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Full text of "The Flow Of Gases In Furnaces"

DESIGN  OF OPEN-HEARTH FURNACES

201

Number of Furances
25       21      12

The diagrams, Figs. 138,139,140 and 141 show, respectively, the
approximate depth of bath in feet; the length of the hearth in
feet; the width of the
hearth in feet and the
area of the hearth in
square feet. Two lines
have been plotted on
these diagrams, show-
ing the dimensions of
the furnaces given in
Table 4, which was
abstracted from Profes-
sor Groume-Grjimailo's
paper, in the Journal de
la Societe Russe de
Metallurgie. This table
was given in The Iron
Age of Dec. 26, 1917.

Fig. 142 shows the
profile of one side of
the hearth suggested
in this paper for a 30-

100 —s

10      20

30      40     50      GO      70      80     90
Capacity of Furnace iu Tons

FIG. 141.—Graphical Comparison of the Hearth
Area of Various Open-hearth Furnaces.

ton     furnace.      These
furnace hearths show a
certain   consistency  in
their   design,   a  larger
hearth and a shallower bath being suggested for the ore process
than for the scrap process.
One feature of the open-hearth and similar furnaces that has
caused sorrow, and tribulation is that the bottom of the furnace
forms a valley below the level of the port sills. One of the basic
principles of furnace design is that the flame must lick the hearth
or bottom of the furnace. The gas pressure in the heating chamber
must be equal to the atmospheric pressure. This last means that
a nice balance must be maintained between the volume of gas and
air entering the chamber and the gases removed from the chamber.
When the pressure in the furnace is permitted to drop below the
atmospheric pressure cold air will tend to flow into the furnace
around the doors and through all cracks and openings. This
chills the bath and causes excessive oxidization to occur.