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Research of Intensified Oxidative Roasting Process of Chromite Ore

Author: WangJunE
Tutor: ZhouQiuSheng；LiuGuiHua
School: Central South University
Course: Non-ferrous metallurgy
Keywords: Chromite Calcium roasting Mechanism Additive Strengthen
CLC: TQ136.11
Type: Master's thesis
Year: 2011
Downloads: 67
Quote: 0
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Abstract


Calcium roasting method is based on the the chromite as raw materials to produce chromium salt technology development direction, but backward chromium salt production in the country more than 95% of calcium roasting process, a handful of calcium roasting plant in the actual production process encountered many problems: chromium oxidation slow (~ 2h), chromium oxidation rate is low (lt; 76%) as well as prone to the phenomenon of ring formation. In order to strengthen chromite calcium oxidation roasting process to further improve the reaction mechanism of the chromite calcium roasting system to find out, in theory, under the guidance of an additive to promote oxidative calcination reaction process, by experimental studies The optimal reaction conditions. The laboratory synthetic spinel compounds as raw materials, a more systematic study of the impact and the possible mechanism of calcium roasting system chromite impurities of iron, aluminum and silicon on the oxidation rate of Cr (Ⅲ) ore. The results show that: the chromite impurities in iron oxidation rate of Cr (III) of no significant impact. Fe2O3 FeO is oxidized obtained after the firing process and Na2CO3 reaction to produce an intermediate product NaFeO2, it still plays the role of a base in the system, so that the chromium in the oxidation reaction to proceed, the reaction rate of the oxidation process of the entire Cr (Ⅲ) compared Quick; impurities of aluminum could significantly inhibit the oxidation of Cr (Ⅲ). The main reason is that the Al2O3 and Cr2O3 and MgO reaction: in the roasting process is relatively stable, insoluble diverse and complex oxides MgO · (Cr 2 O 3) 0.5 · (Al203) 0.5. In addition, A12O3 with Na2CO3 reaction generates Na2O · Al2O3, the But Na2O · Al203 difficult to further and MgO · (Cr 2 O 3) 0.5 · (Al203) 0.5 reaction Na2CrO4; impurities in silicon can hinder the process of oxidation of Cr (Ⅲ), because when temperatures above 1173K, Na2SiO3 and Cr2O3, the oxidation reaction can be reverse, so that the generated Na2CrO4 decomposition will occur, leading to the oxidation rate of chromium reduced. Based on the oxidation reaction mechanism of chromite calcium roasting system, this paper carried out systematically chromite oxidizing roasting experimental study. The results show that: the calcined optimum reaction conditions with alkali content of 110% -120% of the theoretical amount of, and the calcination temperature was 1323K, and the reaction time was 30 min-60min; substance A is added to the system can significantly increase the rate of chromium oxide, mainly : Additive A added the amount of liquid phase of the oxidation roasting system can be significantly reduced; 1223K ~ 1323K temperature range, as the calcination temperature increased, the amount of liquid phase in the calcination system remains substantially unchanged, there are conducive to oxygen to the roasting system diffusion substance A role of the greatest degree of oxidation reaction of Cr (III) of the the chromium oxidation rate up to 98%

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CLC: > Industrial Technology > Chemical Industry > Inorganic compounds, the chemical industry of the metal elements > Part Ⅵ group metal elements in inorganic compounds > Inorganic compounds of the element chromium vice family ( VI B family) > Inorganic compounds of chromium
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