Enhancing circulation of particles and gases in a biomass-fueled circulating fluidized bed boiler: A pseudo-combustion case study using MFiX-PIC modeling

This study investigates a circulating fluidized bed steam boiler fueled by biomass from forest wastes in the Marmara Region, Turkey. The gas–solid hydrodynamic structure was investigated both experimentally and numerically to identify existing or potential issues using the MFiX-PIC CFD model. The circulation, facilitated by u-beams acting as impact separators, is governed by pseudo-combustion boundary conditions. The flow direction of secondary air supply nozzles is found to cause problems with water walls and circulation, with gas velocities exceeding 10 m/s. This leads to damage to the water walls and insufficient circulation. Improved hydrodynamics are achieved by adjusting the angles of horizontally positioned secondary air nozzles downward by -20°. This modification results in a slight decrease (-3.77%) in solid particle concentration in the dense phase and a significant increase (+202.69%) in the dilute phase region. Additionally, a discretization scheme study demonstrates that the hybrid composition of the van Leer and Superbee schemes yields a 55.11% faster solution than using Superbee alone and 21.03% faster than using only van Leer. The findings highlight the suitability of the MFiX-PIC model and cost-reducing modeling approaches for industrial-scale steam boiler simulations.