Effect of particle-tube collision frequency on material wastage of in-bed tubes in the bubbling fluidized bed combustor

Abstract

The metal wastage mechanisms and rate that occur in 1018 carbon steel used in in-bed tube of the bubbling fluidized bed combustor (BFBC) are discussed with particle-surface collision frequency around the tube. Electrostatic impact probes based on the triboelectric effect of moving particles were developed and used to measure the particle-surface collision frequency, which is one of the major parameters characterizing the material wastage of in-bed tubes in the BFBC. The distribution of the particle-surface collision frequency around the tube was affected by the location of the tube and bed height. A series of material wastage tests was carried out using 742 μm, quartz silica (SiO 2) on 1018 steel at elevated temperature (300°C) which occurs in-bed locations of BFBC. The morphologies of the specimens were examined and analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The eroded surface morphology under high particle velocity (30 m s −1) exhibited typical ductile behaviour. The maximum collision frequency around the periphery of the tube was found at 45°, 315° from the bottom centre, 0°, which was correlated with maximum material wastage rate of the specimens.