Experimental investigation and numerical modeling of strength properties of iron ore sinter based on pilot-scale pot tests and X-ray computed tomography

Abstract

One of the most concerned quality in iron ore thermal agglomeration process is the mechanical strength of sinter and thus the size degradation of sinter product which occurs during transportation could be minimized. Due to the complexities of porous structure and brittle nature of sinter, it is difficult to determine their influences on the mechanical properties. Under this prospect, pilot-scale sinter pot tests have been carried out under the conditions of a wide range of coke rates. X-ray computed tomography was applied to reconstruct the sinter porous structures with the resolution of 40 µm and following simulations for obtaining the distribution of stress and displacement in the compressed sinter samples at the micro level were performed. The strength of sinter product was also experimentally evaluated by the shatter and tumbler tests at the macro level. The obtained experimental and numerical results showed that, sinters produced in the low coke rate cases have relatively large porosity and irregular structures, exhibiting more locations with high stress values including bridges with the small cross-sections and pore-shaped notches with the small fillet radius. Those sinters are more easily to be breaked at the macro scale, resulting in their smaller mean diameter and tumbler strength index compared to the sinters under the condition of high coke rates. The increase of coke rate greatly increases the maximum bed temperature in flame front, promoting the melt formation, material coalescence and densification therefore sinters with better mechanical property could be achieved.