Abstract
Quantitative parameters of bed combustion, including the thickness of the combustion zone (TCZ), the maximum temperature of the combustion zone (MTCZ), and the bed shrinkage, were characterized through a series of sinter pot tests in transparent quartz pots. The results showed that TCZ first ascended and then descended as the sintering process proceeded. The sintering process was divided into four stages according to the variation rate of the TCZ. A “relative-coordinate” method was developed to obtain the actual reaction temperature of sinter along the height direction. With increasing the sintering temperature, the reactants transformed and entered into liquid phases. The mineral composition and microstructure of the sinter were characterized through X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. Liquid phases with greater Fe and Al contents were more likely to form acicular-like silico-ferrite of calcium and aluminum after crystallization because of the outward spread of Al, which led to a better fluidity of the liquid. An evolution mechanism of “solid-state reaction—liquid phases formation—crystallization” of the mineral phases is proposed.
Highlights
Sinter, as an important iron-containing raw material for blast furnaces, accounts for more than 70% of iron-containing raw materials
The results show that the the combustion zone (TCZ) first ascended and descended as the sintering process proceeded
The sintering process can be divided into four stages according to the variation rate of the TCZ
Summary
As an important iron-containing raw material for blast furnaces, accounts for more than 70% of iron-containing raw materials. The combustion zone (CZ) of sinter is the region where the solid-fuel combustion occurs, which results in an increase of the bed material temperature and the formation of liquid phases. The heat injected from the hot gas preheated by the upper sinter, passes down the bed, raising the ignition temperature of regions ahead of the front This process is called the self-regenerative function [9]. Numerical simulations of combustion and heat transfer simulate the homogeneous sintering process well and provide solutions for the quantitative combustion parameters These mathematical models fail to consider the high-temperature behavior of the raw material, the effect of gravity on CZ, and the shrinkage of the bed material, resulting in large discrepancies between the models and the behaviors in real sintering beds. The phases and microstructure of the sinter were characterized through X-ray diffraction (XRD) and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS); a mechanism for the evolution of the phases was proposed
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