| 1. |
- Pihl, Erik, 1981, et al.
(författare)
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Biomass Retrofitting a Natural Gas-Fired Plant to a Hybrid Combined Cycle (HCC)
- 2009
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Ingår i: 22nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2009; Foz du Iguacu, Parana; Brazil; 30 August 2009 through 3 September 2009. ; , s. 2163-2176
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Konferensbidrag (refereegranskat)abstract
- This work investigates retrofit of a natural gas fired plant for co-firing with biomass. The retrofit is by integration of a solid biomass combustor with the bottoming cycle of a combined cycle gas turbine (CCGT) plant, to form a Hybrid Combined Cycle (HCC). The motivation is the need to find efficient options for substitution of natural gas by biomass to meet the imminent need to reduce C02 emissions as well as improve security of supply in the utility power sector, which in some regions is heavily dependent on power generation from rather new CCGT plants. The work is based on process simulations using an existing 600 MWfuel combined heat and power CCGT plant (commissioned 2006) as reference. It is shown that the HCC retrofit only yields a minor decrease in plant efficiency; electric efficiency (ηe) of 43.3%, compared to 44.4% for natural gas-only in the reference plant (full load and full substitution of supplementary firing corresponding to 39% of natural gas). A HCC with higher biomass-firing capacity and an additional high-pressure condensing turbine can increase the substitution of natural gas to 59% yielding ηe = 40.8% and total efficiency (electricity and heat) of 87.1%, i.e. a larger decrease in efficiency than for 39% substitution. A HCC plant gives in all configurations higher electric efficiency than a corresponding combination of single-fuel stand-alone plants, CCGT for naturalgas and steam CHP plants for biomass, with the same share of biomass in thefuel mix. A simulation representing one year's operation of hybrid and reference options, including part load cases, show that overall efficiencies can be kept at roughly the same levels as infull load. It is recognized that layout of existing plant, projected level of natural gas substitution and local conditions in fuel supply and energy demand are necessary to consider when assessing the most suitable option for C02 abatement by biomass in a gas power plant.
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| 2. |
- Heyne, Stefan, 1979, et al.
(författare)
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Exergy-based comparison of indirect and direct biomass gasification technologies within the framework of bio-SNG production
- 2013
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 3:4, s. 337-352
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric indirect steam-blown and pressurised direct oxygen-blown gasification are the two major technologies discussed for large-scale production of synthetic natural gas from biomass (bio-SNG) by thermochemical conversion. Published system studies of bio-SNG production concepts draw different conclusions about which gasification technology performs best. In this paper, an exergy-based comparison of the two gasification technologies is performed using a simplified gasification reactor model. This approach aims at comparing the two technologies on a common basis without possible bias due to model regression on specific reactor data. The system boundaries include the gasification and gas cleaning step to generate a product gas ready for subsequent synthesis. The major parameter investigated is the delivery pressure of the product gas. Other model parameters include the air-to-fuel ratio for gasification as well as the H2/CO ratio in the product gas. In order to illustrate the thermodynamic limits and sources of efficiency loss, an ideal modelling approach is contrasted with a model accounting for losses in, e.g. the heat recovery and compression operations. The resulting cold-gas efficiencies of the processes are in the range of 0.66–0.84 on a lower heating value basis. Exergy efficiencies for the ideal systems are from 0.79 to 0.84 and in the range of 0.7 to 0.79 for the systems including losses. Pressurised direct gasification benefits from higher delivery pressure of the finished gas product and results in the highest exergy efficiency values. Regarding bio-SNG synthesis however, a higher energetic and exergetic penalty for CO2 removal results in direct gasification exergy efficiency values that are below values for indirect gasification. No significant difference in performance between the technologies can be observed based on the model results, but a challenge identified for process design is efficient heat recovery and cogeneration of electricity for both technologies. Furthermore, direct gasification performance is penalised by incomplete carbon conversion in contrast to performance of indirect gasification concepts.
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| 3. |
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| 4. |
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| 5. |
- Alamia, Alberto, 1984, et al.
(författare)
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Fuel Quality Analysis for Biogas Utilization in Heavy Duty Dual Fuel Engines
- 2012
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Ingår i: World BioEnergy 2012 - conference in Jönköping , May 2012. ; , s. 1-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The perspective of using gas form biomass gasification as fuel for dual fuel (DF) engines, without refine it all the way to synthetic natural gas (SNG) has been investigated. The initial gas from gasification contains of a blend of various components which are not commonly present in natural gas (NG). The operability of these components in a heavy duty DF engine has been assessed and compared to those of NG. Three parameters have been used to define the quality of the fuel: Lower Heating Value (LHV), Methane Number (MN) and Lower Flammability Limit (LFL).
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| 6. |
- Alamia, Alberto, 1984, et al.
(författare)
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Fuel Quality Analysis for Biogas Utilization in Heavy Duty Dual Fuel Engines
- 2012
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Ingår i: 20th European Biomass conference & exhibition - Milan -June 2012. - 9788889407547 ; , s. 5-
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Konferensbidrag (refereegranskat)abstract
- Internal combustion engines using oil-derived fuels are dominating the heavy transportation sector today. However, the climate issue and security of supply drive the development towards new fuels and engine technologies. In the short term, Natural Gas (NG) is expected to have a dominant role, due to its high availability and a favourable H/C ratio. Thereafter, it is expect an introduction of biofuels of second and third generations. In this scenario the engine suppliers need to develop engines for various fuels of both fossil and renewable origin. One possibility is the Dual Fuel engine (DF), which uses a Diesel pilot to ignite a gas mixture and, it can be used for natural gas of various qualities as well as synthetic natural gas (SNG). To obtain significant share of second and third generation biofuels into the transportation sector a key process is gasification of the raw solid biomass to gas, as it can offer high production capacity and high efficiency. One interesting biofuel is SNG and at present there are a number of projects focusing on SNG production through gasification of biomass to be fed to the NG grid. However, this is a rather advanced and several stage process. The initial gas from the gasification before the gas is upgraded to CH4 (SNG) contains of a blend of various gas components such as H2, CO, CO2, CH4 and fractions of C2H2, C2H4, C3H6, and C3H8, as well as, longer hydrocarbons. The upgrading takes place in many process steps, where each step involves a cost and loss of energy. The question raised is if there are more efficient routs to introduce biomass derived gas than refine it all the way to SNG, from a well to wheel (WTW) perspective? The first step in such an analysis is to investigate how different gas mixtures could meet emission limits, together with the required performance of efficiency and load. This issue has been addressed in this work, where the operability in DF engines using gaseous fuels with a variation in fuel quality has been investigated. The operability has a key role in the optimization of the WTW efficiency, since it influences both the production process and the combustion in the engine. The definition of fuel quality for gaseous fuels to be used in gas engines is still not in place and proper legislation and standards are not available. Here, three parameters which are fundamental for a proper combustion in a DF engine: the Methane Number (MN), the Lower Flammability Limit (LFL) and the Lower Heating Value (LHV) have been studied. All parameters influence the combustion performance in the DF engine of the Port-injected type, which is more sensitive to the fuel quality than the Direct-injected type. The components available from biomass gasification were evaluated together with those from different NG compositions on the European market. Specific relations between the composition and fuel quality parameters have been derived, which can be used as starting point for future well to wheel analysis.
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| 7. |
- Alamia, Alberto, 1984, et al.
(författare)
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Design of an integrated dryer and conveyor belt for woody biofuels
- 2015
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 77, s. 92-109
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Tidskriftsartikel (refereegranskat)abstract
- Combustion or gasification of high-moisture content biomass is associated with a number of drawbacks, such as operational instabilities and lowered total efficiency. The present work proposes an integrated dryer and conveyor belt for woody biofuels with steam as the heat transfer medium. The use of low-temperature steam is favorable from a heat management point of view, but also helps to minimize the risk of fire, self-ignition and dust explosions. Furthermore, the presented dryer design represents an efficient combination of fuel transport, drying equipment and fuel feeding system.The proposed design is developed from a macroscopic energy and mass balance model that uses results from computational fluid dynamics (CFD) fuel bed modeling and experiments as its input. This CFD simulation setup can be further used to optimize the design with respect to bed height, steam injection temperatures and fuel type. The macroscopic model can be used to investigate the integration of the dryer within a larger biomass plant. Such a case study is also presented, where the dryer is tailored for integration within an indirect steam gasification system. It is found that the exergy efficiency of this dryer is 52.9%, which is considerably higher than those of other dryers using air or steam, making the proposed drying technology a very competitive choice for operation with indirect steam gasification units.
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| 9. |
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| 10. |
- Jareteg, Adam, 1989, et al.
(författare)
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Detailed simulations of heterogeneous reactions in porous media using the Lattice Boltzmann Method
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Flows though porous media are commonly found in many systems, both natural and manmade. A few examples from nature include petroleum reservoirs, soil and solid biomass where industrial applications include fuel cells, foams and packed beds. Most of these areas are still subject to both scientific and engineering challenges ranging from basic understanding to detailed optimization. A non-trivial part of the remaining challenges includes the interaction between macro-scale performance and micro-scale characteristics. For some systems, it is possible to control and tune micro-scale properties to optimize the overall performance of the application. This scenario typically manifests in the design of packed beds, especially when reactions occur within the bed. In such situations, particle shape and size distribution will affect not only the pressure drop (and hence the preferential flow paths), but also local reaction rates and thereby efficiency and selectivity. This work aims to understand and identify key design parameters that influences reactions within a packed bed, and ultimately, the overall performance of the pack- ing. Representative microstructures of packed beds are generated with a Discrete Element Method. Flow, temperature and concentration fields (cf. Figure 1) are then fully resolved using the Lattice Boltzmann Method with a first order reaction scheme at the boundaries. Residence time, flow structures and permeability of the systems are correlated to conversion and selectivity of the chemical reactions in the system. Comparisons between packings of different particle shapes and spacing serve to eluci- date phenomena involved in the process and implies design directions for macro-scale optimization.
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