Furnace combustion cross limit control with real-time diagnostic features

Abstract

The present invention monitors and controls various operation/process variables of a furnace or boiler, which may be, for example, fuel flow, fuel pressure, air flow, box pressure, feed outlet temperature, etc., and reacts to certain operation issues. A method and system is provided for monitoring and controlling the operation of a furnace in real-time which may prevent unnecessary tripping of the furnace.

We claim: 
     
         1 . A method for monitoring and controlling the operation of a furnace in real-time, comprising:
 (a) obtaining a measurement of a controlled process variable (PV) from a measuring device that senses the PV in a controlled process;   (b) obtaining an output reading (OP) from a controller that is in an auto-mode and is continuously controlling the controlled process by maintaining the PV within a desired range;   (c) determining whether there has been a change (dPV) in the PV relative to a previously obtained controlled process variable (PV p ) obtained from the measuring device; and   (d) determining whether or not dPV was initiated by the controller.   
     
     
         2 . The method as claimed in  claim 1 , further comprising:
 (e) switching the controller into a manual mode if it is determined that dPV was not initiated by the controller   
     
     
         3 . The method as claimed in  claim 2 , further comprising:
 (f) sending a signal to an operator alerting the operator that the controller has been switched to the manual mode.   
     
     
         4 . The method as claimed in  claim 1 , wherein the controlled process variable (PV) is selected from the group consisting of box pressure, fuel gas pressure, O 2  concentration, valve stiction, air flow transmission, and fuel gas transmission. 
     
     
         5 . A method for monitoring and controlling the operation of a furnace in real-time, comprising:
 (a) obtaining a measurement of a controlled process variable (PV) from a measuring device that senses the PV in a controlled process;   (b) obtaining an output reading (OP) from a controller that is in an auto-mode and is continuously controlling the controlled process by maintaining the PV within a desired range;   (c) determining whether there has been a change (dPV) in the PV relative to a previously obtained controlled process variable (PV p ) obtained from the measuring device;   (d) determining whether there has been a change (dOP) in the OP relative to a previously obtained output reading (OP p ) obtained from the controller; and   (e) determining whether dPV is less than or greater than a predefined maximum controlled process variable (PV max ) and whether the dOP is less than or greater than a predetermined minimum output reading (OP min ) in order to determine whether a change in the process was initiated by the controller.   
     
     
         6 . The method as claimed in  claim 5 , further comprising:
 (f) switching the controller from the auto-mode into a manual mode if it is determined that the change in the process was not initiated by the controller   
     
     
         7 . The method as claimed in  claim 6 , further comprising:
 (g) sending a signal to an operator alerting the operator that the controller has been switched to the manual mode.   
     
     
         8 . The method as claimed in  claim 5 , wherein the controlled process variable (PV) is selected from the group consisting of box pressure, fuel gas pressure, O 2  concentration, valve stiction, air flow transmission, and fuel gas transmission.