In this paper, we investigate multi-phase reacting flow in a coal-fed entrained flow gasifier using large-eddy simulations and Reynolds-averaged Navier Stokes models, respectively. An axial-flow type lab-scale gasifier is investigated. The simulations are performed using a Lagrangian-Eulerian method in which the coal particles are modeled using a Lagrangian approach and the gas phase is solved using an Eulerian approach. We compare the performance of LES and RANS results. The coal particle models include devolatilization, char consumption that uses heterogeneous chemistry and two-way coupling of mass, momentum and energy with the surrounding gas phase. The gas phase combustion is modeled using homogenous chemistry and the effect of turbulence on combustion and gasification is modeled using a partially stirred reactor approximation. Results show that LES captures the unsteady flow structures inside the gasifier. We show that modeling the unsteady mixing is critical to the accurate predictions of the gas phase species and carbon conversion in these gasifiers. (C) 2012 Elsevier Ltd. All rights reserved.