One step kinetic model of coal pyrolysis for cfd applications

This work’s aim is the development of a simplified kinetic model for coal devolatilization, suitable for CFD applications. The detailed model of coal devolatilization, already developed and tested against a very large set of experiments and conditions, is too large to be easily implemented and used inside a CFD code. An automatic procedure is developed to estimate the kinetic parameters and stoichiometric coefficients of a One Step model. An optimization technique manages to minimize an objective function which measures the distance between the simple one step kinetic mechanism and the results of a detailed model for coal devolatilization. One of the important features of this approach is that, thanks to the optimizer, it is possible to easily calculate specific rate parameters for each type of coal. Moreover the one step model, despite its simplicity, is able to characterize not only the coal consumption but also the relative yields of gaseous species (H2O, CO2, H2, HCN, H2S, H2, C2H4), tar species and solids species. The coal database includes 13 coals of different elemental composition, from lignite to anthracite. The agreement of the one step model with the detailed model of coal volatilization is satisfactory for both evolution rates and cumulative values. Moreover it is important to note that the proposed model, being based on the detailed model, is predictive and only needs the coal elemental composition (coal rank) as an input. A correlation for the distribution of the nitrogen and sulfur compounds into solid, tar and gas phases is also proposed.