Note: Descriptions are shown in the official language in which they were submitted.
1~3~42
This invention relates to a process and
system for a controlled supply of a shielding fluid
to a plurality of annular nozzles, which are mounted
in the refractory lining of a refining vessel. Each
of said annular nozzles defines an inner passage for
a refining gas and an annular shielding fluid passage
surrounding said inner passase. The inner passages of
said nozzles are connected by respective refining gas
feed conduits to a refining gas manifold. The annular
0 passsges of said nozzles are connected by respective
shielding fluid feed conduits to a shielding fluid
manifold. The pressure in the shielding fluid feed
conduits i8 controlled in dependence on the pressure
in the refining gas manifold.
~ hen ferrous metal is refined by means of
oxygen, ~hich i9 blown into the molten metal through
nozzles mounted in the refractory lining of the re-
fining vessel, an overheating of the outlet end of
the nozzle and the surrounding refractory must be~ ~ -
Zo prevented in that a shielding fluid i~ gaseous or -;
liquid form is injected at the same time. For this
purpose~ annular nozzles are provided, ~hich extend
through the refractory lining and define an inner
refining gas passage and an annular shielding fluid
passage surrounding the refininy gas passage. In such
a nozzle, the refining gas emerging from the inner
refining gas passage may undesirably enter the annular
passage for the shielding fluid or the shielding fluid
emerging from the annular passage may undesirably enter
30 the inner refining gas passage. A disturbing fire may be
f ~
~i34142
ignited in such case if the refining gas consists
of pure oxygen and the shielding fluid is combustible
and consists e.g., of propane OI' oil. For this reason
the ratios of the pressures and ~low rates of the
refining gas and shielding fluid supplied to each
nozzle should be so controlled that the nozzles will
not be clogged by accretion and will not be wear
at an excessively high rate.
It has already been proposed (German Patent
0 Specification 2,326,754) to control the supply of the
shielding fluid to each annular nozzle in dependence
on the supply of refining gas in that the flow in
each of the branch conduits which connect the shielding
fluid manifold to respective annular nozzles is
controlled by a control valve, which is adjusted in
dependence on the pressure in the refining gas manifold
so that the pressure of the 6hielding fluid cannot
undesirably rise above the refining gas pressure and,
as a result, the shielding fluid cannot enter the re-
zO fining gag passage of an annular nozzle. On the otherhand, an ingress of refining gas into the annular
passage for the shielding fluid can only be prevented
if the pressure in the shielding fluid manifold i6 50
high that the shielding fluid will be under a
sufficiently high pressure in the shielding fluid
passage when the control valve is opened. ~hereas such
a pre~sure control arrangement can prevent a flow of
refining gas and shielding fluid into the respective
other pa~age, it will not ensure a uni~orm distribution
30 of the refinlng gaa and of the shielding Fluid to the
- 2 -
~3414Z
annular nozzles. To ensure a low wear and a trouble- ~-
free operation, the shielding fluid should ~e uni-
formly distributed so that the desired ratio of
the refining gas and shielding fluid flow rates can
be ensured at all nozzles.
It i5 an ohject of the invention so to
improve a process of the kind described first herein-
before that a uniform distribution of the refining
gas and of the shielding fluid to the several annular
10 nozzles can be ensured.
This ohject is acco~plished according to
the invention in that the flow rate in each shielding
fluid feed conduit is controlled in dependence on the
flow rate in the refining gas manifold and~he pressure
in each shielding fluid feed conduit is kept below an
upper limit, which depends on the pressure in the re-
fining gas manifold.
It i9 apparent, that the flow in each
shielding fluid feed conduit rather than the pressure
20 is primarily controlled so that a desired ratio of
the flow rates of refining gas and shielding fluid
can be maintained For each annular nozzle and it is
ensured that the shielding fluid will produce the
optimum nhielding and cooling effects. But a mere flo~
rate control cannot prevent the pressure of the
shielding fluid to rise to such a high value that
the shielding fluid emerging from an annular nozzle
can enter the refining gas passage of the same nozzle.
For this reason the ~low rate control is combined with
30 an overriding pressure control, whlch prevents the
-- 3 --
: `
~3~142
pressure in eaGh shielding fluid feed conduit
Fram rising above an upper limit, which depends
on the instantaneDus refining gas pre~sure. In the
process according to the invention, the pressure
control serves merely to keep the pressure in the
shielding fluid feed conduits leading to respective
annular nozzles at values which are safe in relation
to the refining gas pressure so that the flow rate
control can be fully effective when the shielding
10 gas pressure is below its highest permissible value.
The conditions which ensùre a uniform distribution ~ -
of the refining gas and of the shielding fluid to
the several annular nozzles can thus be maintained ~-
with simple means.
The control of the flow rate of the shielding
fluid supplied to each annular nozzle in combination
with an overriding pressure control can be effected
in various waysc For instance, the flow in each ~ -
shielding fluid feed con~uit may be controlled by
Zo two control valves, which are connected in series,
and one o~ these control valves may be actuated by
a suitable pressure controller and the other by a
~low rate controller. But in such an arrangement,
an adjustment of one control valve will result in
an ad~ustment of the other control valve because
the pressure and the flow rate cannot be changed in-
dependently of each other. For this reason it will be
more desirable to control the flow in each shielding
fluid ~eed conduit by a single control valve, which
30 i9 sd~u~table by a control device, which comprises a
~ _
^~
~34'1~2
flow rate controller and a pressure controller. The
flow rate controller has q reference input connected
to a flow rate sensor for sensing the flow rate in
the refining gas manifold and another input connected
to a flow rate sensor for sensing the flow rate in
the shielding 989 feed conduit. The pressure controller
has a reference input connected to a pressure sensor
for sensing the pressure in the refining gas manifold
and another input connected to à pressure sensor for
0 sensing the pressure in the shielding fluid feed
conduit. The pressure control controller and the Flow ~;~
rate control controller are connected to the actuator
for the con~rol valve through a minimum-selecting ~-
.. ..
compar~tor.
In such an arrangement it i9 ensured in
a simple manner that the control valves far con~rolling
the flow in the shielding fluid feed conduits leading
to the respective annular nozzles are adjusted by the -~
pressùre controller w~e~ the pressure of the shielding
Zo fluid exceeds the reference value and by the flow
rate controller when the pressure of the shielding ;
fluid is below the reference value. The comparator
i9 connected to the flow rate controller and to the
pressure controller and ascertains which of the control
51gnal~ delivered by the9e controllers corresponds to
a ~maller flow area of the control valve, and the
comparator passes only that control signal to the
actuator for the control valve 90 that the latter is
correspondingly adjuste~. The oth~r control signal,
which corresponds to a larger flow area, is blocked
- 5 -
~L~3~1~2
by the comparator~ When the shielding gas pressure
is less than the highest permissible pressure, the
supply of the shielding fluid to each annular
nozzle will be controlled by the associated flo~
rate controller. On the other hand, the control
valve will be controlled by the pressure controller
as soon as the pressure of the shielding gas reaches
the reference value indicating the highest permissible
pressure. The comparator connected to both controllers ~ -
10 of the control system thus selects the control signal
correspon~ing to the smaller flow area. ~- ;
aecause the flow rate of the refining gas
in the refining gas manifold is proportional to the
flow rate of the refining gas in each of the re-
fining gas feed conduits leading to the respective
nozzles, as the resistance to the flow of the refining
gas adjacent to the annular nozzle varies hardly~and
differ5 in this respect from the resistance to the
~low of the shielding fluid, the flow rate in the
Z shielding fluid feed conduits leading to the several
annular nozzles i9 controlled in dependence on the
flow rate of the refining gas in the refining gas
manifold~ A desired ratio of the flow rates in the
re~ining gas and shielding fluid feed conduits can
be maintained in a simple manner in that the flow
rate sensor in the refining gas manifold is connected
to the flow rate controller by a preFerably adjust~
able scaling circuit. ~y means of that scaling
circuit, the signal representing the flow rate in
the reflniny ga~ manifold can be proportionally re-
- 6 -
~ ~134142
duced to represent theflo~ rate in each of the
refining gas feed conduits leading to respective
annular nozzles. The ratio of the flow rate in
the refining gas manifold and in each refining
gas feed conduit may change, e.g., when a nozzle
has failed and this change can be taken into
account by an adjustment of the scaling circuit.
Similar means may be used to convert
the signal representing the pressure in the refining
10 gas manifold to a signal representing the pressure ~ -~
in each refining gas feed conduit. To this end,
the pressure sensor in the refining gas manifold
i8 connected to the pres9ure controller by a
preferably adjustable scaling circuit.
A system according to the invention is
shown by way of example on the drawingg, in which ;;
Figure 1 is a simplified olock circuit
diagram showing a gystem according to the invention ^
for a controlled supply of 8 shielding fluid to a -`~
Z plurality of annular nozzles mounted in the re- ~;
fractory lining of a refining vessel and
Figure 2 is a block circuit diagram
showing the basic arrangement of the control system
for one o~ the annular nozzles~
Annular nozzles Z are mounted in the
refractory lining 1 of a refining vessel and consist
each of t~o concentric tubes, which define an inner
refining gas passage 3 and an annular shielding
fluid passage ~, which surrounds the refining gas
3 passage 3. A refining gas consisting, e.g., of oxygen
' . . . . ' ' . ~ ' .
- . . .
34142
is supplied to the refining gas passage 3 of each
annular nozzle Z by one of several feed conduits
6, which are connected to a refining gas manifold 5.
A shie~ding fluid is supplied to the annular passage
4 of each annular nozzle 2 by Dne of several feeo
conduits 8, which are connected to a shielding fluid
manifold 7. To ensure a unifDrm distribution of the
shielding fluidt~o all annular nozzles 2 in dependence
on the refining gas pressure, the flow rate and
10 pressure of the shielding fluid supplied to each
annular nozzle Z are controlled by a control valve 9
connected between the shielding fluid mani~old 7
and the respective feed conduit 8. For this purpose, ~ :
each control valve 9 is actuated by a separate control
device 10, which receives a flow rate reference sig- ;
nal from a flow rate sensor 11 for sensing the flo~
rate in the refining gas manifold 5 and a pressure
reference signal fro~ a pressure sensor 12 for
sensing the pressure in the refining gas ~anifold 5. :
In the control device 10, these reference signals
are compared with signals representing the actual
flow rate and the actual pressure in the associated
ehielding gas feed cond4it 8 and delivered by a flow
rate eeneor 13 and a pressure sensor 14, which are
arranged in the as~ociated feed conduit 8. The control
devlce 10 comprises means for deciding whether the
a~sociated control valve 9 is to be controlled in
dependence on the flow rate or the pressure in the
associated shielding fluid feed conduit 8. A control
in dependence on pressure will not be effected unless
- 8 _
.
1~L3414Z
the pressure detected hy the pressure sensor 1~
has risen to a value which has a certain ratio to
the refining gas pressure sensed by the pressure
sensor 12 in the manifold 5 and a further pressure
rise in the feed conduit 8 might cause shielding
fluid from the annular passage 4 to enter the re-
fining gas passage 3. The pressure sensor 1Z
determines an upper limit for the pressure in the
shieldin9 fluid feed conduits 8. As soon as the
10 pressure in a given feed conduit 8 exceeds that
upper limit, the control device 10 will cause the
respective control valve 9 to be actuated in a
closing sense. When the pressure in a given
shielding fluid feed conduit B is below the upper
limit, the flow rate control will be fully effective
and each control valve 9 will then be controlled to
maintain a predetermined ratio between the flow
rates of refining gas and shielding fluid discharged
by each annular nozzle 2. This will ensure that the
wear of the annular nozzles 2 and of the surrounding
re~ractory 1 will be slight and uniform.
The refining gas floLJ rate may be controlled
by a suitable controller 15, which actuates a control
valve 16 incorporal;ed in the refining gas manifold
anrl tn wi-lich a rlow rate signal is delivered by a
flow rate sensor 11. Similarly, the rlow rate oF the
6hielding fluid in the manifold 7 can be additionally
controlled so th~t the operation of the plant can oe
continued even when the control devices 10 have
~o Failed~ [n sucil case7 the control valves 9 associaled
-- '3 --
,~
~34142
with the feed conduits ~ must be adju~ted by hano.
For a simple combination of a flow rate
control and an overriding pressure cantrol t the
Control device 10 shown in Figure Z comprises a
flow rate controller 17 and a pressure controller 1~
The flow rate controller 17 is supplied at a reference
input with the output signals of the flow rate
sensor 11 and at another input with the output signal
of the flow rate sensor 13. The pressure controller
18 is supplied at a referenGe input with the output
signal of the pressure sensor 12 and at another in-
put with the output signal of the pressure sensor 14.
~ecause during undisturbed operation the flow rate
and pressure adjacent to the annular nozzles Z ~re
in a predetermined relation to the rate and pre~sure ;
in the respective manifold, the reference signals
supplied to the flow rate controller and pressure
controller, respectively, must be scaled down
cDrrespondingly. For this purpose, a scaling circuit
19 is connected between the flow rate sensor 11
and the flow rate controller 17 and a scaling
circuit 20 is connected between the pressure sensor
12 and the presr~ure contro~er 1B.
The control signals delivered by the
controllers 17 and 1~ are applied to a minimum-
selecting comparator circuit 21, which transmits
to the actuator 22 for the control valve only that
~ntrol signal which corresponds to a smaller flow
area nf the control valve 9 than the other control
ign.llO The control signal which corresponds to a
- 10 -
~34142
laryer flow area is blocked by the comparatorcircuit 21. In this way, the desired combined flow
rate and pregsure control is e~fected. When the
pressure which i9 represented by the signal that
is delivered by the pressure sensor 1Z via the
scaling circuit ZO to the presgure controller 1
exceeds the pressure sensed by the pressure sensor
14~ the pressure controller 18 tends to actuate the
control valve 9 in an opening sense so that the
10 flow rate control by the flow rate controller 17
can be fully effective until the flow rate control
tends to open the control valve 9 to such an extent
that the pressure in the feed conduit ~ exceeds the
reference pressure. In that case, as has been
explained hereinbefore, the control valve 9 will
not be opened further because the comparator circuit
21 then blocks the control signal delivered by the
flow ratè controller 17 and transmits only the
control signal delivered oy the pressure controlIer.
zO aecause the pressure af the refining gas may exhibit ~;`
large ~luctuations~ a reference signal depending on
the actual refining gas pressure must be applied
to the pressure contro~er. -
- 11 -
, . . .
,
