| 1. |
- Elger, Ragna, et al.
(författare)
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Corrosion and deposit formation on four steels exposed in the syngas section after a biomass gasifier
- 2016
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Ingår i: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley-VCH Verlag. - 0947-5117 .- 1521-4176. ; 67:9, s. 939-951
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Tidskriftsartikel (refereegranskat)abstract
- In this work, three different stainless steels (304L (CrNi-18-8), 253 MA®(CrNiSi-21-11), Kanthal® A-1 (FeCrAl)) and a reference low-alloyed ferritic steel (16Mo3 (Fe0.3Mo)) were exposed in a commercial biomass gasifier for three periods of 9 min, 580 and 1054 h in the temperature range 350–500 °C. Biomass is a fuel with generally higher amounts of chlorine and lower amounts of sulphur compared to coal and there is a current lack of data on materials performance in such environments. A high level of zinc sulphide was observed on the surfaces of all materials after exposure. It is argued that zinc plays a key role in capturing sulphur in this environment, thus preventing iron from sulphidation. Some incorporation of sulphur in the oxide scale was observed for Fe0.3Mo and CrNi-18-8. CrNiSi-21-11 showed some internal oxidation and pitting was observed for the FeCrAl material. All four materials showed acceptable performance with low total metal loss.
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| 2. |
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| 3. |
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| 4. |
- Elger, Ragna
(författare)
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High temperature corrosion in biomass-fired energy applications : Alloying effects and test environment comparisons
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To reduce the greenhouse effect, the use of renewable fuel has to be increased. As renewable fuel has different characteristics compared to fossil fuel regarding content of trace metals, alkali, chlorine and sulphur, the corrosion characteristics in high temperature energy processes have to be evaluated. This thesis concerns high temperature corrosion in the superheater region of a boiler and the syngas cooler area of a gasifier.For the superheater region, laboratory exposures were performed. The methods included a salt dip exposure, where samples were dipped in an equimolar solution of ZnCl2 and KCl, and two salt bed exposures with different chlorine concentrations, 10 and 20 wt%. Ranking of the materials showed that a Ni content above 10 wt% and Cr above 20 wt% reduced corrosion rates in the salt dip and in the 10% Cl salt bed exposure. For exposure in the 20% Cl bed, even higher alloying was needed. An alumina forming austenitic steel showed future potential in sulphidising-chlorinating environments.For the gasifier region, the effect of HCl in a simulated gasifier atmosphere was studied and also samples exposed in the syngas section of a biomass gasifier were investigated. Metal loss was low for all exposures and it was observed that chlorine had minor influence. For the plant exposed samples, a difference compared to that reported for coal gasifiers was the absence of FeS for the lowest alloyed steel. Instead, a deposit with pronounced content of Zn, Ca, S and O was present on the surface. Zinc was suggested to mitigate corrosion.Thermodynamic modelling was used to explain phases present and to predict the nitridation behaviour of an alumina forming austenitic steel. Equilibrium and kinetic modelling of the nitridation showed good coherence with the observed microstructures. However, the kinetic modelling resulted in larger nitridation depths than observed experimentally which was attributed to the presence of a thin oxide layer on the surface of the samples.
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| 5. |
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| 6. |
- Elger, Ragna, et al.
(författare)
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Laboratory testing to evaluate candidate alloys for superheaters in waste-fired boilers
- 2016
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Ingår i: Materials at High Temperature. - : Taylor and Francis Ltd.. - 0960-3409 .- 1878-6413. ; 33:6, s. 587-595
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Tidskriftsartikel (refereegranskat)abstract
- Two types of laboratory tests were used to evaluate the behaviour of a wide range of steels in chlorinating–sulphidising conditions: high temperature exposure after applying salt by dipping in an aqueous KCl/ZnCl2 solution and salt-bed test in a ZnCl2/NaCl/KCl/CaSO4 salt mixture. The exposures were performed at 500 °C in a gas comprising N2/HCl/SO2/O2/N2. For the alloy group with 20–30 wt-% chromium and 25–65 wt-% nickel, the extrapolated metal loss was below 0.2 mm/year in the salt dip, up to 6 mm/year in the salt-bed test with 10% Cl and up to 20 mm/year in the 20% Cl salt-bed test. The intermediate alloy group showed poorer performance in the salt-bed; Esshete1250 showed also large spallation in the salt dip test. Results were compared with plant-exposed samples. Further refinement of the salt dip test is suggested for material ranking in the superheater region of a waste or biomass-fired incinerator. © 2016 Swerea Kimab.
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| 7. |
- Elger, Ragna, et al.
(författare)
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Modelling and experimental validation of the electrochemical behaviour of a li-ion battery during repetitive pulses of charge and discharge
- 2004
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Konferensbidrag (refereegranskat)abstract
- In this study, a mathematical model describing the electrochemical and thermal behaviour of a cylindrical lithium-ion battery during high rate discharge and charge using a pulse typical for hybrid electric vehicles (HEV) is validated against experimental data. Experiments on the battery were performed in various constant temperature environments during a repeated pulse using high rate charge and discharge. The results show that the voltage losses increase as the temperature is lowered. The measurements show that as a good approximation, the surface temperature during the pulses can be assumed constant. The open circuit potential of LiNi0.8Co0.15Al0.05 was measured using GITT-experiments. The temperature dependence of the open circuit potential of LiNi0.8Co0.15Al0.05 was shown to be negligible. The experimental data will be used to validate the battery model. Some of the model parameters have yet to be fitted to the experimental results before a good agreement between experimental and model results is obtained.
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| 8. |
- Elger, Ragna, et al.
(författare)
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Modelling internal nitridation in an alumina-forming austenitic stainless steel
- 2017
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Ingår i: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 68:2, s. 143-150
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Tidskriftsartikel (refereegranskat)abstract
- An austenitic alumina forming stainless steel was exposed in a nitriding atmosphere comprising 5 vol% H2/N2 for 100 and 1000 h. After 100 h, the sample displayed aluminium nitrides down to 450 μm and chromium nitrides down to 200 μm. Thermodynamic equilibrium calculations and kinetic modelling of the system to simulate 100 h of exposure time were performed using the software ThermoCalc 4.1 including DICTRA. The order of appearance of nitrides in the sample starting from the surface can be understood from the thermodynamic equilibria as well as from results of kinetic modelling. However, the nitridation depth predicted by the kinetic modelling, was larger than experimentally observed, and the cubic chromium nitride predicted to be present on the surface was not detected in the exposed sample. One difference between model and experiment was a thin oxide layer present on the surface of the sample. As this oxide layer can decrease the inwards flux of nitrogen, attempts were made to describe the effects of this layer in the model. The model was also used for qualitative comparison of varying alloy compositions, temperatures and initial nitrogen contents of the matrix.
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| 9. |
- Elger, Ragna
(författare)
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On the behaviour of the lithium ion battery in the HEV application
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The lithium ion battery is today mainly used in cell phonesand laptops. In the future, this kind of battery might beuseful in hybrid electric vehicles as well. In this work, the main focus has been to gain more knowledgeabout the lithium ion battery in the hybrid electric vehicle(HEV) and more precisely to examine what processes of thebattery that are limiting at HEV currents. Both experiments andmathematical modelling have been used. In both cases, highrate, pulsed currents typical for the HEV, have been used. Two manuscripts have been written. Both of them concern thebehaviour of the battery at HEV load, but from different pointsof view. The first one concerns the electrochemical behaviourof the battery at different ambient temperatures. Theexperimental results of this paper were used to validate amathematical model of a Li-ion battery. Possiblesimplifications of the model were identified. In this work itwas also concluded that the mass transfer of the electrolyte isthe main limiting process within the battery. The mass transferof the electrolyte was further studied in the second paper,where the concentration of lithium ions was measured indirectlyusing in situ Raman spectroscopy. This study showed that themathematical description of the mass transfer of theelectrolyte is not complete. One main reason of this issuggested to be the poor description of the physical parametersof the electrolyte. These ought to be further studied in orderto get a better fit between concentration gradients predictedby experiments and model respectively.
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| 10. |
- Nyman, Andreas, et al.
(författare)
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A New Methodology for Evaluating the High-Power Behavior of a Li-ion Battery Cell
- 2010
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Ingår i: Rechargeable Lithium-Ion Batteries. - : Electrochemical Society. - 9781566778107 ; , s. 253-262
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Konferensbidrag (refereegranskat)abstract
- The internal sources of polarization are calculated and investigated for a graphite (MAG-10) vertical bar 1.2 M LiPF6 in EC: EMC (3: 7 by weight) vertical bar LiNi0.8Co0.15Al0.05O2 battery cell at SOC 40 and 80. A method is developed where the total polarization of the battery cell is split up into six polarizing subprocesses. The method involves two steps; the solving of an experimentally validated model that describes the dynamics of the battery cell during e. g. a hybrid pulse power characterization test and the use of the modeled cell's local potential, concentration profiles and local current density to calculate the internal losses. With this analysis the sources of polarization during an EUCAR test cycle are determined. The major factor limiting the performance is associated with the mass transport in the electrolyte.
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