The furnace has, in addition to the usual tuyeres near the bottom, a second set near the throat in order to effect a complete oxidation of all combustible matter.
At the tuyeres, with a working height of 17-20 ft., will put through in twenty-four hours, with twelve men, 12% coke and 2 lb blast-pressure, 85 -100 tons average charge, i.e.
At the tuyeres, is about $3.
Holes or " tuyeres " near the bottom or " hearth," and through the melting away, by the heat thus generated, both of the iron itself which has been deoxidized in its descent, and of the other minerals of the ore, called the " gangue," which unite with the FIG.
Interpenetrating this descending column of solid ore, limestone and coke, there is an upward rushing column of hot gases, the atmospheric nitrogen of the blast from the tuyeres, and the FIG.
Above the tuyeres, and is there reversed, as in fig.
In limiting the diameter at the tuyeres to 122 ft., the height of the boshes to one which will keep their upper end below the region of pastiness, and their slope to one over which the burning coke will descend freely, we limit the width of the furnace at the top of the boshes and thus complete the outline of the lower part of the furnace.
- On its way from the blowing engine to the tuyeres of the blast-furnace, the blast, i.e.
16) in which this wonderful process is carried out is a huge retort, lined with clay, dolomite or other refractory material, hung aloft and turned on trunnions, DD, through the right-hand one of which the blast is carried to the gooseneck E, which in turn delivers it to the tuyeres Q at the bottom.
The blast of air forced in through the tuyeres near the bottom of the furnace burns the coke there, and the intense heat thus caused melts away the surrounding iron, so that this column of coke and iron gradually descends; but it is kept at its full height by feeding more coke and iron at its top, until all the iron needed for the day's work has thus been charged.
The first water-jacketed cupola which came into general use was a circular inverted cone, with a slight taper, of 36 inches diameter at the tuyeres, and composed of an outer and an inner metal shell, between which water circulated.
To meet this obstacle P. Manhes proposed elevated side tuyeres, which could be kept clear by punching through gates in a wind box.
Vessels of several designs are used - some modelled exactly after steel converters, other barrelshaped, but all with side tuyeres elevated about io in.
The consuming power of the furnace or the rate at which it can burn the fuel supplied is measured by the number of tuyeres and their section.
Where the operation is simply one of fusion, as in the ironfounder's cupola, in which there is no very great change in volume in the materials on their descent to the tuyeres, the stack is nearly or quite straight-sided; but when, as is the case with the smelting of iron ores with limestone flux, a large proportion of volatile matter has to be removed in the process, a wall of varying inclination is used, so that the body of the furnace is formed of two dissimilar truncated cones, joined by their bases, the lower one passing downwards into a short, nearly cylindrical, position.
The space between the two cylinders serves as a heater and distributor for the blast, which is introduced through the nozzle at the bottom, and enters the furnace through a series of several small tuyeres arranged round the inner lining.