Information
-
Patent Grant
-
6178976
-
Patent Number
6,178,976
-
Date Filed
Monday, February 22, 199925 years ago
-
Date Issued
Tuesday, January 30, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Armstrong, Westerman, Hattori, McLeland & Naughton
-
CPC
-
US Classifications
Field of Search
US
- 134 64 R
- 134 122 R
- 134 182
- 134 201
- 134 82
- 134 64 P
- 134 122 P
- 454 67
-
International Classifications
-
Abstract
A tank cover made of a plurality of sections, which when connected, form a continuous tank cover enclosing the pickle tank. The tank cover is constructed of a plurality of exhaust sections each having an exhaust outlet and a plurality of sections having a plenum chamber which adjoin each other and the exhaust sections. The sections of the tank cover having the plenum chamber have an internal chamber for collecting evaporated acid fumes and transporting these fumes to exhaust outlets connected to the exhaust sections where the fumes may be discharged to an external scrubber.
Description
FIELD OF THE INVENTION
The present invention relates generally to a cover assembly for metal pickling tanks and more specifically to a cover assembly which has as a part thereof a means for collecting and exhausting toxic and corrosive fumes released from a picking line.
BACKGROUND OF THE INVENTION
Pickling is the process of chemically removing oxides and scale from the surface of a metal by the action of water solutions of inorganic acids. The reaction occurring when steel or iron materials are immersed in dilute inorganic acid solutions includes the solution of metal as a salt of the acid and the evolution of hydrogen. Steel pickled in dilute hydrochloric acid and sulfuric-acid solutions is an example of this reaction, with the end products of reaction being, respectively, ferrous chloride and hydrogen and ferrous sulfate and hydrogen. Adherent films of oxides are removed by the acid attack upon the scale on the base metal.
The pickling zone for pickling metal usually consists of several individual acid-proof tanks, typically about two to three feet in depth, located in series, comprising an effective immersion length of about 250 to 300 feet. While many lines have from three to five tanks, each about 40 to 80 feet long, some lines have only one long tank, divided by weirs into four or five sections. The strip is completely submerged under several inches of liquid acid bath as it travels through the tank or series of tanks forming the pickling zone.
The rate of pickling metal in the pickling zone is affected by numerous variables, including the metal-based constituents and the type and adherence of oxide to be removed. Solution temperature and concentration, ferrous chloride or ferrous sulfate concentration, agitation, time of immersion and presence of inhibitors all influence the rate of acid attack. Rate of acid attack and tank efficiency are important considerations when choosing operational parameters such as the choice of acid, hydrochloric acid or sulfuric acid for example, and the temperature of the acid bath. One of the most common efficiency problems in today's pickling systems is heat loss from the acid baths. The loss of heat lowers the efficiency of the overall system and will be more costly to operate.
Much of the heat supplied to the acid baths in pickling operations is lost at the surface of the acid bath by liquid evaporation. The heated acid bath solution evaporates into the air space between the acid bath and a cover enclosing the tank from the outside. In conventional pickling systems, the space above the acid bath and below the tank cover is used for transporting exhaust gases, evaporated acid bath fumes and air, to exhaust exits connected to the tank cover. Thus, the exhaust gasses in this space are not static, but form a fluid stream that typically flows in one direction, discharging through the exhaust exits. The contact of this fluid stream, traveling just above the acid bath surface, with the bath increases the evaporation rate at the air-liquid interface of the bath.
Increased evaporation leads to increased heat loss which means that more heat must be supplied to the acid baths in order to maintain the acid baths at a constant temperature. Maintaining the acid baths at a constant temperature is important in achieving even pickling of a length of metal product. By maintaining a specific acid temperature, the pickling process can either be sped up or slowed down to achieve the proper pickling of a product. But heat loss from the acid bath can complicate the pickling process by creating temperature gradients in the acid baths which can cause uneven pickling of the metal product.
In many present designs, the surface of the acid bath is open to the circulation exhaust gases from the pickling system. This facilitates heat loss. Because most of the heat loss of the acid is from the surface of the liquid in the form of evaporation, it is important to control this loss.
OBJECTS OF THE INVENTION
It is an object of the present invention to overcome the above disadvantages, and in particular to provide a pickle tank cover which minimizes heat loss and improves the efficiency of the pickling operation.
It is another object of the present invention to provide a cover assembly and fume collection system which is resistant to high temperature corrosive acid fumes.
It is yet another object of the present invention to provide fume removal at specific locations along the pickling tank for minimal heat loss of pickling acid bath.
It is still another object of the present invention to provide a tank cover that transports air and fumes so the moving air does not substantially contact the liquid surface of the acid bath of the pickling tank.
It is again another object of the present invention to capture escaping fumes at the inlet and exit openings of the pickling tanks where the metal strip enters and exits the pickle tanks and where the covers join.
It is a further object of the present invention to provide a fume exhaust system that is balanced.
It is still a further object of the present invention to provide an improved method for pickling a length of metal strip.
Finally, it is an object of the present invention to provide tank covers such that air is pulled from outside of the pickle tanks to form an air curtain around the entry and exit points to prevent fumes from escaping from the pickle tanks.
Other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The present invention is a tank cover for a pickling operation which can improve the efficiency of the metal pickling operation and can overcome the disadvantages of prior art tank covers. It can also reduce the costs of the pickling operation. Specifically, the tank cover of the present invention reduces the heat lost from the pickling system and minimizes escape gases from the system by improving the flow of air and exhaust gases through the pickling system.
To the end of minimizing heat loss and achieving efficiency, the tank cover of the present invention separates the surface of the acid baths in the pickle tanks from exhaust gas flow through the pickling system. This separation reduces the acid evaporation rate which reduces heat loss and provides for a more efficient control over the exhaust gases.
A typical tank cover of the present invention extends the length of the pickle tank from the metal strip inlet to metal strip outlet at the opposite end of the pickle tank. Preferably the tank cover is made of a plurality of sections, which when connected, form a continuous cover enclosing the pickle tank. Specifically, the tank cover is constructed of a plurality of exhaust sections each having an exhaust outlet which is stationary and a plurality of sections which are movable. The sections which are movable can be opened for access to the inside of the tank if required for maintenance. The plurality of sections which are movable have a plenum chamber, which adjoin each other and the exhaust sections. Furthermore, the tank cover of the present invention is preferably constructed so that the exhaust sections form the entrance and exit of the pickling system in addition to being spaced evenly along tank cover between the sections having the plenum chamber.
The sections of the tank cover having the plenum chamber have an internal plenum chamber for collecting evaporated acid fumes and transporting these fumes to exhaust outlets connected to the exhaust sections. The separate collection and transportation of exhaust gases in the plenum chamber does not disturb the air-liquid interface of the acid bath, thereby reducing the evaporation rate. Once exhaust fumes have entered the plenum chamber, the fumes are transported to the exhaust outlet sections along the pickle tank cover where they are sent to a scrubber. Air velocities may be increased in the plenum chamber without concern for heat loss of the fluid in the pickle tanks because the fumes are not in contact with the fluid surface in the tanks.
Not only does the tank cover of the present invention minimize heat loss from the pickling tanks but it minimizes escape gases from the system. Air flow ducts are attached to the tank cover of the present invention at the entrance and exit of the pickle tank to capture most escaping gasses. This is another way heat is conserved and the efficiency of the system is improved as compared to prior art systems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic view, in cross-section, of three pickle tanks aligned in series covered by one embodiment of a tank cover of the present invention;
FIG. 2
is a schematic view, in cross-section, of one pickle tank and tank cover along section line Y—Y;
FIG. 3
is a perspective view of part of a tank cover showing a section having a plenum and an exhaust section;
FIG. 4
is a schematic view, in cross-section, of one pickle tank and tank cover along section line A—A;
FIG. 5
is a schematic view, in cross-section, of one pickle tank and cover along section line Z—Z;
FIG. 6
is a schematic view, in cross-section, of the sealing means between the plenum chamber section and the exhaust section;
FIG. 7
is a sectional view of the sealing means; and
FIG. 8
is a schematic view, in cross-section, of the pickle tank and tank cover of the present invention along view line X—X.
FIG. 9
is a cross-section of the joint between the exhaust section and section with the plenum chamber of the tank cover.
DETAILED DESCRIPTION OF THE INVENTION
There is shown in
FIG. 1
a continuous single length of steel
2
that is being pickled in an acid bath in pickle tank
4
enclosed by a tank cover
6
which is the preferred embodiment of a tank cover of the present invention. Tank cover
6
reduces the cost and improves the efficiency of the steel pickling operation. Tank cover
6
reduces the heat lost from the pickling system, consisting of pickle tank
4
, tank cover
6
and the acid bath, and minimizes escape gases from the system by improving the flow of air and exhaust gases through the pickling system. The pickling of a length of steel
2
is exemplary, as tank cover
6
of the present invention is suitable for covering a tank for pickling any metal product.
Much of the heat supplied to the acid baths in pickling operations in is lost at the surface of the acid bath by liquid evaporation. The heated acid bath solution evaporates into the air space between the acid bath and the tank cover. In conventional pickling systems, the space above the acid bath and below the tank cover is used for transporting exhaust gases, evaporated acid bath fumes and air, to exhaust exits connected to the tank cover. Thus, the exhaust gasses in this space are not static, but form a fluid stream that typically flows in one direction, discharging through the exhaust exits. The contact of this fluid stream with the acid baths increases the evaporation rate at the air-liquid interface of the baths. Increased evaporation leads to increased heat loss which means that more heat must be supplied to the acid baths in order to maintain the acid baths at a constant temperature. Maintaining the acid baths at a constant temperature is important in achieving even pickling of a length of steel product.
To the end of minimizing heat loss and achieving efficiency, tank cover
6
separates the surface of the acid baths in pickle tank
4
from exhaust gas flow through the pickling system. This separation reduces the acid evaporation rate which reduces heat loss and provides for a more efficient control over the exhaust gases.
FIG. 1
shows pickle tank
4
of one embodiment comprising three acid pickle tanks
4
a, b, c
aligned in a series. Any number of pickle tanks may be used depending on the constraints of the system and amount of pickling desired. Each pickle tank
4
a, b, c
is constructed of polyprolene or steel lined with acid brick or granite
8
as shown in
FIG. 2
, a cross section taken along section line Y—Y. Between the steel and acid brick
8
there may be a rubber or plastic layer (not shown). Each pickle tank
4
a, b, c
has a bottom surface
10
a, b, c
, sidewalls
12
a, b, c
, and
14
a, b, c
respectively.
Pickle tank
4
a
has a front wall
16
at the entrance
18
of the pickling system. Front wall
16
has an inlet roller
20
, for feeding steel strip
2
, in front of a lip
22
, shown in more detail in FIG.
4
. Pickle tank
4
a
has a back wall
24
, which joins a front wall
26
of pickle tank
4
b
to form an intermediate wall in pickle tank
4
. Pickle tank
4
b
has a back wall
28
which joins a front wall
30
of pickle tank
4
c
to form another intermediate wall in pickle tank
4
. Pickle tank
4
c
has a back wall
32
which forms an exit
34
of the pickling system along with an outlet roller
36
.
Referring to
FIG. 1
, steel strip
2
enters pickle tank
4
by being fed over inlet roller
20
and over lip
22
of front wall
16
of pickle tank
4
a
. Steel strip
2
dips through the acid bath in pickle tank
4
a
and over a granite skid cap or a pair of intermediate rollers (not shown) provided in pickle tank
4
a
and over another granite skid cap or rollers (not shown) at the junction of each of pickle tanks
4
a
,
4
b
,
4
c
. Steel strip
2
then passes over back wall
32
of pickle tank
4
c
and contacts outlet roller
36
upon its exit from the pickling system.
Tank cover
6
in
FIG. 1
extends the length of pickle tank
4
from steel strip inlet
18
at pickle tank
4
a
to steel strip exit
34
at pickle tank
4
c
. Tank cover
6
is made of a plurality of sections which when connected form a continuous tank cover
6
enclosing pickle tank
4
. Tank cover
6
is constructed of a plurality of exhaust sections
38
each having an exhaust outlet
40
and a plurality of sections
42
which adjoin each other and sections
38
. The number of sections that form a complete tank cover will vary depending on the length of the pickle tank and the length of each section. Tank cover
6
, the preferred embodiment of the present invention, has four (4) exhaust sections
38
and six (6) sections
42
. Tank cover
6
is preferably constructed so that exhaust sections
38
form the entrance and exit of a pickling system, in addition to being spaced evenly along tank cover
6
, in between sections
42
. Since exhaust sections
38
are associated with an external exhaust system and scrubber, they are not normally moved or lifted from pickle tank
4
. Sections
42
are more easily lifted making their removal for access to pickle tank
4
more appropriate.
Shown in
FIG. 3
is the preferred embodiment of one exhaust section
38
and one section
42
of tank cover
6
. Section
42
has an internal cavity
44
formed from a bowed roof or top wall
46
, a first set of two depending side walls
48
a, b
extending downwardly from the longitudinal edges of top wall
46
, a second set of depending sidewalls
50
a, b
connected to and extending downwardly from sidewalls
48
a, b
respectively and a solid bottom wall
52
in between and connecting the second set of side walls
50
a, b.
Internal cavity
44
houses the structural elements, described below, of tank cover
6
. Except for the main structural elements, internal cavity
44
does not communicate with rest of the pickling system. The hollow space of internal cavity
44
may be filled with air.
In the preferred embodiment, internal cavity
44
is disposed within a space created by bottom wall
10
a, b, c
and side walls
12
a, b, c
and
14
a, b, c
of pickle tank
4
. Internal cavity
44
may be disposed within the space of pickle tank
4
so that bottom wall
52
of plenum chamber
58
is less than 12 inches from the surface of the acid bath in pickle tank
4
. The relative sizes of plenum chamber
58
, internal cavity
44
and exhaust section
38
, for example, may be made larger or smaller than the relative sizes shown.
Section
42
covers a section of pickle tank
4
by mounting the first set of depending side walls
48
a, b
of section
42
on top of a section of sidewalls
12
a, b, c
and
14
a, b, c
of pickle tank
4
. In the preferred embodiment, section
42
is mounted such that the first set of depending side walls
48
a, b
meet with sidewalls
12
a, b, c
and
14
a, b, c
allowing side walls depending from side walls
48
a, b
, namely
50
a, b
, to extend freely in space created between the acid bath in-pickle tank
4
and top wall
46
of section
42
. In the preferred embodiment the second set of depending side walls
50
a, b
do not contact sidewalls
12
a, b, c
and
14
a, b, c
of pickle tank
4
.
The first set of depending side walls
48
a, b
run parallel to each other and typically have a skirt
54
at the bottom of each side wll
48
a, b
for mounting on top of a side wall
12
a, b, c
and
14
a, b, c
of any one of pickle tank
4
a, b, c
, as shown clearly in
FIG. 2. A
liquid may provide the seal between skirt
54
and the top of sidewall
12
a, b, c
and
14
a, b, c
. A liquid seal or other type of seal that provides for thermal expansion would be preferred.
As previously mentioned, depending from side walls
48
a, b
are side walls
50
a, b
respectively which also run parallel to each other. Each depending side wall
50
a, b
depends directly from a member
56
a, b
respectively connected to each depending side wall
48
a, b
. Members
56
a, b
extend in the direction of internal cavity
44
from depending side walls
48
a, b
. Depending side walls
50
a, b
are narrower in width than depending side walls
48
a, b
so that depending side walls
50
a, b
may extend into pickle tank
4
below the top of side walls
12
and
14
.
Connecting depending side walls
50
a, b
is solid bottom wall
52
. Solid bottom wall
52
is both the bottom wall of internal cavity
44
of section
42
and the bottom wall of a plenum chamber
58
, a separate structure, formed in internal cavity
44
. Plenum chamber
58
, shown in cross-section midway along the length of section
42
in
FIG. 2
, is formed by top wall
62
, depending side walls
50
a
and
50
b
and bottom wall
52
. Bottom wall
52
, side walls
50
a
and
50
b
and top wall
62
form an enclosed space
64
which is plenum chamber
58
.
Plenum chamber
58
is for collecting evaporated acid fumes and transporting these fumes to exhaust outlets
40
which are connected to exhaust section
38
. The arrows in
FIG. 3
represent the flow of exhaust gases from plenum chamber
58
through exhaust section
38
to exhaust outlet
40
. The separate collection and transportation of exhaust gases in plenum chamber
58
does not disturb the air-liquid interface of the acid bath, which reduces the liquid evaporation rate at the acid bath surface which minimizes heat loss in the pickling system. Additionally, the rate of exhaust of exhaust gas from the system may be increased by increasing the flow rate of exhaust gas through plenum chamber
58
, because plenum chamber
58
is an enclosed chamber within internal cavity
44
of section
42
. Increasing flow rate of exhaust gasses would normally cause excessive acid evaporation if there was no exhaust gas—acid bath separation.
In the preferred embodiment, plenum chamber
58
has a rectangular shape at cross section Y—Y however, other shapes are possible.
As shown in FIG.
1
. section
42
may be connected to another similar section
42
as well as to exhaust section
38
. Exhaust section
38
is connected to exhaust outlet
40
further connected to an external scrubber. In the preferred embodiment, exhaust outlet
40
is positioned on the center of a top wall
68
, although it may occupy any position on top wall
68
. Exhaust section
38
may have external support ribs
65
as shown in FIG.
3
. Support ribs
65
help maintain the structure of section
38
.
FIG. 4
illustrates the main internal elements of exhaust section
38
at the entry or exit to the pickling tanks. In the preferred embodiment, exhaust section
38
has an internal space
66
created by a bowed roof or top wall
68
, two parallel side walls
70
a, b
depending therefrom and a solid bottom wall
71
, with the profile of the aforementioned walls matching the profile of the corresponding walls of abutting section
42
as shown in
FIGS. 3 and 4
. In other words, the shape of the cross-section of top wall
68
is the same as shape as that of top wall
46
of section
42
. The other walls have the same cross-sectional shape for a matching fit when section
42
abuts exhaust section
38
.
The internal space
72
of exhaust outlet
40
cooperates with the internal space
66
of exhaust section
38
which cooperates with the enclosed space
64
of plenum chamber
58
of section
42
. When tank cover
6
is assembled there is at least one enclosed space extending from tank inlet
18
to tank exit
34
created by the association of plenum chamber
64
in all sections
42
with internal space
66
of all exhaust sections
38
which is further associated with internal space
72
of all exhaust outlets
40
. Tank cover
6
could be designed with more than one internal plenum chamber.
Inside the enclosed space extending from tank inlet
18
to tank exit
34
exhaust gases collect and may be transported to and discharged from exhaust outlets
40
. As previously mentioned the enclosed space within tank cover
6
of the present invention separates the surface of the acid baths in pickle tank
4
from exhaust gas flow through the pickling system. This separation reduces the acid evaporation rate which reduces heat loss and provides for a more efficient control over the exhaust gases. It should be noted however that only a minimum of exhaust gases and air should be removed from the pickling operation. The less removal of gases the more energy conserved.
The junctures between any two sections
38
and
42
of tank cover
6
are preferably sealed so that no exhaust gases from the inside of the pickling system escape to the outside. In the preferred embodiment, a flexible seal
74
is disposed along the perimeter of the top wall and depending side walls of any two sections
38
and
42
to close the inside of the pickling system from the outside.
FIG. 4
illustrates a joint between an exhaust section
38
and a section
42
while
FIG. 5
is a cross-section (section Z—Z) of a section
42
taken where the section
42
abuts another section
42
. In
FIG. 5
, the location of the flexible seal
74
is shown along the perimeter of top wall
46
and depending side walls
48
a, b
. The flexible seal
74
, which is the same as the seal means used between sections
38
and
42
, is connected to a holding member
76
further connected to a support member
78
, as shown clearly in FIG.
6
. Flexible seal
74
is preferably a flexible material that can withstand degradation by exposure to acid fumes and acid liquid. Flexible seal
74
may be neoprene rubber for example.
FIG. 7
is a top view of the flexible seal shown in
FIGS. 4 and 6
.
FIG. 7
illustrates a tight fit between flexible seal
74
and abutting section
42
.
While the top walls and side walls depending therefrom of any two sections
38
and
42
abut with no gap at their juncture, the internal spaces of the two sections, namely space
66
and plenum chamber
58
respectively, are not likewise connected in the preferred embodiment, leaving a gap
80
between them, which is ¼ inch at the maximum and preferably {fraction (1/16)} inch think. Gap
80
is located at the junction of any two sections. Gap
80
cooperates with the inside of pickle tank
4
and the enclosed space of tank cover
6
. Acid fumes evaporate from the acid baths in pickle tank
4
and rise (see arrows in FIG.
2
and
FIG. 9
) until they eventually rise into one of gaps
80
between any two sections
38
and
42
. Exhaust gases enter gap
80
where they collect and join the stream of air and exhaust gases traveling through the enclose space of tank cover
6
, extending from tank inlet
18
to tank exit
34
, to be discharged out exhaust outlets
40
. Because exhaust fumes enter plenum chamber
58
at gaps
80
located at the junctures of sections
38
and
42
, fume removal is limited to specific locations which also helps minimize heat loss.
At the juncture of any two sections
38
and
42
, gaps
80
preferably extends the width of bottom wall
52
of section
42
because plenum chamber
58
also preferably extends the width of bottom wall
52
. Plenum chamber
58
could be positioned so that it does not extend the entire width of bottom wall
52
of section
42
. Instead, in another embodiment, plenum chamber
58
may be located to one side of pickle tank cover
6
.
As previously mentioned gap
80
provides one opening area for the collection of fumes that evaporate from the acid bath in pickle tank
4
. In addition to this gap
80
at the juncture of any two tank sections
38
and
42
are adjustable orifice plates
82
located on bottom wall
52
of section
42
. Adjustable orifice plate
82
, illustrated clearly in
FIG. 3
, allows for the additional collection of fume gas as well as the balance of air in the fume transport system in plenum chamber
58
. Orifice plates
82
are used if the inside vapor pressure is to great causing fumes to escape out of the cover junctions or if a seal fails. Orifice plates
82
can be adjusted so the static pressure is the same at each exhaust outlet
40
so movement of air across the bath surface is minimized.
FIG. 5
illustrates the cross section of pickle tank
4
and tank cover
6
at section line Z—Z. The cross section shows that plenum chamber
58
extends along the entire bottom wall
52
of tank cover
6
and almost the entire width of acid pickle tank
4
. The plenum chamber
58
spans almost the complete pickle tank
4
width in order to capture any fumes evaporating from the acid bath surface. It also serves the purpose that if any cover section
42
is lifted from acid tank
4
then the fume exhaust section
38
will capture all of the fumes across the entire tank width. When this happens, the system is increased in capturing capacity. The fumes will be transported through plenum chamber
64
to exhaust section
38
where they will discharge through exhaust outlet
40
. After tank cover section
42
is removed, of course, the exhaust system will no longer be a relatively closed system but will contain a gap in which exhaust fumes may escape.
Another feature of tank cover
6
of the present invention are the air inlet sections at the entrance
18
and exit
34
of tank cover
6
designed to minimize escape gases from the pickling system. When tank cover
6
is fully assembled no air can escape through the top of tank cover
6
. A small amount of air will enter the pickle tank system at inlet
18
and outlet
34
shown in FIG.
1
. To prevent the escape of exhaust fumes a small inlet duct
84
extends down from exhaust section
38
, shown in detail in FIG.
4
. Inlet duct
84
is associated with the exhaust system so that air entering the pickling system is drawn into inlet duct
84
and discharged through exhaust outlet
40
. This flow of air into the inlet duct
84
forms an air curtain to prevent the escape of exhaust gases from the pickle tank
4
. Also to prevent air from entering the pickle tank system from below the steel strip, a small air flow chamber
86
is constructed just under lip
22
of end wall
16
at both the inlet
18
and exit
34
as shown in FIG.
1
. Air flow chamber
86
works in concert at the ends with air flow chamber
84
to allow exhaust discharge through exhaust outlet
40
.
FIG. 8
a view in cross-section taken along line X—X shows this flow of air around the steel strip into inlet duct
84
and air flow chamber
86
around the steel strip entering pickle tank
4
a.
FIG. 9
is a cross-section of the joint between exhaust section
38
and section
42
of tank cover
6
. The arrows represent the flow of exhaust gases through tank cover
6
and pickle tank
4
.
The preferred method of pickling a length of metal strip is as follows:
providing a pickle tank having a bottom wall, end walls and side walls for containing an acid bath for pickling metal strip; providing a means for introducing metal strip over one end wall of the tank, passing the metal strip through the acid bath and over an opposite end wall of the tank; providing a pickle tank cover substantially completely covering the pickle tank and acid bath and having a top wall, bottom wall end wall and side walls thereby creating an internal cavity and an exhaust means connected to the top wall; forming a plenum chamber in the internal cavity of the pickle tank cover, communicating with the exhaust means and disposed within the space formed by the side walls and bottom wall of the pickle tank; directing vapors from the acid bath to the plenum chamber; and exhausting the vapors out of the plenum chamber to the exhaust means.
Thus the design of the entire pickle tank cover provides a separation of exhaust gases from the air liquid interface of the acid bath as well as improves air flow along the exhaust system including an increased rate of exhaust and provides for the capture of exhaust gases at the inlet and outlet providing for a more efficient use of the air. Additionally this unique design allows for the capture of gases along the entire width of the acid tank and the transportation of these fumes in a relatively closed system to exhaust outlets at certain intervals along the tank.
While there has been illustrated and described several embodiments of the present invention, it will be apparent that various changes and modifications thereof will occur to those skilled in the art. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the present invention.
Claims
- 1. An improved cover for containment and exhaust of fumes from an acid bath in a pickling line having,a) a pickle tank having a bottom wall, end walls and side walls for containing an acid bath for pickling metal strip; b) means for introducing metal strip over one end wall of the tank, passing the metal strip through the acid bath and over an opposite end wall of the tank; said improved cover, substantially completely covering the pickle tank and acid bath, and comprising:a top wall; side walls depending from the top wall which include a means to support the cover on the side walls of the pickle tank; end walls at each end of the cover depending from the top wall and forming a gap with the end walls of the pickle tank to permit the introduction or exit of metal strip; a bottom wall connecting the depending side walls and forming an internal cavity bounded by the top wall, the side walls and the bottom wall of the cover; a plenum chamber formed in said internal cavity and sharing at least a bottom wall with the cover and extending from one end wall of the cover to approximately the opposite end wall of the cover; and at least one exhaust means mounted on the cover and communicating with the plenum chamber, whereby evaporating fumes from the acid bath are confined to the plenum chamber and exhausted from the pickle tank.
- 2. The improved cover of claim 1, wherein said internal cavity of said improved cover is disposed within a space formed by the side walls and bottom wall of the pickle tank.
- 3. The improved cover of claim 1, wherein the plenum chamber has at least one orifice plate on the bottom wall of said chamber to allow for adjusting the collection of evaporated fumes from the acid bath.
- 4. The improved cover of claim 1, wherein at least one air duct having an open end directed to said gap formed between the end wall of the cover and the end wall of the pickle tank and an opposite end in communication with the open end and an exhaust system, is positioned on at least one of the end walls of the cover for drawing in, from outside the pickle tank, air surrounding the metal strip as it enters and exits the pickle tank.
- 5. The improved cover of claim 1, wherein at least one air chamber having an open end directed to said gap formed between the end wall of the cover and the end wall of the pickle tank and an opposite end in communication with the open end and an exhaust system, is positioned on at least one of the end walls of the pickle tank for drawing in air surrounding the metal strip as it enters and exits the pickle tank.
- 6. An improved cover for containment and exhaust of fumes from an acid bath in a pickling line having,a) a pickle tank having a bottom wall, end walls and side walls for containing an acid bath for pickling metal strip; b) means for introducing metal strip over one end wall of the tank, passing the metal strip through the acid bath and over an opposite end wall of the tank; said improved cover having a plurality of adjoining sections, substantially completely covering the pickle tank and acid bath, comprising:at least one plenum section further comprising,a top wall; side walls depending from the top wall which include a means to support at least one plenum section on the side walls of the pickle tank; a bottom wall connecting the depending side walls and forming an internal cavity bounded by the top wall, the side walls and the bottom wall of at least one plenum section; a plenum chamber formed in said internal cavity and sharing at least a bottom wall with at least one plenum section and extending from one end wall of the cover to approximately the opposite end wall of the cover; and at least one exhaust section further comprising,a top wall; side walls depending from the top wall which include a means to support at least one exhaust section on the side walls of the pickle tank; a bottom wall connecting the depending side walls and forming an internal cavity bounded by the top wall, the side walls and the bottom wall of at least one exhaust section; at least one exhaust means mounted on at least one exhaust section and communicating with the plenum chamber of the plenum section; and end walls at each end of the cover depending from the top wall of either at least one plenum section or at least one exhaust section and forming a gap with the end walls of the pickle tank to permit the introduction or exit of metal strip; whereby evaporating fumes from the acid bath are confined to the plenum chamber of at least one plenum section and exhausted from at least one exhaust section of the pickle tank.
- 7. The improved cover of claim 6, wherein said internal cavity of at least one plenum section and at least one exhaust section is disposed within a space formed by the side walls and bottom wall of the pickle tank.
- 8. The improved cover of claim 6, wherein at least one plenum chamber of the plenum section has at least one orifice plate on the bottom wall of said chamber to allow for the collection of evaporated fumes from the acid bath.
- 9. The improved cover of claim 6, wherein a seal is disposed between at least one adjoining plenum section and at least one adjoining exhaust section or between like sections, for inhibiting the escape of exhaust gases from the pickle tank.
- 10. The improved cover of claim 9, wherein the seal is made of neoprene rubber.
- 11. The improved cover of claim 6 wherein gaps are formed at the location where the plenum chamber of at least one plenum section joins at least one exhaust section and the location where the plenum chamber of at least one plenum section joins the plenum chamber of at least one other plenum section.
- 12. The improved cover of claim 6, wherein at least one air duct having an open end directed to said gap formed between the end wall of the cover and the end wall of the pickle tank and an opposite end in communication with the open end and an exhaust system, is positioned on at least one of the end walls of the cover for drawing in air surrounding the metal strip as it enters and exits the pickle tank.
- 13. The improved cover of claim 6, wherein at least one air chamber having an open end directed to said gap formed between the end wall of the cover and the end wall of the pickle tank and an opposite end in communication with the open end and an exhaust system, is positioned on at least one of the end walls of the pickle tank for drawing in air surrounding the metal strip as it enters and exits the pickle tank.
US Referenced Citations (20)
Foreign Referenced Citations (3)
Number |
Date |
Country |
1112682 |
Aug 1961 |
DE |
2415151 |
Sep 1979 |
FR |
46-11561 |
Jul 1971 |
JP |