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    Lignin pyrolysis in a circulating fluidized bed -influence of temperature and char formation on bed material
    (2014)
    Franck, Miika
    ;
    Hartge, Ernst-Ulrich
    ;
    Heinrich, Stefan
    ;
    Werther, Joachim 
    ;
    Meier, Dietrich
    In this work, the pyrolysis of Kraft lignin in a circulating fluidized bed has been studied. The focus lies on the pyrolysis mechanism and on the influences of temperature and char accumulation in the bed on liquid product yields and composition. Also the yield and composition of gaseous products and char are investigated. The pyrolysis oil yield has its maximum at 650°C. The char yield decreases with rising temperature, while the gas yield in contrary rises. With increasing char deposition on the bed material, oil yield decreases in the considered range by about 10-20%. It can be observed that with increasing char deposition on the bed material the pyrolysis oil composition is shifted towards smaller molecular weight.
    Publicationtype: Conference Paper
      30
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    Spray granulation in a circulating fluidized bed system: The role of breakage and attrition
    (2014-05)
    Stiller, Bjoern
    ;
    Hartge, Ernst-Ulrich
    ;
    Heinrich, Stefan
    ;
    Werther, Joachim 
    The role of breakage and attrition of sucrose particles has been investigated in a circulating fluidized bed (CFB) granulation system consisting of a CFB riser and a solids recycle via a cyclone. In different zones of this system - gas distributor, riser, cyclone - different conditions for particle breakage and attrition prevail whose separate investigation leads to the conclusion that breakage in the cyclone is the dominant mechanism in the system. In order to describe its influence on the granulation result a simple population balance model has been derived.
    Publicationtype: Conference Paper
      22
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    Cfd-dem simulations of the gas and particle dynamics in a novel prismatic spouted bed
    (2014-05)
    Salikov, Vitalij
    ;
    Antonyuk, Sergiy
    ;
    Heinrich, Stefan
    ;
    Sutkar, Vinayak S.
    ;
    Deen, Niels G.
    In this investigation a prismatic spouted bed apparatus with two horizontal gas inlets was modeled by using a Discrete Element Model (DEM) coupled with Computational Fluid Dynamics (CFD), also called Discrete Particle Model (DPM). The bed hydrodynamics were characterized experimentally by means of high speed video recordings and Fast Fourier Transformation (FFT) of the measured pressure drop signal. Different operational regimes could be identified by the FFT. The simulations were performed at the gas flow rates corresponding to the minimum spouting velocity ums, to the upper end of the dense spouting domain and to the instable region at high gas velocities. The simulations predict well the expansion of the particle bed, the particle flow patterns, and characteristic pressure drop fluctuations for all studied regimes. Single peaks in the FFT power plots, characteristic to the stable dense spouting, were obtained and are in good agreement with experiments regarding the frequency of the pressure fluctuations. The irregular pressure behaviour resulting in additional peaks in the FFT spectra was predicted accurately by the DPM model. The spouted bed was characterized regarding the particle micromechanics in the apparatus regions with different particle dynamics, such as the annulus, fountain and spout.
    Publicationtype: Conference Paper
      23