Experimental and computational studies to investigate flow dynamics of Geldart A and Geldart B particles in a Circulating Fluidized Bed (CFB)

Abstract

Circulating Fluidized Bed are widely used in power industries owing to their advantageous properties like high heat-transfer, longer residence time, particle mixing and separation. Particularly, CFB technology is used in the applications such as pyrolysis, gasification, chemical looping, calcium looping, oxy-firing, and waste firing, to produce high-quality producer gas thus, allowing to meet emission limits. In a single reactor CFB, the particles are carried by the gas flow, separated using a cyclone, and returned into the riser through a gas sealing mechanism such as a loop seal or valves. The efficient design and operation of the CFB reactors depend on gas-particle flow behaviour and particle circulation rate at different process conditions.

This study addresses the dynamics flow behaviour of the Geldart A and Geldart B particles in CFB using Computational Particle Fluid Dynamic (CPFD) simulations. Sand particles ranging from 63-200 µm in size were employed as the bed material. The CPFD model was developed using the MP-PIC approach in a Barracuda virtual reactor. The CPFD model results were validated against experimental data based on the pressure sensor reading along different reactor zones. The optimal velocity for smooth circulation of the particles were identified as 1.99 m/s and 0.0531 m/s in riser and loop seal. The result illustrated that the Wen-Yu and Ergun drag model predicted the flow dynamics behaviour close to the experimental measurements of the several drag models tested. Similarly, different simulations were run at different velocities to study the flow dynamics of the bed materials. And comparison of two different model were evaluated based on particle mass flux at different zones in CFB.