Abstract
The NOx reduction in the iron ore pelletizing process becomes an important environmental concern owing to its role in the formation of photochemical smog and acid rain. Thus, it is essential to develop new technologies for reducing NOx emissions in order to contribute to the cleaner production of pellets. In this paper, NOx reduction by advanced reburning ingrate-rotary kiln for oxidized pellet production was performed on a laboratory-scale gas kiln. Temperature and NH3/NOx molar ratio (NSR) were the key factors affecting the reduction of NOx. A better denitrification effect can be obtained on flus gas with higher initial NOx concentration, at temperature = 900 °C, NSR = 1.2, and reaction time exceeds one second. NOx reduction rate had reached 55–65% when the initial NOx concentration was above 400 ppm, and exceeds 70% when the initial NOx concentration was around 680 ppm. Urea solution has the best denitrification effect compared with NH3·H2O and NH4HCO3 solution. As for additives, the denitrification effect of the vanadium-titanium catalyst was better than that of ethanol and NaCl, while NaCl plays a promotive role at low NSR. Finally, a series of denitrification measures that include advanced reburning technology for achieving NOx ultra-low emission in the oxidation pellet production was proposed.
Highlights
IntroductionIron ore pellets are a main iron-bearing burden for the blast furnace ironmaking process [1,2]
Iron ore pellets are a main iron-bearing burden for the blast furnace ironmaking process [1,2].Because of its good metallurgical properties and low energy consumption in the production process, pellets can increase production, save coke, improve technical and economic indexes of ironmaking, reduce hot metal cost and improve economic benefits when applied to the blast furnace ironmaking process, as a consequence, it has been developed rapidly
The advanced reburning of in grate-rotary kiln needs further study. The objective of this present study was to investigate the influences of temperature, NSR, and other factors on NOx reduction and ammonia slip, by advanced reburning; as well as to optimize the operating parameters of the grate-rotary kiln for the better development of pellet production, and proposes the mechanism or the most rational operating technology that contribute to a further reduction in the
Summary
Iron ore pellets are a main iron-bearing burden for the blast furnace ironmaking process [1,2]. Because of its good metallurgical properties and low energy consumption in the production process, pellets can increase production, save coke, improve technical and economic indexes of ironmaking, reduce hot metal cost and improve economic benefits when applied to the blast furnace ironmaking process, as a consequence, it has been developed rapidly. With the increasingly strict environmental protection requirements, China has formulated a series of emission standards for iron and steel enterprises, forcing pelletizing plants to do corresponding work in environmental protection. Processes 2020, 8, 1470 the emission targets, NOx emission has become a restriction factor in the development and production of pelletizing plants because of its high removal cost and complex process [8,9,10].
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