Comparative study of gas–solids flow patterns inside novel multi-regime riser and conventional riser

Abstract

A novel CFB riser integrated with an enlarged bottom section was presented in this paper, with the aim to increase overall solids concentration, improve local flow structure and intensify gas–solids contact in the bottom region. Detailed measurements of the flow patterns indicated a multi-regime flow was achieved in this novel riser with a dense-phase bottom region and a dilute upper region. Compared with non-uniform radial profiles of solids concentration and particle velocity presented at the high-density bottom region of a conventional riser, high cross-sectional averaged solids concentration with limited radial gradient was observed in the diameter-enlarged section of this novel riser. Local flow structures in the bottom regions of both risers were also depicted. Better gas–solids contact over the conventional riser was confirmed by the analysis of transient signals and probability distribution of solids concentration. Finally, key flow features of the both risers were summarized.