Blast furnace feeding

The basicity ratio can be expressed in terms of the blast furnace feeds jtf as follows ... 

Table 22 in Section 4.2.3.2 shows the importance of sintered ore for iron and steel making till today. However, iron ore concentrates from poorer ores became finer while, at the same time, higher quality requirements were imposed on blast furnace feeds. As discussed in Sections 4.2.1.3.2,4.2.1.4.2, and 4.2.3.2, this resulted in the development of balling and pelletizing in North America and Sweden, a technology that has quickly attained widespread acceptance throughout the world (see Section 4.2.3.2, Figure 352, and Table 22). More recently, the technology was adapted for other ores, too. ...

At the Pontgibaud smelter in France, a reverberatory hearth was used for batch calcining, followed by elevation in furnace temperature to cause surface melting and sintering of the calcine into an agglomerated mass, rather than complete melting of the charge. This was withdrawn from the furnace, cooled and broken into lump for blast furnace feed. 

This approach significantly improved the prodnctivity of both the roasting operation and the blast furnace, and lead smelters in the early 1900s had large numbers of converters producing blast furnace feed. 

Alternative processes at the time were the Bradford-Carmichael process, in which lead ore was mixed with dehydrated gypsum (plaster) as a binder, was formed into lumps and then processed in the converter, the Savelsberg Process, which fired ore and limestone over a fuel bed in a converter to produce a sintered material as blast furnace feed. 

A circular rotating furnace using a downward blast through a bed of ore and limestone, covered with a surface layer of wood chips as a starting fuel, was developed by the Cerro de Pasco Corporation in Peru to provide a suitable sintered blast furnace feed. 

As well as containing iron at around 40 to 45 per cent, matte contained about 12 per cent lead, most of the copper from blast furnace feed, about half the zinc and a substantial proportion of the silver. Matte was initially roasted in open heaps or stalls to remove sulfur and was then recycled to the blast furnace, but later reverberatory roasting furnaces were used. A shaft kiln was used at the Harz smelter in Germany. 

Zinc proved to be a particularly troublesome problem and many techniques were developed to remove zinc from blast furnace feed. Mineral separation techniques using gravity had limited effectiveness for some ores, and in particular cases it was necessary to leach zinc from roasted ores... 

Secondary lead smelting is predominantly based on the treatment of scrap lead-acid batteries, as detailed in Chapter 10. A wide range of smelting methods are used for the treatment of secondary lead, originally based on traditional smelting methods such as the hearth and blast furnace, feeding whole batteries, but are changing under stricter environmental controls to the use of prior separation and specialised reduction in rotary furnaces or newer electrochemical techniques. 

Most of the investigations of iron ore reduction described above have been on natural or synthetic iron oxides of low porosity. Studies of the reduction of porous oxides are becoming increasingly popular as porous pellets and sinter continue to supplant relatively nonporous natural lump ores as blast furnace feed material. As long ago as 1936 Joseph reported [18] that the porosity of an iron ore had some influence on the rate at which it could be reduced to iron. El-Mehairy [19] reported a similar effect. McAdam et aL [20] studied the effect of various parameters, including solid structure, on the rate of reduction of pellets made from ironsand concentrate. 

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