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- Fredriksson Möller, Björn
(författare)
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A Thermoeconomic Evaluation of CO2 Capture with Focus on Gas Turbine-Based Power Plants
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing emissions of carbon dioxide from fossil fuel burning are today thought to be one of the main contributors to global warming. At the same time, developing countries are striving for an increased welfare and burning more fossil fuel, which in turn is augmenting the greenhouse gas effect. In this thesis the current understanding of the connection between greenhouse gases and the climate are illuminated, while some contradictory theories are also presented. Believing carbon dioxide to be a threat to the climate, which has been sufficiently evidenced to take actions against it, one possible option is to capture carbon dioxide in power plants and permanently store it underground. In this thesis different technologies for carbon dioxide capture are described. A thermodynamic model for post-combustion capture of carbon dioxide from flue gas is detailed, including thermodynamic models for a humidifier and exhaust gas condenser; components much needed in the proposed power plant layouts for power production with low or no emissions of carbon dioxide. Furthermore, an economic model suitable for modelling power plant schemes with low emissions of carbon dioxide in an economic environment with changing fuel prices and incentives for reduced emissions levels, are also presented. In a number of case studies, the thermodynamic and thermoeconomic performance of such proposed power plant layouts are compared, often with a standard combined cycle used as a reference base. In some case studies the performance, thermodynamic or thermoeconomic, have been optimised with an optimisation tool based on genetic algorithms, a method also thoroughly explained in this thesis. Case studies include among others; combined cycle gas turbines and humid air turbines with and without CO2 capture, pre-combustion combined cycle gas turbines and AZEP combined cycles. An overview of different methods for transport and storage of CO2, together with cost estimates and storage potential are also detailed in this thesis. A conclusion is made with the positive message that there seems to be a viable business case for carbon capture and storage with current high prices both on oil and certified emissions rights.
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- Fredriksson Möller, Björn, et al.
(författare)
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Azep gas turbine combined cycle power plants thermo-economic analysis
- 2005
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Ingår i: Proceedings of Ecos 2005, Vols 1-3 - Shaping our future energy systems. ; , s. 819-826
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Konferensbidrag (refereegranskat)abstract
- Conventional power plants based on fossil fuel without CO2 capture produce flue gas streams with concentrations Of CO2 between 3% and 15%, contributing to the threat of increasing global warming. Existing capture technologies such as post-combustion flue gas treatment using chemical absorption or pre-combustion carbon removal suffer from significant efficiency penalties as well as major increase in investment costs. Alternatively, combustion in O-2/CO2 atmospheres also requires expensive and energy-consuming oxygen supplies. A less energy intensive concept for oxygen production is a Mixed Conducting Membrane (MCM) reactor which produces pure oxygen from compressed air. The MCM reactor is best integrated into a conventional gas turbine combined cycle, called Advanced Zero Emissions Plant (AZEP), to provide an efficient and cost-effective power plant altogether. In this paper the economic performance of four different combined cycle alternatives in two different gas turbine sizes are evaluated; a 50 MWe size based on the Siemens SGT800 gas turbine and a 400 MWe size based on the Siemens SGT5-4000F gas turbine. ne evaluated combined cycles are one conventional combined cycle, one combined cycle with post-combustion CO2 capture and two optimised AZEP cases from a previous thermodynamic study. One AZEP alternative provides 100% CO2 capture and is thus a true zero emissions alternative, whereas the second alternative uses a sequential combustion system which enables 85% of the CO2 to be captured, making a comparison with traditional post-combustion treatment easier. The results show that the AZEP concept presents a more competitive system in terms of efficiency and economy compared to traditional capture systems.
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- Fredriksson Möller, Björn, et al.
(författare)
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CO2-free power generation - A study of three conceptually different plant layouts
- 2003
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Ingår i: American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI. ; 3, s. 255-262
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Konferensbidrag (refereegranskat)abstract
- Ever since the release of the Kyoto protocol the demand for CO2-free processes have been increasing. In this paper three different concepts with no or a very small release of CO2 to the atmosphere are evaluated and compared concerning plant efficiency and investment cost. A novel approach to biomass gasification is proposed to provide fuel for a combined gas turbine cycle, where the biomass is considered to be a renewable fuel with zero impact regarding CO2 in the exhaust gases. The gasification concept used is a Dual Pressurised Fluidised Bed Gasifier (DPFBG) system, using steam and recycled product gas as fluidising agent in the gasification reactor. In the separate combustion reactor air is used as fluidising agent. The second cycle is a hybrid fuelled Humid Air Turbine (HAT) cycle with post-combustion CO 2-separation. Steam used for regenerating the amines in the separation plant is produced using a biomass boiler, and natural gas is used as fuel for the humid air turbine. With this fuel mix the net release of CO 2 can even be less than zero if the exhaust gas from the steam generator is mixed and cleaned together with the main exhaust gas flow. The third cycle proposed is a combined cycle with postcombustion CO 2-separation and the steam generation for the CO 2-separation integrated in the bottoming steam cycle. All power cycles have been modelled in IPSEpro [trademark] (tm), a heat and mass balance software, using advanced component models developed by the authors. An equilibrium model is employed both for the gasification and the separation of CO2 from exhaust gases. All three power cycles show efficiencies around 45%, which is high for a biomass gasification cycle. The HAT and the combined cycle show efficiency drops of about 8 percentage points, due to the post-combustion treatment of exhaust gases.
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- Fredriksson Möller, Björn, et al.
(författare)
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CO2-free power generation in combined cycles - Integration of post-combustion separation of carbon dioxide in the steam cycle
- 2006
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 31:10-11, s. 1520-1532
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Tidskriftsartikel (refereegranskat)abstract
- Ever since the release of the Kyoto protocol the demand for CO2-free processes have been increasing. One of the most expanding sources of electric power in the industrialised world today is the gas-fired combined cycle, combining high efficiency and low investment cost. In this paper, the integration of a post-combustion CO2-separation unit into a combined cycle is studied from a thermodynamic and economic point-of-view. A standard dual-pressure combined cycle is chosen as a reference cycle. It is compared to a dual-pressure combined cycle and a triple-pressure combined cycle with the lowest pressure level producing steam for a CO2-separation unit. The steam pressure levels in the different cycles are optimised for maximum efficiency and minimum specific cost, respectively, using genetic algorithms. The efficiency drop due to CO2-separation is approximately 8% points, from 54 to 46%. The specific cost of the power plant is expected to increase with almost 100% and the cost of electricity with approximately 30%. In several countries a carbon dioxide tax is already introduced as an incentive for more efficient power cycles and use of fuels with lower content of coal. The result above implies that the level of such a tax would be in the order of 30% of the price of electricity to encourage CO2-free power generation.
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- Fredriksson Möller, Björn, et al.
(författare)
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On the off-design of a natural gas-fired combined cycle with CO2 capture
- 2007
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 32:4, s. 353-359
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Tidskriftsartikel (refereegranskat)abstract
- During the last 15 years cycles with CO, capture have been in focus, due to the growing concern over our climate. Often, a natural gas fired combined cycle with a chemical absorption plant for CO, capture from the flue gases have been used as a reference in comparisons between cycles. Neither the integration of the steam production for regeneration of amines in the combined cycle nor the off-design behaviour of such a plant has been extensively Studied before. In this paper, the integration of steam production for regeneration of the amines is modelled at design load and studied in off-design conditions for a combined cycle. Different ambient conditions and part-load strategies and their influence on the cycle performance are also examined. Of particular interest is a novel strategy with the possibility of longer life of gas turbine blading, with marginal loss in efficiency. The off-design performance of the combined cycle is modelled in a rigorous Way using a gas turbine performance deck, while the boiler is calculated using simplified correlations for oft-design heat transfer and pressure drop. The steam turbine calculation is based on verified models for the flow-pressure-efficiency relations, whilst the steam condenser is based oil the HEI method.
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| 8. |
- Fredriksson Möller, Björn, et al.
(författare)
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On the off-design of a natural gas-fired combined cycle with CO2 capture
- 2005
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Ingår i: Proceedings of Ecos 2005, Vols 1-3 - Shaping our future energy systems. - 8251920418 ; , s. 811-818
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Konferensbidrag (refereegranskat)abstract
- During the last 15 years cycles with CO2 capture have been in focus, due to the growing concern over our climate. Often a natural-gas fired combined cycle with a chemical absorption plant for CO2 capture from the flue gases have been used as a reference in comparisons between cycles. The integration of the steam production in the cycle to minimise the drop in efficiency have not been extensively studied. Neither have there been any studies on the off-design behaviour of such a plant if it should be built. In this paper the integration of steam production for regeneration of the amines is modelled at design load and studied in off-design conditions for a combined cycle. Different ambient conditions and part-load strategies and their influence on the cycle performance are also examined. Of particular interest is a novel strategy with the possibility of longer life of gas turbine blading, with marginal loss in efficiency. The off-design performance of the combined cycle is modelled in a rigorous way, using a gas turbine performance deck to calculate the performance of the gas turbine. The boiler is calculated using simplified correlations for off-design heat transfer and pressure drop. The steam turbine calculation is based on verified models for the flow - pressure - efficiency relations, whilst the steam condenser is based on the HEI (Heat Exchange Institute) method.
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| 9. |
- Fredriksson Möller, Björn, et al.
(författare)
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Optimisation of an SOFC/GT system with CO2-capture
- 2004
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Ingår i: Selected papers presented at the Eighth Grove Fuel Cell Symposium (Journal of Power Sources). - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 131:1-2, s. 320-326
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Konferensbidrag (refereegranskat)abstract
- Hybrid systems combining solid oxide fuel cells and gas turbines (SOFC/GT) have been extensively studied in recent years. They show very high theoretical electrical efficiencies and are considered as prime contenders for distributed generation. The addition of a CO2-capture system could make them even more attractive from an environmental perspective. In this study, a SOFC/GT configuration with and without a tail-end CO2 separation plant has been examined. In this work, the key parameters of the hybrid system are selected by an innovative tool based on a genetic algorithm (GA), which replaces the cumbersome parameter studies that generally are performed for this purpose. The focus is put on the evaluation of the GA as a tool for handling the multi-variable non-linear optimisation problem. The result of the optimisation procedure is a SOFC/GT system that exhibits an electrical efficiency above 60% with part capture of the CO2. (C) 2004 Elsevier B.V. All rights reserved.
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- Fredriksson Möller, Björn, et al.
(författare)
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Optimisation of hat-cycles - With and without CO2 capture
- 2004
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Ingår i: Proceedings of the ASME Turbo Expo 2004. ; 7, s. 461-468
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Konferensbidrag (refereegranskat)abstract
- In a world where distributed power generation and deregulation of energy markets are on everyone's agenda, the need for highly efficient power plants with short lead times is greater than ever. Although at present combined cycles provide a solution, development of ever more advanced machines to increase efficiency and lower the environmental impact has led to high maintenance costs and a decrease in availability. The Humid Air Turbine (HAT) represents a different approach, suitable for distributed power generation in the medium power range. The HAT cycle, and other wet gas turbine cycles, which have been extensively studied during the last ten years, show as high an efficiency as that of combined cycles, but at a lower specific cost and, with inherently low emissions of NOX. Despite all research done no full-scale plant has been built as yet. CO2 capture is another concept widely studied in recent years. In the present study three HAT cycle configurations are investigated, two of them connected to a post-combustion CO2-capture plant. Thermodynamic and thermoeconomic optimisation of the plants was performed using genetic algorithms (GA), a robust optimisation technique based on Darwinian evolution theories. The three configurations studied were 1) a standard inter-cooled HAT cycle, referred to as the reference cycle. 2) the reference cycle together with an integrated CO2-capture plant taking the energy needed for the CO2 separation from the exhaust heat of the turbine, and 3) the reference cycle together with a CO2 capture plant, in which the energy is supplied by a separate bio-fuelled boiler. This third configuration enables all fossil-based CO2 to be separated. All power cycles were modelled using IPSEpro, a heat-and mass-balance software, employing advanced component models developed by the authors. It has an interface for optimisation and the possibility of employing user-defined objective functions. The impact of CO2 taxation was studied to determine showing which configuration is the most economical at the current fuel-price and tax-level.
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