US20140230919A1

US20140230919A1 - Valve seal for a diverter assembly

Info

Publication number: US20140230919A1
Application number: US13/770,485
Authority: US
Inventors: Robert Rhoads
Original assignee: ADVANCED VALVE DESIGN Inc
Current assignee: ADVANCED VALVE DESIGN Inc
Priority date: 2013-02-19
Filing date: 2013-02-19
Publication date: 2014-08-21

Abstract

A valve for controlling the flow of a waste gas stream received from an industrial process is disclosed. The valve includes ducts to permit entry of the stream for removal of harmful VOCs and exit of the treated gas stream to the atmosphere. The valve includes several open frames extending radially from a central axis. A distribution blade mounted on the axis rotates between two positions to control the flow of the stream through the open frames during processing. A seal ring mounted to each open frame forms a seal with the distribution blade when in contact with the frame. Pressurized air delivered within the seal ring during contact with the blade acts to significantly reduce of the gas stream from within the valve to the atmosphere during operation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

(Not Applicable)

BACKGROUND OF THE INVENTION

Field of Invention

The present invention relates to regenerative thermal oxidizers for destroying volatile organic compounds (VOCs) in emissions from industrial processes. More specifically, the present invention relates to a valve for controlling the flow of a waste gas stream through such an oxidizer that reduces the amount of waste gas streams that are leaked to the atmosphere.
VOCs are found in significant amounts in waste gas streams created as a result of the implementation of industrial processes. Since VOCs are a precursor of smog, the amount of VOCs that are released into the atmosphere need to be substantially reduced or eliminated entirely. Increasingly stringent state and federal legislation impose the need to control the emission of Volatile Organic Compounds (VOCs) to the atmosphere. The industries and processes that need to control their output of VOCs include the printing, chemical, pharmaceutical manufacturing, automotive coating and painting, bakeries, can coating, wood manufacturing, medical device sterilization, soil remediation, and metal decorating industries, among others. Waste process gas streams must be passed through facilities that can eliminate the VOCs from the streams.
Regenerative thermal oxidizers are conventionally used for destroying volatile organic compounds (VOCs) in high flow, low concentration emissions from industrial and power plants. Such oxidizers typically require high oxidation temperatures in order to achieve high VOC destruction. To achieve high heat recovery efficiency, the process gas that is to be treated is preheated before oxidation. A heat exchanger is typically provided to preheat these gases. The heat exchanger is usually packed with material having good thermal and mechanical stability and sufficient thermal mass. In operation, the process gas is fed through a previously heated heat exchanger, which, in turn, heats the process gas to a temperature approaching or attaining its VOC oxidation temperature. This pre-heated process gas is then directed into a combustion zone where any incomplete VOC oxidation is usually completed. The treated gas is then directed out of the combustion zone and through a second heat exchanger. As the hot oxidized gas continues through this second heat exchanger, the gas transfers its heat to the heat exchange media, cooling the gas and pre-heating the heat exchange media so that another batch of process gas may be preheated prior to the oxidation treatment. Usually, a regenerative thermal oxidizer has at least two heat exchangers, which alternately receive process and treated gases. This process is continuously carried out, allowing a large volume of process gas to be efficiently treated.
The performance of a regenerative oxidizer may be optimized by increasing VOC destruction efficiency. Various manners for increasing VOC destruction efficiency have been addressed in the prior art. An important element of an efficient oxidizer is the valving used to switch the flow of process gas from one heat exchange column to another. Any leakage of untreated process gas through the valve system will decrease the efficiency of the apparatus and result in untreated process gas containing VOCs being released to the atmosphere. It therefore would be desirable to reduce or eliminate the amount of leakage of untreated process gas through the valving used to switch the flow of process gas from one heat exchanger to another.

BRIEF SUMMARY OF THE INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

FIG. 1 is a perspective view of a regenerative thermal oxidizer, in which the control valve of the present invention is implemented;

FIG. 2 is an elevational view of the control valve of the present invention;

FIG. 3 is a top view of the control valve of the present invention;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a top view of the control valve of the present invention illustrating rotational movement of the gas flow distribution blade mounted therein between first and second positions;

FIG. 5A is a cross-sectional view taken along line 5A-5A of FIG. 4;

FIG. 6 is an enlarged broken view of the flow distribution blade in an abutting position with the frame of the control valve of the present invention; and,

FIG. 7 is an enlarged view of the seal ring component of the control valve of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in detail to the various figures of the drawings wherein like reference characters refer to like parts, there is shown at 10 in FIG. 1 a two-chamber regenerative thermal oxidizer, the operation of which will be explained and illustrated in detail. The oxidizer 10 includes a housing 14 in which there are first and second heat exchangers 18 and 22, which include a heat recovery media, the heat exchangers being in communication with a centrally located combustion zone 26. Each heat exchanger 18, 22 may also include filtration media for filtering VOCs from waste gas streams. A burner 30 may be located within the combustion zone 26 and a combustion blower (not shown) may be supported within the housing 14 to supply combustion air to the burner. A fan (not shown) is supported on the housing 14 for driving or drawing the process gas into the oxidizer 10. The housing 14 includes a top chamber or roof 34. Those skilled in the art will appreciate that the foregoing description of the oxidizer 10 is for illustrative purposes only; other designs are well within the scope of the present invention, including oxidizers with more or less than two chambers, oxidizers with horizontally oriented chamber(s), and catalytic oxidizers.
In operation, a stream of gas 38 containing contaminants such as VOCs flows into a process gas inlet conduit 42 of the oxidizer 10 and thereafter into a control valve 50 which alternately directs flow of the gas stream 38. In a first direction, the control valve 50 directs the process gas 38 out of the control valve 50 and through the heat exchanger 18, which has been previously heated, thus increasing the temperature of the gas stream 38 to a temperature approaching or attaining its VOC oxidation temperature. This pre-heated gas stream 38 is then directed into the combustion zone indicated generally at 26 where any incomplete VOC oxidation is usually completed by the gas stream 38 passing over the burner 30. Within the combustion zone 26, the gas stream 38 is further heated to the required oxidation temperature and held for a predetermined period of time, e.g., up to one second, at that temperature to allow for adequate destruction of the VOCs. The treated gas stream 38 is then directed out of the combustion zone 26 and through the second heat exchanger 22, whereupon the gas stream 38 transfers its heat to the media of the heat exchanger 22, cooling the gas 38 and pre-heating the media of the heat exchanger 22 so that another batch of process gas 38 directed by the control valve 50 in the opposite direction may be preheated prior to the oxidation treatment. Thereafter, the cooled and treated gas stream 38 is directed into the control valve 50 and then to an exhaust stack 54 where it is released to the atmosphere.
Periodically, the control valve 50 reverses the direction of flow and the gas stream 38 flows in an opposite route. That is, with the heat exchanger 22 preheated, the control valve 50 switches to direct flow of the gas stream 38 along an opposite route. Along this opposite route, the gas stream 38 flows into the control valve 50 from the inlet 42 and flows out of the control valve 50 over the pre-heated heat exchanger 22 to increase the temperature of the gas stream 38 to a temperature approaching or attaining its VOC oxidation temperature. The pre-heated gas stream 38 is then directed into the combustion zone 26 where VOC oxidation is completed. The treated gas 38 is then directed out of the combustion zone 26 and through the heat exchanger 18, whereupon the process gas 38 transfers its heat to the heat exchanger 18, cooling the gas 38 and pre-heating the heat exchanger 18. Thereafter, the cooled gas stream 38 is directed back through the control valve 50 and out to the exhaust stack 54, where it is released to the atmosphere.
As explained above, usually, a regenerative thermal oxidizer 10 has at least two heat exchangers, which alternately receive process and treated gases. This process is continuously carried out, allowing a large volume of process gas to be efficiently treated. The back and forth switching between heat recovery beds 18 and 22 occurs every three to six minutes in most cases. In the embodiment shown, flow through the heat exchangers 18 and 22 is vertical wherein contaminated gas enters the heat exchangers from below or above. However, those skilled in the art will appreciate that other orientations are suitable including a horizontal arrangement.
Referring now to FIGS. 4, 5 and 5A, the details and operation of the control valve 50 are discussed. As best shown in FIGS. 5 and 5A, the control valve 50 includes a housing 60 having a plurality of walls 64, e.g., four walls, a floor 68, and a ceiling 72 (best shown in cut-away in FIG. 3). An L-shaped angle iron 76 having a plurality of through mounting holes (best shown in FIGS. 6 and 7) is affixed to interior surface of each wall 64 by any suitable means, e.g., welding. The angle irons 76 affixed to the four walls 64 extend vertically approximately the height of the wall 64 from the floor 68 to the ceiling 72. As best shown in FIG. 4, a plurality of angle irons 76, e.g., four angle irons, are affixed to the ceiling 72 in like fashion and extend radially from a location in proximity to a vertical axis 80 to each of the four angle irons 76 affixed to the four walls 64. Likewise, a plurality of angle irons 76, e.g., four angle irons, are affixed to the floor 68 and extend radially from a location in proximity to the vertical axis 80 to meet with each of the four wall angle irons 76. In this manner, as best shown in FIGS. 4, 5 and 5A, the angle irons 76 affixed to the floor, walls and ceiling form four frames 88, 92, 96, and 100 having large rectangular openings, wherein the angle irons 76 are suited for mounting a seal assembly 104 thereto.
Referring now to FIGS. 6 and 7, a portion of the seal assembly 104 is illustrated therein as being mounted to an angle iron 76. When mounted to the angle irons 76 locate on the floor 68, walls 64, and ceiling 72, the seal assembly 104 forms a continuous seal thereover by utilizing mitered corners as illustrated in FIG. 7. Each seal assembly 104 includes an outer sealing leaf 108 and an inner sealing leaf 112, the sealing leaves being similarly configured. Each sealing leaf 108 and 112 includes a plurality of regularly spaced mounting holes for mounting to a manifold bar 116 situated therebetween. The sealing leaves 108 and 112 are made of any suitable material, e.g., spring steel which may consist of a longitudinal ribbon or band of spring steel. The manifold bar 116 is disposed between the sealing leaves 108, 112 and is also provided with a plurality of regularly spaced mounting holes for securing the sealing leaves thereto on opposite sides thereof. As mounted, the sealing leaves 108 and 112 are spaced from one another to create a seal gap 120 therebetween (FIG. 6). The sealing leaves are mounted utilizing suitable hardware, e.g., nuts 124 and bolts 128. As best shown, the seal assembly 104 is affixed to the angle irons 76 at regularly spaced intervals within frame openings 92 a and 100 a.
As best shown in FIG. 6, the manifold bar 116 includes a second set of regularly spaced through openings 132 that are flared at one end 132 a. These flared openings 132 a are arranged for attachment of hose segments 136 thereto by utilizing a suitable hose connector 140. Other hose connectors 144 suitable for attaching the plurality of hose segments 136 to each other are also provided. The hose segments 136 are provided for delivering pressurized air from a source (not shown) through the flared openings 132 a and into the seal gap 120 to increase the effectiveness of the seal as will be discussed below. A metal plate 148 is also included as part of the seal assembly 104 to increase rigidity. The sealing leaves 108 and 112 are similarly configured in that each includes a free end that bends at an angle approximating forty-five degrees and bends again so that the free end of the sealing leaves 108 and 112 extends in a direction that is approximately parallel to the gas flow distribution blade 176 when the blade 176 is in contact with the sealing leaves so as to form an effective seal in a manner to be discussed further below.
Referring again to FIGS. 5 and 5A, the housing 60 includes an inlet opening 152, an opposed outlet opening 156, and opposed ducts 160 and 164 for directing process gas in and out of the control valve 50 during operation. The inlet opening 152 is in communication with the inlet conduit 42 (FIG. 1) and the outlet opening 156 is in communication with an outlet conduit 158 (FIG. 1) which leads to the exhaust stack 54 (FIG. 1). The duct 160 provides communication between control valve 50 and heat exchanger 18 through conduit 168 (FIG. 1), while duct 164 provides communication between the control valve 50 and the heat exchanger 22 through conduit 172 (FIG. 1).
Located centrally within the housing 50 is a stationary vertical axis 80 on which a gas flow distribution blade 176 is rotatably mounted. The blade 176 includes a circular hub 180 disposed over the vertical axis 80 and first and second blade portions, indicated at 176 a and 176 b, that extend in opposite directions from the hub 180. Referring now to FIGS. 4, 5, and 5A, the housing 60 of the control valve 50 includes the plurality of frames, indicated at 88, 92, 96, and 100. Each frame includes a seal assembly 104 mounted thereon, as described previously. As shown in these figures, each of these frames extends radially from a location in proximity to the central axis 80 towards the perimeter of the housing 60.
As shown in FIGS. 3, 5, and 5A, the blade 176 is arranged for rotary movement from a first position to a second position. As best shown in FIG. 5A, in the first position, the blade segment 176 a is contacting frame 92 and blocking the passage of any gas stream 38 through frame 92 while blade segment 176 b is contacting frame 100 to block the passage of any gas stream therethrough. As best illustrated in FIG. 6, to create an effective seal, when in this first position, blade segment 176 a makes contact with the free end of leaves 108 and 112 of the seal assembly 104 extending around the periphery of frame 92 to create a seal at the seal gap 120 to significantly reduce or eliminate the amount of gas stream 38 leaking across frame 92 and inadvertently escaping to the atmosphere. Additionally, pressurized air pumped into the seal gap 120 through hose segments 136 and the openings 132 of the manifold bar 116, contributes to significantly reducing the amount of gas stream 38 leaking across open frame 92 and escaping to the atmosphere. In similar fashion, blade segment 176 b contacts the free ends of leaves 108 and 112 of the seal assembly 104 extending around the periphery of frame 100 to create a seal at its seal gap 120, which in combination with the pressurized air pumped into the seal gap 120 acts to significantly reduce the amount of gas stream 38 leaking across open frame 100 and escaping to the atmosphere.
Since in the first position blade segments 176 a and 176 b are not in contact with frames 88 and 96, these frames remain open for the passage of gas streams therethrough. Thus, as indicted by arrows 224 and 228 in FIG. 5A, process gas 38 entering the control valve 50 through the inlet conduit 42 flows through the opening of frame 88 and out of the control valve 50 through duct 160 and to the heat exchanger 18. Once the gas stream 38 has been processed through heat exchanger 18, combustion zone 26, and heat exchanger 22, as indicated by arrows 232 and 236, the process gas 38 re-enters the control valve 50 through duct 164, through the opening of frame 96, and out through outlet opening 156, where it is released to the atmosphere through the stack 54 (FIG. 1).
The back and forth switching of the blade 176 between the first and second positions controls the path of flow of the process gas 38 between heat exchangers 18 and 22. After a predetermined amount of time, the blade 176 is arranged to rotate from this first position through approximately 90 degrees to a second position (not shown) whereby the blade segment 176 a blocks open frame 96 while blade segment 176 b blocks open frame 88. In a similar manner, seal assemblies 104 extend around the periphery of open frames 88 and 96. Blade segments 176 a and 176 b contact the free ends of leaves 108 and 112 of the seal assemblies 104 while pressurized air is pumped into the seal gap 120 of these seal assemblies 104 to significantly reduce the amount of gas stream 38 leaking across open frames 88 and 96. FIG. 5 best illustrates movement of blade 176 between the first and second blocking positions discussed above.
Since in the first position blade segments 176 a and 176 b do not contact frames 92 and 100, these frames remain open for the passage of gas streams therethrough. Thus, when the blade 176 is in the second position, the gas stream 38 will travel along the opposite route, as previously mentioned. That is, when in the second position, the flow of process gas 38 through frames 88 and 96 will be blocked in similar manner as described above. Thus, process gas 38 entering the control valve 50 through the inlet conduit 42 (FIG. 1) and opening 152 flows through the opening of frame 100 and out of the control valve 50 through duct 164 and to the heat exchanger 22 previously heated by the gas stream 38 traveling in the first direction. Once the gas stream 38 has processed through the heat exchanger 22, combustion zone 26, and heat exchanger 18, the process gas 38 re-enters the control valve 50 through duct 160, passes through the opening of frame 92, and out through outlet opening 156, where it is released to the atmosphere through the stack 54 (FIG. 1).
Referring now to FIGS. 2 and 3, rotational movement of the blade 176 is controlled by an actuatable pneumatic assembly 200 positioned within a box 204 located above the housing 50 by attachment to brackets 205 extending upwardly from the housing 50. The pneumatic assembly 200 includes lead wires 202 which connect in to a conventional source of power and control (not shown), from which the assembly 200 may be remotely actuated and controlled in known ways. In particular, the pneumatic assembly 200 includes a cylinder 208 and a piston 212 disposed therein. As best illustrated in FIG. 3, in response to actuation, the piston 212 is arranged to move between a retracted position (shown in solid lines) and an extended position (shown in dotted lines). The retracted and extended positions are limited by stops 216 affixed to the box 204, so as limit movement of the piston 212 between the retracted and extended positions. In this manner, rotation of the blade 176 may be limited between the first and second positions. The piston 212 is affixed to an arm 220 which is affixed to the hub 180 of the blade 176. In this manner rotational movement of the blade 176 between the first position through approximately 90 degrees to the second position may be controlled.
It is understood that the control valve and its constituent parts described herein is an exemplary indication of a preferred embodiment of the invention, and is given by way of illustration only. In other words, the concept of the present invention may be readily applied to a variety of preferred embodiments, including those disclosed herein. While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims

1. A control valve for use in a gas flow installation for controlling a gas stream flowing therethrough, said control valve comprising:

a. a stationary housing for communicating with the gas flow installation, said housing including a central axis and a plurality of open frames extending in generally radial directions from said axis including a first frame and a second frame, a delivery duct and an exit duct to enable the entry and exit of gas through said installation and a plurality of openings disposed about the housing periphery for controlling gas stream flow;

b. a gas flow distribution blade for alternating the flow of the gas stream through the fluid flow installation, said blade extending radially in at least one direction from said central axis and arranged for rotation on said axis between a first position wherein said blade is in abutting relation with said first open frame to a second position wherein said blade is in abutting relation with said second open frame;

c. a seal ring mounted to each of said first and second open frames, said seal ring adapted to form a seal between said blade and said first or second open frame when said blade is in said first or second position; and,

d. wherein when said blade is in said first position, said delivery duct is in fluid communication with a first opening to define a first gas stream inlet path, and when said blade is rotated to said second position, said delivery duct is in fluid communication with a second opening to define a second gas stream inlet path.

2. The control valve of claim 1, wherein each said seal ring comprises a pair of elongated similarly configured leaves spaced-apart from each other a predetermined distance so as to form a gap therebetween.

3. The control valve of claim 2, wherein a manifold is situated within said gap to supply pressurized gas about said seal ring.

4. The control valve of claim 2, wherein each of said leaves is formed of a flexible material.

5. The control valve of claim 2, wherein each of said leaves includes a fixed end affixed to said frame and a free end extending from said fixed end and arranged for contacting said blade when abutting said frame to form said seal.

6. The control valve of claim 4, wherein said free end of said leaves is bent at a predetermined angle.

7. The control valve of claim 1, additionally comprising third and fourth open frames extending radially from said axis each having a seal ring mounted thereon to form a seal between said blade and said third and fourth open frames, wherein said blade extends radially in two opposite directions from said axis and is arranged for rotation between said first position wherein said blade is in abutting relation with said first and third open frames to a said second position wherein said blade is in abutting relation with said second and fourth open frames.

8. The control valve of claim 7, wherein when said blade is in said first position, said delivery duct is in fluid communication with first opening to form a first gas stream inlet path and said second opening is in fluid communication with an exit duct to form a first gas stream outlet path, and when said blade is in said second position, said delivery duct is in fluid communication with said second opening to form a second gas stream inlet path, and said first opening is in fluid communication with said exit duct to form a second gas stream outlet path.

9. The control valve of claim 1, wherein said fluid flow installation is regenerative thermal oxidizer.

10. The control valve of claim 1, wherein said frames are generally rectangular in shape and include a large rectangular opening.

11. The control valve of claim 1, wherein said blade is reciprocable between said first and second positions.

12. The control valve of claim 3, wherein said manifold is comprised of a length of bar stock having a plurality of through bores extending into said gap, said bores serving as ports to transmit pressurized air from an air source through a plurality of tubes and into said gap.

13. The control valve of claim 8, wherein when said blade is in said first position, flow of gas through the first and third open frames is blocked, and wherein when said blade is in said second position, flow of gas through said second and fourth open frames is blocked.

14. The control valve of claim 1, wherein the gas flow installation is a regenerative thermal oxidizer and the gas stream contains volatile organic compounds.