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  • 1.
    Holmgren, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Strandberg, Anna
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wagner, David R.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Molinder, Roger
    Energitekniskt Centrum, Piteå.
    Wiinikka, Henrik
    Energitekniskt Centrum, Piteå.
    Umeki, Kentaro
    Luleå Technical University.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Size, Shape and Density Changes of Biomass Particles during Devolatilization in a Drop Tube Furnace2014In: Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 2.
    Holmgren, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wagner, David R.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Strandberg, Anna
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Molinder, Roger
    Wiinikka, Henrik
    Umeki, Kentaro
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Size, shape, and density changes of biomass particles during rapid devolatilization2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 206, p. 342-351Article in journal (Refereed)
    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.

  • 3.
    Qu, Zhechao
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Energy Engineering, Department of Engineering Sciences & Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden.
    Wagner, David R.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Distribution of temperature, H2O and atomic potassium during entrained flow biomass combustion: coupling in situ TDLAS with modeling approaches and ash chemistry2018In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 188, p. 488-497Article in journal (Refereed)
    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.

  • 4.
    Qu, Zhechao
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Skoglund, Nils
    Wagner, David R.
    Broström, Markus
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Investigation of H2O, temperature and potassium in entrained flow biomass combustion – coupling in situ TDLAS with modelling2017In: Nordic Flame Days 2017, 10-11 October, Stockholm, 2017Conference paper (Refereed)
  • 5.
    Qu, Zhechao
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wagner, David R.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    TDLAS-based in situ detection of atomic potassium during combustion of biomass in an entrained flow reactor2016Conference paper (Other academic)
  • 6.
    Strandberg, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wagner, David R.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Molinder, Roger
    Wiinikka, Henrik
    Umeki, Kentaro
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effects of pyrolysis conditions and ash formation on gasification rates of biomass char2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 6, p. 6507-6514Article in journal (Refereed)
    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.

  • 7.
    Strandberg, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wagner, David R.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Molinder, Roger
    Energitekniskt Centrum, Piteå.
    Wiinikka, Henrik
    Energitekniskt Centrum, Piteå.
    Umeki, Kentaro
    Luleå Technical University.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Influence of Biomass Particle Properties and Pyrolysis Conditions on Char Reactivity2014In: Proceedings of Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 8.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    The effect of particle size, temperature, and residence time on biomass devolatilization behavior in a wire-mesh reactor2014In: Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 9.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Time-dependent variations of activation energy during rapid devolatilization of biomass2016In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 118, p. 98-104Article in journal (Refereed)
    Abstract [en]

    Industrial gasifiers and combustors are assumed to reach particle heating rates of 10(5)-10(6) degrees C/s and understanding how particles behave in these extreme conditions can improve the utilization of solid fuels in these reactors and in downstream applications. By studying intermediate devolatilization processes during solid fuel pyrolysis, detailed models for solid fuel conversion can be formulated. Key objectives of this study included (1) investigate possible mechanisms that promote the formation of synthesis gas components and char, (2) compare the devolatilization behavior of pyrolysis by varying particle size, hold time, and temperature and (3) correlate char deactivation with hold time. The objectives of the study were accomplished using a wire-mesh reactor with a uniform heating rate of 500 degrees C/s in nitrogen under atmospheric pressure. A design of experiments approach was used to quantify the effects that hold time, temperature, and particle size had on char yield, evolved gas composition, and apparent activation energy of pine stem wood and wheat straw. Key results indicate that with increased temperature and hold time more volatiles evolve from the fuels and favor carbon monoxide and methane production at higher temperatures. Apparent activation energy of the volatile matter decreases with hold time. An abbreviated model for apparent activation energy correlates well with experimental data and assumes that along a devolatilization pathway, that not all volatiles are driven from the fuel.

  • 10.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Department of Chemical and Materials Engineering, San Jose State University, One Washington Square, San Jose, California, USA.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 6, article id 065101Article in journal (Refereed)
    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.

  • 11.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Strandberg, Anna
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiinikka, Henrik
    Energitekniskt Centrum, Piteå.
    Molinder, Roger
    Energitekniskt Centrum, Piteå.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fate of Inorganic Species during Biomass Devolatilization in a Drop Tube Furnace2014In: Impacts of Fuel Quality on Power Production October 26–31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 12.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Zhechao, Qu
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Florian, Schmidt
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Validation of reacting flow models via tunable diode laser absorption spectroscopy2014In: Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
1 - 12 of 12
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