The impact of radiation on gas combustion modeling for a Kraft recovery boiler

摘要

The Computational Fluid Dynamics (CFD) has been used recently to develop comprehensive models to study and represent the largest possible number of physical and chemical process inside the equipment. The objective of present work is to evaluate two different numerical radiation method to simulate a Kraft recovery boiler by a comprehensive model on the commercial CFD code for the homogeneous combustion of the volatiles released from black liquor pyrolysis. The model considered the turbulent flow represented by the SST, and the gaseous homogeneous combustion of the volatiles CH4 and CO by the EDM. The radiation was evaluated discussing no radiation, P1 Model and Discrete Transfer Model. As an additional result, the black liquor drops trajectories were calculated for a representative number of particles by one way coupling using the Ishii-Zuber drag particle model without any influence on the continuous phase. A detailed discussion about the radiation numerical methods is presented to pave the preliminary work aiming to reach the complete black liquor combustion with drying, devolatilization, pyrolysis and char combustion. The full discussion of the temperature and chemical composition profiles indicates several insights for better operational conditions.