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  • 1.
    Andersson, KM
    et al.
    YKI – Ytkemiska institutet. Stockholms Universitet.
    Bergström, L
    Stockholms Universitet.
    Friction and adhesion of single spray-dried granules containing a hygroscopic polymeric binder2005In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 155, p. 101-107Article in journal (Refereed)
    Abstract [en]

    The atomic force microscope has been used to study the friction and adhesion of single spray dried granules containing a mixture of fine tungsten carbide and cobalt powders and various amounts of a polymeric binder, polyethylene glycol (PEG). The adhesion or the pull-off force and the friction force between two single granules (representing intergranular friction) and between a granule and a hard metal substrate (representing die-wall friction) have been determined as a function of relative humidity. We found that the granule-wall friction increases with binder content and relative humidity. The small friction force at the lowest addition of PEG was related to a small contact area due to the high surface roughness of the granules. The substantial increase in the friction coefficient at PEG-addition>1wt% was related to the plasticity of the binder-rich granule surface where an increase in binder content or relative humidity increases the deformability. The granule-granule friction and adhesion is independent of the relative humidity and substantially lower than the granule-wall friction at all PEG contents, which has important implications for the handling of granular matter

  • 2. LeBell, J
    et al.
    Stenius, P
    YKI – Ytkemiska institutet.
    The influence of cations on particle interactions and particle release fromaqueous bentonite gels1980In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 26, p. 17-27Article in journal (Refereed)
  • 3.
    Meurk, A
    et al.
    YKI – Ytkemiska institutet.
    Yanez, J
    Bergström, L
    YKI – Ytkemiska institutet.
    Silicon nitride granule friction measurements with an atomic force microscope: effect of humidity and binder concentration2001In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 119, p. 241-249Article in journal (Refereed)
    Abstract [en]

    This study introduces the atomic force microscope (AFM) for direct measurement of internal and external friction in ceramic powder pressing. The experiments were performed between two single granules and a granule and a hard metal substrate as a function of granule binder concentration, relative humidity and sliding velocity. Granule-substrate measurements proved the friction coefficient to decrease with increasing humidity within a specific binder concentration, the effect being more pronounced for low concentrations. The friction coefficient also decreased with increasing binder concentration. Evaluation of the adhesion force showed a steady increase with both humidity and binder concentration. A substantial difference, almost an order of magnitude, was seen for the highest binder concentration at low and high humidities. We attribute these findings to the hygroscopic nature of the binder, poly(ethylene glycol) (PEG). Softening of the PEG at increasing humidities lowers the friction coefficient but increases the adhesion force. The results are consistent with flowability measurements and pressing performance.

  • 4.
    Molinder, Roger
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Feeding small biomass particles at low rates2014In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 269, p. 240-246Article in journal (Refereed)
    Abstract [en]

    Biomass particles (75-1000μm) were fed at 9.0-66.5mgmin-1 (2.9-21.7W) using a particle feeder that dispensed particles by gravity through an injection tube. Feed rate was controlled by altering the velocity of a pusher block. Particles were agitated using a vibration motor and fed onto a balance and mass readings were continuously logged. Factors impacting reproducibility and feed rate stability were investigated as well as the effects of particle size and of pusher block velocity. Statistical analysis was applied to investigate patterns in particle feed rate data. Particle aggregation was identified as a factor which influenced feed rate stability and thereby also influencing reproducibility. Feed rate correlated well with pusher block velocity (R2=0.99). Statistical analysis showed strong indications (P values <0.01) of two patterns (clustering and trends) in the feed rate data which were attributed to changes in particle bed appearance with time. With all else being equal, particle size affected feed rate but not feed rate stability. A higher vibration amplitude was needed to agitate smaller particles. It was concluded that particle agitation control is a key to stable feeding of small biomass particles at low rates.

  • 5.
    Saber, Ammar Hazim
    et al.
    Luleå University of Technology, Luleå; University of Mosul, Iraq.
    Göktepe, Burak
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center. Luleå University of Technology, Luleå.
    Umeki, Kentaro
    Luleå University of Technology, Luleå.
    Lundström, T. Staffan
    Luleå University of Technology, Luleå.
    Gebart, Rikard
    Luleå University of Technology, Luleå.
    Active fuel particles dispersion by synthetic jet in an entrained flow gasifier of biomass: Cold flow2016In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 302, p. 275-282Article in journal (Refereed)
    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.

  • 6.
    Sepman, Alexey
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Ögren, Yngve
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Wiinikka, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy, ETC Energy Technology Center.
    Optical techniques for characterizing the biomass particle flow fluctuations in lab- and pilot-scale thermochemical systems2017In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 313, p. 129-134Article in journal (Refereed)
    Abstract [en]

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

  • 7.
    Shenoy, Pooja
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing. University College Cork, Ireland.
    Innings, Fredrik
    Tetra Pak Processing Systems, Sweden.
    Tammel, Kristel
    Santa Maria AB, Sweden.
    Fitzpatrick, John
    University College Cork, Ireland.
    Ahrné, Lilia
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Evaluation of a digital colour imaging system for assessing the mixture quality of spice powder mixes by comparison with a salt conductivity method2015In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 286, p. 48-54Article in journal (Refereed)
    Abstract [en]

    Mixture quality or homogeneity analysis is a crucial step in powder industries to evaluate if the final product meets the requisite standards and therefore industries prefer a method that is reliable and easy to use. In this study the mixture quality of food powder mixtures that differ in mixability and number of components is studied by using digital colour imaging method (DCI) and comparing it with a salt conductivity method. Two binary food and two quaternary food powder mixtures with different coloured particles were studied. Salt was one of the key ingredients commonly used in all the mixtures. Samples were taken at specific times during mixing. The digital colour imaging method was used to measure colour of each sample and salt conductivity analysis measured the corresponding concentration of salt in each sample. Coefficient of variation (CoV) was used to determine the homogeneity of the mixture. Results showed that both methods gave similar results for the well mixing paprika-salt mixture however the DCI method did not work for the oregano-salt mixture which was highly segregating in nature. When the colour difference between the powders was high the DCI method showed a good trend with the salt concentration method. When quaternary mixture consisting of similar coloured particles and segregating particles was used this trend was weaker as compared to the mixture that consisted of cohesive powders that mixed well with each other although they had some particles that were similarly coloured. Overall it showed that DCI method has potential for use by industries that can analyse powder mixtures with components that have differences in colour and that are not strongly segregating in nature

  • 8.
    Shenoy, Pooja
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing. University College Cork, Ireland.
    Viau, Maxime
    Tetra Pak Guerin Systems, France.
    Tammel, Kristel
    Santa Maria AB.
    Innings, Fredrik
    Tetra Pak Processing Systems, Sweden.
    Fitzpatrick, John
    University College Cork, Ireland.
    Ahrné, Lilia
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Effect of powder densities, particle size and shape on mixture quality of binary food powder mixtures2015In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 272, p. 165-172Article in journal (Refereed)
    Abstract [en]

    Particle size and density are two important parameters which affect the mixture homogeneity of powder mixtures. In this study several types of food powders with different particle sizes and poured bulk densities were chosen for the binary powder mixing trials. In each type of binary mixture salt was one of the main ingredients, hence conductivity analysis was performed on the mixtures and coefficient of variation was used to evaluate the mixture homogeneity. All binary powders were mixed at a ratio of 50:50 by weight in a 2. L prototype lab-scale paddle mixer. The experiments were conducted in such a way that the ingredients used either had a similar particle size and different bulk density or similar bulk density and different particle size. Different density and size ratios were investigated to observe the limit up to which good mixing takes place. Density differences between the binary powders were varied from 1.5 up to 16.4. The range of size ratio investigated was from 1.96 up to 15.73. Results indicate that powders mixed very well up to a particle size ratio of 4.45. For higher ratios mixture quality disimproved but no segregation was visually observed. The bulk density had a larger influence in affecting the mixture quality (MQ) as compared to particle size. At higher bulk density ratios almost complete segregation was observed and this was majorly influenced by the irregular shapes of thyme and oregano.

  • 9.
    Xanthakis, Epameinondas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    van Ommen, J. Ruud
    Delft University of Technology, Netherlands.
    Ahrné, Lilia
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Flowability characterization of nanopowders2015In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 286, p. 156-163Article in journal (Refereed)
    Abstract [en]

    The applications of nanopowders are increasing significantly over the last years. In most of these applications, the flow behavior of the nanopowders seems to be a complicated, multiparametric but critical issue for the proper design of the processes. We have investigated, classified and compared several different metal oxide nanoparticles with respect to their flow properties. The flow properties of titania, silica and alumina hydrophilic nanopowders as well as their corresponding hydrophobic counterparts were determined by means of an annular shear cell powder flow tester (PFT). All the tested powders showed difficulties in flow while the titania nanopowders showed the highest difficulty among them. The results acquired regarding the compressibility, the flow functions and the effective angle of internal friction revealed that in all the cases the hydrophobic nanopowder seemed to be more cohesive than its hydrophilic counterpart. Moreover, the nanoparticles, no matter their polarity, showed negligible hygroscopicity while in the case of the alumina nanopowders the flow properties can be significantly influenced by ca. 1% (w/w) of moisture content.

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