铝酸钠对铬铁矿无钙焙烧过程中铬氧化的影响

Effect of sodium aluminate on chromium spinels oxidation in chromite lime-free roasting process

研究Na_(2)O·Al_(2)O_(3)与铬尖晶石及铬铁矿的氧化焙烧反应行为,揭示Na_(2)O·Al_(2)O_(3)对铬氧化的影响。结果表明:Na_(2)O·Al_(2)O_(3)与MgO·Cr_(2)O_(3)的氧化焙烧过程中,MgO·Cr_(2)O_(3)中仅有约50%的铬被氧化转化为Na_(2)CrO_(4),其余的铬转化为含铝尖晶石Mg(CrAl)O_(4)。Mg(CrAl)O_(4)在铬铁矿氧化焙烧条件下很难与Na_(2)O·Al_(2)O_(3)进一步反应。Na_(2)O·Al_(2)O_(3)与铬铁矿氧化焙烧进一步证实了Na_(2)O·Al_(2)O_(3)不能与部分铬尖晶石充分反应,从而揭示了传统铬铁矿无钙焙烧生产铬盐过程中铬氧化转化率低的原因。根据实验结果,提出了一种消除Na_(2)O·Al_(2)O_(3)对无钙焙烧过程影响的新策略,即在炉料中增加Na_(2)CO_(3)的配量以满足形成Na_(2)O·Al_(2)O_(3)的需要,新策略可使铬氧化率提高至近100%。本研究更新了人们对铝酸钠在铬铁矿无钙焙烧过程作用机理的认识,为开发高效清洁的铬盐生产技术提出了新思路。

The reaction between Na_(2)O·Al_(2)O_(3) and chromium spinels or chromite in the roasting process was systemically investigated to reveal the effects of Na_(2)O·Al_(2)O_(3) on chromium oxidation.The results of Na_(2)O·Al_(2)O_(3) roasted with MgO·Cr_(2)O_(3) illustrate that only about 50%of the chromium in MgO·Cr_(2)O_(3) can convert into Na_(2)CrO_(4),while the remaining chromium converts into an Al-bearing spinel Mg(CrAl)O_(4).Mg(CrAl)O_(4) is found to be difficult to further react with Na_(2)O·Al_(2)O_(3).The oxidative roasting of Na_(2)O·Al_(2)O_(3) with chromite further confirms that Na_(2)O·Al_(2)O_(3) cannot fully react with some chromium spinels,which reveals the cause of the low chromium oxidation rate in the traditional chromite lime-free roasting process.Based on the experiment results,a strategy for eliminating the impacts of Na_(2)O·Al_(2)O_(3) in the lime-free roasting process was proposed,in which adding more Na_(2)CO_(3) for forming Na_(2)O·Al_(2)O_(3) is considered.The chromium oxidation rate can rise close to 100%with the new strategy.This study contributes to better understanding the chromite lime-free roasting process and provides a new idea for developing the chromate salts manufacturing process more efficiently and cleanly.