摘要
研究低温还原超细氧化铁粉的还原热力学。用高能球磨法获得的超细氧化铁粉,在280～400℃的温度范围内用氢气还原。对还原后的粉末进行氧含量测定并计算氧化铁粉末的还原率,研究氧化铁粉粒度、还原温度和还原时间等参数对还原率的影响。从热力学的角度,计算不同温度下的反应自由能,分析和求证400℃以下低温氢气还原氧化铁的可行性。研究结果表明Fe2O3向Fe3O4还原反应的自由能在标准状态下为负值,因此还原反应有很大的自发驱动力,反应很容易进行;而Fe3O4向Fe的还原反应的自由能为正值,说明在标准状态下不能进行,要通过调节还原气体的分压比才能使还原反应进行,因此Fe3O4向Fe的还原反应是制约氧化铁粉还原的主要环节,它与非平衡状态下的温度、气体压力和反应物的状态存在紧密的联系。超细氧化铁粉处于非常高的能量状态,可以促使Fe3O4向Fe的还原反应在400℃以下的低还原温度下得以进行。
Thermodynamic of reduction of micron-nanometre ferric oxide powder at low temperature was investigated. The powders with micron-nanometre size were obtained by high energy milling and then reduced at 280～400 ℃ with hydrogen. Oxygen in the reduced powder was determined and reduction rate was calculated, Influence of the iron oxide size and reduction temperature and time on reduction rate was found. Free energy of reductive reaction was worked out. Possibility of reduction of micron-nanometre ferric oxide powder at low temperature was analyzed and certified in consideration of thermodynamic. The results show that the free energy in standard condition of reaction from Fe2O3 to Fe3O4 is in minus value, so that the reaction will be done in a great potential force, while it is plus value when the reaction from Fe3O4 to Fe so that the reaction can not be done in standard condition. It must adjust divided pressure of the reduction gas to make the reaction free energy to be minus value for the reduction reaction to progress. The process of the reaction from Fe3O4 to Fe is a key step to control whole reduction reaction from Fe2O3 to Fe. It depends closely on temperature, gas pressure and status of ferric oxide powder in reduction reaction in uneven condition. Micron-nanometre ferric oxide powder with very high energy statue could prompt the reductive reaction from Fe3O4 to Fe to progress in a temperature lower than 400 ℃.
出处
《粉末冶金材料科学与工程》
EI
2008年第3期150-154,共5页
Materials Science and Engineering of Powder Metallurgy
基金
国家自然科学基金资助项目(50634040)
关键词
氧化铁还原
还原反应热力学
微纳米氧化铁粉
高能球磨
reduction of ferric oxide powder
thermodynamic of reduction
high-energy milling
micron-nanometre iron powder
