A total of about 1,600 kg/ton-hot metal of such iron-bearing materials as sintered ore, lump ore and pellets, and about 380 kg/ton-hot metal of coke as the reductant are charged in alternate layers from the top of the BF. It has recently become common practice to inject usually 90-120 kg/ton-hot metal of pulverized coal as part of the reductant from the tuyeres in the lower part of the furnace. At present, heavy-oil injection from the tuyeres is rarely used for economic reasons. Approximately 1,000 Nm3/ton-hot metal of hot blast is also blown through the tuyeres after preheating to 1,423-1,523K (1,150-1,250) at the hot stoves. The humidity and oxygen concentration of the hot blast are also controlled. The hot blast reacts with the coke and pulverized coal in the belly and bosh of the BF to form a mixture of carbon monoxide and nitrogen. This mixture ascends in the furnace while exchanging heat and reacting with the raw materials descending from the furnace top. The gas is eventually discharged from the furnace top and recovered for use as fuel in the works. During this process, the layer-thickness ratio of iron-bearing materials to coke charged from the furnace top and their radial distribution are controlled so that the hot blast can pass with appropriate radial distribution. During the descent of the burden in the furnace, the iron-bearing materials are indirectly reduced by carbon monoxide gas in the low-temperature zone of the upper furnace. In the lower part of the furnace, carbon dioxide, produced by the reduction of the remaining iron ore by carbon monoxide is instantaneously reduced by coke (C) into carbon monoxide which again reduces the iron oxide. The overall sequence can be regarded as direct reduction of iron ore by solid carbon in the high-temperature zone of the lower furnace. The reduced iron simultaneously melts, drips, and collects as hot metal at the hearth. The hot metal and molten slag are then discharged at fixed intervals (usually 2-5 hours) by opening the tapholes and cinder notches in the furnace wall. The materials discharged from the BF are hot metal at 1,803K (1,530), about 300 kg/ton-hot metal of molten slag, and dust-bearing exhaust gas discharged from the furnace top. Hot metal is poured into a torpedo car, where it is subjected to hot metal pretreatment, and then transferred to the steelmaking plant. Molten slag is crushed after cooling and is recycled as a material for roadbed and cement. After dust removal, the exhaust gas is used as a fuel for the reheating furnaces. The capacity of a BF is expressed by the weight of hot metal that can be produced per day. Representative technical indicators stand for (i) the tapping ratio, which shows the tapped quantity of hot metal per day per m3 of inner volume of the furnace, and(ii) the fuel ratio, which shows the consumption of coke andauxiliary fuel required per ton of hot metal. In Japanese BFs,tapping ratios of 1.7-2.1 ton/m3/day and fuel ratios of 470-500 kg/ton are typical. The greatest tasks to be achieved in blast-furnace operation are to decrease the unit energy consumption, ensure stable operation in terms of the tapped quantity, composition, and temperature, and to extend the life of the furnace. In recent large-scale BFs, unit energy consumption has been decreased to 13 gigajoules/ton-hot metal, out of which the energy required for ore reduction accounts for about 60%. Careful preparation of raw materials for physical and chemical consistency is an effective way of stabilizing operation over long periods. It is also necessary to understand the physical and chemical behavior accurately in each part of the furnace during operation. For this purpose, monitoring the conditions inside the furnace and applying artificial intelligence for data processing and judgment have been put into practical use with great success. For the future, it will be necessary to understand the complex conditions inside the furnace and use such data to further stabilize furnace operations. Because blast-furnace relining is extremely expensive, total production costs can be reduced substantially by extending furnace life. Technological advances in operation and maintenance to date have extended the life of BFs to as long as 16 years (current record), but further technical development is desired to extend furnace life to twenty years or more.