CFD Simulations of coal gasification in a fluidized bed

ANDRÉS REYES; JOSÉ M. SORIA; CLAUDIA MORA BASAURE; MARIANA T. ZAMBON; GERMÁN D. MAZZA

Lyon

Congreso; XIVème Congrès de la Société Française de Génie des Procédés (SFGP2013); 2013

Societé Française de Génie de Procédés

Currently, worldwide there is an important trend towards finding different ways of environmentally friendly energy obtainment. On this basis, coal gasification is one clean technology that presents good prospects for coal use, mainly for electricity generation with a high coal conversion efficiency and low environmental impact [1]. ANSYS-Fluent 14.0 was used to simulate the experimental procedure of coal gasification in a pilot-scale fluidized bed developed by Ocampo et al. [1]. The system consists of a reactor with an internal diameter of 0.22 m and a height of 2.0 m. The coal feed is located 0.3 m above the grid. Different proportions of char and limestone were used. The simulations were performed on a 2-D unsteady system using Eulerian-Eulerian approach. The particles were assumed to be spherical and of uniform size. The Gidaspow?s drag model was selected among the different alternatives available in the software. Gunn´s model was used for evaluating the heat transfer rate between gas and granular phases. Heat losses through the walls were also evaluated by using heat transfer coefficients suggested in the literature [2]. Heterogeneous reactions of gasification and combustion have been programmed in C++ and the solution algorithm was coupled to the CFD software. This work presents the reactor outlet gas composition calculated by CFD and compares these values with experimental data reported by Ocampo et al. [1] and with results obtained by Armstrong et al. [2] using also CFD. In Armstrong´s work the yield of the volatile products released by pyrolysis was determinated by using a correlation which estimate the gaseous products based on proximate analysis. In our case, new effective stoichiometry coefficients were determined by adjusting the final composition of the mixture in the exit stream. The results of our study are in good agreement with the experimental data and show an improvement with respect to those published by Armstrong et al., validating thus the new CFD simulation. 1. Ocampo, A., Arenas, E., Chejne, F., Espinel, J., Londoño, C., Aguirre, J. and J.D.Perez, 2003, An experimental study on gasification of Colombian coal in fluidised bed. Fuel 82, 161-164. 2. Armstrong, L.M, Gu, S. and K.H. Luo, 2011, Parametric Study of Gasification Processes in a BFB Coal Gasifier. Industrial & Engineering Chemistry Research 50, 5959?5974.