Characteristics of combustion zone and evolution of mineral phases along bed height in ore sintering

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.

Significant influence of self-possessed moisture of limonitic nickel laterite on sintering performance and its action mechanism

“…However, when the selfpossessed moisture of limonitic nickel laterite further rises to 26 mass%, the maximum exhaust-gas temperature is dramatically lowered to 208 °C. As confirmed in previous studies [30,31], the decomposition of the abundant crystal water in limonitic nickel laterite during sintering would result in the formation of highly porous sinter, which subsequently leads to rather low heat front velocity. This adversely affects the transformation of the heat supplied by the combustion of anthracite to sinter bed in the high temperature zone and the efficient utilization of hightemperature exhaust-gas in the lower part.…”

Effective Utilization of Limonitic Nickel Laterite via Pressurized Densification Process and Its Relevant Mechanism

“…Afterward, the exhaust-gas temperature is maintained at a certain level because of the continuous water evaporation. With the further proceeding of sintering process, the exhaust-gas temperature substantially rises to the maximum value due to heat transfer and chemical reaction [44,45]. When sintering is finished, the exhaust-gas temperature is reduced gradually.…”

“…It is well known that the decomposition of extensive crystal water of limonite ores such as limonitic nickel laterite during sintering leads to the formation of high porous sinter and then rather low heat front velocity [44][45][46]. Thus, the heat generated by the combustion of anthracite cannot be effectively transferred to the sinter mixture in a high-temperature zone and the temperature of the high-temperature zone is insufficient to answer the demand of the sintering mineralization consequently.…”

Thermodynamic modelling of the lead sintering roasting process

“…Zhang et al [10] simulated the sintering process of iron ore by an unsteady two-dimensional mathematical model, which incorporated the significant physical phenomena and chemical reactions; sinter pot tests were also carried out. Wang et al [11] established a research route with sinter pot trials to characterize the evolution of the flame front and the phase chemistry along the bed height of sintering. Zhao et al [12] reported the evaluation model of iron ore properties based on the hightemperature characteristic numbers by employing fuzzy mathematics.…”

“…They proposed the application of an algorithm based on the optimization of airflow rate as the control strategy for the sintering process. Wang et al [14] reported the evolution of the flame front and the mineral phases along the bed height of sintering.…”