The　conversion　of　KCl　to　K2SO4　(potassium　sulfation　process)　significantly　affects　ash　deposition　and　corrosion　in　biomass-fired　furnaces.　Potassium　sulfation　has　been　previously　estimated　by　a　detailed　gas-reaction　chemistry　with　a　simple　hypothesis　that　potassium　vapor　condenses　in　a　single　step.　In　this　study,　a　detailed　aerosol　dynamics　model　is　proposed　to　replace　the　single-step　model　of　potassium　vapor　condensation,　which　is　coupled　with　the　detailed　gas-reaction　chemistry　of　K-S-Cl　to　predict　the　potassium　sulfation,　particle　size　distribution,　and　K2SO4/KCl　ratio　of　different　particle　sizes.　The　improved　model　shows　good　consistency　on　the　sulfation　rate　and　aerosol　formation.　The　comparison　between　the　calculated　and　experimental　results　approves　the　non-negligible　promotion　of　aerosol　formation　on　KCl(g)　sulfation.　The　sulfation　and　aerosol　formation　are　calculated　at　varied　SO2　concentrations　(100-1000　ppm)　with　other　initial　compositions　of　100　ppm　KCl(g),　5%　O2,　10%　H2O,　12%　CO2,　and　balanced　N2.　The　modeling　results　show　that　the　mass-based　particle　size　distributions　under　different　cases　are　generally　unimodal.　With　the　increase　of　the　SO2　concentration,　the　particle　size　distribution　shifts　toward　a　larger　scale　because　of　the　intensified　conversion　from　KCl　to　K2SO4.　The　increase　of　K2SO4(g)　partial　pressure　in　flue　gas　advances　the　homogeneous　nucleation　at　a　higher　temperature,　consequently　causing　a　longer　time　for　particle　growth.　Furthermore,　the　nucleation　and　condensation　of　K2SO4(g)　significantly　promote　the　transformation　from　KHSO4(g)　to　K2SO4(g),　causing　an　accumulation　of　K2SO4　in　the　solid　phase　and　thereby　an　increased　sulfation　rate.　©　2020　American　Chemical　Society.