The Flow Of Gases In Furnaces

66 APPLICATION OF THE LAWS OF HYDRAULICS
furnaces which operate satisfactorily should conform to it. This
may be determined as follows:
The air enters the heating chamber of the open-hearth furnace
!; preheated to a temperature of 1000° to 1100°, as does the producer
gas. Their combination forms a flaming jet which, according to
the Wanner pyrometer, has a temperature of from 1800° to 1850°
! instead of the theoretical temperature or calorific intensity of a
flame in an athermal chamber of 2100° or more.^
Knowing the quantity of fuel which is transformed into gas in
the producer per second and its composition, it is not difficult to
compute the volume per second of the producer gas and the air
required for its combustion. Consequently it is not difficult to
compute the velocity with which the preheated gas and air enter
the heating chamber.
I For example, a furnace which has a nominal capacity of 30
tonnes, and is operated to make four melts per day, consumes
0 kg 347 of coal per second, and this at 0° corresponds to 1 m3 81 of
gas and 2 m3 52 of air per second. & Assuming 1000° as the tem-
perature of the gas and the air, the volumes entering the heating
chamber each second will be 8 m3 44 of gas and 11 m3 77 of air.
The gas and the air combine in the heating chamber of the furnace
! and give a current of flaming gases at a temperature of 1850°.
!! To what depth will this jet of flame drop within the heating
chamber, if the gas and the air are flowing into the chamber with
; velocities equal to Fair and VgBa, making angles of a and /? with
the horizontal?
The operation of an open-hearth furnace is impossible unless
the bottom is well sintered in place. If the bottom is not well
made, it will be dug up or float up on the molten metal, and in a
furnace in which the bottom cannot be thoroughly sintered the
i ! metal will not be sufficiently heated.
The depth H of the gaseous jet must absolutely be greater than
the distance from the sill of the gas port to the tapping hole.
(1} The method of computing the Calorific Intensity Curves of various com-
bustibles, as developed by the translator from the methods of Mallard
and Le Chatelier, and as used by Damour, are given in an appendix to this
volume.
C2) One kilogram of coal gives approximately 5 m3 22 of producer gas; this
requires about 6 m3 54 of secondary air, this being 1.25 times the theoretical
air supply, plus 0 m3125 of air for the oxidization of certain elements of the
metallic bath.