An Improved Cupola Furnace.
Year: 1894

page_text: Date of Application, 28th May, 1894
Complete Specification Left, 28th Feb., 1895-Accepted, 30th Mar., 1895
An Improved Cupola Furnace.
I, WILLIAM HENRY BRADLEY, of Mingo Junction, Ohio, U.S.A., Inventor,
do hereby declare the nature of this invention to be as follows:-
The object of this invention is to provide a cupola furnace whereby great saving
of fuel is effected as will be understood by the following description.
My improved cupola comprises a circular lower part from which the tuyeres lead
into the furnace. The upper part of the furnace is of larger diameter and forms the
stack portion, the two being joined by a cone-shaped part. The charging chutes
lead through the conical part and provide means for charging fuel into the furnace.
These chutes are each fitted with a door, and extend in a circular series around the
furnace, and are preferably beneath the fuel-charging floor, which is supported
upon I-beams. A circular band extends upwardly from the lower and larger part
of the cupola to the charging floor and encloses the charging openings.
In the upper part of the stack is the metal-charging opening which has a hinged
door resting against stops when in its lowermost position; the closing of the metal
charging openings giving a natural draught at the fuel openings, thereby consuming
the combustible gases.
In case the cupola cannot be easily fitted up with a fuel-charging floor I employ
chutes extending downwardly from the metal charging floor to the fuel-charging
openings and which chutes have hinged doors therein capable of being operated by
counterweighted levers and chains from the floor above.
I employ a series of tuyeres at or near the fuel openings to furnish air for the
burning and combustible gases.
It will be understood that by reason of the upper part of the cupola being of
smaller diameter than the lower part, the metal entered from above will be deposited
in the centre, with the fuel (which is entered into the lower and larger part)
surrounding it and in contact with the blast; this arrangement of fuel and metal
effecting a great saving of fuel.
Dated this 021 d of M. 1904
W. H. MUNNS,
Agent for Inventor.
1, WILLIAM HENRY BRADLEY, of Mingo Junction, Ohio, U.S.A., Inventor,
do hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement :-
Fig. 1 is a side elevation partly in section, of my improved cupola furnace.
and
Fig. 2., is a cross sectional view on the lines A-A, B-B, and C-C of Fig. 1;

page_text: . In the present working of cupola furnaces the fuel and metal are charged
in together at a certain distance above the tuyeres, and if this distance is small
the combustible gasses rising through the charge are not wholly consumed and
pass off above the charge at a high temperature, thus wasting the heat; while
if the distance is large, the fuel is consumed before it descends to the level of
the tuyeres, and the metal oxidises rapidly under the action of the blast, causing
a loss of metal.
Moreover, in the second case, the slag formed above the tuyeres chills as it
meets the cold blast and clogs the cupola, and the CO₂ rising through the high
charge is changed to the combustible gas CO, which passes off and is lost. In
the present practice, a mean of these extremes is used, partaking of the faults
of each, but in a lesser degree, and in the best results less than one half of the
heat of the fuel is utilized for the melting of the metal.
Various expedients have been tried to overcome these difficulties, such as
blowing in air above the point of incandescent fuel but this again. raises the
heat at such point and consumes the fuel before it descends to the level of the
tuyeres and the metal oxidises rapidly under the action of the blast causing a
loss of metal, or with a short charge causes the gasses to pass off at a high
temperature.
My invention is designed to do away with all these difficulties and evil effects
of waste of fuel, oxidation of metal, and chilling of the slag, thus creating a
great saving in the cost of fuel and increasing the melting capacity of the
furnace, and it consists in charging in the fuel on a different level from that of
the metal. The level for charging the fuel (depending upon the melting capacity
of the cupola,) should be at such a distance above the tuyeres that the fuel
may become heated to the igniting point before reaching the zone of fusion, but
not so high that the fuel will be consumed before descending to the tuyeres.
The metal charging level should be at such a height above the fuel charging
level, that the gasses of combustion may before passing off, have sufficient time
to be fully consumed and cooled down to the most economical point of tempera-
ture while ascending through the charge of metal thus utilizing the full effective
heat of the fuel by preheating the metal.
In the drawings, the lower portion 2 of the cupola is provided with the usual
tuyere belt 3, from which the tuyeres 4 lead into the furnace. The upper
portion 5 of the cupola is smaller in cross section, forming a stack portion
concentric with the lower portion, the two being joined by the cone shaped
portion 6. Through this conical portion lead the charging chutes 7 for the
fuel, and each chute may have a hinged door 8 for closing the same; these
cbutes extending in a circular series about the cupola and being preferably
immediately beneath the fuel charging floor 9 supported on the I-beams 10.
A circular band 11 extends upwardly from the lower part 2 of the cupola to
the charging floor 9, and incloses the charging openings. In the upper part of
the stack is the metal charging opening 12 which is provided with a hinged
door 13, the door resting against stops 14, when in its lowermost position, the
closing of the metal charging openings giving a natural draught at the fuel
openings, by which the combustible gasses will be consumed.
In case the cupola cannot be easily fitted up with a fuel charging floor I may
employ chutes 15 or other suitable devices leading downwardly from the metal
charging floor to the fuel charging openings or level, which may have the hinged
doors 16 therein, provided with counterweighted arms 17, which may be operated
by a chain, 18 from above. I employ also a series of tuyeres 19 at or near the fuel
openings, and a second series 20 above the fuel-openings, to furnish air for burning
the combustible gasses. The air admitted at and above the fuel charging openings
may be regulated by any suitable device, so that the air will enter in sufficient
quantity to consume the gasses, but not in such excess as to cool the burning
gasses.
The operation of my device is obvious. The metal being charged in a central

page_text: stack on an upper level, and the fuel in openings in the side of the stack at a lower
level, or into openings at the cone sheet of a larger concentric stack, the metal will
descend in the centre with the fuel around the outside, the fuel thus being between
the metal and the air inlets, a condition which is correct in theory and in practice
and has been much sought after. The blast of air from the tuyeres thus meets the
incandescent fuel at and above the tuyeres before it enters the zone of metal; being
thereby, heated to the temperature of the zone of fusion it unites with the carbon
of the fuel and maintains a reducing and not an oxidising atmosphere, hence no
oxidation of metal takes place, and the slag and metal are not chilled. The flames
and hot gasses pass into the central zone of metal and ascend through the interstices,
up to the fuel charging level where air is admitted to burn the carbo oxide, the
flames and heat thus produced ascend through the interstices of the metal preheating
the same without burning the fuel. The fuel is charged at such a point above
the tuyeres that it just attains the igniting point as the zone of fusion is reached
since if too high the fuel is consumed before reaching the tuyeres, and the entering
air chills the slag and oxidises the metal, while if too low the fuel reaches t'he
tuyeres in too cool a condition and reduces the zone of fusion thus lowering the
melting capacity of the cupola and wasting the fuel, which falls below the zone of
fusion before being consumed, and gives up its carbon to the metal, thus requiring
a longer blowing in the converter and delaying each heat. This distance between
the charging point of fuel and the tuyeres depends upon the rapidity of melting
of the cupola since the more rapid the descent of the charge the greater must this
distance become. To regulate this distance I employ several rows of tuyeres one
above the other, and if running slowly the upper tuyeres are used the others being
stopped off, the lower tuyeres being employed when running faster. The fuel
having only a short distance to descend is not consumed before reaching the tuyeres,
and hence the highest point of temperature in the zone melting fusion is at and
immediately above of the tuyeres at all times, while the slag formed at this point
in descending, falls below the zone of blast, and is not chilled thereby. Moreover,
the metal, as it melts, immediately falls below the line of tuyeres and is therefore
not oxidized by the blast, and the hot gasses and burning carbonic oxide pass up
through the metal and give up their entire heat thereto.
I am aware that it has heretofore been proposed to heat the metal above the
point of introduction of the fuel merely by the surplus heat of the ascending
gasses, but I believe I am the first to so proportion the distance between the
fuel charging openings and the tuyeres, that the fuel is preheated just to the
temperature of ignition when it reaches the zone of fusion and to introduce air
at or above the fuel openings so as to combine with the rising carbonic oxide
and burn in contact with the metal alone, above the level of the fuel especially
when this air is so regulated as to give the proper amount for uniting with the
carbonic oxide.
The advantages of my construction arise from the great saving in the expense
of running the furnace due to the reduction in the amount of fuel employed,
and from the total lack of any clogging or uneven action of the charge, while
the invention is easily applied to existing conditions.
Many changes may be made in the form and arrangement of the parts without
departure from my invention, which I regard as lying broadly in the furnace
having fuel and metal charging openings at different levels and admitting air
for burning the gasses above the fuel charging level. I do not intend to limit
the invention to the melting of metal only as it may be applied to the reduction
of other materials as well.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:-
1. A furnace having above it crucible one or more fuel charging openings, one
or more metal charging openings above the fuel charging onenings and means for

page_text: supplying air to unite with the carbonic oxide rising from the fuel and preheat the
metal before it reaches the fuel; substantially as described.
2. A furnace, having one or more inetal charging openings, an outer circum-
ferential series of fuel charging openings at a lower level, means for supplying air
to unite with the carbonic oxide rising from the fuel and burn in contact with the
metal substantially as and for the purposes described.
3. A furnace, having a series tuyeres or air blast inlets, circumferential fuel
charging openings above the same, and one or more metal charging openings above
the fuel charging openings; substantially as and for the purposes described.
4. A furnace, having above its crucible one or more fuel charging openings, one
or more metal charging openings above the fuel charging openings, and one or more
air inlets at or adjacent to the fuel charging openings; substantially as and for the
purposes described.
5. A furnace having above its crucible one or more fuel charging openings,
an air inlet or a series of air inlets at or adjacent to the fuel charging openings,
and an air inlet or inlets above the same; substantially as described.
6. A furnace having above the ordinary tuyere-belt, an opening or series of fuel
charging openings in its circumference, covers or doors for said openings, and one
or more metal charging openings above the fuel charging openings; substantially
as and for the purposes described.
7. A furnace having above the ordinary tuyere belt, opening or series of fuel
charging openings in its circumference, one or more metal charging openings above
the fuel charging openings, and covers or doors for said openings; substantially as
and for the purpose described.
8. A cupola or furnace, having two or more series of blast inlets above its crucible,
and one or more fuel charging openings between two or more of the said series;
substantially as and for the purposes described.
9. The method of operating furnaces, consisting in charging substantially the
entire body of fuel at a suitable level, charging the metal at a higher level,
admitting air above the zone of fusion to unite with the carbonic oxide rising from
the fuel and burning the same in contact with the unmelted metal; substantially as
described.
10. The method of operating furnaces, consisting in charging in substantially the
entire body of fuel at a lower level than and concentrically around the descending
charge of metal, admitting air above the zone of fusion to unite with the carbonic
oxide rising from the fuel and burning the same in contact with the unmelted
metal substantially as and for the purposes described.
11. A furnace, having above its crucible, one or more fuel charging openings,
one or more metal charging openings, above the fuel charging openings, and an air
inlet or inlets between the fuel and metal charging openings; substantially as and
for the purposes described.
Dated this 28th day of February 1895.
W. H. MUNNS,
Agent for Applicant..