The　co-gasification　of　coal　and　biomass　through　fluidized　bed　gasifier　is　a　promising　technology　for　the　improvement　of　the　utilization　efficiency　of　fossil　fuels　and　the　development　of　renewable　energy.　In　this　work,　a　coarse-grained　computational　fluid　dynamics-discrete　element　method　(CFD-DEM)　simulation　is　performed　to　investigate　the　co-gasification　process　in　a　bubbling　fluidized　bed　gasifier.　The　effects　of　particle　size　distribution　and　operating　pressure　on　the　hydrodynamics,　heat　transfer,　and　co-gasification　performance　are　analyzed.　The　results　show　that　the　increase　of　sand　particle　size　distribution　(PSD)　width　slightly　affects　the　particle　concentration　distribution,　particle　residence　time　distribution,　and　co-gasification　performance.　The　heat　transfer　rate　of　convection　is　an　order　of　magnitude　higher　than　those　of　conduction　and　radiation.　At　higher　PSD　width,　the　formation　of　the　vertical　solid　temperature　gradient　at　the　bed　bottom　is　attributed　to　the　deteriorated　solid　mixing.　As　the　operating　pressure　increases,　the　bed　temperature　decreases　apparently.　In　addition,　the　variation　of　the　convective　heat　transfer　rate　dominates　the　heat　transfer　efficiency　as　the　operating　pressure　changes.　The　application　of　elevated　operating　pressure　benefits　to　the　thermal-chemical　conversion　of　blend　fuel　since　the　char　conversion　reaction　is　accelerated.　©　2022　Elsevier　Ltd