[ALUMINIUM NETWORK] The redness of the electrolytic cell tank shell is mainly caused by the irrational heat balance. The criterion for judging whether the heat balance is reasonable is the shape of the furnace top, and adjusting the aluminum level and insulation material is the main method for the process manager to adjust the heat balance of the electrolytic cell. .
1: The hazard of red shell
The redness of the tank is a very dangerous signal. According to our measurement of the grate's redness, the plate temperature at the reddish part of the tank shell is higher than 500°C under normal production conditions. There is basically no upper girder or leg extension at the side, and the thickness of the side carbon block is 5 cm. In this article, it was demonstrated that the electrolytic cell not only did not form a furnace grate, but also that the side carbon blocks at the reddening site had been severely corroded, and the electrolytic cell was in danger of lateral breakdown at any time. In order to prevent leakage accidents, operators were forced to take measures such as forced heating at the edge, hair dryer, etc., but the air blow would cause a high cost of compressed air, which would not only increase the labor intensity of workers but also destroy the material balance of the electrolytic cell. . Deal with the problem of redness of the tank shell, must see the essence through the phenomenon, recognize the root causes of the redness of the tank, from the source of governance in order to long-term stability.
2: analysis of the redness of the shell
There are mainly two cases of redness of the tank shell: one is the redness of the tank shell at the pole height of the side of the electrolysis cell. This phenomenon is mainly manifested in the early stage of the enhanced current of the large electrolytic cell or the time from the cold trough to the hot trough, and the incentive is Electrolyte hyperthermia, high flow rate; the other is the red side of the aluminum bath height part of the electrolytic cell, this phenomenon mainly occurs in the ultra-large electrolytic cell or low aluminum water electrolysis cell with a narrow processing surface, the incentive is that the heat balance is unreasonable The electrolyte solidification isotherm was shifted outward and the cell did not stretch.
In the process of changing from cold trough to hot trough, due to poor furnace bottom condition and large horizontal current, often accompanied by voltage pendulum phenomenon, the voltage pendulum not only violently flushes the grate but also reduces the current efficiency, generates additional voltage, and increases thermal income. , destroy the heat balance of the electrolytic cell. The long leg formed by the long-term cold slot melts slowly under the protection of the aluminum liquid, and the heat is hindered from dissipating, exacerbating the heat-dissipation pressure of the upper port furnace, and the polar distance at the side of the electrolytic cell is greatly affected by the intense flushing of the fluid and the thermal tendency. The help was first destroyed. If the cold and hot cells of the electrolytic cell are formed repeatedly, the carbon block on the side will be corroded and worn by the aluminum water and the electrolyte for a long time to cause redness of the cell shell.
3: Countermeasures for redness on the sides
In response to the problem of redness on the side of the electrolytic cell, many aluminum plants in China have taken the following measures:
(1) Increase the level of aluminum, increase the depth of the bath, and increase the capacity of heat dissipation in the side of the electrolytic bath, so that the isotherm of the bath can be reasonably distributed. Increasing the level of aluminum is also beneficial to reduce the degree of electrolyte superheat, weakening the horizontal current inside the aluminum liquid and the bulging of the aluminum liquid, thereby facilitating the formation of the leg extension and the furnace top. From the surface point of view, the level of aluminum is increased to increase heat dissipation. From the perspective of production, the essence of increasing the level of aluminum is to reduce the electrolyte superheat. If you do not master the degree of superheat control, the result will be furnace malformation - stretch legs, empty furnace, but also the problem of redness of the furnace.
(2) Properly increasing the molecular ratio is a preparatory work for increasing the aluminum level. Maintain moderate molecular ratio, enhance electrolyte solubility and dissolution rate of aluminum oxide, make up for the negative factors of high aluminum level and low superheat electrolyte on the bottom of the furnace, help balance heat balance changes and power consumption changes, rarely increase the set voltage Therefore, the pole pitch is compressed to a certain degree, and under the premise of no change in the magnetic field of the electrolytic cell, the compression pole pitch is a major problem affecting the stability of the electrolytic cell. The appropriate molecular ratio also facilitates the internal shift of the electrolyte solidification isotherm, forming a reserve alkaline composition around the furnace, and creating a heat balance environment suitable for increasing the level of production of aluminum to promote the continuous growth of the furnace. Therefore, maintaining a suitable molecular ratio is necessary to adapt to the high-aluminum water process and maintain the polar distance.
(3) The insulation on the pole is a factor that regulates the heat balance more flexible than the maneuverability.
Since the adjustment process of the pole insulation material changes according to the pole change cycle, it is easy to grasp in operation. The pole insulation material is mainly in the form of crust blocks, not in the form of powder. Therefore, in fact, every 1cm increase in insulation material is only about 10mv of heat income. At the same time, due to the reduction of the heat radiation area of ​​the large electrolytic cell, the thermal conductivity of the furnace material has not been correspondingly increased, and the increased heat income has only been resolved by adjusting the technological conditions. Reducing the insulation on the pole is a simple and easy way to adjust the heat balance of the electrolytic cell. Due to the complex factors affecting the thermal balance of the electrolytic cell, the thickness of the thermal insulation material must be determined according to the actual production conditions. The key is to facilitate the formation of the furnace top and leg extension.
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