Research on Recovering Waste Printed Circuit Boards by Mechanical Method (Part Two)

It has been reported at home and abroad that an air shaker or an air flow sorter is used to sort the disintegrated components. This type of equipment is simple in structure and low in cost, but it is affected by the size and shape of the equipment and can only sort narrow-grained materials. The sorting effect of materials smaller than 0.5 mm is not good.

The high frequency pneumatic separator is based on the FGX type compound dry coal preparation equipment. In addition to using gravity, vibration force, wind force, buoyancy of the self-generating medium and other factors to make the material loose, the use of the shape of the bed surface and the function of the back plate makes the material to perform spiral movement. In order to sort fine particles of less than 0.5 mm, high Frequency vibration and suitable bed structure to achieve the purpose of sorting by density. Figure 3 shows the appearance of a laboratory high-frequency pneumatic separator, and Figure 4 shows the results of using a high-frequency pneumatic separator to sort the 2.80 to 0.25 mm board crushers.

The use of laboratory high-frequency pneumatic separators to sort materials with a particle size of 2.80 to 0.25 mm, and through one sort of separation, a non-metal (plastic, resin) content of 80% of light products and 73% of heavy metal products can be obtained. People are satisfied. In addition, it has a wide range of sorting particle size, low sorting lower limit, simple auxiliary system, and low investment and operating costs.

3 Sort fine-grained materials according to differences in physical and chemical properties of the surface

Dry sorting equipment is not ideal for sorting <0.25 mm fines, but the highest value copper is in the <0.5 mm fraction. It has been attempted to use hydraulic sedimentation methods to separate using density differences, but the effect is not good. Flotation is a method that uses the difference in the physical and chemical properties of the surface for separation. The use of a reverse flotation process that suppresses copper, flotation resins, and plastics yields satisfactory results. Table 4 shows the results of laboratory tests. After sorting materials from 0.500 to 0.125 mm, the grade of copper concentrates can reach 66%, non-metallic grades from 90% to 95%, and copper recovery rates of 71% and 50%, respectively. . If the multi-segment sorting is performed, the copper grade and recovery rate will further increase.

4 Conclusion

Physical methods include crushing, screening, re-election, magnetic separation and flotation, etc. It is a preliminary technology for the treatment of waste computer motherboards and circuit boards by chemical, pyrometallurgical, and pyrolysis methods, and is a development trend of electronic waste disposal. When broken to 1.2 mm, the waste motherboard can be dissociated. The broken product contains approximately 6% copper, 18% other metals, and 76% non-metal. Copper is mainly distributed in <0.5 mm powder, and other metals are mainly in >0.5 mm. High-frequency pneumatic separator can effectively separate non-metal and metal, and its wide range of sorting particle size, low sorting lower limit and low operating cost are ideal dry sorting equipment. The flotation method can effectively recover copper concentrates from fine-grained non-metals. For fine particles <200 mesh, physical sorting is more difficult and other methods should be considered. Heavy products can be separated by hot metallurgy. However, more than 70% of the non-metallic treatment still needs further study.



Author/Lu Maixi Zhou Cuihong Pan Yongtai Bai Ru China University of Mining and Technology