But carbon will absorb oxygen when in contact under a certain degree of heat, even when combustion cannot take place; and if pulverized charcoal or anthracite and iron ores are mixed in a close vessel, and subjected to a strong heat, the carbon will absorb the oxide of the ores, while the ores will absorb a portion of the carbon of the coal.
We all know that pure iron, which contains no oxygen, will absorb carbon and be come steel when packed in the cementing furnace with charcoal dust, and subjected to a strong heat, though air is carefully excluded from the cementing chest.
These facts demonstrate that the deoxidization and carbonization of the ores in the blast-furnace are the result of contact with coal under a high temperature; but they also produce conclusive evidence that these processes furnish but little of the "waste heat," so called, or the gases escaping from the blast-furnace. The vapors of combustion, arising from the zone of fusion, and produced by the oxygen of the blast and the carbon of the coal, produce all or most of the gas which we call "waste heat," and furnish the means of propelling the blast-engines, and adding caloric to the air thrown into the furnace. These vapors must escape, and though much of the caloric they carry off may be re tained by Truran's suggestions, and employed in the torrefaction of the ores and the increase of temperature in the body of the furnace, the volume of gas would not thereby be diminished. The equivalents of carbon and oxygen might be slightly changed, but
the gases which we utilize now so successfully would still escape, even though the flues were comparatively cold.* The benefit arising from an enlarged area in the body of the furnace is, therefore, due to the longer period given for the preparation of the ore, and perhaps we may add, the coal.
When the coal and ores are fed into the furnace in large masses, as at present prac tised, the period required for full deoxidization and carbonization is much longer than the rapid consumption of the charges will allow, and the ores arrive at the point of fusion only partially prepared for reduction. At this point the deoxidization can take place only at the expense of both oxygen and carbon, or blast and coal.
If allowed to remain longer in contact, the coal would absorb a larger quantity of the oxides of the ore, and the ore would extract a larger quantity of the carbon of the coal.
The extraction of the oxides from and the addition of carbon to the ores prepares them for rapid reduction with but a small amount of caloric; while the absorption of the oxides of the ore by the carbon of the coal prepares the latter for combustion on arriving at the point of fusion, and diminishes the quantity of air required otherwise for that purpose,