(437a) Uniform Vs. Non-Uniform Aeration in Vertical Standpipes of Group-a Materials

Standpipes are an essential component to circulating fluidized bed systems. Standpipes are one of the only components of a circulating fluidized bed system that adjust their height and pressure build automatically to balance the pressure drop along the rest of the circulating loop. In standpipes with Group A solids, proper aeration is necessary to maximize standpipe pressure build, slide valve ∆P, and solids flux. Often, standpipes of Group A solids are aerated non-uniformly, with more air dispersed at the bottom of the standpipe to account for higher pressures in this region. However, experimental data shows non-uniform aeration may be disadvantageous. Data collected in a 6-in diameter, 36 ft long vertical standpipe at PSRI shows that solids flux is not significantly changed between uniform and non-uniform aeration conditions, but factors such as standpipe stability, pressure drop above the slide valve (or other solids flow restriction), and local ∆P/L measurements are significantly altered when aerated non-uniformly compared to uniformly aerated standpipes. These findings are valuable for the operation of standpipes with Group-A solids in circulating fluidized bed systems.