(1. 中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083；2. 紫金礦業(yè)集團(tuán) 礦冶設(shè)計研究院，上杭 364200)
摘 要: 以實(shí)驗(yàn)室合成的尖晶石型化合物為原料，系統(tǒng)地研究鉻鐵礦無鈣焙燒體系中雜質(zhì)鐵和鋁對Cr(Ⅲ)氧化率的影響規(guī)律及其機(jī)理。結(jié)果表明：鉻鐵礦中雜質(zhì)鐵對Cr(Ⅲ)的氧化率無明顯影響；焙燒過程中FeO被氧化后得到的Fe2O3先與Na2CO3反應(yīng)生成中間產(chǎn)物NaFeO2，它在體系中仍能起著Na2CO3的作用，使鉻的氧化反應(yīng)繼續(xù)進(jìn)行，整個Cr(Ⅲ)氧化過程的反應(yīng)速率均較快；而雜質(zhì)鋁能明顯抑制Cr(Ⅲ)的氧化，其主要原因是：在焙燒過程中，Al2O3與Cr2O3和MgO反應(yīng)生成相對穩(wěn)定、難溶的多元復(fù)雜氧化物MgO·(Cr2O3)0.5·(Al2O3)0.5。此外，Al2O3與 Na2CO3反應(yīng)生成Na2O·Al2O3，但Na2O·Al2O3很難進(jìn)一步與MgO·(Cr2O3)0.5·(Al2O3)0.5反應(yīng)生成Na2CrO4。
關(guān)鍵字: 鉻鐵礦；氧化焙燒；雜質(zhì)；三氧化二鐵；氧化鋁；機(jī)理
oxidation rate of trivalent chromium and its mechanism
（1. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
2. Zijin Institute of Mining and Metallurgy, Zijin Mining Group Company, Shanghang 364200, China）
Abstract:The influences of impurities of ferrous oxide and aluminum oxide on the oxidation rate of trivalent chromium and its mechanism were systematically studied using the compounds synthesized in laboratory as the starting materials in the calcium-free oxidative roasting process of chromite ore. The results show that the impurity of ferrous oxide has little effect on the oxidation rate of the trivalent chromium. Ferrous oxide is first oxidized to form ferric oxide, and NaFeO2 is formed by the preferential reaction of ferric oxide and sodium carbonate, which can further act as the alkali and thus maintain a relatively rapid oxidation rate of trivalent chromium during the whole roasting process of chromite ore. And the impurity of aluminum oxide obviously hinders the oxidation of trivalent chromium. This is mainly attributed to the formation of the complicated insoluble compound of MgO·(Cr2O3)0.5·(Al2O3)0.5. In addition, the aluminum oxide readily reacts with sodium carbonate to form sodium aluminate which is difficult to further react with MgO·(Cr2O3)0.5·(Al2O3)0.5 to form Na2CrO4, resulting in the decrease in the oxidation rate of trivalent chromium.
Key words: chromite ore; oxidative roasting; impurity; ferrous oxide; aluminum oxide; mechanism
