DESIGN OF OPEN-HEARTH FURNACES
regenerator under pressure from the producer. The gas pressure
can be and usually is increased toward the end of a campaign when
the regenerators are partially blocked.
The inclination of the ports is fixed when the heads are built.
It frequently happens that these heads are changed several times
before they work in a satisfactory manner. In fact, a number of
furnace drawings which have been published show heads which
must have been altered considerably in order to make the bottom.
In the open-hearth furnace the ports are just below the roof,
60 50 40 30 20 10 10 20 30 40 50 60
Sumaco Capacity, Teas
FIG. 143.—Graphical Comparison of the Port Areas of Various Open-hearth
and the hearth forms a pocket below the level of the port and door
sills and above the level of the tapping hole. This pocket will
become filled with the coolest gases in the heating chamber. In
order to sweep these gases out of the pocket and permit the
sintering of the bottom of the furnace in place it is necessary to
utilize the jet of flame issuing from the ports. This jet must
describe a parabola having a middle ordinate equal to the vertical
distance from the tapping hole to the port sills. In the earliest
types of open-hearth furnace it was endeavored to attain this