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Öhman, Marcus
Publications (10 of 168) Show all publications
Wagner, K., Kuba, M., Häggström, G., Skoglund, N., Öhman, M. & Hofbauer, H. (2018). Influence of phosphorus on the layer formation on k-feldspar during fluidized bed combustion and gasification. Paper presented at 26th EU Biomass Conference & Exhibition, Copenhagen, 14-17 May 2018. European biomass conference and exhibition proceedings, 26thEUBCE, 486-492
Open this publication in new window or tab >>Influence of phosphorus on the layer formation on k-feldspar during fluidized bed combustion and gasification
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2018 (English)In: European biomass conference and exhibition proceedings, E-ISSN 2282-5819, Vol. 26thEUBCE, p. 486-492Article in journal (Refereed) Published
Abstract [en]

Today, mainly wood-based feedstocks are used in thermo-chemical biomass conversion since they have a comparably high heating value and contain a small amount of ash. Fluidized beds allow a greater variety of fuels to be used, since they are rather flexible regarding their fuel input. The use of biogenic waste streams (chicken manure, horse manure, etc.) and sewage sludge would not only increase the fuel diversity in fluidized beds but might also enhance the usability of side products. The contained essential nutrients like phosphorus, potassium, calcium, etc. in these fuels are enriched in the ash after thermochemical conversion. Thus, in the near future it may be possible to apply this ash as secondary resource for fertilizer. Especially the recovery of phosphorus is of importance due to the imminent phosphorus scarcity. Due to its tendency to react with ash forming elements in fuels, phosphorus influences the ash chemistry severely. Especially the agglomeration and layer formation on bed materials during biomass combustion and gasification is highly dependent on the predominant ash forming elements. Phosphorus therefore has a significant impact on those mechanisms. Until now, the behavior of phosphorus-rich fuels in fluidized beds has not been studied in much detail. To develop a basic understanding of the behavior, phosphorus-rich feedstock was combusted in a bench-scale fluidized bed reactor. Ash layers on bed particles, which were formed during these experiments, were studied and compared to results with phosphorus-lean fuels. Furthermore, layer formation of phosphorus-rich and phosphorus-lean fuels from dual fluid bed gasification were compared to those from fluidized bed combustion. The studied layers on bed materials showed significant amounts of phosphorus. The data also indicates a change in layer formation as soon as phosphorus is present. An increased catalytic activity due ash-layer formation was observed for both phosphorus-rich and phosphorus-lean feedstock, independent from the presence of phosphorus in the ash layer

Place, publisher, year, edition, pages
ETA-Florence Renewable Energies, 2018
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-70379 (URN)2-s2.0-85051038323 (Scopus ID)
Conference
26th EU Biomass Conference & Exhibition, Copenhagen, 14-17 May 2018
Available from: 2018-08-14 Created: 2018-08-14 Last updated: 2018-08-14Bibliographically approved
Sefidari, H., Lindholm, B., Wiinikka, H., Nordin, L. O., Mouzon, J., Bhuiyan, I. U. & Öhman, M. (2018). The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part I: Characterization of process gas particles and deposits. Fuel processing technology, 177, 283-298
Open this publication in new window or tab >>The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part I: Characterization of process gas particles and deposits
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2018 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 177, p. 283-298Article in journal (Refereed) Published
Abstract [en]

o initiate the elucidation of deposit formation during the iron-ore pelletization process, a comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal-fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale grate-kiln setup. Particles and deposits were sampled from 3 positions of different temperature via a water-cooled sampling probe. Three distinct fragmentation modes were identified based on the aerodynamic particle diameter (Dp). The fine mode: Particles with 0.03 < Dp < 0.06 μm. The first fragmentation mode: Particles with 1 < Dp < 10 μm. The second fragmentation mode: Coarse particles (cyclone particles, Dp > 10 μm). A transition from a bimodal PSD (particle size distribution) to a trimodal PSD was observed when pellet dust was added (Case 3) and consequently the elemental bulk composition of the abovementioned modes was changed. The most extensive interaction between pellet dust and coal-ash particles was observed in the coarse mode where a significant number of coal ash globules were found attached to the surface of the hematite particles. The morphology of the sharp-edged hematite particles was changed to smooth-edged round particles which proved that hematite particles must have interacted with the surrounding aluminosilicate glassy phase originating from the coal ash. The short-term deposits collected during coal combustion (Case 1) were highly porous in contrast to the high degree of sintering observed in the experiments with pellet dust addition (Case 3) which is attributed to the dissolution of hematite particles in the aluminosilicate glassy phase. The results suggest that pellet dust itself (Case 2) has low slagging tendency, independent of temperature. However, when coal-ash is present (Case 3), auxiliary phases are added such that tenacious particles are formed and slagging occurs.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering Chemical Engineering Chemical Process Engineering
Research subject
Energy Engineering; Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-68712 (URN)10.1016/j.fuproc.2018.05.004 (DOI)000437819600030 ()2-s2.0-85046802389 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-05-14 (andbra)

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2019-01-18Bibliographically approved
Sefidari, H., Lindblom, B., Wiinikka, H., Nordin, L. O., Lennartsson, A., Mouzon, J., . . . Öhman, M. (2018). The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part II: Thermochemical equilibrium calculations and viscosity estimations. Fuel processing technology, 180, 189-206
Open this publication in new window or tab >>The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part II: Thermochemical equilibrium calculations and viscosity estimations
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2018 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 180, p. 189-206Article in journal (Refereed) Published
Abstract [en]

Fly ash particles from the combustion of solid-fuels together with disintegrated particles arising from iron-ore pellets result in accumulation of deposits on the refractory linings of the grate-kiln induration machine during the iron-ore pelletizing process. The deposits amass in the high-temperature regions of the induration furnace thus disturbing the flow of gas and pellets. Therefore, to tackle the above-mentioned issues, an understanding of deposit formation mechanism is of crucial importance. This study was conducted with the objective of addressing the effect of disintegrated iron-ore pellet dust on deposit formation and the mechanisms behind deposition (slagging) in the grate-kiln process. A comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal- fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale setup. Fly ash particles and short-term deposits were characterized and deposition was addressed in Part I of this study. In light of the experimental observations (Part I) and the thermochemical equilibrium calculations (Part II), a scheme of ash transformation during the iron-ore pelletizing process was proposed. The dissolution of hematite particles into the Ca-rich-aluminosilicate melt (from the coal-ash constituents) decreased the viscosity and resulted in the formation of stronger (heavily sintered) deposits. Overall, this pilot-scale work forms part of a wider study which aims at deepening the understanding of ash transformation phenomena during the large-scale pelletizing process.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering Chemical Engineering Metallurgy and Metallic Materials Chemical Process Engineering
Research subject
Energy Engineering; Chemical Technology; Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-69019 (URN)10.1016/j.fuproc.2018.05.005 (DOI)000447580600020 ()2-s2.0-85047214684 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-05 (johcin) 

Available from: 2018-05-31 Created: 2018-05-31 Last updated: 2019-01-18Bibliographically approved
Sundberg, P., Hermansson, S., Tullin, C. & Öhman, M. (2018). Traceability of bulk biomass: Application of radio frequency identification technology on a bulk pellet flow. Biomass and Bioenergy, 118, 149-153
Open this publication in new window or tab >>Traceability of bulk biomass: Application of radio frequency identification technology on a bulk pellet flow
2018 (English)In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 118, p. 149-153Article in journal (Refereed) Published
Abstract [en]

Radio frequency identification (RFID) technology has been used since the 1950s in a wide range of applications. In the energy sector, there is a potential to use the technology to follow biomass fuels throughout a supply chain. In addition to logistic information, the RFID tags can be used to convey vital information of the fuel properties directly to the energy plant to be used at the moment of combustion. A detailed knowledge of the fuel composition at the moment it reaches the furnace can be used to improve energy efficiency, reduce emissions and limit problems with fouling and slagging. In this work, RFID technology was used in three separate trials to trace wood pellets, from the production site to the furnace. In the trials, RFID tags were added to batches of pellets containing 5% or 100% peat. In this way it was possible to follow the shift in pellet quality from standard pellets (100% wood) to the pellets containing the RFID tags by monitoring the change in flue gas composition. From the results it can be concluded that RFID tags indeed can be used to convey logistic information and thus information of fuel quality parameters throughout a supply chain for wood pellets. However, work on optimization is needed to design the RFID carrier properly to mix well with the pellets as illustrated in a separate trial. Finally, an economic estimate indicates that the marginal cost to implement a RFID system would be less than 1% of the total production cost of wood pellets.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-70829 (URN)10.1016/j.biombioe.2018.08.018 (DOI)000445897300018 ()2-s2.0-85052882718 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-09-17 (svasva)

Available from: 2018-09-11 Created: 2018-09-11 Last updated: 2019-03-27Bibliographically approved
Xiong, S., Bozaghian, M., Lestander, T. A., Samuelsson, R., Hellqvist, S. & Öhman, M. (2017). Calcium oxide as an additive for both conservation and improvement of the combustion properties of energy grass: A preliminary study. Biomass and Bioenergy, 99, 1-10
Open this publication in new window or tab >>Calcium oxide as an additive for both conservation and improvement of the combustion properties of energy grass: A preliminary study
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2017 (English)In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 99, p. 1-10Article in journal (Refereed) Published
Abstract [en]

Degradation of biomass is one of the major reasons for high costs of feedstock collection, transport, and storage, which is largely associated with biomass moisture and microbial activities. Our concept is to add calcium oxide (CaO) to the biomass already when it is collected and in its natural (wet) condition. When a suitable quantity of CaO is added to moistened biomass, an alkali microenvironment will be formed with a pH exceeding 9, based on the reaction CaO + H2O ↔ Ca(OH)2. As a consequence, microbial activities are largely inhibited. The Ca(OH)2 will then successively react with CO2, following the reaction Ca(OH)2 + CO2 ↔ CaCO3 + H2O. The CaCO3 will reside in the feedstock throughout the entire production chain and end up as an additive/sorbent to improve combustion by decreasing slagging. Two experiments were conducted and proved the concept works for at least reed canary grass, but, as expected, the strength of the effect was dependent on the CaO dosage and initial biomass moisture.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-62178 (URN)10.1016/j.biombioe.2017.02.010 (DOI)000399515400001 ()2-s2.0-85013452746 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-27 (andbra)

Available from: 2017-02-27 Created: 2017-02-27 Last updated: 2018-09-13Bibliographically approved
Näzelius, I.-L., Boström, D., Rebbing, A., Boman, C. & Öhman, M. (2017). Fuel Indices for Estimation of Slagging of Phosphorus-Poor Biomass in Fixed Bed Combustion. Energy & Fuels, 31(1), 904-915
Open this publication in new window or tab >>Fuel Indices for Estimation of Slagging of Phosphorus-Poor Biomass in Fixed Bed Combustion
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2017 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 1, p. 904-915Article in journal (Refereed) Published
Abstract [en]

The market for solid biofuels will grow rapidly during the coming years and there will be a great demand for raw materials. This will force the existing fuel base to also cover wooden materials of lower qualities as well as agricultural raw materials and residues, which often show unfavorable ash melting temperatures. This may lead to combustion related problems. Thus, for the utilization of lower quality fuels, it is important to be able to predict potential fuel ash related problems such as slagging. In light of this, the first objective of the present paper was to evaluate the applicability of previously defined indices for slagging of biomass fuels (phosphorus-poor) in fixed bed combustion. The evaluation showed that none of the previously suggested indices in the literature are suitable for qualitative (nor quantitative) prediction of slagging during fixed bed combustion of P-poor biomass fuels. Hence, a second objective was to develop improved novel fuel indices that can be applied to estimate the slagging of phosphorus-poor biomass in fixed bed combustion. The novel fuel indices give a qualitative prediction of the slagging tendency in biomass fixed bed combustion but still needs additional work to further extend the compositional range as well as to fine-tune the indices’ boundaries.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-61274 (URN)10.1021/acs.energyfuels.6b02563 (DOI)000392553800094 ()2-s2.0-85018472780 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-23 (andbra)

Available from: 2016-12-27 Created: 2016-12-27 Last updated: 2018-11-20Bibliographically approved
He, H., Skoglund, N. & Öhman, M. (2017). Time-Dependent Crack Layer Formation in Quartz Bed Particles during Fluidized Bed Combustion of Woody Biomass. Energy & Fuels, 31(2), 1672-1677
Open this publication in new window or tab >>Time-Dependent Crack Layer Formation in Quartz Bed Particles during Fluidized Bed Combustion of Woody Biomass
2017 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 2, p. 1672-1677Article in journal (Refereed) Published
Abstract [en]

Bed agglomeration during combustion and gasification of woody biomass fuels in quartz beds has been frequently studied, and chemical mechanisms responsible for bed agglomeration have been suggested. However, few studies have focused on the bed material deposition on walls, in cyclones, and return legs in fluidized bed combustion. Part of these bed material depositions originates from sticky fragments of alkali-rich silicates formed after crack formation in older quartz bed particles. The crack layer formation in quartz bed particles in fluidized bed combustion of woody biomass was therefore investigated by collecting bed material samples of different ages from full-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the crack morphology and composition of the layer surrounding the cracks. For quartz bed particles with an age of some days, a crack in the quartz bed particle was observed in connection to the irregular interface between the inner layer and the core of the bed particle. The crack layer composition is similar for quartz particles with different ages and for samples taken from different fluidized bed techniques. Their composition is dominated by Si, K, Ca, and Na (except O). These crack layers become deeper, wider, and more common as bed particle age increases. The crack layers eventually connect with each other, and the whole quartz particle is transformed into smaller quartz cores surrounded by crack layers, which were observed in particles older than 1 week. From the characterization work, a crack formation process including three phases is proposed on the basis of the presumption that the initial crack layer formation resulted from the presence of induced cracks in the inner quartz bed particle layer. Fragmentation after the third phase is likely responsible for the formation of sticky alkali silicate deposit formation, and a weekly complete exchange of the bed is therefore recommended to avoid problematic deposits in combustion of woody-type biomass in fluidized bed combustion

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-62219 (URN)10.1021/acs.energyfuels.6b02980 (DOI)000394560900066 ()2-s2.0-85014407817 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-03-14 (andbra)

Available from: 2017-02-28 Created: 2017-02-28 Last updated: 2018-11-20Bibliographically approved
He, H., Skoglund, N. & Öhman, M. (2017). Time-dependent layer formation on K-feldspar bed particles during fluidized bed combustion of woody fuels. Energy & Fuels, 31(11), 12848-12856
Open this publication in new window or tab >>Time-dependent layer formation on K-feldspar bed particles during fluidized bed combustion of woody fuels
2017 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 11, p. 12848-12856Article in journal (Refereed) Published
Abstract [en]

Despite frequent reports on layer characteristics on quartz bed particles, few studies have been found focusing on the layer characteristics on K-feldspar bed particles. The layer characteristics of K-feldspar bed particles in fluidized bed combustion of woody biomass was therefore investigated by collecting bed material samples of different ages from large-scale bubbling and circulating fluidized bed facilities. Scanning electron microscopy/energy-dispersive spectroscopy was used to analyze the layer morphology and elemental composition. For particles with an age of 1 day, a thin layer rich in Si, Ca and Al was found. For particles older than some days, an inner more homogenous layer containing cracks and an outer more particle-rich layer were observed. The outer layer was thinner for K-feldspar bed particles sampled from circulating fluidized bed, compared to particles from bubbling fluidized bed. The concentration of Ca in the inner layer increases towards bed particle surface, the molar ratio of Si/Al is maintained, and the molar ratio of K/Al decreases compared to the K-feldspar. The inner layer thickness for quartz and K-feldspar bed particles collected at the same operation conditions was found to be similar. No crack layers, as have been observed in quartz particles, were found in the core of the K-feldspar bed particles. The results suggest that the diffusion and reaction of Ca2+ into/with the feldspar particle play an important role on the inner layer formation process.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-66257 (URN)10.1021/acs.energyfuels.7b02386 (DOI)2-s2.0-85034573363 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-20 (andbra)

Available from: 2017-10-25 Created: 2017-10-25 Last updated: 2017-12-05Bibliographically approved
Ma, C., Carlborg, M., Hedman, H., Wennebro, J., Weiland, F., Wiinikka, H., . . . Öhman, M. (2016). Ash Formation in Pilot-Scale Pressurized Entrained-Flow Gasification of Bark and a Bark/Peat Mixture. Energy & Fuels, 30(12), 10543-10554
Open this publication in new window or tab >>Ash Formation in Pilot-Scale Pressurized Entrained-Flow Gasification of Bark and a Bark/Peat Mixture
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2016 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 12, p. 10543-10554Article in journal (Refereed) Published
Abstract [en]

Pressurized entrained-flow gasification (PEFG) of bark and a bark/peat mixture (BPM) was carried out in a pilot-scale reactor (600 kWth, 7 bar(a)) with the objective of studying ash transformations and behaviors. The bark fuel produced a sintered but nonflowing reactor slag, while the BPM fuel produced a flowing reactor slag. Si was enriched within these slags compared to their original fuel ash compositions, especially in the bark campaign, which indicated extensive ash matter fractionation. Thermodynamically, the Si contents largely accounted for the differences in the predicted solidus/liquidus temperatures and melt formations of the reactor slags. Suspension flow viscosity estimations were in qualitative agreement with observations and highlighted potential difficulties in controlling slag flow. Quench solids from the bark campaign were mainly composed of heterogeneous particles resembling reactor fly ash particles, while those from the BPM campaign were flowing slags with likely chemical interactions with the wall refractory. Quench effluents and raw syngas particles were dominated by elevated levels of K that, along with other chemical aspects, indicated KOH(g) and/or K(g) were likely formed during PEFG. Overall, the results provide information toward development of woody biomass PEFG and indicate that detailed understanding of the ash matter fractionation behavior is essential.

National Category
Energy Systems Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-61329 (URN)10.1021/acs.energyfuels.6b02222 (DOI)000390072900057 ()2-s2.0-85006511826 (Scopus ID)
Funder
Swedish Energy AgencyBio4Energy
Note

Validerad; 2017; Nivå 2; 2017-01-12 (andbra)

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2018-07-10Bibliographically approved
Kuba, M., He, H., Kirnbauer, F., Skoglund, N., Boström, D., Öhman, M. & Hoffbauer, H. (2016). Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood. Energy & Fuels, 30(9), 7410-7418
Open this publication in new window or tab >>Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood
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2016 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 9, p. 7410-7418Article in journal (Refereed) Published
Abstract [en]

Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid-solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-59285 (URN)10.1021/acs.energyfuels.6b01522 (DOI)000383641000056 ()2-s2.0-84987984789 (Scopus ID)
Note

Validerad; 2016; Nivå 2; 2016-10-10 (andbra)

Available from: 2016-10-04 Created: 2016-10-04 Last updated: 2018-07-10Bibliographically approved
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