Note: Descriptions are shown in the official language in which they were submitted.
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TUYERE FOR METALLURGICAL VESSELS
BACKGROUND OF THE INYENTION
This invention relates to tuyeres for metallurgical vessels
and, more particularly, to submerged gas tuyeres used in
smelting and refining vessels.
Many metallurgical operations are carried out at high
temperatures in refractory-lined furnaces provided with one
or more submerged gas tuyeres through which oxidizing,
reducing or inert gases are supplied to the furnace charge.
As maintenance of the furnace lining and replacement of
tuyeres, mainly as a result of erosion and chemical
reaction, are major costs, much effort is spent on the
design of tuyeres. A common method for alleviating
deterioration problems is by cooling the furnace wall and
lS the tuyeres, such as by using cooling fluids, shielding
fluids or solid cooling elements, or by using protective
sheaths, coatings or the like. Protection is also provided
by causing a porous encrustation of solid material to build
up at the tip of the tuyere.
BRIEF DESCRIPTION OF PRIOR ART
:
The prior art on cooling furnace walls and on gas injectors
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such as tuyeres and lances is extenslve. The following
patents are recited by way of examples. Water cooling of
refractory furnace linings is disclosed in US Pa~ents 1 703
519, 3 593 975, 3 598 382, 3 679 194 and 3 843 106. The
use in a furnace wall of solid or annular cooling members,
of which a portion external to the wall may be cooled, is
disclosed in CA Patent 1 006 695. The use of copper tubes
in a refractory wall is disclosed in US Patent 2 829 879.
Examples of the use of a protective fluid with a
concentric-tube injector can be found in US Patents 3 397
878, 3 706 549, 3 988 148, 4 251 ~71, 4 417 723, 4 424 955,
4 435 211, 4 449 701, 4 734 129, 4 759 532, 4 792 126 and
4 795 138, in CA Patent 1 141 168, and in SV Patent 500
239. The formation of a protective layer or encrustation
on the furnace wall or at the yas injector is disclosed in
some of the above-named patents. The use of a refractory,
re~ractory-coated, -sheathed or -fllled pipe for an
injector is disclosed in US Patents 3 395 910, 4 417 723,
4 783 057 and 4 783 058. A fluid-cooled tuyere having a
cooling chamber for circulatin~ fluid and an adjacent solid
heat-sink wall is disclosed in US Patent 4 572 482.
According to SU Patent 452 599, a tuyere has a nozzle with
an expansion chamber filled with aluminum and adjacent a
fluid~cooled housing; life is enhanced by a crystallized
metal layer formed on the outside surface of the nozzle.
The injectors of the prior art have a number of important
disadvantages. The use of water for cooling requires
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extreme caution as any leaking of water into the high-
temperature furnace charge may cause explosions. The use
of solid cooling elements is subject to a fixed rate of
heat transfer, and is also dependent on the thermal
conductivity of the solid material. Any protective sheaths
or coatings on a tuyere are subject to erosion when exposed
to high-temperature furnace contents. Many of the prior
art lances and tuyeres extend through the wall of the
furnace into its contents, and are, therefore, subject to
chemical or erosive physical attack.
SUMMARY OF THE INVENTION
We have now found that the erosion of the furnace lining
and of a submerged gas tuyere may be alleviated by using a
solid metal tuyere body provided with a number of water-
cooled bores and a central gas feed pipe. The tuyere is
embedded in refractory and the tip or end of the tuyere is
flush with the inner wall 50 that no part of the tuyere
except its texminal surface is exposed to the furnace
contents. The mass of the tuyere body and the water-
cooling of the water-cooled bores in the body together
provide cooling that is effective in reducing erosion of
the furnace refractory wall and the tuyere.
The tuyere comprises a solid metal tuyere body of a,
preferably, generally cylindrical shape and with a good
thermal conductivity. The tuyere body has a central gas
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feed bore and a number of circumferentially-located water-
cooled bores. The central gas feed bore contains a gas
feed pipe, which is connected at one end with a source of
gas, its other end being substantially flush with the end
surface of the tuyere body. Alternatively, the central gas
feed bore contains a gas feed inner pipe and a concentric
shielding gas outer pipe spaced from each other to provide
an annulus between the pipes for passing a shielding gas.
Each water-cooled bore extends partially into the tuyere
body leaving sufficient (unbored) material of the tuyere
body to provide safe operation. Each water-cooled bore is
provided with means to provide a water passage for
circulating water along the length of the water-cooled bore
so that water fed into the bore passes to the end of the
bore and returns in the bore to its other end. In a
preferred embodiment, each bore i9 provided with a water
cooling pipe spaced from the bore wall so that water fed
into the pipe passes to the end of the bore and returns
through an annulus between the pipe and its bore.
The tuyere is attached to a cooling header. The cooling
header has a central passage for the gas feed pipe or the
gas and shielding gas concentric pipes, and has means for
providing a water passage for circulating water~ In the
preferred embodiment, the header has means for attaching
each of the cooling water pipes to and in the header. The
header provides a passage for cooling water into and
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through the header, the cooling pipes, the annulus between
the water cooling pipes and the water-cooled bores, and
through and out of the header. According to an alternative
embodiment, the water-cooled bore and the cooling header
are divided in an inward water passage and a outward water
passage by a central plate.
It is an object of the present invention to provide a
tuyere for a metallurgical vessel. It is another object to
reduce erosion of the wall of the metallurgical vessel and
the tuyere.
Accordingly, there is provided a tuyere for a metallurgical
vessel comprising a tuyere body made of a solid metal; a
gas feed bore through said tuyere body on its longitudinal
axis; at least one gas feed pipe in said gas feed bore; at
least one water-cooled bore in said tuyere body, said
water-cooled bore being situated in and partly penetrating
into said body parallel to and between the outer wall of
said body alld said gas feed bore and having a water passage
for circulating water along the length of the water-cooled
bore; a water cooling header attached to said tuyere body
external to said vessel; a water inlet and a water outlet
in said cooling header; and means in said cooling header to
communicate water from said water inlet to said water
passage and from the water pa sage to said water outlet.
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BRIEF DESCRIPTION OF DRAWINGS
The objects of the invention will be apparent from the
following description taken in conjunction with the
accompanying drawings wherein:
Figure 1 is a section of a tuyere according to the
invention;
Figure 2 is a section of an alternative embodiment of the
tuyere as shown in Figure 1;
Figure 3 is a perspective view, partly cut away, of a
cooling header in relation to the tuyere of Figure 2;
Figure 4 is an exploded view and a parti.al cut-away of the
cooling header of Figure 3;
Figure 5 is a perspective view, partly cut~away, of another
embodiment of the cooling header~
In the Figures, like numbers refer to like parts.
DETAILED DESCRIPTION
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With reference to Figures 1 and 2, the tuyere, generally
indicated with 10, comprises a generally cylindrically-
shaped tuyere body 11. Although the description is made
with reference to a generally cylindrically-shaped tuyere
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body, it is understood that other shapes such as square or
tapered bodies symmetrical about their longitudinal axes
can also be used. The tapered bodies may be tapered over
the full or partial lengths of the bodies towards end face
12. Tuyere body 11 is a solid body made of a metal. The
criteria for the choice of metal for the tuyere body are
good thermal conductivity and a hlgh resistance to
oxidation. Suitable metals are, for example, copper,
certain copper alloys, or stainless steels. Tuyere body 11
has two opposite, substantially flat end faces 12 and 13
perpendicular to its longitudinal axis.
Tuyere body 11 has a central gas feed bore 14 adapted to
contain the gas feed pipe 15. Gas feed bore 14 may have
the same diameter all the way through tuyere body 11 as
shown in Figure 2, or may have a smaller diameter terminal
section 16 over a short portion of its length at end face
12, as shown in Figure 1. Gas feed pipe 15 is inserted in
gas feed bore 14 such that one end is substantially flush
with end face 12, and its other end extends past the
opposite end face 13 where it is connected to a source of
gas (not shown). In the tuyere body of Figure 1, one end
of gas feed pipe 15 fittingly inserts in and passes through
terminal section 16 of gas feed bore 14. If desired, gas
feed pipe 15 may have a smaller diameter terminal nozzle
portion 15a through terminal section 16. The other end of
gas feed pipe 15 is maintained in fixed position with
relation to gas feed bore 14 by pressure plate 30, to be
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described. ~s shown in Figure 2, gas feed bore 14 contains
an o~lter shield gas feed pipe 17. Gas feed pipe 15 is
concentrically positioned in outer shield gas feed pipe 17,
leaving a shield gas annulus 18 for shield gas between the
inner wall of shield gas feed pipe 17 and the outer wall of
gas feed pipe 15. Shield gas feed pipe 17 has one open end
substantially flush with end face 12 of ~uyere body 11, and
has a closed end 19 around the end of gas feed pipe 15
extending beyond tuyere face 13. Close to end 19 of shield
gas feed pipe 17, pipe 17 has a connection 20 connected to
a source of shield gas (not shown). Gas feed pipe 15 is
malntained in fixed and spaced relation to shield gas feed
pipe 17 by tack welds along its length.
Tuyere body 11 has at least one water--cooled bore 21, as
shown, penetrating partly into body 11 parallel to and
between outer wall lla of the body and gas feed bore 14.
More than one bore 21 may be present such as, for example,
three water-cooled bores 21 concentrically located to gas
feed bore 14. The bores are preferably equally spaced.
Water-cooled bore 21 has a bottom 22, and has a depth
sufficient to provide adequate cooling while also providing
sufficient mass of the tuyere body between bottom 22 and
end face 12 to prevent any water from reaching the furnace
charge. Each water-cooled bore 21 is provided with a water
passage for circulating water along the length of the bore.
In one embodiment of the invention, water-cooled bore 21
may be provided with a longitudinal central plate 40
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(Figure 5). Plate 40 substantially divides bore 21 into
two halves which form outward water passage ~1 and inward
water passage 42 substantially along the length of bore 21,
passages 41 and 42 being connected to each other in
proximity to and spaced from end 22 to form a continuous
water passage through bore 21. In a preferred embodiment,
(Figures 3 and 4) the water passage is provided by a water
cooling pipe 23 inserted in spaced relation into water-
cooled bore 21 almost to the bottom 22 of bore 21, such
that a water passage in the form of a cooling water annulus
29 is provided between the wall of pipe 23 and bore 21, and
a space is provided between the one end of pipe 23 and
bottom 22 of bore 21. The other end of water cooling pipe
23 is held in fixed, spaced relation in bore 21 by water
cooling header 100, to be described. The diameter of the
water-cooled bore 21 and water cooling pipe 23 are chosen
such that an adequate flow of water can be provided that
supplies the desired degree of cooling. The cross section
of tuyere body 11 should be at least sufficient for
accomodating the gas feed bore 14 and at least one water-
cooled bore 21, with inserted gas feed pipe lS or gas feed
pipe lS and shield gas feed pipe 17, and water cooling pipe
23, respectively, while providing a sufficient mass for
effective cooling as well as continuous, safe operation.
The length of tuyere body 11 is such that the body passes
through the refractory wall of the metallurgical vessel,
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end face 12 being substantially flush with the inner
surface of the vessel wall, and end face 13 protruding some
small distance beyond and outside the surface of the outer
vessel wall.
Suitable means (not shown) are provided to mount the tuyere
10 onto the furnace, the tuyere fittingly passing through
the refracto~y of the vessel wall. Optionally, the tuyere
body may be provided with an end cap 24, as shown with
interrupted lines in Figure 2. End cap 24 may be shrunk-
fit over the end of tuyere body ll. If desired, a portion
of tuyere body ll may be machined to provide a shoulder 25
to accommodate end cap 24. An end cap may be provided in
cases wherein the material being treated in the
metallurgical vessel is not conducive to the formation of
a suitable encrustation on the end of the tuyere.
Tuyere 10 may also be provided with a thermocouple well 26,
as shown in Figure l, to hold a thermocouple (not shown)
for measuring the temperature of the tuyere body ll at a
point in the tuyere body ll indicated with 27, the point
being preferably located between the bottom 22 of a water-
cooled bore 21 and the face 12 of the tuyere. Tuyere body
ll is attached to a water cooling header 100, to be
described, by means of a pressure plate 30 and fastening
means.
With reference to Figure 3, the water cooling header 100 is
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11
adapted for the feeding of cooling water to the water-
cooled bore 21 in tuyere body 11. Header 100 has means for
the gas feed pipe 15 and the shield gas feed pipe 17 to
pass through the header. A thermo couple passage 32 is
provided in and through header 100 which is in alignment
with thermocouple well 26 in tuyere body 11. Header 100 i5
attached to the tuyere body 11 by pressure plate 30 and
fastening means such as studs or bolts 28 threaded into
tuyere body 11. Pressure pla~e 30 has a central opening 31
for fittingly holding gas feed pipe 15 ~Figure 1) or shield
gas feed pipe 17 (Figure 2) which pass through opening 31.
Water cooling header 100 may be of a cast or welded
construction, and has generally the same shape as the cross
section of tuyere body 11.
Water cooling header 100 consists of an inner header plate
101, a centre header plate 102 and an outer header plate
103, inner plate 101 being located adjacent tuyere body 11.
The inner header plate 101 and the outer header plate 103
are attached to or integral with the end of a header body
104 in parallel spaced relation, and centre header plate
102 is in header body 104 intermediate and parallel to the
inner and outer plates 101 and 103. Centre header plate
102 provides means to physically separate water flowing
into the header from water flowing from the header, as will
; 25 be explained. Centrally in and passing through the
parallel plates 101, 102 and 103 is a central gas feed pipe
passage 105 adapted to contain the gas feed pipe 15 or the
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outer shield gas feed pipe 17 with gas feed pipe 15
therein. The diameter of pipe passage 10~ is substantially
the same as the diameter of central gas feed bore 14 in
tuyere body 11.
A water inlet 106 is suitably located on the circumference
and through ~he wall of and in header body 104 between
outer header plate 103 and cen~re header plate 102 Water
inlet 106 is conneoted to a source of cooling water (not
shown). A water outlet 107 is provided on the
circumference and through the wali of and in header body
104 between centre header plate 102 and inner header plate
101. Water outlet 107 is connected to means tnot shown)
for discharging water from header 100. Water inlet 106 and
outlet 107 may be suitably located anywhere on the
circumference of header body 104.
According to the preferred embodiment, water cooling header
100 is provided with attachment means generally indicated
with 108 in an opening 108a in centre plate 102 for
attachment of the at least one water cooling pipe 23.
Attachment means 108 comprises, preferably, a half coupling
109 in opening 108a in the peripheral portion 110 of centre
plate 102. Half coupling 109 is provided with a threaded
; : portion 111 for attachment of the threaded mating end of a
water cooling pipe 23. In case of more than one water
oooling pipe, the~half couplings 109 are evenly spaced in
the pe~ripheral portion:llO of centre plate 10~ around pipe
.
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105. Opening 112 corresponding and in axial alignment with
half coupling 109 is provided in the peripheral portion of
inner header plate 101 so that water cooling pipe 23
attached to half coupling 109 passes through inner header
S plate 101. Opening 112 has the same diameter as that of a
water-cooled bore 21 in the tuyere body 11, leaving an
annulus 29 for cooling water.
Preferably, tuyere body 11 has three water-cooled bores 21,
the centres of bores 21, corresponding with centre lines
through openings 108a with half couplings 109 and openings
112, being equally spaced Oll a circle concentric to the
longitudinal axis of the tuyere.
Water cooling header 100 is attached to tuyere body 11 by
means of pressure plate 30 and suitable fastening means
such as studs or bolts 28. The fastening means each pass
through pipe nipples 113 attached to or integral with and
through plates 101, 102 and 103. Preferably, three
fastening means are used, their centre lines being on the
same circle as the centre lines through half couplings 109
and openings 112 for water cooling pipes 23, the fastening
means with nipples 113 and the water cooling pipes 23
alternating at equal distances.
To obtain a water-tight connection between cooling header
100 and tuyere body 11, a groove 114 is provided in the
surface of lnner header plate 101 adjacent tuyere body 11
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and around each of the openings 112 for holding an "O" ring
(not shown). When cooling header 100 is attached to tuyere
body 11 by tightening the pressure plate with the fastening
means, the "O" rings provide a water-tight connection.
A sealed water inlet chamber 115 is formed in header body
104 between the inner wall of body 104, centre plate 102
and outer plate 103, water ingress being provided by water
inlet 106 and water egres~ through attachment means 108.
A sealed water outlet chamber 116 is formed in header body
104 between the inner wall of body 104, centre plate 102
; and inner plate 101, water ingress being provided by
annulus 29 in opening 112 and water egress through water
outlet 107. This construction physically separates water
; inlet 106 from outlet 107. A continuous water passage 117,
schematically indicated with an arrowed line, is formed
from water inlet 106 into water inlet chamber 115, through
attachrnent means 108, through water cooling pipe 23,
cooling water annulus 29, and through water outlet chamber
116 to water outlet 107. If desired, the direction of
water through water passage 117 may be reversedO
According to an alternative embodiment (Figure 5) of the
means in cooling header 100 to communicate water from water
inlet 106 through the water passage and from the water
passage to water outlet 107, longitudinal central plate 40
in water-cooled bore 21 extends into header 100 through
openings 112 and 108a. Openings 108a and 112 are provided
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with a pipe nipple 43 attached in and to or integral with
the openings and between plates 101 and 102. The end 44 of
pipe nipple 43 in opening 108a is half closed at 45 and
half open at 46 so that sealed water chamber 115 is in
communication with inward water passage 42. Nipple 43 also
has an opening 47 in its side ~o that outward water passage
41, closed at its end at ss with a substantially semi-
circular plate, is in communication with sealed water
outlet chamber 116. Water chambers 115 and 116 are thus
physically separated and continuous water passage 117 for
~ooling water is formed from water inlet 106 into chamber
llS, through opening 46 into inward water passage 42 to end
22 of bore 21, through outward water passage gl, through
opening 47 into water chamber 116 and to water outlet 107.
As can be seen from the above description, means are
provided in the cooling header to communicate water from
water inlet 106 to the water passage and from the water
passage to water outlet 107.
The invention will now be illustrated by means of the
following non-limitative examples.
Example 1
A tuyere according to the invention described with
reference to Figure 1 was installed in a sidewall near the
bottom of a lead softening furnace operating at a
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temperature of 620C. The tuyere had a cylindrical copper
tuyere body with a length of 387 mm and a diameter of 152
mm. The body had a central gas feed pipe bore with a
diameter of 24 mm and a nozzle bore portion with a length
of 52 mm and a diameter of 9 mm. The gas feed pipe
inserted in the gas feed pipe bore had a diameter of 22 mm
outside and 12.7 mm inside, and had a nozzle portion 70 mm
long with a 9 mm outside diameter and an inside diameter of
4 mm~ The tuyere had a thermocouple well, its end being 75
mm from the face of the tuyere.
The tuyere had three water-cooled bores at 120 spacings,
each with a length of 222 mm and a diameter of 26 mm.
Water cooling pipes with an inside diame~er of 12.7 mm and
an outside diameter of 21 mm were inserted in the bores,
leaving a space of 5 mm between the end of the pipe and the
end of the bore, and leaving an annulus with a w.idth of 2.5
mm between pipe and bore.
The cooling header, attached to the tuyere body with three
bolts, was 92 mm long and had a diameter of 16B mm.
Threaded ends of the water cooling pipes were fixedly
attached in half couplings in the centre plate of the
header.
Oxygen was passed through the gas feed pipe at a rate of 12
normal m3/h and water was passed through the cooling header
and the water cooling pipes in the water-cooled bores at a
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rate of 600 L/h. During operation at these rates, the
water inlet temperature was 7C and the outlet temperature
17C. The heat flux at the tuyere end surface was 300,000
kcal/m2.h. The temperature recorded with the termocouple
was 210C. A distinct encrustation was formed on the end of
the tuyere. After one month of operation no discernable
deterioration of the tuyere was observed, and little
erosi4n of refractory material around the tuyere occurred.
Example 2
A submerged bottom tuyere for a QSL lead smelting furnace
was constructed as described with reference to Figure 2.
The cylindrical copper tuyere body was 600 mm long with a
diameter of 152 mm. The central gas feed bore had a
diameter of 38.1 mm. A shield gas feed pipe with an
; 15 outside diameter of 38.1 mm and an inside diameter of 31.29
mm was fittingly inserted in the gas feed bore. ~ gas feed
pipe with an outside diameter of 29.99 mm and an inside
diameter of 24.3 mm was centrally inserted in and tack
welded to the shield gas feed pipe, leaving an annulus for
the shield gas with a width of 1.3 mm. The tuyere body had
three water-cooled bores with a length of 410 mm and a
diameter of 26 mm. The water cooling pipes and the cooling
header were the same as in the tuyere of Example 1.
It is understood that changes and modifications may be made
in the embodiments of the invention without departing from
the scope of the appended claims.
