Surrogate Reaction Mechanism for Waste Incineration and Pollutant Formation

Abstract

The incineration of municipal solid waste (MSW) is an attractive technology to generate thermal energy and reduce landfill waste volume. To optimize primary measures to ensure low emission formation during combustion, numerical models that account for varying waste streams and their impact on nitrogen oxide (NOx) formation are needed. In this work, the representation of the fuel by surrogate species is adopted from liquid fuel and biomass combustion and applied to solid waste devolatilization and combustion. A surrogate formulation including biomass components, protein, inorganics, and plastic species is proposed, and a comprehensive description of the heterogeneous and homogeneous reactions is developed. The presented work combines and extends available schemes from the literature for woody and algae biomass, coal, and plastic pyrolysis. The focus is set on the prediction of fuel NOx and its precursors, including cyclic nitrogen-containing hydrocarbons. Additionally, the interaction of NOx with sulfur and chloride species is accounted for, which are typically released during the devolatilization of MSW. The model allows for predicting thermogravimetric analysis measurement of waste fractions and different waste mixtures. The proposed kinetic mechanism well reproduces NOx formation from ammonia and hydrogen cyanide and its reduction under selective non-catalytic reduction conditions. The chemical model is successfully applied to predict the released gas composition along a grate-fired fuel bed using a stochastic reactor network.