4 results for Ashman, P.J.

  • Influence of droplet size on the release of atomic sodium during the combustion of black liquor

    Saw, W.L.; Nathan, G.J.; Ashman, P.J.; Hupa, M. (2009)

    Conference Contributions - Published
    University of Canterbury Library

    This paper reports on the implementation of a quantitative planar laser-induced fluorescence (PLIF), which employs an absorption technique simultaneously, to assess the effect of initial diameter on the release of atomic sodium. The temporal release of the atomic sodium under fuel rich conditions was found to be different from that under fuel lean conditions, especially during the smelt coalescence stage. The total atomic sodium released and the release rate of atomic sodium increase as the initial diameter of the black liquor droplet is decreased. This highlights the role of small droplets, possibly derived from ejecta, in fume formation.

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  • Surface temperature measurement of a burning black liquor droplet using two-colour optical pyrometry

    Saw, W.L.; Nathan, G.J.; Ashman, P.J.; Alwahabi, Z.T.; Hupa, M. (2009)

    Conference Contributions - Published
    University of Canterbury Library

    This paper reports on the implementation of two-colour optical pyrometry to measure the distribution of surface temperature of a burning black liquor droplet in a flat flame environment. The black liquor was burned in the flame provided by the flat flame burner at two flame conditions, fuel lean (Øbg = 0.8), and fuel rich (Øbg = 1.25). Two identical digital singlelens reflex (SLR) cameras were used to allow the simultaneous measurement of the surface temperature and particle size. This provides an opportunity for more reliable measurements of surface temperature for black liquor than has previously been available.

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  • Assessment of the release of atomic Na from a burning black liquor droplet using quantitative PLIF

    Saw, W.L.; Nathan, G.J.; Ashman, P.J.; Alwahabi, Z.T. (2009)

    Journal Articles
    University of Canterbury Library

    The quantitative measurement of atomic sodium (Na) release, at high concentration, from a burning black liquor droplet has been demonstrated using a planar laser-induced fluorescence (PLIF) technique, corrected for fluorescence trapping. The local temperature of the particle was measured to be approximately 1700 C, at a height of 10 mm above a flat flame burner. The PLIF technique was used to assess the temporal release of atomic Na from the combustion of black liquor and compare it with the Na concentration in the remaining smelt. A first-order model was made to provide insight using a simple Plug Flow Reactor model based on the independently measured concentration of residual Na in the smelt as a function of time. This model also required the dilution ratio of the combustion products in the flat flame entrained into the plume gas from the black liquor particle to be estimated. The key findings of these studies are: (i) the peak concentration of atomic Na from the combustion of the black liquor droplets is around 1.4 ppm; (ii) very little atomic Na is present during the drying, devolatilisation or char combustion stages; and (iii) the presence of atomic Na during smelt phase dominates over that from the other combustion stages.

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  • The Influence of Boron on the Emission of Sodium during Black Liquor Combustion under Oxidative Conditions

    Saw, W.L.; Forssén, M.; Hupa, M.; Nathan, G.J.; Ashman, P.J. (2009)

    Journal Articles
    University of Canterbury Library

    The addition of boron to black liquor has the potential to reduce fume formation in a Kraft recovery boiler. Two Kraft black liquors, with and without boron, were analysed. Single 10 mg droplets were introduced into a furnace and were burned at temperatures of 900, 1000 and 1050ºC with oxygen concentrations of 2, 5 and 10 (vol %). Under these conditions, the addition of boron to the black liquor is found to reduce both the extent of sodium emission and the combustion time. This shows that the boron reduced the sodium loss due to the lower amount of sodium carbonate available to be decomposed by the char. The char combustion time of the liquor with boron is found to be shorter because some of the char may be consumed by the borate. The added boron reduced the sodium loss mainly during the char combustion stage.

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