U.S. patent number 3,712,602 [Application Number 05/117,275] was granted by the patent office on 1973-01-23 for blast furnace tuyere and method of operating same.
This patent grant is currently assigned to United States Steel Corporation. Invention is credited to Marinus L. Brown, Paul J. La Rosa, Charles M. Sciulli, Jr..
United States Patent |
3,712,602 |
Brown , et al. |
January 23, 1973 |
BLAST FURNACE TUYERE AND METHOD OF OPERATING SAME
Abstract
A blast furnace tuyere having a nose portion and a rear portion,
each of which are independently water cooled by separate
circulation systems. The nose portion thereof comprises nothing
more than helically wound tubing, with each end thereof extending
back through the rear portion to provide an inlet and outlet for
the cooling water.
Inventors: |
Brown; Marinus L. (Pittsburgh,
PA), La Rosa; Paul J. (Allison Park, PA), Sciulli, Jr.;
Charles M. (Pittsburgh, PA) |
Assignee: |
United States Steel Corporation
(Pittsburgh, PA)
|
Family
ID: |
22371959 |
Appl.
No.: |
05/117,275 |
Filed: |
February 22, 1971 |
Current U.S.
Class: |
122/6.6 |
Current CPC
Class: |
C21B
7/16 (20130101) |
Current International
Class: |
C21B
7/00 (20060101); C21B 7/16 (20060101); C21b
007/16 () |
Field of
Search: |
;110/182.5 ;122/6.6
;266/41 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dost; Gerald A.
Claims
We claim:
1. A blast furnace tuyere comprising a rear member and a nose
member joined together to form a single air blast opening
therethrough, said rear member formed of a cast material and having
a base portion and a substantially annular chamber therein and
openings through said base portion for circulating cooling water
through said chamber, said nose member being formed of helically
wound tubing having linear end portions thereof extending back
through said air blast opening and through said base portion of the
rear member for circulating cooling water through said tubing
independently of said openings for circulating cooling water
through the chamber in said rear member.
Description
BACKGROUND OF THE INVENTION
Because of the excessive heat to which they are subjected, it is
well known that blast furnace tuyeres are relatively short-lived.
Although many tuyere designs have been advanced through the years
in attempts to extend tuyere life, improvements have not been
greatly significant. Tuyeres of even the most advanced designs
typically last no more than about 85 to 100 days during continuous
operation.
It is also well known that tuyere failure most commonly occurs in
the nose portion thereof where the tuyere comes into direct contact
with the hot molten metal and/or slag within the furnace. Even
though tuyeres are usually water cooled, continuous furnace
operation soon creates conditions whereby the cooling water is
incapable of preventing failure. That is, in normal operation,
tuyeres operate with nucleated boiling of the cooling water in the
nose portion. Sooner or later, there is sufficient heat loading on
the tuyere nose to cause the cooling water to go into film boiling.
Film boiling results in a lower heat transfer from the adjacent
surface, causing a rapid increase in temperature. When the melting
temperature of the tuyere material is reached, failure or burn-out
begins. When a tuyere failure does occur, the cooling water enters
the furnace charge causing a temperature drop as well as other
complications due to the rapid boiling thereof. It is therefore
imperative that upon tuyere failure, the cooling water supply
should be shut-off and the failed tuyere immediately replaced.
SUMMARY OF THE INVENTIOn
An object of this invention is to provide an improved, longer life,
blast furnace tuyere having independent forward and rearward
cooling chambers so that the nose portion and the rearward portion
are cooled by separate systems to thereby increase cooling
efficiency, particularly in the nose portion, and to permit
continued, though limited, operation even after the nose portion
has failed.
Another object of this invention is to provide a blast furnace
tuyere having separate forward and rearward cooling chambers in
which at least the forward chamber comprises unprotected helically
wound tubing to increase heat transfer efficiency and prolong
tuyere life.
A further object of this invention is to provide a blast furnace
tuyere having a nose portion which is readily separable from the
rear portion so that upon failure of the nose portion, the tuyere
can be easily repaired merely by replacing the separable nose
portion.
These and other objects and advantages will become apparent from
the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an outside end view of a blast furnace tuyere in
accordance with one embodiment of this invention;
FIG. 2 is a sectional side view of the blast furnace tuyere shown
in FIG. 1 taken at line II--II;
FIG. 3 is a sectional view of the wall of the tuyere shown in FIG.
1, taken at line III--III;
FIG. 4 is another sectional view of the tuyere wall taken at line
IV--IV, FIG. 1;
FIG. 5 is a further sectional view of the tuyere wall taken at line
V--V; and
FIG. 6 is a sectional side view of a blast furnace tuyere in
accordance with another embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIGS. 1 through 5, one embodiment of the blast
furnace tuyere of this invention comprises a rear member 10, having
frusto-conical walls 12 defining an air blast opening 14
therethrough, and a frusto-conical nose member 30 consisting of
helically wound tubing 32 forming an extension of the air blast
opening 14.
The rear member 10 is formed of cast metal, preferably copper or
alloys thereof, and although the outer surface is substantially
frusto-conical in configuration, the air blast opening 14 is
frusto-conical only in the forward part thereof. That is, a heavy
flange 16 is provided around the inside portion of walls 12 to
provide a flat ring shaped surface 18 at the base of member 10, as
shown in FIG. 2. A chamber 20, for receiving cooling water, is
provided within walls 12 partially encircling opening 14. An inlet
port 22, communicating with chamber 20, is provided through surface
18 to admit cooling water into chamber 20. Similarly, an outlet
port 24 is provided through surface 18 to discharge water from
chamber 20. If desired, a gas port 26, as shown in FIG. 2, may be
provided through wall 12 to introduce natural gas into the hot air
blast passing through opening 14.
The nose member 30 is preferably formed from stainless steel
tubing, and is secured to the small forward end of rear member 10
by any suitable means such as spot welding. The helically wound
tubing 32 is wound and positioned so that the windings form an
extension of walls 12 and opening 14. Both ends of the helical
tubing 32 extend back within opening 14 to provide a cooling water
inlet and outlet. Specifically, a cooling water inlet pipe 34 is
provided by extending the forward end of tubing 32 back through
opening 14 parallel to inside wall 12 and through flange 16 to
inlet port 36. Similarly, a cooling water outlet pipe 38 is
provided by similarly extending the other end of tubing 32 to
outlet port 40. A continuous weld and/or high temperature adhesive
should be applied between tube layers to prevent the hot blast from
exiting therebetween.
In operation, the tuyeres are of course inserted into openings in
the blast furnace side wall (not shown) and a blow pipe (not shown)
is secured against opening 14 at surface 18. A pair of water inlet
lines (not shown) are connected to inlet ports 22 and 36, and a
pair of outlet lines (not shown) are connected to outlet ports 24
and 40.
The cooling water circulating through nose member 30 is first
admitted to the extreme forward end thereof so that the water at
its coolest temperature is first subjected to the hottest part of
the tuyere where maximum heat transfer is most essential. Since the
nose member 30 comprises nothing more than coiled tubing 32, the
cooling water passing therethrough has a smooth unobstructed path
with no sharp corners, pockets or restrictions, thus allowing water
flow with a minimum resistance and hence optimum cooling
efficiency. Furthermore, since the cooling water passing through
nose member 30 does not also serve to cool the base portion 10, the
resistance to water flow is even further minimized. The rear member
10 is of course water cooled independently. Since the cooling water
passing through rear member 10 is not preheated by first passing
through the nose member 30, the rear member 10 is kept cooler than
those tuyeres having a single cooling system, and will therefore
help to keep nose member 30 somewhat cooler. All these factors will
combine therefore to keep nose member 30 cooler than has been
possible with prior art tuyeres, and hence enhance the life of the
tuyere. That is, the cooling water in the nose member 30 of the
above tuyere develops a much higher velocity at lower flow rates
than can prior art tuyeres. The increased water velocity of course
increases heat transfer from the tube 32. The water velocity
obtained in conventional tuyeres is generally less than 2 feet per
second at volumetric flow rates of 25 gpm, whereas the above tuyere
develops a water velocity of about 20 fps in the nose member 30 at
a flow rate of only 15 gpm. This provides a further advantage in
that less water per unit of time will enter the blast furnace in
the event of failure.
Upon continued operation, the nose member 30 will of course fail
eventually. Because of the double cooling system, however, the
furnace operator may, if he wishes, merely shut off the cooling
water to the nose member 30. Although this will cause the nose
member 30 to be quickly melted away, the rear member 10 would still
be water cooled, and hence the operator could continue to operate
the furnace without interruption for a limited time until a more
opportune time for a tuyere change.
Since rear member 10 would remain intact after failure of the nose
member 30, it would of course be possible to reuse rear member 10
by merely replacing a new nose member 30 thereon.
In order to realize the primary object of this invention, i.e.,
enhanced tuyere life, certain structural and operating conditions
must be met. The table below provides the essential structural and
operating conditions to this end and the preferred values
therefor.
TABLE
Essential Preferred
__________________________________________________________________________
Thermal Conductivity of 50-220 140-190 Fabricating Material
Btu/ft-hr-F Btu/ft-hr-F Tube Wall Thickness 1/16 inch 1/8-1/4 inch
minimum Rear Member Wall 1/4 inch 1/4-1-1/2 inch Thickness minimum
Water Velocity in 10-60 ft./sec. 20-30 ft./sec. Nose Member Water
velocity in 1-10 ft./sec. 2-7 ft./sec. Rear Member Inlet Water
Pressure 15-150 20-60 lb./sq. in. lb./sq. in. Inlet Water
Temperature less than 120.degree.F 40-80.degree.F
__________________________________________________________________________
another embodiment of this invention is shown in FIG. 6 and is
substantially the same as the embodiment described above except
that the rear member 10A is formed from helically wound tubing as
is the nose portion 30A. In this embodiment, inlet and outlet pipes
for the cooling water are disposed outside the frusto-conical
tuyere walls merely to show an alternate position therefor.
Considering the second tuyere embodiment in more detail, the rear
member 10A comprises helically wound tubing 50 axially secured to
an annular base flange 52. Base flange 52 is made entirely of plate
metal, i.e., two discs 54 and 56, each having a circular hole
therethrough, horizontally spaced apart by sleeve members 58 and
60. The structure thereby forms a portion of the air blast opening
14A having an annular chamber 62 therearound. The inner sleeve
member 58 extends beyond disc 56 to provide a sleeve over which
rests the helically wound tubing 50. The ends 64 and 66 of tubing
50 extend back through base flange 52 to provide a water inlet and
outlet respectively to the helical portion of tubing 50. Similarly,
the ends of tubing 32A forming the nose portion 30A must extend
back through base flange 52 to provide a water inlet and outlet for
the nose portion 30A. At least three confinement tubes 68, or other
suitable means, should be provided within chamber 62 to prevent the
water from mixing therein. In operation, this tuyere functions
substantially the same as described above for the first
embodiment.
* * * * *