Aluminum ash processing technology development trend

Aluminum recovery has always been the most important indicator for aluminum ash processing plants. The actual operation of the furnace and the remelting furnace and the cooling technology have a major influence on the recovery of aluminum ash.

Tilt-type rotary furnace and dry flux melting technology

1. Tilting rotary furnace. As we all know, the key equipment in most aluminum ash processing plants is the rotary kiln. The use of rotary kiln to recover the aluminum ash in aluminum ash has been more than 50 years old. However, traditional rotary furnaces are fixed-pave type, with a cylindrical steel structure container with a refractory lining and horizontally mounted on a trunnion. The operation of the rotary kiln includes melting the flux in the furnace and adding aluminum ash to the furnace. The rotation of the furnace forces the aluminum ash to be below the surface of the flux and is not directly impacted by the burner flame. The furnace operates on a periodic basis for several hours. Each cycle consists of charging the flux and melting the flux, charging the aluminum ash to melt the aluminum ash, releasing the aluminum water and removing the used flux or salt cake. With the increasingly stringent global environmental legislation on waste gas and solid waste and the need to maximize the recycling rate of aluminum, rotary kiln technology is continuously improving. The use of an advanced rotary kiln technology with an oxygen-fuel combustion system, advanced computer control technology and a SCADA system will provide a reliable guarantee for maximizing aluminum recovery in aluminum ash.

2. Dry flux melting technology. The use of dry flux melting technology can increase the recovery of aluminum by a few percentage points, significantly reducing the amount of flux required and salt cake produced, thereby reducing production costs, with a flux to non-metal ratio of 0.3:1. The traditional fixed-shaft rotary kiln is operated in a liquid state. Therefore, a sufficient amount of flux is added to the furnace to maintain its liquid state. The flux and non-metal ratio is 1:10.

For a company producing 500 tons of aluminum ash per month, if it is skilled in inclined rotary furnace technology, it will increase the aluminum recovery rate in aluminum ash by 3% to 8%, and increase the income of 460,000 US dollars in one year. Advanced aluminum ash processing technology, the use of oxygen-fuel combustion system tilting rotary kiln technology and dry flux melting technology, can achieve the maximum aluminum recovery in aluminum ash.

The best flux formula and the preservation of aluminum ash

1. The best flux formula. In the processing of aluminum ash, the flux addition ratio, flux formulation and chemical composition have a great impact on aluminum recovery in aluminum ash. Flux should have the following properties: rapid melting at the lowest melting temperature; protection of aluminum will not oxidize; dissolve and absorb aluminum oxide, dirt and other impurities, while reducing the surface tension of liquid aluminum particles; promote the condensation of liquid aluminum droplets And form a larger molten pool.

The salt flux for processing aluminum ash is a mixture of NaCl and KCl. The composition of the salt flux with the lowest eutectic melting point is 58% KCl and 42% NaCl because KCl is more expensive than NaCl, so 30% KCl and 70% NaCl are used. The ratio is an effective formula. However, the best recovery flux formulations are 47.5% KCl, 47.5% NaCl, and 5% cryolite. The amount of salt flux used is taken as the percentage of aluminum in the processed aluminum ash. The greater the amount of non-metallic substances in the aluminum ash, such as the greater amount of oxides and impurities, the greater the amount of salt flux required. Flux particle size is also an important factor influencing aluminum recovery.

2. Aluminum ash preservation. Aluminum ash as a second-use material, should pay attention to prevent impurities and other waste mixed into the ground, keep the aluminum ash dry, in order to obtain the best aluminum ash quality and recovery rate. If aluminum ash is stored outdoors or exposed to moisture, the recovery rate of aluminum will be greatly affected.