Three-dimensional modelling and optimization of an industrial dual fluidized bed biomass gasification decoupling combustion reactor

Dual fluidized bed biomass gasification decoupling combustion technology, as a promising technology to realizing the highly efficient and stable combustion for high-water-containing biomass fuel and lower NOx emission, has drawn worldwide attention from researchers in recent years. In this work, a three-dimensional industrial dual fluidized bed biomass gasification decoupling combustion reactor was modelled using the reactive multiphase particle-in-cell approach, and the secondary air operating parameters concerning total secondary air ratio, upper secondary air ratio, upper secondary air height, and upper secondary air injection models of the biomass gasification combustion reactor were optimized to enhance its performance further. Results show that the biomass gasification combustion model, established and comprehensively verified by comparing the simulated values with measured data in this work, shows a good prediction accuracy of gas–solid flow, heat transfer, and biomass combustion processes. With the total secondary air ratio, the upper secondary air ratio and the upper secondary air height increase, the gas-phase entrainment effects on the axial particle concentration distribution below the upper secondary air feed port in the dense zone weakens, and the overall biomass combustion efficiency decreases. Compared with the single injection model for the upper secondary air injection, the gas-phase entrainment effects on the axial particle concentration distribution were enhanced, and the overall biomass combustion efficiency was improved when adopting the opposite injection or circular injection model. Finally, the optimal secondary air operating parameters for the biomass gasification combustion reactor were obtained from the combustion and gasification views, providing an essential theoretical reference for industrial-scale dual fluidized bed biomass gasification decoupling combustion reactor optimization, biomass gasification decoupling combustion process enhancement, and efficient biomass energy utilization.