Strengthening current is an effective measure to increase production of electrolytic aluminum

The significance of strengthening electric current in aluminum electrolyzer
In recent years, in order to further improve the economic benefits of enterprises, the international aluminum electrolysis industry has generally increased aluminum output by strengthening the series current density of electrolysis. Increasing production efficiency by increasing current efficiency has little effect, while long-term investment in new construction and expansion is long. In contrast, using enhanced current methods to increase output can achieve the goal of less investment and quicker results. It can make full use of existing site, public and auxiliary facilities to increase aluminum production and current efficiency in electrolytic cells and reduce production costs. In particular, the current price of alumina is relatively low, and the profits of electrolytic aluminum companies have been relatively high. Under the stimulation of these factors, electrolytic aluminum enterprises have all raised their output below the full capacity of the equipment.
In 2005, the output of electrolytic aluminum in China reached 7.8 million tons, reaching 9.35 million tons in 2006. There are 43 aluminum plants with a current intensity of 157 kA, and the production volume accounts for about 82% of the national output. The anode current density of these electrolytic cell designs is low, generally less than 0.73 A/cm2, and all have the feasibility of strengthening the current. However, the anodic current density of the pre-baked cells modified by the original 60kA self-baked cell is relatively high, generally 0.80A/cm2~0.88A/cm2, and the feasibility of the enhanced current is small. After deducting the production capacity of the pre-baking cell converted from the baking tank, the new pre-baking cell with a capacity of 160 kA accounts for more than 60% of the total output. If this pre-bake cell current is enhanced by 10%, the output can be increased by 550,000 annually after current fortification. Tons, the investment cost for newly-built electrolytic aluminum in China is 11,000 yuan/ton to 13,000 yuan/ton, while the investment required for the electrolytic aluminum to increase current output is only 0 to 30% of the investment in new projects, which can save about 80% of investment. , Strengthen current and increase output of 550,000 tons of electrolytic aluminum can save 5 billion yuan in investment. In addition, the increase in the output of the electrolytic aluminum plant enables the fixed cost per ton of aluminum to be reduced by approximately 10%, ie, a cost savings of approximately 55 yuan per ton, and a national savings of 332.10 million yuan. It can be seen that the aluminum electro-refining current is of great significance. Therefore, it is said that the intensified current is an effective measure to save production of electrolytic aluminum.
The feasibility of strengthening the current
1. Domestic successful case of strengthening current. The domestic aluminum electrolyzer enhanced current in 2002, but the magnitude of the intensified current is relatively small, generally 1% to 5%. In recent years, the magnitude of the intensified current has increased. Chinalco Guangxi Branch and Qinghai Branch successfully used the extended eccentric anode to successfully intensify the current in 160kA pre-baked cells to 180kA and increase the series current by 12.5%. The Guangxi Branch's 2006 test cell further intensified the current to 190kA; Lanzhou Aluminum In 2006, without increasing the anode size, the current in the 200 kA series of prebaked cells was enhanced to 220 kA, the test cell was enhanced to 230 kA, and the intensity of the intensified current reached 10% to 15%; the Zhengzhou Research Institute was in the original 280 kA. The prebaked anode cell is based on a strengthening current up to 300 kA. The above successful cases of intensified current have achieved good economic and social benefits. Both have passed the appraisal of domestic authoritative professional technologies, and industrial production practices have shown that they can be applied.
2. Strengthen current and anode current density and current efficiency. At the 6th Electrolytic Aluminium Technology Conference held in Australia in November 1999, a new series of 200 kA pre-baked cells at the Dubal aluminum plant in New Zealand, the anode current density is as high as 0.88 A/cm2, and the current efficiency of one year's operation is achieved. 95.5%, the result proves that the electrolyzer operates stably.
Aldrich Aluminum Plant, Norway, 1 series 150kA enhanced to 159kA, current efficiency increased from 88.9% to 93.2%, 11 series 160kA enhanced to 169kA, current efficiency increased from 90.5% to 93.4%; French Pischne company 180kA enhanced to 210kA The current efficiency increased from 94.8% to 94.9% to 95.3%. The design value of the anode current density of domestic 160 ~ kA200kA pre-baked cells is about 0.72A/cm2, the current efficiency is about 92% ~ 93%, the anode current density is 0.75A/cm2 ~ 0.83A/cm2 after the strengthening current, the current efficiency is improved. About 0.2 percentage points, the overall view of domestic currents after the strengthening of current efficiency change is not.
3. Strengthen the feasibility of current. The anode current density of the original 60 kA self-baked cell was as high as 1.0 A/cm2 at the earliest, and the anode current density was still above 0.82 A/cm2 after multiple anode widening. The pre-baked anode current density in foreign countries is generally 0.8A/cm2 to 0.9A/cm2. As the anode production technology is mature, the anode quality is continuously improved, and the current density is allowed to increase in terms of the physical and chemical properties of the anode carbon material. To a certain level, the anode current density can be increased to 0.9 A/cm2 to achieve normal aluminum electrolytic production.
From the above several examples, we can see that the experience of strengthening the current is successful, and the current efficiency after the strengthening current has been improved to different degrees, indicating that the current density increases with the anode and the corresponding technical measures are taken after the strengthening of the current. The current efficiency will be improved. The higher the research density, the higher the current efficiency. However, the current efficiency tends to be constant when the anode current density reaches a certain value (1.57 A/cm 2 ). As far as China's large-scale pre-baked cells are concerned, it is possible to increase the current density by 10% to 20% for any anode current density below 0.73A/cm2.
Intensified current solutions and major technical measures
1. Enhanced current solution. Aluminum electrolysis cell intensified current, involving aluminum lining lining materials, electric heat balance, magnetic field effects, etc.
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