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Blast furnace: a vertical iron-smelting furnace with a circular cross-section. A steel plate is used as the furnace shell, with a refractory brick lining inside it. The blast furnace itself is divided, from top to bottom, into five sections: the throat, the furnace body, the waist, the belly, and the hearth. Due to the favorable technical and economic indicators of blast furnace iron production, as well as its simplicity, high output volume, high labor productivity, and low energy consumption, iron produced by this method accounts for the vast majority of the world’s total iron production. During blast furnace operation, iron ore, coke, and a slag-forming flux (limestone) are fed in from the top of the furnace, while preheated air is blown in through tuyeres located around the perimeter of the furnace at its lower part. At high temperatures, the carbon in coke (and in some blast furnaces, auxiliary fuels such as coal powder, heavy oil, and natural gas are also injected) burns with the oxygen in the blown-in air to produce carbon monoxide and hydrogen; as these gases rise within the furnace, they remove the oxygen from the iron ore, thereby reducing it to obtain iron. The molten iron produced is discharged from the taphole. The unreduced impurities in the iron ore combine with fluxes such as limestone to form slag, which is discharged through the slag outlet. The generated gas is discharged from the top of the furnace; after dust removal, it is used as fuel for hot blast stoves, heating furnaces, coke ovens, boilers, etc. The main product of blast furnace smelting is pig iron, with blast furnace slag and blast furnace gas as by-products. Raw materials for blast furnace smelting The raw materials used in blast furnace smelting mainly consist of iron ore, fuel (coke), and flux (limestone). 　　Typically, to produce 1 ton of pig iron, 1.5–2.0 tons of iron ore, 0.4–0.6 tons of coke, and 0.2–0.4 tons of flux are required, for a total of 2–3 tons of raw materials. To ensure the continuity of blast furnace production, an adequate supply of raw materials is required. 　　Therefore, the task of purchasing raw materials is particularly important for both pig iron manufacturers and steel mills. 　　Blast furnace production is continuous. A generation of blast furnaces (one generation spans from startup to shutdown for major repairs) can operate continuously for several years to over a decade. During production, iron ore, coke, and flux are continuously fed in from the top of the furnace (the furnace top typically consists of a material feed system and hoppers; modern blast furnaces use bell-type or bell-less furnace tops), while hot air at temperatures of 1000–1300 degrees Celsius is blown in through tuyeres located at the bottom of the furnace, along with fuels such as oil, coal, or natural gas. The iron ore fed into blast furnaces is mainly a compound of iron and oxygen. At high temperatures, the carbon in the coke and the injection materials, along with carbon monoxide produced by the combustion of carbon, remove the oxygen from the iron ore to produce iron; this process is called reduction. Iron ore is reduced to pig iron through a reduction reaction, and the molten iron is discharged from the taphole. The gangue in iron ore, the ash in coke and injection materials, combine with fluxes such as limestone added to the furnace to form slag, which is discharged separately through the tap hole and the slag outlet. The gas is extracted from the top of the furnace; after dust removal, it is used as industrial gas. Modernized blast furnaces can also utilize the high pressure at the top of the furnace to generate electricity using some of the extracted gas. 　　Pig iron is a product of blast furnaces (referring to pig iron produced through blast furnace smelting), but the products of blast furnaces are not limited to pig iron; there are also products such as ferromanganese, which belong to the category of ferroalloys. Manganese iron blast furnaces are not included in the calculation of various indicators for iron-making blast furnaces. The blast furnace iron-making process also produces by-products such as water slag, slag wool, and blast furnace gas. 　　Characteristics of blast furnace iron production: It operates on a large scale. Both in other parts of the world and in China, the volume of blast furnaces is continuously increasing. For example, Baosteel’s blast furnace in China has a capacity of 4,063 cubic meters; it produces over 10,000 tons of iron per day, along with more than 4,000 tons of slag, and consumes over 4,000 tons of coke per day. Smelting process Blast furnace smelting is a continuous production process for reducing iron ore into pig iron. Solid raw materials such as iron ore, coke, and fluxes are fed into the blast furnace in batches via the top charging device according to specified mixing ratios, thereby maintaining a certain level of material at the furnace throat. Coke and ore form an alternating layered structure inside the furnace. As it descends, the ore is gradually reduced and melted into iron and slag, accumulating in the furnace bowl and being discharged periodically through the iron tap and slag tap. 　　The cold air supplied by the blower is heated to 800–1350°C in the hot air furnace, and then enters the furnace chamber continuously and steadily through the tuyeres. The hot air causes the coke in front of the tuyeres to burn, producing highly hot reducing gas at temperatures above 2000°C. The rising stream of hot coal gas heats the iron ore and flux, turning them into a liquid state ； This causes the iron ore to undergo a series of physicochemical changes, while the coal gas stream gradually cools down. It is a process of intense heat, mass, and momentum transfer between the descending material column and the ascending coal gas stream. 　　The capillary moisture in the descending charge evaporates when heated to 100–200°C, while the crystalline water in limonite and certain gangues decomposes and evaporates only at 500–800°C. The main fluxes, limestone and dolomite, as well as other carbonates and sulfates, also decompose upon heating in the furnace. The decomposition temperatures of CaCO3 in limestone and MgCO3 in dolomite are 900–1000°C and 740–900°C, respectively. Iron ore begins to be reduced in a blast furnace at 400°C or slightly lower temperatures. Some iron oxide melts in the lower high-temperature zone first to form slag, and then iron is reduced from the slag. 　　Coke does not melt in the blast furnace; it only burns and vaporizes near the tuyeres, with a small portion of the coke vaporizing into CO while reducing oxides. The ore begins to soften when it is partially reduced and heated to 1000–1100°C ； It melts completely at 1350–1400°C ； It drips at temperatures above 1400°C. During the descent, coke and ore maintained an alternating layered structure. Due to the counterflow heat exchange in the blast furnace, several regions with different temperature distributions are formed. Region ① is the dry zone where ore and coke are separated into layers; it is known as the lumpy zone, and there is no liquid in this area ； ②The zone is a softening zone composed of a softening layer and a coke interlayer, where the ore begins to soften and eventually melt completely ； ③The zone is the area where liquid slag and iron droplet; within this zone only coke remains solid ； ④In front of the tuyeres, there is a bag-shaped coke swirling zone where the coke swirls and burns intensely; this area is the main source of heat and gaseous reducing agents within the furnace.

The iron-making process in a blast furnace is essentially a process of reducing iron from its natural form—iron-containing compounds such as ores. The main iron smelting methods include the blast furnace method, direct reduction method, and melt reduction method, etc. The principle behind these methods is that the ore is processed in a specific atmosphere (reducing agents such as CO, H2, C) ； Appropriate temperatures, etc.) are used to obtain reduced pig iron through physicochemical reactions. Apart from a small portion being used for casting, the vast majority of pig iron is used as raw material for steelmaking. 1. The smelting principle of blast furnace ironmaking (the most widely used method). Raw materials for blast furnace smelting: The raw materials used in blast furnace smelting consist mainly of iron ore, fuel (coke), and flux (limestone). Typically, to produce 1 ton of pig iron, 1.5–2.0 tons of iron ore, 0.4–0.6 tons of coke, and 0.2–0.4 tons of flux are required, for a total of 2–3 tons of raw materials. To ensure the continuity of blast furnace production, an adequate supply of raw materials is required. Therefore, the task of purchasing raw materials is particularly important for both pig iron manufacturers and steel mills. Although the principle of smelting pig iron is the same, the process flow varies due to different methods and smelting equipment. The following provides a brief introduction for each one. Blast furnace production is continuous. A generation of blast furnaces (one generation spans from startup to shutdown for major repairs) can operate continuously for several years to over a decade. During production, iron ore, coke, and flux are continuously fed in from the top of the furnace (the furnace top typically consists of a material feed system and hoppers; modern blast furnaces use bell-type or bell-less furnace tops), while hot air at temperatures of 1000–1300 degrees Celsius is blown in through tuyeres located at the bottom of the furnace, along with fuels such as oil, coal, or natural gas. The iron ore fed into blast furnaces is mainly a compound of iron and oxygen. At high temperatures, the carbon in the coke and the injection materials, along with carbon monoxide produced by the combustion of carbon, remove the oxygen from the iron ore to produce iron; this process is called reduction. Iron ore is reduced to pig iron through a reduction reaction, and the molten iron is discharged from the taphole. The gangue in iron ore, the ash in coke and injection materials, combine with fluxes such as limestone added to the furnace to form slag, which is discharged separately through the tap hole and the slag outlet. The gas is extracted from the top of the furnace; after dust removal, it is used as industrial gas. Modernized blast furnaces can also utilize the high pressure at the top of the furnace to generate electricity using some of the extracted gas. Pig iron is a product of blast furnaces (referring to pig iron produced through blast furnace smelting), but the products of blast furnaces are not limited to pig iron; there are also products such as ferromanganese, which belong to the category of ferroalloys. Manganese iron blast furnaces are not included in the calculation of various indicators for iron-making blast furnaces. The blast furnace iron-making process also produces by-products such as water slag, slag wool, and blast furnace gas. Characteristics of blast furnace iron production: It operates on a large scale. Both in other parts of the world and in China, the volume of blast furnaces is continuously increasing. For example, Baosteel’s blast furnace in China has a capacity of 4,063 cubic meters; it produces over 10,000 tons of iron per day, along with more than 4,000 tons of slag, and consumes over 4,000 tons of coke per day. At present, among domestic manufacturers of pure pig iron, the capacity of blast furnaces has reached around 500 cubic meters, but most still remain in the range of 100–300 cubic meters. There are even still small blast furnaces with capacities below 100 cubic meters, which are energy-intensive and polluting; the quality of their products varies greatly, and there is no consistency in such production, making it impossible for them to compete with steel plants worldwide.