From 3D to 1D: Capturing the effect of particle clusters in downers in the fluid catalytic cracking of gasoil

•1D models tend to over predict conversion in catalytic gas-solid reactive flows.•Fully coupled DEM-LES capture the effect of clusters on the prevailing chemistry.•Two effectiveness factors related to clusters improve the 1D model predictions.•The reactions where gasoil participates are the most affected by clusters. The effect of particle clusters on the chemical performance of a downer reactor during fluid catalytic cracking of gasoil is investigated by performing several 4-way coupled reactive 3D Discrete Element Method - Large Eddy Simulations (DEM-LES) in OpenFOAM. A one-meter-long cylindrical downer was used as a canonical case to analyze the dynamics of particles via 3D DEM-LES. A fluid mesh of 7×106 hexahedral cells sufficed to meet the y+