Reduction properties of sinter with fine dispersed pores at high temperatures of 1 273 K and above

Abstract

The change in the particle size distribution of limestone and coke breeze has been investigated to determine its effects on the sintering rate, sinter quality, sinter bed heat pattern and other parameters by the use of the sintering pot test. Furthermore, the sinters produced in the sintering pot tests have been evaluated as to their reducibility at 1 273 to 1 573 K in a high-temperature reduction test apparatus. If the particle sizes of both limestone and coke breeze are simultaneously adjusted, it is possible to improve the permeability of a raw mix and control the pore size distribution of the sinter product. Simultaneous removal of a -1.0 mm fraction from the limestone and a -1.0 mm fraction from the coke breeze improves the granulation index and permeability of the raw mix, and is considered effective in shortening the high-temperature holding time in the sinter bed. Such removals also suppress the shrinkage of sinter cake, and also improve the pore network of the sinter cake to assure a uniform gas flow in the sinter bed and increase the sintering rate. Fine pores can be prevented from coalescing into coarser pores if expansion of the heat pattern in the sinter bed is suppressed. This study suggests that the number of fine pores in the sinter can be increased by reducing the small fractions of the limestone and coke breeze used in the raw mix and coalesced fine pores can increase the surface area of sinter to achieve a substantial improvement in its high-temperature reducibility.