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Full text of "The Flow Of Gases In Furnaces"


212

APPENDIX VII

the square root of the difference in temperature. This tends to
give an angular direction to currents.

The open-hearth furnace works very close to the yield point
of the refractories, but it is only recently that water-cooling has
been adopted for these furnaces, although it has been used for
years in the blast furnace. Water-cooling adds to the life of the
brickwork by increasing the thermal gradient through the wall
and removing the heat. It adds little if anything to the fuel
consumption and increases the life of certain portions of the
furnace, thereby reducing the amount of time the furnace is down
for local repairs. This means increasing the output. Water-
cooled doors and frames were used a number of years ago, but the
extended use of cooling devices is rather recent.

In early designs of furnaces the regenerator chambers were
under the furnace and the uptakes rose direct to the ports. As a
result the upper portion of the checkerwork blocked up rapidly
and its life was reduced. The first -cinder pockets were small
chambers parallel with the regenerator chamber designed to
distribute the gases to the checkerwork by a number of small
ports and their functioning as cinder pockets was accidental.
The way the cinder lodged in them showed the advantage of
increasing their size, and ample space for this purpose became
available when the checkerwork was removed from below the
furnace and placed under the charging platform. The main fault
with many of these pockets is their lack of depth. Removable
cinder pockets have been devised.

Regenerative methods of firing or the preheating of the incom-
ing gases and the air-for combustion have made it possible to
attain high furnace temperatures. The numerous furnaces
utilizing the heat of the products of combustion for the preheating
of the gas and air supply are a grand memorial to the Siemens
brothers.

In the designing of any furnace with regenerators it is important
to have sufficient regenerator capacity and equally important to
avoid overdoing the matter. The products of combustion leave
the heating chamber of open-hearth furnaces at a temperature of
about 1700. The incoming air enters the valve at 10 &nd the
temperature of the producer gas in the main will range from 500
to 600. Coke oven gas, natural gas or any gaseous fuel con-
taining hydrocarbons cannot be passed through a regenerator

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