2025 AIChE Annual Meeting

(89g) Issues and Solutions in Deep Fluidized Bed Startup

Authors

Francisco Sanchez Careaga - Presenter, Western University / Institute for Chemicals and Fuels from Alternative Resources (ICFAR)
Surya Karri, Particulate Solid Research, Inc.
Ted Knowlton, Particulate Solid Research, Inc.
Allan Issangya, Particulate Solid Research, Inc
A smooth startup at the beginning of a turnaround maintenance cycle is one of the key factors in successfully operating deep fluidized beds or standpipes. In deep beds, startup issues can arise due to the humidity of freshly loaded fluidized material or compaction after loading. These issues stem from gas permeability through initially packed beds or standpipes. These permeability challenges can lead to the formation of large voids (bubbles) that suddenly move through a stagnant bed, potentially damaging the unit or its components (such as baffles, grids, and sheds).

The fluidized bed used in this study consists of a main vessel with a diameter of 7-ft (2.13 m) and a height of 26-ft (7.92 m), a standpipe with a diameter of 3-ft (0.91 m) and a height of 64-ft (19.50 m), and a riser that is 1-ft (0.30 m) in diameter and 96-ft (29.26 m) tall. The bed is equipped with multiple differential pressure transducers (Honeywell and Rockwell) to monitor density in the three sections of the fluidized bed: the main vessel, standpipe, and riser.

This research presents examples of startup challenges in tall, fluidized beds, their consequences, and strategies to address stagnant sections during startup. Specifically, the study explores methods for mitigating startup issues in deep fluidized beds containing Geldart Group A powders by introducing additional aeration ports. These ports are activated only during startup and are switched off once the bed or standpipe is fully fluidized. Additionally, the findings suggest that a fluidized bed can sometimes operate with a partially plugged plenum, but the issue may not be fully resolved until all solids are drained from the system.