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@ARTICLE{Seebold:824141,
      author       = {Seebold, Sören and Wu, Guixuan and Müller, Michael},
      title        = {{T}he {I}nfluence of {C}rystallization on the {F}low of
                      {C}oal {A}sh-{S}lags},
      journal      = {Fuel},
      volume       = {187},
      issn         = {0016-2361},
      address      = {New York, NY [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2016-06762},
      pages        = {376-387},
      year         = {2017},
      abstract     = {Numerous technical applications in the energy and
                      metallurgical industries demand a fundamental knowledge of
                      the flow of slags. In particular, the operation of an
                      entrained flow gasifier is challenging, as the oxide slag
                      has to be reliably discharged. Crystallization in the slag
                      influences strongly the flow behavior of the slag because
                      precipitations occur. In this study, the process of
                      crystallization during flow of two coal ash slags was
                      investigated. Therefore, isothermal viscosity measurements
                      were conducted in order to examine the rheological evolution
                      over time caused by the crystallization. It has been
                      demonstrated that the evolution of viscosity of a
                      sub-liquidus melt depends strongly on time, as well as on
                      temperature and composition. Using a rotational
                      high-temperature viscometer to investigate coal slags, it
                      was found that the crystallization during flow could be
                      separated into three time regimes: a lag-time, in which the
                      undercooled melt behaved as an Arrhenius-liquid; the
                      kinetic-driven crystallization; and, finally, the
                      rheological equilibrium that is represented by a constant
                      viscosity. Furthermore, an increase of relative viscosity
                      caused by crystallization was accompanied by a shift from
                      Newtonian to non-Newtonian flow; here, pseudoplastic flow
                      indicated the existence of precipitations. The results
                      demonstrate that the flow behavior has to be divided into
                      dilute, semi-concentrated and concentrated particle bearing
                      fluids. A view into the morphology of the partly
                      crystallized slag was taken by scanning electron microscope.
                      Differential thermal analysis of the slags was conducted, to
                      underline the results of the isothermal viscosity
                      measurements. The degree of supercooling promotes the
                      kinetics of crystallization. Our results demonstrate that
                      time-dependency has to be considered for an accurate
                      description of flow during crystallization, as well as the
                      influence of degree of supercooling.},
      cin          = {IEK-2},
      ddc          = {660},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {111 - Efficient and Flexible Power Plants (POF3-111)},
      pid          = {G:(DE-HGF)POF3-111},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000386187100041},
      doi          = {10.1016/j.fuel.2016.09.078},
      url          = {https://juser.fz-juelich.de/record/824141},
}