Metallurgical waste slag refers to various solid wastes generated in the production process of the metallurgical industry. It mainly refers to blast furnace slag produced in iron-making furnaces; steel slag; various non-ferrous metal slags produced by non-ferrous metal smelting, such as copper slag, lead slag, zinc slag, nickel slag, etc.; as well as red mud discharged from the extraction of alumina from bauxite and a small amount of iron oxide slag produced in the steel rolling process. 0.3-0.9t of steel slag is discharged for every ton of pig iron, 0.1-0.3t of steel slag is discharged for every ton of steel, and 0.6-2t of red mud is discharged for every ton of alumina. It is mainly used to manufacture various construction or industrial materials. my country's metallurgical pollution utilization started late, with the utilization rate of blast furnace slag being 70-85%, and the utilization rate of steel slag being only about 25%.

BLAST FURNACE SLAG

The output of blast furnace slag varies with the smelting technology and the grade of the ore. Blast furnace slag belongs to silicate material. It has stable chemical properties and has the characteristics of wear resistance and water absorption, and can be widely used. In order to adapt to different uses, blast furnace slag can be processed into several main products such as water slag, slag crushed stone and expanded slag.

1. Water slag: It is to quench the molten blast furnace slag with water or a mixture of water and air; it becomes a sand-like glassy material. This is also the main method for treating blast furnace slag in my country. There are many specific water quenching methods, and the commonly used ones are the filter tank water quenching process and the stirring tank pumping water quenching process.

2. Slag crushed stone: It is a kind of crushed stone material obtained by crushing, screening and other processes after the blast furnace slag is naturally cooled or water-cooled in the designated slag pit or slag yard to form a denser slag. For this purpose, the hot pouring method is often used. In recent years, Germany, France, Britain, the United States and other countries have mostly adopted the thin layer multi-layer hot pouring method. This method has the advantages of easy operation and high slag density.

3. Expanded slag: It is a porous lightweight slag formed by rapidly cooling the blast furnace slag with water. For this purpose, it can be produced by the injection method, the sprayer trench method, the launder method, etc. The newer process is the production of expanded slag beads using the flow tube method invented by Canadian Slag Co., Ltd., referred to as "expanded beads".

STEEL SLAG

Steel slag is a solid waste discharged during the steelmaking process, including converter slag, electric furnace slag, etc. The slag removal process in the steelmaking process not only affects the development of steelmaking technology, but is also closely related to the comprehensive utilization of steel slag.

1. Cold abandonment method: The steel slag is poured into the slag pot, and after it is slowly cooled, it is directly transported to the slag yard to form a slag mountain.

2. Hot pouring and crushing process: Use a crane to pour the liquid steel slag in the slag pot on the slag bed (or slag pit) in layers, and spray water at the same time to make it quench and break, and then transport it to the slag yard.

3. Steel slag water quenching process: The discharged high-temperature liquid slag is crushed by pressure water cutting, and it shrinks and breaks when it encounters water quenching, and granulates in the water curtain. There are many specific methods such as pan pouring water cooling method, furnace front water flushing method and tipping tank-water pool method.

4. Wind quenching method: Its main advantage is that it can recover 41% of the heat contained in the high-temperature slag (about 2100-2200MJ/t), avoid the problem of slag explosion when it meets water, and improve the operating environment. Steel slag can be wind-quenched into hard spheres less than 3mm, which can be directly used as fine aggregate for mortar.