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The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2009 (English)In: International journal of greenhouse gas control, ISSN 1750-5836, Vol. 3, no 3, 255-262 p.Article in journal (Refereed) Published
Abstract [en]

This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.

Place, publisher, year, edition, pages
2009. Vol. 3, no 3, 255-262 p.
Keyword [en]
Carbon dioxide capture; Hybrid power cycles; PFBC
National Category
Chemical Process Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10978DOI: 10.1016/j.ijggc.2008.09.002ISI: 000266179200002Scopus ID: 2-s2.0-64449085290OAI: oai:DiVA.org:kth-10978DiVA: diva2:233600
Note
QC 20100727Available from: 2009-09-01 Created: 2009-09-01 Last updated: 2010-08-20Bibliographically approved
In thesis
1. Opportunities and uncertainties in the early stages of development of CO2 capture and storage
Open this publication in new window or tab >>Opportunities and uncertainties in the early stages of development of CO2 capture and storage
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The topic of this thesis is carbon dioxide (CO2) capture and storage (CCS), which is a technology that is currently being promoted by industries, scientists and governments, among others, in order to mitigate climate change despite a continued use of fossil fuels. Because of the complex nature of CCS and the risks it entails, it is controversial. The aim of this thesis is to analyse how the technology may be further developed in a responsible manner. In the first part of the thesis different methods for capturing CO2 from industrial processes as well as power plants are analysed. The aim is to identify early opportunities for CO2 capture, which is considered important because of the urgency of the climate change problem. Three potential early opportunities are studied: i) capturing CO2 from calcining processes such as cement industries by using the oxyfuel process, ii) capturing CO2 from pressurised flue gas, and iii) capturing CO2 from hybrid combined cycles. Each opportunity has properties that may make them competitive in comparison to the more common alternatives if CCS is realised. However, there are also drawbacks. For example, while capturing CO2 from pressurised flue gas enables the use of more compact capture plant designs as well as less expensive and less toxic absorbents, the concept is neither suitable for retrofitting nor has it been promoted by the large and influential corporations. The second part of the thesis has a broader scope than the first and is multidisciplinary in its nature with inspiration from the research field of Science and Technology Studies (STS). The approach is to critically analyse stakeholder percep-tions regarding CCS, with a specific focus on the CCS experts. The thesis sheds new light on the complexity and scientific uncertainty of CCS as well as on the optimism among many of its proponents. Because of the uncertain development when it comes to climate change, fossil fuel use and greenhouse gas emissions, the conclusion is that CCS has to be further developed and demonstrated. A responsible strategy for a future development of CCS would benefit from: i) a search for win-win strategies, ii) increasing use of appropriate analytical tools such as life-cycle analysis, iii) a consideration of fossil fuel scarcity and increasing price volatility, iv) funding of unbiased research and v) increasing simultaneous investments in long-term solutions such as renewable energy alternatives and efficiency improvements.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. viii, 68 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:50
Keyword
Acceptance, cement, CCS, CO2 capture and storage, early opportunities, enhanced oil recovery, expert opinions, hybrid power cycles, optimism, oxyfuel combustion, pressurised fluidised bed combustion, pilot plant, potassium carbonate, risk, Sargas, scenario studies, scientific uncertainty, stakeholder perceptions
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:kth:diva-10985 (URN)978-91-7415-413-9 (ISBN)
Public defence
2009-09-28, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100727Available from: 2009-09-08 Created: 2009-09-01 Last updated: 2010-07-27Bibliographically approved
2. A trinity of sense: Using biomass in the transport sector for climate change mitigation
Open this publication in new window or tab >>A trinity of sense: Using biomass in the transport sector for climate change mitigation
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis analyses two strategies for decreasing anthropogenic carbon dioxide (CO2) emissions: to capture and store CO2, and to increase the use of biomass. First, two concepts for CO2 capture with low capture penalties are evaluated. The concepts are an integrated gasification combined cycle where the oxygen is supplied by a membrane reactor, and a hybrid cycle where the CO2 is captured at elevated pressure. Although the cycles have comparatively high efficiencies and low penalties, they illustrate the inevitable fact that capturing CO2 will always induce significant efficiency penalties. Other strategies are also needed if CO2 emissions are to be forcefully decreased. An alternative is increased use of biomass, which partially could be used for production of motor fuels (biofuels). This work examines arguments for directing biomass to the transport sector, analyses how biofuels (and also some other means) may be used to reduce CO2 emissions and increase security of motor fuel supply. The thesis also explores the possibility of reducing CO2 emissions by comparatively easy and cost-efficient CO2 capture from concentrated CO2 streams available in some types of biofuel plants. Many conclusions of the thesis could be associated with either of three meanings of the word sense: First, there is reason in biofuel production – since it e.g. reduces oil dependence. From a climate change mitigation perspective, however, motor fuel production is often a CO2-inefficient use of biomass, but the thesis explores how biofuels’ climate change mitigation effects may be increased by introducing low-cost CO2 capture. Second, the Swedish promotion of biofuels appears to have been governed more by a feeling for attaining other goals than striving for curbing climate change. Third, it seems to have been the prevalent opinion among politicians that the advantages of biofuels – among them their climate change mitigation benefits – are far greater than the disadvantages and that they should be promoted. Another conclusion of the thesis is that biofuels alone are not enough to drastically decrease transport CO2 emissions; a variety of measures are needed such as fuels from renewable electricity and improvements of vehicle fuel economy.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 68 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:62
Keyword
Biofuel, biomass, carbon dioxide capture and storage, energy systems, ethanol, hybrid cycle, mixed conducting membrane reactor, pressurized fluidized bed combustion, Sweden, transport
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9292 (URN)978-91-7415-107-7 (ISBN)
Public defence
2008-11-07, F3, KTKH, Lindstedtsvägen 26, Stockholm, 13:30 (English)
Opponent
Supervisors
Note
QC 20100823Available from: 2008-10-22 Created: 2008-10-16 Last updated: 2010-08-23Bibliographically approved

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