Slag treatment method for reducing aluminum loss

In the smelting process of aluminum alloy, due to the oxidation of aluminum and the interaction between aluminum and furnace wall and refining agent, the loss of non-recoverable metal is called burning loss. The metal contained in the burnout and slag is collectively referred to as a melt loss. The use of flame reverberatory furnace melting aluminum alloy, due to different charge, the slag amount of 2% to 5% of the charge, and the amount of aluminum in the slag is about 40-60% of the slag amount. Therefore, it is of great significance to properly treat the aluminum slag and recover the aluminum in the slag to reduce the melting loss. The practice of 5t flame reverberatory furnaces for smelting aluminum alloys introduces methods for treating aluminum slags to reduce melt loss.

1 Measures to reduce aluminum slag: During the melting process of aluminum alloy, as the amount of slag increases, the melting loss of aluminum also increases, and the amount of slag is related to factors such as smelting temperature, charge status, and production process. Reduce the amount of slag from the following aspects:

(1) Reasonable furnace geometry and order of addition;

(2) Strictly control the smelting temperature to prevent overheating. The flame spray should have a certain angle in order to melt quickly and shorten the smelting time;

(3) The proper flux and refining time, the stirring should be stable, do not destroy the oxide surface oxide film, timely covering the aluminum melt;

(4) Classifying and cleaning waste aluminum, and comparing the surface area of ​​the finely divided charge with a press;

(5) Treatment of slag before slagging;

2 Treatment of slag

(1) Treatment before slag slag: The slag that floats on the surface of the melt after refining is better in wettability with the melt. The wetting angle is less than 90o. There is a considerable amount of melt in the slag. This part of the melt is granular. Disperses in the slag and adheres to the slag. When the melt temperature is low, the wettability of the two is better. If the slag is at this time, the weight of the melt with the slag is about 60% of the slag weight. The slagging agent with a slag amount of 1 ‰ to 2 均匀 is evenly sprinkled on the surface of the melt to reduce the aluminum content in the slag. The reaction of the slagging agent with the aluminum liquid is as follows: Na2SiF6→2NaF+SiF4; 2NaF+Al2O3→NaAlO2+NaAlOF2; 4NaF+2Al2O3→3NaAlO2+NaAlF4; 6NaF+Al2O3→2AlF3+3Na2O AlF3 reacts exothermically with aluminum and oxygen The heat released releases the viscous slag into a dry, powdery, dry slag. In this way, the wettability of the aluminum melt and the oxides in the slag is reduced, and the particulate aluminum droplets mixed in the slag are removed and returned to the melt.

(2) Aluminum slag treatment after tapping: It should be pointed out that after the above-mentioned treatment, the slag extracted is still mixed with aluminum droplets. When the slag is dipped, it is first dipped into the iron box with perforations so that a part of the aluminum melt adhering to the slag can leak out. After the slag is finished, pour the slag into the prepared pit (after special treatment), sprinkle some slagging agent into the slag, and stir to mix the slag and slagging agent. After 5 to 10 minutes, remove the residue from the pit. Out. Relying on the rapid warming effect of the slagging agent, the slag temperature reached about 950°C, the oxide film around the aluminum droplets in the slag broke, and the aluminum droplets gradually fell to the bottom of the pit with their own gravity. After the secondary treatment of the slag contains only a small amount of aluminum particles, the cooled slag is stored in a certain place, from which to pick the aluminum particles. The above method for treating aluminum slag for recycling is simple and feasible. At present, in the melting process of aluminum alloy, the melting loss is reduced to 1.6%, sometimes reaching 1.4%. If 5000 tons of aluminum alloy is produced each year, the original economic loss caused by melting loss can be reduced by 400,000 yuan, and the economic benefit is considerable.