(中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 用于鉻鹽生產(chǎn)的傳統(tǒng)無鈣焙燒過程存在鉻氧化率低的問題，嚴重影響鉻的生產(chǎn)效率和回收率。為強化鉻鐵礦氧化焙燒過程，對鉻氧化過程的動力學(xué)規(guī)律及其氧化反應(yīng)機理進行了研究。結(jié)果表明：鉻鐵礦氧化焙燒過程，鉻的氧化反應(yīng)分為初期和后期兩個階段，初期鉻氧化速率快，后期鉻氧化速率慢，在優(yōu)化條件下，鉻(Ⅲ)的氧化率可達99%以上；兩個階段鉻的氧化反應(yīng)均符合收縮未反應(yīng)核動力學(xué)模型且受表面化學(xué)反應(yīng)控制，鉻氧化反應(yīng)初期和后期的表觀反應(yīng)活化能分別為68.7和231.8 kJ/mol；反應(yīng)初期是鉻鐵礦直接與碳酸鈉和氧氣發(fā)生反應(yīng)生成鉻酸鈉，而后期則是鉻鐵礦與反應(yīng)初期生成的鐵酸鈉和氧氣發(fā)生反應(yīng)生成鉻酸鈉。
關(guān)鍵字: 鉻鐵礦；鉻酸鈉；氧化焙燒；動力學(xué)
（School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The traditional lime-free roasting process used for manufacturing chromate from chromite ore has low oxidation rate which impact the chromate production efficiency and chromium recovery rate seriously. To intensify the oxidation roasting process of chromite ore, the oxidation kinetics and its mechanism were studied. The results show that there are two stages for the oxidation roasting process of chromite ore. The oxidation reaction is very rapid in the initial stage but quite slow in the later stage. The oxidation rate of chromium(Ⅲ) in chromite ore can reach more than 99% under the optimized conditions. The whole oxidation process of chromite ore follows the shrinking unreacted core model, and the surface chemical reaction is the controlling step. The apparent activation energies of the initial and later stages are 68.7 and 231.8 kJ/mol, respectively. And the sodium chromate is produced by the reaction of chromite with sodium carbonate and oxygen in the initial stage, whereas sodium chromate is formed by the reaction of chromite with sodium ferrite formed in the initial stage and oxygen in the latter stage.
Key words: chromite ore; sodium chromate; oxidation roasting; kinetics
