Patent Application
20220397270
The present inventive concept relates to a regenerative thermal oxidizer with chamber flushing, which utilizes a three, or more heat recovery chamber system. Airflow is directed with poppet style valves.
Regenerative Thermal Oxidizers (RTOs) are a commonly used anti-pollution device used to clean contaminated air. There are a wide variety of RTO designs (for example see U.S. Pat. Nos. 5,540,584 and 5,262,131, both of which are incorporated by reference herein in their entireties), most of which are customized for a specific purpose. The basic premise is that polluted air is introduced into an RTO in order to be heated to a level sufficient to cause the pollutants to decay or oxidize into carbon dioxide and water, which are far less harmful to human health and the environment than the pollutants themselves would be. The cleaned air may then be cooled before being released back into the environment. In most developed countries, including the U.S., the use of RTOs are required in order to comply with limits set forth in the anti-pollution statutes of each jurisdiction.
RTOs function by directing airflow in a first direction through various types of heat exchange media, which are typically ceramic or a similar material. In a first heat exchange chamber, the polluted air, also referred to a process gas, which can be at any initial temperature of 75-850 degrees Fahrenheit, is heated by the first heat exchange chamber to temperatures of approximately 1450 to 1950 degrees Fahrenheit before passing into a combustion chamber. In the combustion chamber, the heated process gas is mixed with natural gas and combusted, thus destroying most of the pollutants in the process gas via oxidation. The cleaned process gas then passes through a second heat exchange chamber wherein it is cooled from approximately 1950 degrees to temperatures slightly higher than the incoming process gas, before being released as exhaust into the atmosphere. In so doing, the first heat exchange chamber is cooled while the second heat exchange chamber is heated. For this reason, a functioning RTO must periodically reverse the flow of the process gas to ensure that it is heated before reaching the combustion chamber and the treated process gas is cooled after leaving the combustion chamber.
One of the typical features of an RTO is that the flow of the process gas can be reversed, often in cycles lasting sixty seconds to four minutes in duration wherein the first heat exchange chamber can be used for heating the processed air in a first cycle and cooling it in a second cycle while the second heat exchange chamber correspondingly cools the processed air in the first cycle and heats the processed gas in the second cycle. In fact, the heating of the processed gas, which occurs in the first heat exchange chamber in the first cycle, is possible because the first heat exchange chamber was previously heated by passing the combusted processed air through it to cool it during the second cycle. Of course, the same is true of the second heat exchange chamber, which is heated and cooled at opposite times of the first heat exchange chamber.
Control of airflow through RTOs is typically performed by using poppet valves or similar devices. Poppet valves have existed for many decades and are typically a disc-shaped blade mounted on the end of a movable shaft. (The valves used to control airflow in internal combustion engines are variations of the poppet valve.) The disc-shaped blade should be of a suitable size and shape to overlap a seat surrounding a port through which air passes in or out of the valve. When the disc-shaped blade is firmly against the seat, with proper seating force, air is not allowed to flow through the port and when the blade (the blade is also referred to as the disc herein) is not against the seat, and no seating force is applied, air is allowed to flow through the port. The seating force required to seal the port with the plug can be between 100 and 5000 or more pounds of pressure. In RTO's these poppet valves can be quite large, measuring in circumference up to seventy-two (72) inches or more.
The basic design of a regenerative thermal oxidizer (“RTO”) 100 is illustrated in
During the cycle described above, the first set of heat exchange media 114 in the first chamber 104 can be cooled by the untreated process gas 101 as it flows through the first chamber 104. Likewise, the second set of heat exchange media 115 in the second chamber 107 can be heated by the treated process gas 101, which has just been combusted, as it flows through the outlet chamber 107. Therefore, it is necessary to periodically reverse the flow of the process gas 101 through the RTO 100 such that process gas 101 is heated before it enters the combustion chamber 105 and cooled after it leaves the combustion chamber 105. This cycling can be made possible by the first manifold poppet valve 103 and the second manifold poppet valve 109, which can open and close in concert to reverse the flow of process gas 101 through the RTO 100. Such cycle is repeated continuously (e.g., each valve remains in a same position for a predetermined period of time, then both valves reverse their position simultaneously, then remain in that position for the predetermined of time, then both valves reverse their position, and so on.)
It is an aspect of the present device to provide an improved regenerative thermal oxidizer.
These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
Further features and advantages of the present device, as well as the structure and operation of various embodiments of the present device, will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
The present inventive concept relates to a regenerative thermal oxidizer which utilizes three chambers or more. While two of the chambers are being used for gas processing, the third chamber can be in a “purge” mode which flushes (evacuates) the volume of process gas which has not entered the combustion chamber. As a consequence, such an RTO can have higher destruction efficiency as the three chambers are purged in a continuous sequence. Each chamber is associated with two poppet valves, one that provides sealing and prevention of cross contamination and the second poppet valve directs flow to different chambers. These two poppet valves are controlled by a computer to implement different flow sequences which operate the three chamber RTO which utilizes a purge mode.
Table I below shows the steps for each of the valve sequence. The valve sequences would switch from the first valve sequence to the second valve sequence to the third valve sequence and then the cycle repeats itself indefinitely (i.e., from the third valve sequence the RTO would switch back to the first valve sequence, then to the second valve sequence then to the third valve sequence, and then back to the first valve sequence, etc.)
Note that the three chamber RTO depicted in
Note that a valve configuration for the first chamber 010 has a first (left) poppet valve 0010-A and second (right) poppet valve 0010-B. Each of the poppet valves can open and close in order to define which mode the valve configuration (and hence its associated chamber) will be in. In
Note that a valve configuration for the second chamber 020 has a first (left) poppet valve 0020-A and second (right) poppet valve 0020-B. Each of the poppet valves can open and close in order to define which mode the valve configuration (and hence its associated chamber) will be in. In
Note that a valve configuration for the third chamber 030 has a first (left) poppet valve 0030-A and second (right) poppet valve 0030-B. Each of the poppet valves can open and close in order to define which mode the valve configuration (and hence its associated chamber) will be in. In
Note that each valve configuration has two valves (typically poppet valves although other types of valves can be used) each of which can be independent opened (extended) or closed (retracted). The position of the combined two poppet valves would dictate the flow of gas into or out from the respective chamber connected to the valve configuration. In the purge mode the gas in the chamber has no exit but through a separate purge valve which can be opened (allowing exit of the gas in the chamber) or closed (no exit for the gas in the chamber). When the purge valve is opened, then the gas from the chamber can exit the chamber through the purge valve and flow according to the current available path.
Each sequence has one chamber in outlet mode, one chamber in inlet mode, and one chamber in purge mode. The purge mode is used to flush out (clean) the chamber. While one chamber is in the purge mode, the other two chambers are operating (one in inlet mode and one in outlet mode) so that operation of the RTO does not have to cease. A purge manifold is a pathway connected to all three chambers and is used to flush out the gas in the chamber in the purge mode. Each chamber has a purge valve which when closed, prevents the gas in the respective chamber from exiting to the purge manifold, and when open, allows the gas to enter into the purge manifold where it can then flow according to the path of the purge manifold.
Note that the three chamber RTO depicted in
Note that the three chamber RTO depicted in
Please note that Table II illustrates an alternative sequence of valve positions, alternative to Table I:
Thus, in this embodiment (and as shown in
In
In
As an alternative to
In
In operation 801, the valves in the RTO are positioned in the first sequence described herein.
From operation 801, the method proceeds to operation 802, in which the valves in the RTO are positioned to the second sequence described herein.
From operation 802, the method proceeds to operation 803, in which the valves in the RTO are positioned to the third sequence described herein.
From operation 803, the progression can return to operation 801 wherein the valves in the RTO are positioned back to the first sequence and the progression continues.
Note that
Each of the three sequences can last for a duration of 10 seconds to 5 minutes (or any other time) before the progression proceeds to the next step. The sequence is conducted automatically and a digital computer can control the position of each of the valves in accordance with the current sequence. Note that in the alternative, instead of the order shown in
Note that there are four purge modes: Recirculation of the flushing volume back to the inlet of the RTO system, use of recirculated stack air to flush the process gasses into the combustion chamber, Use of outside air to flush process gases into the combustion chamber and use of a separate (combustion blower) fan to recirculate the process gases to the combustion chamber or to be used as burner combustion air. Mode of force for the four modes is supported with either a forced draft or induced draft main RTO fan orientation
Note that the purge manifold in the combustion blower purge mode connects all three chambers (each chamber has its purge valve possibly preventing flow to the purge manifold depending on the position of the respective purge valve). The purged gas from the chamber in the purge mode is extracted through the purge manifold (when the respective purge valve is opened) and then directed via one or more combustion air blowers into the combustion chamber where it is then processed through the burner. The purge manifold (from the three chambers) leads through one or more combustion air blowers into the combustion chamber.
Note that in the untreated process purge mode (
An electronic and/or mechanical system can be utilized to control the operation of the valves (e.g., opening, closing, etc.) sot that each of the valve sequences can be implements. A computer can implement a timer and memory such that when the time for a particular valve sequence has ended, it would change the position of the necessary valves (e.g., open closed valves, close open valves, etc.) to implement the new sequence.
A processing unit 1801 can be a microprocessor and any associated hardware (power supply, cache, etc.). The processing unit 1801 can also be an off the shelf computer. The processing unit 1801 is connected to an input/output device(s) 1803, which can be a keyboard (input device), LCD (output device), etc. The input/input devices 1803 would allow a person to communicate with the computer to program it and enable it to conduct any operations. The processing unit 1801 can also be connected to a ROM/RAM 1804 and also a storage device 1805 (e.g., a hard disk drive, flash memory, etc.). The processing unit 1801 can also be connected to a valve controller 1802 which is an interface which communicates with each valve and enables individual control of each of the valves used in the RTO, so that the processing unit 1801 can open/close individual valves according to a program, etc. The storage device 1805 can store a computer program which, when executed, would instruct the processing unit 1801 to automatically control the RTO to implement all of the progressions and valve sequences herein. The input/output devices 1803 can be used to interrupt a program (when necessary) to suspend (or turn off) the RTO automatic operations.
The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
