The treatment methods for zinc ash can be divided into wet and pyrometallurgical processes. The pyrometallurgical process, also known as distillation, leverages the fact that the boiling point of zinc is much lower than the boiling points of other impurities in the ash. Under normal pressure and high temperature, zinc is volatilized into zinc vapor, or the zinc oxide in the zinc ash is reduced to zinc vapor, which is then condensed into liquid metal zinc or zinc powder. Other metallic impurities remain in the residue. Currently, the commonly used distillation equipment for this method is the horizontal tank. The horizontal tank distillation method for zinc extraction is an ancient technique. In terms of treating zinc ash, it has the advantages of low investment, simple process, and a wide range of tolerance for impurity composition and zinc content. However, it also has significant drawbacks, including high labor intensity, high energy consumption, low processing capacity, and low recovery rate. As humans demand higher quality living environments, this method of treating zinc ash will ultimately be phased out.
Wet zinc smelting is currently the main technological development direction in the zinc smelting industry. Extensive experimental and industrial research has been conducted on using wet processes to treat zinc ash, and significant progress has been made. This treatment process consists of steps such as hot water leaching, neutral leaching, hot acid leaching, and electrodeposition of zinc. Hot water leaching aims to maximize the dissolution of carbon in the zinc ash, reducing the burden of chloride ion removal in subsequent processes. Neutral leaching aims to obtain an electrolyte that meets electrolysis requirements. Hot acid leaching aims to maximize the leaching of zinc into the solution. Experiments have shown that this method can achieve a zinc recovery rate of over 97%, and almost no harmful waste is generated during the process. It is a promising method with good development prospects.
