Main process of recycled zinc recovery

The treatment process of regenerated zinc in China is divided into two methods: fire separation method and wet method. Wherein the high zinc content of the waste processing method of metal materials having a reducing heteroaryl distillation, wet, liquation melting aluminum method. The treatment of zinc dust with low zinc content, such as rotary kiln, flat kiln and other processes, first produces zinc oxide, and zinc ingots can be obtained directly.

1. Treatment of waste materials with high zinc content

The distillation method and the wet method are currently used for the recovery process of zinc slag, zinc ash, etc., which have a high zinc content, and zinc ingots can be obtained directly.

(1) Treatment of zinc-rich waste by horizontal tank distillation

This method is relatively simple in production process, does not require a lot of electromechanical equipment, has less capital investment and lower cost. It is still used by some small-scale regenerative zinc smelters in China to process zinc-rich waste, such as hot-dip galvanized ash, zinc slag and coarse Zinc ingots, scraps, etc.

When the raw material for zinc smelting in the horizontal tank is zinc slag, the zinc recovery rate is 80%-85%, and if it is zinc ash, it is only 40%-60%. The zinc obtained from the horizontal tank zinc smelting is not high, generally only reach No. 4 or No. 5 zinc, even the outer zinc. In order to obtain high quality regenerated zinc, it needs to be rectified and refined.

(2) Vacuum distillation

The principle of this method is to use zinc vapor and other metals in the zinc slag to achieve the purpose of separating zinc and impurities. The method can only deal with hot-dip galvanizing slag, which has the advantages of higher evaporation rate and higher metal recovery rate at lower temperature, selective recovery of components in the material, and avoidance of oxidation and product. Other pollution, the purity can reach 99.8% ~ 99.9%, the recovery rate can reach more than 85%. The unvaporized zinc in the slag can be returned to the distillation after simple sorting, so the total recovery rate can reach over 98%, and the equipment is simple, the operation is simple, and the processing cost is lower than the conventional flat tank regeneration process. However, the equipment investment of this law is large, and the promotion is limited. It is used in some large galvanized steel plants.

(3) Wet process

The wet process can be divided into two processes: soluble anode electrolysis and leaching-purification-electrodeposition. The soluble anodic electrolysis process is suitable for treating zinc slag, while the leaching-purification-electrodeposition process is suitable for treating zinc ash. Both processes use an aqueous solution of sulfuric acid and zinc sulfate as the electrolyte.

In the zinc smelting industry, wet zinc smelting is the main technical development direction. The advantage of the wet process is that the zinc recovery rate is high, about 20% higher than the traditional fire method, which is convenient for mechanization, automation, process wastewater, Less waste residue and less environmental pollution.

Second, the treatment of zinc dust in steel plants