Rotating degassing method, also known as bubble floating method, is the most advanced and effective purification method. The active gas chlorine, or inert gas argon and nitrogen, or flux mixture gas are introduced into the aluminum melt to form bubbles. The alkali metals and inclusions in the melt undergo chemical reactions through adsorption contact, so as to achieve the purpose of removing alkali metals and inclusions.
The granular refining agent (magnesium chloride) is transported to the furnace metal through a hollow graphite rotor by inert gas (nitrogen or argon). The design of the rotor impeller can cut the small bubbles efficiently. Alkali metals, inclusions and hydrogen are removed directly from the furnace in a short reaction time. Moreover, the temperature and chemical composition of the metal are kept consistent in the furnace by the stirring reaction.
In order to achieve the best purification efficiency, the chemical composition of the refining agent is 60% magnesium chloride and 40% potassium chloride when the rotating speed of graphite rotor is 240 ~ 300 rpm. The amount of refining agent required for the treatment ranges from 0.4 kg / T to 0.6 kg / t al, which is related to the expected chemical composition specification and the set processing time. The gas flow rate – argon or nitrogen – is usually set at 200 L / min.
Compared with the technology using chlorine gas, the investment of rotating degassing method is lower, because there is no need for chlorine station and related chlorine safety system. Moreover, environmental emissions (gas and soot) and slag production will be lower. Different types of degassing equipment are suitable for different furnace configurations.
A large number of small bubbles are formed by the rotating injection of degassing unit, and the contact surface area between bubbles and molten aluminum is large. Under the dual effects of inertial rotation force and buoyancy force, bubbles rise in spiral shape and evenly distribute in the melt in the furnace. The blind area of bubble dispersion and purification is eliminated, and the full integration of bubbles and aluminum melt is increased The large-scale mode drives the flow of aluminum melt, effectively eliminates the stagnation zone of purification in the furnace, and maximizes the purification efficiency.