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Publications (10 of 31) Show all publications
Wagner, D. R., Holmgren, P., Skoglund, N. & Broström, M. (2018). Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions. Review of Scientific Instruments, 89(6), Article ID 065101.
Open this publication in new window or tab >>Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions
2018 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 6, article id 065101Article in journal (Refereed) Published
Abstract [en]

The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-69223 (URN)10.1063/1.5030603 (DOI)000437195200054 ()2-s2.0-85048128383 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-08 (andbra)

Available from: 2018-06-08 Created: 2018-06-08 Last updated: 2018-08-10Bibliographically approved
Qu, Z., Holmgren, P., Skoglund, N., Wagner, D. R., Broström, M. & Schmidt, F. M. (2018). Distribution of temperature, H2O and atomic potassium during entrained flow biomass combustion: Coupling in situ TDLAS with modeling approaches and ash chemistry. Combustion and Flame, 188, 488-497
Open this publication in new window or tab >>Distribution of temperature, H2O and atomic potassium during entrained flow biomass combustion: Coupling in situ TDLAS with modeling approaches and ash chemistry
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2018 (English)In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 188, p. 488-497Article in journal (Refereed) Published
Abstract [en]

Tunable diode laser absorption spectroscopy (TDLAS) is employed for simultaneous detection of gas temperature, water vapor (H2O) and gas-phase atomic potassium, K(g), in an atmospheric, research-scale entrained flow reactor (EFR). In situ measurements are conducted at four different locations in the EFR core to study the progress of thermochemical conversion of softwood and Miscanthus powders with focus on the primary potassium reactions. In an initial validation step during propane flame operation, the measured axial EFR profiles of H2O density-weighted, path-averaged temperature, path-averaged H2O concentration and H2O column density are found in good agreement with 2D CFD simulations and standard flue gas analysis. During biomass conversion, temperature and H2O are significantly higher than for the propane flame, up to 1500 K and 9%, respectively, and K(g) concentrations between 0.2 and 270 ppbv are observed. Despite the large difference in initial potassium content between the fuels, the K(g) concentrations obtained at each EFR location are comparable, which highlights the importance of considering all major ash-forming elements in the fuel matrix. For both fuels, temperature and K(g) decrease with residence time, and in the lower part of the EFR, K(g) is in excellent agreement with thermodynamic equilibrium calculations evaluated at the TDLAS-measured temperatures and H2O concentrations. However, in the upper part of the EFR, where the measured H2O suggested a global equivalence ratio smaller than unity, K(g) is far below the predicted equilibrium values. This indicates that, in contrast to the organic compounds, potassium species rapidly undergo primary ash transformation reactions even if the fuel particles reside in an oxygen-deficient environment

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-66385 (URN)10.1016/j.combustflame.2017.10.013 (DOI)000424859100040 ()2-s2.0-85032255301 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-06 (andbra)

Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2018-03-02Bibliographically approved
Skoglund, N., Werner, K., Nylund, G. M., Pavia, H., Albers, E. & Broström, M. (2017). Combustion of seaweed: A fuel design strategy. Fuel processing technology, 165, 155-161
Open this publication in new window or tab >>Combustion of seaweed: A fuel design strategy
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2017 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 165, p. 155-161Article in journal (Refereed) Published
Abstract [en]

The high ash content and varying ash composition in algal biomass is often mentioned as problematic if to be used for thermal energy conversion. This paper suggests an approach where detailed information on ash composition and predicted ash formation reactions are basis for successful remedies enabling the use of fuels considered to be difficult. The procedure is demonstrated on seaweed (Saccharina latissima) cultivated for biorefinery purposes. The ash composition of the seaweed was found suitable for co-combustion with Miscanthus x giganteus, an energy crop high in alkali and silicon. Fuel mixtures were combusted in a bubbling fluidized bed reactor and ash samples were analyzed by SEM-EDS and XRD. The results showed that Ca from the seaweed was very reactive and thus efficient in solving the silicate melting problems. The fuel design approach was proven successful and the potential for using otherwise difficult seaweed fuels in synergetic co-combustion was demonstrated.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-63481 (URN)10.1016/j.fuproc.2017.04.017 (DOI)000403987400019 ()2-s2.0-85019946204 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-06-09 (andbra)

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2018-07-10Bibliographically approved
Edo, M., Skoglund, N., Gao, Q., Persson, P.-E. & Jansson, S. (2017). Fate of metals and emissions of organic pollutants from torrefaction of waste wood, MSW, and RDF. Waste Management, 68, 646-652
Open this publication in new window or tab >>Fate of metals and emissions of organic pollutants from torrefaction of waste wood, MSW, and RDF
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2017 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 68, p. 646-652Article in journal (Refereed) Published
Abstract [en]

Torrefaction of municipal solid waste (MSW), refuse-derived fuel (RDF), and demolition and construction wood (DC) was performed at 220 °C and a residence time of 90 min in a bench-scale reactor. The levels of toxic polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) contained in emission from the torrefaction process were evaluated. In addition, main ash-forming elements and trace metals in the raw feedstock and char were determined. The use of MSW in fuel blends with DC resulted in lower PCDD and PCDF emissions after torrefaction, compared with the RDF blends. The migration of chlorine from the feedstock to the gas phase reduces the chlorine content of the char which may reduce the risk of alkali chloride-corrosion in char combustion. However, trace metals catalytically active in the formation of PCDD and PCDF remain in the char, thereby may promote PCDD and PCDF formation during subsequent char combustion for energy recovery; this formation is less extensive than when the feedstock is used.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-64276 (URN)10.1016/j.wasman.2017.06.017 (DOI)000413126300065 ()28633911 (PubMedID)2-s2.0-85020515019 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-09-25 (andbra)

Available from: 2017-06-20 Created: 2017-06-20 Last updated: 2018-07-10Bibliographically 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
Skoglund, N., Bäfver, L., Fahlström, J., Holmén, E. & Renström, C. (2016). Fuel design in co-combustion of demolition wood chips and municipal sewage sludge (ed.). Paper presented at . Fuel processing technology, 141(2), 196-201
Open this publication in new window or tab >>Fuel design in co-combustion of demolition wood chips and municipal sewage sludge
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2016 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 141, no 2, p. 196-201Article in journal (Refereed) Published
Abstract [en]

Municipal sewage sludge (MSS) is a waste stream resource which contains both energy and elements such as phosphorus which could be recycled. If these two aspects of this waste stream resource are to be used to their full potential the sludge should not be used in landfills or road construction. There is some use of sludge in agriculture today but not all MSS produced is suitable for direct use on arable land due to its content of potentially harmful elements, pathogens or anthropogenic chemicals. By combusting sludge that is not used directly in agriculture the problematic organic content could be destroyed. The combustion process also produces an ash that possibly could be used either directly in agriculture or as a raw material for recovering phosphorus and energy could be recovered. Building mono-combustion plants for sewage sludge is not economically feasible in all parts of the world so it is of interest to investigate how MSS can be introduced together with other fuels in existing infrastructure which already have extensive cleaning systems for potentially harmful elements.To investigate this possible path, demolition wood chips (DWC) were co-combusted with municipal sewage sludge (MSS) in a grate-fired combined heat and power plant running at 50% capacity producing 25 MWth and 9 MWel. The amount of MSS that was suitable to introduce in blends was determined using a “fuel fingerprint” based on the composition of the raw materials. Thermodynamic equilibrium calculations were made to evaluate potential problems with slagging based on the ash content prior to the combustion experiments. The fuels were introduced as a reference case with only demolition wood and pre-blended fuel mixtures in two ratios; 65 w/w-% DWC/35 w/w-% MSS and 55 w/w-% DWC/45 w/w-% MSS and were fired for 12 h. The high water content of the MSS affected how much MSS that could be introduced without compromising the heat and power production.The fuel blends worked nicely for 12 h of continuous combustion with small adjustments where the primarily the air inlet configuration was changed. The main problems encountered related to cleaning of the flue gases and to some extent ash removal. The bed ash and fly ash produced was analysed both using ICP-AES (elemental) and XRD (speciation) and the bottom ash was subjected to ash melting tests. The major nutrient phosphorus was mainly found in bottom ash (80 w/w-%) as whitlockites with some hydroxyapatite whereas fly ash (20 w/w-%) contained larger amounts of hydroxyapatite, especially for the reference fuel. The amount of alkali chloride in the fly ash was reduced in favour of alkali sulphate formation.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-12373 (URN)10.1016/j.fuproc.2015.08.037 (DOI)000366779400004 ()2-s2.0-84948567111 (Scopus ID)b805ece9-1ab4-44fa-a7c9-069751dfaae2 (Local ID)b805ece9-1ab4-44fa-a7c9-069751dfaae2 (Archive number)b805ece9-1ab4-44fa-a7c9-069751dfaae2 (OAI)
Note
Validerad; 2016; Nivå 2; 20150914 (andbra)Available from: 2016-09-29 Created: 2016-09-29 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
Kumpiene, J., Brännvall, E., Wolters, M., Skoglund, N., Cirba, S. & Aksamitauskas, V. C. (2016). Phosphorus and cadmium availability in soil fertilized with biosolids and ashes (ed.). Chemosphere, 151, 124-132
Open this publication in new window or tab >>Phosphorus and cadmium availability in soil fertilized with biosolids and ashes
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2016 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 151, p. 124-132Article in journal (Refereed) Published
Abstract [en]

The recycling of hygienized municipal sewage sludge (biosolids) to soil as the source of phosphorus (P) is generally encouraged. The use of biosolids, however, has some concerns, such as the presence of elevated concentrations of potentially toxic trace elements, and the possible presence of pathogens, hormones and antibiotics. Organic substances are destroyed during combustion whereas trace elements could partly be separated from P in different ash fractions. Biomass combustion waste (ash) can instead be considered as an alternative P source. This study evaluates and compares the impact of biosolids and their combustion residues (ashes), when used as fertilizers, on P and Cd solubility in soil, plant growth and plant uptake of these elements. Biosolids were also amended with K and Ca to improve the composition and properties of P in ashes, and incinerated at either 800 °C or 950 °C. Combustion of biosolids improved the Cd/P ratio in ashes by 2-5 times, compared with the initial biosolids. The low Cd content in ashes (4-9 mg Cd (kg P)-1) makes this material a particularly attractive alternative to mineral fertilizers. Significantly higher pore water P (as well as total N) was measured in soils containing biosolids, but plants produced a higher biomass in soil fertilized with ashes. The K and Ca amendments prior to biosolids combustion generally decreased the total Cd in ash, but had little effect on P and Cd uptake and biomass growth. Similarly, the combustion temperature had negligible effect on these factors as well

National Category
Other Environmental Engineering Energy Engineering
Research subject
Waste Science and Technology; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-9570 (URN)10.1016/j.chemosphere.2016.02.069 (DOI)000374071000016 ()26933903 (PubMedID)2-s2.0-84959221559 (Scopus ID)8383e6a4-cd0f-4090-bd47-01caffdd123e (Local ID)8383e6a4-cd0f-4090-bd47-01caffdd123e (Archive number)8383e6a4-cd0f-4090-bd47-01caffdd123e (OAI)
Note

Validerad; 2016; Nivå 2; 20160307 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Reyes, D. C., Skoglund, N., Svedberg, A., Eliasson, B. & Sundman, O. (2016). The influence of different parameters on the mercerisation of cellulose for viscose production (ed.). Paper presented at . Cellulose (London), 23(2), 1061-1072
Open this publication in new window or tab >>The influence of different parameters on the mercerisation of cellulose for viscose production
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2016 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 2, p. 1061-1072Article in journal (Refereed) Published
Abstract [en]

A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 °C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25–1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-6726 (URN)10.1007/s10570-016-0879-0 (DOI)000373136400005 ()2-s2.0-84957694846 (Scopus ID)501cc6af-3753-472a-bd66-b72ddcd36aff (Local ID)501cc6af-3753-472a-bd66-b72ddcd36aff (Archive number)501cc6af-3753-472a-bd66-b72ddcd36aff (OAI)
Note
Validerad; 2016; Nivå 2; 20160211 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Projects
Fundamental studies of chemical speciation in ash fractions from thermal conversion of biomass and waste streams focusing on phosphates and heavy metals [2017-05331_VR]; Umeå University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5777-9241

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