umu.sePublications
Change search
Link to record
Permanent link

Direct link
BETA
Backman, Rainer
Alternative names
Publications (10 of 57) Show all publications
Strandberg, A., Thyrel, M., Skoglund, N., Lestander, T. A., Broström, M. & Backman, R. (2018). Biomass pellet combustion: cavities and ash formation characterized by synchrotron X-ray micro-tomography. Fuel processing technology, 176, 211-220
Open this publication in new window or tab >>Biomass pellet combustion: cavities and ash formation characterized by synchrotron X-ray micro-tomography
Show others...
2018 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 176, p. 211-220Article in journal (Refereed) Published
Abstract [en]

Ash formation during thermochemical conversion of biomass-based pellets influences both char conversion rates and ash-related operational problems. The objective of the present study was to provide detailed insights into changes in fuel and ash properties during fuel conversion. Pellets of poplar wood and wheat straw were used as model biofuels, representing vastly different compositions of ash-forming elements. Pellet samples at different char conversion phases were analyzed by synchrotron-based 3D X-ray micro-tomography, to map and visualize the development of cracks, internal cavities, and ash layers during conversion. The analysis of ash layers was complemented by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. The results provide new insights into how large cracks and internal cavities are developed already during devolatilization, for example, the poplar wood pellets had a 64% void fraction after the devolatilization stage. As expected, there were large variations between the ash layer properties for the two fuels. A porous, low density, and calcium-rich ash was formed from the poplar fuel, whereas the wheat straw ash was a high-density silicate melt that developed into bubbles on the surface. As the conversion proceeded, the wheat straw ash covered parts of the active char surface area, but without blocking the gas transport.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
ash composition, pellet, thermochemical conversion, wheat straw, poplar, SEM-EDS
National Category
Chemical Process Engineering Bioenergy
Identifiers
urn:nbn:se:umu:diva-146673 (URN)10.1016/j.fuproc.2018.03.023 (DOI)
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-06-09Bibliographically approved
Holmgren, P., Broström, M. & Backman, R. (2018). Slag Formation during Entrained Flow Gasification: Silicon Rich Grass Fuel with KHCO3 Additive. Energy & Fuels
Open this publication in new window or tab >>Slag Formation during Entrained Flow Gasification: Silicon Rich Grass Fuel with KHCO3 Additive
2018 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029Article in journal (Refereed) Epub ahead of print
Abstract [en]

Prediction of ash particle adherence to walls, melting, and flow properties are important for successful operation of slagging entrained flow gasifiers. In the present study, silicon-rich reed canary grass was gasified at 1000 and 1200 °C with solid KHCO3 added at 0, 1, or 5 wt % to evaluate the impact and efficiency of the dry mixed additive on slag properties. The fuel particles collided with an angled flat impact probe inside the hot reactor, constructed to allow for particle image velocimetry close to the surface of the probe. Ash deposit layer buildup was studied in situ as well as ash particle shape, size, and velocity as they impacted on the probe surface. The ash deposits were analyzed using scanning electron microscopy–energy-dispersive X-ray spectroscopy, giving detailed information on morphology and elemental composition. Results were compared to thermodynamic equilibrium calculations for phase composition and viscosity. The experimental observations (slag melting, flow properties, and composition) were in good qualitative agreement with the theoretical predictions. Accordingly, at 1000 °C, no or partial melts were observed depending upon the potassium/silicon ratio; instead, high amounts of additive and a temperature of at least 1200 °C were needed to create a flowing melt.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Energy Engineering Other Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-151688 (URN)10.1021/acs.energyfuels.8b02545 (DOI)2-s2.0-85053900505 (Scopus ID)
Available from: 2018-09-10 Created: 2018-09-10 Last updated: 2018-10-04
Boström, D., Skoglund, N., Boman, C., Öhman, M., Broström, M. & Backman, R. (2017). Ash transformation chemistry during combustion of biomass, theory and technical applications. Paper presented at 254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, AUG 20-24, 2017, Washington, DC. Abstract of Papers of the American Chemical Society, 254
Open this publication in new window or tab >>Ash transformation chemistry during combustion of biomass, theory and technical applications
Show others...
2017 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-147225 (URN)000429525604122 ()
Conference
254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, AUG 20-24, 2017, Washington, DC
Note

Meeting Abstract: 23

Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2018-06-09Bibliographically approved
Boman, C., Öhman, M., Broström, M., Skoglund, N., Schmidt, F. M., Backman, R. & Boström, D. (2017). Ash transformation chemistry in biomass fixed beds with focus on slagging and aerosols: 20 years of research and new developments. Paper presented at 254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, AUG 20-24, 2017, Washington, DC. Abstract of Papers of the American Chemical Society, 254
Open this publication in new window or tab >>Ash transformation chemistry in biomass fixed beds with focus on slagging and aerosols: 20 years of research and new developments
Show others...
2017 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254Article in journal, Meeting abstract (Other academic) Published
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-148191 (URN)
Conference
254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, AUG 20-24, 2017, Washington, DC
Note

Meeting Abstract: 24

Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2018-06-09
Strandberg, A., Thyrel, M., Rudolfsson, M., Lestander, T. A., Backman, R., Skoglund, N. & Broström, M. (2017). Char conversion characterizedby synchrotron based X-ray micro-tomograhy and SEM-EDS analysis. In: EUBCE 2017 – 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden: . Paper presented at EUBCE 2017 – 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden.
Open this publication in new window or tab >>Char conversion characterizedby synchrotron based X-ray micro-tomograhy and SEM-EDS analysis
Show others...
2017 (English)In: EUBCE 2017 – 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden, 2017Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Fuel and ash properties were studied during fuel conversion by careful examination of char samples at different degrees of char oxidation. Two types of lignocellulosic pellets with different compositions of ash forming elements were used: poplar and straw from wheat. The charred pellets were investigated by synchrotron-based X-ray micro-tomography to create 3D images of the development of cracks, internal cavities, and ash layers during conversion.  Furthermore, SEM-EDS was used to for detailed chemical and morphological information of the ash layers formed. The pore development during pellet conversion was found to deviate from what has previously been described for the structure of solid wood particles. Large cracks and internal cavities were formed extensively already during devolatilization. For poplar, no mobility of the ash forming elements were observed as the burnout proceeded. Ash layer properties varied between the two fuels: poplar formed a porous, permeable, low density and Ca rich ash, whereas wheat straw ash accumulated on the surface in the form of high density melt that develop into bubbles on the surface. As the conversion proceeded, the ash layer covered more of the active char surface area, but without totally blocking the gas transport.

Keywords
chemical composition, pellet, thermochemical conversion, wheat straw, poplar
National Category
Energy Engineering Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-136274 (URN)10.5071/25thEUBCE2017-2BO.14.5 (DOI)978-88-89407-17-2 (ISBN)
Conference
EUBCE 2017 – 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden
Funder
Bio4Energy
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2018-06-09
Holmgren, P., Broström, M. & Backman, R. (2017). Slag formation during entrained flow gasification. Part 1: Calcium rich bark fuel. In: Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden: . Paper presented at Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden. Stockholm, Sweden
Open this publication in new window or tab >>Slag formation during entrained flow gasification. Part 1: Calcium rich bark fuel
2017 (English)In: Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden, Stockholm, Sweden, 2017Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Stockholm, Sweden: , 2017
National Category
Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-146668 (URN)
Conference
Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden
Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2018-06-09
Holmgren, P., Broström, M. & Backman, R. (2017). Slag formation during entrained flow gasification. Part 2: Silicon rich grass fuel with KHCO3 additive. In: Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden: . Paper presented at Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden.
Open this publication in new window or tab >>Slag formation during entrained flow gasification. Part 2: Silicon rich grass fuel with KHCO3 additive
2017 (English)In: Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden, 2017Conference paper, Published paper (Other academic)
National Category
Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-146669 (URN)
Conference
Nordic Flame Days 2017 – 10th – 11th of October, Stockholm, Sweden
Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2018-06-09
Ma, C., Carlborg, M., Hedman, H., Wennebro, J., Weiland, F., Wiinikka, H., . . . Ohman, 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
Show others...
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 kW(th), 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
Bioenergy
Identifiers
urn:nbn:se:umu:diva-130239 (URN)10.1021/acs.energyfuels.6b02222 (DOI)000390072900057 ()
Available from: 2017-01-16 Created: 2017-01-14 Last updated: 2018-10-17Bibliographically approved
Kramb, J., Konttinen, J., Backman, R., Salo, K. & Roberts, M. (2016). Elimination of arsenic-containing emissions from gasification of chromated copper arsenate wood. Fuel, 181, 319-324
Open this publication in new window or tab >>Elimination of arsenic-containing emissions from gasification of chromated copper arsenate wood
Show others...
2016 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 181, p. 319-324Article in journal (Refereed) Published
Abstract [en]

The behavior of arsenic in chromated copper arsenate containing wood during gasification was modeled using thermodynamic equilibrium calculations. The results of the model were validated using bench-scale gasification tests. It is shown that over 99.6% of arsenic can be removed from the product gas by a hot filter when the gas is cooled below the predicted condensation temperature.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Gasification, Arsenic, CCA wood, Equilibrium modeling
National Category
Energy Engineering Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-127241 (URN)10.1016/j.fuel.2016.04.109 (DOI)000377328700029 ()
Available from: 2016-11-14 Created: 2016-11-03 Last updated: 2018-06-09Bibliographically approved
He, H., Ji, X., Boström, D., Backman, R. & Öhman, M. (2016). Mechanism of Quartz Bed Particle Layer Formation in Fluidized Bed Combustion of Wood-Derived Fuels. Energy & Fuels, 30(3), 2227-2232
Open this publication in new window or tab >>Mechanism of Quartz Bed Particle Layer Formation in Fluidized Bed Combustion of Wood-Derived Fuels
Show others...
2016 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 3, p. 2227-2232Article in journal (Refereed) Published
Abstract [en]

Agglomeration is among one of the major problems in the operation of fluidized bed boilers. The formation of bed particle layers is thought to play an important role on the occurrence of agglomeration in wood-fired fluidized (quartz) beds. In spite of frequent experimental reports on the quartz bed particle layer characteristics, the underlying bed layer formation process has not yet been presented. By combining our previously experimental results on layer characteristics for samples with durations from 4 h to 23 days, with phase diagrams, thermochemical equilibrium calculations, and a diffusion model, a mechanism of quartz bed particle layer formation was proposed. For younger bed particles (<around 1 day), the layer growth process is accelerated due to a high diffusion of calcium in a K-rich silicate melt. However, with continuous addition of calcium into the layer, the amount of melt decreases and crystalline Ca-silicates starts to form. Ca2SiO4 is the dominating crystalline phase in the inner layer, while the formation of CaSiO3 and possibly Ca3SiO5 are favored for younger and older bed particles, respectively. The decreasing amount of melt and formation of crystalline phases result in low diffusion rates of calcium in the inner layer and the layer growth process becomes diffusion controlled after around 1 day.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-119290 (URN)10.1021/acs.energyfuels.5b02891 (DOI)000372562800078 ()
Available from: 2016-04-20 Created: 2016-04-15 Last updated: 2018-06-07Bibliographically approved
Organisations

Search in DiVA

Show all publications