IMPROVEMENTS IN BLAST FURNACES AND APPARATUS EMPLOYED IN CONNECTION THEREWITH
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Charles Denton Abel at the Office
of the Commissioners of Patents on the 9th February 1880. A communi-
cation from abroad by John Francis Bennett, of Port Carbon, Schuylkill
County, Pennsylvania, United States of America.
CHARLES DENTON ABEL, of No. 28, Southampton Buildings, in the County of
Middlesex. "IMPROVEMENTS IN BLAST FURNACES AND APPARATUS EMPLOYED IN
CONNECTION THEREWITH." [A communication from abroad by John Francis
Bennett, of Port Carbon, Schuylkill County, Pennsylvania, United States of
America.]
One part of the present Invention has reference to an improved construction of
blast furnaces for which Letters Patent were granted to me bearing date 1st July
1878, No. 2627, being a communication from the said J. F. Bennett. According to
the present improvements instead of employing only one tier of tuyeres, as described
in the Specification to the said Patent, two or more tiers of tuyeres are provided,
in which case if three tiers are used the boshes of the furnace are placed higher up
than in the ordinary construction, and by preference they are placed at from
about one third to one fourth the total height of the furnace. The diameters of
the tuyeres are so proportioned that the quantity of air blown through the second
tier of tuyeres is equal in weight to that blown through the lower tuyeres, while if
a third tier be employed, the quantity of air blown through these tuyeres is made
to be double the weight of that blown through the lower tuyeres.
The air blown through the several tiers of tuyeres may be either hot or cold, or
one part of the blast may be hot and another cold; or cold air may be blown
through the lowest tuyeres and hot air through the upper ones, or vice versa, or cold
air may be blown through the two lower tiers, and hot air through the upper tier.
The tuyeres are by preference made of such enlarged diameters that the pressure
of the blast in the supply pipe outside the furnace near the tuyeres need be but
slightly in excess of the pressure within the furnace to maintain the required air
supply. Thus, by way of example, a blast furnace with two tiers of tuy eres,
receiving a blast of 12,000 cubic feet of air per minute, would have five tuyeres of
4 inches diameter each passing cold air in the lower tier, and six tuyeres in the
upper tier of 6 inches diameter passing hot air at about 800° Fahr. into the furnace,
the whole area of the eleven tuyeres being 250 square inches, and each tuyere
delivering an equal weight of air.

page_text: The "bustle" pipes or circular air chambers that supply each tier of tuyeres with
the blast are connected with each other by pipes, which I term "equalisers," and
which have for their object to equalize the weight of air delivered through the
upper and lower tiers of tuyeres, as, should the temperature of the hot air in the
upper chamber, or that of the cold air in the lower chamber vary from any cause,
and consequently the weight of the air decrease or increase, the air will descend
or ascend through the said equalisers from the one chamber to the other, and
thus compensate for the variations in the air blast due to the said variation
in the temperatures. Instead of arranging the tuyeres so that they deliver the
air blast in a horizontal plane at the level thereof, they are inclined upward at
such an angle that the air blasts delivered by them shall meet in the centre of
the furnace at a height not less than the diameter of their nozzles above the
height of the tuyeres at the inner wall of the furnace.
Another part of the Invention has reference to the construction of the
description of tuyeres that are constructed of a coil of pipes through which cold
water is made to circulate. Instead of constructing such tuyeres of a single
length of coiled pipe as heretofore, they are according to this Invention formed
of two lengths of pipe laid side by side and coiled to the required shape, thus
forming the walls of the tuyere of two coils of pipe, each of which has its own cold
water supply. By this arrangement, as the water in circulating through the tuyere
has only to travel through half the length of pipe that it has to pass through in an
ordinary tuyere, it is kept moderately cool instead of becoming heated during its
passage to a considerable degree as is the case with the ordinary tuyere, and thus
the tuyere is preserved from destruction a much greater length of time.
Another part of the Invention relates to the apparatus for heating the air blast
of blast furnaces. The air pipe or pipes leading from the air receiver to the heating
stoves are made of such a diameter that they shall deliver the air freely into the
pipes of the stove, and the diameter of the pipes at the inlet end of the stove is
made equal to or larger than that of the supply pipe, while from the inlet to the
outlet end these pipes are made to increase in diameter in such proportion that at
the outlet their sectional area shall be as much greater than that of the inlet pipes
as the volume of the air is increased by the degree of heat it has acquired.
Furthermore, the pipe or pipes leading from the heating stove to the larger ends
of the belly pipes is or are made of the same sectional area as the total sectional
area of the heating stove pipes at their outlet end. Thus the diminishing of the
area of all the pipes will be effected in the belly pipe, and the pressure of the air
in the air receiver, and at the large end of the belly pipe, will be nearly the same,
thus enabling the blowing engine to deliver more air into the furnace than with
the ordinary construction, where the resistance to the passage of the air gradually
increases as it passes through the heating apparatus owing to its increase in
volume.