IMPROVEMENTS IN BLAST FUR- NACES.
Year: 1878

page_text: LETTERS PATENT to Charles Denton Abel, of Southampton Buildings, in the
County of Middlesex, for the Invention of "IMPROVEMENTS IN BLAST FUR-
NACES. A communication from abroad by John F. Bennett, of Pittsburg,
Pennsylvania, in the United States of America.
Sealed the 10th December 1878, and dated 1st July 1878.
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel at
the Office of the Commissioners of Patents on the 1st July 1878.
_CHARLES DENTON ABEL, of Southampton Buildings, in the County of Middlesex.
"IMPROVEMENTS IN BLAST FURNACES." [A communication from abroad by John
F. Bennett, of Pittsburg, Pennsylvania, in the United States of America.]
Blast furnaces, as hereto-before constructed, consist in their main divisions of,
first, the well, which is to contain the inolten metal, and is usually of comparatively
small area in cross section; second, the boshes, which usually are made of the form
of an inverted truncated cone with the sides diverging widely toward the top to
form what is commonly known as the belly of the furnace, which has an area in
cross section largely in excess of the well below, and, usually, also of the throat
above; and, third, the stack or shaft of the furnace, which extends upward from
the boshes any desired distance, according to the inclination of the builder. This
upper shaft usually converges toward the top or throat, so as to give an opening
somewhat smaller in area than the belly of the furnace, but still considerably in
excess of the well or of the point of junction between the well and boshes.
Tuyeres through which the blast is forced into the furnace have been inserted
through the walls of the well, their nozzles terminating nearly even with the inner
face of the wall. As the inner walls or lining wore away these tuyeres were moved
back, so as still to keep their nozzles nearly even with the wearing face. While
furnaces in use differ from each other more or less in detail, yet they, as a rule, have
substantially the parts and proportions given.

page_text: The difficulties which attend this form and construction, and which are effectually
overcome by the present improved construction of furnace are, first, it is necessary
to place the tuyeres pretty low down in order to produce sufficient heat in the lower
part of the well to keep the metal and slags therein in a molten condition, and, the
well being comparatively small in cross section, such lowering of the tuyeres results
in lowering and contracting the zone or belt of fusion, and reduces the efficiency of
the furnace. Again, by placing the tuyeres with their nozzles even or nearly even
with the inner face of the furnace wall the upward currents of the blast are brought
near to the furnace wall or lining, which is thus subjected to intenso heat. Such
heat renders the material of the linings more or less plastic, so that it is easily
worn away by the abrasion or attrition of the descending charge. In time this
wearing away of the furnace wall necessitates the pulling down and rebuilding of
the same.
Another difficulty attending this arrangement of the tuyeres is, that the ascending
gases, being brought thereby close to the side walls, tend to follow such walls in
making their escape from the furnace, as the lumps and irregular pieces lying
against the wall do not pack as densely as in the centre of the furnace, and thereby
offer an casier passage for such gases; but in so doing they do not act equally upon
all parts of the charge, and their full effect is not realised, which results in lossening
the production and increasing expense. To overcome this difficulty the boshes of
the furnace have been widely expanded toward the belly; but such construction of
the boshes interferes seriously with the uniform descent of the charge along the
same, which is a very important consideration. And, again, the belly of the
furnace being made so much longer than the throat, it is very difficult to get an
even and proper distribution of the materials when they reach the belly of the
furnace in their descent.
According to the present improved construction of furnace the inner walls
constitute substantially two frustrums of cones placed base to base, the lower one
resting its smaller end upon the foundation or hearth, and extending upward one-
third the height of the furnace or to the point of greatest area in cross section, the
upper cone beginning with its largest end at such point of greatest area, and
extending upward two-thirds of the height of the furnace.
The inner diameter of the furnace at the base or hearth is, by preference, two-
fifteenths of the whole height of the furnace, and the area in cross section at the
belly or point of greatest diameter is not less than twice nor greater than three
times the area of the base. The area of the throat is, by preference, the same as of
the base, but may be increased by one-half when desired, as when the rolative area
at the point of greatest diameter is increased.
The area of the charging opening in the throat, which is closed by a bell as usual,
is made about one-half the area of the throat.
The tuyeres are inserted through the walls of the furnace at a height above the
base, equal to one-half the diameter of the base; or one-fifteenth the height of the
furnace. This position of the tuyeres is given as affording the best results with a
blast of about five pounds to the square inch, and of a temperature of about 1,000°
Fahr. If the blast be weaker, say one pound, giving a blast of four pounds to the
square inch, then the tuyeres should be lowered a little, depending upon the capacity
of the furnace, so as to keep the molten metal below sufficiently heated. The higher
the tuyeres are placed, and at the same time a sufficient heat be maintained below,
the more productive will be the furnace, for the zone or belt of fusion will thereby
be increased.
The dimensions given to the base of the furnace provide for a much larger plane
chamber or zone in which fusion takes place, and the heat from the same is corre-
spondingly increased. This of itself enables the tuyeres to be placed higher in the
furnace than could be done in the old form, as much increased heat above assists in
keeping the metal below properly heated.
Instead of placing the nozzles of these tuyeres even with the inner face of the
wall, as has heretofore been done, they are, according to the present Invention,

page_text: mado to project into the interior of the furnace, by preference, until their nozzles
reach an imaginary circle which will divide the area at that cross section into two
equal parts; or in any case they project to such distance that the reflex currents
made by the mutual action of the several jets shall not return nor strike back
against the walls of the furnace, or until they shall have been converted into
carbonic oxide gas or carbonic acid gas, in which condition they will not act
destructively on the lining.
By this arrangement the walls are subjected in a much less degree to the
destructive action of the heat and gases of the furnace, and, in consequence of the
diminished activity thus secured about the walls, particles of free or nearly free
carbon settle upon and become attached to the walls. This accumulating carbon
forms in course of time a coat or lining, closely resembling in its nature black lead
or plumbago, and making substantially the lower part of the furnace a black lead
crucible, which practically never wears out, for it continually renews itself by the
action of the furnace as worn away by the attrition of the descending charge or
stock. And it is partly with a view to the formation of this coat or lining that the
furnace is constructed with so great an area in cross section at the base, as room is
thus provided for the same between the face of the wall and nozzles of the tuyeres,
and also provides for free passage of the molten metal and slags through the space
between the nozzles, which is always kept clear by the action of the blast.
An additional advantage is also secured by the enlarged size of this part of the
furnace, as the area of the zone of fusion above the tuyeres is thereby materially
increased, and other things being equal, the productiveness of a furnace of given
capacity depends upon the area of this zone; and, furthermore, the walls of the
furnace being further removed the ascending gases, which are generated near the
centre, do not as readily take to the walls for passage, but rather ascend up through
the body of the charge and permeate the whole inass. This last result is also in a
measure secured by the even distribution of the charge secured, as before described,
by the reduced charging hole.
By making the lower part of the furnace of a continuous conical form not only
is the area of the zone of fusion increased, as already described, but also the angle
formerly made at the top of the well, or at the junction of boshes and well, is
avoided, thus securing a freer action of the furnace.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Denton Abel in the Great Seal Patent Office on the
1st January 1879.
CHARLES DENTON ABEL, of Southampton Buildings, in the County of Middlesex.
"IMPROVEMENTS IN BLAST FURNACES." A communication from abroad by John
F. Bennett, of Pittsburg, Pennsylvania, in the United States of America.
Fig. 1 shews an outside elevation of a furnace constructed according to the present
Invention; Fig. 2 is a vertical section of the same.
Fig. 3 is a transverse section, a little above the tuyeres, and Fig. 4 is also a ver-
tical section of the furnace, having drawn thereon, in full lines, the outline figure of
the interior walls of blast furnaces as frequently constructed.
Figs. 5 and 5 show the interior lines of the furnace, with length of lower part
one-third of the whole height.
Figs. 6 and 6a show the furnace, with length of lower part one-fourth of the
whole height.
Figs. 7 and 7 show the furnace, with length of lower part one-sixth of the
whole height.
Fig. 5 also shows the furnace, with conical or substantially conical base, having
a shaft of conical or substantially conical, or parabolically curved, or any other
shape.
Fig. 8 shows the furnace as a cylinder.
Fig. 9 shows the furnace as substantially two frustrums of cones placed top to
top.
Blast furnaces as hitherto constructed consist in their main divisions of, first, the
well, which is to contain the molten metal, and is usually of comparatively small
area in cross section; second, the boshes, which usually are made of the form of an
inverted truncated cone with the sides diverging widely toward the top, to form
what is commonly known as the belly of the furnace, which has an area in cross
section largely in excess of the well below, and usually also of the throat above;
and, third, the stack or shaft of the furnace, which extends upwards from the boshes
any desired distance, according to the inclination of the builder. This upper shaft
usually converges toward the top or throat, so as to give an opening somewhat
smaller in area than the belly of the furnace, but still considerably in excess of the
well, or of the point of junction between the well and boshes.
Tuyeres through which the blast is forced into the furnace have been inserted
through the walls of the well, their nozzles terminating nearly even with the inner
face of the wall. As the inner walls or lining wore away, these tuyeres were moved
back so as to still keep their nozzles nearly even with the wearing face. While
furnaces in uso differ from each other more or less in detail, yet they as a rule havo
substantially the parts and proportions given.
The difficulties which attend this form and construction (and which are effectually
overcome by the improved furnace) are, first, it is necessary to place the tuyeres
pretty low down in order to produce sufficient heat in the lower part of the well to
keep the metal and slags therein in a molten condition; and the well being com-
paratively small in cross section, such lowering of the tuyeres results in lowering
and contracting the zone or belt of fusion, and reduces the efficiency of the furnace
again by placing the tuyeres with their nozzles even or nearly even with the inner
face of the furnace wall, the upward currents of the blast are brought near to the
furnace wall or lining, which is thus subject to intense heat. Such heat renders the
materials of the linings more or less plastic, so that it is easily worn away by
the abrasion or attrition of the descending charge. In time this wearing away of
the furnace wall necessitates the pulling down and rebuilding of the same. By
dotted lines in Fig. 4 is shewn the form to which a furnace was worn by con-

page_text: tinuous use, the furnace being built originally of the internal form there shown in
outline on the section figure, and marked c. The tuyeres as used in such furnace
are marked e, and as already described they were moved back as the furnace wall
wore away, so as to keep their nozzles about even with the inner face of the
wall.
Another difficulty attending this arrangement of the tuyeres is that the ascending
gases being brought thereby close to the side walls tend to follow such walls in
making their escape from the furnace, as the lumps and irregular pieces lying
against the wall do not pack as densely as in the centre of the furnace, and thereby
offer an easier passage for such gases, but in so doing they do not act equally upon
all parts of the charge, and their full effect is not realised, which results in lessening
the production and increasing the expense. To overcome this difficulty the boshes
of the furnace have been widely expanded towards the belly; but such construction
of the boshes interferes seriously with the uniform descent of the charge along the
saine, which is a very important consideration; and, again, the belly of the furnace
being made so much larger than the throat, it is very difficult to get an even and
proper distribution of the materials when they reach the belly of the furnaco in
their descent.
The following are the essential requisites in the form of a blast furnace :-
First. It is essential to the economical working of a blast furnace that the area at
the zone of fusion shall be as large as possible, in order to produce a large make of
pig iron.
Second. It is essential that the air blown in shall have equable access to the zone of
fusion, to effect which, with a large area of hearth and of zone of fusion, the tuyeres
must be inserted so far into the interior of the furnace that about one-half of its
area at this plane shall be in front of the nozzles and one-half behind them,
Third. It is essential that the furnace shall retain its original shape, and shall not
quickly wear away. To effect this it is necessary to place the tuyeres so far into
the furnace that the blast of atmospheric air shall have become carbonic oxide gas
before it strikes back to the wall, whereby a wall of carbon' will be established
which will protect the lower part of the furnace from ever wearing out.
Fourth. It is essential to the making of the best quality of pig iron that the
pressure of the blast at the zone of fusion shall be light. This is attained by
making the area at the, hearth and at the zone of fusion very large in comparison
with the present practice.
Fifth. It is essential that there shall be an equable descent of the stock materials,
so that slips and scaffoldings shall not occur. This is attained by making the two.
slopes of the furnace very slight, the upper shaft will then deliver the materials to
the greatest diameter with little disturbance of them (slightly more open), and the
lower shaft will deliver them to the zone of fusion with one continued pressure and
descent, without the irregularities of alternate binding and dropping, which when
aggravated become scaffolding and slipping.
I do not restrict myself absolutely to the shape of the furnace being that of two.
frustrums of cones placed base to base at their larger ends.
The furnace may be made a cylinder, as regards its interior form, or substantially
a cylinder as regards its shaft or upper part, with its lower part substantially a
frustrum of a cone, whose smaller end is the bottom; or substantially two frustrums.
of cones, with their smaller ends placed together at the belly (or as in this case may
be more properly called the waist), and their larger ends at the bottom and at the
top, see Figs. 8 and 9, the chief improvement being, as before mentioned, that
the area at the hearth and at the zone of fusion shall be as large as possible, and
that this large area shall be equally supplied with air by the insertion of tuyeres so
far beyond the inner wall that the original form of the furnace shall be preserved,
and that a thin, wall of carbon shall be established that will prevent the wearing
away of the fire-brick wall, and also lessen the dissipation of heat from the chamber
of the zone of fusion.
Sixth. It is essential to deliver the charge at the top so as to obtain its equable

page_text: descent, and thus assist the object mentioned in No. 5. This is effected by a cone
of half the area of the top.
Seventh. It is essential that the heated gases after passing the zone of fusion
shall not be allowed to diverge from a straight line upwards in order that they
shall neither be attenuated nor delivered in less proportionate volume to the stock
nearest the wall. This is attained by making the whole furnace as nearly a cylin-
der as will comport with a free descent of the materials.
Eight. It is essential that as much of the heat as possible shall be delivered to
the descending stock, and that the gases pass off cool. This is attained by making
the furnace of great height in comparison with its average area.
Ninth. It is essential that the tuyeros shall be placed as high above the hearth
as will practically comport with keeping the liquid metal and slag hot enough to
discharge freely; the large space of this part of the furnace assists in this respect.
The high position of the tuyeres (placed so much higher than hitherto usual) will
raise the zone of fusion and increase its area, and will also increase the column of
hot coke, down which the liquid iron from the zone of fusion passes, enabling the
liquid iron to take up more carbon, and thus improve its quality.
The weakest part of a tuyere is its nozzle end. There is no more dangor in
inserting tuyeres far into the body of the furnace (other things being equal) than
even with the wall; but other things are not equal, inasmuch as the end coil of a
tuyere placed even with the wall has to withstand the heat of combustion first
made; and secondly, the reflex of this heat from the wall; also the greater velocity
of the hot current caused by the greater pressure required to penetrate to the
middle of the furnace. It is found that fewer tuyeres are burnt when inserted into
the body of the furnace than when placed even with the wall.
In the improved furnace the inner walls constitute substantially two frustrums
of cones placed base to base, the lower one resting its lower end upon the founda-
tion or hearth, and extending upward from one-sixth to one-third the height of the
furnace, or to the point of greatest area in cross section, the upper cone beginning
with its largest end at such point of greatest area, and extending upward from five-
sixths to two-thirds of the height of the furnace, see Figs. 5, 6, and 7, and 5ª, 6a,
and 7º.
The inner diameter of the furnace at the base or hearth is, by preference, two-
fifteenths of the whole height of the furnace, and the area in cross section at the
belly is not less than twice nor greater than four times the area at the base. The
area of the throat is, by preference, the same as the base, but may be increased by
one-half when desired.
As shewn in the Drawing B, B', represent the walls of the improved furnace,
which are supported at the top of the boshes and at the base by any suitable frame-
work A. These walls are lined with fire-brick in the usual way. The cone or bell
of the furnace is represented at D, and the opening in the throat, through which
the furnace is charged in the usual way, is shewn at C¹. The area of this opening
is equal to one-half the area of the throat.
Furnaces as ordinarily constructed have a cone or bell much smaller in proportion
than this, and the difficulty attending such small openings is that the finer particles
of the charge accumulate in the centre of the furnace, and becoming packed prevent
a free passage of the ascending gas through such packed portion.
A few furnaces have been built with a much larger cone opening than the one
employed according to this Invention, but with such large cones the charge becomes
packed against the walls of the furnace. In no case has a cone of the relative
dimensions given been used in a furnace having the prescribed relative proportions
of throat, belly, and base. By means of an opening and cone of the proportions
given a better and more even distribution of the charge is obtained, especially when
it reaches the boshes, than could be done in the old form of furnaces.
•
Tuyeres a are inserted through the walls of the furnace at a height above the 5
base, equal to one-half the diameter of the base, or one-fifteenth the height of the
furnace. The higher the tuyeres are placed, and at the same time a sufficient heat

page_text: be maintained below, the more productive will be the furnace, for the zone or belt
of fusion will thereby be increased.
The dimensions which have been given to the base of the furnace provide for a
much larger plane chamber or zone in which fusion takes place, and the heat from
the same is correspondingly increased. This of itself enables the tuyeres to be
placed higher in the furnace than could be done in the old form, as such increased
heat above assists in keeping the metal below properly heated.
Instead of placing the nozzles of these tuyeres even with the inner face of the
wall, as has hitherto been done, they are inserted into the interior of the furnace, by
preference, until their nozzles reach an imaginary circle, which will divide the area
at that cross section into two equal parts, or, in any case, they are inserted to such
distance that the reflex currents made by the mutual action of the several jets shall
not return nor strike back against the walls of the furnace, or until they have
become converted into carbonic oxide gas, or carbonic acid gas.
By this arrangement the walls are subjected in a much less degree to the
destructive action of the heat and gases of the furnace, and in consequence of the
diminished activity thus secured about the walls particles of free, or nearly free,
carbon settlo upon and become attached to the walls. This accumulating carbon
forms, in course of time, a wall or lining n closely resembling in its nature blacklead
or plumbago, and making substantially the lower part of the furnace a blacklead
crucible which practically never wears out, for it continually renews itself by the
action of the furnace as it is worn away by the attrition of the descending charge
or stock, and it is partly with a view to the formation of this coat or lining n that
the furnace is constructed with so great area in cross section at the base, as room is
thus provided for the same between the face of the wall and nozzles of the tuyeres,
and also for free passage of the molten metal and slag through the space between
the between the nozzles, which is always kept clear by the action of the blast.
An additional advantage is also secured by the enlarged size of this part of the
furnace, as thereby the area of the zone of fusion abovo the tuyeres is materially
increased, and other things being equal the productiveness of a furnace of given
capacity depends upon the area of this zone; and furthermore, the walls of tho
furnace being further removed the ascending gases, which are generated near the
centre, do not as readily take to the walls for passage, but rather ascend up through
the body of the charge and permeate the whole mass. The last result is also,
in a measure, secured by the even distribution of the charge, effected as before
described.
By following the proportions given a greater height is attained in a furnace of
given capacity than in the old form, and this is a desirable feature, where, as in the
case with the present furnace, the form is such as to give the requisite strength and
also to preserve a uniform distribution of the charge through its whole descent;
still the height may be varied somewhat, to adapt it to a companion furnace already
built, retaining, however, as far as possible, the other features described.
By making the lower part of the furnace of substantially a conical form not only
is the area of the zone of fusion increased, as already described, but also the angle
formerly made at the top of the well is avoided, and in so doing the freer action of
the furnace is secured.
In the old form of blast furnaces, with widely expanded boshes, the ascending
gases having so much room for expansion become cooler towards the walls, and did
not operate upon the charge with the same effect as the hotter portion in the centre,
while in the present furnace the interior being more uniform in size the charge will
be more evenly affected.
In constructing a furnace according to the above-described Invention it is
preferred to make the same,-
First. With the diameter of the top and bottom of the same dimension.
Second. With the inner walls of two straight lines, the lower one to be one-third
and the upper one to be two-thirds of the height, to meet at such an angle that the

page_text: area of the boshes or greatest diameter shall be twice the area of the bottom and
of the top.
•
Third. With the bell or cone one-half the area of the top.
Fourth. With the tuyeres inserted so far into the body of the furnace that one-
half the area of the furnace at this plane shall be in front of and one-half the area
behind the nozzles of the túyeres.
'
Fifth. With the height of the furnace seven and a half times the diameter of the
bottom.
Sixth. With the tuyeres at a height above the bottom of the furnace equal to one-
half the diameter of the bottom.
Having thus described the nature of this Invention, and in what manner tho
same is to be performed, as communicated to me by my foreign correspondent, I
claim,―
First. Constructing a blast smelting furnace composed interiorly of substantially
two frustrums of cones placed base to base, and having, first, its greatest area in
cross section not greater than four times nor less than equal to the area of the base;
second, the area of the thront not less than equal to and not more than twice the
area of the base; and third, the lower frustrum being not less than one-fourth and
not greater than one-half the height of the upper frustrum, substantially as set
forth.
Second. In a blast smelting furnace the use of air blast tuyeres a, two or more in
number, projecting into the interior of the furnace, beneath the charge and above
the space designed to contain the molten metal, substantially as and for the
purposes set forth.
Third. The use of tuyeres a, arranged so that a circle drawn through their nozzles
shall divide the horizontal plane of the furnace at that level into two equal or
nearly equal parts, in combination with a furnace having its greatest area in cross
section, not greater than four times nor less than equal to the area of the base,
substantially as set forth.
Fourth. The use of tuyeres a, arranged as described, in combination with a blast
smelting furnace, having its greatest arca in cross section not greater than four
times nor less than equal to the area of the base, the area of the throat being
not less than equal to and not more than twice greater than that of the base,
and the cone or bell equal to one half the area of the throat, substantially as
described.
Fifth. The combination in a blast smelting furnace of a throat having an area
equal to or not more than twice the area of the base, and a charging hole or bell of
about one-half the area of the throat, substantially as set forth.
In witness whereof, I, the said Charles Denton Abel, have hereunto set
my hand and seal, this First day of January, in the year of our Lord
One thousand eight hundred and seventy-ninc.
CHAS D ARET 101