Experimental and numerical investigation of the dynamics of loop seals in a large‐scale DFB system under hot conditions

Abstract

The dynamics of the loop seals in a large‐scale dual fluidized bed (DFB) system is investigated as a function of variations in the flux of the bed material through the seal and changes in the bed material density. These investigations are performed numerically with a computational fluid dynamics (CFD) model and experimentally for the loop seals of the Chalmers 2–4 MWth DFB gasifier. Both experiments and simulations show that more of the aeration gas leaves the loop seal in the direction of the solids when a low‐density bed material (silica) is used rather than a high‐density one (bauxite). The simulations also reveal homogeneous fluidization in a vertical connection to the loop seal, whereas an inclined connection yields heterogeneous fluidization. The minor discrepancies between the experiments and simulations with silica are attributed to particle agglomeration, and it is proposed that CFD models applied to loop seals should account for this phenomenon. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3580–3593, 2015