A multi-scale compartmental model for simulation of thermal and gas composition profiles on waste layers in grate-fired furnaces

To establish more advanced combustion control in industrial Waste-to-Energy plants, models are required, that combine low computation demand with sufficient accuracy. In this work, a multi-scale compartmental model is presented, that enables simulation of heat generation and gas compound release from a combusting waste layer in a typical grate furnace. The model takes inputs measurable at the industrial scale, and avoids features that are considered less essential. Time-Travelling Reactive Cells (TTRCs), representing unit volumes of the waste layer, stepwise advance the waste as lumped solid spheres, applying shrinking-core-type solid-gas kinetics to simulate the release of CO, H₂O, HCl, and H₂S under strong limitation by mass transfer of O₂. The gas phase in each TTRC, well-mixed at high temperature and containing a large excess of O₂, enables instant oxidation of CO to CO₂ and H₂S to SO₂. In its current state, the model is valid for the case of incineration only. Initial results confirm correctness of the numerical calculations internal to the model, and suggest adequate level of accuracy for future industrial use. Comparison with data from the literature, although limited in availability and not always representative of actual conditions in industrial furnaces, also yields reasonable agreement with regard to temperatures.