基于床层传热的真空镧热还原氧化钐过程优化

Optimization of Sm production by vacuum La thermal reduction of Sm_(2)O_(3) based on heat transfer in the pellets bed

金属钐是生产钐钴永磁材料的重要原料,主要采用真空镧热还原法制备.金属钐的生产周期长、生产效率低,而团块填充床层的传热是影响钐还原周期的主要因素之一.本文中借助数值模拟,研究了真空镧热还原氧化钐过程中坩埚内的温度及还原反应速率的分布,并提出了工业还原炉内团块填充方法的优化方案.结果表明:团块直径的变化对床层平均还原率的影响不大;坩埚中心区域的团块反应速度慢、反应滞后,反应20 h后床层的平均还原率达到80%,但从坩埚中心至0.4R的圆柱形区域内,物料几乎未发生反应;采用床层中心区域留空的方式能够有效缩短还原周期,提高原料的利用率;以单位时间床层单位体积内的钐产量为依据,中心区域留空的尺寸为0.4R和0.7R时,能获得较大的生产效率.

Sm is an important raw material for producing Sm-Co permanent magnet,which is prepared by vacuum thermal reduction of Sm_(2)O_(3) with La.Sm has a long production cycle and a low production efficiency.The heat transfer in the pellets bed is one of the main factors affecting the reduction period.In the paper,by means of numerical methods,temperature distributions and transient reaction rate distributions in the pellets bed are studied and an optimization of Sm production by changing charge method is proposed.The results show that there is a light effect of pellet diameter on the reduction ratio.The pellets in the central region have a slow reaction rate and their reduction is delayed.The average reduction ratio reaches 80%after a soaking time of 20 h,whereas the pellets in the central region<0.4R reduction reaction barely occurs.The method of leaving the central area of the bed empty can effectively shorten the reduction cycle and improve the utilization ratio of raw materials.The optimal size of the empty central region is between 0.4R and 0.7R based on Sm yield per unit volume and unit time.