| Iron ore pellets get more and more favour in modern blast furnaces, and the proportion of pellets in the burden of ironmaking becomes higher and higher, for their good intensity, equality granularity, high iron grade, fine reducibility and so on. There are three main pellet production processes: shaft furnace process, straight grate process and grate-kiln process. The grate-kiln process has the exhibited the greatest potential. One of the main problems in the grate-kiln process is ringforming, but there is few research on the ringforming of gas-heat-supply acid pellet rotary kiln.Aiming at the problem of ringforming of gas-heat-supply rotary kiln of Kunming Iron and Steel Joint Stock Limited Liability Company, this paper mainly studied the characteristic of rings in rotary kiln, such as chemical composition, mineral component, microstructure of rings and the soft-melt temperature of powder. The affecting factors of each sect of the rotary kiln by measuring the concretion intensity of powder and the soft-melt temperature of powder were also studied, and It concluded that, the ringforming of gas-heat-supply acid pellet rotary kiln is because of solid concretion of accumulated powder in the rotary kiln and liquid phase concretion only acts the assistant effect.This paper also found that the main reasons of ringforming are that too much powder, high roast temperature, high content of alkali metals and SiO2. Methods to prevent ringforming in the kiln were proposed. |
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