| 1. |
- Boman, Christoffer, et al.
(författare)
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Development of innovative small(micro)-scale biomass-based CHP technologies
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To enhance the overall efficiency of the use of biomass in the energy sector in Europe, the large electricity production potential from small-scale biomass heating systems should be utilised. So far, no technologically sound (in terms of efficiency and reliability) and economically affordable micro- and small-scale biomass CHP technologies are, however, available. Therefore, the present ERA-NET project (MiniBioCHP) aimed at the further development and test of new CHP technologies based on small-scale biomass combustion in the electric capacity range between some W and 100 kW. Within the project, an international consortium consisting of 12 partners from 4 countries, including university institutions, institutes and industry (both engineering and manufacturing), collaborated closely to perform high level R&D on three promising micro/small-scale biomass based CHP technologies which are covering a broad range of applications in the residential heating sector. The Austrian engineering company BIOS, coordinated the international project. The project was based on earlier basic research and development work related to these promising new technologies and aimed at the achievement of a technological level which allows a first (commercial) demonstration after the end of the project. The three CHP concepts included in the MiniBioCHP project were;1. Pellet stoves with a thermoelectric generator (TEG)2. Small-scale biomass boilers (10-30 kWth) with a micro-ORC process3. High temperature heat exchanger (HT-HE) for an externally fired gas turbine (EFGT)The Swedish part of the project was focused on the development of the concept of biomass based EFGT with dedicated R&D activities related to the development of the HT-HE system. The Swedish project consisted of the research partners Umeå University (project leader), Luleå University of Technology, Chalmers University of Technology and RISE Research Institutes of Sweden, together with the industrial partners Enertech AB/Osby Parca and Ecergy. The expertise of the Swedish partners regarding ash related problems, grate boiler combustion and modelling, deposit formation and high temperature corrosion, were combined with the know-how of a Polish partner regarding HT-HE design, construction, testing and optimisation.The HT-HE is the most crucial component in EFGT processes significantly influencing the investment costs, availabilities as well as the efficiencies that can be achieved. With a thermal capacity from several hundred kW up to 2-3 MWth) the CHP technology based on a biomass boiler and an EFGT is suitable for district heating systems, or process heat consumers. The electricity produced by the gas turbine (up to some 100 kWel) can be used to cover the own electricity consumption of a company and/or fed into the grid. Even though the concept of biomass based EFGT has been an interesting alternative for small-scale CHP production for some decades, and R&D activities have been undertaken, tackling both economic and technical aspects, only a few pilot-plants have been in operation and no initiative has so far reached the level of commercial implementation. Thus, the concept of EFGT fed with biomass is still considered to be in a rather early development stage and the main technical challenges are related to alkali deposit induced corrosion and thermal stress of the HT-HE material, turbine design/operation and system integration.Within the present project, a HT-HE prototype aimed for an EFGT system was therefore designed, constructed and successfully tested at flue gas temperatures up to 900°C. Thus, appropriate guidelines for a compact design of the HT-HE and recommendations have been worked out to minimize thermal stresses as well as ash related problems regarding ash deposit formation and high temperature corrosion in a biomass boiler system. Furthermore, different concepts for the overall biomass based EFGT system have been worked out and evaluated. The outcome of the project will hopefully be used in the further development work and form the basis for a first testing and demonstration plant within the coming years.
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| 2. |
- Hjörnhede, Anders, 1968, et al.
(författare)
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Erosion-corrosion of laser and thermally deposited coatings exposed in fluidised bed combustion plants
- 2006
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Ingår i: Materials and Corrosion. ; 57:4, s. 307-322
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Tidskriftsartikel (refereegranskat)abstract
- Coated steel tubes were exposed in two power plants (CFB and PFBC) fired with wood chips and coal with a small addition of olive seeds, respectively. Laser coating and two thermal spray techniques were used. The samples in the PFBC plant were immersed in the fluidising bed at material temperatures 450 °C and 400 °C. The exposure lasted for a total time of 8089 h. In the CFB plant a probe at the cyclone entrance had a material temperature of 630 °C for the first 2100 h and then 480 °C for 920 h. The material wastage was determined from tube cross-sections. The corrosion products and deposits were analysed by SEM/EDX, Auger spectroscopy, XPS and XRD. Cobalt based coatings show the best performance in both plants, while nickel based coatings are very sensitive to erosion but resistant to a corrosive atmosphere. The totally degraded chromium carbide containing coating in the CFB plant shows that the degree of corrosion is much larger in this environment. The same coating was excellent in the fluidised bed due to its high erosion resistance. The material wastage is independent of the deposition method. The coating technicques had no significant effect on the spallation behaviour.
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| 3. |
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| 4. |
- Ström, Henrik, 1981, et al.
(författare)
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Experimental and Numerical Investigations of Ash Behaviour in Fixed-Bed Combustion of Woody Biomass Pellets
- 2017
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Ingår i: Proceedings of the Nordic Flame Days 2017, Stockholm, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Combustion of woody biomass in a fixed-bed configuration could play an important role in the development of small-scale combined-heat-and-power solutions, such as externally-fired micro-gas turbines. However, many challenges still remain with regard to the complexity of maintaining high availability with an acceptable fuel flexibility, as ash transformations in the fuel bed can cause serious problems for the robustness of the process as well as for downstream components. In this work, fixed-bed combustion of two woody biomasses of different ash contents is studied experimentally and numerically in an attempt to advance the understanding of ash-related disturbances. A mathematical model for fixed-bed conversion of biomass is extended to account for ash transformations on both the single-pellet level and the bed level, and the predictions from this model are assessed against the experimental results. The agreement between simulations and experiments is good for low air-flow rates, whereas additional considerations are needed for air-flow rates closer to the stoichiometric limit. Although there was no catastrophic slagging observed in the experiments, the capabilities of the model to describe effects of such slagging, down to only slightly reduced combustion rates due to milder ash transformations, are confirmed by the simulations.
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| 5. |
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| 6. |
- Hjörnhede, Anders, 1968
(författare)
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Erosion - Corrosion Resistance and Adhesion of Laser and Thermally Deposited Coatings in Fluidised Beds
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High temperature erosion - corrosion is the major source for degradation of components such as heat exchangers, tubes, cyclones and water walls used in Fluidised Bed Combustion (FBC) plants. By coating the exposed components with a protective material, the degradation rate can be decreased. The aim of this work was to determine the erosion - corrosion resistance of coatings deposited with the arc-spray, High Velocity Oxy Fuel (HVOF) and laser techniques. The erosion - corrosion tests have been performed in three different power plants; one Circulating Fluidised Bed (CFB) plant fired with biomass, one Multi Bed Combustion (MBC) plant fired with a mixture of coal and biomass and one Pressurised Fluidised Bed Combustion (PFBC) plant fired with coal. The erosion - corrosion resistance of coatings has also been examined in one laboratory jet nozzle test rig and one fluidised bed test rig. Further, the adhesion strength of coatings deposited on substrates of a low-alloyed steel (1Cr0.5Mo) has been tested. A number of commercially available coating qualities have been used in this study. The reference material is the Fe-based Metcoloy 2 coating, which was deposited with all the three methods available. The other coatings can be divided into Ni-based, Co-based, carbide - containing and Fe-based. Under active - service conditions Co-based coatings show the best overall performance. It is suggested that the erosion resistance is partly due to the presence of carbide rich phases dispersed in the coating. The softer Ni based coatings are generally more subjected to erosion. The corrosion resistance of Fe-based coatings is poor at higher temperatures in more corrosive environments. Chromium carbide - containing coatings are excellent in the coal fired erosive environment but degrade severely in the biomass fired plants showing that stable hard phases, such as carbide, at the exposure temperature decrease the degradation rate. Tungsten and Ti-carbide containing coatings suffer from severe degradation in all environments. The coated samples were subjected to erosion- corrosion in a jet nozzle rig in air at 520ºC or 550ºC. Compared to a solid 304L steel (Fe19Cr10Ni), the erosion - corrosion resistance of the coatings tested (Fe-based, Ni-based and carbide - containing) is higher. The oxides formed on the eroded area of the Metcoloy 2 coating are 10 - 60 times thicker than those formed on the non - eroded area. Consequently, erosion has increased the oxide growth rate. The increased oxide thickness on the eroded areas is due to the formation of cracks and pores in the oxide scale. These will enhance the inward transport of molecular oxygen through the oxide layer to the oxide/metal interface where the metal phase is oxidised. Erosion - corrosion tests performed in the fluidised bed test rig at 550°C in air shows that the erosion resistance of thermally sprayed coatings is higher in comparison to laser deposited coatings. The use of acoustic emission for determining the adhesion strength of the coatings proved to be successful and more reliable than the traditional four point bending test with a subsequent metallographic examination. HVOF sprayed coatings start to delaminate at a strain of about 1%, arc sprayed at a strain of about 1.4 2% while laser deposited coatings did not delaminate for strains up to 15%. However, by increasing the splat size in the arc sprayed coatings the strain at which delamination occurred was increased to a bout 10%.
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| 7. |
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| 8. |
- Ström, Henrik, 1981, et al.
(författare)
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Experimental and Numerical Investigations of Ash Behaviour in Fixed-Bed Combustion of Woody Biomass Pellets
- 2018
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Ingår i: Industrial Combustion Journal. - 2075-3071.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Combustion of woody biomass in a fixed-bed configuration could play an important role in the development of small-scale combined-heat-and-power solutions, such as externally-fired micro-gas turbines. However, many challenges still remain with regard to the complexity of maintaining high availability with an acceptable fuel flexibility, as ash transformations in the fuel bed can cause serious problems for the robustness of the process as well as for downstream components. In this work, fixed-bed combustion of two woody biomasses of different ash contents is studied experimentally and numerically in an attempt to advance the understanding of ash-related disturbances. A mathematical model for fixed-bed conversion of biomass is extended to account for ash transformations on both the single-pellet level and the bed level, and the predictions from this model are assessed against the experimental results. The agreement between simulations and experiments is good for low air-flow rates, whereas additional considerations are needed for air-flow rates closer to the stoichiometric limit. Although there was no catastrophic slagging observed in the experiments, the capabilities of the model to describe effects of such slagging, down to only slightly reduced combustion rates due to milder ash transformations, are confirmed by the simulations.
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