US20090142717A1 - Metering combustion control - Google Patents

Metering combustion control Download PDF

Info

Publication number
US20090142717A1
US20090142717A1 US11/999,103 US99910307A US2009142717A1 US 20090142717 A1 US20090142717 A1 US 20090142717A1 US 99910307 A US99910307 A US 99910307A US 2009142717 A1 US2009142717 A1 US 2009142717A1
Authority
US
United States
Prior art keywords
combustion air
air flow
combustion
firing rate
fuel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US11/999,103
Inventor
Peter Lavelle
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Preferred Utilities Manufacturing Corp
Original Assignee
Preferred Utilities Manufacturing Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Preferred Utilities Manufacturing Corp filed Critical Preferred Utilities Manufacturing Corp
Priority to US11/999,103 priority Critical patent/US20090142717A1/en
Assigned to PREFERRED UTILITIES MANUFACTURING CORPORATION reassignment PREFERRED UTILITIES MANUFACTURING CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LAVELLE, PETER
Publication of US20090142717A1 publication Critical patent/US20090142717A1/en
Application status is Abandoned legal-status Critical

Links

Images

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23NREGULATING OR CONTROLLING COMBUSTION
    • F23N1/00Regulating fuel supply
    • F23N1/02Regulating fuel supply conjointly with air supply
    • F23N1/022Regulating fuel supply conjointly with air supply using electronic means
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23NREGULATING OR CONTROLLING COMBUSTION
    • F23N5/00Systems for controlling combustion
    • F23N5/003Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F23N5/006Systems for controlling combustion using detectors sensitive to combustion gas properties the detector being sensitive to oxygen
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23NREGULATING OR CONTROLLING COMBUSTION
    • F23N2023/00Signal processing; Details thereof
    • F23N2023/36PID signal processing
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23NREGULATING OR CONTROLLING COMBUSTION
    • F23N2041/00Applications
    • F23N2041/04Heating water
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23NREGULATING OR CONTROLLING COMBUSTION
    • F23N2041/00Applications
    • F23N2041/10Generating vapour

Abstract

Metering combustion control in a fired equipment is disclosed in which both the fuel flow rate and the combustion air flow rate are metered in a desired ratio corresponding to a master firing rate demand, and the master firing rate demand combustion air flow directed to the combustion air regulating element is trimmed in response to an error based correction adjustment determined from the respective values of the fuel flow meter and combustion air flow meter input signals to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand.

Description

    FIELD OF THE INVENTION
  • The present invention relates generally to combustion control for use in fired equipment and deals more particularly with a metering combustion control for fired equipment.
  • BACKGROUND OF THE INVENTION
  • Combustion control strategies applied to fired equipment, both commercial and industrial, generally are one of three general category types or some subtle variation to one or the other of them. The control strategies as known to a person skilled in the art are: 1) single point positioning control also known as jackshaft positioning; 2) parallel positioning control; and 3) metered cross-limited control.
  • Each of these are fuel/air ratio combustion control strategies wherein a firing rate demand signal generated as a result of an attempt to maintain a selected “process variable” (PV) equal to a desired “set-point” (SP) is simultaneously directed to a fuel flow regulating element and a combustion air flow regulating element.
  • The currently known and implemented combustion control strategies are not entirely satisfactory. To applicant's knowledge, none of the known combustion control strategies meet Underwood Laboratories (UL) approval as a parameter based combustion control instrument capable of carrying out a metering fuel/air ratio combustion control strategy.
  • The currently known and implemented metered cross-limited combustion control strategies are not entirely satisfactory. Current implementations utilize two, or more, PID (Proportional-Integral-Derivative) control logic blocks, one for fuel and one for air. Cross-limiting logic must be applied to coordinate the two independent proportional integral derivative logics. This combination requires considerable skill to tune and calibrate, and results in a slow firing rate demand response time.
  • Accordingly what is needed is a parameter based combustion control instrument capable of choosing via parameter selection a selected one of a single point positioning control strategy, a parallel positioning control strategy and a metering fuel/air ratio combustion control strategy.
  • SUMMARY OF THE INVENTION
  • In accordance with a broad aspect of some embodiments of the invention, combustion is controlled in a fired equipment by metering both the fuel flow rate and the combustion air flow rate in a desired ratio corresponding to a master firing rate demand, and by trimming the master firing rate demand directed to the combustion air regulating element in response to an error based correction adjustment determined from the respective values of the fuel flow meter and combustion air flow meter input signals to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand
  • BRIEF DESCRIPTION OF DRAWINGS
  • FIG. 1 is a function schematic representation of an example of a parallel positioning combustion control system.
  • FIG. 2 is a functional schematic representation of an example of a parallel positioning combustion control system with oxygen trim.
  • FIG. 3 is a functional schematic representation of an example of a full metering combustion control system with fuel flow and combustion air flow cross limiting.
  • FIG. 4 is a functional schematic representation of an example of a metering combustion control system with oxygen trim according to some embodiments of the present invention.
  • FIG. 5 shows a flowchart of the basic steps of the method according to some embodiments of the invention.
  • FIG. 6 shows a combustion controller enabled device according to some embodiments of the invention for providing combustion control in a fired equipment.
  • FIG. 7 is a functional block diagram of an example of a signal processor for carrying out the invention.
  • FIG. 8 is a functional block diagram of an example of a combustion controller for carrying out the steps of the method according to some embodiments of the invention.
  • FIG. 9 shows a combustion controller chipset according to some embodiments of the invention for providing combustion control in a fired equipment.
  • WRITTEN DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
  • The basic purpose and intent of a combustion control strategy in a fired equipment is to maintain as stated above a process variable equal to a desired set-point by directing a firing rate demand signal to a fuel flow regulating element and a combustion air flow regulating element in the fired equipment. Such fired equipment may be for example, a steam generator, a hot water heater, a boiler, a chemical process heater, a heated manufacturing process, or other boiler combustion fired equipment although the invention is not limited to such fired equipment. For purposes of explanation and by way of example only, consider a steam generator. In this case the process variable is the steam pressure. Under the combustion control strategy, a reduction in the steam pressure relative to the set-point of the desired pressure results in an increase in the master firing rate demand signal with a coincidental call for an increase in the fuel input and combustion air input to the burner to increase the firing rate to produce more steam to drive the pressure upward toward the desired pressure. Likewise, an increase in the steam pressure relative to the set-point results in a decrease in the master firing rate demand signal with a coincidental call for a decrease in the fuel input and combustion air input to decrease the firing rate to produce less steam to drive the pressure downward toward the desired pressure.
  • For further purposes of explanation and by way of a further example, consider a hot water heater. In this case the process variable is hot water temperature. Under the combustion control strategy, a reduction in water temperature relative to the set-point of the desired water temperature results in an increase in the master firing rate demand signal with a coincidental call for an increase in the fuel input and combustion air input to the burner to increase the firing rate to produce hotter water to drive the water temperature upward toward the desired water temperature. Likewise, an increase in the water temperature relative to the set-point results in a decrease in the master firing rate demand signal with a coincidental call for a decrease in the fuel input and combustion air input to decrease the firing rate to lessen the heat input allowing the water temperature to decrease thus driving the water temperature toward the desired water temperature.
  • In both examples, a reduction in the process variable relative to the set-point results in an increase in the master firing rate demand signal (MFDS) with a coincidental call for an increase in fuel and combustion air inputs to the burner of the fired equipment while an increase in the process variable relative to the set-point results in a decrease in the MFDS and the fuel and combustion air inputs.
  • FIG. 1 shows a schematic representation of a combustion controller generally designated 10 in which a parallel positioning control strategy is utilized. Two firing rate demand signals are used in parallel positioning control, with one signal going to the fuel flow regulating element and the other going to the combustion air regulating element, hence the term parallel positioning. For example, a reduction in the process variable relative to the set-point results in an increase in the master firing rate demand signal with a coincidental call for an increase in the fuel input and combustion air input to the fired equipment, whereas an increase in the process variable relative to the set-point results in a decrease in the master firing rate demand signal and as a result a decrease in the fuel input and the combustion air input. As shown in FIG. 1, the master firing rate demand signals are generated or retrieved from a suitably configured module 10 a. The generated output (0 to 100%) is the result of a comparison of the design operating set-point versus the actual process state. The fuel firing rate demand signal is conditioned by a fuel function generator module 10 b and directed to the fuel flow regulating element 10 c. The fuel function generator 10 b characterizes the opening of the fuel flow regulating element to produce a near linear fuel flow as a function of the master firing rate demand signal. The fuel flow regulating element 10 c may be for example, a flow control valve or a metering pump, and is responsive to the fuel firing rate demand signal from the fuel function generator module 10 b to increase or decrease fuel flow. The combustion air firing rate demand signal is conditioned by a combustion air function generator 10 d and directed to the air flow regulating element 10 e. The combustion air function generator 10 d characterizes the opening and/or speed of the air flow regulating element 10 e to produce the desired fuel/air ratio as a function of the master firing rate demand signal. The fuel/air ratio is not a constant and varies due to the need to maintain ideal fuel/air mixing velocity ratios throughout the burner firing rate range. The air flow regulating element 10 e may be for example, a burner or forced draft fan damper and/or a forced draft fan variable frequency drive or a turbine.
  • Another combustion control strategy known as “single point positioning” or “jackshaft positioning” control is a variation of the parallel positioning control strategy in which the flow regulating elements are of a design that is arranged to regulate their respective flows via the action of one or more linkage rods, each of which are connected to a common “jackshaft”. That jackshaft is in turn mechanically linked to a single positioning actuator or servo-motor, which receives the master firing rate demand signal input. In this way only one master firing rate demand signal is directed to the fired equipment and the relative flow regulating characteristics of each flow regulating element, i.e., the fuel flow regulating element and the combustion air flow regulating element, is accomplished by mechanical means, for example, linkage adjustments, or adjustable cam/roller assemblies or both or in other ways well known and understood by those skilled in the art.
  • FIG. 2 shows a schematic representation of a combustion controller generally designated 12 in which a parallel positioning control strategy with oxygen trim is utilized. As explained in connection with the discussion of FIG. 1, two firing rate demand signals are used with the fuel firing rate demand signal going to the fuel flow regulating element and the combustion air firing rate demand signal being trimmed prior to going to the combustion air regulating element. As shown in FIG. 2, the master firing rate demand signals are generated or retrieved from a suitably configured module 12 a. The generated output (0 to 100%) is a result of a comparison of the design operating set-point versus the actual process state. The fuel firing rate demand signal is conditioned by a fuel function generator module 12 b and directed to the fuel flow regulating element 12 c. The fuel function generator 12 b characterizes the opening of the fuel flow regulating element to produce a near linear fuel flow as a function of the master firing rate demand signal. The fuel flow regulating element 12 c may be for example, a flow control valve or a metering pump, and is responsive to the fuel firing rate demand signal from the fuel function generator module 12 b to increase or decrease fuel flow. A flue gas oxygen analyzer module 12 d determines the actual oxygen in the flue gas. An air demand trim computer module 12 e compares the actual oxygen content in the flue gas to a master firing rate demand-based flue gas excess oxygen set-point and adjusts either the master firing rate demand combustion air flow signal input to the controller or the master firing rate demand signal combustion air flow signal directed to the air flow regulating element. Generally, the oxygen trim computation will include limits on the amount of variation that can be enacted to change the master firing rate demand combustion air flow signal because of the concern for possible failure of the flue gas oxygen analyzer. The master firing rate demand combustion air flow signal is conditioned by a combustion air function generator 12 f and directed to the air flow regulating element 12 g. The combustion air function generator 12 f characterizes the opening and/or speed of the air flow regulating element 12 g to produce the desired fuel/air ratio as a function of the master firing rate demand signal. The air flow regulating element 12 g may be for example, a burner or forced draft fan damper and/or a forced draft fan variable frequency drive or a turbine. The fuel/air ratio is not a constant and varies due to the need to maintain ideal fuel/air mixing velocity ratios throughout the burner firing rate range.
  • FIG. 3 shows a schematic representation of a combustion controller generally designated 14 in which a full metering control strategy with fuel flow and combustion air flow cross limiting is utilized. In a traditional full metering combustion control system, the values of the respective input of the actual fuel flow and the combustion air flow are compared to their respective flow set-point in a proportional integral derivative controller. The actual firing rate demand signal for the fuel flow input and the combustion air flow input is then the error correction based output signal from the respective controller. The set-point of each of the fuel flow controller and the combustion air flow controller was originally the master firing rate demand signal. The traditional full metering control strategy differs from the ‘basic’ jackshaft and parallel positioning control strategies (without oxygen trim) in that neither of those strategies has any form of “feedback” pertaining to the actual affect on flow rates resulting from a change in the master firing rate demand signal. The addition of “cross limiting” adds low and high signal selectors and logic to assure that on increases in the firing rate, the air demand would increase before the fuel demand and on decreases in firing rate, the reverse action would be assured.
  • Still referring to FIG. 3, the master firing rate demand signals are generated or retrieved from a suitably configured module 14 a. The generated output (0 to 100%) is a result of a comparison of the design operating set-point versus the actual process state. The fuel flow master firing rate demand signal is input to a low value selector module 14 d along with an actual combustion air flow signal from a combustion air flow transmitter module 14 e to provide a fuel set-point signal that is input to the fuel flow proportional integral derivative controller 14 c along with an actual value of the fuel flow signal from a fuel flow transmitter module 14 b to provide a fuel firing rate demand signal. The fuel firing rate demand signal is conditioned by a fuel function generator module 14 f and is directed to the fuel flow regulating element 14 g. The fuel function generator 14 f characterizes the opening of the fuel flow regulating element to produce a near linear fuel flow as a function of the master firing rate demand signal. The fuel flow regulating element 14 g may be for example, a flow control valve or a metering pump, and is responsive to the fuel firing rate demand signal from the fuel function generator module 14 f to increase or decrease fuel flow. The combustion air flow master firing rate demand signal is input to a high value selector module 14 h along with an actual fuel flow signal from the fuel flow transmitter module 14 b to provide an air flow set-point that is input to the air flow proportional integral derivative controller 14 i along with an actual combustion air flow signal from the combustion air flow transmitter module 14 e to provide a combustion air firing rate demand signal. The combustion air firing rate demand signal is conditioned by a combustion air function generator 14 j and directed to the air flow regulating element 14 k. The combustion air function generator 14 j characterizes the opening and/or speed of the air flow regulating element 14 k to produce the desired fuel/air ratio as a function of the master firing rate demand signal. The air flow regulating element 14 k may be for example, a burner or forced draft fan damper and/or a forced draft fan variable frequency drive or a turbine. The fuel/air ratio is not a constant and varies due to the need to maintain ideal fuel/air mixing velocity ratios throughout the burner firing rate range.
  • Turning now to FIG. 4, a functional schematic representation of an example of a metering combustion control system with oxygen trim according to some embodiments of the present invention is shown therein and generally designated 16. Now in contrast to the combustion control system strategies discussed above, the metering combustion control system strategy with oxygen trim embodying the present invention blends the benefits of all of the above described approaches by using the respective flow meter input signals in combination with the master firing rate demand signals in a proportional integral controller to “trim” the basic parallel positioning master firing rate demand signal being directed to the air flow regulating element. Further, limits are applied to the allowable level of error correction based adjustment so that even if there is a flow meter failure, continued operation in the basic parallel positioning format (with or without oxygen trim) is possible. Ideally the fuel input varies linearly with the master firing rate demand whereas for reasons associated with maintaining optimum mixing influenced velocities, the combustion air level is relatively higher at lower firing rates (i.e. fuel/air ratio is not a constant throughout the range).
  • As shown in FIG. 4, the master firing rate demand signals are generated or retrieved from a suitably configured module 16 a. The generated output (0 to 100%) is a result of a comparison of the design operating set-point versus the actual process state. The firing rate demand signal is applied simultaneously to a fuel function generator 16 b and an air flow demand summing module 16 k. The fuel function generator 16 b characterizes the opening of the fuel flow regulating element 16 c to produce a near linear fuel flow as a function of the master firing rate demand signal. The air flow demand summing module 16 k adds the firing rate demand signal to the air flow proportional integral derivative controller 16 g trim signal and applies the resultant signal to the combustion air function generator 16 i. The combustion air function generator 16 i characterizes the opening and/or speed of the air flow regulating element 16 j to produce the desired fuel/air ratio as a function of the master firing rate demand signal. The fuel/air ratio is not a constant and varies due to the need to maintain ideal fuel/air mixing velocity ratios throughout the burner firing rate range.
  • The fuel flow regulating element 16 c may be for example, a flow control valve or a metering pump, and is responsive to the fuel firing rate demand signal from the fuel function generator module 16 b to increase or decrease fuel flow. The air flow regulating element 16 j may be for example, a burner or forced draft fan damper and/or a forced draft fan variable frequency drive or a turbine.
  • A flue gas oxygen analyzer module 16 d determines the actual oxygen in the flue gas. An air flow trim computer module 16 e receives a signal representative of the value of the actual oxygen in the flue gas along with a signal representative of the combustion air flow from a combustion air flow transmitter module 16 f to provide an adjusted combustion air flow signal in accordance with the required oxygen content in the flue gas. The output signal from the air flow trim computer module 16 e is input to an air flow proportional integral derivative controller module 16 g along with the value of the actual fuel flow from a fuel flow transmitter module 16 h for determining the combustion air flow trim signal to be directed to the air flow demand summing module 16 k.
  • It should be recognized that the turndown capability (i.e. ability to operate at reduced rates) of a burner governed by a traditional metering control strategy is tied to the flow meter's limited turndown capabilities that is, flow measurement accuracy at reduced rates. In contrast according to some embodiments of the present invention, the turndown capabilities are equivalent to that of parallel positioning due to the lack of the absolute dependence on the fuel flow and combustion air flow signals.
  • It should be recognized that according to some embodiments of the present invention, the fuel and air regulating elements (16 c and 16 j) respond instantly to changes in the firing rate demand 16 a. In contrast, traditional metered control strategy low selector 14 d, high selector 14 h and the differing response rates of fuel proportional integral derivative controller 14 c and air flow proportional integral derivative controller 14 i all combine to delay the response of the respective fuel and air regulating elements (16 c and 16 j) to a change in the firing rate demand 16 a.
  • FIG. 5 shows a flowchart of the basic steps of the method for metering combustion control in fired equipment according to some embodiments of the present invention. The basic method is shown in the flowchart generally designated 20 and includes the steps of controlling combustion in a fired equipment, for example a steam boiler or hot water heater by metering both the fuel flow rate and the combustion air flow rate in a desired ratio corresponding to a master firing rate demand (step 20 a), and trimming the master firing rate demand signal directed to the combustion air regulating element in response to an error based correction adjustment determined from the respective values of the fuel flow meter and combustion air flow meter input signals to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand (step 20 b).
  • FIG. 6 shows by way of example a metering combustion control enabled device 22 according to some embodiments of the invention for use in a fired equipment 24 such as described above. The metering combustion control enabled device 22 includes one or more modules 22 a configured for controlling combustion in a fired equipment, for example a boiler or hot water heater, according to a master firing rate demand, one or more modules 22 b configured for metering the fuel flow rate and the combustion air flow rate in a desired ratio to correspond to the master firing rate demand, one or more modules 22 c configured for providing an error based correction adjustment based on the value of the fuel flow meter input signal and the value of the combustion air flow meter input signal, and one or more modules 22 d configured for trimming the master firing rate demand signal value directed to the combustion air flow regulating element in response to the error based correction adjustment to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand. Consistent with that described above, the metering combustion control enabled device may include other modules 22 e that do not necessarily form part of the underlying invention and are not described in detail herein.
  • By way of example, and consistent with that described above, the functionality of the modules 22, 22 a, 22 b 22 c, 22 d and/or 22 e may be implemented using hardware, software, firmware, or a combination thereof, although the scope of the invention is not intended to be limited to any particular embodiment thereof. In a typical software implementation, the modules 22 a, 22 b, 22 c and 22 d would be one or more microprocessors-based architectures having a microprocessor, a random access memory (RAM), a read only memory (ROM), input/output devices, memory, flow meter control, and control, data and address buses connecting the same such as shown in FIG. 7. A person skilled in the art would be able to program such a microprocessor-based implementation to perform the functionality described herein without undue experimentation. The scope of the invention is not intended to be limited to any particular implementation using technology now known or later developed in the future. Moreover, the scope of the invention is intended to include the modules 22 a, 22 b, 22 c and 22 d being a standalone module, as shown, or in the combination with other circuitry for implementing another module. Moreover, the real-time part may be implemented in hardware, while the non-real-time part may be done in software.
  • According to some embodiments the present invention may be implemented as a computer program product comprising a computer readable structure embodying computer program code therein for execution by a computer processor instructions for performing a method comprising controlling combustion in a fired equipment according to a master firing rate demand; metering the fuel flow rate and the combustion air flow rate in a desired ratio to correspond to the master firing rate demand; providing an error based correction adjustment based on the value of the fuel flow meter input signal and the value of the combustion air flow meter input signal, and trimming the master firing rate demand signal value directed to the combustion air flow regulating element in response to the error based correction adjustment to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand.
  • Turning now to FIG. 8, a schematic functional block diagram of an example of a metering combustion control is illustrated therein showing the major operational functional components which may be required to carry out the intended functions of the combustion controller and implement the steps of the method according to some embodiments of the invention and is generally designated 24. A processor such as the signal processor of FIG. 7 carries out the computational and operational control of the metering combustion control in accordance with one or more sets of instructions stored in a memory. A user interface may be used to provide alphanumeric input and control signals or other program steps and set-points by a user and is configured in accordance with the intended function to be carried out. A display sends and receives signals from the controller that controls the graphic and text representations shown on a screen of the display in accordance with the function being carried out. The controller controls a fuel flow meter and an air combustion flow meter that operate in a manner well known to those skilled in the art. The functional logical elements for carrying out the metering combustion control operational functions are suitably interconnected with the controller to carry out the metering combustion control as contemplated in accordance with some embodiments of the invention. An electrical power source such as a battery is suitably interconnected within the combustion controller to carry out the functions described above. It will be recognized by those skilled in the art that the metering combustion control according to some embodiments of the invention may be implemented in other ways other than that shown and described, including using pneumatic control elements and other mechanical and electrical devices. It will also be recognized by those skilled in the art that the metering combustion control strategy for fired equipment according to some embodiments of the invention can be implemented using other suitably configured and arranged devices including but not limited to pneumatic, electronic, microprocessor, computer, signal processor, logic devices, wired logic, firmware, computational and memory components, software instruction sets, and other devices and components now known or future developed.
  • Consistent with that discussed above, the metering combustion control according to some embodiments of the invention may be implemented as a chipset for use in a combustion control enabled fired equipment generally designated 26 for example as illustrated in FIG. 9. The metering combustion control chipset generally designated 26 a is suitably configured for controlling combustion in a fired equipment by metering both the fuel flow rate and the combustion air flow rate in a desired ratio corresponding to a master firing rate demand, and for trimming the master firing rate demand directed to the combustion air regulating element in response to an error based correction adjustment determined from the respective values of the fuel flow meter and combustion air flow meter input signals to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand. Consistent with that described above, the metering combustion control chipset may include other metering combustion chipsets 26 b that do not necessarily form part of the underlying invention and are not described in detail herein.

Claims (19)

1. Method, comprising:
controlling combustion in a fired equipment according to a master firing rate demand;
metering the fuel flow rate and the combustion air flow rate in a desired ratio to correspond to the master firing rate demand;
providing an error based correction adjustment based on the value of the fuel flow meter input signal and the value of the combustion air flow meter input signal, and
trimming the master firing rate demand signal value directed to the combustion air flow regulating element in response to the error based correction adjustment to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand.
2. The method according to claim 1 further comprising the fuel flow input signal and the combustion air flow input signal being input to a proportional integral derivative controller for determining the value of the error based correction adjustment.
3. The method according to claim 1 further comprising limiting in response to the failure of a fuel flow meter and/or an air combustion flow meter, the value of the error correction based adjustment to a predetermined allowable level to insure continued combustion.
4. The method according to claim 1 further comprising providing a turndown capability without dependence on flow meter flow signals.
5. The method according to claim 4 wherein the turndown capability is equivalent to a parallel positioning combustion control operation.
6. The method according to claim 1 further comprising providing a reduced response time capability without dependence on low selectors, high selectors or differences in independent fuel and air flow PID tunings.
7. The method according to claim 1 further comprising controlling the fuel British Thermal Unit (BTU) flow rate and controlling the combustion air oxygen mass flow rate.
8. The method according to claim 1 further comprising analyzing the oxygen level in the flue gas for adjusting the combustion air flow meter input signal.
9. The method according to claim 1 further comprising characterizing the opening of the fuel flow regulating element to produce a near linear fuel flow as a function of the trimmed master firing rate demand signal directed to the fuel flow regulating element.
10. The method according to claim 1 further comprising characterizing the opening/speed of the air flow regulating element to produce the desired fuel flow rate/combustion air flow rate ratio as a function of the trimmed master firing rate demand signal directed to the combustion air flow regulating element.
11. A controller, comprising:
one or more modules configured for controlling combustion in a fired equipment according to a master firing rate demand;
one or more modules configured for metering the fuel flow rate and the combustion air flow rate in a desired ratio to correspond to the master firing rate demand;
one or more modules configured for providing an error based correction adjustment based on the value of the fuel flow meter input signal and the value of the combustion air flow meter input signal, and
one or more modules configured for trimming the master firing rate demand signal value directed to the combustion air flow regulating element in response to the error based correction adjustment to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand.
12. The controller according to claim 11 further comprising one or more modules configured as a proportional integral derivative controller for determining the value of the error based correction adjustment based on the respective values of the fuel flow input signal and the combustion air flow input signal.
13. The controller according to claim 11 wherein said fired equipment is a boiler configured and arranged for generating steam.
14. The controller according to claim 11 wherein said fired equipment is a hot water heater.
15. The controller according to claim 11 wherein said fired equipment is at least one of a steam generator, a boiler, a chemical process heater, a heated manufacturing process, a boiler combustion fired equipment.
16. A computer program product comprising a computer readable structure embodying computer program code therein for execution by a computer processor, said computer program further comprising instructions for performing a method comprising controlling combustion in a fired equipment according to a master firing rate demand; metering the fuel flow rate and the combustion air flow rate in a desired ratio to correspond to the master firing rate demand; providing an error based correction adjustment based on the value of the fuel flow meter input signal and the value of the combustion air flow meter input signal, and trimming the master firing rate demand signal value directed to the combustion air flow regulating element in response to the error based correction adjustment to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand.
17. A method according to claim 1 wherein the method further comprises implementing the steps of the method via a computer program running in a processor, controller or other suitable module located in or interfaced with the fired equipment.
18. A chipset, comprising:
a first chipset module configured for controlling combustion in a fired equipment by metering both the fuel flow rate and the combustion air flow rate in a desired ratio corresponding to a master firing rate demand, and
a second chipset module configured for trimming the master firing rate demand directed to the combustion air regulating element in response to an error based correction adjustment determined from the respective values of the fuel flow meter and combustion air flow meter input signals to drive the ratio between the fuel flow rate and the combustion air flow rate toward the desired ratio for controlling the combustion in accordance with the master firing rate demand.
19. The chipset according to claim 18 further comprising a proportional integral derivative controller configured for determining the value of the error based correction adjustment based on the respective values of the fuel flow input signal and the combustion air flow input signal.
US11/999,103 2007-12-04 2007-12-04 Metering combustion control Abandoned US20090142717A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US11/999,103 US20090142717A1 (en) 2007-12-04 2007-12-04 Metering combustion control

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US11/999,103 US20090142717A1 (en) 2007-12-04 2007-12-04 Metering combustion control

Publications (1)

Publication Number Publication Date
US20090142717A1 true US20090142717A1 (en) 2009-06-04

Family

ID=40676095

Family Applications (1)

Application Number Title Priority Date Filing Date
US11/999,103 Abandoned US20090142717A1 (en) 2007-12-04 2007-12-04 Metering combustion control

Country Status (1)

Country Link
US (1) US20090142717A1 (en)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100062381A1 (en) * 2008-09-11 2010-03-11 Gross Dietrich M Oxy-fuel combustion system with closed loop flame temperature control
US20110212404A1 (en) * 2008-11-25 2011-09-01 Utc Fire & Security Corporation Automated setup process for metered combustion control systems
US20110223548A1 (en) * 2008-11-25 2011-09-15 Utc Fire & Security Corporation Oxygen trim controller tuning during combustion system commissioning
US20110244407A1 (en) * 2010-03-30 2011-10-06 Yamatake Corporation Combustion controlling device
US8437941B2 (en) 2009-05-08 2013-05-07 Gas Turbine Efficiency Sweden Ab Automated tuning of gas turbine combustion systems
US20150045971A1 (en) * 2011-12-15 2015-02-12 Honeywell International Inc. Valve controller configured to estimate fuel comsumption
US9267443B2 (en) 2009-05-08 2016-02-23 Gas Turbine Efficiency Sweden Ab Automated tuning of gas turbine combustion systems
US9354618B2 (en) 2009-05-08 2016-05-31 Gas Turbine Efficiency Sweden Ab Automated tuning of multiple fuel gas turbine combustion systems
US9557059B2 (en) 2011-12-15 2017-01-31 Honeywell International Inc Gas valve with communication link
US9657946B2 (en) 2012-09-15 2017-05-23 Honeywell International Inc. Burner control system
US9671797B2 (en) 2009-05-08 2017-06-06 Gas Turbine Efficiency Sweden Ab Optimization of gas turbine combustion systems low load performance on simple cycle and heat recovery steam generator applications
US9835265B2 (en) 2011-12-15 2017-12-05 Honeywell International Inc. Valve with actuator diagnostics
US9851103B2 (en) 2011-12-15 2017-12-26 Honeywell International Inc. Gas valve with overpressure diagnostics
US9995486B2 (en) 2011-12-15 2018-06-12 Honeywell International Inc. Gas valve with high/low gas pressure detection
US10203049B2 (en) 2014-09-17 2019-02-12 Honeywell International Inc. Gas valve with electronic health monitoring
US10313767B2 (en) 2016-04-07 2019-06-04 Honeywell International Inc. Fuel submetering using firing rate signals
US10422531B2 (en) 2012-09-15 2019-09-24 Honeywell International Inc. System and approach for controlling a combustion chamber

Citations (43)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3049300A (en) * 1960-04-07 1962-08-14 Bailey Meter Co Combustion control for a furnace fired with fuels having different oxygenexcess air characteristics
US3216661A (en) * 1961-10-10 1965-11-09 George K Mckenzie Combustion control apparatus
US3236449A (en) * 1958-03-12 1966-02-22 Sulzer Ag Method and apparatus for controlling fuel and air supplied to a combustion chamber
US3241597A (en) * 1962-12-04 1966-03-22 Sulzer Ag Method of firing with fluid fuels
US3284615A (en) * 1956-09-24 1966-11-08 Burroughs Corp Digital control process and system
US3549089A (en) * 1968-07-26 1970-12-22 Hays Corp Method and means for trimming position control members
US3602487A (en) * 1969-11-10 1971-08-31 Jones & Laughlin Steel Corp Blast furnace stove control
US3616997A (en) * 1968-05-20 1971-11-02 Kockums Mekaniska Verkstads Ab Combustion regulator
US3734675A (en) * 1971-07-13 1973-05-22 Phillips Petroleum Co Burner controlling apparatus and method
US3908897A (en) * 1972-12-21 1975-09-30 Shell Oil Co Off-line integration of bridge and boiler controls
US4097218A (en) * 1976-11-09 1978-06-27 Mobil Oil Corporation Means and method for controlling excess air inflow
US4133629A (en) * 1977-08-02 1979-01-09 Phillips Petroleum Company Combustion system control
US4138725A (en) * 1976-07-30 1979-02-06 Kawasaki Jukogyo Kabushiki Kaisha Automatic fuel combustion control method and system
US4150939A (en) * 1977-08-22 1979-04-24 Reliance Instrument Manufacturing Corp. Differential controller for positioning combustion system
US4249886A (en) * 1979-05-22 1981-02-10 Westinghouse Electric Corp. Combustion control system
US4309168A (en) * 1980-03-06 1982-01-05 Barber-Greene Company System for combining multiple fuels to produce controllable gas temperatures in asphalt drum mixers
US4362499A (en) * 1980-12-29 1982-12-07 Fisher Controls Company, Inc. Combustion control system and method
US4369026A (en) * 1980-02-21 1983-01-18 Phillips Petroleum Company Control of the fuel/oxygen ratio for a combustion process
US4421473A (en) * 1981-07-27 1983-12-20 Coen Company, Inc. Apparatus for operating a burner at an optimal level
US4423487A (en) * 1979-11-23 1983-12-27 Neotronics Limited Apparatus for measuring the efficiency of combustion appliances
US4444551A (en) * 1981-08-27 1984-04-24 Emerson Electric Co. Direct ignition gas burner control system
US4486166A (en) * 1982-08-12 1984-12-04 Westinghouse Electric Corp. Jackshaft controlled boiler combustion control system
US4498428A (en) * 1984-04-10 1985-02-12 Phillips Petroleum Company Combustion control for a boiler
US4576570A (en) * 1984-06-08 1986-03-18 Republic Steel Corporation Automatic combustion control apparatus and method
US4585161A (en) * 1984-04-27 1986-04-29 Tokyo Gas Company Ltd. Air fuel ratio control system for furnace
US4645450A (en) * 1984-08-29 1987-02-24 Control Techtronics, Inc. System and process for controlling the flow of air and fuel to a burner
US4649767A (en) * 1985-10-02 1987-03-17 Cleveland Controls, Incorporated Trim linkage
US4676734A (en) * 1986-05-05 1987-06-30 Foley Patrick J Means and method of optimizing efficiency of furnaces, boilers, combustion ovens and stoves, and the like
US5106294A (en) * 1988-04-16 1992-04-21 Conel Ag Method and arrangement for reducing the effect of disturbances on the combustion of a fan burner system
US5239980A (en) * 1992-05-19 1993-08-31 Hilt Fay E J Forced air furnace control system and method of operation
US5401162A (en) * 1989-10-30 1995-03-28 Honeywell Inc. Microbridge-based combustion control
US5452687A (en) * 1994-05-23 1995-09-26 Century Controls, Inc. Microprocessor-based boiler sequencer
US5605452A (en) * 1995-06-06 1997-02-25 North American Manufacturing Company Method and apparatus for controlling staged combustion systems
US5634786A (en) * 1994-11-30 1997-06-03 North American Manufacturing Company Integrated fuel/air ratio control system
US5997280A (en) * 1997-11-07 1999-12-07 Maxon Corporation Intelligent burner control system
US6059195A (en) * 1998-01-23 2000-05-09 Tridelta Industries, Inc. Integrated appliance control system
US6377426B2 (en) * 1998-12-21 2002-04-23 American Standard International Inc. Gas furnace with variable speed draft inducer
US20040209209A1 (en) * 2002-11-04 2004-10-21 Chodacki Thomas A. System, apparatus and method for controlling ignition including re-ignition of gas and gas fired appliances using same
US6984122B2 (en) * 2003-04-25 2006-01-10 Alzeta Corporation Combustion control with temperature compensation
US20080091309A1 (en) * 1998-01-15 2008-04-17 Walker Richard C Electrically controlled automated devices to operate, slow, guide, stop and secure, equipment and machinery for the purpose of controlling their unsafe, unattended, unauthorized, unlawful hazardous and/or legal use, with remote control and accountability worldwide
US7435080B2 (en) * 2004-01-12 2008-10-14 Combustion Science & Engineering, Inc. System and method for flame stabilization and control
US7517215B1 (en) * 2004-07-09 2009-04-14 Erc Incorporated Method for distributed ignition of fuels by light sources
US7671305B2 (en) * 2002-03-04 2010-03-02 Saint-Gobain Ceramics & Plastics, Inc. Systems for regulating voltage to an electrical resistance igniter

Patent Citations (43)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3284615A (en) * 1956-09-24 1966-11-08 Burroughs Corp Digital control process and system
US3236449A (en) * 1958-03-12 1966-02-22 Sulzer Ag Method and apparatus for controlling fuel and air supplied to a combustion chamber
US3049300A (en) * 1960-04-07 1962-08-14 Bailey Meter Co Combustion control for a furnace fired with fuels having different oxygenexcess air characteristics
US3216661A (en) * 1961-10-10 1965-11-09 George K Mckenzie Combustion control apparatus
US3241597A (en) * 1962-12-04 1966-03-22 Sulzer Ag Method of firing with fluid fuels
US3616997A (en) * 1968-05-20 1971-11-02 Kockums Mekaniska Verkstads Ab Combustion regulator
US3549089A (en) * 1968-07-26 1970-12-22 Hays Corp Method and means for trimming position control members
US3602487A (en) * 1969-11-10 1971-08-31 Jones & Laughlin Steel Corp Blast furnace stove control
US3734675A (en) * 1971-07-13 1973-05-22 Phillips Petroleum Co Burner controlling apparatus and method
US3908897A (en) * 1972-12-21 1975-09-30 Shell Oil Co Off-line integration of bridge and boiler controls
US4138725A (en) * 1976-07-30 1979-02-06 Kawasaki Jukogyo Kabushiki Kaisha Automatic fuel combustion control method and system
US4097218A (en) * 1976-11-09 1978-06-27 Mobil Oil Corporation Means and method for controlling excess air inflow
US4133629A (en) * 1977-08-02 1979-01-09 Phillips Petroleum Company Combustion system control
US4150939A (en) * 1977-08-22 1979-04-24 Reliance Instrument Manufacturing Corp. Differential controller for positioning combustion system
US4249886A (en) * 1979-05-22 1981-02-10 Westinghouse Electric Corp. Combustion control system
US4423487A (en) * 1979-11-23 1983-12-27 Neotronics Limited Apparatus for measuring the efficiency of combustion appliances
US4369026A (en) * 1980-02-21 1983-01-18 Phillips Petroleum Company Control of the fuel/oxygen ratio for a combustion process
US4309168A (en) * 1980-03-06 1982-01-05 Barber-Greene Company System for combining multiple fuels to produce controllable gas temperatures in asphalt drum mixers
US4362499A (en) * 1980-12-29 1982-12-07 Fisher Controls Company, Inc. Combustion control system and method
US4421473A (en) * 1981-07-27 1983-12-20 Coen Company, Inc. Apparatus for operating a burner at an optimal level
US4444551A (en) * 1981-08-27 1984-04-24 Emerson Electric Co. Direct ignition gas burner control system
US4486166A (en) * 1982-08-12 1984-12-04 Westinghouse Electric Corp. Jackshaft controlled boiler combustion control system
US4498428A (en) * 1984-04-10 1985-02-12 Phillips Petroleum Company Combustion control for a boiler
US4585161A (en) * 1984-04-27 1986-04-29 Tokyo Gas Company Ltd. Air fuel ratio control system for furnace
US4576570A (en) * 1984-06-08 1986-03-18 Republic Steel Corporation Automatic combustion control apparatus and method
US4645450A (en) * 1984-08-29 1987-02-24 Control Techtronics, Inc. System and process for controlling the flow of air and fuel to a burner
US4649767A (en) * 1985-10-02 1987-03-17 Cleveland Controls, Incorporated Trim linkage
US4676734A (en) * 1986-05-05 1987-06-30 Foley Patrick J Means and method of optimizing efficiency of furnaces, boilers, combustion ovens and stoves, and the like
US5106294A (en) * 1988-04-16 1992-04-21 Conel Ag Method and arrangement for reducing the effect of disturbances on the combustion of a fan burner system
US5401162A (en) * 1989-10-30 1995-03-28 Honeywell Inc. Microbridge-based combustion control
US5239980A (en) * 1992-05-19 1993-08-31 Hilt Fay E J Forced air furnace control system and method of operation
US5452687A (en) * 1994-05-23 1995-09-26 Century Controls, Inc. Microprocessor-based boiler sequencer
US5634786A (en) * 1994-11-30 1997-06-03 North American Manufacturing Company Integrated fuel/air ratio control system
US5605452A (en) * 1995-06-06 1997-02-25 North American Manufacturing Company Method and apparatus for controlling staged combustion systems
US5997280A (en) * 1997-11-07 1999-12-07 Maxon Corporation Intelligent burner control system
US20080091309A1 (en) * 1998-01-15 2008-04-17 Walker Richard C Electrically controlled automated devices to operate, slow, guide, stop and secure, equipment and machinery for the purpose of controlling their unsafe, unattended, unauthorized, unlawful hazardous and/or legal use, with remote control and accountability worldwide
US6059195A (en) * 1998-01-23 2000-05-09 Tridelta Industries, Inc. Integrated appliance control system
US6377426B2 (en) * 1998-12-21 2002-04-23 American Standard International Inc. Gas furnace with variable speed draft inducer
US7671305B2 (en) * 2002-03-04 2010-03-02 Saint-Gobain Ceramics & Plastics, Inc. Systems for regulating voltage to an electrical resistance igniter
US20040209209A1 (en) * 2002-11-04 2004-10-21 Chodacki Thomas A. System, apparatus and method for controlling ignition including re-ignition of gas and gas fired appliances using same
US6984122B2 (en) * 2003-04-25 2006-01-10 Alzeta Corporation Combustion control with temperature compensation
US7435080B2 (en) * 2004-01-12 2008-10-14 Combustion Science & Engineering, Inc. System and method for flame stabilization and control
US7517215B1 (en) * 2004-07-09 2009-04-14 Erc Incorporated Method for distributed ignition of fuels by light sources

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9353945B2 (en) * 2008-09-11 2016-05-31 Jupiter Oxygen Corporation Oxy-fuel combustion system with closed loop flame temperature control
US20100062381A1 (en) * 2008-09-11 2010-03-11 Gross Dietrich M Oxy-fuel combustion system with closed loop flame temperature control
US8439667B2 (en) 2008-11-25 2013-05-14 Utc Fire & Security Corporation Oxygen trim controller tuning during combustion system commissioning
US20110223548A1 (en) * 2008-11-25 2011-09-15 Utc Fire & Security Corporation Oxygen trim controller tuning during combustion system commissioning
US9028245B2 (en) * 2008-11-25 2015-05-12 Utc Fire & Security Corporation Automated setup process for metered combustion control systems
US20110212404A1 (en) * 2008-11-25 2011-09-01 Utc Fire & Security Corporation Automated setup process for metered combustion control systems
US10260428B2 (en) 2009-05-08 2019-04-16 Gas Turbine Efficiency Sweden Ab Automated tuning of gas turbine combustion systems
US9328670B2 (en) 2009-05-08 2016-05-03 Gas Turbine Efficiency Sweden Ab Automated tuning of gas turbine combustion systems
US8437941B2 (en) 2009-05-08 2013-05-07 Gas Turbine Efficiency Sweden Ab Automated tuning of gas turbine combustion systems
US9267443B2 (en) 2009-05-08 2016-02-23 Gas Turbine Efficiency Sweden Ab Automated tuning of gas turbine combustion systems
US9354618B2 (en) 2009-05-08 2016-05-31 Gas Turbine Efficiency Sweden Ab Automated tuning of multiple fuel gas turbine combustion systems
US9671797B2 (en) 2009-05-08 2017-06-06 Gas Turbine Efficiency Sweden Ab Optimization of gas turbine combustion systems low load performance on simple cycle and heat recovery steam generator applications
US20110244407A1 (en) * 2010-03-30 2011-10-06 Yamatake Corporation Combustion controlling device
US9557059B2 (en) 2011-12-15 2017-01-31 Honeywell International Inc Gas valve with communication link
US20150045971A1 (en) * 2011-12-15 2015-02-12 Honeywell International Inc. Valve controller configured to estimate fuel comsumption
US9835265B2 (en) 2011-12-15 2017-12-05 Honeywell International Inc. Valve with actuator diagnostics
US9846440B2 (en) * 2011-12-15 2017-12-19 Honeywell International Inc. Valve controller configured to estimate fuel comsumption
US9851103B2 (en) 2011-12-15 2017-12-26 Honeywell International Inc. Gas valve with overpressure diagnostics
US9995486B2 (en) 2011-12-15 2018-06-12 Honeywell International Inc. Gas valve with high/low gas pressure detection
US9657946B2 (en) 2012-09-15 2017-05-23 Honeywell International Inc. Burner control system
US10422531B2 (en) 2012-09-15 2019-09-24 Honeywell International Inc. System and approach for controlling a combustion chamber
US10203049B2 (en) 2014-09-17 2019-02-12 Honeywell International Inc. Gas valve with electronic health monitoring
US10313767B2 (en) 2016-04-07 2019-06-04 Honeywell International Inc. Fuel submetering using firing rate signals

Similar Documents

Publication Publication Date Title
US3422800A (en) Combined gas turbine and waste heat boiler control system
US4577270A (en) Plant control method
US7593803B2 (en) Method for controlling fuel splits to gas turbine combustor
EP2372127A1 (en) Control device for waste heat recovery system
US20040255595A1 (en) Method and system for controlling gas turbine by adjusting target exhaust temperature
US5841652A (en) Adaptive-predictive control and optimization system
US8186313B2 (en) Control system for modulating water heater
JP4564376B2 (en) LNG power generation plant and its operation method
EP0189614B1 (en) Apparatus and method for adjusting a central heating installation
US4139887A (en) Dynamic compensation for multi-loop controls
EP0098037A2 (en) Electric power generation systems and methods of operating such systems
JP4191563B2 (en) Compressor control method
US8303297B2 (en) Method and apparatus for controlling combustion in a burner
US20040188532A1 (en) Air control system
US4866940A (en) Computer aided tuning of turbine controls
EP1676991A3 (en) Plant temperature control system
US4064699A (en) Boiler control providing improved operation with fuels having variable heating values
US7565792B2 (en) Fuel gas heating control equipment and gas turbine power generation facility provided with the fuel gas heating control equipment
JP4234738B2 (en) Linked hot water system
US7066155B2 (en) Method and system for the control of fumigation
CN101861552A (en) Extremum seeking control with actuator saturation control
JP4331406B2 (en) Burner operation method and burner apparatus
KR890005133B1 (en) Process heater control
Anderson Instrumentation for Process Measurement and Control, Third Editon
US4498863A (en) Feed forward combustion control system

Legal Events

Date Code Title Description
AS Assignment

Owner name: PREFERRED UTILITIES MANUFACTURING CORPORATION, CON

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LAVELLE, PETER;REEL/FRAME:020248/0124

Effective date: 20071130

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION