Note: Descriptions are shown in the official language in which they were submitted.
1:151421
The present invention relates to metallurgy, and
more particularly it relates to apparatus for treating molten
metal with powdered products.
The invention can be utilized most advantageously in
treating molten metal in iron and steel teeming ladles, and
also in steel-making units, such as open-hearth furnaces,
converters, electric furnaces, etc.
The invention can be also utilized in non-ferrous
metallurgy.
There are known constructions of tuye~res or blowing
lances for treating molten metal with powdered products in
a gas flow, including a supply line from which the powdered
product is introduced into the metal together with its
carrier gas (cf- the US Patent No. 3,891,196, Int.Cl. C21C
7/100, dated June 24, 1975).
With the tuyere or blowing lance being of this
construction, there has been experienced a considerable degree
of carrying away the fine particles with ascending gas bubbles
from the molten metal body into the atmosphere of the unit.
There is further known a device for blowing powdered
products into molten metal with separation of the powdered
products from the carrier gas, including a supply line with
the bent end portion incorporating a separating baffle at
its outlet (cf. the Czechoslovak Patent No. 130,274, Cl- 18 b
7/100, published December 15, 1968).
In this construction the powdered product fed in
the flow of the carrier gas, while passing the bent portion
of the supply line, is urged by thP centrifugal forces toward
the outer portion of the curvilinear channel. It is
practically pure carrier gas which flowsadjacent to the inner
portion of curvilinear duct and is being cut off the flow
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with high concentration of the powdered product by the '
separating baffle.
Thus, the separation of the flow takes place within
the curvilinear portion of the supply pipe line wherein solid
particles are urged toward the outermost part of the curvi-
linear channel by the centrifugal forces, while practically
pure carrier gas flows adjacent to the innermost portion of
the channel. However, notwithstanding the incorporation of
the separating baffle or partition, the whole body of the
carrier gas passes through the outlet of the supp~y line,
entering the melt is a single stream with non-uniform
distribution of fine particles across its cross-section.
The known construction is characterized by a con-
siderable hydrodynamic resistance of the curvilinear portion
of the channel, which reduces the kinetic energy stored by
the stream and results in less deep penetration of the solid
particles into the molten metal, which reduces the volume of
the molten metal directly contacting the powdered product.
It is an object of the present invention to step up
the efficiency of using powdered products in metallurgical
processes.
It is another object of the invention to provide for
separation of a part of the stream of the carrier gas, and
thus to step up the concentration of the powdered product in
the gas flow penetrating the molten metal.
It is yet another object of the invention to reduce
the resistance of the tuyere to passage therethrough of the
stream of the carrier gas with entrained powdered product.
It is a further object of the present invention to
provide for directing a part of the carrier gas away, avoiding
its contact with the molten metal.
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These and other objects are attained in a tuyere for
injecting powdered products in a flow of a carrier gas into
molten metal, comprising a supply line the end portion of
which is adapted for separating a part of the carrier gas flow
from the mainstream flow, wherein, in accordance with the invention
the end portion of the supply line has in the wall thereof at
least one opening adjoined by a gas escape channel of which the
axis extends at an angle to the axis of the supply line.
The provision of the opening enables to withdraw a
part of the stream of the carrier gas from the supply line to
step up the concentration of the powdered product in the main-
stream flow downstream of the opening.
The arrangement is such that the carrier gas with-
drawn through the opening in the supply line would not mix with
the mainstream flow issuing from the outlet of the supply line.
Consequently, the disclosed tuyere provides for more efficient
utilization of powdered products supplied into the melt for
various reasons (carbonization, deoxidation, alloying of the
metal, desulfurization of the metal in ladles, etc-, while
reducing the amount of the powdered product finding its way into
the atmosphere; furthermore, it enables to use inexpensive and
readily available gases as the carrier gas, e.g. compressed air~
It is expedient that th~ opening should be in the
form of at least one annular slit.
The slit-like shape of the opening minimizes the
entrainment of fine particles in the carrier gas withdrawn from
the mainstream flow in the supply line.
It is preferable that the terminal portion of the
supply pipe should narrow down toward the outlet thereof,
otherwise the velocity of the mainstream flow would significantly
decrease on account of the part of the carrier gas having been
withdrawn, which would reduce accordingly the depth of penetra-
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~51421
tion of the stream of the carrier gas with the powdered productentrained therein into the molten metal, thus affecting the
efficiency of utilizing the powdered product.
Should it be necessary to avoid interaction of the
withdrawn part of the carrier gas with the molten metal, it
is expedient that a casing be mounted externally of the supply
line, coaxially therewith, to define with the supply line an
annular gap through which the part of the carrier gas can be
withdrawn from the mainstream flow.
In one embodiment of the invention the opening in
the tuyere through which the part of the carrier gas is with- -
drawn is defined as a gap between the end face of the terminal
portion of the supply line and the internal wall of the
narrowing-down terminal portion of the casing, located at some
distance downstream of the end face of the supply line and
having an outlet coaxial with the supply line of a diameter
not in excess of the diameter of the outlet of the supply line.
It is expedient that in the tuyere the gas escape
channels should be so arranged that their axes should extend
at an acute angle to the axis of the supply line, with their
outlets facing the molten metal being treated.
In one embodiment of the invention, the tuyere has
partitions or baffles mounted in the terminal portion thereof
to separate the gas escape channels from the main channel of
the supply line, these partitions or baffles having a varying
thickness increasing toward the outlets of the gas escape
channels, with the main channel being of a cross-section
varying from circular in the area adjoining the inlets of the
escape channels to slit-like at the outlet of the main channel.
Gwing to the varying thickness of the partitions or
baffles, the withdrawn part of the carrier gas penetrates the
molten metal at an angle relative to the mainstream flow.
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51421
It can be seen from the abovesaid that in every
embodiment of the tuyere in accordance with the invention
the fine particles-of the powdered product would not alter the
directicn of their motion throughout the length of the supply ,,
line, whereas in the structure of the prior art the separation
of the part of the carrier gas from the mainstream flow takes
place within the curving portion of the supply line offering a
significant local resistance to the flow, whereby a substantial
amount of kinetic energy is lost by the fine particles.
Moreover, in every embodiment of the disclosed tuyere
the withdrawn part of the carrier gas would not interact in
the molten metal with the mainstream flow.
The invention will be further described in connection
with embodiments thereof, with reference being made to the
accompanying drawings, wherein:
Fig. 1 schematically shows a tuyere with two annular
rows of openings for withdrawal of a part of
the carrier gas, and with the narrowing
terminal portion of the supply line,
Fig. 2 shows schematically a perspective, partly
broken-away view of a tuyere with annular
slits and a gas escape channel defined by a
specifically provided casing,
Fig. 3 shows schematically a tuyere with a slit for
withdrawing a part of the carrier gas, defined
as a gap between the end face of the terminal
portion of the supply line and the casing;
Fig. 4 shows schematically a tuyere with baffles in
the terminal portion thereof:
Fig. 5 is a sectional view taken on line V-V of
Fig. 4:
Fig. 6 shows a tuyere in accordance with Fig. 2 in
its operating position of treating molten metal
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in a steel-teeming ladle.
Referring now to the drawings, a tuyere or lance
for injecting powdered products into molten metal includes a
supply line 1 (Fig. 1) having at one end thereof a connection
(not shown) for communicating the tuyere with a line leading
from a pneumatic conveying unit supplying powdered products
in a flow of a carrier gas into the molten metal, e.g.
supplying desulfurizing agents in a flow of compressed air.
The terminal portion of the supply line 1 adapted to contact
the molten metal is provided with a series of openings 2
which in the embodiment being described serve essentially as
gas escape channel 3 through which a part of the carrier gas
is drawn away from the mainstream flowing through the tuyere.
Owing to this part of the carrier gas having been drawn away,
the concentration of the powdered product in the mainstream
flow is stepped up in the supply line 1 downstream of the
openings 2.
In the embodiment illustrated in Fig. 1 there are
two annular rows of the openings 2 in the supply line 1.
However, it should be understood that a different arrangement
of the openings would not alter the essence of the invention.
The terminal or end portion of the supply line 1 is
shaped as a truncated cone 4 narrowing down toward the outlet.
This provides for an increased velocity of the mainstream flow
issuing from the tuyere, and. hence, for deeper penetration
into the molten metal of the flow of the powdered product
entrained in the carrier gas. '-
In another embodiment, the openings 2 (Fig. 2) in
the supply line 1 are in the form of several substantially
annular slits- The slits-like shape of the openings 2 offers
the advantage of minimizing the amount of fine particles of the
powdered product carried away by the carrier gas withdrawn from
the mainstream flow.
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1~51421
In this embodiment there is a casing 5 mounted
externally of the supply line 1, coaxially therewith, to
define with this supply line 1 an annular gap 6 through which
the part of the carrier gas, withdrawn from the mainstream
flow, is led away. This construction enables to draw away
the part of the carrier gas along this annular gap or channel
6, to avoid its interaction with the molten metal, which in
a number of practical applications, e.g. in the case of
treating molten metal in a ladle, is essential from the point
of view of minimizing molten blowouts, of using inexpensive
compressed air as the carrier gas and of stepping up the
efficiency of utilizing some of the powdered product, e.g.
deoxidizing and desulfurizing agents, etc.
In another embodiment, likewise incorporating the
casing 5 (Fig. 3), the opening 2 for drawing away a part of
the carrier gas is defined by an annular gap (being in this
embodiment the gas escape channel 3) between the end face of
the supply line 1 and the internal wall of the narrowing
terminal portion 7 of the casing 5, ending in an outlet 8
coaxial with the supply pipe 1.
Alternatively, the terminal portion of the supply line
1 can be arranged as illustrated in Figs. 4 and 5, with its
cross-section altering from circular in the area of the inlets
of the gas escape channels to slit-like at the outlet (see
Fig. 5). Thus, the terminal portion of the tuyere is divided
by baffles 9 into the central channel through which the main-
stream flcw with the high concentration of the powdered product
is adapted to flow, and side channels for drawing away a part
of the carrier gas. The central channel is a continuation of
the supply line 1. The baffles 9 have their thickness increasing
toward the outlets of the gas escape channels. It should be
pointed out that the provision of the tuyere either with water
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cooling means, or with refractory heat protection means, or
with both would not alter the essence of the invention.
The disclosed tuyere illustratedin Fig. 2 is
operated in the following manner for treating molten steel in
a ladle with powdered desulfurizing compositions (e~g. lime
and fluorspar) supplied in a stream of compressed air ~see
Fig. 6), a displacement mechanism (not shown) is operated to
position the tuyere approximately 0.5 m above the molten metal
level, the supply of compressed air from the compressor into
the supply line 1 is turned on, the tuyere is dipped into the
molten metal to a 1.5 m, depth and the feed of the powdered
desulfurizing composition from the pneumatic conveying unit is
initiated. Thus, the powdered composition in the flow of the
carrier gas, i.e. compressed air, is fed into the supply line 1
of the tuyere, with part of the compressed air advancing through
the supply line 1 being drawn away through the slit-like open-
ings 2, into the gas escape channel 3 adjoining these openings 2,
to flow through the gap 6 defined between the supply line 1 and
the casing 5 into the atmosphere above the molten metal level, to
be collected therefrom by a hood (not shown) positioned above the
ladle and to be directed into a system cleaning the air from sus-
pended fine particles.
While the part of the carrier gas is led away through
the openings 2, the fine particles continue their motion by the
kinetic energy stored through the supply line 1 in the stream
of compressed air, to penetrate the molten metal at a higher
concentration than at the inlet of the tuyere.
With the feed of the powdered product terminated,
the supply line 1 is blasted with compressed air, the tuyere
is withdrawn from the molten metal, and the feed of com-
pressed air to the tuyere is turned off.
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The employment of the herein disclosed tuyere orlance, e.g. for treating molten steel in a ladle, enables:
- to step up the efficiency of utilization of powdered
products injected into molten metal with the aims of desulfuriza-
tion, deoxidation, alloying and carbonization,
- to cut down the production cost of steel,
- to reduce the percentage of fine particles carried
away from molten metal by the carrier gas'
- to minimize blowouts of molten metal from a ladle
in the course of the blasting, and to conduct the treatment
in a ladle being filled with steel teemed from a steel-making
unit.
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