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Rebbling, A., Sundberg, P., Fagerström, J., Carlborg, M., Tullin, C., Boström, D., . . . Skoglund, N. (2020). Demonstrating Fuel Design To Reduce Particulate Emissions and Control Slagging in Industrial-Scale Grate Combustion of Woody Biomass. Energy & Fuels, 34(2), 2574-2583
Open this publication in new window or tab >>Demonstrating Fuel Design To Reduce Particulate Emissions and Control Slagging in Industrial-Scale Grate Combustion of Woody Biomass
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2020 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, no 2, p. 2574-2583Article in journal (Refereed) Published
Abstract [en]

The demand for increased overall efficiency, improved fuel flexibility, and more stringent environmental legislations promotes the development of new fuel- and technology-related concepts for the bioenergy sector. Previous research has shown that careful consideration of the fuel ash composition and the adjustment of the same via various routes, i.e., fuel design, have the potential to alter the ash transformation reactions, leading to, e.g., a reduction of the formation of slag or entrained inorganic ash particles. The objective of the present work was, therefore, to demonstrate the use of fuel design as a primary measure to reduce the emission of PM1 during combustion of woody biomass in medium-scale grate-fired boilers while keeping the slag formation at a manageable level. This was achieved by designing fuel blends of woody biomass with carefully selected Scandinavian peats rich in Si, Ca, and S. The work includes results from three experimental campaigns, performed in three separate grate-fired boilers of different sizes, specifically 0.2 MWth, 2 MWth, and 4 MWth. In one of the campaigns, softwood-based stemwood pellets were copelletized with different additions of peat (5 and 15 wt %) before combustion. In the other campaigns, peat was added in a separate fuel feed to Salix chips (15 wt % peat) and softwood-based stemwood pellets (10 and 20 wt % peat). Particulate matter and bottom ashes were characterized by scanning electron microscopy-energy-dispersive X-ray spectroscopy for morphology and elemental composition as well as by powder X-ray diffraction for crystalline phase composition. The results show that the fuel design approach provided PM1 reduction for all fuel blends between 30 and 50%. The PM1 reduction could be achieved without causing operational problems due to slagging for any of the three commercial boilers used, although an expected increased slagging tendency was observed. Overall, this paper illustrates that fuel design can be implemented on an industrial scale by achieving the desired ash transformation reactions, in this case, leading to a reduction of fine particulate emissions by up to 50% without any operational disturbances due to slag formation on the grate.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
Keywords
Redox reactions, Reaction products, Biomass, Fuels, Particulate matter
National Category
Energy Engineering
Identifiers
urn:nbn:se:umu:diva-169362 (URN)10.1021/acs.energyfuels.9b03935 (DOI)000518215400147 ()
Available from: 2020-04-07 Created: 2020-04-07 Last updated: 2020-04-07Bibliographically approved
Häggström, G., Wagner, K., Kuba, M., Skoglund, N. & Öhman, M. (2020). Effect on P-mineralization in fluidized bed combustion of chicken litter with wheat straw and bark residues. Paper presented at 27th International Conference of Impacts of Fuel Quality on Power Production and the Environment, 23–28 September, 2018, Lake Louise, Canada. Energy & Fuels, 34(2), 1822-1829
Open this publication in new window or tab >>Effect on P-mineralization in fluidized bed combustion of chicken litter with wheat straw and bark residues
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2020 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, no 2, p. 1822-1829Article in journal (Refereed) Published
Abstract [en]

This study aims to determine the fate of P during fluidized bed co-combustion of chicken litter (CL) with K-rich fuels [e.g., wheat straw (WS)] and Ca-rich fuels (bark). The effect of fuel blending on phosphate speciation in ash was investigated. This was performed by chemical characterization of ash fractions to determine which phosphate compounds had formed and identify plausible ash transformation reactions for P. The ash fractions were produced in combustion experiments using CL and fuel blends with 30% CL and WS or bark (B) at 790–810 °C in a 5 kW laboratory-scale bubbling fluidized bed. Potassium feldspar was used as the bed material. Bed ash particles, cyclone ash, and particulate matter (PM) were collected and subjected to chemical analysis with scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) and X-ray diffraction. P was detected in coarse ash fractions only, that is, bed ash, cyclone ash, and coarse PM fraction (>1 μm); no P could be detected in the fine PM fraction (<1 μm). SEM–EDS analysis showed that P was mainly present in K–Ca–P-rich areas for pure CL as well as in the ashes from the fuel blends of CL with WS or B. In the WS blend, P was found together with Si in these areas. The crystalline compound containing P was hydroxyapatite in all cases as well as whitlockite in the cases of pure CL and WS blend, of which the latter compound has been previously identified as a promising plant nutrient. The ash fractions from CL and bark blend only contained P in hydroxyapatite. Co-combustion of CL together with WS appears to be promising for P recovery, and ashes with this composition could be further studied in plant growth experiments.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
Keywords
Phosphates, Chemical reactions, Fuels, Reaction products, Materials
National Category
Energy Engineering Other Chemistry Topics
Identifiers
urn:nbn:se:umu:diva-157283 (URN)10.1021/acs.energyfuels.9b03652 (DOI)
Conference
27th International Conference of Impacts of Fuel Quality on Power Production and the Environment, 23–28 September, 2018, Lake Louise, Canada
Funder
Swedish Research Council Formas, 2015-619
Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2020-04-06Bibliographically approved
Falk, J., Skoglund, N., Grimm, A. & Öhman, M. (2020). Fate of Phosphorus in Fixed Bed Combustion of Biomass and Sewage Sludge. Energy & Fuels, 34(4), 4587-4594
Open this publication in new window or tab >>Fate of Phosphorus in Fixed Bed Combustion of Biomass and Sewage Sludge
2020 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, no 4, p. 4587-4594Article in journal (Refereed) Published
Abstract [en]

The recovery of phosphorus (P) from societal waste streams, such as sewage sludge, could make a significant contribution to alleviating the global dependency upon non-renewable phosphate sources, such as phosphate rock. This study aims to determine the effect of fuel ash composition, chemical association, and combustion technology on the fate of P in ashes from the combustion of sewage sludge and biomass blends to enable more efficient P recovery from combustion ashes. Experiments were performed in a fixed bed pellet burner (20 kW), combusting two sewage sludge blends and three biomass blends of similar fuel ash composition but with different P source (sewage sludge, dried distiller's grain with solubles, or phosphoric acid). Slag, bottom ash, and particulate matter samples were collected and analyzed by scanning electron microscopy-energy-dispersive X-ray spectroscopy and X-ray diffraction for morphology and elemental and crystalline phase composition and compared to results from experiments in fluidized bed combustion using the same fuel blends reported separately. The distribution and elemental composition of ash fractions indicated that sub-micrometer particles contained a minor share of fuel P, with the significant share of fuel P found in the slag and bottom ash fractions. No apparent difference in phosphate speciation could be observed between the slag and bottom ash from sewage sludge blends and biomass blends, with a range of crystalline Ca, Mg, and K phosphates detected in the ash. By comparison, only Ca-rich phosphates were detected in the ashes from the combustion of the sewage sludge blends in the bench-scale fluidized bed. The difference in P speciation between the technologies was attributed to a difference in the process temperature between the two technologies. In comparison to fluidized bed combustion, fixed bed combustion favored the formation of (Ca, Mg)-K phosphates rather than Ca phosphates for similar fuel blends.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
National Category
Energy Engineering
Identifiers
urn:nbn:se:umu:diva-170546 (URN)10.1021/acs.energyfuels.9b03976 (DOI)000526324100055 ()
Funder
Swedish Research Council Formas, 942-2015-619Swedish Research Council, 2017-05331
Available from: 2020-05-15 Created: 2020-05-15 Last updated: 2020-05-15Bibliographically approved
Falk, J., Skoglund, N., Grimm, A. & Ohman, M. (2020). Systematic Evaluation of the Fate of Phosphorus in Fluidized Bed Combustion of Biomass and Sewage Sludge. Energy & Fuels, 34(4), 3984-3995
Open this publication in new window or tab >>Systematic Evaluation of the Fate of Phosphorus in Fluidized Bed Combustion of Biomass and Sewage Sludge
2020 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, no 4, p. 3984-3995Article, review/survey (Refereed) Published
Abstract [en]

Comprehensive knowledge concerning the behavior of phosphorus (P) during combustion is necessary to enable more efficient recovery of P from combustion ashes for agricultural purposes. To this end, parameters that influence the distribution and speciation of P in combustion ashes are important because they may influence which ash fractions are suitable for P recovery. This study aims to determine the fate of P as a result of fuel ash composition and chemical association in the fuel during fluidized bed combustion by a systemic review of previous work. The synthesis was performed by comparing scanning electron microscopy–energy-dispersive X-ray spectroscopy and X-ray diffraction chemical analyses of bed ash, fly ash particles, and deposits from fluidized bed combustion of different blends of P-poor (logging residues or wheat straw) and P-rich (sewage sludge, dried distiller’s grain with solubles, or phosphoric acid) fuels and additives. The blends were produced to have a similar ash composition but with a different P source. The distribution of P among ash fractions indicated that P is mainly found in the coarse ash fractions (bed and cyclone ash), irrespective of fuel ash composition or chemical association in the fuel. The chemical speciation of P in coarse ash fractions differed between biomass blends containing sewage sludge compared to blends with phosphoric acid or dried distiller’s grain with solubles. Phosphates in the ash from the two sewage sludge blends included predominantly Ca with minor inclusion of other cations. In contrast, ashes from the blends with phosphoric acid or dried distiller’s grain with solubles contained phosphates with a significant amount of K, Ca, and Mg. The difference in phosphate speciation could not solely be explained by the combustion conditions and the elemental composition of the ash fractions. These results show that it is necessary to consider the chemical association of P in the fuel to predict the type of phosphates that will form in fluidized bed combustion ashes.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
National Category
Bioenergy
Identifiers
urn:nbn:se:umu:diva-170545 (URN)10.1021/acs.energyfuels.9b03975 (DOI)000526324100002 ()
Funder
Swedish Research Council Formas, 942-2015-619Swedish Research Council, 2017-05331
Available from: 2020-05-27 Created: 2020-05-27 Last updated: 2020-05-27Bibliographically approved
Ma, C., Skoglund, N., Carlborg, M. & Broström, M. (2020). Viscosity of molten CaO-K2O-SiO2 woody biomass ash slags in relation to structural characteristics from molecular dynamics simulation. Chemical Engineering Science, 215, Article ID 115464.
Open this publication in new window or tab >>Viscosity of molten CaO-K2O-SiO2 woody biomass ash slags in relation to structural characteristics from molecular dynamics simulation
2020 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 215, article id 115464Article in journal (Refereed) Published
Abstract [en]

Molten compositions in the CaO-K2O-SiO2 system relevant to woody biomass ash slags were simulated with molecular dynamics to extract structural characteristics. Multivariate analysis elucidated correlations of these structural characteristics with viscosity measurements. The simulations show SiO4/silicate tetrahedral units (STUB) diffusing slowly and forming flexible networks via oxygen bridges. The degree of STU polymerization varies linearly with the (K2O + CaO)/SiO2 ratio. Ca depolymerises stronger than K, but K diffuses quicker. Depolymerization and diffusion cause network disruptions and agitations that promote collective atomic mobility of the system. This imposes structural characteristics in the slag that correlate with viscosity. The inter-STU Si-O-Si angle narrows with decreasing viscosity, while the Si-O bond length of these bridges increases. Attributes related to atomic mobility, such as the variations in the Si-O-Si angle and the distance of nearest Si-Si pairs, also correlate with viscosity. The discussion provides insight into the connection between structural characteristics and viscosity.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Viscosity, Biomass ash, Slag, Molecular dynamics, Silicate melt
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:umu:diva-169464 (URN)10.1016/j.ces.2019.115464 (DOI)000520029300037 ()
Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved
Strandberg, A., Skoglund, N. & Thyrel, M. (2019). Characterization of porosity and microstructure of phosphorus-rich ash particles with X-ray micro-tomography. In: : . Paper presented at Nordic Flame Days, Turku, Finland, 28-29 August, 2019.
Open this publication in new window or tab >>Characterization of porosity and microstructure of phosphorus-rich ash particles with X-ray micro-tomography
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

A large proportion of the nutrients supplied from forest and agricultural sector are lost today, both through leaching and removing of produced biomass. Sustainable and efficient recycling of macro- and micro nutrients can be done by combustion / co-combustion of residual streams, which makes it possible to utilize for example the phosphorus-bound fraction in the produced ash for further processing and recycling. The porosity of the ash is important for, among other things, leaching and water-retaining ability when returning to the soil. The purpose of the project is to provide detailed knowledge of porosity and internal microstructure of ash particles from combustion of residual biomass streams, by using X-ray based micro-tomography and image analysis. The results provide new insights into how ash porosity and micro structure differs between different ashes, depending on fuel and the choice of conversion process.

National Category
Chemical Sciences Engineering and Technology
Identifiers
urn:nbn:se:umu:diva-163277 (URN)
Conference
Nordic Flame Days, Turku, Finland, 28-29 August, 2019
Available from: 2019-09-12 Created: 2019-09-12 Last updated: 2019-10-23Bibliographically approved
Skoglund, N., Strandberg, A., Öhman, M. & Boström, D. (2019). Elemental approaches to additives: mechanisms and dosage. In: : . Paper presented at World Sustainable Energy Days, REFAWOOD workshop session, 28 February, 2019, Wels, Austria.
Open this publication in new window or tab >>Elemental approaches to additives: mechanisms and dosage
2019 (English)Conference paper, Oral presentation only (Other academic)
National Category
Energy Engineering
Identifiers
urn:nbn:se:umu:diva-157287 (URN)
Conference
World Sustainable Energy Days, REFAWOOD workshop session, 28 February, 2019, Wels, Austria
Note

Funded by the ERA-NET project REFAWOOD

Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2020-02-24Bibliographically approved
Skoglund, N. (2019). Inorganic chemistry and bioenergy - an unexpected match?. In: : . Paper presented at Inorganic Days, Umeå, Sweden, June 12-14, 2019.
Open this publication in new window or tab >>Inorganic chemistry and bioenergy - an unexpected match?
2019 (English)Conference paper, Oral presentation only (Other academic)
National Category
Inorganic Chemistry Other Chemistry Topics
Identifiers
urn:nbn:se:umu:diva-160830 (URN)
Conference
Inorganic Days, Umeå, Sweden, June 12-14, 2019
Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-25Bibliographically approved
Wagner, K., Häggström, G., Skoglund, N., Priscak, J., Kuba, M., Öhman, M. & Hofbauer, H. (2019). Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass. Applied Energy, 248, 545-554
Open this publication in new window or tab >>Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass
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2019 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 248, p. 545-554Article in journal (Refereed) Published
Abstract [en]

The use of phosphorus-rich fuels in fluidized bed combustion is one probable way to support both heat and power production and phosphorus recovery. Ash is accumulated in the bed during combustion and interacts with the bed material to form layers and/or agglomerates, possibly removing phosphorus from the bed ash fraction. To further deepen the knowledge about the difference in the mechanisms behind the ash chemistry of phosphorus -lean and phosphorus-rich fuels, experiments in a 5 kW bench-scale-fluidized bed test-rig with K-feldspar as the bed material were conducted with bark, wheat straw, chicken manure, and chicken manure admixtures to bark and straw. Bed material samples were collected and studied for layer formation and agglomeration phenomena by scanning electron microscopy combined with energy dispersive X-ray spectrometry. The admixture of phosphorus-rich chicken manure to bark changed the layer formation mechanism, shifting the chemistry to the formation of phosphates rather than silicates. The admixture of chicken manure to straw reduced the ash melting and agglomeration risk, making it possible to increase the time until defluidization of the fluidized bed occurred. The results also highlight that an increased ash content does not necessarily lead to more ash melting related problems if the ash melting temperature is high enough.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Phosphorus, Layer formation, Agglomeration, K-feldspar, Fluidized bed
National Category
Energy Engineering Inorganic Chemistry
Identifiers
urn:nbn:se:umu:diva-160593 (URN)10.1016/j.apenergy.2019.04.112 (DOI)000469891900044 ()2-s2.0-85064643200 (Scopus ID)
Projects
Bio4Energy
Funder
The Kempe Foundations
Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-09-02Bibliographically approved
Wagner, K., Häggström, G., Mauerhofer, A. M., Kuba, M., Skoglund, N., Öhman, M. & Hofbauer, H. (2019). Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure. Paper presented at 26th European Biomass Conference and Exhibition (EUBCE), Copenhagen, Denmark, May 14-17, 2018. Biomass and Bioenergy, 127, Article ID 105251.
Open this publication in new window or tab >>Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure
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2019 (English)In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 127, article id 105251Article in journal (Refereed) Published
Abstract [en]

Understanding layer formation on bed materials used in fluidized beds is a key step for advances in the application of alternative fuels. Layers can be responsible for agglomeration-caused shut-downs but they can also improve the gas composition in fluidized bed gasification. Layers were observed on K-feldspar (KAlSi3O8) impurities originating from the combined heat and power plant Senden which applies the dual fluidized bed (DFB) steam gasification technology. Pure K-feldspar was therefore considered as alternative bed material in DFB steam gasification. Focusing on the interactions between fuel ash and bed material, K-feldspar was tested in combustion and DFB steam gasification atmospheres using different fuels, namely Ca-rich bark, Ca -and P-rich chicken manure, and an admixture of chicken manure to bark. The bed particle layers formed on the bed material surface were characterized using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans were carried out for all samples. The obtained data show no essential influence of operational mode on the layer-formation process. During the combustion and DFB steam gasification of Ca-rich bark, a layer rich in Ca formed while K was diffusing out of the layer. The use of Ca -and P-rich chicken manure inhibited the diffusion of K, and a layer rich in Ca and P formed. The addition of P to bark via chicken manure also changed the underlying layer-formation processes to reflect the same processes as observed for pure chicken manure.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fluidized bed, Layer formation, K-feldspar, Phosphorous, Combustion, DFB steam gasification
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:umu:diva-162319 (URN)10.1016/j.biombioe.2019.05.020 (DOI)000478564300032 ()
Conference
26th European Biomass Conference and Exhibition (EUBCE), Copenhagen, Denmark, May 14-17, 2018
Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2020-03-10Bibliographically 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; Publications
Falk, J., Skoglund, N., Grimm, A. & Ohman, M. (2020). Systematic Evaluation of the Fate of Phosphorus in Fluidized Bed Combustion of Biomass and Sewage Sludge. Energy & Fuels, 34(4), 3984-3995
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5777-9241

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