The nozzle blades of the degassing equipment play an important role in the efficiency of hydrogen removal. It can collide and break the bubbles to make the bubble size smaller, and at the same time use centrifugal force to scatter the bubbles and disperse them evenly, reducing the probability of bubbles merging and improving the effect of hydrogen removal.
The rotating nozzle of the degassing equipment plays an important role in the refinement of the bubbles and the dispersion of the bubbles in the aluminum liquid during the rotation, but it also causes the liquid surface to turn over. With the continuous increase of the nozzle speed, a trumpet-shaped negative pressure zone is formed in the center of the molten aluminum, which intensifies the hydrogen absorption, oxidation and slag inclusion of the molten aluminum. The blades of the nozzle not only have a lateral stirring effect on the molten aluminum, but also make the gas and liquid mixture. The upward jet effect, this jet effect intensifies the churn of molten aluminum. Due to the mechanical action of the blades on the rotating nozzle, the molten aluminum is in a turbulent state, and the centrifugal force causes the molten aluminum to move radially in the nozzle, and the gas is sprayed into the molten aluminum with the flow of the molten aluminum.
When the speed of the nozzle is low, the nozzle has a small stirring effect on the molten aluminum, the turbulence of the molten aluminum is low, and the mechanical splitting effect of the blade on the gas is small, so the bubble size is larger; when the speed is large, the molten aluminum The degree of turbulence is intensified, the blade has a large mechanical splitting effect on the gas, and the centrifugal force on the molten aluminum is large. The bubble diffuses far away with the molten aluminum, the probability of bubbles is small, and the bubble size is small. Therefore, considering the effect of rotation speed on the refinement of bubbles and the interference effect on molten aluminum, the nozzle rotation speed of degassing equipment should be around 250r/mn in actual production.
Gas flow is an important parameter for removing hydrogen from aluminum melt. To achieve a certain hydrogen removal effect in a molten pool with a capacity of about 60t, there must be sufficient gas injection speed. The greater the gas flow, the higher the efficiency of hydrogen removal. However, the air flow cannot be increased without limit. If the gas flow is too large, there will be too many bubbles in the reaction chamber. Relatively speaking, the amount of molten aluminum to be processed becomes gas and the contact time for liquid is shortened. At the same time, when the air flow is too large, the upper and lower convection of the aluminum liquid is intensified, so that the bubble staying in the aluminum melt is greatly shortened, thereby reducing the hydrogen removal effect. For this reason, in actual production, in order to reduce the influence of the upper and lower convection, To improve the gas utilization rate, excessive gas flow should be avoided as much as possible. It is difficult to increase the hydrogen removal efficiency by increasing the gas flow rate alone. The gas flow rate should be controlled so that the aluminum liquid level does not turn over.