What is the process of blast furnace ironmaking?

Blast furnace ironmaking is a complicated process. Its raw materials are iron ore, limestone and coke. The reaction in blast furnace is mainly divided into three parts, the first part is the process of preparing reducing agent, the second part is the main principle of ironmaking, and the third part is the process of removing impurities and slagging. But the iron smelted in blast furnace is impure and contains a small amount of impurities, so it is called pig iron.

In ironmaking, raw materials such as iron ore, coke and limestone are added to the blast furnace (ironmaking blast furnace) in layers according to a certain proportion, and a large amount of oxygen-enriched air heated by the hot blast stove is blown into the blast furnace from the air inlet, so that the coke burns to produce carbon dioxide, and the carbon dioxide reacts with the hot coke on the upper layer and is reduced to carbon monoxide.

Carbon monoxide is added from the top of the blast furnace to react with the falling iron ore. Among them, iron oxide is gradually reduced to liquid iron, commonly known as molten iron. After the reduced molten iron accumulates to a certain extent, it is discharged from the bottom of the furnace.

Limestone added during ironmaking plays a role in slagging, aiming at making gangue (mainly composed of silicon dioxide) with high melting point in iron ore react with limestone to generate calcium silicate floating on molten iron, so as to form slag and separate it from molten iron.

China blast furnace ironmaking

Present situation of blast furnace ironmaking

China's blast furnace ironmaking industry is almost saturated. Although the output ranks first in the world, both the production cost and economic benefit are worse than the world level, which leads to insufficient competitiveness in the world market and hinders the sustainable development of blast furnace ironmaking.

Among them, advanced blast furnace ironworks and backward blast furnace ironworks exist, there are too many small and medium-sized blast furnaces, and there are also blast furnace ironworks that do not meet the requirements. In production, it is impossible to achieve low cost, low consumption and low pollution, ignoring the saturated state of the market, which eventually leads to oversupply and low finished products. Due to this harsh market environment, there are some defects in environmental protection and energy in blast furnace ironmaking in China.

China has also made corresponding countermeasures: in order to solve the problem of excess capacity, various policy schemes were introduced one after another in 20 16, and the structural reform on the supply side was vigorously promoted, which led to a slight rebound in steel prices, but the problem of excess capacity has not been solved, and the economic benefits have improved slightly, but the fundamental problems still exist.

Technical indicators

According to China's industry standard, a blast furnace with a capacity of more than 4000m3 is a large blast furnace, and its productivity is several times that of a small blast furnace, so the large blast furnace in China plays a leading role in blast furnace ironmaking technology.

Among them, the average capacity of large blast furnace is about 4568.75m3, and the average utilization coefficient is about 2.085t/(m3 d). The average coke ratio and coal ratio of large blast furnace are 349.4kg/t and 159.76kg/t respectively, and the average oxygen enrichment rate is 3.36%.

Due to the low grade of ore in China, in order to ensure the stability of large blast furnaces, most imported raw materials are used, among which the proportions of sinter, pellet and lump ore are about 7 1.5%, 19.7% and 8.7%. The fuel ratio of small and medium-sized blast furnaces in China is 539.72kg/t, the coke ratio and coal ratio are 36 1.02kg/t, 14 1.72kg/t respectively, and the blast temperature is 1 153.96℃.

However, the fuel ratio of foreign advanced countries is less than 500 kg/t.

Refer to the above contents: China-How Iron is Made-Blast Furnace Ironmaking.

Baidu encyclopedia-blast furnace ironmaking