Mechanism of deterioration for dry barrier material in aluminum electrolysis cells

doi:10.11949/j.issn.0438-1157.20180662

Abstract

Abstract:

A component analysis and an X-ray phase analysis of spent dry barrier material were used to reveal the mechanism of deterioration for dry barrier material in aluminum electrolysis cells. The results show that both NaF and cryolite in the osmotic electrolyte react with the dry anti-seepage material to form a glass matrix of nepheline (NaAlSiO₄), which can prevent the electrolyte from further penetrating downward. The Na₃AlF₆ continuously penetrating from the carbon cathode can react with the nephelite to form β-Al₂O₃, and the formation of β-Al₂O₃is one major cause for deterioration of dry barrier materials. It can also produce SiF₄ gas in the process of electrolyte reacts with dry barrier, which makes the silicon migrate to the lower part and results in the decrease of silicon in the upper layer.

Key words: dry barrier, aluminum electrolytic cells, chemical reaction, phase change, alumina

摘要：

通过对大修铝电解槽中废防渗料的成分和物相组成进行分析，探讨了干式防渗料与电解质的反应机理。研究结果表明，渗透电解质中的NaF和冰晶石均会与干式防渗料反应生成霞石(NaAlSiO₄)玻璃体层，可起到防止电解质进一步向下渗透的作用。但随着渗透电解质的增加，冰晶石会继续与霞石反应生成β氧化铝，β氧化铝层不具有防渗作用，这是导致防渗料中电解质继续渗透的主要原因之一。渗透电解质与防渗料反应还可生成SiF₄气体，使硅元素向防渗料下部迁移，导致废防渗料上层硅元素含量降低。

关键词: 干式防渗料, 铝电解槽, 化学反应, 相变, 氧化铝

CLC Number:

TF 803.21

Yaowu WANG, Jianping PENG, Yuezhong DI, Pengcheng HAO. Mechanism of deterioration for dry barrier material in aluminum electrolysis cells[J]. CIESC Journal, 2019, 70(3): 1035-1041.

王耀武, 彭建平, 狄跃忠, 蒿鹏程. 铝电解槽干式防渗料在电解过程中的反应机理探讨[J]. 化工学报, 2019, 70(3): 1035-1041.

Figures/Tables 8

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Element	Dry barrier/%(mass)	Spent dry barrier/%(mass)
Al	18.49	16.6
Si	25.02	12.36
Na	0.10	23.55
F	0	8.00
Ca	1.14	1.98
Fe	2.40	3.59
K	2.05	1.36

Element	Dry barrier/%(mass)	Spent dry barrier/%(mass)
Al	18.49	16.6
Si	25.02	12.36
Na	0.10	23.55
F	0	8.00
Ca	1.14	1.98
Fe	2.40	3.59
K	2.05	1.36

Sample number	Element content/%(mass)
Sample number	Al	Si	Na	F	Ca	TFe	K
dry barrier	18.49	25.02	0.10	0.00	1.14	2.40	2.05
1	22.78	3.66	21.07	18.00	2.37	0.60	0.37
2	21.18	6.82	22.51	19.28	2.46	1.66	0.25
3	13.14	21.52	16.91	1.89	1.40	2.04	1.07
4	12.98	21.06	16.27	0.72	1.16	2.96	1.23
5	15.46	27.15	2.32	0.085	1.20	2.48	1.35

Sample number	Element content/%(mass)
Sample number	Al	Si	Na	F	Ca	TFe	K
dry barrier	18.49	25.02	0.10	0.00	1.14	2.40	2.05
1	22.78	3.66	21.07	18.00	2.37	0.60	0.37
2	21.18	6.82	22.51	19.28	2.46	1.66	0.25
3	13.14	21.52	16.91	1.89	1.40	2.04	1.07
4	12.98	21.06	16.27	0.72	1.16	2.96	1.23
5	15.46	27.15	2.32	0.085	1.20	2.48	1.35

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