Blast Furnace

Blast furnace is a continuous unit of shaft-type. The charging of burden is conducted from above, through the typical charging unit, which is the gas damper of the blast furnace. It is reduced rich iron ore (at present time resources of rich iron ore are preserved only in Australia and Brazil), sinter or pellets in the blast furnace. Sometimes granular pellets are used instead of crude ore. Blast furnace consists of five constructive elements: top cylindrical part is top throat, that is necessary for the charging and distribution of burden in furnace; the highest splayed conic part is shaft, where the heating process of materials and the reducing of iron from oxides pass; the widest cylindrical part is belly, in which the process of softening and melting of the reduced iron passes; tapering conic part is bosh, where a reducing gas – carbon monoxide is generated, the cylindrical part is hearth, that is used to accumulate liquid products of blast furnace method – cast iron and slag. And the top element is tuyere zone, where is the injection of combined blast into the furnace, and the lower element is blast-furnace bottom. There are tuyeres on the top of hearth – holes for supplying of heated to high temperature blast. Blast is compressed air, enriched with oxygen and hydrocarbon fuel. At the level of the tuyeres temperature rises to about 2000 ° C. As the distance upward the temperature drops, and it reaches 270 ° C in the top throat. Thus, different temperatures are set at different heights in the furnace, because of that different chemical processes of transition of ore into metal proceed.

[pic]

Blast furnace in Sestao, Spain.

Coke burns off and generates carbon dioxide and large amount of heat at the top part of hearth, where oxygen supply is big enough.

[pic][pic][pic][pic][pic] Carbon dioxide, leaving enriched oxygen zone, reacts with the coke and generates carbon monoxide is the main blast furnace method