Influence of Exit Configuration on the Hydrodynamic Behaviors of a High-Density Circulating Fluidized Bed Riser

Abstract

The influence of three different exit configurations (L-shape, T-shape and V-shape) on the hydrodynamic behaviors was investigated in a high-density circulating fluidized bed (HDCFB). The solid circulation rate G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> was up to 865 kg/(m2s) by using the Geldart group B silica sand (particle density ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> is 3092 kg/m3, Sauter mean diameter d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> is 106 μm) as bed material. Under high G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> conditions, no increase of solid concentration was observed using the L-shape, T-shape and V-shape abrupt configuration, which was different from the previous published results. However, the solid concentration increased obviously near the riser exit zone under low G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> conditions with the V-shape configuration. Composition of the pressure drop near the exit region was analyzed. The pressure drop across the reducing pipe (ΔP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rp</sub> ) accounted for the most part of the total pressure drop. A theoretical model of ΔP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rp</sub> was derived based on Bernoulli Equation, which can be used to predict the solid circulation rates.