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.
Highlights
Municipal solid waste (MSW) emergence is increasing worldwide and is predicted to grow further in the future.[1]
Nitrogen oxides (NOx) are of significant concern because they act as an acid rain precursor and in the formation of photochemical smog.[5]
Sulfur and chlorine have been shown to limit or catalyze the further oxidation of CO29,30 and interact with NOx chemistry by their impact on the formation of H, O, and OH radicals.[31−33] They are involved in joint reaction pathways, nitrosyl chloride formation,[34,35] and reactions between sulfur oxides (SOx) and NOx species.[36]. These findings suggest that the mathematical description of the gas phase in WtE plants should include those species
Summary
Municipal solid waste (MSW) emergence is increasing worldwide and is predicted to grow further in the future.[1]. For the kinetic rate estimation, different approaches are proposed.[11] Examples are the nonlinear least squares algorithm,[12] the Avrami−Eroffev equation,[13] and the modified integral Coats−Redfern method for non-isothermal reaction conditions.[14] Typically, the reaction parameters are determined for a specific waste sample or material, such as juice cartons, wood type, or paper quality Their decomposition is described by a global heterogeneous decomposition step and global cracking or decomposition pathways, including tar, gases, and char.[11] This approach is widely used for MSW12−20 but lacks the flexibility to describe and interchange the solid fuel composition to predict changes in released gas and tar species compositions and emission precursors as a function of varying waste streams. Before the paper is concluded, the limitations and potentials of the presented approach are discussed
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