power system running POP is only 0.3% lower than the one not running POP. Moreover, according to the economic assessments based on the net present value, it is also economically feasible that the payback time of the investment of the oxy-coal combustion power system running POP is about 13 years under the assumptions of 10% discount rate and 2.5% cost escalation rate. In addition, the effects of the difference of on-grid electricity prices, daily peak period, investment for POP operations, and ASU energy consumption were also analyzed, concerning the net present value.

Keyword
Oxy-coal combustion, Air separation unit (ASU), Peak and off-peak operations, CO2 capture, Economic assessment
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-116567 (URN)10.1016/j.apenergy.2012.12.001 (DOI)000329377800080 ()2-s2.0-84884211048 (Scopus ID)
Conference
4th International Conference on Applied Energy (ICAE), July 01-04, 2012
Note

QC 20140210

Available from: 2013-01-21 Created: 2013-01-21 Last updated: 2017-12-06Bibliographically approved
7. Techno-economic evaluation of the evaporative gas turbine cycle with different CO2 capture options
Open this publication in new window or tab >>Techno-economic evaluation of the evaporative gas turbine cycle with different CO2 capture options
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 89, no 1, 303-314 p.Article in journal (Refereed) Published
Abstract [en]

The techno-economic evaluation of the evaporative gas turbine (EvGT) cycle with two different CO2 capture options has been carried out. Three studied systems include a reference system: the EvGT system without CO2 capture (System I), the EvGT system with chemical absorption capture (System II), and the EvGT system with oxyfuel combustion capture (System III). The cycle simulation results show that the system with chemical absorption has a higher electrical efficiency (41.6% of NG LHV) and a lower efficiency penalty caused by CO2 capture (10.5% of NG LHV) compared with the system with oxyfuel combustion capture. Based on a gas turbine of 13.78 MW, the estimated costs of electricity are 46.1 $/MW h for System I, while 70.1 $/MW h and 74.1 $/MW h for Systems II and III, respectively. It shows that the cost of electricity increment of chemical absorption is 8.7% points lower than that of the option of oxyfuel combustion. In addition, the cost of CO2 avoidance of System II which is 71.8 $/tonne CO2 is also lower than that of System III, which is 73.2 $/tonne CO2. The impacts of plant size have been analyzed as well. Results show that cost of CO2 avoidance of System III may be less than that of System II when a plant size is larger than 60 MW.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
CO2 capture, Evaporative gas turbines, Chemical absorption, Oxyfuel combustion, Cycle simulation, Economic evaluation
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-48639 (URN)10.1016/j.apenergy.2011.07.034 (DOI)000296114700036 ()2-s2.0-80053350189 (Scopus ID)
Note
QC 20111122Available from: 2011-11-22 Created: 2011-11-22 Last updated: 2017-12-08Bibliographically approved

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Permanent link

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
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  • text
  • asciidoc
  • rtf