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Holmgren, Per
Publications (10 of 17) Show all publications
Broström, M., Holmgren, P. & Backman, R. (2018). Ash fractionation and slag formation during entrained flow biomass gasification. In: : . Paper presented at The 27th International Conference on the Impacts of Fuel Quality on Power Production and the Environment, Lake Louise, Alberta, Canada, September 24-28 2018..
Open this publication in new window or tab >>Ash fractionation and slag formation during entrained flow biomass gasification
2018 (English)Conference paper, Oral presentation only (Other academic)
National Category
Chemical Engineering Bioenergy
Identifiers
urn:nbn:se:umu:diva-152042 (URN)
Conference
The 27th International Conference on the Impacts of Fuel Quality on Power Production and the Environment, Lake Louise, Alberta, Canada, September 24-28 2018.
Available from: 2018-09-25 Created: 2018-09-25 Last updated: 2018-11-22Bibliographically approved
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
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-147729 (URN)10.1063/1.5030603 (DOI)000437195200054 ()29960572 (PubMedID)2-s2.0-85048128383 (Scopus ID)
Projects
Bio4Energy
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2019-09-02Bibliographically 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
New York: Elsevier, 2018
Keywords
Tunable diode laser absorption spectroscopy (TDLAS), Atomic potassium, Entrained flow reactor, Biomass combustion, Thermodynamic equilibrium calculations, Computational fluid dynamics (CFD)
National Category
Atom and Molecular Physics and Optics Chemical Process Engineering Inorganic Chemistry
Identifiers
urn:nbn:se:umu:diva-141456 (URN)10.1016/j.combustflame.2017.10.013 (DOI)000424859100040 ()
Projects
Bio4Energy
Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2019-09-02Bibliographically approved
Holmgren, P. (2018). Entrained flow studies on biomass fuel powder conversion and ash formation. (Doctoral dissertation). Umeå: Umeå University
Open this publication in new window or tab >>Entrained flow studies on biomass fuel powder conversion and ash formation
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Partikelomvandling och askbildning i pulverflammor
Abstract [en]

Reducing the global dependence on fossil fuels is of paramount importance in tackling the environmental challenges we face, not only tomorrow, but already today. Biomass offers a renewable supply of CO2-neutral raw material that can be converted into many different forms of fuels and valuable chemicals, making it a prime candidate for the technologies of tomorrow. However, the heterogeneous nature and distinctly different elemental composition of biomass compared to traditional fossil sources present new challenges to be solved. When it comes to thermochemical technologies, key issues concern fuel conversion efficiency, ash formation, ash/fuel interactions and ash/reactor material interactions.

The objective of the present thesis was to provide new knowledge and insights into thermochemical fuel conversion, in particular its application in entrained flow technologies. A laboratory-scale reactor was constructed, evaluated and was used to study several aspects of high-temperature entrained flow biomass fuel conversion. Pulverized fuel particles from different biomass sources were used, and their physical and chemical interactions with the surrounding atmosphere, the concurrent ash element release, ash formation, and phase interactions were also studied in detail. In addition to the entrained flow reactor designed and constructed for this purpose, the main method for data collection was in situ optical studies of converting particles, either while entrained in the flow or when impacting upon surfaces. Elemental composition analysis of collected samples and gas analysis were also performed, allowing for a deeper understanding of ash element fractionation and interactions and thus explaining the observed properties of the resulting deposits or slag.

The degree of conversion of fuels with very low ash content, such as stem wood, was well described and modeled by a novel method using optical data, offering a non-intrusive and non-destructive alternative to traditional techniques. Coupling computational fluid dynamics with optical data allowed for improved experimental data interpretation and provided improved accuracy for fuel particle residence time estimations, which is an important parameter when studying fast chemical reactions such as those taking place in reactors for entrained flow conditions. The results from studies on ash formation gave new insights into the feasibility of using dry-mixed K-rich additives for improving slag properties during gasification of Ca-rich and Si-rich fuels. Interpretations of the experimental results were supported by thermodynamic equilibrium calculations, and the conclusions highlight both possibilities and challenges in gasification with high fuel flexibility while at the same time producing a flowing slag. Applications and future implications are discussed, and new topics of interest are presented.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2018. p. 63
Keywords
Thermochemical biomass conversion, particle image velocimetry, gasification, entrained flow reactor, ash transformation, equilibrium calculations, slag formation
National Category
Inorganic Chemistry Chemical Engineering Energy Engineering
Identifiers
urn:nbn:se:umu:diva-152332 (URN)978-91-7601-937-5 (ISBN)
Public defence
2018-10-26, N430, Naturvetarhuset, Umeå, 10:00 (English)
Opponent
Supervisors
Funder
Bio4EnergySwedish Research CouncilSwedish Energy Agency
Available from: 2018-10-05 Created: 2018-10-02 Last updated: 2018-10-18Bibliographically approved
Holmgren, P., Broström, M. & Backman, R. (2018). Slag Formation during Entrained Flow Gasification: Silicon Rich Grass Fuel with KHCO3 Additive. Energy & Fuels, 32(10), 10720-10726
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 1520-5029, Vol. 32, no 10, p. 10720-10726Article in journal (Refereed) Published
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)000448087000068 ()2-s2.0-85053900505 (Scopus ID)
Projects
Bio4Energy
Available from: 2018-09-10 Created: 2018-09-10 Last updated: 2019-08-30Bibliographically approved
Strandberg, A., Holmgren, P., Wagner, D. R., Molinder, R., Wiinikka, H., Umeki, K. & Broström, M. (2017). Effects of pyrolysis conditions and ash formation on gasification rates of biomass char. Energy & Fuels, 31(6), 6507-6514
Open this publication in new window or tab >>Effects of pyrolysis conditions and ash formation on gasification rates of biomass char
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2017 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 6, p. 6507-6514Article in journal (Refereed) Published
Abstract [en]

Pyrolysis conditions and the presence of ash-forming elements significantly influence char properties and its oxidation or gasification reactivity. In this study, intrinsic gasification rates of char from high heating rate pyrolysis were analyzed with isothermal thermogravimetry. The char particles were prepared from two biomasses at three size ranges and at two temperatures. Reactivity dependence on original particle size was found only for small wood particles that had higher intrinsic char gasification rates. Pyrolysis temperature had no significant effect on char reactivity within the range tested. Observations of ash formation highlighted that reactivity was influenced by the presence of ash-forming elements, not only at the active char sites but also through prohibition of contact between char and gasification agent by ash layer formation with properties highly depending on ash composition.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-136565 (URN)10.1021/acs.energyfuels.7b00688 (DOI)000404691900079 ()
Projects
Bio4Energy
Available from: 2017-06-19 Created: 2017-06-19 Last updated: 2019-09-06Bibliographically approved
Qu, Z., Holmgren, P., Skoglund, N., Wagner, D. R., Broström, M. & Schmidt, F. M. (2017). Investigation of H2O, temperature and potassium in entrained flow biomass combustion – coupling in situ TDLAS with modelling. In: Nordic Flame Days 2017, 10-11 October, Stockholm: . Paper presented at Nordic Flame Days 2017, 10-11 October, Stockholm.
Open this publication in new window or tab >>Investigation of H2O, temperature and potassium in entrained flow biomass combustion – coupling in situ TDLAS with modelling
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2017 (English)In: Nordic Flame Days 2017, 10-11 October, Stockholm, 2017Conference paper, Oral presentation with published abstract (Refereed)
National Category
Atom and Molecular Physics and Optics Chemical Process Engineering Inorganic Chemistry
Identifiers
urn:nbn:se:umu:diva-141520 (URN)
Conference
Nordic Flame Days 2017, 10-11 October, Stockholm
Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2018-06-09
Strandberg, A., Holmgren, P. & Broström, M. (2017). Predicting fuel properties of biomass using thermogravimetry and multivariate data analysis. Fuel processing technology, 156, 107-112
Open this publication in new window or tab >>Predicting fuel properties of biomass using thermogravimetry and multivariate data analysis
2017 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 156, p. 107-112Article in journal (Refereed) Published
Abstract [en]

Simple and reliable characterization methods for determining fuel properties of biomass are needed for several different applications. This paper describes and demonstrates such a method combining thermogravimetric analysis with multivariate data analysis, based on the thermal decomposition behavior of the fuel. Materials used for the tests were milled samples of wood chips thermally pretreated under different conditions in a torrefaction pilot plant. The predictions using the multivariate model were compared to those from a conventional curve deconvolution approach. The multivariate approach showed better and more flexible performance, with error of prediction of 2.7% for Mass Yield prediction, compared to the reference method that resulted in 29.4% error. This multivariate method could handle samples pretreated under more severe conditions compared to the curve deconvolution methods. Elemental composition, heating value and volatile content were also predicted with even higher accuracies. The results highlight the usefulness of the method and also the importance of using calibration data of good quality. (C) 2016 Elsevier B.V. All rights reserved.

Keywords
Thermogravimetric analysis, Multivariate data analysis, Fuel characterization, Fuel composition, Torrefaction
National Category
Bioenergy Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-130216 (URN)10.1016/j.fuproc.2016.10.021 (DOI)000390078200014 ()
Available from: 2017-02-02 Created: 2017-01-14 Last updated: 2018-06-09Bibliographically approved
Holmgren, P., Wagner, D. R., Strandberg, A., Molinder, R., Wiinikka, H., Umeki, K. & Broström, M. (2017). Size, shape, and density changes of biomass particles during rapid devolatilization. Fuel, 206, 342-351
Open this publication in new window or tab >>Size, shape, and density changes of biomass particles during rapid devolatilization
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2017 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, p. 342-351Article in journal (Refereed) Published
Abstract [en]

Particle properties such as size, shape and density play significant roles on particle flow and flame propagationin pulverized fuel combustion and gasification. A drop tube furnace allows for experiments athigh heating rates similar to those found in large-scale appliances, and was used in this study to carryout experiments on pulverized biomass devolatilization, i.e. detailing the first stage of fuel conversion.The objective of this study was to develop a particle conversion model based on optical informationon particle size and shape transformation. Pine stem wood and wheat straw were milled and sieved tothree narrow size ranges, rapidly heated in a drop tube setup, and solid residues were characterized usingoptical methods. Different shape descriptors were evaluated and a shape descriptor based on particleperimeter was found to give significant information for accurate estimation of particle volume. The opticalconversion model developed was proven useful and showed good agreement with conversion measuredusing a reference method based on chemical analysis of non-volatilized ash forming elements.The particle conversion model presented can be implemented as a non-intrusive method for in-situ monitoringof particle conversion, provided density data has been calibrated.

Keywords
PIV, DTR, Pyrolysis, Biomass conversion
National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-136564 (URN)10.1016/j.fuel.2017.06.009 (DOI)000405805800035 ()
Projects
Bio4Energy
Available from: 2017-06-19 Created: 2017-06-19 Last updated: 2019-09-06Bibliographically approved
Holmgren, P., Broström, M. & Backman, R. (2017). Slag formation during entrained flow gasification. Part 1: Calcium rich bark fuel. In: : . Paper presented at Nordic Flame Days 2017, Stockholm, Sweden, October 10-11, 2017. Stockholm, Sweden
Open this publication in new window or tab >>Slag formation during entrained flow gasification. Part 1: Calcium rich bark fuel
2017 (English)Conference paper, Oral presentation only (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, Stockholm, Sweden, October 10-11, 2017
Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2019-06-25Bibliographically approved
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