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  • 1.
    Hadi Jafari, Pantea
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wingren, Anders
    Meva Energy AB, Hisings Backa.
    Hellström, J. Gunnar I.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Effect of process parameters on the performance of an air-blown entrained flow cyclone gasifier2019Ingår i: International Journal of Sustainable Energy, ISSN 1478-6451, E-ISSN 1478-646XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    Entrained flow gasification of biomass in a cyclone reactor combined by a gas engine has been applied in Nordic countries as one of the preferred methods for generating combined heat and power in small scales. The purpose of the current study was to optimise the gasification plant efficiency and understanding the influence of operating conditions. The experiments were carried out in a 2.4 MW(th) commercial gasification power plant. The gasifier was operated in optimum at a rather low lambda around 0.27 and a temperature of 950°C. The lower heating value of the clean product gas at this lambda was 5.95 MJ/Nm3. The experimental results also were compared with the predicted values from thermodynamic equilibrium calculations by Factsage 7.0. The performance of five different types of biofuels including torrefied spruce, peat, rice husk, bark and stemwood were assessed and compared with each other using thermodynamic equilibrium and available experimental data.

  • 2.
    Jafri, Yawer
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirtania, Kawnish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Granberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    A study of black liquor and pyrolysis oil co-gasification in pilot scale2018Ingår i: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, Vol. 8, nr 1, s. 113-124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of the blend ratio and reactor temperature on the gasification characteristics of pyrolysis oil (PO) and black liquor (BL) blends with up to 20 wt% PO was studied in a pilot-scale entrained-flow gasifier. In addition to unblended BL, three blends with PO/BL ratios of 10/90, 15/85, and 20/80 wt% were gasified at a constant load of 2.75 MWth. The 15/85 PO/BL blend was used to investigate the effect of temperature in the range 1000–1100 °C. The decrease in fuel inorganic content with increasing PO fraction resulted in more dilute green liquor (GL), and a greater portion of the feedstock carbon ended up in syngas as CO. As a consequence, the cold gas efficiency increased by about 5%-units. Carbon conversion was in the range 98.8–99.5% and did not vary systematically with either fuel composition or temperature. Although the measured reactor temperatures increased slightly with increasing PO fraction, both unblended BL and the 15% PO blend exhibited largely similar behavior in response to temperature variations. The results from this study show that blending BL with the more energy-rich PO can increase the cold gas efficiency and improve the process carbon distribution without adversely affecting either carbon conversion or the general process performance.

  • 3.
    Pantea, Hadi Jafari
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Misiulia, Dzmitry
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hellström, J. Gunnar I.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Modeling of Particle-Laden Cold Flow in a Cyclone Gasifier2018Ingår i: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 141, nr 2, artikel-id 021302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Isothermal transient Eulerian–Lagrangian simulation of the turbulent gas–solid flow in a cyclone gasifier with two inlet tubes at 890 °C has been performed. The single-phase gas flow is modeled using SSG Reynolds stress turbulence model. Ten thousand representative solid particles of different sizes are injected from each inlet continuously at every second of simulation time. Particles are finally stopped as soon as they arrive at the outlet or reach the bottom plate of the gasifier. The effect of particle-to-gas coupling on the pressure and velocity of the flow and particles motion inside the gasifier is studied. The numerical approach can reasonably predict the impact of particle load on the gas flow as presented in the experimental results. Single particles are traveled throughout the transient gas flow field by using Lagrangian approach. High temperature of the gas flow inside the gasifier has significant effects on the swirl intensity reduction, damping the turbulence in the core region, pressure, and particle behaviors. However, the presence of solid particles does not have a notable influence on the swirl intensity and turbulence.

  • 4.
    Göktepe, Burak
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hazim, Ammar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Soot reduction in an entrained flow gasifier of biomass by active dispersion of fuel particles2017Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 201, s. 111-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soot is an undesired by-product of entrained flow biomass gasification since it has a detrimental effect on operation of the gasifier, e.g. clogging of flow passages and system components and reduction of efficiency. This study investigated how active flow manipulation by adding synthetic jet (i.e. oscillating flow through orifice) in feeding line affects dispersion of fuel particles and soot formation. Pine sawdust was gasified at the conditions similar to pulverized burner flame, where a flat flame of methane-air sub-stoichiometric mixture supported ignition of fuel particles. A synthetic jet flow was supplied by an actuator assembly and was directed perpendicular to a vertical tube leading to the center of the flat flame burner through which pine sawdust with a size range of 63–112 μm were fed into a reactor. Quartz filter sampling and the laser extinction methods were employed to measure total soot yield and soot volume fraction, respectively. The synthetic jet actuator modulated the dispersion of the pine sawdust and broke up particle aggregates in both hot and cold gas flows through generation of large scale vortex structures in the flow. The soot yield significantly reduced from 1.52 wt.% to 0.3 wt.% when synthetic jet actuator was applied. The results indicated that the current method suppressed inception of young soot particles. The method has high potential because soot can be reduced without changing major operation parameters.

  • 5.
    Pantea, Hadi Jafari
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hellström, Gunnar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Turbulence Modelling of a Single-Phase Flow Cyclone Gasifier2017Ingår i: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 9, nr 9, s. 779-799, artikel-id 79329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current work aims to make a foundation for an engineering design of a cyclone gasifier to be able not only to predict its flow field with a suitable accuracy but also to investigate a large number of design alternatives with limited computer resources. A good single-phase flow model that can form the basis in an Euler-Lagrange model for multi-phase flow is also necessary for modelling the reacting flow inside a cyclone gasifier. The present paper provides an objective comparison between several popular turbulence modelling options including standard k-ε and SST with curvature corrections, SSG-RSM and LES Smagorinsky models, for the single-phase flow inside cyclone separators/gasifiers that can serve as a guide for further work on the reacting multi-phase flow inside cyclone gasifiers and similar devices. A detailed comparison between the models and experimental data for the mean velocity and fluctuating parts of the velocity profiles are presented. Furthermore, the capabilities of the turbulence models to capture the physical phenomena present in a cyclone gasifier that affects the design process are investigated.

  • 6.
    Hazim, Ammar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Göktepe, Burak
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Active fuel particles dispersion by synthetic jet in an entrained flow gasifier of biomass: Cold flow2016Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 302, s. 275-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pulverized fuel (PF) burners play a key role for the performance of PF fired gasification and combustion plants, by minimizing pollutant emission, fuel consumption and hence fuel costs. However, fuel diversity in power generation plants imposes limitations on the performance of existing PF burners, especially when burning solid fuel particles with poor flowability like biomass sawdust. In the present study, a vertically downward laminar flow was laden with biomass particles at different particle mass loading ratios, ranging from 0.47 to 2.67. The particle laden flow was forced by a synthetic jet actuator over a range of forcing amplitudes, 0.35–1.1 kPa. Pulverized pine particles with a sieve size range of 63–112 μm were used as biomass feedstock. Two-phase particle image velocimetry was applied to measure the velocity of the particles and air flow at the same time. The results showed that the synthetic jet had a large influence on the flow fields of both air and powdered pine particles, via a convective effect induced by vortex rings that propagate in the flow direction. The particle velocity, particle dispersion and hence inter-particle distance increased with increasing forcing amplitude. Moreover, particles accumulated within a specific region of the flow, based on their size. The effect on particle dispersion was more pronounced in the forced flows with low mass loading ratios

  • 7.
    Göktepe, Burak
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hazim, Ammar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Cold flow experiments in an entrained flow gasification reactor with a swirl-stabilized pulverized biofuel burner2016Ingår i: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 85, s. 267-277Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Short particle residence time in entrained flow gasifiers demands the use of pulverized fuel particles to promote mass and heat transfer, resulting high fuel conversion rate. The pulverized biomass particles have a wide range of aspect ratios which can exhibit different dispersion behavior than that of spherical particles in hot product gas flows. This results in spatial and temporal variations in temperature distribution, the composition and the concentration of syngas and soot yield. One way to control the particle dispersion is to impart a swirling motion to the carrier gas phase. This paper investigates the dispersion behavior of biomass fuel particles in swirling flows. A two-phase particle image velocimetry technique was applied to simultaneously measure particle and gas phase velocities in turbulent isothermal flows. Post-processed PIV images showed that a poly-dispersed behavior of biomass particles with a range of particle size of 112-160 μm imposed a significant impact on the air flow pattern, causing air flow decelerated in a region of high particle concentration. Moreover, the velocity field, obtained from individually tracked biomass particles showed that the swirling motion of the carrier air flow gives arise a rapid spreading of the particles

  • 8.
    Göktepe, Burak
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Does distance among biomass particles affect soot formation in an entrained flow gasification process?2016Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 141, nr 1, s. 99-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soot creates technical challenges in entrained flow biomass gasification processes, e.g. clogging of flow passages, fouling on system components and reduced efficiency of gasification. This paper demonstrates a novel soot reduction method in a laboratory-scale entrained flow reactor by forced dispersion of biomass particles. Gasification of small biomass particles was done in a flat flame burner where a steady stream of biomass was sent. The flat flame burner was operated with a premixed sub-stoichiometric methane–air flame to simulate the conditions in an entrained flow gasifier. The dispersion of biomass particles was enhanced by varying the flow velocity ratio between particle carrier gas and the premixed flame. Primary soot particles evolved with the distance from the burner exit and the soot volume fraction was found to have a peak at a certain location. Enhanced particle separation diminished the peaks in the soot volume fraction by 35–56% depending on the particle feeding rates. The soot volume fraction was found to decrease towards an asymptotic value with increasing inter-particle distance.

  • 9.
    Jafri, Yawer
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirtania, Kawnish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Performance of a Pilot-Scale Entrained-Flow Black Liquor Gasifier2016Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, nr 4, s. 3175-3185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pilot-scale entrained flow gasification experiments were carried out at the 3 MWth LTU Green Fuels black liquor gasification (BLG) plant, using ∼140 tons of Kraft black liquor (BL) with a dry solids content of ∼72.5%. Comprehensive mass and energy balances were performed to quantify process performance under varying pressure, load, and oxygen/fuel ratio. Carbon conversion efficiency of the BLG process was 98.3%–99.2% and did not vary systematically in response to process changes. The unconverted carbon is almost exclusively present as dissolved organic carbon in the green liquor (GL) stream. GL is an aqueous solution of sodium carbonate and sodium sulfide used to recover the inorganic pulping chemicals present in BL for reuse in the pulp mill. A small fraction of syngas CO is converted to formate ions dissolved in GL through reaction with hydroxide ions. Unconverted carbon present in GL solids is insignificant. Syngas produced is subsequently upgraded to methanol and dimethyl ether (DME) in an integrated fuel synthesis facility. Concentration of H2 in syngas is not significantly affected by operating point changes in the domain investigated, while CO and CO2 concentrations are. Syngas hydrocarbon concentration values are typically in the single-digit parts per million (ppm) with the exception of C6H6, which was present at 16–127 ppm. CH4 is present at 0.5%–1.2%, with lower concentrations at higher temperatures, and shows good correlation with C6H6. A quantity of 24%–27% of BL sulfur ended up in the syngas as 1.5%–1.7% H2S and 64–72 ppm COS. Cold gas efficiencies (CGEs) on a lower heating value (LHV) basis, when including syngas CH4, were 52%–55% and decreased at higher temperature. CGEs on an LHV basis, when considering only H2 and CO with a sulfur-free BL heating value relevant for catalytic syngas upgrading, were 58%–60% and showed the opposite temperature dependence. Good mass and energy balance closures show the figures presented to be reliable. The results obtained from this study demonstrate process stability at varying operating conditions and can be further used for techno-economic analysis and design purposes.

  • 10.
    Furusjö, Erik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirtania, Kawnish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Jafri, Yawer
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Oller, Albert Bach
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Landälv, Ingvar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Pettersson, Esbjörn
    SP ETC.
    Co-gasification of pyrolysis oil and black liquor - a new track for production of chemicals and transportation fuels from biomass2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Pressurized oxygen-blown entrained flow black liquor (BL) gasification, the Chemrec technology, has been demonstrated in a 3 MWth pilot plant in Piteå, Sweden for more than 25,000 h. The plant is owned and operated by Luleå University of Technology since 2013. It is well known that catalytic activity of alkali metals is important for the high reactivity of black liquor, which leads to a highly efficient BL gasification process. The globally available volume of BL is however limited and strongly connected to pulp production. By co-gasifying pyrolysis oil (PO) with BL it is possible to utilize the catalytic activity also for PO conversion to syngas. Adding PO leads to larger feedstock flexibility with the possibility of building larger biofuels plants based on BL gasification technology. This presentation summarizes new results from research activities aimed at developing and assessing the PO/BL co-gasification process. Results from laboratory experiments with PO/BL mixtures show that pyrolysis behavior and char gasification reactivity are similar to pure BL. This means that the decrease in the alkali metal concentration due to the addition of PO in the mixture does not decrease the reactivity. Pure PO is much less reactive. Mixing tests show that the fraction of PO that can be mixed into BL is limited by lignin precipitation as a consequence of PO acidity. Pilot scale PO/BL co-gasification experiments have been executed following design and construction of a new feeding system to allow co-feeding of PO with BL. The results confirm the conclusions from the lab scale study and prove that the co-gasification concept is practically applicable. Process performance of the pilot scale co-gasification process is similar to gasification of BL only with high carbon conversion and clean syngas generation. This indicates that the established BL gasification technology can be used for co-gasification of PO and BL without major modifications.

  • 11.
    Weiland, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Hedman, Henry
    Energy Technology Centre, Piteå, SP Energy Technology Center AB.
    Wennebro, Jonas
    SP Energy Technology Center AB.
    Pettersson, Esbjörn
    LTU/ETC, Energy Technology Centre, Piteå, SP Energy Technology Center AB.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Influence of process parameters on the performance of an oxygen blown entrained flow biomass gasifier2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 153, s. 510-519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized, O2 blown, entrained flow gasification of pulverized forest residues followed by methanol production is an interesting option for synthetic fuels that has been particularly investigated in the Nordic countries. In order to optimize gasification plant efficiency, it is important to understand the influence of different operating conditions. In this work, a pressurized O2 blown and entrained flow biomass gasification pilot plant was used to study the effect of four important process variables; (i) the O2 stoichiometric ratio (λ), (ii) the load of the gasifier, (iii) the gasifier pressure, and (iv) the fuel particle size. Commercially available stem wood fuels were used and the process was characterized with respect to the resulting process temperature, the syngas yield, the fuel conversion and the gasification process efficiency. It was found that CH4 constituted a significant fraction of the syngas heating value at process temperatures below 1400 °C. If the syngas is intended for catalytic upgrading to a synthetic motor fuel where CO and H2 are the only important syngas species, the process should be optimized aiming for a process temperature slightly above 1400 °C in order to reduce the energetic losses to CH4 and C6H6. This resulted in a cold gas efficiency (based only on CO and H2) of 70%. The H2/CO ratio was experimentally determined within the range 0.45–0.61. Thus, the syngas requires shifting in order to increase the syngas composition of H2 prior to fuel synthesis.

  • 12.
    Risberg, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Carlsson, Per
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Numerical modeling of a 500 kW air-blown cyclone gasifier2015Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 90, s. 694-702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclone gasification of biomass in combination with a gas engine has been considered as a process for combined heat and power production. In this work a numerical model of the cyclone gasification process of wood powder was developed intended to be used as a tool for future engineering design of cyclone gasifiers. The model is based on an Euler-Lagrange formulation for the multiphase flow where the biomass powder was treated as a dispersed phase and the gas as a continuous phase. The results from the simulation are compared with experimental measurement in a 500 kWth cyclone gasifier that uses wood powder as fuel. The model was able to predict the gas composition change with increasing equivalence ratio. The relative error for the main gas component was between 2.5-4.4%, 2.8-5.4%, and 2.6-17.3% for CO2, CO and H2. CH4 was predicted with a relative error of between 3.8-19.2%. Also the model was able to predict the char amount out from the gasifier with reasonable accuracy. The obtained lower heating value from the model was between 3.5 – 5.2 MJ/Nm3 whereas the calculated based on measurement was 4.0-5.3 MJ/Nm3.

  • 13.
    Risberg, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Nilsson, Patrik
    Gudmundsson, Anders
    Sanati, Mehri
    Influence from fuel type on the performance of an air-blown cyclone gasifier2014Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 116, s. 751-759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Entrained flow gasification of biomass using the cyclone principle has been proposed in combination with a gas engine as a method for combined heat and power production in small to medium scale (<20 MW). This type of gasifier also has the potential to operate using ash rich fuels since the reactor temperature is lower than the ash melting temperature and the ash can be separated after being collected at the bottom of the cyclone. The purpose of this work was to assess the fuel flexibility of cyclone gasification by performing tests with five different types of fuels; torrefied spruce, peat, rice husk, bark and wood. All of the fuels were dried to below 15% moisture content and milled to a powder with a maximum particle size of around 1 mm. The experiments were carried out in a 500 kWth pilot gasifier with a 3-step gas cleaning process consisting of a multi-cyclone for removal of coarse particles, a bio-scrubber for tar removal and a wet electrostatic precipitator for removal of fine particles and droplets from the oil scrubber (aerosols). The lower heating value (LHV) of the clean producer gas was 4.09, 4.54, 4.84 and 4.57 MJ/N m3 for peat, rice husk, bark and wood, respectively, at a fuel load of 400 kW and an equivalence ratio of 0.27. Torrefied fuel was gasified at an equivalence ratio of 0.2 which resulted in a LHV of 5.75 MJ/N m3 which can be compared to 5.50 MJ/N m3 for wood powder that was gasified at the same equivalence ratio. A particle sampling system was designed in order to collect ultrafine particles upstream and downstream the gasifier cleaning device. The results revealed that the gas cleaning successfully removed >99.9% of the particulate matter smaller than 1 μm.

  • 14.
    Jafari, Pantea Hadi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hellström, J. Gunnar I.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    On the Influence from Turbulence Modeling on Particle Suspension Flow in Cyclone Gasifiers2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Air-blown cyclone gasification is an entrained flow gasification process in which biomass powder fuel is burnt in a gasifier that operates similarly to a cyclone separator. Cyclone separators are widely used in industry to separate a dispersed solid phase (e.g. particles) from a continuous flow of gas based on density differences. Due to its simple design, the cyclone is a reliable apparatus with low cost for manufacture and maintenance.The performance of an isothermal cyclone separator can be predicted satisfactorily with the model developed by Muschelknautz et al. However, the flow in a non-isothermal cyclone gasifier has additional complexities, e.g. the production of gas from the fuel particles, that are outside the scope of the Muschelknautz model. In order to incorporate these effects more advanced modeling based on Computational Fluid Dynamics is needed. One problem with the CFD approach in combination with turbulent heat transfer and chemical reactions is that the complexity of the global model makes it difficult to assess the accuracy of the sub-models. Recently published models are based on relatively simple eddy-viscosity turbulence models. The agreement between these models and experiments has been encouraging but one cannot rule out the possibility that the apparently good performance of the model is a lucky coincidence due to cancellation of errors in the different sub models.The present paper is focusing on the fluid dynamics modeling of the flow in a cyclone gasifier in order to develop a better foundation for continued modeling. Since simulation of dispersed phase behavior is based on a precise modeling of the continuous phase flow field, it is valuable to assess different numerical approaches to find the most promising one for simulating the turbulent gas phase flow. Due to the complexity of turbulent swirling flow in a cyclone gasifier, a careful selection of turbulence models is needed to fulfill accurate numerical calculations of flow parameters. Two families of turbulence models are supposed to be tested: the two-equation eddy viscosity models including k-epsilon and k-omega, and the Reynolds stress model. For the k-epsilon model, steady-state and transient simulations are implemented. The gas cyclone of Obermair et al. with relevant operating conditions was chosen as a benchmark. The simulation results are compared to the Laser Doppler Anemometry (LDA) velocity measurements of the gas cyclone. The simulations are implemented in the commercial CFD (computational fluid dynamics) code ANSYS CFX 14.5; which uses an element-based finite volume approach. The method involves discretization of the spatial domain using a three-dimensional mesh to build up finite volumes over which relevant quantities like mass, momentum, and energy are conserved. In all, the capability of the mentioned approaches for representing the flow field in general and the precessing vortex core and its related fluctuations in particular will be discussed.

  • 15.
    Weiland, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Nilsson, Patrik T.
    Ergonomics and Aerosol Technology, Lund University.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Gudmundsson, Anders
    Ergonomics and Aerosol Technology, Lund University.
    Sanati, Mehri
    Ergonomics and Aerosol Technology, Lund University.
    Online Characterization of Syngas Particulates Using Aerosol Mass Spectrometry in Entrained-Flow Biomass Gasification2014Ingår i: Aerosol Science and Technology, ISSN 0278-6826, E-ISSN 1521-7388, Vol. 48, nr 11, s. 1145-1155Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Entrained flow gasification is a promising technique where biomass is converted to a synthesis gas (syngas) under fuel rich conditions. In contrast to combustion, where the fuel is converted to heat, CO2 and H2O, the syngas from gasification is rich in energetic gases such as CO and H2. These compounds (CO and H2) represent the building blocks for further catalytic synthesis to chemicals or biofuels. Impurities in the syngas, such as particulates, need to be reduced to different levels depending on the syngas application. The objective of this work was to evaluate the amount of particulates; the particle size distribution and the particle composition from entrained flow gasification of pine stem wood at different operating conditions of the gasifier. For this purpose online time resolved measurements were performed with a Soot Particle Aerosol Mass Spectrometer (SP-AMS) and a Scanning Mobility Particle Sizer (SMPS). The main advantage of SP-AMS compared to other techniques is that the particle composition (soot, PAH, organics and ash forming elements) can be obtained with high time resolution and thus studied as a direct effect of the gasifier operating conditions. The results suggest that syngas particulates were essentially composed of soot at these tested process temperatures in the reactor (1200–1400 °C). Furthermore, the AMS analysis showed a clear correlation between the amounts of polycyclic aromatic hydrocarbons (PAH) and soot in the raw syngas. Minimization of soot and PAH yields from entrained flow gasification of wood proved to be possible by further increasing the O2 addition.

  • 16.
    Landälv, Ingvar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marke, Birgitta
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, TVM Green Fuels Operation.
    Granberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, TVM Green Fuels Operation.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Löwnertz, Patrik
    Chemrec AB, Stockholm.
    Öhrman, Olov
    Energy Technology Centre, Piteå.
    Sørensen, Esben Lauge
    Haldor Topsøe A/S, R&D Department.
    Salomonsson, Per
    Volvo Group Trucks Technology, Gothenburg.
    Two years experience of the BioDME project: A complete wood to wheel concept2014Ingår i: Environmental Progress & Sustainable Energy, ISSN 1944-7442, E-ISSN 1944-7450, Vol. 33, nr 3, s. 744-750Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dimethyl ether (DME), is an excellent diesel fuel that can be produced through gasification from multiple feedstocks. One particularly interesting renewable feedstock is the energy rich by-product from the pulping process called black liquor (BL). The concept of utilizing BL as gasifier feed, converting it via syngas to DME and then compensating the withdrawal of BL energy from the pulp mill by supplying biomass to a conventional combined heat and power plant, is estimated to be one of the most efficient conversion concepts of biomass to a renewable fuel on a well-to-wheel basis. This concept has been demonstrated by the four-year BioDME project, including field tests of DME-fueled heavy-duty trucks that are operated commercially. Up till the summer of 2013 more than 500 tons of BioDME has been produced and distributed to 10 HD trucks, which in total has run more than 1 million km in commercial service

  • 17.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Iisa, Kristiina
    National Renewable Energy Laboratory, Golden, Colorado.
    High-speed imaging of biomass particles heated with a laser2013Ingår i: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 103, s. 278-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work two types of lignocellulosic biomass particles, European spruce and American hardwood (particle sizes from 100 μm to 500 μm) were pyrolysed with a continuous wave 2 W Nd:YAG laser. Simultaneously a high-speed camera was used to capture the behavior of the biomass particle as it was heated for about 0.1 s. Cover glasses were used as a sample holder which allowed for light microscope studies after the heating. Since the cover glasses are not initially heated by the laser, vapors from the biomass particle are quenched on the glass within about 1 particle diameter from the initial particle. Image processing was used to track the contour of the biomass particle and the enclosed area of the contour was calculated for each frame.The main observations are: There is a significant difference between how much surface energy is needed to pyrolyses the spruce (about 75% more) compared to the hardwood. The oil-like substance which appeared on the glass during the experiment is solid at room temperature and shows different levels of transparency. A fraction of this substance is water soluble. A brownish coat is seen on the unreacted biomass. The biomass showed insignificant swelling as it was heated. The biomass particle appears to melt and boil at the front that is formed between the laser beam and the biomass particle. The part of the particle that is not subjected to the laser beam seems to be unaffected.

  • 18.
    Risberg, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Numerical modeling of counter-current condensation in a black liquor gasification plant2013Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 58, nr 1-2, s. 327-335Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized Entrained flow High Temperature Black Liquor Gasification is a novel technique to recover the inorganic chemicals and available energy in black liquor originating from kraft pulping. The gasifier has a direct quench that quickly cools the raw syngas when it leaves the hot reactor by spraying the gas with a water solution. As a result, the raw syngas becomes saturated with steam. Typically the gasifier operates at 30 bar which corresponds to a dew point of about 235 °C and a steam concentration in the saturated syngas that is about 3 times higher than the total concentration of the other species in the syngas. After the quench cooler the syngas is passed through a counter-current condenser where the raw syngas is cooled and most of the steam is condensed. The condenser consists of several vertical tubes where reflux condensation occurs inside the tubes due to water cooling of the tubes on the shell-side. A large part of the condensation takes place inside the tubes on the wall and results in a counterflow of water driven by gravity through the counter current condenser. In this study a computational fluid dynamics model is developed for the two-phase fluid flow on the tube-side of the condenser and for the single phase flow of the shell-side. The two-phase flow was treated using an Euler-Euler formulation with closure correlations for heat flux, condensation rate and pressure drop inside the tubes. The single-phase model for the shell side uses closure correlations for the heat flux and pressure drop. Predictions of the model are compared with results from experimental measurements in a condenser used in a 3 MW Black Liquor Gasification development plant. The results are in good agreement with the limited experimental data that has been collected in the experimental gasifier. However, more validation data is necessary before a definite conclusion can be drawn about the predictive capability of the code

  • 19.
    Weiland, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hedman, Henry
    Energy Technology Centre, Piteå.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Pressurized oxygen blown entrained-flow gasification of wood powder2013Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, nr 2, s. 932-941Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present study, an oxygen blown pilot scale pressurized entrained-flow biomass gasification plant (PEBG, 1 MWth) was designed, constructed, and operated. This Article provides a detailed description of the pilot plant and results from gasification experiments with stem wood biomass made from pine and spruce. The focus was to evaluate the performance of the gasifier with respect to syngas quality and mass and energy balance. The gasifier was operated at an elevated pressure of 2 bar(a) and at an oxygen equivalence ratio (λ) between 0.43 and 0.50. The resulting process temperatures in the hot part of the gasifier were in the range of 1100-1300 °C during the experiments. As expected, a higher λ results in a higher process temperature. The syngas concentrations (dry and N 2 free) during the experiments were 25-28 mol % for H2, 47-49 mol % for CO, 20-24 mol % for CO2, and 1-2 mol % for CH 4. The dry syngas N2 content was varied between 18 and 25 mol % depending on the operating conditions of the gasifier. The syngas H 2/CO ratio was 0.54-0.57. The gasifier cold gas efficiency (CGE) was approximately 70% for the experimental campaigns performed in this study. The synthesis gas produced by the PEBG has potential for further upgrading to renewable products, for example, chemicals or biofuels, because the performance of the gasifier is close to that of other relevant gasifiers

  • 20. Öhrman, Olov
    et al.
    Häggström, Caroline
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Analysis of trace components in synthesis gas generated by black liquor gasification2012Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 102, s. 173-179Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The only pressurized black liquor gasifier currently in operation is located in Sweden. The composition of the main components in the gas has been reported previously. The main components are H2, CO, CO2, N2, CH4, and H2S. In the present work, trace components in the gas have been characterized and the results are hereby reported for the first time. Samples were taken at two occasions during a one year period. The benzene concentration in the gas varied only slightly and the average concentration was 158 ppm. Benzene is formed by thermal cracking of the biomass. The COS concentration varied substantially and the average concentration was 47 ppm. The variations may be related to how the quench is operated. A few ppm of C2-hydrocarbons were also observed in the gas and the variation was probably a result of varying oxygen to black liquor ratio. No tars were observed in the gas. However, tar compounds, such as phenanthrene, pyrene, fluoranthene and fluorene were detected in deposits found on the pipe walls after the gas cooler. The concentration of particles in the synthesis gas was very low; <0.1 mg/N m3, which is comparable to the particulate matter in ambient air. Submicron particles were comprised of elements such as C, O, Na, Si, S, Cl, K, and Ca, and these particles probably originated from the black liquor. Larger particles were comprised mainly of Fe, S and Ni and these particles probably resulted from corrosion of steel in the plant pipe-work. In summary, the concentrations of trace components and particles in the gas are quite low.

  • 21.
    Häggström, Caroline
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Öhrman, Olov
    Rownaghi, Ali
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Catalytic methanol synthesis via black liquor gasification2012Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 94, nr 1, s. 10-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biofuel production from gasified black liquor is an interesting route to decrease green house gas emissions. The only pressurised black liquor gasifier currently in pilot operation is located in Sweden. In this work, synthesis gas was taken online directly from this gasifier, purified from hydrocarbons and sulphur compounds and for the first time catalytically converted to methanol in a bench scale equipment. Methanol was successfully synthesised during 45 h in total and the space time yield of methanol produced at 25 bar pressure was 0.16–0.19 g methanol/(g catalyst h). The spent catalyst exposed to gas from the gasifier was slightly enriched in calcium and sodium at the inlet of the reactor and in boron and nickel at the outlet of the reactor. Calcium, sodium and boron likely stem from black liquor whereas nickel probably originates from the stainless steel in the equipment. A slight deactivation, reduced surface area and mesoporosity of the catalyst exposed to gas from the gasifier were observed but it was not possible to reveal the origin of the deactivation. In addition to water, the produced methanol contained traces of hydrocarbons up to C4, ethanol and dimethyl ether.

  • 22.
    Lycksam, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    High-speed interferometric measurement and visualization of the conversion of a black liquor droplet during laser heating2012Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 50, nr 11, s. 1654-1661Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Black liquor is a mix of organic and inorganic materials that is left after the kraft pulping process. In a modern pulp mill the pulping chemicals and the energy in the black liquor is recovered and used in the pulping cycle by burning the black liquor in a recovery burner. An alternative to the recovery boiler is to gasify the black liquor to produce an energy rich synthesis gas that can be upgraded into synthetic fuels or chemicals. Characterization of black liquor has mostly been done under conditions that are relevant for recovery boilers but the conditions in a gasifier differ significantly from this. In particular the droplets are much smaller and the heating rates are much higher. This paper presents an optical interferometric technique that has the potential to produce data under relevant conditions for gasification. In the paper, results are measured at atmospheric conditions and with relatively low heating rate. However, the method can be applied also for pressurized conditions and at heating rates that are only limited by the frame rate of the digital camera that is used to capture the transient event when the droplets are heated. In the paper the dynamic properties of the gas ejected from and the swelling during conversion of a single droplet are measured

  • 23.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Iisa, Kristiina
    National Renewable Energy Laboratory.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Computational fluid dynamics simulations of raw gas composition from a black liquor gasifier: comparison with experiments2011Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, nr 9, s. 4122-4128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized entrained flow high temperature black liquor gasification can be used as a complement or a substitute to the Tomlinson boiler used in the chemical recovery process at kraft pulp mills. The technology has been proven on the development scale, but there are still no full scale plants. This work is intended to aid in the development by providing computational tools that can be used in scale up of the existing technology. In this work, an existing computational fluid dynamics (CFD) model describing the gasification reactor is refined. First, one-dimensional (1D) plug flow reactor calculations with a comprehensive reaction mechanism are performed to judge the validity of the global homogeneous reaction mechanism used in the CFD simulations in the temperature range considered. On the basis of the results from the comparison, an extinction temperature modification of the steam-methane reforming reaction was introduced in the CFD model. An extinction temperature of 1400 K was determined to give the best overall agreement between the two models. Next, the results from simulations of the flow in a 3 MW pilot gasifier with the updated CFD model are compared to experimental results in which pressure, oxygen to black liquor equivalence ratio, and residence time have been varied. The results show that the updated CFD model can predict the main gas components (H2, CO, CO2) within an absolute error of 2.5 mol %. CH4 can be predicted within an absolute error of 1 mol %, and most of the trends when process conditions are varied are captured by the model.

  • 24.
    Gebart, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, M.
    Energy Technology Centre, Piteå.
    Carlsson, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grönberg, C.
    Weiland, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Johansson, A-C
    Öhrman, Olov
    Recent advances in the understanding of pressurized black liquor gasification2011Ingår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 45, nr 7-8, s. 521-526Artikel i tidskrift (Refereegranskat)
  • 25.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Furusjö, Erik
    Chemrec.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Black liquor gasification: CFD model predictions compared with measurements2010Ingår i: 2010 International Chemical Recovery Conference Proceedings, Norcross, GA: TAPPI Press, 2010, Vol. 2, s. 160-171Konferensbidrag (Refereegranskat)
  • 26.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Piteå.
    Carlsson, Per
    Granberg, Fredrik
    Chemrec.
    Löfström, Johan
    Chemrec.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Tegman, Ragnar
    Chemrec.
    Lindblom, Mats
    Chemrec.
    Gebart, Rikard
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Design and methodology of a high temperature gas sampling system for pressurized black liquor gasification2010Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, nr 9, s. 2583-2591Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes the system design and methodology for high temperature gas sampling during pressurized black liquor gasification. The motivation for developing a system that can withstand the harsh conditions in the reactor part of the gasifier (30 bar, 1000 °C, reducing conditions and corrosive environment) comes from an ambition to better understand the various stages in the conversion of the fuel (black liquor) and provide spatially resolved data of the gas composition inside the gasification reactor. Important components in the high temperature sampling system which are all described in detail in the paper, are the syngas sampling line, nitrogen purging system, water cooling line and an aerodynamic quench probe with an anti-clogging shield. Several measurement campaigns have been conducted in the gasifier where the concentration of CO2, CO, H2, CH4, H2S, and COS close to the outlet of the hot reactor have been measured with the high temperature gas sampling system. The results showed that the repeatability of the measured gas composition was excellent and that significant effects on the gas composition from different operating parameters of the gasifier could be found.

  • 27. Carlsson, Per
    et al.
    Wiinikka, Henrik
    Energy Technology Centre, Piteå.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Grönberg, Carola
    Energy Technology Centre, Piteå.
    Pettersson, Esbjörn
    Energy Technology Centre, Piteå.
    Lidman, Marcus
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Energy Technology Centre, Piteå.
    Experimental investigation of an industrial scale black liquor gasifier: 1. Influence of reactor operation parameters on product gas composition2010Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 89, nr 12, s. 4025-4034Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient fuel synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO2, CO, H2, CH4, H2S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.

  • 28.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Furusjö, Erik
    Chemrec.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Experiments and mathematical models of black liquor gasification: influence of minor gas components on temperature, gas composition, and fixed carbon conversion2010Ingår i: TAPPI Journal, ISSN 0734-1415, Vol. 9, nr 9, s. 15-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, predictions from a reacting Computational Fluid Dynamics (CFD) model of a gasification reactor are compared to experimentally obtained data from an industrial pressurized black liquor gasification plant. The data consists of gas samples taken from the hot part of the gasification reactor using a water cooled sampling probe. During the considered experimental campaign, the oxygen-to-black liquor equivalence ratio (λ) was varied in three increments, which resulted in a change in reactor temperature and gas composition. The presented numerical study consists of CFD and thermodynamic equilibrium calculations in the considered λ-range using boundary conditions obtained from the experimental campaign. Specifically, the influence of methane concentration on the gas composition is evaluated using both CFD and thermodynamic equilibrium. The results show that the main gas components (H2, CO, CO2) can be predicted within a relative error of 5% using CFD if the modeled release of H2S and CH4 are specified a priori. In addition, the calculations also show that the methane concentration has large influence on the reactor outlet temperature and final carbon conversion.

  • 29.
    Grip, Carl-Erik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Sandström, Erik
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Karlsson, Jonny
    Industrial ecology in northern areas: practical experience and development2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    The possibilities to develop the industrial ecology in the northern regions of Europe are influenced by some common characteristics, e.g.: The regions are rich in natural re-sources and energy- and material intensive base industries. These industries cover sev-eral branches, e.g., Mining, Iron and Steel, Metal production, Pulp and Paper. Low popu-lation density and relatively long distances to the main customers are difficulties espe-cially for transport and use of rest products. District heating with waste heat from the in-dustries is an important part of the energy system that reduces the emission of green-house gases and improves the overall energy efficiency. The problems and possibilities connected to the industrial ecology are described for two examples, the energy system in Luleå and the Solander science park in Piteå

  • 30. Göktepe, Burak
    et al.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Fernandes, Edgar
    Instituto Superior Técnico, Dpartment of Mechanical Engineering/Center IN.
    Leitão, Noel
    Instituto Superior Técnico, Dpartment of Mechanical Engineering/Center IN.
    Leitão, Ivo
    Instituto Superior Técnico, Dpartment of Mechanical Engineering/Center IN.
    Merícia, Janaína Gomes de
    Instituto Superior Técnico, Dpartment of Mechanical Engineering/Center IN.
    Simultaneous pressure and heat release measurements in a 150kW wood powder burner2010Konferensbidrag (Övrigt vetenskapligt)
  • 31. Göktepe, Burak
    et al.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Leitao, Noel
    Instituto Superior Técnico, Dpartment of Mechanical Engineering/Center IN.
    Fernandesc, Edgar
    Instituto Superior Técnico, Dpartment of Mechanical Engineering/Center IN.
    Visualization of the reactive swirling flows in a 150 KW wood powder burner2010Konferensbidrag (Övrigt vetenskapligt)
  • 32.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grönberg, Carola
    Energy Technology Centre, Piteå.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Risberg, Mikael
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov
    Spatially resolved measurements of gas composition in a pressurised black liquor gasifier2009Ingår i: Environmental Progress & Sustainable Energy, ISSN 1944-7442, E-ISSN 1944-7450, Vol. 28, nr 3, s. 316-323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Black liquor gasification is a new process for recovery of energy and chemicals in black liquor from the Kraft pulping process. The process can be combined with catalytic conversion of syngas into motor fuels. The potential for motor fuel production from black liquor in Sweden is to replace about 25% of the current consumption of gasoline and diesel. For Finland the figure is even higher while for Canada it is about 14% and for the USA about 2%.

  • 33.
    Marklund, Magnus
    et al.
    Energy Technology Centre, Piteå.
    Tegman, R.
    Chemrec AB, Piteå.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    A self-consisted CFD-model for pressurized high temperature black liquor gasification2008Ingår i: Industrial Combustion, ISSN 2075-3071, E-ISSN 2075-3071, s. 1-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High temperature pressurised black liquor gasification has the potential to significantly improve the efficiency of energy and chemical recovery in the pulping industry. However, a lack of demonstration of the reliability of the process has delayed its large scale industrial implementation. As an important step towards a greater trust in the process reliability, a self-consistent CFD model has been developed. This paper contains a detailed description of the model and a performance prediction of an entrained flow pilot gasifier for a typical operational condition. Emphasis is put on the modelling of input data for the CFD simulation where eight key assumptions form the basis for a consistent model of the black liquor composition. The results for the pilot gasifier performance with typical values for the design variables indicate that the droplet size should be <200 μm and/or have a residence time of 2-3 s for a high level of carbon conversion.

  • 34.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Comparison and validation of gas phase reaction schemes for black liquor gasification modeling2008Ingår i: Conference Proceedings 2008 AiChE annual meeting: Advances in gasification research, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Pressurized Entrained-flow High Temperature Black Liquor Gasification (PEHT-BLG) is a potential substitute or complement to the recovery boiler traditionally used for the recovery of chemicals and energy in black liquor in the Kraft pulping process. Black liquor consists of roughly 30 % moisture, 35 % inorganic pulping chemicals and 35 % combustible material (i.e. lignin). The PEHT-BLG technology can give an increase in total energy efficiency of the mill and provide new products with high added value, such as green motor fuels. The main parts of the recovery unit in the process are; a slagging refractory lined entrained-flow gasification reactor, with a gas assisted burner nozzle producing small black liquor droplets, used for direct gasification of the black liquor at about 1000 °C to produce a ‘raw' syngas and a liquid smelt containing mainly Na2CO3 and Na2S; a quench cooler beneath the reactor where the product gas and smelt are separated and the smelt is dissolved in water forming green liquor; a counter current condenser (CCC) that cools the syngas and condenses water vapor and any volatile and tar species that may be present. The heat recovered from the gas condensation is used to generate low/medium pressure steam that can be used in the pulp and paper process. Furthermore, the chemicals in the green liquor are recovered as cooking chemicals in the downstream processing. Due to lack of demonstration of long term operation of the technology, a development (pilot) plant for PEHT-BLG (named DP-1) with a capacity of 20 tones dry solids/24h is in operation by the technology vendor Chemrec AB at the Energy Technology Centre in Piteå, Sweden. An important tool for reduction of the technical risk associated with scale up of new technology is a comprehensive CFD model for the PEHT-BLG reactor. The current model includes drying, pyrolysis, char gasification and smelt formation of black liquor droplets as well as a simplified gas phase reaction mechanism. The current model has been validated against the outlet gas composition after the Counter Current Condenser (CCC). The model predicted a CO / CO2 ratio that was approximately 50% higher compared to the measurements. However, it is possible that the well known water-gas shift reaction is active in the quench and this could explain that the experimentally determined gas composition after the CCC differs from the computational results at the outlet from the hot zone. Recently, in-situ measurements have been performed in the DP-1 reactor and a further validation of the model has been made possible. The measurements have been performed by sampling gas with a water-cooled suction probe from the lower part of the hot zone, followed by offline gas analyses. The present paper investigates the difference between the current CFD-model and a modified version with an additional CO + O2 reaction added to the simplified gas phase reaction scheme. The simulation results are compared against measurements obtained by the gas sampling probe in the DP-1 reactor. The results suggest that by implementing the additional CO + O2 reaction local flame temperature was increased significantly. However, the effect on volume average and outlet gas temperature was minimal.The results also showed that the CO + O2 reaction had very little effect on outlet gas composition when the reaction was implemented in the PEHT-BLG-CFD model

  • 35.
    Gebart, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov
    Energy Technology Centre, Piteå.
    Pettersson, Esbjörn
    Energy Technology Centre, Piteå.
    Risberg, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Carlsson, Per
    Energy Technology Centre, Piteå.
    Turning a pulp mill into a biorefinery: A possible outcome from the 2nd black liquor gasification program2008Ingår i: NWBC 2008: 2008 Nordic Wood Biorefinery conference : 11-14 March, 2008 : City Conference Centre, Stockholm, Sweden, Stockholm: STFI-Packforsk AB , 2008, s. 56-61Konferensbidrag (Refereegranskat)
  • 36.
    Marklund, Magnus
    et al.
    Energy Technology Centre, Piteå.
    Tegman, Ragnar
    Chemrec AB, c/o ETC, Piteå.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    CFD modelling of black liquor gasification: identification of important model parameters2007Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, nr 12-13, s. 1918-1926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized high temperature black liquor gasification has the potential to significantly improve the efficiency of energy and chemical recovery in the pulping industry and to enable new processes, e.g. production of renewable automotive fuels from the formed synthesis gas. However, the current process is still considered as novel and the interest in validated computer models for scale-up and process optimisation is large. In this paper a sensitivity analysis on the four most important model parameters in the pre-processing ‘droplet composition model' for a proposed CFD model has been performed. It was shown that careful measurements of the amount of sulphur released to the gas phase as H2S during devolatilization and the concentration ratio of Na2S and Na2SO4 in the black liquor char under real process conditions are of great importance for calibration of the model.

  • 37.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Energy Technology Centre, Piteå.
    Boman, Christoffer
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Influence of fuel ash composition on high temperature aerosol formation in fixed bed combustion of woody biomass pellets2007Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, nr 1, s. 181-193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the influence of fuel ash composition on high temperature aerosol formation during fixed bed combustion of woody biomass (two wood pellets and one bark pellets) were investigated experimentally in a laboratory reactor and theoretically through chemical equilibrium model calculations. For all fuels, the particle mass size distribution in the PM2.5 region was bimodal, with one fine mode and one coarse mode. Early in the flame, the fine mode was dominated by particles from incomplete combustion and these particles were rapidly oxidised in the post flame zone. After the hot flame, the fine mode concentration and the particle diameter increases gradually when the temperature decreases due to condensation of vaporised inorganic matter, K, Na, S, Cl, and Zn. For two of the fuels also P could be found in the fine particles. The coarse mode consisted of carbon, refractory metals and considerable amount of alkali. Further, the initial fuel alkali concentration and the alkali to silicon ratio (K + Na)/Si influenced the amount of vaporised aerosol forming alkali matter. Finally, the present study shows that, combustion temperature and fuel ash composition is of major importance for the formation of high temperature aerosols in fixed bed combustion of woody biomass pellets.

  • 38.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    The importance of mechanics in black liquor gasification2007Ingår i: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, s. 61-Konferensbidrag (Övrigt vetenskapligt)
  • 39.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Energy Technology Centre, Piteå.
    Boman, Christoffer
    Umeå university.
    Boström, Dan
    Umeå university.
    Öhman, Marcus
    Nordin, Anders
    Umeå university.
    High-temperature aerosol formation in wood pellets flames: spatially resolved measurements2006Ingår i: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 147, nr 4, s. 278-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation and evolution of high-temperature aerosols during fixed bed combustion of wood pellets in a realistic combustion environment were investigated through spatially resolved experiments. The purpose of this work was to investigate the various stages of aerosol formation from the hot flame zone to the flue gas channel. The investigation is important both for elucidation of the formation mechanisms and as a basis for development and validation of particle formation models that can be used for design optimization. Experiments were conducted in an 8-kW-updraft fired-wood-pellets combustor. Particle samples were withdrawn from the centerline of the combustor through 10 sampling ports by a rapid dilution sampling probe. The corresponding temperatures at the sampling positions were in the range 200-1450 °C. The particle sample was size-segregated in a low-pressure impactor, allowing physical and chemical resolution of the fine particles. The chemical composition of the particles was investigated by SEM/EDS and XRD analysis. Furthermore, the experimental results were compared to theoretical models for aerosol formation processes. The experimental data show that the particle size distribution has two peaks, both of which are below an aerodynamic diameter of 2.5 μm (PM2.5). The mode diameters of the fine and coarse modes in the PM2.5 region were [similar to] 0.1 and [similar to] 0.8 μm, respectively. The shape of the particle size distribution function continuously changes with position in the reactor due to several mechanisms. Early, in the flame zone, both the fine mode and the coarse mode in the PM2.5 region were dominated by particles from incomplete combustion, indicated by a significant amount of carbon in the particles. The particle concentrations of both the fine and the coarse mode decrease rapidly in the hot oxygen-rich flame due to oxidation of the carbon-rich particles. After the hot flame, the fine mode concentration and particle diameter increase gradually when the temperature of the flue gas drops. The main contribution to this comes from condensation on preexisting particles in the gas of alkali sulfates, alkali chlorides, and Zn species formed from constituents vaporized in the fuel bed. The alkali sulfates were found to condense at a temperature of [similar to] 950 ° C and alkali chlorides condensed later at [similar to] 600 ° C. This agrees well with results of chemical equilibrium calculation of the gas-to-particle conversion temperature. After the hot flame the coarse mode concentration decreased very little when the flue gas was cooled. In addition to carbon, the coarse mode consists of refractory metals and also considerable amounts of alkali.

  • 40.
    Marklund, Magnus
    et al.
    Energy Technology Centre, Piteå.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Fletcher, D.F.
    University of Sydney.
    Determination of the influence of uncertain model parameters in pressurized gasification of black liquor using a factorial design2005Ingår i: Combustion Science and Technology, ISSN 0010-2202, E-ISSN 1563-521X, Vol. 177, nr 3, s. 435-453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Introduction of pressurized gasification of black liquor in the pulping industry has the potential to give a significant increase in energy efficiency. However, uncertainties about the reliability and robustness of the technology are preventing large-scale market introduction. One important step toward a greater trust in the process reliability is the development of a better understanding of the sensitivity of the process to parameter variations. A computational fluid dynamics model for pressurized gasification of black liquor in an entrained-flow gasifier is presented and used for investigation of the effects of uncertainties in the specific heat capacity of black liquor, the radiation absorption coefficient, and the volatile devolatilization rate using factorial design methodology. It is found that all main factor effects, but none of the interaction effects, influence the considered responses: char conversion, maximum temperature, and outlet temperature. However, the main effects are found to be relatively small and the uncertainties in the examined model parameters would not invalidate the results from a design optimization with the presented model.

  • 41.
    Wiinikka, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    The influence of air distribution rate on particle emissions in fixed bed combustion of biomass2005Ingår i: Combustion Science and Technology, ISSN 0010-2202, E-ISSN 1563-521X, Vol. 177, nr 9, s. 1747-1766Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Combustion of biomass under fixed-bed conditions will generate both coarse and fine particles that have a negative effect on technical performance or pose health hazards. It is therefore important to reduce the emissions of these particles that are already in the combustion process. The aim of this study was to experimentally investigate how different air supply strategies affect the particle emission in fixed-bed combustion of biomass. The air was supplied either through the grate, through a secondary air register, or equally divided between the two. The results showed that the air supply affects the emissions of both coarse and especially fine fly ash particles. The emissions of fine particles decrease when the air supply through the grate decreases, probably due to lower oxygen concentration in the fuel bed and thereby lower temperature in the burning char particles, which results in less vaporisation of ash elements. Hence, changing or optimizing the air supply strategy appears to be an attractive way to reduce the particle emissions already in the combustion process. Copyright

  • 42.
    Wiinikka, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    The influence of fuel type on particle emissions in combustion of biomass pellets2005Ingår i: Combustion Science and Technology, ISSN 0010-2202, E-ISSN 1563-521X, Vol. 177, nr 4, s. 741-763Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three different biomass fuels (bark pellets, wood pellets and granulates made from hydrolysis residues) were burned under identical conditions to determine the effect of biomass type on the amount and composition of the combustion-generated particles under fixed-bed conditions. Significant differences in emissions of dust, submicron particles, and the shape of the particle number and mass size distributions were found between the different biomass fuels. For the particles that were dominated by ash elements, the particle emissions were correlated to the ash concentration in the unburned fuel. However, if the combustion condition allowed for organic particles, the "sooting" tendency of the fuel was found to become more important than the amount of ash in the fuel. Furthermore, the fuel type affects the particle emissions more than changes in reactor operating parameters.

  • 43.
    Wiinikka, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Critical parameters for particle emissions in small-scale fixed-bed combustion of wood pellets2004Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 18, nr 4, s. 897-907Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, laboratory experiments in a small-scale (10 kW) reactor have been performed to investigate the particle formation mechanisms and the influence of different operating parameters on the particle emissions from combustion of wood pellets under fixed-bed conditions. The results presented herein show that the particles from fixed-bed combustion are formed from three different mechanisms: coarse fly ash particles (>10 μm) are released by mechanical ejection from the fuel bed, submicrometer-sized fly ash particles are produced from the vaporization and nucleation of ash minerals, and, finally, submicrometer-sized soot particles are produced from incomplete combustion. Significant effects on the particle emissions have been observed for the combustor wall temperature and the flow pattern in the combustion zone. Increasing the combustor wall temperature yields a decrease in the emissions of coarse fly ash and soot particles; however, the emissions of submicrometer-sized fly ash particles increase simultaneously. For example, the emissions of soot are reduced by a factor of ~5 and the emissions of fly ash are increased by a factor of ~2 when the wall temperature increases from 400° C to 950°C. Increasing the mixing rate in the combustion chamber will also decrease the emissions of soot particles. An important conclusion from this study is that the total emissions of particles can be minimized in fixed-bed combustion of a solid biomass by minimizing the combustion temperature in the burning char particle and maximizing the temperature in the secondary combustion zone.

  • 44.
    Wiinikka, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Detailed experimental investigation of the formation of submicron aerosols in wood pellets flames2004Ingår i: NOSA Aerosol Symposium Stockholm: Conference Proceedings, Nordic Society for Aerosol Research , 2004Konferensbidrag (Övrigt vetenskapligt)
  • 45.
    Wiinikka, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Experimental investigations of the influence from different operating conditions on the particle emissions from a small-scale pellets combustor2004Ingår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, nr 6, s. 645-652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study is to determine how different design parameters in an idealised small-scale combustor affect the emission of particulates in the flue gas and to provide insight that can be used for design optimisation. The design parameters are the primary air factor, the total air factor and the magnitude of swirling flow in the combustion chamber. Particles from the reactor were collected from two different sampling lines, one located in the combustion zone, just above the fuel bed, and the other in the flue stack after the reactor. The measurements show that this burner gives very low emissions of particulates and CO in the flue gas. Furthermore, the concentration of particles in the flue gas is uncoupled to the concentration of particles immediately above the fuel bed, probably as a result of a well-designed secondary air supply. The variable that had the strongest effect on the total particulate emission from the combustor was the total air factor. In order to understand the qualitative differences in the flow nature between different operating conditions, CFD simulations of the flow field were also performed.

  • 46.
    Wiinikka, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Formation of soot and submicron fly ash in a wood pellets flame2004Konferensbidrag (Refereegranskat)
  • 47.
    Andersson, H.M.
    et al.
    Luleå tekniska universitet.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Synnergren, Per
    Luleå tekniska universitet.
    Application of digital speckle photography to measure thickness variations in the vacuum infusion process2003Ingår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 24, nr 3, s. 448-455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new method to measure the movement of the flexible bag used in vacuum infusion is presented. The method is based on an in-house developed stereoscopic digital speckle photography system (DSP). The advantage with this optical method, which is based on cross-correlation, is that the deflection of a large area can be continuously measured with a great accuracy (down to 10 μm. The method is at this stage most suited for research but can in the long run also be adopted in production control and optimization. By use of the method it was confirmed that a ditch is formed at the resin flow front and that there can be a considerable and seemingly perpetual compaction after complete filling. The existence of the ditch demonstrates that the stiffness of the reinforcement can be considerably reduced when it is wetted. Hence, the maximum fiber volume fraction can be larger than predicted from dry measurements of preform elasticity. It is likely that the overall thickness reduction after complete filling emanates from lubrication of the fibers combined with an outflow of the resin. Besides, the cross-linking starts and the polymer shrinks. Hence, the alteration in height will continue until complete cross-linking is reached.

  • 48. Andersson, Magnus
    et al.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Numerical model for vacuum infusion manufacturing of polymer composites2003Ingår i: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, E-ISSN 1758-6585, Vol. 13, nr 3, s. 383-394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The focus is set on the development and evaluation of a numerical mgodel describing the impregnation stage of a method to manufacture fibre reinforced polymer composites, namely the vacuum infusion process. Examples of items made with this process are hulls to sailing yachts and containers for the transportation industry. The impregnation is characterised by a full 3D flow in a porous medium having an anisotropic, spatial- and time-dependent permeability. The numerical model has been implemented in a general and commercial computational fluid dynamic software through custom written subroutines that: couple the flow equations to the equations describing the stiffness of the fibre reinforcement; modify the momentum equations to account for the porous medium flow; remesh the computational domain in each time step to account for the deformation by pressure change. The verification of the code showed excellent agreement with analytical solutions and very good agreement with experiments. The numerical model can easily be extended to more complex geometry and to other constitutive equations for the permeability and the compressibility of the reinforcement.

  • 49. Burman, Jörgen
    et al.
    Papila, Nilay
    Shyy, Wei
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Assessment of response surface-based optimization techniques unsteady flow around bluff bodies2002Ingår i: A collection of technical papers: 9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization : Atlanta, Georgia, 4 - 6 September 2002, Reston, Va.: American Institute of Aeronautics and Astronautics, AIAA , 2002Konferensbidrag (Refereegranskat)
    Abstract [en]

    The shape of a trapezoidal obstacle immersed in a 2D unsteady, viscous flow is optimized by response surface (RS) techniques based on combined criteria of minimum total drag and maximum mixing efficacy. Time-dependent Navier-Stokes computations are conducted to supply the database. In order to address the issues related to noise, an outlier analysis based on iteratively re-weighted least square (IRLS) method is applied. The results indicate that optimum designs having a low mean drag coefficient tend to be square-shaped, while designs having a large value of the mixing effectiveness are more trapezoidally-shaped. Both RS and IRLS models yield consistent designs, indicating that the present task is well handled by the techniques employed. In addition, the RS methodology is used to identify domains within the design space within which all designs are, for practical purpose, acceptable.

  • 50. Andersson, Magnus
    et al.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Långström, R.
    Swedish Institute of Composites, Piteå.
    Flow-enhancing layers in the vacuum infusion process2002Ingår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 23, nr 5, s. 895-901Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current trend towards increased use of vacuum infusion molding for large surface-area parts has increased the interest in an advanced modeling of the process. Because the driving pressure is limited to 1 atmosphere, it is essential to evaluate possible ways to accelerate the impregnation. One way of doing this is to use layers of higher permeability within the reinforcing stack, i.e. flow-enhancing layers. We present an experimental investigation of the flow front shape when using such layers. The through-thickness flow front was observed by making a number of color marks on the glass-mats forming the reinforcing stack, which became visible when the resin reached their position. The in-plane flow front was derived from observations of the uppermost layer. It turned out that existing analytical models agree very well with the experiments if effective permeability data is used, that is, permeability obtained from vacuum infusions. However, the fill-time was nearly twice as long as predicted from permeability data obtained in a stiff tool. This rather large discrepancy may be due to certain features of a flexible mold half and is therefore a topic for further research. The lead-lag to final thickness ratio is dependent on the position of the flow front and ranges form 5 to 10 for the cases tested. Interestingly the lead-lag has a miximum close to the inlet.

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