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生物質替代焦粉鐵礦石燒結過程中的堿金屬遷移行為

Migration behavior of alkali metals in an iron ore sintering process with the substitution of biomass for coke breeze

  • 摘要: 通過揮發–冷凝實驗裝置進行小型燒結實驗,運用X射線熒光光譜(XRF)、掃描電鏡–能譜儀(SEM–EDS)及電感耦合等離子體發射光譜儀(ICP–OES)等分析檢測手段,結合Factsage熱力學模擬,對比研究了以木炭和焦粉為燃料,配加含鐵粉塵的鐵礦石燒結過程中,床層堿金屬隨煙氣揮發遷移的規律、燒結前后的堿金屬脫除率以及工藝措施對堿金屬脫除的影響。結果表明,K相對于Na更容易被脫除,揮發至煙氣中的堿金屬化合物主要是KCl,其次為NaCl。增加燃料配比促進了堿金屬元素的脫除;在燃料配比相同的條件下,木炭燒結的堿金屬脫除效果不及焦粉燒結。燒結過程中,排入廢氣中的堿金屬化合物被下部混合料層大量捕獲、吸附,下部床層內捕集的堿金屬氯化物促進了堿金屬的氯化脫除。添加CaCl2后,以木炭為燃料時K和Na的脫除率高于焦粉工況,且產物中K和Na的含量較低。配合氯化脫除工藝將生物質應用于鐵礦石燒結是燒結生產發展的可行方向。

     

    Abstract: Iron ore sintering is a process in which iron ore powder, flux, iron-bearing dust, solid fuel (such as coke powder), and return fines are mixed in a certain proportion, granulated, and then processed into agglomerates by high-temperature generated by solid-fuel combustion, which is an important process prior to blast furnace ironmaking. The iron ore sintering process is an important emitter of atmospheric particles in which alkali metal elements in a sinter bed contribute to the formation of fine particles during combustion, aggravating particulate emissions. Using biomass materials such as charcoal to replace coke in the sintering process can significantly alleviate the emission of both greenhouse gases and pollutants. However, owing to the high content of alkali metals in biomass and their poor combustion characteristics, alkali-metal-related problems inevitably arise. In this study, a small sintering experiment was conducted in a volatilization condensation test facility and analyses were performed based on data obtained by X-ray fluorescence spectroscopy, scanning electron microscopy energy dispersive spectrometer, and inductively coupled plasma-atomic emission spectrometry followed by thermodynamic simulation. The purpose of these analyses was to investigate the laws associated with alkali metal migration and enrichment, removal rate of alkali metal elements, and influence of technological measures on removal process in iron ore sintering using charcoal and coke as fuel with iron-bearing dust added. The results show that K is easier to remove than Na, and the alkali compounds volatilized into a flue gas mainly contain KCl with small amount of NaCl. With the same fuel mass fraction the removal rate of alkali metal in the sintering process using charcoal as fuel is less than that using coke. As the alkali metal compounds in the downstream flue gas migrate, they collide with the raw material particles because of the inertial effect. In addition, owing to the low temperature of the raw materials in the low bed, alkali metal compounds tend to condense and deposit on the particles’ surface. During the sintering process, a large number of alkali metal compounds discharged into the waste gas are trapped and absorbed by the low bed, and the alkali metal chloride accumulated in the low bed promotes the removal of chloride from the alkali metal. With the addition of CaCl2, the removal rate of K and Na when using charcoal as fuel is higher than that using coke. Accordingly, the content of K and Na in sintering products with charcoal as fuel is lower than that using coke. The use of biomass as fuel in iron ore sintering in combination with chlorine removal process is feasible and has good prospects.

     

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