Present situation and suggestion of comprehensive utilization of metallurgical slag in China

The rapid development of China's economy, black and non-ferrous metallurgy industry is indispensable. National Bureau of Statistics data show that in 2020, China's crude steel production of 1.06 billion tons, 10 kinds of non-ferrous metal production of 618.84 billion tons, accompanied by a large number of metallurgical solid waste. According to the statistics of the Industrial solid Waste network, in 2020, China will produce 3.787 billion tons of industrial solid waste, including 689 million tons of metallurgical slag, accounting for 18.19%, which is the third largest bulk industrial solid waste in addition to tailings and coal gangue. While the accumulation of metallurgical slag occupies a lot of land, it also brings a huge pollution risk to air, soil and water resources, resulting in heavy environmental burden. Under the background of "double carbon", it is urgent to strengthen the comprehensive utilization of metallurgical slag.

1. Classification of metallurgical slag

Metallurgical slag is a variety of solid waste produced in the process of metallurgical industry production, mainly including iron and steel metallurgical slag (blast furnace slag, steel slag, ferroalloy slag, iron and steel dust mud, etc.), non-ferrous smelting slag (copper slag, lead slag, zinc slag, magnesium slag, etc.), electrolytic manganese slag and red mud, this article is collectively referred to as metallurgical slag. Due to the huge amount of red mud produced, only the first three kinds of smelting slag are discussed in this paper.

Blast-furnace slag is a porous and amorphous silicate molten by-product produced in the process of ironmaking in blast furnace. The main components are Ca0, Mg0, Si02 and Al2O3, which is similar to natural ore and has potential chemical activity. Steel slag is a molten solid waste produced in the process of steelmaking, which has complex chemical composition and great fluctuation. Meanwhile, due to the existence of free calcium oxide and free magnesium oxide, its stability is poor, which brings great difficulty to its comprehensive utilization. Iron dust and mud is a solid waste containing iron produced in the whole process of smelting and rolling of iron and steel, and contains unequal amounts of valuable metal zinc.

There are many kinds of nonferrous smelting slag. Taking copper slag as an example, copper slag is a solid waste containing iron, lead and zinc produced in the process of copper smelting, which belongs to typical nonferrous smelting slag and can be divided into blast furnace smelting copper slag and reverberatory furnace smelting copper slag. Besides oxides of Ca, Mg, Si and Al, copper slag contains 20%-40% iron and a certain amount of lead and zinc. It has high comprehensive utilization value.

Electrolytic manganese slag is a black fine mushy powder waste produced in the process of electrolytic manganese sulfate production of metallic manganese. The main components are Si02 and CaSO4·2H20, and the water content is high.

2. Production and comprehensive utilization of metallurgical slag

2.1 Occurrence

In 2020, despite the impact of the new coronavirus epidemic, the production and consumption of the steel industry will remain at a high level, benefiting from relevant economic policies and downstream industries. Rising steel prices combined with the impact of multiple real estate can be released, resumed production, etc., and the national steel has shown a growth trend throughout the year. In 2020, China will produce 887 million tons of pig iron, 1.06 billion tons of crude steel, 34.196 million tons of ferroalloy, 311 million tons of blast furnace slag, 128 million tons of steel slag, 68.392 million tons of ferroalloy slag, 97.614,600 tons of iron-containing dust mud, and a total of 604 million tons of iron and steel metallurgical slag.

In 2020, the global copper market supply shortage of nearly 1.4 million tons, China's apparent consumption of copper has risen, domestic copper prices are first down and then rising, copper producers full of momentum. In 2020, the country's refined copper output will reach 0.025 million tons, of which 7.843,900 tons of mineral copper will be produced, accompanied by about 31.3758 million tons of copper slag. About 73.388 million tons of non-ferrous smelting slag were produced in the year.

At the beginning of 2020, affected by the epidemic, the domestic electrolytic manganese production enterprises have stopped production in a large area, and the output has declined, although the second quarter began to recover, the industry as a whole is still in a state of oversupply, and the price of electrolytic manganese has been going down. At the same time, the national electrolytic metal Manganese Alliance was established, the supply side reform was opened within the industry, and effective production capacity was reduced. In 2020, China's electrolytic manganese production is about 1,389,700 tons, which is lower than that in 2019, with the production of electrolytic manganese slag about 11,117,600 tons.

In summary, the total production of metallurgical slag in China in 2020 is about 689 million t, mainly based on iron and steel metallurgical slag.