Lead-zinc slag and nickel-iron slag are solid waste residues generated during the smelting of lead-zinc ore. These solid smelting slags usually contain iron and lead. These iron-lead symbiotic particles in solid waste residues need to be separated. Zinc slag can be divided into dry slag and wet slag. Currently, the process mainly involves wet slag, where iron-lead symbiotic particles and zinc slag are encapsulated in solid waste residue. To separate iron-lead symbiotic particles, zinc slag must be crushed and ground to break the symbiotic structure between iron-lead particles and the waste residue, allowing individual dissociation of iron-lead particles from the ground zinc slag and waste residue.
The entire separation process includes crushing, grinding, magnetic separation, flotation, etc., each of which is explained below.
The crushing process uses a jaw crusher to crush large materials to within 50mm. The model and quantity of the crusher in the crushing process are determined based on the actual processing capacity. To reduce production costs and process complexity, a single coarse crushing process is generally sufficient.
A simple crushing process can partially dissociate some waste residue and iron-silver symbiotic particles, but there are still materials that are difficult to dissociate, and the material contains lumps with a particle size above 5mm. To improve the dissociation of materials, grinding is usually required. Using grinding equipment will not cause damage to the equipment due to the presence of large particles. Therefore, grinding equipment plays a crucial role in the entire process.
According to the nature of different zinc slag, ball mills or rod mills can be selected for grinding. Using a ball mill for grinding can effectively break the continuous structure between iron-lead alloy particles and waste residue, contributing to a good effect on the next separation.
The advantage of the rod mill lies in its large processing capacity, high grinding efficiency, and the use of peripheral discharge to solve the problem of clearing the grinding equipment. However, the grinding efficiency is lower than that of the ball mill.
Due to the symbiosis of iron and lead in zinc slag, magnetic separation can be used to recover iron-lead symbiotic particles. The ground minerals are sent to a wet magnetic separator, which separates iron-lead symbiotic particles from waste residue, achieving the purpose of recovering iron-lead symbiotic particles. As the waste residue has a high calorific value (usually above 2000 kcal) due to the roasting process during zinc slag smelting, it also has high value and can be sold to brick factories for use in making refractory bricks.
After breaking the continuous structure of iron-lead through the grinding process, lead still adheres to iron due to its nature. Therefore, to separate iron and lead, flotation is necessary. Positive flotation of iron and reverse flotation of iron can achieve the separation of lead and iron. This method basically achieves the complete recovery and utilization of zinc slag. The treatment of zinc slag is a new investment project with small investment, high returns, and it helps reduce resource waste and environmental pollution.
