Validation and Application of Computational Modeling to Reduce Erosion in a Circulating Fluidized Bed Boiler

The 40 MW Strongoli power plant, located in the Calabria region of Italy, produces power from 100% biomass sources. The combustion of wood biomass, exhausted olive residues and palm kernel shells, occurs in a sand-filled, Circulating Fluidized Bed (CFB) combustor. Operational experience with the unit dates back to 2003. This paper describes the optimization of the boiler in order to minimize erosion on internal surfaces and structures. Detailed three-dimensional, transient, multiphase gas-solid flow fields were computed and are presented. Details of the complex geometry include the combustion chamber, cyclone, cyclone dipleg, seal pot, fluidized bed heat exchanger and cyclone outlet structures including suspension tubes. The gas-solid flow was computed using the commercially-available software package Barracuda, a CFD software based on a unique Eulerian-Lagrangian formulation that was essential to the success of the subject work. Both instantaneous and time-averaged results were obtained. Results were validated against operational erosion experience. The validated model, in turn, was utilized to redesign various components of the boiler, optimizing both erosion characteristics and performance behaviour of the system. The redesigned unit was commissioned in early 2012.