废旧金属旋转偏析纯化再生机理与方法

Mechanism and method of purification and regeneration of scrap metal by rotatinal segregation

针对传统废旧金属回收方法流程长、效率低、传质慢的问题,借助水模型试验开展旋转偏析过程杂质强化去除的机理研究,为旋转偏析技术回收废旧金属提供动力学基础。试验分别通过流场可视化处理和流速的测定对溶质在废旧金属熔体中的传输进行分析,发现旋转偏析技术可以有效提高杂质原子在熔体中的传质效率,降低生长界面处杂质的传质阻力。水模型试验结果表明,旋转偏析炉内流场的循环运动模式有利于杂质向远离生长界面处运动,但在低转速条件下循环流动较弱,杂质的排除能力随着转速的增加而增加,但当转速增加到800r/min时,杂质无法有效向远结晶器端输送,不利于杂质去除;平均流速随着结晶器转速的增加而增加,结晶器转速从200r/min增加到800r/min时,各点流速平均增大2倍;流场平均流速随着结晶器浸入深度的增加而增加,结晶器转速为200r/min时,随着结晶器浸入水深的1/2增加到4/5,近结晶器液面端流速从0.02m/s增加到0.04m/s,其他各测速位点流速均有明显提高,平均流速增大1倍;流场平均流速随着结晶器直径与坩埚直径比例增大而增大,直径比从1/7增大到1/2,流场内平均流速增大了4倍左右。试验证明,适当增大转速、结晶器浸入深度以及结晶器与坩埚的直径比都能提高旋转驱动力,从而提高溶质在熔体中的传输速率,获得高效、均匀的浓度场。本研究中,在结晶器与坩埚直径比为1/3、结晶器浸入深度为4/5时,杂质的传输效果和浓度场的均匀度均较好,有利于旋转偏析过程杂质的有效脱除。在水模型基础上开展的铝熔体旋转偏析除杂研究结果表明,在结晶器转速为400r/min时,铅的去除效率最高可以达到66%,旋转偏析回收废旧金属资源可以改善传统回收方法流程长、效率低的问题,实现金属杂质的深度高效去除,满足金属资源的高值化回收利用需求。

Aiming at the problems of long process,low efficiency and slow mass transfer of traditional waste meal recovery methods,the mechanism of enhanced removal of impurities in rotational segregation process was studied by means of water model experiment,which provided a dynamic basis for recycling waste metal by rotational segregation technology.The flow field visualization and velocity measurement were used to analyze the transport of solute in waste metal melt,and t was found that the rotational segregation technology can effectively improve the mass transfer efficiency of impurity atoms in the melt and reduce the mass transfer resistance of impurities at the growth interface.The results of the water model experiment show that the circulation motion mode of the flow field in the rotational segregation furnace is conducive to the movement of impurities away from the growth interface,but the circulation flow is weak at low rotational speed.The exclusion ability of impurities increases with the increase of rotational speed.However,when the rotational speed increases to 800 r/min,the impurities cannot be effectively transported to the far crystallizer end,which is not conducive to the removal of impurities.The average flow velocity increases with the increase of the crystallizer speed.When the crystallizer speed increases from 200 r/min to 800 r/m in,the average low velocity at each point increases by 2 times.The average flow velocity of the low field increased with the increase of the immersion depth of the crystallizer.When the speed of the crystallizer was 200 r/min,the flow velocity near the llquid surface of the crystallizer increased from 0.02 m/s to 0.04 m/s with the immersion depth of the crystallizer increasing by 1/2 to 4/5,and the low velocity at other measurement sites increased significantly,and the average low velocity increased by 1 times.The average low velocity of the flow field increased with the increase of the ratio between the diameter of the crystallizer and the diameter of the crucible.The diameter ratio increased from 1/7 to 1/2,and the average low velocity in the low field increased by about 4 time..Experiments show that increasing the rotation speed,the immersion depth of the mold and the diameter ratio of the mold to the crucible can improve the rotation driving force,thus improving the transfer rate of the solute in the melt and efficient uniform concentration field.In this study,when the diameter ratio of the crystallizer to the crucible is 1/3 and the immersion depth of the crystallizer is 4/5,it has a good effect on the transport of impurities and the uniformity of the concentration field,which is conducive to the effective removal of impurities in the rotatonal segregation process.The results show that the removal efficiency of Pb can reach 66%when the crystallizer speed is 400 r/min.This proves that rotational segregation recovery of waste metal resources can solve the problems of long process and low efficiency of traditional recovery methods,achieve deep and efficient removal of metal impurities,and meet the needs of high-value recovery of metal resources.