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  • 1.
    Gersen, Sander
    et al.
    DNV-GL Oil and Gas, The Netherlands.
    Van Essen, Martijn
    DNV-GL Oil and Gas, The Netherlands.
    Visser, Pieter
    DNV-GL Oil and Gas, The Netherlands.
    Ahmad, Mohammad
    DNV-GL Oil and Gas, The Netherlands.
    Mokhov, Anatoli V.
    University of Groningen, The Netherlands.
    Sepman, Alexey
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Alberts, Ramon
    Hanze University Groningen, The Netherlands.
    Duoma, Arno
    University Groningen, The Netherlands.
    Levinsky, Howard B.
    DNV-GL Oil and Gas, The Netherlands; University Groningen, The Netherlands.
    Detection of H2S, So2 and NO2 in CO2 at pressures ranging from 1- 40 bar by using broadband absorption spectroscopy in the UV/VIS range2014In: Energy Procedia, 2014, Vol. 63, p. 2570-2582Conference paper (Refereed)
    Abstract [en]

    This paper presents a methodology to quantitatively measure H2S, So2 and NO2 fractions in gaseous CO2 by using broadband absorption spectroscopy at 1 and 40 bar. The mole fractions of binary- And 3-component mixtures of H2S, So2 and NO2 in CO2 with known fractions ranging from 35-250 ppm are successfully derived from the measured absorption spectra. The difference between the fitted and experimental mole fractions is less than 10% for all studied mixtures. The results successfully demonstrate that low fractions of H2S, So2 and NO2 in gaseous CO2 can be accurately measured at pipeline conditions by using broad band absorption spectroscopy.

  • 2.
    Likitha, S. S.
    et al.
    Luleå Uniersity of Technology, Sweden.
    Westerberg, L. G.
    Luleå Uniersity of Technology, Sweden.
    Akerstedt, H. O.
    Luleå Uniersity of Technology, Sweden.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Sepman, Alexey
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Modelling of heat flow and electromagnetic phenomena in a non transferred plasma torch2021In: 47th EPS Conference on Plasma Physics, EPS 2021, European Physical Society (EPS) , 2021, p. 1088-1091Conference paper (Refereed)
    Abstract [en]

    Over the decades, computational methods have been used to model and describe the flow and ionization dynamics in plasma torches. However, the impact of the operational parameters such as gas flow rate, swirl number and input current density on flow is still inexplicit. In this study, the flow in a non-transferred plasma torch is modelled using COMSOL Multiphysics, and the influence of these parameters is studied. The analysis is carried out on an axisymmetric geometry with the conical-shaped cathode, nozzle-shaped anode, and Argon is used as the plasma gas. A thermal plasma (equilibrium discharges) is considered, i.e., the plasma is under partial to complete local thermodynamic equilibrium in which the magnetohydrodynamic (MHD) equations are solved. This is treated in the Equilibrium Discharge Interface in COMSOL’s plasma module that has been used in the present study. The laminar flow analysis is performed for low-velocity cases and turbulent flow analysis for higher velocities. It was found that the velocity increase across the plasma arc due to ionization and gas expansion, could be observed only for sufficiently high plasma inflow velocities. The position of the plasma arc is determined for different operating conditions. It was further found that the velocity has a negligible effect on the length of the plasma arc, whereas the dependency of the arc length and attachment point on the anode wall, to the input current density and cathode tip temperature is well explained. The paper concludes by presenting the variations in temperature and velocity of plasma arc due to swirling inflow

  • 3.
    Mousavi, S. M.
    et al.
    Lund University, Sweden.
    Thorin, E.
    Umeå University, Sweden.
    Schmidt, F. M.
    Umeå University, Sweden.
    Sepman, Alexey
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Bai, X S
    Lund University, Sweden.
    Fatehi, H
    Lund University, Sweden.
    Numerical Study and Experimental Verification of Biomass Conversion and Potassium Release in a 140 kW Entrained Flow Gasifier2023In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 37, no 2, p. 1116-1130Article in journal (Refereed)
    Abstract [en]

    In this study, a Eulerian-Lagrangian model is used to study biomass gasification and release of potassium species in a 140 kW atmospheric entrained flow gasifier (EFG). Experimental measurements of water concentration and temperature inside the reactor, together with the gas composition at the gasifier outlet, are used to validate the model. For the first time, a detailed K-release model is used to predict the concentrations of gas-phase K species inside the gasifier, and the results are compared with experimental measurements from an optical port in the EFG. The prediction errors for atomic potassium (K), potassium chloride (KCl), potassium hydroxide (KOH), and total potassium are 1.4%, 9.8%, 5.5%, and 5.7%, respectively, which are within the uncertainty limits of the measurements. The numerical model is used to identify and study the main phenomena that occur in different zones of the gasifier. Five zones are identified in which drying, pyrolysis, combustion, recirculation, and gasification are active. The model was then used to study the transformation and release of different K species from biomass particles. It was found that, for the forest residue fuel that was used in the present study, the organic part of K is released at the shortest residence time, followed by the release of inorganic K at higher residence times. The release of inorganic salts starts by evaporation of KCl and continues by dissociation of K2CO3 and K2SO4, which forms gas-phase KOH. The major fraction of K is released around the combustion zone (around 0.7-1.3 m downstream of the inlet) due to the high H2O concentration and temperature. These conditions lead to rapid dissociation of K2CO3 and K2SO4, which increases the total K concentration from 336 to 510 ppm in the combustion zone. The dissociation of the inorganic salts and KOH formation continues in the gasification zone at a lower rate; hence, the total K concentration slowly increases from 510 ppm at 1.3 m to 561 ppm at the outlet. © 2023 The Authors. 

  • 4.
    Sepman, Alexey
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Fredriksson, Christian
    LKAB, Sweden.
    Ögren, Yngve
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Laser-Based, Optical, and Traditional Diagnostics of NO and Temperature in 400 kW Pilot-Scale Furnace2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 15, article id 7048Article in journal (Refereed)
    Abstract [en]

    A fast sensor for simultaneous high temperature (above 800 K) diagnostics of nitrogen oxide (NO) concentration and gas temperature (T) based on the spectral fitting of low-resolution NO UV absorption near 226 nm was applied in pilot-scale LKAB’s Experimental Combustion Furnace (ECF). The experiments were performed in plasma and/or fuel preheated air at temperatures up to 1550 K, which is about 200 K higher than the maximal temperature used for the validation of the developed UV NO sensor previously. The UV absorption NO and T measurements are compared with NO probe and temperature measurements via suction pyrometry and tuneable diode laser absorption (TDL) using H2O transitions at 1398 nm, respectively. The agreement between the NO UV and NO probe measurements was better than 15%. There is also a good agreement between the temperatures obtained using laser-based, optical, and suction pyrometer measurements. Comparison of the TDL H2O measurements with the calculated H2O concentrations demonstrated an excellent agreement and confirms the accuracy of TDL H2O measurements (better than 10%). The ability of the optical and laser techniques to resolve various variations in the process parameters is demonstrated.

  • 5.
    Sepman, Alexey
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Gullberg, Marcus
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Measuring NO and temperature in plasma preheated air using UV absorption spectroscopy2020In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 126, no 6, article id 100Article in journal (Refereed)
    Abstract [en]

    A new fast sensor for simultaneous high temperature diagnostics (above 800 K) of nitrogen oxide (NO) concentration and gas temperature (T) was developed based on the spectral fitting of low-resolution NO UV absorption near 226 nm. The sensor was intended for process control in future low-carbon footprint heavy process industries using renewable powered electro fuels (e.g. H2, NH3) or plasma torches as heat source. Due to excitation of molecular vibration, the shape of the selected NO feature, including (0, 0), (1, 1), and (2, 2) vibrational transitions of the A2Σ+ − X2Π2 electronic system had a strong temperature sensitivity at temperatures above 800 K. The fitting was made using the well-known NO molecular constants of the A2Σ+ − X2Π2 electronic system. To reduce the computational time, a library of the molecular spectra calculated at different temperatures was created. The fitting of an experimental spectrum representing the convolution of the instrument line function of the spectrometer with the molecular spectra was performed using the pre-calculated library spectra. Based on comparison with conventional measurement methods, the accuracy of the developed sensor was within 15% for NO and about 40 K for T, clearly showing the potential for fast in situ diagnostics in hot process gases. © 2020, The Author(s).

  • 6.
    Sepman, Alexey
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Malhotra, Jaskaran Singh
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy. DTU Technical University of Denmark, Denmark.
    Wennebro, Jonas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Iron as recyclable electrofuel: Effect on particle morphology from multiple combustion-regeneration cycles2024In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 259, article id 113137Article in journal (Refereed)
    Abstract [en]

    This work describes the morphological and material changes in the iron powder during four regeneration-combustion cycles. The regeneration in H2 and combustion in air experiments were made in a fluidized bed (FB) and an entrained flow reactor (EFR), respectively. The average size of the iron oxide particles more than doubled between the first and fourth combustion cycles, and many of the particles were hollow. The regeneration step did not change the size of the particles but increased their porosity. A mechanism is proposed that describes the formation of large-diameter hollow particles which increases as a function of the regeneration-combustion cycles. The observed increase in particle size and the change in particle morphology complicates the iron fuel concept, as it leads to a degradation of the structural stability of the particle with time.

  • 7.
    Sepman, Alexey
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Thorin, Emil
    Umeå University, Sweden.
    Ögren, Yngve
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Ma, Charlie
    Umeå University, Sweden.
    Carlborg, Markus
    Umeå University, Sweden.
    Wennebro, Jonas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Broström, Markus
    Umeå University, Sweden.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy. Luleå University of Technology, Sweden.
    Schmidt, Florian
    Umeå University, Sweden.
    Laser-based detection of methane and soot during entrained-flow biomass gasification2022In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 237, article id 111886Article in journal (Refereed)
    Abstract [en]

    Methane is one of the main gas species produced during biomass gasification and may be a desired or undesired product. Syngas CH4 concentrations are typically >5 vol-% (when desired) and 1–3 vol-% even when efforts are made to minimize it, while thermochemical equilibrium calculations (TEC) predict complete CH4 decomposition. How CH4 is generated and sustained in the reactor core is not well understood. To investigate this, accurate quantification of the CH4 concentration during the process is a necessary first step. We present results from rapid in situ measurements of CH4, soot volume fraction, H2O and gas temperature in the reactor core of an atmospheric entrained-flow biomass gasifier, obtained using tunable diode laser absorption spectroscopy (TDLAS) in the near-infrared (1.4 µm) and mid-infrared (3.1 µm) region. An 80/20 wt% mixture of forest residues and wheat straw was converted using oxygen-enriched air (O2>21 vol%) as oxidizer, while the global air-fuel equivalence ratio (AFR) was set to values between 0.3 and 0.7. Combustion at AFR 1.3 was performed as a reference. The results show that the CH4 concentration increased from 1 to 3 vol-% with decreasing AFR, and strongly correlated with soot production. In general, the TDLAS measurements are in good agreement with extractive diagnostics at the reactor outlet and TEC under fuel-lean conditions, but deviate significantly for lower AFR. Detailed 0D chemical reaction kinetics simulations suggest that the CH4 produced in the upper part of the reactor at temperatures >1700 K was fully decomposed, while the CH4 in the final syngas originated from the pyrolysis of fuel particles at temperatures below 1400 K in the lower section of the reactor core. It is shown that the process efficiency was significantly reduced due to the C and H atoms bound in methane and soot. © 2021 The Authors

  • 8.
    Sepman, Alexey
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Ögren, Yngve
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center. Luleå University of Technology, Sweden.
    Gullberg, Marcus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center. Luleå University of Technology, Sweden.
    Development of TDLAS sensor for diagnostics of CO, H2O and soot concentrations in reactor core of pilot-scale gasifier2016In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 122, no 2, p. 1-12, article id 29Article in journal (Refereed)
    Abstract [en]

    This paper reports on the development of the tunable diode laser absorption spectroscopy sensor near 4350 cm−1 (2298 nm) for measurements of CO and H2O mole fractions and soot volume fraction under gasification conditions. Due to careful selection of the molecular transitions [CO (υ″ = 0 → υ′ = 2) R34–R36 and H2O at 4349.337 cm−1], a very weak (negligible) sensitivity of the measured species mole fractions to the temperature distribution inside the high-temperature zone (1000 K < T < 1900 K) of the gasification process is achieved. The selected transitions are covered by the tuning range of single diode laser. The CO and H2O concentrations measured in flat flames generally agree better than 10 % with the results of 1-D flame simulations. Calibration-free absorption measurements of studied species in the reactor core of atmospheric pilot-scale entrained-flow gasifier operated at 0.1 MW power are reported. Soot concentration is determined from the measured broadband transmittance. The estimated uncertainties in the reactor core CO and H2O measurements are 15 and 20 %, respectively. The reactor core average path CO mole fractions are in quantitative agreement with the µGC CO concentrations sampled at the gasifier output.

  • 9.
    Sepman, Alexey
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Qu, Zhechao
    Umeå University, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Schmidt, Florian M.
    Umeå University, Sweden.
    Real-time in situ multi-parameter TDLAS sensing in the reactor core of an entrained-flow biomass gasifier2017In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 36, no 3, p. 4541-4548Article in journal (Refereed)
    Abstract [en]

    Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure several important process parameters at two different locations inside the reactor of an atmospheric air-blown 0.1 MW biomass gasifier. Direct TDLAS at 2298 nm was employed for CO and water calibration-free scanned wavelength modulation spectroscopy at 1398 nm for H2O and gas temperature and direct TDLAS at 770 nm for gaseous elemental potassium K(g) under optically thick conditions which correspond the first in situ measurements of K(g) and temperature in a reactor core and in biomass gasification respectively. Actual average temperatures in the reactor core were significantly higher than the uncorrected thermocouple measurements in the gas stream. The CO concentrations at the lower optical access port were comparable to those obtained by GC at the exhaust. In gasification mode similar H2O values were obtained by the two different TDLAS instruments. The reaction time was faster for peat than for stem wood.

  • 10.
    Sepman, Alexey
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, ETC Energy Technology Center.
    Qu, Zhechau
    Umeå University, Sweden; PTB Physikalisch-Technische Bundesanstalt, Germany.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy, ETC Energy Technology Center.
    Schmidt, Florian
    Umeå University, Sweden.
    Tunable diode laser absorption spectroscopy diagnostics of potassium, carbon monoxide, and soot in oxygen-enriched biomass combustion close to stoichiometry2019In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 33, no 11, p. 11795-11803Article in journal (Refereed)
    Abstract [en]

    Combustion facilities run on pulverized biomass often exhibit fluctuations in fuel feeding and, thus, equivalence ratio and would benefit from fast process control based on optical λ sensors installed in the reactor core. The conversion of softwood powder is investigated in an atmospheric entrained-flow reactor (EFR) operated close to stoichiometry using two different burners (swirl and jet) and three oxygen concentrations (21, 30, and 40%). Tunable diode laser absorption spectroscopy (TDLAS) is used to conduct time-resolved (0.1-1 s) in situ measurements of the gas temperature, carbon monoxide (CO), water vapor (H2O), gaseous atomic potassium [K(g)], and soot volume fraction in the lower part of the reactor core and in the exhaust of the EFR. At both locations, the measurement parameters show significant, correlating fluctuations. The local equivalence ratio is derived from a comparison of measured CO and H2O concentrations (for fuel-rich and fuel-lean conditions, respectively) to thermodynamic equilibrium calculations (TEC) and found to vary in a wide range (0.8-1.3). Soot production decreases with an increasing local equivalence ratio and oxygen enrichment and is lower for the swirl compared to the jet burner. The measured K(g) concentrations follow the general behavior predicted by TEC around stoichiometry. In the relevant temperature range (1100-1700 K), K(g) is 2-4 orders of magnitude higher under fuel-rich than fuel-lean conditions, with a sharp transition at stoichiometry. While K(g) concentrations are lower than TEC in the reactor core and under fuel-rich conditions, excellent agreement is found at the exhaust after complete fuel conversion. Precise, wide dynamic range detection of K(g) using TDLAS enables discrimination between fuel-rich and fuel-lean conditions and has the potential for lambda sensing close to the hot reaction zone of combustion plants.

  • 11.
    Sepman, Alexey
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Ögren, Yngve
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Wennebro, Jonas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Simultaneous diagnostics of fuel moisture content and equivalence ratio during combustion of liquid and solid fuels2022In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 324, article id 119731Article in journal (Refereed)
    Abstract [en]

    The precise control of bio-based combustion is challenging due to the varying composition and moisture content of the fuels, difficulties in achieving stable fuel feeding, and complex underlying thermochemical processes. We present simultaneous online diagnostics of two combustion parameters, the equivalence ratio and fuel moisture content, in a pilot-scale environment. The parameters were evaluated by analysing the H2O and CO2 concentrations. These were measured using a Fourier transform infrared (FTIR) spectrometer (exhaust) and tuneable diode laser (TDL) absorption spectroscopy (combustion chamber) in pilot-scale diesel and pulverized biomass combustion. Liquid H2O was added into the combustion chamber to represent fuel moisture. The equivalence ratio of diesel and wood combustion was varied by adjusting the flows of combustion air in a staged manner or by using rapid periodic variations (on the order of seconds). The moisture fuel levels calculated using the measured fuel and water flow rates (flow method) and the FTIR and TDL H2O and CO2 concentrations agree within 3% (absolute) for both fuels. The TDL and FTIR equivalence ratios agreed quantitatively for both diesel and biomass combustion. However, close to stoichiometry, the TDL values for biomass are up to 15% lower than the FTIR values, indicating ongoing combustion at the location of the TDL measurements. © 2022 The Authors

  • 12.
    Sepman, Alexey
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Optical techniques for characterizing the biomass particle flow fluctuations in lab- and pilot-scale thermochemical systems2017In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 313, p. 129-134Article in journal (Refereed)
    Abstract [en]

    The work demonstrates the performance of the optical extinction technique for real-time diagnostics of the fluctuations in biomass particle flows. The online measurements of fluctuations of density were used to determine the biomass particle mass flow fluctuations. Biomass flows were produced using laboratory biomass particle feeder (mass flux up to 10 g/min) and the hopper-screw feeding system of the pilot-scale entrained flow rector, mass flux up to 500 g/min, located at SP ETC in Piteå. The experiments showed that the time-averaged extinction appeared to be linearly related to the real particle mass flow. The relatively fast variations in biomass feeding rates measured using the extinction technique were confirmed by fast balance measurements (in laboratory feeder experiments) and by real-time tunable diode laser CO and H2O concentrations measured in the reactor core of the entrained flow gasifier.

  • 13.
    Siddanathi, S. L.
    et al.
    Luleå University of Technology, Sweden.
    Westerberg, L. G.
    Luleå University of Technology, Sweden.
    Åkerstedt, H.O.
    Luleå University of Technology, Sweden.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Sepman, Alexey
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Computational modeling and temperature measurements using emission spectroscopy on a non-transferred plasma torch2023In: AIP Advances, E-ISSN 2158-3226, Vol. 13, no 2, article id 025019Article in journal (Refereed)
    Abstract [en]

    A non-transferred plasma torch is a device used to generate a steady thermal plasma jet. Plasma torches have the potential to replace fossil fuel burners used as heat sources in the process industry. Today, however, the available plasma torches are of small scale compared to the power used in the burners in the process industry. In order to understand the effects of large scales on the plasma flow dynamics, it is essential to understand the operation of the plasma torch under different operating conditions and for different geometries. In this study, the analysis of a non-transferred plasma torch has been carried out using both computational and experimental methods. Computationally, the magnetohydrodynamic (MHD) equations are solved using a single-fluid model on a 2D axisymmetric torch geometry. The experiments are performed using emission spectroscopy to measure the plasma jet temperature at the outlet. This paper explains the changes in the arc formation, temperature, and velocity for different working gases and power inputs. Furthermore, the possibilities and disadvantages of the MHD approach, considering a local thermal equilibrium, are discussed. It was found that in general, the computational temperature obtained is supported by the experimental and equilibrium data. The computational temperatures agree by within 10% with the experimental ones at the center of the plasma torch. The paper concludes by explaining the significant impact of input properties like working gas and power input on the output properties like velocity and temperature of plasma jet. © 2023 Author(s).

  • 14.
    Simonsson, Johan
    et al.
    Lund University, Sweden.
    Bladh, Henrik
    Lund University, Sweden.
    Gullberg, Marcus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Pettersson, Esbjörn
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Sepman, Alexey
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Ögren, Yngve
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Bengtsson, Per-Erik
    Lund University, Sweden.
    Soot Concentrations in an Atmospheric Entrained Flow Gasifier with Variations in Fuel and Burner Configuration Studied Using Diode-Laser Extinction Measurements2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 3, p. 2174-2186Article in journal (Refereed)
    Abstract [en]

    Soot concentration measurements were performed using diode-laser extinction in an atmospheric air-blown entrained flow gasifier at two vertical levels. The gasifier was operated at different air-fuel equivalence ratios and with variations in fuel and burner configurations. Two fuels were investigated: wood powder and peat powder. These were burned using two burner configurations, one giving a rotating flow inside the gasifier (swirl), and one where the fuel and air were injected parallel with the gasifier axis (jet). The diode-laser measurements were performed at the wavelength 808 nm from which the soot concentrations were estimated, and additionally at 450 nm in order to gain insight into the spectral dependence of the extinction to estimate measurement quality. Additional diagnostic techniques were used, such as an electrical low-pressure impactor (ELPI) for soot size distributions and gas chromatography for species concentration measurements. The results show that wood powder produces higher soot concentrations than peat powder, especially at lower air-fuel equivalence ratios. Furthermore, the burner configuration had in general much less impact than the choice of fuel on the soot concentration.

  • 15.
    Thorin, Emil
    et al.
    Umeå University, Sweden.
    Sepman, Alexey
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Ögren, Yngve
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Ma, Charlie
    Umeå University, Sweden.
    Carlborg, Markus
    Umeå University, Sweden.
    Wennebro, Jonas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Broström, Markus
    Umeå University, Sweden.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy. Luleå University of Technology, Sweden.
    Schmidt, Florian M
    Umeå University, Sweden.
    Quantitative real-time in situ measurement of gaseous K, KOH and KCl in a 140 kW entrained-flow biomass gasifier2023In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 39, no 1, p. 1337-1345Article in journal (Refereed)
    Abstract [en]

    Photofragmentation tunable diode laser absorption spectroscopy (PF-TDLAS) was used to simultaneously measure the concentrations of gas phase atomic potassium (K), potassium hydroxide (KOH) and potassium chloride (KCl) in the reactor core of a 140 kWth atmospheric entrained-flow gasifier (EFG). In two gasification experiments at air-to-fuel equivalence ratio of 0.5, the EFG was first run on forest residues (FR) and then on an 80/20 mixture of FR and wheat straw (FR/WS). Combustion at air-to-fuel equivalence ratio of 1.3 was investigated for comparison. A high K(g) absorbance was observed in gasification, requiring the photofragmentation signals from KOH(g) and KCl(g) to be recorded at a fixed detuning of 7.3 cm-1 from the center of the K(g) absorption profile. In combustion, the fragments recombined instantly after the UV pulse within around 10 μs, whereas in gasification, the K(g) fragment concentration first increased further for 30 μs after the UV pulse, before slowly decaying for up to hundreds of μs. According to 0D reaction kinetics simulations, this could be explained by a difference in recombination kinetics, which is dominated by oxygen reactions in combustion and by hydrogen reactions in gasification. The K species concentrations in the EFG were stable on average, but periodic short-term variations due to fuel feeding were observed, as well as a gradual increase in KOH(g) over the day as the reactor approached global equilibrium. A comparison of the average K species concentrations towards the end of each experiment showed a higher total K in the gas phase for FR/WS, with higher K(g) and KCl(g), but lower KOH(g), compared to the FR fuel. The measured values were in reasonable agreement with predictions by thermodynamic equilibrium calculations. © 2022 The Author(s). 

  • 16.
    Toth, Pal
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Brackmann, Christian
    Lund University, Sweden.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Mannazhi, Manu
    Lund University, Sweden.
    Simonsson, Johan
    Lund University, Sweden.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Bengtsson, Per Erik
    Lund University, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Experimental and numerical study of biomass fast pyrolysis oil spray combustion: Advanced laser diagnostics and emission spectrometry2019In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 252, p. 125-134Article in journal (Refereed)
    Abstract [en]

    The objective of this work was to move towards developing a comprehensible Computational Fluid Dynamics (CFD) model to facilitate the predictive modeling of Fast Pyrolysis Oil (FPO) spray combustion. A CFD model was implemented from the literature and results were compared to 2D data from non-intrusive optical diagnostics involving Planar Laser Induced Fluorescence of the OH radical, Mie scattering imaging and two-color pyrometry using a laboratory-scale, CH 4 /air flat-flame with an air-assist atomizer. Furthermore, flame radiation and contributions from graybody sources, chemiluminescence and soot were studied experimentally using emission spectroscopy and Laser Induced Incandescence (LII). Reasonable qualitative agreement was found between experimental and model results in terms of flame structure and temperature. Emission spectroscopy and LII results revealed and confirmed earlier observations regarding the low soot concentration of FPO spray flames; furthermore, it was shown that a significant portion of flame radiation originated from graybody char radiation and chemiluminescence from the Na-content of the FPO. These suggest that the treatment of soot formation might not be important in future computational models; however, the description of char formation and Na chemiluminescence will be important for accurately predicting temperature and radiation profiles, important from the point of e.g., large-scale power applications. Confirmed low soot concentrations are promising from an environmental point of view.

  • 17.
    Toth, Pal
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Vikström, Therese
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Gren, Per
    Luleå University of Technology, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Spray combustion of biomass fast pyrolysis oil: Experiments and modeling2019In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 237, p. 580-591Article in journal (Refereed)
    Abstract [en]

    In this work, we are the first to report a detailed comparison between the predictions of a current Computational Fluid Dynamics (CFD) model for describing Fast Pyrolysis Oil (FPO) spray combustion and results from a laboratory-scale experiment. The objectives were to assess the predictive power of the CFD model, evaluate its usefulness in a numerical optimization scenario and characterize the spray flame. The spray flame was produced by using an air-assist atomizer piloted by a CH4/air flat-flame. Pyrolysis oil from a cyclone fast pyrolysis plant was combusted. The flame was characterized by using two-color pyrometry, Tunable Diode Laser Absorption Spectroscopy and high-magnification shadowgraphy. Overall, the assessed model correctly predicted flame structure and seemed appropriate for engineering applications, but lacked predictive power in estimating droplet size distributions. Numerical results were the most sensitive to variations in the initial droplet size distribution; however, seemed robust to changes in the multicomponent fuel formulation. Several conclusions were drawn regarding FPO spray combustion itself; e.g., the amount of produced soot in the flames was very low and droplets exhibited microexplosion behavior in a characteristic size-shape regime. 

  • 18.
    Toth-Pal, Zsolt
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy. University of Miskolc, Hungary.
    Ögren, Yngve
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Sepman, Alexey
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Gren, Per O.
    Luleå University of Technology, Sweden.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Combustion behavior of pulverized sponge iron as a recyclable electrofuel2020In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 373, p. 210-219Article in journal (Refereed)
    Abstract [en]

    In this work, the combustion behavior of pulverized sponge iron (PSI), a practical-grade iron product that was proposed as a potential candidate in the metal fuel cycle, was observed directly using high-magnification shadowgraphy and other optical diagnostics techniques. The PSI was combusted in a laboratory-scale, McKenna flat-flame burner. Results suggest that, in agreement with theoretical models, PSI combusted heterogeneously, with most of the particle mass converting to an intact, solid oxide. However, in contrast with previous hypotheses, the formation of a microflame of combusting aerosol that was attached to the particle surface was observed. Results from quantitative shadowgraphy indicated near-instantaneous melting and complex behavior—we attempted to explain these based on the Fe–O phase diagram. The analysis of micron- and nano-sized combustion products confirmed that the PSI combusted heterogeneously and a gaseous sub-oxide was formed. Combustion under high excess oxygen was hypothesized to reduce the formation of these oxides.

  • 19.
    Wiinikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Lindblom, Bo
    LKAB, Sweden.
    Nordin, Lars-Olof
    LKAB, Sweden.
    Combustion Evaluation of Renewable Fuels for Iron-Ore Pellet Induration2019In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 33, no 8, p. 7819-7829Article in journal (Refereed)
    Abstract [en]

    Induration (or sintering) of iron-ore pellets requires high temperature (∼1300 °C), which today is generated by burning fuel oil in the firing zone of the straight-grate plant (SG) or coal in the rotary kiln of grate-kiln (GK) plants. In this study, ∼150 kWth combustion experiments were used to investigate the opportunity of totally replacing fuel oil with H2 or pyrolysis oil and replacing coal with wood pellets or black pellets powder. For SG plants, the fuel oil can probably be replaced with either H2 or pyrolysis oil without any major concerns, except for slightly or much higher NOx emissions in the case of pyrolysis oil and H2, respectively. For GK induration machines, it is probably challenging to replace coal entirely with biomass since the temperature profile will be different, and there is a risk for increased ash related operational problems. For both SG and GK plants, the slightly lower O2 concentration in the flue gas observed during biomass combustion (pyrolysis oil, wood pellets, and black pellets) may, however, be negative for the induration process, and this needs to be clarified in future research.

  • 20.
    Wiinikka, Henrik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Vikström, Therese
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wennebro, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Pulverized Sponge Iron, a Zero-Carbon and Clean Substitute for Fossil Coal in Energy Applications2018In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, no 9, p. 9982-9989Article in journal (Refereed)
    Abstract [en]

    The direct combustion of recyclable metals has the potential to become a zero-carbon energy production alternative, much needed to alleviate the effects of global climate change caused by the increased emissions of the greenhouse gas CO2. In this work, we show that the emission of CO2 is insignificant during the combustion of pulverized sponge iron compared to that of pulverized coal combustion. The emissions of the other harmful pollutants NOx and SO2 were 25 and over 30 times lower, respectively, than in the case of pulverized coal combustion. Furthermore, 96 wt % of the solid combustion products consisted of micrometer-sized, solid or hollow hematite (α-Fe2O3) spheres. The remaining 4 wt % of products was maghemite (Î-Fe2O3) nanoparticles. According to thermodynamic calculations, this product composition implies near-complete combustion, with a conversion above 98%. The results presented in this work strongly suggest that sponge iron is a clean energy carrier and may become a substitute to pulverized coal as a fuel in existing or newly designed industrial systems.

  • 21.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Gullberg, Marcus
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wennebro, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Influence of oxidizer injection angle on the entrained flow gasification of torrefied wood powder2018In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 181, p. 8-17Article in journal (Refereed)
    Abstract [en]

    In the present work, 5 different axisymmetric burners with different directions of the oxidizer inlets were experimentally tested during oxygen blown gasification of torrefied wood powder. The burners were evaluated under two different O2/fuel ratios at a thermal power of 135 kWth, based on the heating value of torrefied wood powder. The evaluation was based on both conventional methods such as gas chromatography measurements and thermocouples and in-situ measurements using Tunable Diode Laser Absorption Spectroscopy. It was shown that changes in the near burner region influence the process efficiency significantly. Changing the injection angle of the oxidizer stream to form a converging oxidizer jet increased process efficiency by 20%. Besides increased process efficiency, it was shown that improvements in burner design also influence carbon conversion and hydrocarbon production. The burner with the best performance also produced less CH4 and achieved the highest carbon conversion. The effect of generating swirl via rotating the oxidizer jet axes was also investigated. Swirl broadened or removed the impingement area between the fuel and oxidizer jets, however resulting in differences in performance within the measurement uncertainty.

  • 22.
    Ögren, Yngve
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Sepman, Alexey
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Fooladgar, Ehsan
    RISE Research Institutes of Sweden.
    Weiland, Fredrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Wiinikka, Henrik
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy. Luleå University of Technology, Sweden.
    Development and evaluation of a vision driven sensor for estimating fuel feeding rates in combustion and gasification processes2024In: Energy and AI, ISSN 2666-5468, Vol. 15, article id 100316Article in journal (Refereed)
    Abstract [en]

    A machine vision driven sensor for estimating the instantaneous feeding rate of pelletized fuels was developed and tested experimentally in combustion and gasification processes. The feeding rate was determined from images of the pellets sliding on a transfer chute into the reactor. From the images the apparent area and velocity of the pellets were extracted. Area was determined by a segmentation model created using a machine learning framework and velocities by image registration of two subsequent images. The measured weight of the pelletized fuel passed through the feeding system was in good agreement with the weight estimated by the sensor. The observed variations in the fuel feeding correlated with the variations in the gaseous species concentrations measured in the reactor core and in the exhaust. Since the developed sensor measures the ingoing fuel feeding rate prior to the reactor, its signal could therefore help improve process control. 

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  • 23.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology,Sweden.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Qu, Zhechau
    Umeå University, Sweden.
    Schmidt, Florian M.
    Umeå University, Sweden.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Comparison of Measurement Techniques for Temperature and Soot Concentration in Premixed, Small-Scale Burner Flames2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 10, p. 11328-11336Article in journal (Refereed)
    Abstract [en]

    Optical and intrusive measurement techniques for temperature and soot concentration in hot reacting flows were tested on a small-scale burner in fuel-rich, oxygen-enriched atmospheric flat flames produced to simulate the environment inside an entrained flow reactor. The optical techniques comprised two-color pyrometry (2C-PYR), laser extinction (LE), and tunable diode laser absorption spectroscopy (TDLAS), and the intrusive methods included fine-wire thermocouple thermometry (TC) and electrical low pressure impactor (ELPI) particle analysis. Vertical profiles of temperature and soot concentration were recorded in flames with different equivalence and O2/N2 ratios. The 2C-PYR and LE data were derived assuming mature soot. Gas temperatures up to 2200 K and soot concentrations up to 3 ppmv were measured. Close to the burner surface, the temperatures obtained with the pyrometer were up to 300 K higher than those measured by TDLAS. Further away from the burner, the difference was within 100 K. The TC-derived temperatures were within 100 K from the TDLAS results for most of the flames. At high signal-to-noise ratio and in flame regions with mature soot, the temperatures measured by 2C-PYR and TDLAS were similar. The soot concentrations determined with 2C-PYR were close to those obtained with LE but lower than the ELPI results. It is concluded that the three optical techniques have good potential for process control applications in combustion and gasification processes. 2C-PYR offers simpler installation and 2D imaging, whereas TDLAS and LE provide better accuracy and dynamic range without calibration procedures.

  • 24.
    Ögren, Yngve
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Toth, Pal
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. University of Miskolc, Hungary.
    Garami, Attila
    University of Miskolc, Hungary.
    Sepman, Alexey
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center. Luleå University of Technology, Sweden.
    Development of a vision-based soft sensor for estimating equivalence ratio and major species concentration in entrained flow biomass gasification reactors2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 226, p. 450-460Article in journal (Refereed)
    Abstract [en]

    A combination of image processing techniques and regression models was evaluated for predicting equivalence ratio and major species concentration (H2, CO, CO2 and CH4) based on real-time image data from the luminous reaction zone in conditions and reactors relevant to biomass gasification. Two simple image pre-processing routines were tested: reduction to statistical moments and pixel binning (subsampling). Image features obtained by using these two pre-processing methods were then used as inputs for two regression algorithms: Gaussian Process Regression and Artificial Neural Networks. The methods were evaluated by using a laboratory-scale flat-flame burner and a pilot-scale entrained flow biomass gasifier. For the flat-flame burner, the root mean square error (RMSE) were on the order of the uncertainty of the experimental measurements. For the gasifier, the RMSE was approximately three times higher than the experimental uncertainty – however, the main source of the error was the quantization of the training dataset. The accuracy of the predictions was found to be sufficient for process monitoring purposes. As a feature extraction step, reduction to statistical moments proved to be superior compared to pixel binning.

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