U.S. patent number 3,747,335 [Application Number 05/096,348] was granted by the patent office on 1973-07-24 for method and apparatus for controlling a metallurgical furnace turbo compressor.
This patent grant is currently assigned to Brown-Boveri Sulzer Turbomachinery, Ltd.. Invention is credited to Rene Strub.
United States Patent |
3,747,335 |
Strub |
July 24, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS FOR CONTROLLING A METALLURGICAL FURNACE TURBO
COMPRESSOR
Abstract
The blade angle of the stator blades in the turbocompressor is
adjusted in order to control the amount of compressed air delivered
by the turbocompressor. The blade angle is adjusted in dependence
on the speed of the turbomachinery shaft and the amount of
compressed air delivered by the turbocompressor can be divided
between the compressed air line to the plant and a branch line to a
reduced pressure zone so as to prevent pumping of the
turbocompressor.
Inventors: |
Strub; Rene (Winterthur,
CH) |
Assignee: |
Brown-Boveri Sulzer Turbomachinery,
Ltd. (Zurich, CH)
|
Family
ID: |
4178869 |
Appl.
No.: |
05/096,348 |
Filed: |
December 9, 1970 |
Foreign Application Priority Data
Current U.S.
Class: |
60/773; 65/143;
266/197; 266/155; 415/17 |
Current CPC
Class: |
C21B
5/06 (20130101); F02C 6/10 (20130101); F04D
27/0246 (20130101); F02C 9/20 (20130101); C21B
9/12 (20130101); C21B 2100/64 (20170501) |
Current International
Class: |
F04D
27/02 (20060101); C21B 9/00 (20060101); C21B
9/12 (20060101); C21B 5/06 (20060101); F02C
6/00 (20060101); F02C 9/00 (20060101); F02C
9/20 (20060101); F02C 6/10 (20060101); F02c
009/14 () |
Field of
Search: |
;60/39.29,39.18B,39.18C,39.23,39.03 ;123/119CE ;415/17 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Olsen; Warren
Claims
What is claimed is:
1. An apparatus for controlling a metallurgical furnace plant
having at least one furnace, a compressed-air line connected to
said furnace to supply compressed air thereto, a turbine connected
to said furnace to receive combustion gas therefrom and a
turbocompressor drivingly connected to said turbine to be driven
thereby and connected to said compressed air line to deliver
compressed air thereto, said turbocompressor having an adjustable
blade system therein; said apparatus comprising a speed controller
connected to said turbocompressor to be driven thereby and to said
adjustable blade system for changing the blade angle of said system
to vary the efficiency of said turbocompressor while maintaining a
constant turbocompressor speed and to maintain a constant pressure
in said compressed-air line, said speed controller having a
predetermined speed set value and means for adjusting said speed
set value, said means being adjusted in dependence upon the
pressure in said compressed-air line as created therein by a
separately driven compressor.
2. An apparatus as set forth in claim 1 which further comprises a
supply line connected between said furnace and said turbine for
delivering the combustion gas to said turbine, a shut-off element
in said supply line for selectively closing off the flow of gas
through said supply line to said turbine, and a quick-acting
controller connected between said turbine and said element for
actuating said element to close off the flow of gas to said turbine
in response to a measurement of a predetermined speed of said
turbine.
3. An apparatus for controlling a furnace plant having at least one
furnace, a compressed-air line connected to said furnace to supply
compressed air thereto, a turbine connected to said furnace to
receive combustion gas therefrom and a turbocompressor drivingly
connected to said turbine to be driven thereby and connected to
said compressed air line to deliver compressed air thereto, said
turbocompressor having an adjustable blade system therein; said
apparatus comprising a speed controller connected to said
turbocompressor to be driven thereby and to said adjustable blade
system for changing the blade angle of said system to vary the
efficiency of said turbocompressor while maintaining a constant
turbocompressor speed and to maintain a constant pressure in said
compressed-air line, as created therein by a separately driven
compressor, a delivery line between said turbocompressor and said
compressed-air line, a branch line connected between said delivery
line and a reduced pressure zone, and a control system in said
branch line for controlling a flow of compressed air through said
branch line, said control system including means in said delivery
line for measuring the air delivery of said turbocompressor and for
actuating said control system in dependence on the measured air
delivery pressure falling below a preset value.
4. An apparatus as set forth in claim 3 wherein said speed
controller has a predetermined speed set value and which further
comprises means for adjusting said speed set value.
5. An apparatus as set forth in claim 4 wherein said means is
adjusted in dependence upon the pressure in said compressed-air
line.
6. An apparatus as set forth in claim 3 wherein said control system
includes a regulating valve in said branch line responsive to an
air quantity set value in said system for opening thereof, and
means responsive to the pressure in said delivery line for
adjusting said air quantity set value.
7. An apparatus as set forth in claim 3 which further comprises a
check value in said delivery line between said branch line and said
compressed-air line for preventing a back flow of air from said
compressed-air line to said branch line and said
turbocompressor.
8. In combination with a metallurgical furnace plant having at
least one furnace producing a flow of combustion gas, a
compressed-air line connected to said furnace to supply compressed
air thereto at a constant pressure, a turbine connected to said
furnace to receive the flow of combustion gas therefrom and to be
driven thereby, and a turbocompressor drivingly connected to said
turbine to be driven thereby and connected to said compressed air
line to deliver compressed air thereto at constant pressure, said
turbocompressor having an adjustable blade system therein; an
apparatus for controlling said plant comprising a speed controller
connected to said turbocompressor to be driven thereby and to said
adjustable blade system for changing the blade angle of said blade
system to vary the efficiency of said turbocompressor while
maintaining a constant turbocompressor speed to maintain a constant
air pressure in said compressed-air line, said speed controller
having a predetermined speed set value and means for adjusting said
speed set value, said means being connected to said compressed air
line for adjustment in dependence upon the pressure in said
compressed-air line as created therein by a separately driven
compressor.
9. A method of controlling a metallurgical furnace plant having at
least one furnace producing a flow of combustion gas, a
compressed-air line connected to said furnace to supply compressed
air thereto at a constant pressure, a turbine connected to said
furnace to receive combustion gas therefrom and to be driven
thereby and a turbocompressor drivingly connected to said turbine
to be driven thereby and connected to said compressed air line to
deliver compressed air thereto at a constant pressure, said
turbocompressor having an adjustable blade system therein; said
method including the steps of
setting a set-value for the speed of said turbocompressor in
dependence on the pressure in said compressed-air line said
pressure created therein by a separately driven compressor;
determining a difference between the speed of said turbocompressor
and said set-value; and
changing the blade angle of said blade system in response to
occurrence of a said difference to vary the efficiency of said
turbocompressor while maintaining a constant turbocompressor speed
and a constant pressure in said compressed-air line.
10. An apparatus as set forth in claim 2 which further comprises a
branch line connected to said supply line upstream of said shut-off
element and to a reduced pressure area, and a straight-through
valve in said branch line connected to said controller for
actuation thereby to open said branch line to a flow of gas in
response to the measurement of said predetermined speed of said
turbine.
11. An apparatus as set forth in claim 1 which further comprises a
check valve between said turbocompressor and said compressed-air
line for preventing a flow back of air from said line to said
turbocompressor.
Description
This invention relates to an apparatus for controlling a furnace
plant, and particularly, a furnace plant for the heat treatment of
metals.
Heretofore, furnace plants have been known in which compressed air
necessary to support combustion has been supplied over a
compressed-air line to a furnace in which combustion has taken
place at elevated pressure. These plants have usually exhausted the
combustion gases from the furnaces at elevated pressures to a
turbine which, in turn, has driven a turbocompressor delivering
compressed air to the compressed-air line. In order to control the
turbocompressor sections of these plants, it has been the usual
practice to act on the turbine input gas flow. Unfortunately, the
possibilities of adaptation of this kind of control to the special
features of the furnace have been limited because only some of the
gas can then be supplied to the turbine while the remainder must be
discharged elsewhere as a reserve supply for control purposes. As a
result, the available gases cannot be utilized economically
enough.
Accordingly, it is an object of this invention to economically
utilize the waste gas flow of a furnace plant.
It is another object of the invention to eliminate any need to act
on the turbine input gas flow in order to control a furnace
plant.
Briefly, the invention provides a furnace plant which has a
compressed-air supply line, a furnace receiving compressed air from
the supply line, a turbine for receiving the waste gas exhausted
from the furnace and a turbocompressor for delivering compressed
air to the supply line with a speed controller in the section of
the plant containing the turbine and turbocompressor. This speed
controller is used to adjust an adjustable stator blade system in
the turbocompressor while the flow of gas to the turbine is
unaffected. In this way, by shifting the control from the turbine
to the turbocompressor, it is possible for the turbine to receive
the entire waste gas output from the furnace substantially at all
times. Full use is thus made of the turbine output.
The speed control is also provided with a means for adjusting the
speed set value. This adjusting means can be adjusted, e.g. in
dependence upon the pressure in the compressed-air line. As a
result, the compressor operation can always be controlled so as to
deliver in optimum circumstances the quantity of air corresponding
to the available power.
In addition, the turbocompressor delivery line is connected to a
branch line which leads to a reduced-pressure zone. This branch
line includes a control system which is adjusted by a senser which
measures the air delivery of the turbocompressor. This metering
system serves to control a means for adjusting the air quantity set
value at which a regulating element in the branch line begins to
open.
The means for adjusting the air quantity set value is itself
adjusted by the pressure in the turbocompressor delivery line. This
prevents the turbocompressor from operating near its pumping limit.
When little air is being taken from the compressed-air line, the
quantity of air which prevents the compressor from starting to be
pumpted discharges through the branch line. Any return of air from
the compressed-air line to the compressor or into the branch line
is prevented by the provision of a check valve in the delivery
line, a feature which may be particularly useful when air has to be
bled through the branch line to prevent pumping of the
turbocompressor.
The turbine feed line also has a stop member which is closed under
the control of a quick-acting controller when the turbocompressor
reaches maximum permissible speed. This case might occur if the
turbocompressor should suddenly prove unable to absorb the power
from the turbine, the result of which might cause the
turbo-machinery to race. It is also recommended, in this case, that
a branch line which has a straight-through valve and which extends
to an area of reduced pressure be connected to the turbine feed
line at a place upstream of the straight-through member, and to
have the straight-through valve opened under the control of a
quick-acting controller when the turbocompressor reaches maximum
permissible speed.
These and other objects and advantages of the invention will become
more apparent from the following detailed description and appended
claims taken in conjunction with the accompanying drawings in
which:
FIG. 1 diagrammatically illustrates a view of a furnace plant
controlled in accordance with the invention, and
FIG. 2 is a PV diagram of the turbocompressor.
Referring to FIG. 1, a metallurgical or blast furnace 1 is supplied
through a supply line 2 with combustion-supporting air at elevated
pressure. The waste gases of combustion leave the blast furnace 1,
at a pressure which, although reduced by the pressure drop in the
blast furnace 1, is still considerable, through a line 3 and pass
to a gas turbine 4. The turbine 4 drives, via a coupling 5, a
turbocompressor 6 having at least one row or ring of rotatable
adjustable stator blades 7 (only one of which is shown). The
compressor 6 intakes air from atmosphere through a line 8 and
delivers compressed air through a delivery line 9 to a
compressed-air line 10 which in turn is connected to at least the
blast furnace air supply line 2. Other lines for supplying
combustion-supporting air to other furnace plants can also be
connected to the line 10. A separately driven compressor (not
shown) will also be needed, as a rule, to supply the line 10 with
the quantity of air which the turbocompressor 6 cannot supply. In
operation, therefore, it is essential to maintain a constant
pressure, e.g. the pressure P1, in the compressed-air line 10 by
appropriate control of the quantity of air delivered by the added
compressor.
In order to control the operation of the turbocompressor 6, a speed
controller 11 driven by the turbomachinery shaft acts through the
agency of a servomotor 12 on the ring of adjustable blades 7 so
that the compressor efficiency decreases as speed decreases and
increases as speed increases. Through the agency of a set-value
adjustment system 13, as is known, the required set value of the
turbomachine can be determined in accordance with the pressure P1
in the line 10. However, since the pressure therein is maintained
constant, the speed too remains constant unless the pressure in the
line 10 changes.
In order to prevent pumping of the turbocompressor 6, a branch line
14 comprising a regulator valve 15 is connected to the
turbocompressor delivery line 9. The line 14 extends to an area at
a reduced pressure, such as a discharge line through which air
delivered in excess can discharge to atmosphere above the roof (not
shown) of the plant. The regulator valve 15 is actuated by a
servomotor 16 which is controlled by a senser 17 of conventional
structure which, in turn, is controlled by the quantity of air
flowing through line 9 to line 10. The regulator valve 15 starts to
open when the quantity of air entering line 10 becomes so small
that the turbocompressor 6 is near the critical level at which
pumping begins. The resulting increase in air delivery from the
turbocompressor 6 precludes any pumping thereof as the
turbocompressor 6 acts only against a small pressure. Since the
critical level for pumping also changes when the delivery pressure
is low, a senser 18 responsive to the pressure in the delivery line
9 adjusts the air quantity set value at which the servomotor 16
opens the valve 15. Consequently, whatever the operating condition
may be, as much compressed air can always be supplied to the line
10 as the same can absorb without any pressure increase, and air
need be discharged only in the amount necessary to prevent pumping
of the compressor. A check valve 25 in line 9 prevents a flowback
of air from line 10 to compressor 6 or to line 14 in such
cases.
In order to prevent the turbomachinery from racing under an excess
flow of waste gas, a quick-acting shut-off element 19 under the
control of a quick-acting shut-off controller 20 is interposed in
the line 3. If speed becomes excessive, the element 19 closes to
prevent the turbomachinery from racing. Also, a branch line
comprising a straight-through valve 22 is connected to the line 3
upstream of the element 19. The valve 22 is also controlled by the
controller 20 as is known, so that upon closure of the element 19,
the blast furnace waste gas passes through the line 21 to a
lower-pressure area. This feature ensures that a rapid shutdown of
the turbomachinery does not disturb the blast furnace
operation.
The compressor 6 shown is an axial-flow machine wherein either the
inlet stator blades, e.g., a ring preceding the first stage or
inter-stage rings or a final ring after the final stage can be
adjusted. If required, however, radial-flow compressors can be
used, in which event appropriate inlet turbulence devices or
turbulence devices in the diffusers are used. In special cases, it
might be possible for rotor rings of axial-flow compressors to be
adjustable.
The nature of the control provided can be gathered from the PV
diagram shown in FIG. 2. P1 denotes the delivery pressure in the
line 10 in FIG. 1. A denotes the pumping limit for various
operating conditions, and B denotes a level which the compressor
must not pass through if pumping is not to occur. Curves W1, W2 and
W3 represent zones of equal efficiency (86, 84 and 80 percent).
The normal operating condition is at point F on the line P1, the
compressor having a particular performance N at a speed R. The
adjustable blades 7 are at a blade angle B. When the turbine output
decreases, e.g. because either the quantity of gas or the pressure
or the temperature decreases, the operating point shifts from point
F to point F', the blade angle B changing. The control adjusts the
blade, for instance, to the blade angle B' at the point F'. If
there still is a tendency to shift towards the critical pumping
level A, the metering control system 15, 16, 17 then opens the
regulator valve 15 so that air can discharge through the line 14
and the total delivery of the compressor 6 increases, operation
shifting back towards the point F' so that the pumping zone above
the curve A is not reached.
When the output from the turbine to the turbocompressor increases,
operation shifts from the point F towards the point F". The control
then acts to adjust the adjustable blades to the blade angle B".
More air is therefore supplied to the line 10 and so the work done
by the turbine is absorbed. If the turbine output were to increase
further, compression would be controlled out and operation would
follow the curve B". The turbocompressor would then deliver a
smaller volume of air but at high pressure and thus absorb the
increased turbine output, although at increased speed.
Speed could become excessive only in exceptional circumstances in
which the compressor ceased to be able to absorb the power supplied
thereto. In such cases, the quick-acting controller 20 would
operate and in all cases close the quick-acting element 19, and, if
required, open the discharge valve 22 so that the turbine plant
would stop.
Since waste gases from blast furnaces usually contain appreciable
proportions of finely divided impurities, with the consequent risk
of deposits being formed in lines and difficult bends,
accumulations of this kind may build up in quite a short period of
operation to such an extent that the flow cross-sections are
reduced to a disturbing extent and any moving parts present may
jam. The places most at risk are tube elbows and, in particular,
control equipment, such as the turbine control valves. However, at
the high flow velocities in the turbine, the blade shaping
according to the invention so directs the flow that either
accumulations are completely obviated or small accumulations are at
least prevented from getting any bigger. The invention thus allows
the placement of the all important control equipment elsewhere than
in the turbine gas flow so that the turbine can operate without
disturbance despite the high dust contents of the turbine-operating
gas.
* * * * *