Modern blast furnace

FIGURE 21.5 A diagram of a blast furnace for the reduction of iron ore. Modern blast furnaces are as large as 60 m in height and 14 m in diameter. They are designed for continuous operation and produce up to 10,000 tons of iron per day. Note the approximate temperatures and the chemical reactions that occur in the various regions of the furnace. 

The recent fundamental changes in the field of refractory linings in the steel industry, which are not yet at an end, are illustrated in Fig. 5.5-4 in which classic and modern blast furnaces are compared with one another. 

The development of the forerunners of the modern blast furnace is believed to have occurred in Belgium in about 1400. These were still fired by charcoal and produced several hundred kilograms every 24 hr, but also required water power to provide a strong air blast. These larger blast furnaces only gradually displaced the early smaller scale operations. 

TABLE 14.4 Approximate Material Balance Data for a Modern Blast Furnace Producing 600 Tonnes of Pig Iron/Day"... 

The principle and terminology of a modern blast furnace is shown in Figure 8.14. 

Modern blast furnaces (Figure 6.5.10) have a volume of 5000 and produce 10 000 tonnes of Fe per day. A fixed-matrix regenerator system with periodic flow -a so-called Cowper stove, named after Edward A. Cowper (see box) - is used to preheat the blast air up to 1300 °C. The furnace is supplied with a constant flow of hot... 

Tabie 6,5.3 Typical data of a modern blast furnace . ... 

The consumption of fuel (blast furnace coke plus powered coal or oil injected into the tuyeres) per tonne of pig iron of a blast furnace has decreased quite substantially during recent decades and has today reached a value of about 480 kg (Figure 6.5.17). Data for a modern blast furnace with oil injection are given in Table 6.5.3. 

Gurmed insulating castables are used to line the outer middle section of modern blast furnaces also, the uptake sections of the top of the blast furnace are lined with gunned insulating material. 

A typical blast furnace installation is shown in Fig. 8.1 and the evolution of blast furnace sizes in Fig. 8.2 [3]. As seen, recent developments have tended to produce larger furnaces, especially those with larger hearth diameters. Modern blast furnaces have working volumes ranging from 60,000-150,000 ft (1080-4500 m ) and may produce up to 10,000 tons of hot metal per day. 

Pig iron consists of iron combined with numerous other elements. Depending on the composition of the raw materials used in the blast furnace, principally iron ore (beneficiated or otherwise), coke, and limestone, and the manner in which the furnace is operated, pig iron may contain 3.0—4.5% carbon, 0.15—2.5% or more manganese, as much as 0.2% sulfur, and 0.025—2.5% phosphoms siUcon can be as low as 0.15% with modern techniques and is almost always less than 0.8%. Sulfur, phosphoms, and siUcon can be reduced significantly by treating the hot metal between the blast furnace and the steelmaking vessel. During the steelmaking process, many but not all solutes are reduced, often drastically. 

Carbon unites with molten iron, forming a carbide hence the product of the blast-furnace is not pure iron, but a mixture of iron with its carbide, and also with its sulphide and phosphide, if the ore has contained sulphates or phosphates. When such impure iron is brought in contact with oxygen in a molten or semi-molten condition, the carbon, sulphur, and phosphorus are oxidised mostly before the iron. If lime be present, sulphate and phosphate of calcium are formed. The modern process of removing these impurities is to pour the molten metal into a pear-shaped iron vessel lined with bricks made of magnesia while it is molten, air is blown through the metal, and the carbon burns to carbon dioxide the sulphur and phosphorus are likewise oxidised and combine with lime, a layer of which floats on the surface of the molten metal When these impurities have thus been removed in the Bessemer... 

A modern industrial Iron blast furnace is shown here. 

Smelting is a proeess whereby metals, sueh as lead, iron, or eopper, are recovered from a feedstock by the ehemieal reduetion of their eompounds. These reactions occur in various processes and take place at temperatures up to 1400°C in some lead blast furnaces, and to over 1800°C in iron blast furnaces. Various types of furnace are utilized worldwide for the smelting lead. These include the blast, reverberatory and Isasmelt/Ausmelt technologies [6] (see also Chapter 16), and the QSL [7] and Kivcet [8] processes. Not all secondary lead producers use modern technology such... 

The modern view is that the cements best adapted to seawater are blast furnace slag, fly ash and pozzolanic cemenf because a much lower amount of calcium hydroxide is present in the hydration products and the finer pore structure strongly reduces the transport rate of both sulfate and chloride ions. More detailed recommendations may vary on local experience. 

In most blast furnaces hydrocarbons (oil, gas, tar, etc.) are added to the blast to provide a source of hydrogen. In the modern direct-reduction process the CO and H2 maybe produced separately so that the reduction process can proceed at a lower temperature. The pig iron produced by a blast furnace contains about 4% carbon and fur-... 

Iron, the most important metal in modern society, is obtained from its oxide ores by reduction in a blast furnace. The reducing agent is carbon, in Ihe form of coke. Limestone (CaCOs) is added to react with the silicates present in Ihe crude ore to form slag. The raw iron from Ihe blast furnace, called pig iron, is usually taken directly to a converter, where refining takes place to form various kinds of steel. In Ihe converter Ihe molten iron reacts with pure oxygen to oxidize impurity elements. 

The concentrated (dressed) iron ore is formed into sintered pellets at the mine, which are then reduced to iron in a blast furnace by carbon (coke). A modern integrated steel production process based on ore is shown in Figure 8.23. 

Steel is worked up from iron ore, mainly ferric oxides examples of iron ores are magnetite ( Todestone ) Fc304 and hematite FegOa. First, pig iron is made from these raw materials by reduction of the ores in a blast furnace. The pig iron contains a number of impmities, e.g. sulphur, phosphorus and silicon, and it has an unacceptably high carbon content. The contents of these rmdesired components are reduced afterwards by refining and then the raw steel is ready for processing. A modern blast... 

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