CFD modelling of the flow through a grate-kiln

LKAB is an international high-tech minerals group, one of the world's leading producers of upgraded iron ore products for the steel industry and a growing supplier of industrial minerals products to other sectors. Over the last years, the swedish industry has been facing increasing governmental pressure to control and reduce pollutant emissions, one of which is nitrogen oxides NOx. The pelletizing process requires high excess air levels and high temperatures, which promotes the production of NOx. Consequently, LKAB is running several research projects with the objective to reduce NOx emissions from the company's pellet production plants, including both primary and secondary measures. This work is part of an investigation whether Selective Non-Catalytic Reduction (SNCR) is suitable for reducing NOx emissions in LKAB's grate-kiln iron ore pelletizing plant SK. The motivation of this specific research is to develop a CFD model that enhances the understanding of the aerodynamics and mixing of species inside the rotary kiln. At first, a parametric study of the pure airflow through the kiln is carried out and under certain conditions, a transient behaviour similar to that of vortex shedding is observed, with a strong dependence on momentum flux ratio between the secondary air jets. Further, the development of a preliminary coal combustion model is set out, which is in need of continued work in order to produce reliable predictions of various parameters relevant to the SNCR process. However, the effect of the combustion on the flow field is limited, indicating that the pure airflow model can be used to broadly investigate the influence of the secondary air flow.Validerat; 20101217 (root