Bed-Wall Frictional Loss in a Bubbling Bed with Horizontal Flow of Solids

The establishment of a horizontal fluidized solids flow is a feature present in dual-fluidized bed systems with at least one reactor operated under bubbling conditions. Frictional loss between horizontally-flowing bed solids and reactor walls is a crucial aspect of reactor design since this loss limits the horizontal flow rate within the system.

The present study aims to develop a description of the bed-wall friction for bubbling beds with a horizontal flow of solids. This work uses experiments under ambient fluid-dynamically down-scaled conditions since these provide good operational flexibility and the possibility of implementing measurement techniques for detailed flow monitoring while allowing scale-up of the results to large-scale hot conditions. Bed material of Geldart-B type with a particle density of 8770 kg/m³ and a mean size of 125 µm was used. The fluidized bed used is operated under bubbling conditions and consists of a closed horizontal loop configured to force a horizontal circulation of solids which can be controlled. For this purpose, the horizontal loop consists of two sections that are operated independently: a relatively small conveying section (forcing the solids to flow horizontally) and a transport section (through which the horizontal flow of solids is returned to the conveying zone). The transport section has an average length of 1.12 m, which scales up to 9.35 m at 850 ⁰C conditions. The system is equipped with in-bed pressure probes to sample pressure drop along segments of the transport section, which is assumed to represent the frictional pressure drop. Additionally, the horizontal solids velocity established was measured through the magnetic solids tracing technique. Variations of conveyed solids flow (u₀/u_mf within 3–100), channel width (0.04–0.12 m, scaling up to 0.33–1 m), and bed height (0.08–0.1 m, scaling up to 0.67–0.83 m) are used to parametrize the results.