Aluminum scrap is the waste aluminum produced in the process of aluminum processing. It is mainly produced from the masonry, planing and milling of aluminum parts, castings, forgings, aluminum bus bars, aluminum guide rods, etc. In this production process, it is usually necessary to add water or lotion for cooling and lubrication, resulting in a large amount of water and oil in the generated aluminum chips, as well as iron debris such as cutter heads. Due to the oil stain, large specific surface area and easy burning loss of aluminum chips, they cannot be melted directly, so they need to be pretreated. The pretreatment of aluminum chips usually adopts a combination of pretreatment technologies such as degreasing, drying, screening, magnetic separation and packaging.
The production process of pretreatment of aluminum chips is summarized as follows:
1. Load the aluminum chips into the receiving bin by crane or loader, and add the aluminum chips into the aluminum chip non oxidation roasting device through vibrating feeder and conveyor belt for oil removal and drying.
2. The degreased and dried aluminum chips enter the vibrating screen to remove inclusions, and then select iron through the hanging iron separator.
3. The aluminum chips after iron separation enter the material box and are pressed into blocks.
The pretreatment process unit of aluminum chips is usually composed of the following parts:
1. The crushing system is usually completed by the waste aluminum crusher to make the aluminum chips smaller.
2. Aluminum chip receiving system, including a receiving bin to the feeder;
3. Pre screening system for sorting inclusions and foreign matters exceeding the specified size;
4. Aluminum chip non oxidation roasting device composed of rotary kiln, combustion chamber and smoke collection device;
5. Sorting and screening system for removing oxides, dirt and metal dust;
6. Magnetic separation system;
The pretreatment of aluminum chips can be roughly divided into four processes: drying, degreasing, iron selection and pressing and packaging. The drying and degreasing of aluminum chips are usually completed in the same equipment. Aluminum chips drying and degreasing are suitable for rotary kiln with direct heating or indirect heating. In the direct heating rotary kiln, the heater is arranged in the rotary kiln, and the convection principle is applied — the raw material and hot gas move relative to each other. The inclination angle of the rotary drum is 3 ° ~ 6 ° and the rotation speed is 2 ~ 6R / min. However, the direct heating rotary kiln is adopted, because the furnace gas is an oxidizing atmosphere, the oxidation and burning loss of aluminum chips is large. Therefore, indirect heating rotary kiln is often used in the drying and degreasing of aluminum chips. The indirect heating chamber and the rotary kiln are arranged separately, and there is a tangent inlet at the top of the indirect heating chamber. The hot gas is distributed along the length of the rotary kiln through the tangent inlet. The oxidation and burning loss of aluminum chips treated by the indirect heating rotary kiln can be reduced to a small extent, and the residual content of oil can be lower than 0.05%.