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Effects of flue gas recycle on oxy-coal power generation systems
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
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.

Place, publisher, year, edition, pages
2012. Vol. 97, 255-263 p.
Keyword [en]
CO 2 capture, Dew point of flue gas, Flue gas recycle, Oxy-coal combustion, Radiation
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-100282DOI: 10.1016/j.apenergy.2011.12.096ISI: 000307196000030Scopus ID: 2-s2.0-84862777767OAI: oai:DiVA.org:kth-100282DiVA: diva2:543240
Note

QC 20120807

Available from: 2012-08-07 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Oxy-coal combustion and its integration with power systems for CO2 capture
Open this publication in new window or tab >>Oxy-coal combustion and its integration with power systems for CO2 capture
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
oxy-coal combustion; flue gas recycle; radiation; peak and off-peak operations; cryogenic CO2 purification
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-116575 (URN)987-91-7501-612-2 (ISBN)
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

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