Patent Description:
A fluid flow diverter reroutes the flow of fluids through a system. Fluid flow diverters are used to minimize the commingling of different fluid streams in systems that require a rapid change in the flow pattern of the fluids. One such system is a regenerative thermal oxidizer (RTO), which is used in a number of industries to reduce the quantity of contaminants in industrial process effluent gases.

In an RTO, incoming process effluent gases are oxidized in a combustion chamber and then directed through a heat exchanger before being sent to an exhaust stack. In the heat exchanger, up to <NUM>% of the heat from the high-temperature combustion gases is transferred to the heat exchange media. The flow of gases is then rerouted so that the incoming process gases move through that heat exchanger before entering the combustion chamber. Heat is transferred from the hot heat exchange media to the process gases so that less energy is required to oxidize the process gases in the combustion chamber.

A two chamber RTO has two heat exchangers that are separately connected to a shared combustion chamber. A first flow path begins with the first heat exchanger, then goes to the combustion chamber, and then passes through the second heat exchanger and on to the exhaust stack. After the second heat exchanger captures heat from the outgoing gases, the gas flow through the RTO is rerouted so that the incoming process gases can be heated by the second heat exchanger. In particular, the incoming gases are redirected so as to follow a second flow path that begins with the second heat exchanger, then goes to the combustion chamber, and then passes through the first heat exchanger and on to the exhaust stack. After the first heat exchanger captures heat from the outgoing gases, the gas flow through the RTO is rerouted back to the first flow path, and the process is repeated. A fluid flow diverter is used to accomplish this repeated rerouting of the fluid flow through the RTO while minimizing the discharge of unoxidized process gas into the atmosphere.

A conventional fluid flow diverter typically includes a valve system that uses poppet valves connected to a valve shaft. The gas moving through the valve is directed by the position of a disc (or "poppet") that is moved linearly between two opposed valve seats. One example of such a fluid flow diverter that can be used use in a two chamber RTO is disclosed in <CIT>, entitled "Valve System for Regenerative Thermal Oxidizers," the entire disclosure of which is herein incorporated by reference. This fluid flow diverter has a valve system with two side-by-side poppet valves that are actuated by an eccentric mechanical drive assembly having a variable speed (or variable frequency) motor, a gear reducer, and a single drive shaft. In an alternate configuration of the valve system, the eccentric mechanical drive assembly controls two sets of butterfly valves.

Both fluid flow diverter configurations disclosed in <CIT> are effective and have been used in many RTOs. However, these fluid flow diverters have distinctive drawbacks. The first fundamental drawback is the complexity of the valve system. Additionally, the valve seals in these valve systems have a tendency to leak over time for a variety of reasons.

<CIT> describes a multiport fluid flow control valve for use in regenerative incinerators, which includes a structure to provide a pressure differential within the valve to preclude leakage of emissions from one part of the valve to another.

<CIT> describes a four-port flow diverter for a regenerative thermal oxidizer.

<CIT> describes a unitary diverter/bypass valve.

In view of the foregoing, an improved fluid flow diverter is needed. In particular, what is needed is a fluid flow diverter that overcome these drawbacks while maintaining the use of an eccentric mechanical drive assembly.

The invention provides a fluid flow diverter according to claim <NUM> that includes a diverter body having four ports, a rotating plenum located within the diverter body, and a purge fluid assembly that supplies a purge fluid to the rotating plenum. The rotating plenum has a first stop position that defines a first fluid flow path through the diverter, and a second stop position that defines a second fluid flow path through the diverter. Each of the fluid flow paths define first and second fluid streams. In the first fluid flow path, the first fluid stream goes between the first port and the second port, and the second fluid stream goes between the fourth port and the third port. In the second flow path, the first fluid stream goes between the first port and the third port, and the second fluid stream goes between the fourth port and the second port. The purge fluid supplied to the rotating plenum creates a positive pressure fluid barrier that prevents or minimizes cross-contamination of the first and second fluid streams in the first and second fluid flow paths.

The invention also provides a regenerative thermal oxidizer that includes a combustion chamber first and second heat exchangers in flow communication with the combustion chamber, and the fluid flow diverter according to claim <NUM> in flow communication with the first and second heat exchangers.

Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention being defined by the claims.

As required, embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples and that the systems and methods described below can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present subject matter in virtually any appropriately detailed structure and function. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the concepts.

Embodiments of the present invention provide an improved fluid flow diverter. The improved fluid flow diverter rapidly changes the flow of fluids while introducing a purge fluid between the fluid streams in order to minimize or prevent leakage between the flow paths. The improved fluid flow diverter is simple with a single diverter, a single motor, and a single rotating plenum instead of poppet or butterfly valves. This makes the device durable, reliable, and easy to construct and maintain.

<FIG> show a regenerative thermal oxidizer (RTO) with a fluid flow diverter in accordance with an embodiment of the present disclosure. The RTO <NUM> has a common combustion chamber <NUM> in flow communication with first and second heat exchangers <NUM> and <NUM>. Each of the heat exchangers <NUM> and <NUM> is a chamber housing a heat exchange media such as ceramic saddles or porous ceramic monoliths. A four-port fluid flow diverter <NUM> is also in flow communication with the first and second heat exchangers <NUM> and <NUM>.

In particular, the fluid flow diverter <NUM> has a first (inlet) port <NUM> that receives the industrial process effluent gases via a first transfer duct <NUM>, and a fourth (outlet) port <NUM> that is connected to an exhaust stack <NUM> via a fourth transfer duct <NUM>. A second port <NUM> of the diverter <NUM> is connected through a second transfer duct <NUM> to one end of the first heat exchanger <NUM>, and third port <NUM> of the diverter <NUM> is connected through a third transfer duct <NUM> to one end of the second heat exchanger <NUM>. The opposite ends of first and second heat exchangers <NUM> and <NUM> are connected to the combustion chamber <NUM>, which is equipped with a burner <NUM>.

The diverter <NUM> defines several fluid flow passages through which gases flow as directed by the position of a rotating plenum <NUM> within the diverter. When the plenum <NUM> is in a first stop position as shown in <FIG>, the inlet port <NUM> is in communication with the second port <NUM>, and the outlet port <NUM> is in communication with the third port <NUM>. Thus, the process gases from the process stream follow a first flow path through the diverter <NUM> that enters at the inlet port <NUM> and exits at the second port <NUM>. The gases then pass through the first heat exchanger <NUM>, into the combustion chamber <NUM>, and out through the second heat exchanger <NUM>.

Next, the gases follow a second flow path through the diverter <NUM> that goes from the third port <NUM> to the outlet port <NUM>. The gases exiting the outlet port <NUM> are sent to the exhaust stack <NUM>. With this flow, the process gases are heated in the first heat exchanger <NUM> (whose media was heated in the previous cycle) before entering the combustion chamber <NUM>. And the hot gases exiting the combustion chamber <NUM> transfer heat to the heat exchange media of the second heat exchanger <NUM>.

After a predetermined time, the plenum <NUM> is rotated <NUM>° into a second stop position as shown in <FIG>. In this position, the inlet port <NUM> is in communication with the third port <NUM>, and the outlet port <NUM> is in communication with the second port <NUM>. Thus, the process gases from the process stream follow a third flow path through the diverter <NUM> that enters at the inlet port <NUM> and exits at the third port <NUM>. The gases then pass through the second heat exchanger <NUM>, into the combustion chamber <NUM>, and out through the first heat exchanger <NUM>. Next, the gases follow a fourth flow path through the diverter <NUM> that goes from the second port <NUM> to the outlet port <NUM>. The gases exiting the outlet port <NUM> are sent to the exhaust stack <NUM>. With this flow, the process gases are heated in the second heat exchanger <NUM> before entering the combustion chamber <NUM>, and then the hot gases exiting the combustion chamber <NUM> transfer heat to the heat exchange media of the first heat exchanger <NUM>.

The fluid flow diverter <NUM> is formed of a box-shaped diverter assembly, a drive motor and controller assembly, and a purge fluid assembly. The diverter assembly physically routes the flow of fluids through the diverter. The drive motor and controller assembly actuates the diverter assembly to reroute the fluid flow at predetermined timings in a cycle. The purge fluid assembly provides clean purge fluid to the diverter assembly to create a positive pressure fluid barrier that prevents cross-contamination of the fluid streams.

<FIG> illustrates a fluid flow diverter according to one embodiment of the present disclosure. The diverter assembly portion of this diverter <NUM> includes a square diverter body <NUM> and a rotating fluid flow diverter plenum <NUM>. The diverter body <NUM> generally has a box (e.g., cube) shape with a solid top and bottom, and four sides that each have an opening that forms one of the ports. The plenum <NUM> is connected to and rotates about a single drive shaft <NUM> that passes through apertures in the centers of the top and bottom surfaces of the diverter body <NUM>. The bottom extension of the drive shaft is retained by an external guide bearing.

The plenum <NUM> is formed as a hollow rectangular box (e.g., rectangular cuboid) that fits within the diverter body <NUM>. The height of the plenum <NUM> substantially matches the interior height of the diverter body <NUM> and the width of the plenum substantially matches the distance between diagonally opposite rounded vertical corners of the diverter body <NUM> (with allowances for clearance). The plenum <NUM> makes clearance contact between the top and bottom of the diverter body <NUM>, and also with the four rounded vertical corners of the diverter body <NUM>. Enough clearance is provided between the walls and corners of the diverter body and plenum to allow for thermal expansion of the diverter body-plenum interface. In some embodiments, the outside edges of the plenum <NUM> are lined with high operating temperature seals that are made of a material that is capable of handling the process temperature (i.e., seals suitable for the process flow application). For example, the outside edges where the plenum <NUM> makes clearance of the communicating surfaces of the diverter body <NUM> can be lined with high operating temperature brush seals or high operating temperature flexible material, such as RTV silicone seals, flexible metal wiper seals, or tadpole gaskets. These seals help prevent cross-contamination of the fluid streams.

The drive motor and controller assembly includes an electric motor <NUM>, a gear reducer <NUM>, control components <NUM>, and a variable speed drive controller <NUM>. The motor <NUM> is a three-phase variable frequency braking motor that turns the drive shaft <NUM> via the gear reducer <NUM>, which is connected to the top extension of the drive shaft <NUM>. The gear reducer <NUM> steps down the motor speed and also prevents the drive shaft <NUM> from reversing or coasting beyond top or bottom dead center. The control components <NUM> (e.g., proximity switches) are located on the drive shaft <NUM> and provide position information to the variable speed drive controller <NUM>. The drive controller <NUM> regulates the speed of the motor <NUM> to control the rotation speed, along with the acceleration and deceleration, of the drive shaft.

The drive motor and controller assembly provides a rapid change of position and precise stopping point for the drive shaft. In particular, the rotation of the drive shaft <NUM> is controlled by the drive controller <NUM> such that the plenum <NUM> controllably rotates within the diverter body <NUM> through the motion generated by the motor <NUM>. The plenum <NUM> is made to repeatedly rotate <NUM>° in the same direction in timed increments, so as to repeatedly switch between the two fluid flow patterns. In this exemplary embodiment, a timing command from the drive controller <NUM> starts the motor <NUM> to initiate rotation of the drive shaft <NUM> via the gear reducer <NUM>. The drive shaft <NUM> accelerates to a predetermined speed and then, after predetermined rotation, the control components are triggered to start deceleration. The drive controller <NUM> stops the drive shaft <NUM> when the plenum has rotated the full <NUM>° to its next predetermined stop position. In one embodiment, an internal motor encoder pulse counter controls total movement so as to place the stop position of the drive shaft exactly <NUM>° past the previous stop position.

The acceleration and deceleration of the drive shaft <NUM> is controlled by the drive controller <NUM> (via a variable speed regulator associated with the motor) to slow the plenum as it nears the stop position in this exemplary embodiment. As an example, if the proximity switch is set to set to trigger deceleration at <NUM>° rotation of the drive shaft, and the variable speed drive controller <NUM> is set at a rotation speed of ½ rps, an acceleration rate of <NUM> seconds, and a deceleration rate of <NUM> seconds, then the drive shaft <NUM> will accelerate up to one rps in <NUM> seconds, trigger at <NUM>°, and then decelerate for <NUM> seconds. This produces a bell curve time speed relationship in which the drive shaft <NUM> (and thus the plenum) moves through the full <NUM>° rotation to the next stop position in ½ second, with a velocity of zero at the beginning and end of travel. In other embodiments, the plenum rotates in <NUM>° increments in less than ½ second.

In this exemplary embodiment, the purge fluid assembly includes a purge fluid propelling device <NUM> (e.g., a high pressure fan or blower), first solenoid and valve <NUM> and <NUM>, and second solenoid and valve <NUM> and <NUM>. First and second purge fluid input ports <NUM> and <NUM> are located on the top and bottom of the diverter body <NUM>. These purge fluid input ports are aligned in a diagonal arrangement from corner to corner on the top and bottom of the body so as to form an X-shaped pattern. The valves within the closed passageways, under control of the solenoids, direct the purge fluid to the purge fluid input ports that align with the current stop point of the plenum.

The fan <NUM> supplies the purge fluid (e.g., air) to the plenum <NUM> through two distinctive paths. The first purge fluid path goes through the first valve <NUM>, into a first closed passageway <NUM>, and then through the first purge fluid input ports <NUM>. The second purge fluid path goes through the second valve <NUM>, into a second closed passageway <NUM>, and then through the second purge fluid input ports <NUM>. The drive controller <NUM> controls the solenoids <NUM> and <NUM> so that the corresponding valves <NUM> and <NUM> direct the flow of the purge fluid through the desired closed passageway to the connected input ports. Each of the distinctive purge fluid paths is selectively activated to coincide with one of the diagonal stop positions of the plenum, so that the purge fluid enters the plenum through the input ports on the diagonal that currently aligns with the plenum.

The exterior of the plenum <NUM> is generally solid with holes on its upper and lower faces to allow purge fluid from the input ports to enter the interior of the plenum. There are also holes on the narrow vertical faces of the plenum <NUM> so that the purge fluid in the interior of the plenum creates a positive pressure "fluid barrier". This positive pressure minimizes or prevents cross-contamination of the two streams of gases passing through the diverter.

<FIG> illustrate the operation of the fluid flow diverter of <FIG>. When the plenum <NUM> is in the first stop position (i.e., <NUM>° or <NUM>°) shown in <FIG>, the contaminated industrial process gases introduced into the first port <NUM> are diverted by the plenum <NUM> to the second port <NUM> that is connected to the first heat exchanger <NUM>. At the same time, combusted gases from the second heat exchanger <NUM> entering the third port <NUM> are diverted by the plenum <NUM> to the fourth port <NUM>. Further, high pressure clean purge fluid (e.g., air) from the fan <NUM> is introduced through the first valve <NUM> to the first purge fluid inlet ports <NUM> located on the top and bottom of the diverter body. In this first stop position, one side of the holes in the X pattern on the top and bottom of the diverter body align with the top and bottom of the plenum <NUM>. Thus, the purge fluid is forced into the interior of the hollow plenum <NUM> (through the holes in its top and bottom).

After a predetermined time, the plenum <NUM> rotates (indexes) <NUM>° to the second stop position (i.e., <NUM>° or <NUM>°) shown in <FIG>. In this position, the contaminated industrial process gases introduced into the first port <NUM> are diverted by the plenum <NUM> to the third port <NUM> that is connected to the second heat exchanger <NUM>. At the same time, combusted gases from the first heat exchanger <NUM> entering the second port <NUM> are diverted by the plenum <NUM> to the fourth port <NUM>. Further, high pressure clean purge fluid from the fan <NUM> is introduced through the second valve <NUM> to the second purge fluid inlet ports <NUM> located on the top and bottom of the diverter body. In this second stop position, the other side of the holes in the X pattern on the top and bottom of the diverter body align with the top and bottom of the plenum <NUM>. Thus, the purge fluid is again forced into the interior of the hollow plenum <NUM> (through the holes in its top and bottom).

In this exemplary embodiment, the purge fluid enters the plenum only when the plenum is in one of the stop positions so as to be aligned with the holes in the top and bottom of the diverter body. The purge fluid flow to these holes is controlled by the independent solenoids <NUM> and <NUM>, which are each activated when the drive controller determines that the plenum has reached a stop position corresponding to the set of holes associated with that solenoid.

The purge fluid introduced into the interior of the hollow plenum pressurizes it with sufficient pressure to overcome the system pressure. Therefore, the clean purge fluid exits the narrow vertical sides of the plenum and is forced out between each edge of the plenum and the corresponding sidewall of the diverter body. Because the pressure of the purge fluid escaping the plenum edges is greater the system pressure, any process gases trying to bypass the rotating plenum will be displaced by the high-pressure clean purge fluid. Thus, such leakage will be forced back upstream of the diverter. The introduction of the high-pressure purge fluid between the fluid streams minimizes or prevents leakage between the flow paths. In other words, the flow through each of the four ports of the diverter is kept separated by way of a high-pressure purge fluid curtain to ensure zero (or at least minimal) leakage of process contaminants from the inlet to the outlet of the system.

As shown in <FIG>, the rotating plenum <NUM> of this exemplary embodiment is formed by two steel plates <NUM> and <NUM> that are connected together by bolts that each pass through a spacer <NUM>. This creates the hollow rectangular cuboid shape of the rotating plenum. Optionally, the top and bottom of the rotating plenum <NUM> are closed by additional plates (e.g., steel) having a series of holes for receiving the purge fluid. In some embodiments, the narrow vertical faces of the plenum <NUM> (i.e., between the ends of the steel plates) are closed by additional plates (e.g., steel) having holes for expelling the purge fluid. In other embodiments, the narrow vertical faces of the plenum <NUM> are left completely open. Bristled brush seals <NUM> are attached to the outside of the perimeter edges of the rotating plenum <NUM>. Additionally, the four diagonal corners <NUM> of the diverter body <NUM> are rounded to the swing diameter of the rotating plenum <NUM> plus a clearance gap that allows for both plenum and diverter wall expansion. The bristled brush seals <NUM> make contact with the rounded corners <NUM> to generate an air seal baffle. This type of seal is totally flexible so as to compress when making contact with the rounded corners.

<FIG> shows a fluid flow diverter according to another embodiment of the present disclosure. In this alternative embodiment, exterior plenums on the top and bottom of the diverter body facilitate the introduction of the purge fluid into the rotating plenum. In particular, a closed passageway <NUM> connects the purge fluid propelling device <NUM> to an upper exterior plenum <NUM> attached to the top of the diverter body <NUM>, and another closed passageway <NUM> connects the purge fluid propelling device <NUM> to a lower exterior plenum <NUM> attached to the bottom of the diverter body <NUM>. The drive shaft <NUM> passes through the upper and lower exterior plenums <NUM> and <NUM> and is closed at both ends. The portion of the drive shaft <NUM> located within the exterior and rotating plenums is hollow and perforated.

During operation, the purge fluid propelling device <NUM> supplies a constant flow of purge fluid to the upper and lower exterior plenums <NUM> and <NUM>. The interior of the hollow, perforated drive shaft <NUM> receives the pressurized purge fluid from the upper and lower exterior plenums <NUM> and <NUM>. The pressurized purge fluid in the interior of the drive shaft is then expelled into the interior of the rotating plenum <NUM>. This purge fluid is dispersed throughout the rotating plenum <NUM> and escapes all perimeter edges, so as to create a fluid seal barrier on the perimeter of the rotating plenum (i.e., between the rotating plenum edge and the diverter body).

In another alternative embodiment, expanded apertures on the top and bottom of the diverter body facilitate the introduction of the purge fluid into the rotating plenum. In particular, the closed passageways <NUM> and <NUM> connect the purge fluid propelling device <NUM> to the upper and lower exterior plenums <NUM> and <NUM>. Each of the exterior plenums <NUM> and <NUM> covers an enlarged annular aperture where the drive shaft <NUM> passes through the diverter body <NUM>. The expanded aperture is greater in diameter than the drive shaft <NUM>. Thus, the pressurized purge fluid entering the upper and lower exterior plenums <NUM> and <NUM> is forced through the enlarged apertures in the diverter body <NUM>, along the drive shaft <NUM>, and into the rotating plenum <NUM>. These expanded apertures can be used with a solid drive shaft or a hollow, perforated drive shaft.

In these alternative embodiments, the solenoids and valves are not needed because the flow of the purge fluid is constant and does not require redirection. This supplies a constant fluid barrier at the communicating edges between the rotating plenum and the diverter body. In yet another embodiment, the hollow, perforated drive shaft and/or expanded apertures are added to the embodiment of <FIG> to augment the flow of the purge fluid through the purge fluid input ports.

Accordingly, embodiments of the present invention provide an improved fluid flow diverter. The improved fluid flow diverter provides four ports with two distinct flow patterns. The sealed diverter is purged with a positive pressure purge fluid and therefore does not require valve seals to prevent (or minimize) bypass leakage from the inlet port to the outlet port. The diverter has one electrically driven moving part that rotates in the same direction in <NUM>° increments to generate the two distinct flow patterns. The diverter is easy to construct and maintain, compact by comparison to other diverters that achieve a similar effect, and most importantly prevents or minimizes cross-contamination of fluid streams.

The improved fluid flow diverter is particularly suited for use in a two-chamber RTO, which requires fast flow reversal between two distinct flow patterns to achieve regenerative heat exchange. The diverter can be used in such an RTO to quickly reverse the flow of process gasses through the heat exchangers with minimal cross-contamination. Each reversal of the flow pattern through the RTO is accomplished by only a <NUM>° rotation of one moving part (a rotating plenum). The plenum can rotate the <NUM>° in less than ½ second. The positive pressure purge fluid and quick flow reversal minimize contaminant bypass leakage.

While the improved fluid flow diverter is particularly suited for use in an RTO, the present disclosure is not so limited and can be used in other systems that require cyclical rerouting of fluid flow with minimal cross contamination of the fluid streams.

The terms "a" or "an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms "including" and "having," as used herein, are defined as comprising (i.e., open language). The term "coupled," as used herein, is defined as "connected," although not necessarily directly, and not necessarily mechanically.

Claim 1:
A fluid flow diverter (<NUM>) comprising:
a diverter body (<NUM>) comprising a first port (<NUM>) , a second port (<NUM>), a third port (<NUM>), and a fourth port (<NUM>);
a rotating plenum (<NUM>) located within the diverter body (<NUM>), the rotating plenum (<NUM>) having a first stop position that defines a first fluid flow path through the diverter (<NUM>) and a second stop position that defines a second fluid flow path through the diverter (<NUM>), each of the fluid flow paths defining first and second fluid streams;
a motor (<NUM>) that repeatedly rotates the plenum (<NUM>) <NUM>° in the same direction in timed increments, so as to repeatedly switch between the first and second fluid flow paths; and
a purge fluid assembly configured to supply a purge fluid to the rotating plenum (<NUM>),
wherein in the first fluid flow path, the first fluid stream goes between the first port (<NUM>) and the second port (<NUM>), and the second fluid stream goes between the fourth port (<NUM>) and the third port (<NUM>),
in the second flow path, the first fluid stream goes between the first port (<NUM>) and the third port (<NUM>), and the second fluid stream goes between the fourth port (<NUM>) and the second port (<NUM>), and
the purge fluid supplied to the rotating plenum (<NUM>) creates a positive pressure fluid barrier that prevents or minimizes cross-contamination of the first and second fluid streams in the first and second fluid flow paths.