Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROU~D OF THE INVENT ION
The present invention relates to cooling arrangements
for protecting the walls of metallurgical furnaces from heat,
and more particularly to shaft-furnace coolers~
The invention can be advantageously applied for
the protection of blast-furnace shells.
Because of elevated temperatures created in the
working space of a blast furnace, the shell-thereof is subjected
to severe heat. Therefore, special arrangements are called
for to insure mechanical strength of such shells and protect
them from heat loads. The arrangements in question are plate
coolers which are usually mounted on the furnace shell at the
side of the furnace working space.
It is modern practice to intensify the blast-furnace
process by raising the blast temperature, increasing the
amount of oxygen contained in the blast, or else by building
up pressure in the furnace space. The above factors are
detrimental to the operation of heat-protecting arrangements,
placing more stringent requirements upon their ability to
resist heat.
There are known in the art plate coolers which
comprise a cast-iron plate with built-in steel pipes whose
open ends extend beyond the plate and through the furnace
shell. The pipes are connected through said ends with the
furnace cooling circuit through which circulates a coolant,
such as industrial or chemically treated water, or vapour-
water mixture.
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In the course of the blast-furnace operation, the
plate is e~posed to heat loads which vary timewise. As a
result, the plate tends to change its geometrical dimensions,
expanding and contracting. The plate expansion and shrinkage
adversely affect the pipes which are rigidly connected
therewith. The process of manufacturing coolers is such that
it causes embrittlement of steel pipes which are subjected
to carbonization in the process of casting molten iron
therein. The ends of the pipes extending through the
furnace shell are usually we~lided thereto. With the iron
plate acting upon said pipes, there creates therein periodi-
cally variable pressures which bring about their destruction.
As a result, the coolant passing from the furnace cooling
circuit penetrates through the damaged pipe into the furnace
working space. This calls for higher fuel input per unit
of production because of the heat losses require~or the
evaporation of the escaped coolant. In some cases, the
penetration of considerable amount of coolant to the furnace
may even disrupt the furnace operating process.
At present, for lack of reliable and prompt trouble-
shooting techniques, it takes considerable time and human
effort to spot and disconnect the damaged pipe. The atten-
ding personnel involved in such operation are compelled
to work in the conditions of severe gas contamination and
high temperatures.
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It is deemed necessary to point out still another dis-
advantage of the hereinbefore described coolers. There is pro-
vided in the furnace cooling circuit, with a plurality of
coolers being connected thereto, gravity circulation of the
coolant. This type of the coolant circulation depends for its
rate on the average heat load acting on the coolers. With the
lining being broken away from the surface of the cooler plate,
the latter is exposed to severe heating which can be eliminated
only by increasing the rate of vapor-water mixture circulation
through the pipes intended for cooling the plate. As mentioned
above, however, the rate of circulation depends solely on the
average heat load acting on the group of coolers, which practi-
cally remains unaltered. Therefore, the increased amount of
heat effecting a separate plate results in greater amount of
vapor in the pipes cooling this plate, which, in turn, causes
its overheating and fusion.
A construction in accordance with the present
invention includes a cooler for a shaft furnace comprising a
plate adapted to protect the furnace wall body against the effect
of heat flux to which it is exposed and formed of two layers, a
high heat-conducting layer facing the furnace working space and
a low heat-conducting one presented to the furnace wall, a means
for cooling said plate, made in the form of metal pipes partially
filled with a coolant and sealed at the ends thereof, the longi-
tudinal axis of said pipes being parallel to the interfacial
plane of said layers, a cooling chamber arranged exteriorly of
the furnace wall body and having a coolant circulating there-
through, ends of said pipes partially filled with a coolant
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being rigidly connected to said plate, ends of said pipes free
from coolant, arranged slightly above those filled therewith
and mounted in said cooling chamber.
In other words, in order to improve the cooling of
the cooler plate by a sudden increase of the flow rate of heat
affecting said cooler and eliminating the possibility of the
water penetration into a metallurgical furnace, there has been
developed a cooler comprising a plate with pipes whose ends at
one side thereof are built into said plate, filled with a
coolant and sealed. The other ends of the pipes, which are
mounted higher than those filled with water, extend beyond the
plate and pass through the furnace shell into a cooling
chamber wherein they
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are fixed. Circulating in the cooling chamber is a coolant.
The cooling chamber is arranged exteriorly of the furnace
and connected to the cooling circuit thereof.
The improved cooling of the plate of each separate
cooler has been accomplished by way of sealing the ends of
the cooler plate pipes, whereby each pipe is provided with its
own circuit wherein the vapour-water mixture circulation is
determined by the heat loads acting on such circuit. The
rate of vapour-water mixture circulation in the plate-cooling
pipes increases with the heat load acting on the plate,
thereby providing for reliab~e cooling of said plate.
The use of such cooler practically eliminates the
coolant penetration to the furnace in case of damage of the
sealed pipe, since there is but a negligible amount of
coolant contained therein, with the furnace cooling circuit,
wherein circulates water, being separated from the interior
of the damaged pipe by the wall of the latter. This being
the cooler construction,the pipe is surrounded with the
cast-iron plate, having therefore, its entire surface exposed
to heat. It happens that certain heat flows cause abundant
formation of vapour in the part of the pipe which is fixed
in the plate, and the condensate, formed in the free part of
the pipe due to condensation of vapour passing there~nto
through a cooling chamber, is prevented from descending to the
lower part of the pipe. Thus, the water from the part of
the pipe fixed in the plate is rushed to the upper part of
the pipe. This results in the overheating of the pipe and
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plate walls because of the absence of the heat outlet leading
to the furnace cooling circuit, and the destruction of the
cooler thus becomes in~vitable.
To eliminate the above-mentioned disadvantage,
there has been proposed a cooler for a metallurgical shaft
furnace, comprising a plate with built-in pipes whose ends
at one side thereof are filled with a coolant and sealed.
Ihe other ends of said pipes are disposed above tho~e filled
with the coolant and extend beyond the plate and through the
furnace shell into a cooling chamber to be fixed therein`,
said chamber being connected to the furnace cooling circuit
with a coolant circulating therethrough. Fitted into each
~aid pipe is a pipe--insert with a diameter substantially
lesq than that of the main pipe, so that open ends of the
inserted pipe have no contact with closed ends of the pipes,
the generatrix of the inserted pipe coming in contact with
that of the pipe facing the furnace shell.
The heat removed from the plate is used to heat
up the water in the ~ealed pipe. The resultant vapour-water
~ixture rises to the coolant-free end of the pipe wherein
the vapour is condensed on the pipe wall, cooled with the
coolant flowing through the cooling chamber and circulating
within the furnace cooling circuit, and then drainsdown
through the inserted pipe. In such a manner the coolant flow
is separated into two flows, namely: the vapour-water mixture
flow rising to the water-free end of the pipe, and the
condensate flow passing down to the portion of the pipe in
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contact with the plate. The cooler waC thus enabled to
function faultlessly in the conditions of severe heat flowing
out of the furnace working space, this being the advantage
over the previously described cooler.
However, the hereinabove described cooler is com-
plicated in construction due to the difficulty of fitting
smaller-diameter pipes into the plate-cooling pipes, the former
requiring complex configuration which ressembles that of the latter.
It is therefore an ob~ect of the present invention
to improve operating reliabl~ity of a shaft-furnace cooler by
means of providing reliable cooling of the cooler plate
exposed to heat evoled in metallurgical furnaces.
Another object of the invention is to increase
the furnace campaign by means of enhancing operating dura-
bility of coolers due to improving the heat resistance of
their plates.
Still another object of the invention is to
reduce the cooler weight.
SUMMARY OF THE I~VENTION
These and other objects of the invention are
accomplished by the provision of a cooler for metallurgical
furnaces, comprising a plate adapted to protect the furnace
walls against the heat effect and arranged in the way of
heat flow, and a means for cooling said plate, made in the
form of metal pipes filled with a coolant and sealed at ends
thereof, the coolant-containing ends of said pipes being
rigidly fixed in the plate while the coolant-free ends
thereof are mounted in a cooling chamber, with the coolant
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circulating therethrough, arranged exteriorly of the furnace
wall body, and the coolant-free ends of the pipes being
slightly above those containing the coolant, wherein,
according to the invention, the plate is formed of two
layers, namely, a high-heat-conducting layer and a low-heat-
conducting layer, the former facing the furnace working
space and the latter being presented to the furnace wall
body, the interfacial plane of said layers being parallel
to the longitudinal axis of said pipes.
Such constructional arrangement of the cooler plate
makes it possible to create in each plate-cooling pipe a
circulating flow of a definite structure.
Owing to the fact that the plate is made of two
layers, with the high-heat-conducting layer facing the
furnace working space and the low-heat-conducting one being
presented to the furnace wall body, the interfacial plane
of said layers running parallel to the longitudinal axis of
the plate-cooling pipes, there occurs in each of said pipes
a separation of the coolant flow into a vapour-water mixture
flow and that of water. The aforesaid separation takes
place due to non-uniform heating of the surfaces of said
pipes around their periphery. The part of the pipe which
faces the furnace working space and in contact with the
plate high-heat-conducting layer is heated more than that
in contact with the plate layer made of low-heat-conducting
material. In the part of the pipe interior passage which is
narrowed ~y the overheated walls thereof, there takes place
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vigorous vapour-forming process accompanied by an ascending
flow of vapour-water mixture. In the other part of the pipe
interior passage a flow of water unhinderedly passes down,
i.e. natural or gravity circulation of coolant is formed
within said pipe. Thus, favourable operating conditions
are created for the plate-cooling pipes and for the cooler
as a whole. Such circulating conditions in the pipes are
feasible to maintain within a definite rate of heat flow,
required for heating the plate and pipes. Excessive rate
of heat flow will upset the aforedescribed structure of the
coolant circulation in the pipes, an upwardly moving flow
of vapour-water mixture takes up the entire interior space
of the pipe, blocking the downward passage of water towards
the end of the pipe fixed in the plate, thereby disrupting
normal conditions of cooling the plate.
The above-mentioned problem finds its solution
in that each pipe is provided with a partition extending short
of the closed ends of the pipe and in parallel with the
longitudinal axis of the pipe, said partition defining two
cavities, one of which is a heat-absorbing cavity facing
the high-heat-conducting layer, the partition plane being
substantially coincident with the interfacial plane of the
two plate layers.
Such an arrangement of the partitions in the
cooler plate-cooling pipes is required to enable mechanical
separation of the ascending flow of vapour-water mixture formed
in the part of the pipe adjacent to the high-heat-conducting
layer, and the downwardly passing flow of water formed of
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the condensed vapour. Thus, the upwardly moving flow will
not impede the downward passage of water to the pipe end
fixed in the plate. This allows for reliable cooling of
the plate and affords protection to the furnace wall body
against the heat effect.
Since the pipes with partitions therein are simple
to manufacture, the latter are secured in the pipe longitudi-
nal central plane. Such an arrangement of the partition is
the best possible, with the latter being equal in width to
in diameter of the pipe into which it is inserted.
The passageway of the pipe is thus divided by
the partition into cavities equal in cross section, which,
however, is undesirable from the point of view of hydraulic
resistance to the ascending flow of vapour-water mixture in
the cavity adjacent the high-heat-conducting layer of the
plate. When the heat load acting on the plate and pipes
becomes excessive, a great amount of vapour is formed in
the cavity adjacent the high-heat-conducting layer, said
cavity being small enough in
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in cross-section to enable the escape of vapor. This being
the case, a directed coolant circulation in the pipes is dis-
rupted and the cooling of plate is deteriorated.
The above disadvantage is eliminated by way of dis-
placing the partition plane from the longitudinal central plane
of the pipe towards the furnace wall body by 0.1 to 0.3 of the
pipe inside diameter.
Such mounting of the partitions in the plate-cooling
pipes brings about an increase in the cross-sectional area of
the pipe cavity adjacent to the high heat-conducting layer of
the plate, i.e., hydraulic resistance to the ascending flow of
vapor-water mixture is reduced. This, in turn, results in
reliable circulation of coolant in the pipes.
Such an arrangement of the partitions makes for the
removal of specific heat loads on the order of 30X106 c2al
m h
through the cross-sectional area of the pipe cavity adjacent
to the high heat-conducting layer without upsetting the coolant
circulation in the pipe.
The high heat-conducting layer of the two-layer plate
is preferably manufactured from such material as heat-resistant
iron, and the low heat-conducting layer from heat-resistant
concrete. Since specific weight of concrete is considerably
less than that of cast iron, the cooler plate is reduced in
weight.
With a purpose of enhancing heat resistance of the high
heat-conducting layer, the latter is formed of individual
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bars which are mounted on the pipes for free movement during
thermal expansion along the axes of the pipes.
Due to the fact that t~e cooler in accordance with the
invention is constructed so that the plate thereof consists of
two layers, namely, a high heat-conducting layer and a low
heat-conducting one, and the pipes are provided with partitions,
it became possible to considerably expand the operating range
of heat loads which fail to affect the cooler plate being under
effective cooling protection of the pipes, and thus to enhancing
heat resistance of the cooler. It has been found feasible to
make use of the pipes for cooling purposes of metallurgical
installations, which are sealed at their ends and filled with
a coolant, the ends of said pipes at one side being rigidly
fixed in the plate and extending at the other side beyond the
plate and through the furnace wall body into a cooling chamber
to be fixed therein. This allows for removing severe heat
fluxes which arise in individual coolers independently of
moderate heat fluxes; it also precludes the penetration of water
into the furnace working space in case of any damage to a
pipe; and makes it possible to reduce the weight of coolers
adapted for use on metallurgical installations.
These and other objects and features of the invention
will become more apparent from a specific embodiment thereof,
taken in conjunction with the accompanying drawings. In the
drawings:
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Fig. 1 is a longitudinal cross-sectional view of
a cooler according to the invention;
Fig. 2 is a cross-section taken along line II-II,
a low-heat-conducting layer is not shown,
Fig. 3 is a cross-section taken along line III-III
of Fig. 2, and
Fig. 4 is a cross-section taken along line IU-IV,
wherein a partition is constructed in accordarce with claim 6.
DESCRIPTION OF THE PREFERRED EMBOD~MENT
_ _ .
In the embodiment, a cooler for a blast furnace
comprises a two-layer plate l(see Fig. 1), of which layer
2 facing the furnace inner space is formed of individùal
cast-iron bars 3 extending horizontally for a length greater
than vertically, the other layer 4 thereof being presented
to a furnace wall 5 and formed of heat-resistant concrete.
The cooler plate 1 likewise incorporates at least two pipes
6, such as shown in Fig. 2, which pipes are partially filled
with a coolant and sealed at the ends thereof with plugs 7,
such as shown in Fig. 1, said pipes each being provided with
a partition 8 extending short of the plugs 7. The coolant-
filled end of the pipe 6 is mounted in the plate 1, the
coolant-free end of said pipe 6 being mounted within 2 cooling
chamber 9 arranged exteriorly of the furnace wall 5 and con-
nected to the furnace cooling circuit (not shown~.
The partition 8 divides the interior of the pipe
6 into two cavities, of which a heat-absorbing cavity 10
is adjacent to the high heat-conducting layer 2, the other
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cavity 11 being adjacent to the low heat-conducting layer 4
formed of heat-resistant concrete. Provided on the surface
of each bar 3, presented to the furnace wall 5, is a recess
such as shown at 12 in Fig. 3, adapted to receive the pipes
6 therein: the surfaces of said bars presented to the furnace
working space being formed with ribs 13 such as shown in
Fig. 1. The pipes 6 are interconnected by means of cleats
14, shown in Fig. 2. The interconnected pipes 6 are accom-
modated in the recesses 12 fitted in the bars 3. Each of
the bars 3 is fixed by means of pins 15, cast-in in the
interspaces between the recesses 12, on the pipes 6 with
the aid of plates, such as plate springs 16 which are secured
on said pipes 6 by screw nuts 17. To enable mounting the plate
1 on the furnace wall body 5 the pipes 6 have welded thereto
lugs 18, such as shown in Fig. 3, fitted with threaded holes
19 adapted to receive studs 20 therein. The described cooler
is secured on the furnace wall body 5 by means of the studs
20 and screw nuts 21. All the coolers are mounted on the
furnace wall body 5 so that a gap 22 is provided for a heat-
insulating material to be placed therein, the size of saidgap being determined by the height of the lug 18. To ~aci-
litate heat transfer from the bars 3 to the pipes 6, the
recesses 12 accommodate therein a layer 23 of heat-conducting
material.
The number of the bars 3 which make up the metal
layer 2 of the plate 1 is determi-ned by the cooler height
and width parameters so that the height-width ratio of the
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bar 3 be within the range of 2 to 4, respectively.
The number of the pipes 6 provided in the cooleris determined by the width of the plate 1, as well as by
the heat load acting on the cooler used in a given metallurgical
installation.
The diameter of the pipe 6 is selected in accordance
with a rigidity of the cooler construction and heat loads
acting thereupon.
The provision of the partition 8 in the pipe 6, as
well as its arrangement therein, is governed by heat loads
acting on the cooler and, consequently, by the heat loads
transferred through the cross-section of the pipe 6. The
cast-iron bars 3 of each cooler are heated with the heat of
the furnace working space, transferring the absorbed heat
through the heat-conducting layer 23 to the walls of the
cooling pipes 6. The transferred heat causes boiling of water
in the heat-abSorbing cavities 10 of the pipes 6, with the
resultant ascending flow of vapour-water mixture being formed
in each of said cavities. The heat passing up to the pipes
6 from the side of the concrete-made layer 4 is considerably
less in amount due to lower heat conductivity of heat-resistant
concrete as compared to that of metal. Therefore, the hy-
draulic resistance, created in the cavity 11 of the pipe 6,
to the downwardly passing flow of condensate formed in the
coolant-free end of the pipe 6 cooled by the coolant flowing
through the chamber 9, is very small. Thus a directed circula-
tion of the vapour-water mixture and water originates in the
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interior of the pipe 6, i.e. in the cavity 10 of the pipe
6 a flow of vapour-water mixture rises to the fluid-free end
of the pipe 6 wherein vapour is separated from water to be
thereby condensed, the water draining down through the
cavity 11 to the lower end of the pipe 6. In this manner
a reliable cooling is provided for the walls of the pipes 6
and bars 3, and the cooler thus fulfils its function aimed
at affording protection to the walls of furnaces from over-
heating and destruction.
When subjected to heating the bars 3 tend to increase
in dimensions, freely elongating in the direction parallel
to the axes of the pipes 6, with the fixture elements 15, 16
and 17 permitting such elongation~ As a result, the dis-
placement of the bars 3 cause no mechanical strains in the
pipes 6.
With heat fluxes passing up at a higher rate, which
fluxes are removed through the cavity 10 of the pipe 6, it
is advisable to install the partition 24, such as shown
in Fig. 4, in the plane offset from the longitudinal central
plane of the pipe towards the layer 4 by 0.1 to 0.3 of the
pipe inside diameter, which increases the cross-sectional
area of the cavity 10 and, consequently, decreases hydraulic
resistance to the ascending flow of vapour-water mixture
in the cavity 10.
Therefore, the cooler construction according to
the invention makes it possible to improve operational
reliability of the cooling system utilized on metallurgical
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installations due to enhancing the heat resistance of
cooler plates,
- provides for autonomous operation of each cooling
pipe, which permits of removing from the plate being cooled
vigorous heat fluxes forming in various places within the
furnace,
- increases campaign of metallurgical furnaces,
- brings down to minimum emergency situations due
to destruction of the furnace wallq,
- prevents penetration of water to the furnace working
space,
- reduces the cooler weight by 1.5 time.
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