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摘要: 鋁電解槽炭渣是鋁工業冶煉生產過程中產生的一種危險廢物。炭渣的大量堆存，在浪費電解質資源的同時，也會造成大氣、土壤以及水體的污染。本試驗以炭渣為原料，Na2CO3為添加料，對炭渣的焙燒?水浸工藝回收炭粉和冰晶石的可行性與過程進行了研究。試驗結果表明，將質量比為2.5∶1的Na2CO3與炭渣混合后置于坩堝電阻爐中，在950 ℃下焙燒2 h，炭渣中氧化鋁、冰晶石和亞冰晶石被Na2CO3消耗，焙燒后混合料由C、Na2CO3、NaF、NaAlO2組成。焙燒后混合料在pH為13、浸出溫度為25 ℃的條件下浸出1 h，固液分離后的浸出渣經過水洗、烘干后得到炭粉，其純度可達89%。利用碳酸化法回收浸出液中F?，可獲得主成分合格的粉狀冰晶石。適當地提高焙燒溫度和延長保溫時間可提高炭和電解質的分離效率。研究經濟而有效的炭渣處理方法，不僅可以解決炭渣帶來的環境污染問題，還對社會的可持續發展產生深遠影響。Abstract: Carbon residue in aluminum electrolytic cell is a kind of hazardous waste produced during the smelting and production process of the aluminum industry. Approximately 10 kg of carbon residue is produced for every ton of primary aluminum produced. China’s primary aluminum output was as high as 35.04 million tons in 2019, so its carbon residue production was about 350,000 tons. The accumulation of a large amount of carbon residue wastes electrolyte resources, as well as causes air, soil, and water pollution. Additionally, carbon residue was listed on the National Hazardous Waste List in 2016. Therefore, the treatment of carbon residue needs to be solved urgently. In this experiment, the characteristics of carbon residue were introduced, and it was used as the raw material to study the process feasibility of recovering carbon powder and cryolite by the roasting-water leaching process of carbon residue with Na2CO3 as the additive. Na2CO3 with a mass ratio of 2.5∶1 was mixed with carbon residue, placed in a crucible-resistance furnace, and then baked at 950 ℃ for 2 h. Test results show that the alumina, cryolite, and sub-cryolite in the carbon residue are consumed by Na2CO3, and the mixture after roasting consists of C, Na2CO3, NaF, and NaAlO2. After roasting, the mixture is leached for 1 hour with a pH of 14 and at a leaching temperature of 25 ℃. The purity of the recovered carbon powder after solid-liquid separation can reach 89%. The carbonation method is used to recover F? in the leachate to obtain powdered cryolite with qualified main components. Properly increasing the roasting temperature and extending the holding time can improve the separation efficiency of carbon and electrolyte. Research on economical and effective carbon residue treatment methods can not only solve the environmental pollution caused by carbon residue, but it can also have a profound impact on the sustainable development of society.
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Key words:
- carbon residue /
- aluminum electrolysis /
- electrolyte /
- carbon powder /
- cryolite
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圖 4 炭渣焙燒?水浸試驗原理圖
Figure 4. Principle diagram of carbon residue roasting?water immersion test
圖 5 焙燒試驗主要反應熱力學計算曲線
Figure 5. Main reaction thermodynamic calculation curve of roasting test
圖 7 炭渣（a）和焙燒混合料（b）的SEM-EDS圖
Figure 7. SEM-EDS mapping of carbon residue (a) and roasted mixture (b)
圖 8 不同溫度下Al?H2O 的E?pH圖。（a）25 ℃；（b）50 ℃；（c）75 ℃；（d）100 ℃
Figure 8. E?pH diagram of Al?H2O at different temperatures: (a) 25 ℃; (b) 50 ℃; (c) 75 ℃; (d) 100 ℃
圖 9 950 ℃時保溫時間與混合料質量損失的關系
Figure 9. Relationship between the holding time and mass loss of the mixture at 950 ℃
a—m[Na2CO3]=7.5 g, m[carbon residue]=3 g; b—m[Na2CO3]=7 g, m[carbon residue]=3.5 g; c—m[Na2CO3]=5.25 g, m[carbon residue]=5.25 g
圖 10 焙燒2 h時焙燒溫度與混合料的質量損失的關系
Figure 10. Relationship between the roasting temperature and mass loss of the mixture at 2 h roasting
a—m[Na2CO3]=7.5 g, m[carbon residue]=3 g; b—m[Na2CO3]=7 g, m[carbon residue]=3.5 g; c—m[Na2CO3]=5.25 g; m[carbon residue]=5.25 g
圖 11 浸出時間與炭粉純度的關系
Figure 11. Relationship between leaching time and carbon powder purity
圖 12 試驗Ⅶ（a）和Ⅷ（b）所得炭粉的X射線衍射物相分析
Figure 12. X-ray diffraction phase analysis of carbon powder obtained in Ⅶ(a) and Ⅷ(b)
圖 13 試驗Ⅷ所得冰晶石的X射線衍射物相分析
Figure 13. X-ray diffraction phase analysis of cryolite obtained in Experiment Ⅷ
圖 14 試驗Ⅷ所得炭粉（a, b）和冰晶石（c, d）的SEM圖
Figure 14. SEM images of carbon powder (a, b) and cryolite (c, d) obtained from test Ⅷ
表 1 炭渣主要成分（質量分數）
Table 1. Main components of carbon residue
% Sample
numberC Na Al F O K Li Mg Ca Total Sample 1 30.1 16.53 11.69 33.55 — 0.11 0.002 0.3 1.14 93.422 Sample 2 29.2 16.67 10.92 34.7 — 0.1 0.002 0.33 1.21 93.132 
下載: 導出CSV
表 2 炭渣焙燒試驗參數及炭粉產物純度
Table 2. Roasting test parameters of carbon residue and purity of carbon powder
Test Components Roasting temperature/
℃Holding time/
hThe quality of carbon
powder/gPurity of carbon powder/
%Exp. Ⅰ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 800 1 5.51 55 Exp. Ⅱ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 850 1 5.28 56 Exp. Ⅲ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 900 0.5 3.99 70 Exp. Ⅳ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 900 1 3.69 72 Exp. Ⅴ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 900 1.5 3.71 73 Exp. Ⅵ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 900 2 3.52 76 Exp. Ⅶ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 950 1 3.48 84 Exp. Ⅷ m[carbon residue] = 10 g, m[Na2CO3] = 25 g 950 2 2.95 89
下載: 導出CSV
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