Decrease of high-carbon-ash landfilling by its Co-firing inside a cement calciner

A waste by-product from chemical industry, called high-carbon-ash (HCA), appears to be a potential alternative fuel for cement industry. However, because of different fuel characteristics, use of HCA as a fuel directly affects the performance characteristics of existing pulverized fuel fired furnaces. To achieve the aim of HCA utilisation in existing pulverized coal fired furnaces, it is significant to investigate the combustibility of HCA and then propose a comprehensive way of its utilisation. In this study, the physical and chemical properties of the HCA were investigated. A drop tube furnace was employed to test the combustibility of HCA in a pulverized furnace. After the pulverized HCA was experimentally investigated, an HCA combustion model was developed within a computational fluid dynamics (CFD) code AVL FIRE®. The CFD code was then used for the analysis. The experimentally obtained results were used to validate the numerical model. The comparison of results showed satisfactory agreement between the numerical predictions and experimental data. Finally, the validated numerical model was used to numerically study the co-firing of coal and HCA inside of a real industrial cement calciner furnace. It is suggested that no more than 30% of HCA, in thermal share, should be burned in order not to affect the rate of calcium carbonate decomposition on the calciner's outlet. The study results show that 78,408 tonnes of HCA per year could be utilised in cement production and avoid landfilling. This indicates that HCA used in cement industry and avoided from the landfill contributes to a more sustainable waste management of HCA and to a cleaner cement production.