U.S. patent number 3,582,050 [Application Number 04/763,256] was granted by the patent office on 1971-06-01 for fluid-handling, gas-scrubbing, and blast furnace top pressure control.
This patent grant is currently assigned to National Steel Corporation. Invention is credited to Hiram C. Kozak.
United States Patent |
3,582,050 |
Kozak |
June 1, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
FLUID-HANDLING, GAS-SCRUBBING, AND BLAST FURNACE TOP PRESSURE
CONTROL
Abstract
Venturi-scrubbing system for blast furnace effluent gases,
embodies a fluid handling system in which pressure of fluid
(including the effluent gases) flowing in a passageway in open
communication with the blast furnace top, is controlled by
injecting control fluid into the passageway to increase and
decrease the effective transverse cross-sectional area of the
passageway at the location of control fluid injection. The control
fluid is injected at the throat of the venturi in response to
sensed pressure in the passageway, to adjust the effective
cross-sectional area of the throat to maintain a predetermined
pressure drop across the venturi, or a predetermined pressure
upstream or downstream of the venturi. By controlling pressure in
the passageway, the blast furnace top pressure is controlled.
Inventors: |
Kozak; Hiram C. (Lackawanna,
NY) |
Assignee: |
National Steel Corporation
(N/A)
|
Family
ID: |
25067307 |
Appl.
No.: |
04/763,256 |
Filed: |
September 27, 1968 |
Current U.S.
Class: |
261/36.1;
261/118; 137/13; 137/805; 137/806; 137/842; 261/DIG.54 |
Current CPC
Class: |
B01D
47/10 (20130101); Y10S 261/54 (20130101); Y10T
137/0391 (20150401); Y10T 137/2071 (20150401); Y10T
137/2273 (20150401); Y10T 137/2076 (20150401) |
Current International
Class: |
B01D
47/00 (20060101); B01D 47/10 (20060101); B01f
003/04 () |
Field of
Search: |
;261/DIG 54/
;261/118,36.1 ;137/13,81.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miles; Tim R.
Claims
I claim:
1. Fluid handling apparatus, comprising
means including walls defining a passageway having an effective
cross-sectional area for flow of first fluid,
the walls of the passageway being immovable relative to one
another,
sensing means for sensing pressure of first fluid flowing in the
passageway,
means including an injector located along the passageway for
injecting second fluid into the passageway to decrease and increase
the effective cross-sectional area of the passageway at the
location of second fluid injection,
the injector including directing means for directing second fluid
into the passageway in a direction transverse to the passageway,
and
control means responsive to the sensing means for increasing and
decreasing pressure of second fluid to decrease and increase the
effective cross-sectional area of the passageway, to maintain a
predetermined pressure condition of first fluid flowing in the
passageway,
the passageway including a venturi portion having a contraction
section, a throat section, and an expansion section defined by
portions of the passageway walls,
the injector being located at the venturi portion of the
passageway,
the directing means including means defining a plurality of
injector apertures in the walls of the passageway in the throat
section of the venturi portion,
the throat section having a fixed cross-sectional area defining a
maximum value for the effective cross-sectional area of the
passageway in the throat section,
the fixed cross-sectional area of the throat section having a major
axis and a generally elliptical configuration,
the injector apertures being positioned around opposed major axis
end portions of the throat section,
the walls of the passageway including opposed, imperforate portions
between the major axis end portions of the throat section.
2. Gas-scrubbing apparatus, comprising
means including walls defining a passageway having a venturi
portion and having an effective cross-sectional area for flow of
first fluid including gas,
means for injecting scrubbing liquid into the passageway at a
location upstream of the venturi portion,
the passageway walls at the venturi portion including means for
accelerating the first fluid to disperse injected scrubbing liquid
into fine particles,
the venturi portion being characterized by absence of movable
walls,
sensing means for sensing the pressure of the first fluid flowing
in the passageway,
means including an injector located at the venturi portion for
injecting second fluid into the passageway to decrease and increase
the effective cross-sectional area of the passageway at the venturi
portion,
the injector including directing means for directing the second
fluid into the passageway in a direction transverse to the
passageway to form a flow-retarding barrier, and
control means responsive to the sensing means for increasing and
decreasing the pressure of the second fluid to decrease and
increase the effective cross-sectional area of the passageway to
maintain a predetermined pressure condition of the first fluid
flowing in the passageway,
the flow-retarding barrier advancing away from and withdrawing
toward the walls of the passageway with the increasing and
decreasing pressure of the second fluid.
3. The apparatus of claim 2,
the means for injecting second fluid into the passageway to
decrease and increase the effective cross-sectional area of the
passageway including
a supply conduit in fluid communication with the injector,
the control means including
a pressure regulator in the supply conduit, and
controller means responsive to the sensing means for operating the
pressure regulator to increase and decrease pressure in the supply
conduit downstream of the pressure regulator.
4. The apparatus of claim 2,
the venturi portion having a contraction section, a throat section,
and an expansion section,
the injector being located at the throat section of the venturi
portion.
5. The apparatus of claim 4,
the sensing means including a first pressure sensor located
upstream of the throat section of the venturi portion and a second
pressure sensor located downstream of the throat section of the
venturi portion,
the control means increasing and decreasing the pressure of second
fluid to maintain a predetermined pressure differential in the
passageway across the venturi portion.
6. The apparatus of claim 4,
the sensing means including a pressure sensor located upstream of
the throat section of the venturi portion,
the control means increasing and decreasing the pressure of second
fluid to maintain a predetermined pressure in the passageway
upstream of the venturi portion.
7. The apparatus of claim 4,
the sensing means including a pressure sensor located downstream of
the throat section of the venturi portion,
the control means increasing and decreasing the pressure of second
fluid to maintain a predetermined pressure in the passageway
downstream of the venturi portion.
8. The apparatus of claim 4,
the directing means including means defining a plurality of
injection apertures in the walls of the passageway in the throat
section of the venturi portion.
9. The apparatus of claim 8,
the throat section having a central axis,
the injection apertures directing second fluid toward the central
axis of the throat section.
10. Gas-scrubbing process, comprising
passing first fluid including gas through a passageway having walls
and having an effective cross-sectional area for flow of the first
fluid,
the passageway having a venturi portion characterized by absence of
movable walls,
injecting scrubbing liquid into the passageway at a location
upstream of the venturi portion,
accelerating the first fluid in the venturi portion, thereby
dispersing injected scrubbing liquid into fine particles,
sensing the pressure of the first fluid flowing in the
passageway,
injecting second fluid into the passageway at the venturi portion
in a direction transverse to the passageway, thereby forming a
flow-retarding barrier, and
automatically increasing and decreasing the pressure of the second
fluid in response to the sensed first fluid pressure to advance the
barrier away from and withdraw the barrier toward the walls of the
passageway, thereby decreasing and increasing the effective
cross-sectional area of the passageway to maintain a predetermined
pressure condition of the first fluid flowing in the
passageway.
11. The process of claim 10,
the venturi portion having a contraction section, a throat section
and an expansion section,
the second fluid being injected into the throat section of the
venturi portion.
12. The process of claim 11,
the pressure of first fluid being sensed at a location upstream of
the throat section of the venturi portion and at a location
downstream of the throat section of the venturi portion,
the pressure of second fluid being increased and decreased to
maintain a predetermined pressure differential in the passageway
across the venturi portion.
13. The process of claim 11,
the pressure of first fluid being sensed at a location upstream of
the throat section of the venturi portion,
the pressure of second fluid being increased and decreased to
maintain a predetermined pressure in the passageway upstream of the
venturi portion.
14. The process of claim 11,
the pressure of first fluid being sensed at a location downstream
of the throat section of the venturi portion,
the pressure of second fluid being increased and decreased to
maintain a predetermined pressure in the passageway downstream of
the venturi portion.
15. Blast furnace top pressure control and gas-scrubbing process,
comprising
withdrawing first fluid including gas from a blast furnace top
region,
passing the withdrawn first fluid through a passageway in open
fluid communication with the blast furnace top region,
the passageway having walls and having an effective cross-sectional
area for flow of the first fluid,
the passageway having a venturi portion characterized by absence of
movable walls,
injecting scrubbing liquid into the passageway at a location
upstream of the venturi portion,
accelerating the first fluid in the venturi portion, thereby
dispersing injected scrubbing liquid into fine particles,
sensing the pressure of the first fluid flowing in the
passageway,
injecting second fluid into the passageway at the venturi portion
in a direction transverse to the passageway, thereby forming a
flow-retarding barrier, and
automatically increasing and decreasing the pressure of the second
fluid in response to the sensed first fluid pressure to advance the
barrier away from and withdraw the barrier toward the walls of the
passageway, thereby decreasing and increasing the effective
cross-sectional area of the passageway to maintain a predetermined
pressure condition of the first fluid flowing in the
passageway,
thereby maintaining a predetermined pressure in the blast furnace
top region.
Description
BACKGROUND OF THE INVENTION
This invention relates to fluid-handling systems. In its more
particular aspects, the invention pertains to systems for scrubbing
gases to remove entrained dust particles.
In operation of venturi scrubbers for dust-laden blast furnace
off-gases, the pressure of gases in the scrubbing system is
controlled as an expeditious technique for controlling the pressure
in the top of the furnace from which the off-gases are withdrawn.
For smooth furnace operation, it is desirable to maintain a
generally constant top pressure for a given set of operating
conditions. Without control, the top pressure fluctuates as a
result of changes in burden density and other factors.
To control the pressure of gases in a venturi-scrubbing system, it
has been proposed to provide the venturi with walls which are
movable to alter the cross-sectional area of the venturi.
Adjustment of the venturi area controls pressure in the system, but
movable-wall constructions of the prior art are disadvantageous in
that moving parts are necessarily exposed to the highly erosive
action of the dust-laden blast furnace gases. As a result of
erosion, prior art adjustable-area orifices provide constant
maintenance problems and have unacceptably short service lives.
Main objects of the invention are to provide improved and
simplified fluid-handling, gas-scrubbing and blast furnace top
pressure control systems, in which pressure can be effectively
controlled and the effective cross-sectional area of a venturi can
be adjusted without subjecting moving parts to erosive action of
fluids in the system.
Other objects of the invention will appear from the following
detailed description which, together with the accompanying
drawings, discloses a preferred embodiment of the invention for
purposes of illustration.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, similar reference characters denote similar
elements throughout the several views, and:
FIG. 1 schematically illustrates a venturi-scrubbing system
embodying principles of the invention;
FIG. 2 is a cross-sectional view of the venturi of the system of
FIG. 1; and
FIG. 3 is a cross-sectional view on line 3-3 of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, hot, dust-laden blast furnace effluent gases are
withdrawn from the top of an iron blast furnace 8, passed through a
conventional dust catcher (not shown) for removal of many of the
entrained dust particles, and then passed via conduit 10 through a
venturi-scrubbing system constructed and operated in accordance
with the invention. Water or other scrubbing liquid is sprayed from
pipe 12 into conduit 10 at location 14, in a conventional manner.
The blast furnace gases, with entrained scrubbing liquid, are
accelerated in a venturi (generally indicated at 16) downstream
from the locus of injection of washing liquid. Acceleration of
fluid in venturi 16 intimately contacts the dust-laden gases with
the scrubbing liquid by atomizing into fine particles the
relatively coarse spray particles of scrubbing liquid, so that the
gases are effectively cleaned of contaminants. The scrubbed gases
then pass into a conventional cooling tower 17 and upwardly through
the tower in countercurrent flow with cooling water to emerge clean
and cool through conduit 20.
As will be appreciated from FIGS. 2 and 3, the walls of conduit 10
define a fluid passageway 11 which is constricted at venturi 16.
The venturi includes a contraction section 18, a throat section 20,
and an expansion section 22, as is conventional.
A control fluid injector, generally indicated at 24, is located at
throat section 20. Injector 24 includes a plurality of injection
apertures 26 formed in the walls of throat 20. As discussed in
detail hereinafter, control fluid is injected into throat 20 to
control the pressure of fluid flowing in the passageway by
adjusting the effective transverse cross-sectional area of the
throat. Apertures 26 direct the control fluid into throat 20 in a
transversely inward direction relative to the passageway. Stated
differently, the control fluid is directed into the passageway from
the walls in the general direction of i.e., toward, longitudinal
axis 28 of the passageway.
Control fluid under pressure is supplied to apertures 26 from
headers 30, 32 which are located on opposite sides of throat 20.
Headers 30, 32 are supplied with control fluid through a plurality
of branches 34 of a control fluid supply conduit 36.
Throat 20 has a generally elliptical cross-sectional configuration
(FIG. 3), although other than elliptical configurations can be
employed. Since the walls of the conduit are fixed in position,
throat 20 has a fixed open cross-sectional area. Being elliptical,
throat 20 has major and minor axes 38, 40 respectively. Control
fluid injection apertures 26 are grouped around those opposed end
portions of the throat which lie at the ends of major axis 38.
Imperforate wall portions 42, 44 separate the groups of injection
apertures. For example, each of the opposed imperforate wall
portions 42, 44 can comprise about 20 percent of the throat
circumference.
At any given location along its length, the passageway defined by
the walls of conduit 10 has an effective cross-sectional area,
herein defined as that portion of the transverse cross-sectional
area of the passageway through which fluid can flow. The maximum
value for the effective cross-sectional area at any given location
is the open cross-sectional area of the conduit. The effective
cross-sectional area of the passageway is generally constant all
along the length of the passageway, except at venturi 16 where the
walls of the conduit converge and diverge. At all locations along
the passageway the effective cross-sectional area is fixed at the
maximum value defined by the open cross-sectional area of the
conduit, except in throat 20. In the throat, the cross-sectional
area available for fluid flow can be adjusted as desired by
adjusting the pressure under which control fluid is injected
through apertures 26. The effective cross-sectional area of the
throat, before any control fluid is injected, is that of the open
cross-sectional area defined by the walls of the throat. However,
after injection is initiated, the effective cross-sectional area of
the throat is decreased because of resistance to flow provided by
the injected control fluid. The extent to which the effective
cross-sectional area of the throat is decreased is proportional to
the pressure of injection of control fluid. With increasing control
jet pressure, throat 20 is progressively choked down, approaching a
generally circular configuration because of the location of
apertures 26 at the major axis end portions of the throat. The
process is reversible, with reduction in control jet pressure
increasing the effective orifice cross-sectional area so that the
orifice progressively approaches the size and shape of the area
defined by the fixed walls of the throat.
Control fluid supplied to injector 24 through conduit 36 is
pressurized by pump 46 (FIG. 1). Injector 24, conduit 36 and pump
46 are thus parts of a system by which control fluid is injected
into conduit 10 to decrease and increase the effective
cross-sectional area of the gas passageway at venturi 16. Control
fluid pressure is increased and decreased to decrease and increase
the effective cross-sectional area of the passageway at the venturi
to maintain a predetermined pressure condition of fluid flowing in
the passageway, by an automatic control system. The control system
includes pressure sensors 48, 50, which can be of any suitable type
of conventional design. For example, a Pneumatic Differential
Pressure Transmitter, Series 292, manufactured by Honeywell, Inc.
(Industrial Division), Fort Washington, Pa. (hereafter termed
"Honeywell"), can be employed. The pressure sensors sense pressure
of gases and other fluid in the passageway at locations upstream
and downstream, respectively, of venturi 16. The pressure sensors
transmit pressures in conduit 10 upstream and downstream of venturi
16 to controller 52, which can be of any suitable type of
conventional design. For example, a Honeywell Class 70 Pneumatic
Controller can be used. Controller 52 is operatively connected in a
conventional manner to a pressure regulating valve 54 and opens and
closes the valve to increase and decrease control fluid pressure in
conduit 36 downstream of the valve in response to the sensed
pressures. Valve 54 can be of any suitable, conventional type, and
as an example, can be a Honeywell Cage Type Flow Control Valve.
With pressure sensors 48, 50 transmitting pressures upstream and
downstream of venturi 16 to controller 52, the pressure
differential across the venturi is constantly monitored and can be
maintained at any desired predetermined value set on the
controller. For example, if it is desired to maintain a pressure
condition in the conduit in which there is a pressure drop of about
30 inches of water across the venturi, this value is set on
controller 52. When, because of variation in pressure of the input
gases or for any other reason, the pressure drop increases above
the desired value, controller 52 responds to the increase as sensed
by sensors 48, 50 by progressively closing valve 54 to
progressively decrease the control jet pressure, thereby
progressively increasing the effective cross-sectional area of
throat and progressively decreasing the pressure drop across the
venturi back toward the predetermined level. When the predetermined
level is attained the controller holds valve 54 in the position
then occupied, to maintain the present level.
Conversely, if the pressure drop across the venturi decreases below
that desired, controller 52 responds by opening valve 54 to
increase the control jet pressure, thereby choking down the
effective cross-sectional area of throat 20 and increasing the
pressure differential across the venturi back to the predetermined
value.
By controlling the pressure differential across venturi 16, the
back pressure (i.e., the pressure upstream of the venturi) and thus
the furnace top pressure is controlled, because conduit 10 is in
open fluid communication with the top region of the furnace. The
greater the pressure differential across the venturi, the higher
the furnace top pressure. Stated another way, the furnace top
pressure is proportional to the pressure drop across the venturi,
the exact proportion being determined for any given system by
conduit losses and other factors operative between the furnace and
the scrubber. Since the walls of throat 20 are fixed, no moving
parts are exposed to the erosive action of the dust-laden gases,
and effective furnace top pressure control can be exercised by
orifice-area control without the disadvantages of prior art
variable-area orifices.
By eliminating or otherwise deactivating downstream sensor 50,
setting controller 52 to respond only to upstream pressure sensor
48, control fluid pressure can be adjusted to maintain a pressure
condition in which the pressure upstream of venturi 16 is held at
any desired, predetermined value by adjustment of the effective
cross section of throat 20.
For example, if it is desired to maintain a gas pressure of about
90 inches of water in conduit 10 upstream of venturi 16, this value
is set on controller 52 and downstream sensor 50 is deactivated (as
by venting to atmosphere, in the case of a pneumatic sensor). When
upstream sensor 48 detects an increase in pressure above that
desired, controller 52 responds by closing valve 54, thereby
decreasing control jet pressure and increasing the effective
cross-sectional area of throat 20 so that gas pressure in conduit
10 upstream of the venturi decreases toward the desired level. If
the upstream pressure decreases below that desired, controller 52
responds to correct the condition by opening valve 54, thereby
increasing control jet pressure and decreasing the effective
cross-sectional area of the throat so that back pressure upstream
of the venturi increases toward the preset value. In this mode of
operation, as in the mode employing pressure-drop control, the
blast furnace top pressure is controlled by controlling pressure in
conduit 10, by virtue of the conduit being in open fluid
communication with the blast furnace top region and the top
pressure being proportional to the passageway pressure upstream of
the venturi.
By deactivating upstream pressure sensor 48 so that controller 52
responds only to the downstream sensor 50, control fluid pressure
can be adjusted to maintain a gas pressure condition in which
pressure downstream of venturi 16 is held at a predetermined
value.
For example, if it is desired to maintain a fluid pressure of about
50 inches of water in conduit 10 downstream of the venturi, this
pressure is set on controller 52 and upstream sensor 48 is
deactivated. When sensor 50 detects an increase in pressure above
the desired value, controller 52 responds by opening valve 54,
thereby increasing control jet pressure, decreasing the effective
cross-sectional area of the throat 20, and decreasing the
downstream pressure towards the preset level. Conversely, if the
downstream pressure decreases below the level set on controller 52,
the controller responds to the decrease as detected by sensor 50 by
closing valve 54, thereby decreasing control jet pressure,
increasing the effective cross section of throat 20, and increasing
the pressure downstream of the venturi back to the preset level.
Since the furnace top region is in open fluid communication with
conduit 10 and the furnace top pressure is proportional to the
pressure downstream of the venturi, this mode of operation also
controls the furnace top pressure.
The volume fluid can be water, clean gas, or any other suitable
material. The output of pump 46 is controlled to assure that supply
conduit 36 always contains sufficient control fluid volume and
pressure upstream of pressure regulating valve 54 to accommodate
any demand that may be required on opening valve 54, but without
developing an unduly high pressure head against the pump. This is
effected through a conventional pressure sensor 56 which detects
the pressure in supply conduit 36 upstream of valve 54 and
downstream of pump 46. This pressure is transmitted to controller
58, which can be of any suitable type of conventional design, and
is operatively connected to position valve 60. When back pressure
in conduit 36 exceeds a value necessary for proper operation of
injector 24, valve 60 is opened by controller 58 to bleed a portion
of the pump output from conduit 36 for recycle through conduit 62.
Thus, pressure in conduit 36 upstream of regulating valve 54 is
maintained at desired levels by recirculating as much or as little
of the pump output as is necessary to maintain the necessary
pressure in conduit 36 upstream of valve 54.
Fluid-handling systems embodying principles of the invention are
highly advantageous. With such systems, the effective
cross-sectional area of fluid passageways can be adjusted for
operation at maximum efficiency irrespective of input pressure by a
simple system employing no moving parts exposed to the fluid
stream. A predetermined pressure drop can be maintained across a
constricted orifice, or pressure above or below the orifice can be
established at a predetermined value. Control can be exercised over
blast furnace top pressure by pressure control in a venturi
scrubber without maintenance problems associated with prior art
movable-wall, adjustable-area orifices.
Although the invention has been described with reference to a
preferred embodiment, modifications of that embodiment can be made
without departure from the principles of the invention. Such
modifications are within the scope of the invention as defined by
the appended claims.
* * * * *