卢婷婷, 李荣斌, 赵洪亮, 谢明壮, 刘风琴. 铝电解槽废阴极炭块电−热耦合处理过程数值模拟[J]. 工程科学学报, 2020, 42(6): 731-738. DOI: 10.13374/j.issn2095-9389.2019.06.10.002
引用本文: 卢婷婷, 李荣斌, 赵洪亮, 谢明壮, 刘风琴. 铝电解槽废阴极炭块电−热耦合处理过程数值模拟[J]. 工程科学学报, 2020, 42(6): 731-738. DOI: 10.13374/j.issn2095-9389.2019.06.10.002
LU Ting-ting, LI Rong-bin, ZHAO Hong-liang, XIE Ming-zhuang, LIU Feng-qin. Numerical simulation of electro−thermal coupling process for spent cathode carbon block from aluminum electrolysis cell[J]. Chinese Journal of Engineering, 2020, 42(6): 731-738. DOI: 10.13374/j.issn2095-9389.2019.06.10.002
Citation: LU Ting-ting, LI Rong-bin, ZHAO Hong-liang, XIE Ming-zhuang, LIU Feng-qin. Numerical simulation of electro−thermal coupling process for spent cathode carbon block from aluminum electrolysis cell[J]. Chinese Journal of Engineering, 2020, 42(6): 731-738. DOI: 10.13374/j.issn2095-9389.2019.06.10.002

铝电解槽废阴极炭块电−热耦合处理过程数值模拟

Numerical simulation of electro−thermal coupling process for spent cathode carbon block from aluminum electrolysis cell

  • 摘要: 废阴极炭块是铝电解槽大修时产生的一种危险固体废弃物,对其进行安全处置和资源化利用的关键是深度分离其中的有价组分炭和氟化盐。采用火法工艺对废阴极炭块进行处理,明确了氟化盐的挥发温度。基于氟化盐的挥发析出性质,设计了高温热处理电阻炉,并对其传热特性、控温规律以及氟化盐有效挥发区域进行了三维数值解析。实验确定氟化物的有效挥发温度为≥1700 ℃,该温度段下其挥发率可达93.1%以上。通过模拟不同供电模式下炉内温度场的演变规律,得到:在12 V升温24 h,9 V保温12 h的供电条件下,升温阶段炉内最高温度可达2250 ℃,氟化盐理论挥发区域占比可达98%;采用逐级递减的电压供给制度可以保证1700 ℃以上温度区域维持20 h,大幅度延长了有效热处理时间,有利于废阴极炭块中炭与氟化盐的深度分离。

     

    Abstract: Spent cathode carbon block (SCCB) is considered to be a kind of hazardous waste, because it contains a large amount of soluble fluoride salts and toxic cyanides. The life of an aluminum electrolytic cell is generally 5−8 years, and the SCCB would be produced during the overhaul of the cell. Currently, most SCCBs are piled in landfills or stored for disposal in China. The unreasonable disposal of SCCBs will cause serious pollution and damage to the ecological environment, and wastage of valuable carbon material and fluoride salts. The key to the safe disposal and resource utilization of SCCBs is to separate the carbon and fluoride salts deeply. In this study, SCCB was treated by the pyrometallurgical process, and the characteristics of volatilization temperature of fluoride salts were firstly experimentally determined. For a laboratory-scale self-designed high temperature resistance furnace, a three-dimensional model was built and numerical calculation was performed. The heat transfer characteristics, temperature control law and effective volatilization region of fluoride salts were analyzed in detail. The experimental results demonstrate that the effective volatilization temperature of fluoride is higher than 1700 ℃, and the volatilization rate is higher than 93.1%. By simulating the evolution of the temperature field in the furnace under different power supply modes, it is obtained that under the power supply condition of heating at 12 V for 24 h and holding 9 V for 12 h, the maximum temperature in the furnace during the heating phase can reach 2250 ℃, and the theoretical volatilization volume of fluoride salts can reach 98%. After optimization, a step-by-step decreasing mode of power supply can improve the efficiency of treating SCCBs. Moreover, the treating temperature can be maintained for 20 h at 1700 ℃, which is beneficial to the deep separation of carbon material and fluoride salts in SCCB.

     

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