Method and apparatus for enhancing flame radiation in a coal-burner retrofit

Abstract

An apparatus for retrofitting a coal-fueled burner of, e.g., a furnace, with a gas-fueled burner system for enhancing flame radiation of a gas flame. The gas-fueled burner system includes a flame charging system and an electrically isolated electrode. A time-varying voltage is applied to the flame charging system and the flame charging system imparts a corresponding time-varying charge onto the flame. The flame responds to the time-varying charge by increasing its luminosity and emissivity.

What is claimed is: 
     
         1 . A furnace, comprising:
 a furnace wall formed about at least a radiant heating volume and having a plurality of steam tubes disposed within the radiant heating volume; and   a burner system disposed at the furnace wall and including:
 a gas burner disposed through an opening in the furnace wall and configured to hold a gas flame in the radiant heating volume, 
 a gas and combustion air delivery device configured, respectively, to output a gas fuel and combustion air to the gas burner to support the gas flame, 
 a flame charging system configured to impart a time-varying electrical charge onto the gas flame, and 
 at least one electrode operatively coupled to the gas burner and disposed proximate the gas flame, the at least one electrode being disposed to apply an electric field to or proximate to the gas flame. 
   
     
     
         2 . The furnace of  claim 1 , wherein the burner system further comprises:
 a voltage source configured to provide a time-varying voltage to the flame charging system; and   a control interface operably connected to the voltage source and configured to control at least one of a level, phase, duty cycle, and wave shape of the time-varying voltage.   
     
     
         3 . The furnace of  claim 1 , wherein the flame charging system of the burner system includes an energization electrode disposed to have at least intermittent contact with the gas flame and configured to receive the time-varying voltage. 
     
     
         4 . The furnace of  claim 3 , wherein the time-varying voltage is selected to cause the energization electrode of the flame charging system to impart the corresponding time-varying electrical charge onto the gas flame. 
     
     
         5 . The furnace of  claim 1 , wherein the flame charging system further comprises a charge-ejecting electrode disposed proximate the gas flame; and
 wherein the charge-ejecting electrode is configured to receive a time-varying electrical voltage and to eject a corresponding time-varying electrical charge toward the gas flame.   
     
     
         6 . The furnace of  claim 5 , wherein the charge-ejecting electrode includes a corona electrode. 
     
     
         7 . The furnace of  claim 1  wherein the flame charging system includes an ionizer configured to receive a time-varying voltage and to provide a fluid medium carrying corresponding time-varying electrical charges to or in proximity to the flame. 
     
     
         8 . The furnace of  claim 1 , wherein the radiant heating volume is configured for receipt of heat from a coal burner, and wherein the burner system is a replacement burner system that replaces the coal burner, the flame charging system configuration to impart the time-varying electrical charge onto the gas flame is to increase emissivity of the gas flame. 
     
     
         9 . The furnace of  claim 8 , wherein the radiant heating volume is configured for receipt of heat from a coal burner, and wherein the burner system is a replacement burner system that replaces the coal burner, the flame charging system configuration to impart a time-varying reactant ratio into the gas flame is to increase emissivity of the gas flame. 
     
     
         10 . A coal-to-gas burner retrofit kit, comprising:
 a gas burner system sized to replace a coal burner in a furnace, the gas burner system including a fuel supply and a combustion air supply respectively configured to convey a gas fuel and combustion air, and a gas burner configured to hold a gas flame resulting from combustion of the gas fuel and combustion air received from the fuel supply and combustion air supply;   at least one electrode operatively coupled to the gas burner and placed for impingement with the gas flame, the at least one electrode being disposed proximate a location for the gas flame and arranged to apply a time-varying high voltage to the gas flame;   a voltage source having circuitry configured to control supply of the high voltage to the at least one electrode; and   an electrically isolated electrode configured to interact with the time-varying high voltage to increase flame luminance.   
     
     
         11 . The coal-to-gas burner retrofit kit of  claim 10 , wherein the time-varying high voltage on the at least one electrode is selected to interact with the electrically isolated electrode to cause a time-varying position of the gas flame. 
     
     
         12 . The coal-to-gas burner retrofit kit of  claim 11 , wherein the time varying-position of the gas flame is selected to cause a time-varying reactant mixture. 
     
     
         13 . The coal-to-gas burner retrofit kit of  claim 10 , wherein the gas burner is sized to replace the coal burner in the furnace without modification of an opening of the furnace that receives the gas burner. 
     
     
         14 . The coal-to-gas burner retrofit kit of  claim 10 , further comprising one or more attachment mechanisms affixed to the gas burner system, the attachment mechanisms having attachment features that secure at least a portion of the gas burner system to the furnace when the gas burner system is installed to the furnace. 
     
     
         15 . The coal-to-gas burner retrofit kit of  claim 14 , wherein the attachment mechanisms are placed in correspondence with existing attachment features of the furnace. 
     
     
         16 . The coal-to-gas burner retrofit kit of  claim 10 , further comprising refractory material configured to be disposed along a portion of the gas burner that is outside the furnace when the gas burner system is installed to the furnace. 
     
     
         17 . A method for retrofitting a furnace, the method comprising:
 removing, from the furnace, an existing coal burner system, the existing coal burner system having a coal burner disposed at a burner opening of the furnace, a coal supply, and a combustion air supply;   providing a replacement burner system for radiating energy from a gas flame, the replacement burner system including:
 a gas fuel source disposed to provide gaseous fuel via a fuel nozzle to the gas flame, 
 a combustion air source disposed to provide combustion air to the gas flame, 
 a gas burner configured to hold the gas flame produced from the gaseous fuel and the combustion air, 
 a flame charging system configured to receive a time-varying voltage and to impart a corresponding time-varying electrical charge to the gas flame, and 
 an electrically isolated conductor disposed proximate the gas burner; and 
   securing the replacement burner system proximate the furnace, the gas burner disposed at the burner opening.   
     
     
         18 . The method for retrofitting a furnace of  claim 17 , wherein the replacement gas burner system further comprises:
 a voltage source configured to provide the time-varying voltage to the flame charging system; and   a control interface operably connected to the voltage source and configured to control at least one of a voltage level, phase, duty cycle, and wave shape of the time-varying voltage.   
     
     
         19 . The method for retrofitting a furnace of  claim 17 , wherein the flame charging system of the replacement gas burner system further comprises an energization electrode disposed to have at least intermittent contact with the gas flame and configured to receive the time-varying voltage. 
     
     
         20 . The method for retrofitting a furnace of  claim 19 , wherein the time-varying charge is selected to cause the energization electrode to impart the corresponding time-varying electrical charge onto the gas flame. 
     
     
         21 . The method for retrofitting a furnace of  claim 17 , wherein the replacement gas burner system further comprises a charge-ejecting electrode disposed proximate the flame; and
 wherein the charge-ejecting electrode is configured to receive the time-varying electrical voltage and to eject a corresponding time-varying electrical charge toward the flame.   
     
     
         22 . The method for retrofitting a furnace of  claim 17 , wherein the replacement gas burner system further includes attachment features configured to attach the existing coal burner system to the furnace, the securing of the replacement gas burner system including attaching the replacement gas burner system to the furnace via the attachment features. 
     
     
         23 . The method for retrofitting a furnace of  claim 17 , wherein the replacement gas burner system further includes refractory material, the method further comprising installing the refractory material along a portion of the gas burner that is outside the furnace.