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Peak and off-peak operations of the air separatino unit in oxy-fuel combustion 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.
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.

Place, publisher, year, edition, pages
2013. Vol. 112, no SI, 747-754 p.
Keyword [en]
Oxy-coal combustion, Air separation unit (ASU), Peak and off-peak operations, CO2 capture, Economic assessment
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-116567DOI: 10.1016/j.apenergy.2012.12.001ISI: 000329377800080Scopus ID: 2-s2.0-84884211048OAI: oai:DiVA.org:kth-116567DiVA: diva2:590193
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
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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