Iron ore – coke nut interaction and behaviour during conveyor belt transportation and discharge: A DEM modelling study
ABSTRACT
Ironmaking blast furnace (BF) operation and control is quite a challenging task due to the “black box” nature of the process. The difficulty is aggravated by the fact that the overall performance of the furnace is influenced by both in-furnace (four phase system interactions) and out-of-furnace (burden material delivery, interactions and characteristics) processes, which are fairly linked. However, the difficulty can be mitigated through application of empirical knowledge, appropriate measurements and numerical modelling throughout the chain system. One of the main BF critical control parameters is gas distribution in different zones of the shaft. BF charging system control has a direct influence on burden permeability and controls gas distribution in the lumpy zone (belly to throat region). Depending on the program and philosophy for a particular furnace operation with a conveyor belt charging system, burden material can be batched as single material components along the conveyor belt or layers of two or more different materials layered on top of each other. With the later scenario, mixing, segregation and material consolidation, typical of non-cohesive granular material, is inevitable. Mixing and segregation occurrences, quantification of phenomena and overall performance of such burden material on the conveyor belt and the subsequent discharge to the receiving hopper are poorly understood. Understanding of the fore-mentioned characteristics will aid in the understanding of time-varying composition as well as facilitate a better estimation of radial variation in burden chemistry and physical properties of delivered burden materials. This study presents a discrete element method (DEM) modelling study of iron ore – coke nut interaction and behaviour during conveyor belt transportation and discharge into a hopper. Detailed study of the material flow patterns has been presented in the form of sectional cross plots and results obtained are useful for understanding materials behaviour, interactions, mixing and segregation characteristics of the flow. The results provide a basis for further development, redesign and reengineering of charging system with ultimate objective of achieving improved burden distribution at furnace top and thus optimizing chemical reactions, heat and mass transfer between solids, liquids and gases.
Key words
DEM, Blast furnace, Burden distribution, mixing, segregation