China is a large metallurgical country, in 2019 China's steel production 0.996 billion tonnage ranked first in the world, accounting for 53.31 of the world's steel production. But in the iron and steel or non-ferrous metal smelting process, will inevitably produce a variety of solid waste, such as steel slag, slag, etc., collectively referred to as metallurgical solid waste, referred to as metallurgical solid waste. At present, the annual production of smelting waste in China's iron and steel industry is about 0.42 billion tons, and that of non-ferrous metal industry is 0.128 billion tons.

Metallurgical solid waste can be divided into slag, ferroalloy slag, steel slag, non-ferrous metal metallurgical slag and dust mud, red mud, etc. according to the production link and composition of solid waste.

1) Slag: In the ironmaking process, iron oxide is reduced to metallic iron at high temperature, and impurities such as silica and alumina in iron ore react with lime to form a melt with silicate and aluminosilicate as the main components. Slag is one of the largest emissions of solid waste in the production of iron and steel metallurgy industry, and its emissions are directly related to the taste of ore and smelting system.

2) steel slag: steel slag is the converter, electric furnace, refining furnace in the smelting process of discharge, by the impurities in the metal raw materials and fluxing agent, furnace lining slag, silicate, ferrite as the main components.

3) dust: with the gas flow or oxidation with the flue gas discharged from the smelting equipment, the general iron or metal element content is higher, can be divided into converter sludge, blast furnace gas ash, iron dust ash, gas dust ash and so on.

4) Red mud: Red mud is the industrial solid waste discharged from the aluminum industry when extracting alumina. Due to the large amount of iron oxide, the appearance is similar to that of red mud. About 1.0-1.8 tons of red mud are discharged for every ton of alumina produced.