Burner Control

Abstract

A reactant supply and control system supplies a regenerative burner assembly with streams of pilot fuel and pilot air. The system can maintain a pilot flame throughout regenerative cycles in which a main flame is turned on and off, and supplies either or both of the pilot streams with an increased flow rate for shifting from a regenerative exhaust condition to a regenerative firing condition.

1 . An apparatus comprising:
 a regenerative bed;   a burner assembly in air flow communication with the regenerative bed; and   a reactant supply and control system configured a) to shift from a regenerative exhaust condition in which the system does not supply the burner assembly with a main fuel stream to a regenerative firing condition in which the system supplies the burner assembly with a main fuel stream, b) to supply the burner assembly with a flow rate of pilot fuel and a flow rate of pilot air in the regenerative exhaust condition, and c) to supply the burner assembly with a different flow rate of pilot fuels or a different flow rate of pilot air, or different flow rates of both pilot fuel and pilot air, in the regenerative firing condition.   
     
     
         2 . An apparatus as defined in  claim 1  wherein each of the different flow rates in the regenerative firing condition is greater than the corresponding flow rate in the regenerative exhaust condition. 
     
     
         3 . An apparatus as defined in  claim 1  wherein the reactant supply and control system is configured to shift back and forth between the flow rates throughout consecutive cycles of shifting back and forth between the regenerative exhaust condition and the regenerative firing condition. 
     
     
         4 . An apparatus as defined in  claim 3  wherein the reactant supply and control system is configured to supply the pilot burner with pilot fuel and pilot air to form a pilot flame continuously throughout the consecutive cycles of shifting back and forth between the regenerative exhaust condition and the regenerative firing condition. 
     
     
         5 . An apparatus comprising:
 a regenerative bed;   a pilot burner configured receive streams of pilot fuel and pilot air to form a pilot flame;   a main burner configured to receive streams of main fuel and primary air to be ignited by the pilot flame and thereby to form a main flame;   a first supervisory device configured to sense the pilot flame;   a second supervisory device configured to sense the main flame but not to sense the pilot flame; and   a reactant supply and control system configured a) to alternate between a regenerative exhaust condition and a regenerative firing condition, b) to identify a first condition in which the first supervisory device senses the pilot flame and the second supervisory device does not sense a main flame, c) to identify a second condition in which the second supervisory device senses a main flame, d) to supply the pilot burner with a flow rate of pilot fuel and a flow rate of pilot air in the first condition, and e) to supply the pilot burner with a different flow rate of pilot fuel, or a different flow rate of pilot air, or different flow rates of both pilot fuel and pilot air, in the second condition.   
     
     
         6 . An apparatus as defined in  claim 5  wherein each of the different flow rates is an increased flow rate. 
     
     
         7 . An apparatus as defined in  claim 5  wherein the first condition is a regenerative exhaust condition and the second condition is a regenerative firing condition. 
     
     
         8 . An apparatus as defined in  claim 7  wherein the reactant supply and control system is configured to shift back and forth between the flow rates throughout consecutive cycles of shifting back and forth between the regenerative exhaust condition and the regenerative firing condition. 
     
     
         9 . An apparatus as defined in  claim 8  wherein the reactant supply and control system is configured to supply the pilot burner with pilot fuel and pilot air to form a pilot flame continuously throughout the consecutive cycles of shifting back and forth between the regenerative exhaust condition and the regenerative firing condition. 
     
     
         10 . An apparatus comprising:
 a pilot burner configured to receive fuel and air flows to form a pilot flame;   a reactant supply and control system configured to supply the pilot burner with a first combination of fuel and air flows, and a second combination of fuel and air flows distinct from the first combination by virtue of differing amounts of either or both of fuel flow and air flow, and capable of switching between the two combinations;   a main burner configured to receive streams of main fuel and primary air to be ignited by the pilot flame and thereby to form a main flame;   a first supervisory device configured to sense the pilot flame under either combination of fuel and air flows, regardless of whether or not the main fuel stream is being delivered to the main burner; and   a secondary supervisory device configured to sense the main flame when the main fuel stream is present, but which will not sense the pilot flame when the main fuel stream is absent and the pilot burner is being supplied with the first combination of fuel and air flows;   wherein the reactant supply and control system is further configured a) to identify a first condition in which the first supervisory device senses the pilot flame, the second supervisory device does not sense the main flame, and there is no main fuel stream supplied to the main burner, b) to identify a second condition in which the second supervisory device senses the main flame, c) to supply the pilot burner with the first combination of fuel and air flows in the first condition, and d) to supply the pilot burner with the second combination of fuel and air flows in the second condition.   
     
     
         11 . An apparatus as defined in  claim 10  wherein the reactant supply and control system is configured to shift back and forth between the first and second combinations throughout consecutive cycles of shifting back and forth between the first and second conditions. 
     
     
         12 . An apparatus as defined in  claim 11  wherein the reactant supply and control system is configured to supply the pilot burner with fuel and air flows to form a pilot flame continuously throughout the consecutive cycles of shifting back and forth between the first and second conditions. 
     
     
         13 . An apparatus as defined in  claim 10  further comprising a regenerative bed in air flow communication with the reactant supply and control system, and wherein the first condition is a regenerative exhaust condition and the second condition is a regenerative firing condition. 
     
     
         14 . A method comprising:
 shifting a reactant supply and control system from a regenerative exhaust condition in which the system does not supply a burner assembly with a main fuel stream to a regenerative firing condition in which the system supplies the burner assembly with a main fuel stream and with preheated air from a regenerative bed;   operating the reactant supply and control system to supply the burner assembly with a flow rate of pilot fuel and a flow rate of pilot air in the regenerative exhaust condition; and   operating the reactant supply and control system to supply the burner assembly with a different flow rate of pilot fuel, or a different flow rate of pilot air, or different flow rates of both pilot fuel and pilot air, in the regenerative firing condition.   
     
     
         15 . A method as defined in  claim 14  wherein each of the different flow rates in the regenerative firing condition is greater than the corresponding flow rate in the regenerative exhaust condition. 
     
     
         16 . A method as defined in  claim 14  wherein the reactant supply and control system is shifted back and forth between the flow rates throughout consecutive cycles of shifting back and forth between the regenerative exhaust condition and the regenerative firing condition. 
     
     
         17 . A method as defined in  claim 16  wherein the reactant supply and control system is operated to supply the burner assembly with pilot fuel and pilot air continuously throughout the consecutive cycles of shifting back and forth between the regenerative exhaust condition and the regenerative firing condition. 
     
     
         18 . A method of operating an apparatus comprising a pilot burner configured to receive streams of pilot fuel and pilot air to form a pilot flame, and a main burner configured to receive streams of main fuel and primary air to be ignited by the pilot flame and thereby to form a main flame, the method comprising:
 operating a first flame sensor that is configured to sense the pilot flame;   operating a second flame sensor that is configured to sense the main flame but not to sense the pilot flame;   identifying a first condition in which the first flame sensor senses the pilot flame but the second flame sensor does not sense the main flame;   identifying a second condition in which the second flame sensor senses the main flame;   supplying the pilot burner with a flow rate of pilot fuel and a flow rate of pilot air in the first condition; and   supplying the pilot burner with a different flow rate of pilot fuel, or a different flow rate of pilot air, or different flow rates of both pilot fuel and pilot air, in the second condition.   
     
     
         19 . A method as defined in  claim 18  wherein each of the different flow rates is an increased flow rate. 
     
     
         20 . A method as defined in  claim 18  wherein the flow rates are shifted back and forth throughout consecutive cycles of shifting back and forth between the first condition and the second condition. 
     
     
         21 . A method as defined in  claim 18  wherein the pilot flame is formed at the pilot burner continuously throughout the consecutive cycles of shifting back and forth between the first condition and the second condition. 
     
     
         22 . A method as defined in  claim 18  wherein the first condition is a regenerative exhaust condition and the second condition is a regenerative firing condition.