电解金属碎锰电渣重熔脱硫的基础研究

Electrolytic manganese metal scrap would be created during manganese electrolytic process. Since the manganese metal scrap has a higher sulfur content, it cannot be used in the industrial production without further treatment. As a result, China, as the world’s largest producer of the electrolytic manganese, suffers billions of dollars in losses every year. In order to improve the value of the manganese metal scrap, electroslag remelting technology with a water-cooled non-consumable electrode has been employed to reduce the sulfur content in the manganese metal scrap. In the present work, we would focus on the thermodynamics and kinetics of the desulfurization of the manganese metal scrap under the action of an alternative electromagnetic field, and the evolution rule of the slag-manganese sulfur partition ratio, and finally try to reveal the transport behavior of the sulfur between the molten slag and the molten manganese. We first plan to measure the activity of the sulfur and oxygen in the molten manganese based on 60% CaF2 - (40-x)% Al2O3 - x% CaO (mass%) slag system. The computational models of the sulfur capacity and the slag-manganese sulfur partition ratio are then developed. The influences of the compositions of the slag, content of MnO, and oxygen partial pressure in the atmosphere would also be explored. According to above researches, the desulfurization performance induced by the molten slag and the gas would be revealed, and the quantitative relation between the addition amount of the aluminum and the slag-manganese sulfur partition ratio could also be found. Besides, in order to establish the three-comprehensive comprehensive mathematical model of desulfurization of the manganese metal scrap in the electroslag remelting process, a visual physical model experiment would be used to study the formation, grow up, oscillation and falling of the manganese droplet. The variation of the sulfur content distribution in the slag and the manganese then can be predicted by using this model. The present work would afford a theoretical foundation for the electroslag remelting process of the electrolytic manganese metal scrap, which is desired to yield a refined manganese with low-sulfur and low-carbon, and the production of the high-purity manganese.

电解金属锰过程中产生部分含硫量高的碎锰，无法直接用于工业生产，作为世界上产量最大的电解锰生产国，中国因此每年损失上亿元。为提高碎锰利用价值，本项目拟采用水冷非自耗电极电渣重熔对碎锰进行脱硫，通过对交变电磁场作用下锰液电渣脱硫反应的热力学和动力学研究，阐明碎锰电渣脱硫过程中渣锰间硫分配比的演变规律，揭示硫在渣锰两相间的迁移行为。基于60%CaF2-(40-x)%Al2O3-x%CaO(mass%)渣系，测定锰液中硫、氧活度，建立电渣硫容量、渣锰间硫分配比计算模型，探索渣系组分、MnO含量和气氛氧分压对渣锰间硫分配比的影响，揭示熔渣脱硫和气化脱硫规律，掌握加铝量与硫分配比之间的定量关系。利用可视化物理模拟实验观察交变电磁场作用下锰液滴的形成、长大、振荡及沉降，建立碎锰电渣重熔脱硫过程三维非稳态全耦合数学模型，预测硫在渣锰两相中浓度随时间的变化。研究将为精准控制碎锰电渣重熔过程奠定理论基础。

电解金属锰过程中产生部分含硫量高的碎锰，无法直接用于工业生产，作为世界上产量最大的电解锰生产国，中国因此每年损失上亿元。为提高碎锰利用价值，本项目建立了碎锰电渣脱硫热力学模型，探究了渣系组分、MnO含量和气氛氧分压对渣锰间硫分配比的影响，掌握了电渣熔渣脱硫和气化脱硫规律，获得了还原剂添加量与硫分配比之间的定量关系。基于碎锰电渣脱硫热力学模型，建立了碎锰电渣重熔脱硫过程三维非稳态全耦合数学模型，揭示了重熔过程中电磁场、焦耳热场、渣金两相流动、传热以及硫在渣锰两相中再分配的规律。利用建立好的数值模型，多因素综合优化水冷电极直径与结晶器内径之比、水冷电极冷却水流量、碎锰添加速率、重熔电流和渣厚等结构和操作参数，并进行了工业实验。研究结果表明，在空气气氛下，使用含Na2O电渣，搭配水冷铜电极电渣重熔电解金属碎锰，并添加镁钙合金时，可有效脱除金属锰中的硫元素，重熔电渣锭中的平均残余硫含量为0.0174%，对应的脱硫率为85.62%。炉渣中Na2O含量越高，渣的硫容量、CaO活度和Na2O活度的提高，其脱硫效果越好。Na2O含量高于10.44%时，Na2O促进脱硫主要通过提高渣的硫容量和Na2O活度，低于10.44%时是通过提高渣的硫容量和CaO活度。因此，炉渣中Na2O含量不应超过10%，以确保炉渣的高脱硫能力、流动性和低挥发性。含Na2O渣搭配镁钙合金脱氧剂可以在有效脱硫的同时，减少电渣锭的氧含量。终渣中11.73%的MnO证明，镁钙脱氧剂虽然可以还原部分MnO，但是空气气氛下，高温锰液依旧被其被严重氧化，提高了熔渣的氧化性，并加重了锰损失。因此在保护气氛下进行电渣重熔电解碎锰是更好的选择。随着电渣重熔过程的进行，锰熔池氧化加剧，熔渣池的MnO含量逐渐升高。在采用含Na2O渣电渣重熔电解碎锰时，电渣重熔进料前期，渣中MnO含量较低时，可以采用较小的电流，在脱硫的同时减少锰液的氧化，在电渣重熔后期，增大电流，以在熔渣中MnO含量较高时，提高渣/锰硫分配比，保证电渣锭整体较好的脱硫效果。