What is "blast furnace"

Blast \Blast\ (bl[.a]st), n. [AS. bl[=ae]st a puff of wind, a blowing; akin to Icel. bl[=a]str, OHG. bl[=a]st, and fr. a verb akin to Icel. bl[=a]sa to blow, OHG. bl[^a]san, Goth. bl[=e]san (in comp.); all prob. from the same root as E. blow. See Blow to eject air.]

1. A violent gust of wind.

   And see where surly Winter passes off, Far to the north, and calls his ruffian blasts; His blasts obey, and quit the howling hill.
   --Thomson.

2. A forcible stream of air from an orifice, as from a bellows, the mouth, etc. Hence: The continuous blowing to which one charge of ore or metal is subjected in a furnace; as, to melt so many tons of iron at a blast.

   Note: The terms hot blast and cold blast are employed to designate whether the current is heated or not heated before entering the furnace. A blast furnace is said to be in blast while it is in operation, and out of blast when not in use.

3. The exhaust steam from and engine, driving a column of air out of a boiler chimney, and thus creating an intense draught through the fire; also, any draught produced by the blast.

4. The sound made by blowing a wind instrument; strictly, the sound produces at one breath.

   One blast upon his bugle horn Were worth a thousand men.
   --Sir W. Scott.

   The blast of triumph o'er thy grave.
   --Bryant.

5. A sudden, pernicious effect, as if by a noxious wind, especially on animals and plants; a blight.

   By the blast of God they perish.
   --Job iv. 9.

   Virtue preserved from fell destruction's blast.
   --Shak.

6. The act of rending, or attempting to rend, heavy masses of rock, earth, etc., by the explosion of gunpowder, dynamite, etc.; also, the charge used for this purpose. ``Large blasts are often used.''
   --Tomlinson.

7. A flatulent disease of sheep.

   Blast furnace, a furnace, usually a shaft furnace for smelting ores, into which air is forced by pressure.

   Blast hole, a hole in the bottom of a pump stock through which water enters.

   Blast nozzle, a fixed or variable orifice in the delivery end of a blast pipe; -- called also blast orifice.

   In full blast, in complete operation; in a state of great activity. See Blast, n., 2. [Colloq.]

n. 1 a forge in which ore is smelted to metal, the process being intensified by a blast of hot air. 2 as above, but specifically a forge where the fuel and the ore are intermixed.

n. a furnace for smelting of iron from iron oxide ores; combustion is intensified by a blast of air

A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron, but also others such as lead or copper.

In a blast furnace, fuel, ores, and flux (limestone) are continuously supplied through the top of the furnace, while a hot blast of air (sometimes with oxygen enrichment) is blown into the lower section of the furnace through a series of pipes called tuyeres, so that the chemical reactions take place throughout the furnace as the material moves downward. The end products are usually molten metal and slag phases tapped from the bottom, and flue gases exiting from the top of the furnace. The downward flow of the ore and flux in contact with an upflow of hot, carbon monoxide-rich combustion gases is a countercurrent exchange process.

In contrast, air furnaces (such as reverberatory furnaces) are naturally aspirated, usually by the convection of hot gases in a chimney flue. According to this broad definition, bloomeries for iron, blowing houses for tin, and smelt mills for lead would be classified as blast furnaces. However, the term has usually been limited to those used for smelting iron ore to produce pig iron, an intermediate material used in the production of commercial iron and steel, and the shaft furnaces used in combination with sinter plants in base metals smelting.