Assessment of the effect of alkali chemistry on post-flame aerosol formation during oxy-combustion of biomass

The oxy-combustion of biomass enables negative CO₂ emissions by combining subsequent CO₂ capture technology. The potassium sulfation process significantly affects deposition and corrosion in heat transfer surfaces during biomass combustion. In the present work, a detailed aerosol dynamics model coupling with the detailed gas-reaction chemistry of K-S-Cl is proposed to investigate the effect of alkali chemistry on the evolution of post-flame aerosol during oxy-combustion of biomass. According to the modelling results, the mass-based particle size distributions are generally unimodal. Changing the environment from the air (N₂ as a balance gas) to oxy (CO₂ as balance gas) has a slight effect on the particle size distribution; yet, a slight left-shift particle size distribution was observed. The difference is mainly explained by the more substantial diffusion capacity of KCl(g) and K₂SO₄(g) in N₂ than that in CO₂, indicating a bit higher heterogeneous condensation of KCl(g) and K₂SO₄(g) in a CO₂-based atmosphere. Further, the modelling results revealed that oxy-combustion significantly affects the evolution of aerosol and sulfation of KCl regardless of flue gas recirculation strategy. The wet oxy-combustion case has the largest particle size of PM_1.0, that is due to the higher concentration of water and SO₂, which increased KCl sulfation with value of ∼ 92%. The increased K₂SO₄ concentration in the flue gas causes earlier onset nucleation and prolonged the residence time for particle growth. Further ROP analysis results indicate that the reaction pathway for the sulfation of KCl via SO