The overall goal of this project is to find out if selective non-catalytic reduction (SNCR) technologies can be used in grate-kiln plants for NO x reduction. The technique has, to the best knowledge of the authors, never been used in this context before despite that it is commonly used in cement and waste incineration plants.A Computational Fluid Dynamic model of parts of a real grate was created and numerical simulations with a commercial code was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NO x polluted air. The simulations show promising results for SNCR with urea but not with ammonia.
Heat transfer in a random packed bed of monosized iron ore pellets is modelled with both a discrete three-dimensional system of spheres and a continuous Computational Fluid Dynamics (CFD) model. Results show a good agreement between the two models for average values over a cross section of the bed for an even temperature profiles at the inlet. The advantage with the discrete model is that it captures local effects such as decreased heat transfer in sections with low speed. The disadvantage is that it is computationally heavy for larger systems of pellets. If averaged values are sufficient, the CFD model is an attractive alternative that is easy to couple to the physics up-and downstream the packed bed. The good agreement between the discrete and continuous model furthermore indicates that the discrete model may be used also on non-Stokian flow in the transitional region between laminar and turbulent flow, as turbulent effects show little influence of the overall heat transfer rates in the continuous model.
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