Pyrolysis zinc smelting includes roasting, reduction distillation and refining, including zinc smelting in flat tank, vertical tank, closed blast furnace and electrothermal zinc smelting. Zinc smelting in flat tank and vertical tank are indirect heating, which has the reasons of high energy consumption and poor adaptability to raw materials. Zinc smelting in flat tanks is almost eliminated, while zinc smelting in vertical tanks is only adopted by a few 3~5 plants. Although zinc smelting by electrothermal method is directly heated, it does not produce combustion gas, and there are also problems such as small capacity, high energy consumption and low direct yield of zinc. It has little development prospect and is only suitable for use in places where electricity is cheap. Zinc smelting in closed blast furnace is the main pyrometallurgical equipment at present, accounting for about 65,438+00% of the total zinc output, because it can treat lead-zinc mixed concentrate and zinc-containing oxidized materials, and can produce two different metals, lead and zinc, which are directly heated by fuel.
Zinc hydrometallurgy includes traditional zinc hydrometallurgy and total zinc hydrometallurgy. Wet zinc smelting has the advantages of comprehensive utilization of resources, relatively low unit energy consumption and high environmental friendliness, and is the mainstream of zinc metallurgical technology development. By the early 1980s, its output accounted for about 80% of the world's total zinc production.
The traditional zinc hydrometallurgy is actually a combined process of pyrometallurgy and zinc hydrometallurgy, which appeared at the beginning of the 20th century. It includes five main processes: roasting, leaching, purification, electrodeposition and acid production. Generally speaking, most newly-built zinc smelters adopt wet zinc smelting. Its main advantages are to improve working conditions, reduce environmental pollution, facilitate continuous production, automation, large-scale production and comprehensive utilization of raw materials, improve product quality, reduce comprehensive energy consumption and increase economic benefits.
All-wet zinc smelting is based on the direct pressure leaching technology of zinc sulfide concentrate, which was applied to industrial production in the 1990s. The improved process saves the roasting and acid-making processes in the traditional zinc hydrometallurgy process, and the sulfur in zinc concentrate is enriched in the leaching residue in the form of elemental sulfur for further treatment.