Solids flow patterns in large-scale circulating fluidised bed boilers: Experimental evaluation under fluid-dynamically down-scaled conditions

This work aims at gaining novel knowledge of the mechanisms governing the solids flow pattern in the furnace of large-scale Circulating Fluidised Bed (CFB) boilers. A fluid-dynamically down-scaled unit resembling an existing 200-MWth CFB boiler was built and validated against full-scale data. The extensive experimental campaign showed, among others, that the presence or absence of a dense bed governs the entrainment of solids from the bottom region of the furnace, and that the back-flow of solids at the exit region is negligible at low gas velocities although it quickly becomes significant with an increase in gas velocity. Thus, it is shown that the estimation of the external solids flux by the top flux in the furnace is not generally valid. (C) 2020 The Authors. Published by Elsevier Ltd.

Automated summary

This study aims to explore the mechanisms of solid flow pattern in large-scale Circulating Fluidised Bed (CFB) boilers. Through experiments, it was found that the presence or absence of a dense bed at the bottom of the furnace significantly affects the entrainment of solids, while the back-flow of solids at the exit region is negligible at low gas velocities but becomes significant with higher gas velocities. The estimation of external solids flux based on top flux in the furnace may not always be valid.