Solids back-mixing in the transport zone of circulating fluidized bed boilers
نویسندگان
چکیده
• Experimental and modeled data are used to explain solids back-mixing. Solids back-mixing occurs mainly through the wall layers. Core-to-layer transfer governs in front of lateral dispersion core region. Turbophoresis is identified drive core-to-layer transfer. decay coefficient can be described by a Sh -expression for internal flow. This work investigates transport zone large-scale circulating fluidized bed (CFB) boilers, with aims identifying evaluating governing mechanisms providing mathematical description based on solid theoretical background rather than purely empirical correlations. In addition, transient Direct Numerical Simulation (DNS) modeling identify mechanism that drives migration from dilute up-flow region down-flow at furnace walls. Previously published concentration pressure profiles collated analyzed steady-state mass balance dispersed zone. The study shows layers limited (hence governed) core-to-wall layer movement within latter shown 3-dimensional (3D) model, DNS indicates this due turbophoresis mechanism. We also show use Pe -numbers describe not straightforward but depends unit scale, Pe-numbers < 26 needed yield rates measured CFB boilers. Finally, we propose expression derived Sherwood number ( Sh) -correlation fitted values characteristic constant result better agreement measurements do expressions given literature.
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ژورنال
عنوان ژورنال: Chemical Engineering Journal
سال: 2022
ISSN: ['1873-3212', '1385-8947']
DOI: https://doi.org/10.1016/j.cej.2021.130976