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@PHDTHESIS{Schlter:1310,
      key          = {1310},
      othercontributors = {Schlüter, Annette},
      title        = {{U}ntersuchungen zum {V}erschmutzungsverhalten rheinischer
                      {B}raunkohlen in {K}ohledampferzeugern},
      volume       = {7},
      issn         = {1866-1793},
      school       = {RWTH Aachen},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-1310},
      isbn         = {978-3-89336-524-1},
      series       = {Schriften des Forschungszentrums Jülich : Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {164 S.},
      year         = {2008},
      note         = {Record converted from VDB: 12.11.2012; Aachen, RWTH, Diss.,
                      2008},
      abstract     = {In lignite-fired power plants high fouling in heat
                      exchangers can be observed while firing Rhenish brown coals
                      rich in sodium and poor in silicon content. These sulphatic
                      and oxidic deposits reduce the heat transfer and can cause
                      plant damage. It is assumed that fouling is caused by ash
                      softening and partial melting of alkaline phases. The
                      objective of this dissertation is to provide a better
                      understanding of the fouling processes in lignite-fired
                      boilers through experimental analysis using the ashes of
                      different Rhenish brown coals and synthetic ash mixtures. In
                      order to estimate the agglomeration potential of the brown
                      coal ashes and synthetic ash mixtures, measurements of shear
                      properties and impedance spectroscopy were performed.
                      Furthermore, exposure tests in air and flue gas were
                      conducted in the temperature range between 600 to 1,200 °C
                      to evaluate the influence of different parameters on the
                      crystalline phase compounds and microstructures of the brown
                      coal ashes and synthetic ash mixtures. The exposed samples
                      were compared among each other and with corresponding ash
                      deposits produced in a micro combustion chamber. Another aim
                      of this dissertation is to verify the occurrence of NaOH
                      melt in fouling processes. For this purpose impedance
                      spectroscopy with a special probe was performed in the pilot
                      power plant Niederaußem while firing sodium enriched
                      fouling coal. This research indicates the importance of
                      non-silicate bonded sodium and calcium in fouling processes.
                      The higher their contents are, the higher is the fouling
                      potential of the brown coal. Although the occurrence of NaOH
                      in the boiler can not be directly proven by impedance
                      spectroscopy, the experimental results indicate that it
                      plays an important role in fouling. However, this research
                      shows that silicates reduce the fouling potential of the
                      ashes. Shear property measurements, impedance spectroscopy
                      and the calculation of Na/Si and Ca/Si ratios of
                      450°C-ashes are applicable methods to predict the fouling
                      potential of brown coals. According to the findings
                      resulting from this dissertation it is 450°C-ashes with an
                      Na/Si ratio > 2 and a very high Ca/Si ratio that show
                      fouling behaviour.},
      cin          = {IEF-2},
      ddc          = {333.7},
      cid          = {I:(DE-Juel1)VDB810},
      pnm          = {Rationelle Energieumwandlung},
      pid          = {G:(DE-Juel1)FUEK402},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/1310},
}